Document and Entity Information - USD ($) $ in Millions	12 Months Ended
Document and Entity Information - USD ($) $ in Millions	Dec. 31, 2020	Feb. 23, 2021	Jun. 30, 2020
Cover [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Trading Symbol	CYTK
Entity Registrant Name	CYTOKINETICS, INCORPORATED
Entity Central Index Key	0001061983
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		71,110,576
Entity Public Float			$ 1,413.0
Entity Interactive Data Current	Yes
Title of 12(b) Security	Common Stock, $0.001 par value
Security Exchange Name	NASDAQ
Entity File Number	000-50633
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	94-3291317
Entity Address, Address Line One	280 East Grand Avenue
Entity Address, City or Town	South San Francisco
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94080
City Area Code	650
Local Phone Number	624-3000
Document Annual Report	true
Document Transition Report	false
ICFR Auditor Attestation Flag	true
Documents Incorporated by Reference	Portions of the Registrant’s Proxy Statement for its 2021 Annual Meeting of Stockholders to be filed with the Securities and Exchange Commission, no later than 120 days after the end of the fiscal year, are incorporated by reference into Part III of this Annual Report on Form 10-K.

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 82,985	$ 36,433
Short-term investments	381,075	188,679
Accounts receivable	4,420	5,163
Prepaid expenses and other current assets	5,741	3,477
Total current assets	474,221	233,752
Long-term investments	36,954	42,650
Property and equipment, net	13,346	4,530
Operating lease right-of-use assets and other assets	9,282	8,882
Total assets	533,803	289,814
Current liabilities:
Accounts payable	8,050	8,160
Accrued liabilities	19,315	12,123
Short-term lease liability	2,785	4,616
Other current liabilities	1,049	1,124
Total current liabilities	31,199	26,023
Term loan, net	46,209	45,052
Convertible notes, net	89,504	84,205
Liability related to the sale of future royalties, net	166,068	143,276
Long-term deferred revenue	87,000	0
Long-term lease and other non-current liabilities	440	2,195
Total liabilities	420,420	300,751
Commitments and contingencies	0	0
Stockholders’ equity (deficit):
Preferred stock, $0.001 par value: Authorized: 10,000,000 shares; Issued and outstanding: none	0	0
Common stock, $0.001 par value: Authorized: 163,000,000 shares; Issued and outstanding: 71,015,183 shares at December 31, 2020 and 59,172,124 shares at December 31, 2019	70	59
Additional paid-in capital	1,105,470	853,341
Accumulated other comprehensive income	149	679
Accumulated deficit	(992,306)	(865,016)
Total stockholders’ equity (deficit)	113,383	(10,937)
Total liabilities and stockholders’ equity (deficit)	$ 533,803	$ 289,814

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2020	Dec. 31, 2019
Statement Of Financial Position [Abstract]
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	163,000,000	163,000,000
Common stock, shares issued	71,015,183	59,172,124
Common stock, shares outstanding	71,015,183	59,172,124

Consolidated Statements of Operations And Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenues:
Total revenues	$ 55,828	$ 26,868	$ 31,501
Operating expenses:
Research and development	96,951	86,125	89,135
General and administrative	52,820	39,610	31,282
Total operating expenses	149,771	125,735	120,417
Operating loss	(93,943)	(98,867)	(88,916)
Interest expense	(15,963)	(6,623)	(3,797)
Non-cash interest expense on liability related to sale of future royalties	(22,713)	(20,737)	(17,767)
Interest and other income, net	5,329	4,535	4,191
Net loss	$ (127,290)	$ (121,692)	$ (106,289)
Net loss per share — basic and diluted	$ (1.97)	$ (2.11)	$ (1.95)
Weighted-average number of shares used in computing net loss per share — basic and diluted	64,524	57,575	54,420
Other comprehensive loss:
Unrealized (losses) gains on available-for-sale securities, net	$ (530)	$ 179	$ 157
Comprehensive loss	(127,820)	(121,513)	(106,132)
Research and Development Revenues [Member]
Revenues:
Total revenues	16,527	26,868	26,368
License [Member]
Revenues:
Total revenues	36,501	0	5,133
Milestone Revenues [Member]
Revenues:
Total revenues	$ 2,800	$ 0	$ 0

Consolidated Statements of Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Total	Cumulative Effect, Period of Adoption, Adjustment [Member]	At-the-Market Offering [Member]	Underwritten Public Offering [Member]	Common Stock [Member]	Common Stock [Member] Cumulative Effect, Period of Adoption, Adjustment [Member]	Common Stock [Member] At-the-Market Offering [Member]	Common Stock [Member] Underwritten Public Offering [Member]	Additional Paid-in Capital [Member]	Additional Paid-in Capital [Member] Cumulative Effect, Period of Adoption, Adjustment [Member]	Additional Paid-in Capital [Member] At-the-Market Offering [Member]	Additional Paid-in Capital [Member] Underwritten Public Offering [Member]	Accumulated Other Comprehensive Income [Member]	Accumulated Other Comprehensive Income [Member] Cumulative Effect, Period of Adoption, Adjustment [Member]	Accumulated Other Comprehensive Income [Member] At-the-Market Offering [Member]	Accumulated Other Comprehensive Income [Member] Underwritten Public Offering [Member]	Accumulated Deficit [Member]	Accumulated Deficit [Member] Cumulative Effect, Period of Adoption, Adjustment [Member]	Accumulated Deficit [Member] At-the-Market Offering [Member]	Accumulated Deficit [Member] Underwritten Public Offering [Member]
Beginning Balance at Dec. 31, 2017	$ 109,842				$ 54				$ 755,526				$ 343				$ 646,081
Beginning Balance, shares at Dec. 31, 2017					53,960,832
Exercise of stock options, value	3,173				$ 1				3,172				0				0
Exercise of stock options, shares					422,819
Issuance under Employee Stock Purchase Plan, value	928				$ 0				928				0				0
Issuance under Employee Stock Purchase Plan, shares					144,822
Vesting of restricted stock units, net of taxes withheld, value	(866)				$ 0				(866)				0				0
Vesting of restricted stock units, net of taxes withheld, shares					189,433
Issuance of warrants	182				$ 0				182				0				0
Stock-based compensation	9,761				0				9,761				0				0
ASC 606 Adoption (ASC 606 [Member]) at Dec. 31, 2017		$ 9,046				$ 0				$ 0				$ 0				$ 9,046
Other comprehensive loss	157				0				0				157				0
Net loss	(106,289)				0				0				0				(106,289)
Ending Balance at Dec. 31, 2018	25,934				$ 55				768,703				500				(743,324)
Ending Balance, shares at Dec. 31, 2018					54,717,906
Exercise of stock options, value	1,017				$ 0				1,017				0				0
Exercise of stock options, shares					131,909
Issuance of common stock, net of issuance costs, value			$ 36,214				$ 4				$ 36,210				$ 0				$ 0
Issuance of common stock, net of issuance costs, shares							3,984,849
Issuance under Employee Stock Purchase Plan, value	1,108				$ 0				1,108				0				0
Issuance under Employee Stock Purchase Plan, shares					172,113
Vesting of restricted stock units, net of taxes withheld, value	(732)				$ 0				(732)				0				0
Vesting of restricted stock units, net of taxes withheld, shares					165,347
Issuance of warrants	185				$ 0				185				0				0
Equity component of convertible notes	49,477				0				49,477				0				0
Capped call options associated with convertible notes	(13,386)				0				(13,386)				0				0
Stock-based compensation	10,759				0				10,759				0				0
Other comprehensive loss	179				0				0				179				0
Net loss	(121,692)				0				0				0				(121,692)
Ending Balance at Dec. 31, 2019	(10,937)				$ 59				853,341				679				(865,016)
Ending Balance, shares at Dec. 31, 2019					59,172,124
Exercise of stock options, value	7,611				$ 1				7,610				0				0
Exercise of stock options, shares					943,505
Exercise of warrants, value	0				$ 0				0				0				0
Exercise of warrants, share					104,890
Claims settlement under Section 16(b)	2,151				$ 0				2,151				0				0
Issuance of common stock, net of issuance costs, value				$ 188,883				$ 8				$ 188,875				$ 0				$ 0
Issuance of common stock, net of issuance costs, shares								8,385,417
Issuance of common stock upon private placement, value	36,437				$ 2				36,435				0				0
Issuance of common stock upon private placement, shares					2,000,000
Issuance under Employee Stock Purchase Plan, value	1,509				$ 0				1,509				0				0
Issuance under Employee Stock Purchase Plan, shares					134,684
Vesting of restricted stock units, net of taxes withheld, value	(2,255)				$ 0				(2,255)				0				0
Vesting of restricted stock units, net of taxes withheld, shares					274,563
Issuance of warrants	184				$ 0				184				0				0
Stock-based compensation	17,620				0				17,620				0				0
ASC 606 Adoption (ASC 606 [Member]) at Dec. 31, 2019	(865,016)
Other comprehensive loss	(530)				0				0				(530)				0
Net loss	(127,290)				0				0				0				(127,290)
Ending Balance at Dec. 31, 2020	$ 113,383				$ 70				$ 1,105,470				$ 149				$ (992,306)
Ending Balance, shares at Dec. 31, 2020					71,015,183

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Cash flows from operating activities:
Net loss	$ (127,290)	$ (121,692)	$ (106,289)
Adjustments to reconcile net loss to net cash provided by (used in) operating activities:
Non-cash interest expense on liability related to sale of future royalties	22,792	20,737	17,767
Non-cash stock-based compensation expense	17,620	10,759	9,761
Depreciation and amortization of property and equipment	1,831	1,293	1,239
Gain on investment, net	(573)	0	0
Interest receivable and amortization on investments	(1,194)	(2,587)	(1,677)
Non-cash interest expense related to debt	6,640	919	920
Changes in operating assets and liabilities:
Accounts receivable	743	(2,932)	(1,119)
Contract assets	0	4,554	5,154
Prepaid and other current assets	(2,183)	(3,862)	1,817
Operating lease right-of-use assets and other assets	1,242	3,552	0
Accounts payable	(110)	4,396	(1,490)
Accrued and other liabilities	7,117	(2,168)	(2,063)
Contract liabilities	0	0	(18,750)
Operating lease liabilities	(4,692)	(3,876)	0
Deferred revenue	87,000	0	(6,485)
Net cash provided by (used in) operating activities	8,943	(90,907)	(101,215)
Cash flows from investing activities:
Purchases of investments	(435,825)	(277,883)	(240,224)
Maturities of investments	247,301	202,599	246,232
Sales of investments	3,061	3,196	0
Purchases of property and equipment	(11,052)	(2,619)	(889)
Sales of property and equipment	0	0	14
Net cash (used in) provided by investing activities	(196,515)	(74,707)	5,133
Cash flows from financing activities:
Proceeds from public offerings of common stock, net of discounts, commissions and offering cost	188,883	0	0
Proceeds from private placement, net	36,225	0	0
Proceeds from issuance under Employee Stock Purchase Plan	1,509	0	0
Proceeds from stock-based award activities, net	5,356	1,393	3,234
Claims settlement under Section 16(b)	2,151	0	0
Net proceeds from long-term debt, net of debt discount and issuance costs	0	1,710	9,898
Net proceeds from convertible notes, net of debt discount and issuance costs	0	133,860	0
Issuance of common stock under at-the-market offering, net of issuance costs	0	36,214	0
Purchase of capped call options associated with convertible notes	0	(13,386)	0
Net cash provided by financing activities	234,124	159,791	13,132
Net increase (decrease) in cash and cash equivalents	46,552	(5,823)	(82,950)
Cash and cash equivalents, beginning of period	36,433	42,256	125,206
Cash and cash equivalents, end of period	82,985	36,433	42,256
Supplemental cash flow disclosures:
Cash paid for interest	9,620	4,059	2,877
Right-of-use assets recognized in exchange for lease obligations	$ 1,106	$ 10,687	$ 0

Organization and Accounting Policies

12 Months Ended

Dec. 31, 2020

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Organization and Accounting Policies

Note 1 — Organization and Accounting Policies

Organization

Cytokinetics, Incorporated (the “Company”, “we” or “our”) was incorporated under the laws of the state of Delaware on August 5, 1997. We are a late-stage biopharmaceutical company focused on the discovery and development of novel small molecule therapeutics that modulate muscle function for the potential treatment of serious diseases and medical conditions.

Our financial statements contemplate the conduct of our operations in the normal course of business. We have incurred an accumulated deficit of $992.3 million since inception and there can be no assurance that we will attain profitability. We had a net loss of $127.3 million and net cash provided by operations of $8.9 million for the year ended December 31, 2020. Cash, cash equivalents and investments increased to $501.0 million as of December 31, 2020 from $267.8 million as of December 31, 2019. We anticipate that we will have operating losses and net cash outflows in future periods.

We are subject to risks common to late stage biopharmaceutical companies including, but not limited to, development of new drug candidates, dependence on key personnel, and the ability to obtain additional capital as needed to fund our future plans. Our liquidity will be impaired if sufficient additional capital is not available on terms acceptable to us. To date, we have funded operations primarily through sales of our common stock, contract payments under our collaboration agreements, sale of future royalties, debt financing arrangements, government grants and interest income. Until we achieve profitable operations, we intend to continue to fund operations through payments from strategic collaborations, additional sales of equity securities, grants and debt financings. We have never generated revenues from commercial sales of our drugs and may not have drugs to market for at least several years, if ever. Our success is dependent on our ability to enter into new strategic collaborations and/or raise additional capital and to successfully develop and market one or more of our drug candidates. As a result, we may choose to raise additional capital through equity or debt financings to continue to fund operations in the future. We cannot be certain that sufficient funds will be available from such a financing or through a collaborator when required or on satisfactory terms. Additionally, there can be no assurance that our drug candidates will be accepted in the marketplace or that any future products can be developed or manufactured at an acceptable cost. These factors could have a material adverse effect on our future financial results, financial position and cash flows.

Based on the current status of our research and development plans, we believe that our existing cash, cash equivalents and investments will be sufficient to fund our cash requirements for at least the next 12 months after the issuance of the consolidated financial statements. If, at any time, our prospects for financing our research and development programs decline, we may decide to reduce research and development expenses by delaying, discontinuing or reducing our funding of one or more of our research or development programs. Alternatively, we might raise funds through strategic collaborations, public or private financings or other arrangements. Such funding, if needed, may not be available on favorable terms, or at all. The financial statements do not include any adjustments that might result from the outcome of this uncertainty.

Use of Estimates

The preparation of financial statements in conformity with accounting principles generally accepted in the United States requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosures of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.

Basis of Presentation

The consolidated financial statements include the accounts of Cytokinetics, Incorporated and its wholly-owned subsidiary and have been prepared in accordance with U.S. generally accepted accounting principles (“US GAAP”). Intercompany transactions and balances have been eliminated in consolidation. Certain prior period amounts have been reclassified to conform the prior period presentation to the current year.

Concentration of Credit Risk and Other Risks and Uncertainties

Financial instruments that potentially subject us to concentrations of risk consist principally of cash and cash equivalents, investments, and accounts receivable.

Our cash, cash equivalents and investments are invested in deposits with two major financial institutions in the United States. Deposits in these banks may exceed the amount of insurance provided on such deposits.

Our exposure to credit risk associated with non-payment is limited to our strategic partners Amgen Inc. (“Amgen”), Astellas Pharma Inc. (“Astellas”) and Ji Xing Pharmaceuticals Limited (“Ji Xing”) and any material non-payment from our partners would result in a material breach of the agreements underlying our strategic partnerships.

Drug candidates we develop may require approvals or clearances from the U.S. Food and Drug Administration (“FDA”) or other regulatory agencies prior to commercial sales. There can be no assurance that our drug candidates will receive any of the required approvals or clearances. If we were to be denied approval, or clearance or any such approval or clearance was to be delayed, it would have a material adverse impact on us.

Cash and Cash Equivalents

We consider all highly liquid investments with a maturity of three months or less at the time of purchase to be cash equivalents.

Investments

Available-for-sale investments. Our investments consist of U.S. Treasury securities, agency bonds, commercial paper, corporate debt and money market funds. We designate all investments as available-for-sale and report them at fair value, based on quoted market prices, with unrealized gains and losses recorded in accumulated other comprehensive income and loss. The cost of securities sold is based on the specific-identification method. Investments with original maturities greater than three months and remaining maturities of one year or less are classified as short-term investments. Investments with remaining maturities greater than one year are classified as long-term investments. The amortized cost of debt securities in this category is adjusted for amortization of premiums and accretion of discounts to maturity. Such amortization is included in Interest and other income, net. Recognized gains and losses and declines in value judged to be other-than-temporary, if any, on available-for-sale securities are included in Interest and other income, net. Interest and dividends on securities classified as available-for-sale are included in Interest and other income, net.

All of our available-for-sale investments are subject to a periodic impairment review. If an impairment is the result of a credit loss, we recognize an allowance for credit losses (“ACL”). ACL’s reflect management’s current estimate of credit losses that are expected to occur over the remaining life of a financial asset. We recognize an impairment charge when a decline in the fair value of investments below the cost basis is judged to be other-than-temporary. Factors we consider in assessing whether an other-than-temporary impairment has occurred include: the nature of the investment; whether the decline in fair value is attributable to specific adverse conditions affecting the investment; the financial condition of the investee; the severity and the duration of the impairment; and whether we have the intent and ability to hold the investment to maturity. When we determine that an other-than-temporary impairment has occurred, the investment is written down to its market value at the end of the period in which it is determined that an other-than-temporary decline has occurred.

Property and Equipment, net

Property and equipment are stated at cost less accumulated depreciation and are depreciated on a straight-line basis over the estimated useful lives of the related assets, which are generally three years for computer equipment and software, five years for laboratory equipment and office equipment, and seven years for furniture and fixtures. Amortization of leasehold improvements is computed using the straight-line method over the shorter of the remaining lease term or the estimated useful life of the related assets, typically ranging from three to seven years. Upon sale or retirement of assets, the costs and related accumulated depreciation and amortization are removed from the balance sheet and the resulting gain or loss is reflected in operations.

Impairment of Long-lived Assets

We review long-lived assets, including property and equipment, for impairment whenever events or changes in business circumstances indicate that the carrying amount of the assets may not be fully recoverable. Impairment is measured as the amount by which the carrying amount of a long-lived asset exceeds its fair value. We would recognize an impairment loss when estimated undiscounted future cash flows expected to result from the use of the asset and its eventual disposition are materially less than its carrying amount.

Leases

We adopted Accounting Standards Update No. 2016-02, Leases (“Topic 842”) on January 1, 2019 using the modified retrospective approach. In adopting Topic 842, we recognized a right-of-use asset and a short-term and long-term lease liability on our consolidated balance sheets for our existing facilities leases with Britannia Pointe Grand Limited Partnership (the “Britannia Leases”). The right-of-use asset is based on the liability adjusted for any prepaid or deferred rent. We determined the lease term at the commencement date by considering whether renewal options and termination options are reasonably assured of exercise. In determining the present value of lease payments, we estimated our incremental borrowing rate based on information available when we adopted Topic 842. We base the Britannia Leases liability on the present value of remaining lease payments over the remaining terms of the Britannia Leases, using an estimated rate of interest that we would pay to borrow equivalent funds on a collateralized basis at the lease commencement date. We evaluated our other contracts and determined that, except for the Britannia Leases, none of our contracts contained a lease as defined in Topic 842.

We elected the package of practical expedients permitted under the transition guidance within Topic 842, which among other things, allowed us to carry forward the historical lease classification of those leases in place as of January 1, 2019. We also elected to exclude from our consolidated balance sheets recognition of leases having a term of 12 months or less (short-term leases) and elected to not separate lease components and non-lease components for Britannia Leases.

We recorded a lease liability of $10.7 million and a corresponding right-of-use asset of $9.6 million upon adoption of the new lease standard on January 1, 2019.

We recognize rent expense for operating leases on a straight-line basis over the lease term in operating expenses on the consolidated statements of operations.

Prior period amounts continue to be reported in accordance with our historic accounting under previous lease guidance, ASC 840, Leases (“Topic 840”).

Revenue Recognition

We recognize revenue when we transfer promised goods or services to customers in an amount that reflects the consideration for those goods or services. To recognize revenue from a contract with a customer, we:

(i)

identify our contracts with our customers;

(ii)

identify our distinct performance obligations in each contract;

(iii)

determine the transaction price of each contract;

(iv)

allocate the transaction price to the performance obligations; and

(v)

recognize revenue as we satisfy our performance obligations.

At contract inception, we assess the goods or services promised within each contract and assess whether each promised good or service is distinct and determine those that are performance obligations. We then recognize as revenue the amount of the transaction price that is allocated to the respective performance obligation when (or as) the performance obligation is satisfied.

Collaborative Arrangements

We enter into collaborative arrangements with partners that typically include payment to us for one of more of the following: (i) license fees; (ii) milestone payments related to the achievement of developmental, regulatory, or commercial goals; (iii) royalties on net sales of licensed products; and (iv) research and development cost reimbursements. Each of these payments results in collaboration or other revenues. Where a portion of non-refundable up-front fees or other payments received are allocated to continuing performance obligations under the terms of a collaborative arrangement, they are recorded as deferred revenue and recognized as revenue when (or as) the underlying performance obligation is satisfied.

As part of the accounting for these arrangements, we must develop estimates and assumptions that require judgment to determine the underlying stand-alone selling price for each performance obligation which determines how the transaction price is allocated among the performance obligations. The stand-alone selling price may include such items as, forecasted revenues, development timelines, reimbursement rates for personnel costs, discount rates and probabilities of technical and regulatory success, to determine the transaction price to allocate to each performance obligation.

For our collaboration agreements that include more than one performance obligation, such as a license combined with a commitment to perform research and development services, we make judgments to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress for purposes of recognizing revenue from non-refundable, up-front fees. We evaluate our progress each reporting period and, if necessary, adjust the measure of a performance obligation and related revenue recognition.

License Fees: If a license to our intellectual property is determined to be distinct from the other performance obligations identified in the arrangement, we recognize revenues from non-refundable, up-front fees allocated to the license when the license is transferred to the licensee and the licensee is able to use and benefit from the license. For licenses that are bundled with other promises, we utilize judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress for purposes of recognizing revenue from non-refundable, up-front license fees. We evaluate the measure of progress each reporting period and, if necessary, adjust the measure of performance and related revenue recognition.

Milestone Payments: We use judgment to determine whether a milestone is considered probable of being reached. Using the most likely amount method, we include the value of a milestone payment in the consideration for a contract at inception if we then conclude achieving the milestone is more likely than not. Otherwise, we exclude the value of a milestone payment from contract consideration at inception and recognize revenue for a milestone at a later date, when we judge that it is probable the milestone will be achieved. If we conclude it is probable that a significant revenue reversal would not occur, the associated milestone is included in the transaction price. We then allocate the transaction price to each performance obligation on a relative stand-alone selling price basis, for which we recognize revenue as or when the performance obligations under the contract are satisfied. At the end of each subsequent reporting period, we re-evaluate the probability of achievement of such milestones and any related constraint, and if necessary, adjust our estimate of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis, which would affect license, collaboration and other revenues and earnings in the period of adjustment.

Royalties: For contracts that include sales-based royalties, we recognize revenue at the later of (i) when the related sales occur, or (ii) when the performance obligation to which some or all of the royalty has been allocated has been satisfied. To date, we have not recognized any royalty revenues resulting from contracts.

Research and Development Cost Reimbursements: Our joint programs with Astellas under that certain License and Collaboration Agreement for Other Skeletal Sarcomere Activators, dated April 23, 2020, as amended (the “Astellas OSSA Agreement”), and with Amgen under that certain Collaboration and Option Agreement, dated December 29, 2006, as amended (the “Amgen Agreement”), include promises of research and development services. We have determined that these services collectively are distinct from the licenses provided to Astellas and Amgen under such agreements, and as such, these promises are accounted for as a separate performance obligation recorded over time. We recognize revenue for these services as the performance obligations are satisfied, which we estimate using internal research and development costs incurred.

Accrued Research and Development Expenditures

A substantial portion of our preclinical studies and all of our clinical trials have been performed by third-party contract research organizations (“CROs”) and other vendors and our accruals for expenses for preclinical studies and clinical trials may be significant. For preclinical studies, the significant factors used in estimating accruals include the percentage of work completed to date and contract milestones achieved. For clinical trial expenses, the significant factors used in estimating accruals include the number of patients enrolled, duration of enrollment, milestones achieved and percentage of work completed to date. We monitor patient enrollment levels and related activities to the extent practicable through internal reviews, correspondence and status meetings with CROs, and review of contractual terms. We depend on the timeliness and accuracy of data provided by our CROs and other vendors to accrue expenses. If we receive and rely on incomplete or inaccurate data, accruals and expenses may be too high or too low at a given point in time and corresponding adjustments to accruals and expenses would be made in future periods when the actual expense becomes known.

Liability Related to Sale of Future Royalties

We treat our liability to RPI Finance Trust (“RPI”) related to sale of future royalties under that certain Royalty Purchase Agreement, dated February 1, 2017 (the “RPI Royalty Purchase Agreement”) pursuant to which we sold a portion of our right to receive royalties from Amgen on potential net sales of omecamtiv mecarbil as a debt financing, to be amortized under the effective interest rate method over the life of the related royalty stream.

Our liability to RPI related to sale of future royalties under the RPI Royalty Purchase Agreement (the “RPI Liability”) and related amortization are based on our current estimates of future royalties expected to be paid over the life of the arrangement. Concurrently with our entry into the RPI Royalty Purchase Agreement, we entered into a common stock purchase agreement with RPI. We allocated the consideration and issuance costs on a relative fair value basis to the RPI Liability and the common stock.

The RPI Royalty Purchase Agreement further provides that in the event Amgen elects to terminate the Amgen Agreement, we are obliged to enter into an agreement with RPI to preserve RPI’s rights under the RPI Royalty Purchase Agreement, which includes the payment by Cytokinetics of 4.5% of its worldwide net sales of omecamtiv mecarbil and other compounds with the same mechanism of action as omecamtiv mecarbil that are subject to the Amgen Agreement (together the “Amgen Alliance Compounds”), subject to a potential increase of up to an additional 1% under certain circumstances (delay in US marketing approval). Our obligation to enter into a new agreement with RPI does not impact our accounting treatment of the RPI Liability or our estimates.

The RPI Liability will be recognized using significant unobservable inputs. These inputs are derived using internal management estimates developed based on third party data and reflect management’s judgements, current market conditions surrounding competing products, and forecasts. The significant unobservable inputs include the estimated patient population, estimated selling price, estimated peak sales and sales ramp, the expected term of the royalty stream, timing of the expected launch and its impact on the royalty rate. A significant change in unobservable inputs could result in a material increase or decrease to the effective interest rate of the RPI Liability.

We will periodically assess the amount and timing of expected royalty payments using a combination of internal projections and forecasts from external sources. To the extent our future estimates of future royalty payments are greater or less than previous estimates or the estimated timing of such payments is materially different than previous estimates, we will adjust the amortization of the RPI Liability related to sale of future royalties and prospectively recognize the related non-cash interest expense. We have updated the analysis to include the data released on October 8, 2020 relating to GALACTIC-HF. Our estimates regarding the amount and timing of future royalty payments have not changed as a result of Amgen’s election to terminate the Amgen Agreement or Servier’s election to terminate the sublicense agreement (the “Servier Agreement”) between Amgen and Les Laboratoires Servier and Institut de Recherches Internationales Servier (“Servier”) respectively.

We account for the RPI Liability, as a liability primarily because we have significant continuing involvement in generating the royalty stream. If and when omecamtiv mecarbil is commercialized and royalties become due, we will recognize the portion of royalties paid to RPI as a decrease to the RPI Liability and a corresponding reduction in cash.

Research and Development Expenditures

Research and development costs are charged to operations as incurred. Research and development expenses consist primarily of clinical manufacturing costs, preclinical study expenses, consulting and other third-party costs, employee compensation, supplies and materials, allocation of overhead and occupancy costs, facilities costs and depreciation of equipment.

Income Taxes

We account for income taxes under the asset and liability method. Under this method, deferred tax assets and liabilities are determined based on the difference between the financial statement and tax basis of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to affect taxable income. Valuation allowances are established when necessary to reduce deferred tax assets to the amounts expected to be realized.

We recognize uncertain tax positions taken or expected to be taken on a tax return. Tax positions are initially recognized when it is more likely than not that the position will be sustained upon examination by the tax authorities. Such tax positions are initially and subsequently measured as the largest amount of tax benefit that is more likely than not of being realized upon ultimate settlement with the tax authority assuming full knowledge of the position and relevant facts.

We recognize interest accrued related to unrecognized tax benefits and penalties as income tax expense.

In December 2019, the FASB issued ASU 2019-12, Simplifying the Accounting for Income Taxes (“ASU 2019-12”), as part of its Simplification Initiative to reduce the cost and complexity in accounting for income taxes. ASU 2019-12 removes certain exceptions related to the approach for intraperiod tax allocation, the methodology for calculating income taxes in an interim period and the recognition of deferred tax liabilities for outside basis differences. ASU 2019-12 also amends other aspects of Topic 740, Income Taxes, to help simplify and promote consistent application of US GAAP. The guidance is effective for interim and annual periods beginning after December 15, 2020, with early adoption permitted. We early adopted ASU 2019-12 in 2019 and it did not have a material impact on the Consolidated Financial Statements.

The only aspect of ASU 2019-12 that had a material impact on our consolidated financial statements was the removal of the exception related to intraperiod tax allocation. Starting in 2019, we followed the general intraperiod allocation of tax expense. We have a loss from continuing operations and subsequent to the adoption of ASU 2019-12, we determined the amount attributable to continuing operations without regard to the tax effect of other items. We prospectively applied the ASU 2019-12 amendment related to intraperiod tax allocation.

Had the Company not adopted ASU 2019-12, upon issuance of the convertible notes in 2019 (see Note 6 – Debt) a $12.0 million deferred tax benefit would have been recognized along with corresponding decreases to net loss and accumulated deficit. The Company had no intraperiod tax allocation items in prior years.

Due to our net loss position, the income tax benefit generated without the adoption of ASU 2019-12 was a non-cash benefit. The adoption of ASU 2019-12 did not impact our cash flows.

Stock-Based Compensation

We maintain equity incentive plans under which incentive stock options may be granted to employees and nonqualified stock options, restricted stock awards, restricted stock units and stock appreciation rights may be granted to employees, directors, consultants and advisors. In addition, we maintain an employee stock purchase plan (“ESPP”) under which employees may purchase shares of our common stock through payroll deductions.

Stock-based compensation expense related to stock options granted to employees and directors is recognized based on the grant date estimated fair values using the Black Scholes option pricing model. The value of the portion of the award that is ultimately expected to vest is recognized as expense ratably over the requisite service period.

Stock-based compensation expense related to restricted stock units granted to employees is recognized based on the grant-date fair value of each award and recorded as expense over the vesting period using the ratable method.

Stock-based compensation expense related to the ESPP is recognized based on the fair value of each award estimated on the first day of the offering period using the Black Scholes option pricing model and recorded as expense over the service period using the straight-line method.

Amortization of Debt Discount and Issuance Costs

Debt discount and issuance costs, consisting of legal and other fees directly related to the debt as well as the discount created by the bifurcation of the equity component and the debt component of the convertible senior notes due 2026 (the “2026 Notes”), are offset against gross proceeds from the issuance of debt and are amortized to interest expense over the estimated life of the debt based on the effective interest method.

Recent Accounting Standards

In June 2016, the Financial Accounting Standards Board (“FASB”) issued ASU 2016-13, ‘Financial Instruments — Credit Losses — Measurement of Credit Losses on Financial Instruments (“ASU 2016-13”), which requires that financial assets measured at amortized cost be presented at the net amount expected to be collected. The measurement of expected credit losses is based on historical experience, current conditions, and reasonable and supportable forecasts that affect collectability. ASU 2016-13 also eliminates the concept of “other-than-temporary” impairment when evaluating available-for-sale debt securities and instead focuses on determining whether any impairment is a result of a credit loss or other factors. An entity will recognize an allowance for credit losses on available-for-sale debt securities rather than an other-than-temporary impairment that reduces the cost basis of the investment. ASU 2016-13 is effective for annual and interim reporting periods beginning after December 15, 2019. We adopted ASU 2016-13 as of January 1, 2020 and the adoption did not have a material impact on the Consolidated Financial Statements.

In August 2018, the FASB issued ASU 2018-15, Intangibles-Goodwill and Other-Internal-Use Software (Subtopic 350-40): Customer's Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract, which expands the scope of costs associated with cloud computing arrangements that must be capitalized. Under the new guidance, costs associated with implementing a cloud computing arrangement that is a service contract must be capitalized and expensed over the term of the hosting arrangement. This guidance should be applied either retrospectively or prospectively to all implementation costs incurred after the date of adoption. We adopted ASU 2018-15 on January 1, 2020 and the adoption did not have a material impact on the Consolidated Financial Statements.

In November 2018, the FASB issued ASU 2018-18, Collaborative Arrangements (Topic 808): Clarifying the Interaction between Topic 808 and Topic 606, Revenue from Contracts with Customers, (“ASU 2018-18”), which makes targeted improvements to clarify the interaction between Topic 808, Collaborative Arrangements, and Topic 606, Revenue from Contracts with Customers. ASU 2018-18 is effective for fiscal years beginning after December 15, 2019, and interim periods within those fiscal years. We adopted ASU 2018-18 on January 1, 2020 and the adoption did not have a material impact on the Consolidated Financial Statements.

In November 2019, the FASB issued ASU 2019-08, Compensation-Stock Compensation (Topic 718) and Revenue from Contracts with Customers (Topic 606): Codification Improvements-Share-Based Consideration Payable to a Customer, which requires that an entity measure and classify share-based payment awards granted to a customer by applying the guidance in Topic 718. The amount recorded as a reduction of the transaction price is required to be measured on the basis of the grant-date fair value of the share-based payment award. We have adopted ASU 2019-08 as of January 1, 2020 and the adoption did not have any impact on the Consolidated Financial Statements.

In March 2020, the FASB issued ASU 2020-04, Reference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting (“ASU 2020-04’). ASU 2020-04 provides optional guidance for a limited period of time to ease the potential burden associated with the expected market transition from the London Inter-Bank Offer Rate ("LIBOR") to alternative reference rates. Companies can apply ASU 2020-04 immediately, however the guidance will only be available until December 31, 2022. The Company’s term loan utilizes LIBOR as the reference rate and we are currently evaluating the impact that adopting this new accounting standard will have on our Consolidated Financial Statements and related disclosures.

In August 2020, the FASB issued ASU 2020-06, Debt-Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging-Contracts in Entity’s Own Equity (Subtopic 815-40): Accounting for Convertible Instruments and Contracts in an Entity’s Own Equity (“ASU 2020-06”). ASU 2020-06 amends the guidance on convertible instruments and the derivatives scope exception for contracts in an entity's own equity, and also improves and amends the related earnings per share guidance. ASU 2020-06 will be effective for annual reporting periods after December 15, 2021 and interim periods within those annual periods and early adoption is permitted. We are currently evaluating the impact that adopting this new accounting standard will have on our Consolidated Financial Statements and related disclosures.

Net Loss Per Share

12 Months Ended

Dec. 31, 2020

Earnings Per Share [Abstract]

Net Loss Per Share

Note 2 — Net Loss Per Share

Basic net loss per share is computed by dividing net loss by the weighted average number of vested common shares outstanding during the period. Diluted net loss per share is computed by giving effect to all potentially dilutive common shares, including outstanding stock options, unvested restricted stock, warrants, convertible preferred stock and shares issuable under our ESPP, during the period using the treasury stock method and convertible notes using the if-converted method.

The following instruments were excluded from the computation of diluted net loss per share for the periods presented because their effect would have been antidilutive (in thousands):

	Years Ended December 31,
	2020		2019		2018
Options to purchase common stock		8,510		7,759		5,476
Warrants to purchase common stock		48		165		116
Restricted stock and performance units		1,117		839		547
Shares issuable related to the ESPP		12		27		107
Shares issuable upon conversion of convertible notes		16,675		16,675		—
Total shares		26,362		25,465		6,246

Research and Development Arrangements

12 Months Ended

Dec. 31, 2020

Research And Development [Abstract]

Research and Development Arrangements

Note 3 — Research and Development Arrangements

Our contract assets changed during the period, as follows (in thousands):

	December 31,
	2020		2019			2018
Contract asset from the 2016 Astellas Amendment
Balance at beginning of period	$	—	$	4,554		$	9,708
Services performed		—		—			11,713
Cash received for services		—		(4,554	)		(16,867	)
Balance at end of period	$	—	$	—		$	4,554

Amgen

We and Amgen continue activities related to novel small molecule therapeutics, including omecamtiv mecarbil, that activate cardiac muscle contractility for potential applications in the treatment of heart failure under the Amgen Agreement.

On November 23, 2020, we announced that Amgen has elected to terminate the Amgen Agreement and thereby end its collaboration with Cytokinetics, effective May 20, 2021, and Amgen intends to transition development and commercialization rights for omecamtiv mecarbil and CK-136 (formerly known as AMG 594) to Cytokinetics.

On December 23, 2020, we announced that Amgen notified us that Servier elected to terminate the Servier Agreement. The termination is effective as of March 18, 2021, after which all development, commercialization and other rights with respect to omecamtiv mecarbil previously granted by Amgen to Servier will revert to Amgen.

Omecamtiv mecarbil is an investigational cardiac myosin activator, developed for the potential treatment of heart failure with reduced ejection fraction (“HFrEF”), and was recently studied in GALACTIC-HF (Global Approach to Lowering Adverse Cardiac Outcomes Through Improving Contractility in Heart Failure), a positive Phase 3 cardiovascular outcomes clinical trial, and is the subject of an ongoing Phase 3 clinical trial, METEORIC-HF (Multicenter Exercise Tolerance Evaluation of Omecamtiv Mecarbil Related to Increased Contractility in Heart Failure), a Phase 3 clinical trial intended to evaluate the potential of omecamtiv mecarbil to increase exercise performance. CK-136, a novel mechanism cardiac troponin activator, was recently studied in a Phase 1 clinical study.

We recognize research and development revenue for reimbursements from Amgen of both internal costs of certain full-time employee equivalents and other costs related to the Amgen Agreement, which will terminate effective as of May 20, 2021. Research and development revenue from Amgen of $10.0 million in 2020, $13.8 million in 2019 and $1.9 million in 2018 consists of reimbursement of costs we incurred related to METEORIC-HF.

We had accounts receivable of $1.7 million from Amgen as of December 31, 2020 and $3.3 million as of December 31, 2019.

Astellas

Our strategic alliance with Astellas to advance novel therapies for diseases and medical conditions associated with muscle impairment and weakness commenced in 2013 under the License and Collaboration Agreement, dated June 21, 2013 between the parties (the “Astellas Agreement”).

In 2014, we and Astellas amended and restated the Astellas Agreement (the “2014 Astellas Amendment”) and expanded the objective of the collaboration to include spinal muscular atrophy (“SMA”) and potentially other neuromuscular indications for reldesemtiv and other fast skeletal muscle troponin activators (“FSTAs”). License revenues in 2018 related to our performance obligations under the 2014 Astellas Amendment. In 2018, we completed all our deliverables for the 2014 Astellas Amendment.

In 2016, we and Astellas amended the Astellas Agreement (the “2016 Astellas Amendment”) to expand the collaboration to include the development of reldesemtiv for the potential treatment of amyotrophic lateral sclerosis (“ALS”), as well as the possible development in ALS of other FSTAs previously licensed by us to Astellas, and Astellas paid us a $35.0 million non-refundable upfront amendment fee and an accelerated $15.0 million milestone payment for the initiation of the first Phase 2 clinical trial of reldesemtiv in ALS that was otherwise provided for in the Astellas Agreement, as if such milestone had been achieved upon the execution of the 2016 Astellas Amendment, and committed research and development consideration of $44.2 million, for total consideration of $94.2 million.

On April 23, 2020, we and Astellas entered into the two agreements referenced below which, taken together, amend and restate the Company’s research, development and commercialization collaboration with Astellas under the Astellas Agreement.

Fast Skeletal Regulatory Activator Agreement

The Company and Astellas entered into that certain Fast Skeletal Regulatory Activator Agreement, dated April 23, 2020 (the “Astellas FSRA Agreement”). As a result of the Astellas FSRA Agreement, the Company will now have exclusive control and responsibility for the Company's future development and commercialization of reldesemtiv, CK-601 and other fast skeletal regulatory activator (collectively “FSRA”) compounds and products, and accordingly, Astellas has agreed to terminate its license to all FSRA compounds and related products.

Under the Astellas FSRA Agreement, Astellas has agreed to pay one-third of the out-of-pocket clinical development costs which may be incurred in connection with the Company’s potential Phase 3 clinical trial of reldesemtiv in ALS, up to a maximum contribution by Astellas of $12 million. In addition, Astellas has agreed to non-cash contributions to the Company, which include the transfer of its existing inventories of active pharmaceutical ingredient of reldesemtiv and CK-601. Astellas has also agreed to the continued conduct of ongoing stability studies pertaining to such existing inventories of active pharmaceutical ingredient, at Astellas’ cost. In exchange, the Company will pay Astellas a low- to mid- single digit royalty on sales of reldesemtiv in the United States, Canada, United Kingdom and the European Union until the later of (i) ten years following the first commercial sale of such product in a major market country, or (ii) December 31, 2034, subject to certain royalty reduction provisions. The Company would not owe Astellas royalties on sales of reldesemtiv in any other country, or on the sale of any FSRA compounds or related products other than reldesemtiv.

License and Collaboration Agreement for Other Skeletal Sarcomere Activators

Under the Astellas OSSA Agreement, we are eligible to receive additional research and early and late stage development milestone payments for research and clinical milestones, including the initiation of certain clinical studies, the submission of an application for marketing authorization for a drug candidate to certain regulatory authorities and the commercial launch of collaboration products, which could total up to $250.0 million, except under certain scenarios. Additionally, $200.0 million in commercial milestones could be received under the Astellas OSSA Agreement provided certain sales targets are met. We are eligible to receive $1.0 million in research milestone payments under this collaboration for each future potential drug candidate. Due to the nature of drug development, including the inherent risk of development and approval of drug candidates by regulatory authorities, it is not possible to estimate if and when these milestone payments could be achieved or become due.

We continue to recognize research revenue for reimbursements from Astellas of internal costs of certain full-time employee equivalents, supporting collaborative research and development programs, and of other costs related to those programs.

License revenues and research and development revenues from Astellas for 2020, 2019 and 2018 were as follows (in thousands):

	Years Ended December 31,
	2020		2019		2018
License revenues	$	—	$	—	$	5,133
Reimbursements		6,555		13,106		22,253
Milestone fees		—		—		2,000
	$	6,555	$	13,106	$	29,386

We had accounts receivable from Astellas of $2.7 million as of December 31, 2020 and $1.9 million as of December 31, 2019.

RTW Transactions

On July 14, 2020, we entered into a series of transactions as described below with RTW Royalty Holdings Designated Activity Company (“RTW Royalty Holdings”) and Ji Xing, related to Cytokinetics’ proprietary small molecule cardiac myosin inhibitor product referred to as CK-3773274 (“CK-274”), a novel cardiac myosin inhibitor, and other assets (together, the “RTW Transactions”). The RTW Transactions include entering into a licensing and collaboration agreement with Ji Xing, the sale of Cytokinetics common stock to the RTW Investors (as defined below), an agreement to sell to RTW Royalty Holdings our interest in certain future royalties on net sales of products containing the compound mavacamten that is being developed by Bristol-Myers Squibb Company (formerly by MyoKardia, Inc.), and the ability for the Company to obtain additional funding in the future from RTW Royalty Holdings, upon the achievement of certain clinical trial milestones, in exchange for future royalty payments as further discussed below. As a result, we have or expect to receive a combination of committed capital, funding and sale proceeds from the RTW Investors, RTW Royalty Holdings and Ji Xing.

The RTW Transactions were entered into with parties that are affiliated and in contemplation of one another and, accordingly, we have assessed the accounting for these transactions in the aggregate. We concluded that there were three units of accounting in the RTW Transactions as further described below. The Company allocated the total consideration in accordance with ASC 820, Fair Value Measurement, and ASC 606, Revenue from Contracts with Customers, as follows (in thousands):

	Allocated Consideration
Units of Accounting:
License and collaboration (residual)	$	36,501
Royalty (fair value)		87,000
Common stock (fair value)		36,499
Total consideration	$	160,000

License and Collaboration Agreement

We entered into a License and Collaboration Agreement (the “Ji Xing License Agreement”) with Ji Xing, pursuant to which we granted to Ji Xing an exclusive license to develop and commercialize CK-274 in People’s Republic of China (including the Hong Kong SAR and Macau SAR) (together “China”) and Taiwan. Under the terms of the Ji Xing License Agreement, we received from Ji Xing a nonrefundable upfront payment of $25.0 million. We may be eligible to receive from Ji Xing milestone payments totaling up to $200.0 million for the achievement of certain development and commercial milestone events in connection to CK-274 in the field of obstructive hypertrophic cardiomyopathy (“oHCM”) and/or non-obstructive hypertrophic cardiomyopathy (“nHCM”) and other indications. In addition, Ji Xing will pay us tiered royalties in the low-to-high teens range on the net sales of the products containing CK-274 in China and Taiwan, subject to certain reductions for generic competition, patent expiration and payments for licenses to third party patents.

Ji Xing will be responsible for the development and commercialization of CK-274 at its own cost and is required to use diligent efforts to develop and commercialize CK-274 in China and Taiwan. The development of CK-274 will be initially focused on hypertrophic cardiomyopathy, and Ji Xing will have the opportunity to participate in Cytokinetics’ global pivotal clinical trials of CK-274. Cytokinetics or a designated supplier will supply CK-274 to Ji Xing either as a finished product or as an active pharmaceutical ingredient.

The Ji Xing License Agreement, unless terminated earlier, will continue on a market-by-market basis until expiration of the relevant royalty term. Ji Xing has the right to terminate the Ji Xing License Agreement for convenience. Each party may terminate the Ji Xing License Agreement for the other party’s uncured material breach, insolvency, or failure to perform due to extended force majeure events. Cytokinetics may also terminate the Ji Xing License Agreement if Ji Xing challenges Cytokinetics’ patents or undergoes certain change of control transactions. Rights granted to Ji Xing in relation to CK-274 will revert to Cytokinetics upon termination, and, under certain circumstances, subject to a low single digit royalty payment by the Company to Ji Xing on the net sales of the products containing the compound CK-274 in China and Taiwan.

License revenues and milestone revenues for 2020, 2019 and 2018 were as follows (in thousands):

	Years Ended December 31,
	2020		2019		2018
License revenues	$	36,501	$	—	$	—
Milestone revenues		2,500		—		-
	$	39,001	$	—	$	—

We assessed this arrangement in accordance with ASC 606 and concluded that there is one performance obligation relating to the license of functional intellectual property. The performance obligation was satisfied, and we recognized the residual allocation of arrangement consideration as revenue of $36.5 million for 2020. Due to the nature of development, including the inherent risk of development and approval by regulatory authorities, we are unable to estimate if and when the development milestone payments could be achieved or become due and, accordingly, we consider the milestone payments to be fully constrained and exclude the milestone payments from the initial transaction price.

The consideration related to sales-based milestone payments, including royalties, will be recognized when the related sales occur under the sales- and usage-based royalty exception as these amounts have been determined to relate predominantly to the license.

We re-evaluate the probability of achievement of development milestones and any related constraints each reporting period. We will include consideration, without constraint, in the transaction price to the extent it is probable that a significant reversal in the amount of cumulative revenue recognized will not occur.

We earned a $2.5 million milestone from Ji Xing as of December 31, 2020 for the first patient dosed in Cohort 2 of REDWOOD-HCM (Randomized Evaluation of Dosing With CK-274 in Obstructive Outflow Disease in HCM). We determined recognition of the milestone during 2020 based on clinical trial progress. Our determination that we expected to earn the $2.5 million milestone resulted in a change in the overall transaction price of the collaboration agreement, as it was probable that a significant reversal of cumulative revenue would not occur. A corresponding contract asset was recorded in other current assets in our consolidated balance sheet as of December 31, 2020.

Royalty Purchase Agreement

We entered into a Royalty Purchase Agreement (the “RTW Royalty Purchase Agreement”) with RTW Royalty Holdings, pursuant to which we sold our right to receive certain payments on the net sales of products containing the compound mavacamten, a cardiac myosin inhibitor (the “Mavacamten Royalty”), under the Research Collaboration Agreement, dated August 24, 2012, between us and MyoKardia, Inc. to RTW Royalty Holdings for a one-time payment of $85.0 million. The RTW Royalty Purchase Agreement transaction closed on November 13, 2020.

We accounted for the sale of our rights to the Mavacamten Royalty as deferred revenue under ASC 470, Debt, since the arrangement is a sale of our future right to receive royalties and not a sale of the underlying patents or related intangibles. Further, we do not have any significant continuing involvement in the further development, commercialization or sale of mavacamten, the one-time payment is not required to be paid back to RTW Royalty Holdings, the investor’s return is not limited and will be driven by net sales, and RTW Royalty Holdings does not have any recourse to the Company’s assets.

The allocation of the consideration for the RTW Transactions resulted in $87.0 million being allocated to the RTW Royalty Purchase Agreement representing its fair value. The fair value was determined using an income approach method based on management’s estimates of the discounted cash flows to be received over the term of the related royalty agreement, which are Level 3 fair value inputs. Management’s estimates included significant unobservable inputs. These inputs are derived using internal management estimates developed based on third party data and reflect management’s judgements, current market conditions surrounding competing products, and forecasts. The significant unobservable inputs include the estimated patient population, estimated selling price, estimated peak sales and sales ramp, the expected term of the royalty stream, and timing of the expected launch. The $87.0 million recorded as deferred revenue will be amortized using the units-of-revenue method.

We will recognize revenue related to the sale of the Mavacamten Royalty using the units-of-revenue method. Under the units-of-revenue method, the revenue to be recognized for a period is calculated by computing a ratio of the Mavacamten Royalty paid to RTW Royalty Holdings for a given period to the total payments expected to be made to RTW Royalty Holdings over the term of the agreement, and then applying that ratio to the period's cash payment. We will record any adjustments due to changes in the underlying royalties on a cumulative catch-up basis.

Common Stock Purchase Agreement

On July 14, 2020, we entered into Common Stock Purchase Agreements (each, a “CSPA”) with each of RTW Master Fund, Ltd., RTW Innovation Master Fund, Ltd. and RTW Venture Fund Limited (collectively, the “RTW Investors”). The CSPAs provided for the sale and issuance of an aggregate of 2.0 million shares of common stock of Cytokinetics (the “Shares”) at a price per share of $25.00 and an aggregate purchase price of $50.0 million. The closing occurred on July 14, 2020. The RTW Investors have agreed to certain trading and other restrictions with respect to the Shares, including a restriction on sales or other transfers of the Shares, subject to certain exceptions, for a period of two years from the closing date, which period will be extended if certain conditions are met. The restrictions resulted in a premium paid by RTW investors of $13.5 million which represents the excess amount paid over the fair value of the Shares. The premium was determined by analyzing the holding period discount applied to the 30-day average stock price as of July 14, 2020, which is a Level 2 fair value inputs. The cash received less the calculated premium is the $36.5 million fair value of the common stock recorded.

Funding Agreement

We entered into a Funding Agreement (the “Funding Agreement”) with RTW Royalty Holdings. Pursuant to the Funding Agreement, RTW Royalty Holdings has committed to provide up to $90.0 million (the “Funding Commitment”) to fund our development and commercialization of CK-274 in nHCM and oHCM. Half of the Funding Commitment will be available, at our option, if certain clinical trial milestones of CK-274 for oHCM are achieved by January 14, 2023, and the remaining $45.0 million of the Funding Commitment will be available, at our option, if certain clinical trial milestones of CK-274 for nHCM are achieved by January 14, 2024. If we develop CK-274 in another indication, we will negotiate an additional funding commitment from RTW to fund our development and commercialization of CK-274 in such other indication (other than oHCM or nHCM).

In exchange for the Funding Commitment and upon receipt of such funding from RTW Royalty Holdings, we have agreed to make payments to RTW Royalty Holdings equal to 2%, if RTW Royalty Holdings funds $45.0 million of the Funding Commitment, or 4%, if RTW Royalty Holdings funds the full $90.0 million of the Funding Commitment, in each case in respect of net sales of CK-274 by us and any of our licensees in the United States, the European Union, Switzerland, the United Kingdom and certain other countries in Europe (collectively referred to as the “CK-274 Territory”). In addition, should we exercise our option draw borrowings pursuant to the Funding Agreement, such agreement contains certain covenants applicable to us, including, among other things, development and commercialization diligence obligations in connection to the CK-274 Territory, use of proceeds, reporting and encumbrances. There are no performance obligations related to the Funding Agreement, as access to the Funding Commitment is at the option of the Company and based upon the achievement of certain development milestones.

The Funding Agreement contains customary conditions to disbursement, which may include the consent of our Lenders at the time of disbursement. On July 16, 2020, we entered into an amendment to the Term Loan Agreement, which permits, subject to entry into an intercreditor agreement between Oxford (as security agent for the Lenders) and RTW Royalty Holdings in form and substance reasonably satisfactory to the Lenders and RTW Royalty Holdings, the draw of funding under the Funding Agreement and the grant of a security interest to RTW Royalty Holdings in the intellectual property located in the United States and accounts receivable related to CK-274 thereunder.

The Company granted RTW Royalty Holdings a security interest in all of its rights, title and interest in, to certain intellectual property, accounts receivable and any proceeds from such collateral. The security interest will automatically terminate when total net payments made to RTW Royalty Holdings exceed a certain agreed threshold.

Fair Value Measurements

12 Months Ended

Dec. 31, 2020

Fair Value Disclosures [Abstract]

Fair Value Measurements

Note 4 — Fair Value Measurements

We value our financial assets and liabilities at fair value, defined as the price that would be received for assets when sold or paid to transfer a liability in an orderly transaction between market participants at the measurement date (exit price). We utilize market data or assumptions that we believe market participants would use in pricing the asset or liability, including assumptions about risk and the risks inherent in the inputs to the valuation technique. These inputs can be readily observable, market corroborated or generally unobservable.

We primarily apply the market approach for recurring fair value measurements and endeavors to utilize the best information reasonably available. Accordingly, we use valuation techniques that maximize the use of observable inputs and minimize the use of unobservable inputs to the extent possible and consider the security issuers’ and the third-party issuers’ credit risk in our assessment of fair value.

We classify fair value based on the observability of those inputs using a hierarchy that prioritizes the inputs used to measure fair value. The hierarchy gives the highest priority to unadjusted quoted prices in active markets for identical assets or liabilities (Level 1 measurement) and the lowest priority to unobservable inputs (Level 3 measurement):

Level 1 — Observable inputs, such as quoted prices in active markets for identical assets or liabilities;

Level 2 — Inputs, other than the quoted prices in active markets, that are observable either directly or through corroboration with observable market data; and

Level 3 — Unobservable inputs, for which there is little or no market data for the assets or liabilities, such as internally-developed valuation models.

Fair Value of Financial Assets

The follow tables set forth the fair value of our financial assets, which consists of cash equivalents and investments classified as available-for-sale securities, that were measured on a recurring basis (in thousands):

	December 31, 2020
	Fair Value Hierarchy Level	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
Money market funds	Level 1	$	80,050	$	—	$	—		$	80,050
U.S. Treasury securities	Level 1		274,407		147		(8	)		274,546
Agency bonds	Level 2		51,581		15		(3	)		51,593
Commercial paper	Level 2		49,500		3		(1	)		49,502
Corporate obligations	Level 2		42,392		7		(11	)		42,388
		$	497,930	$	172	$	(23	)	$	498,079

	December 31, 2019
	Fair Value Hierarchy Level	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
Money market funds	Level 1	$	31,535	$	—	$	—		$	31,535
U.S. Treasury securities	Level 1		134,845		72		(1	)		134,916
Agency bonds	Level 2		47,024		23		(9	)		47,038
Commercial paper	Level 2		10,435		4		—			10,439
Corporate obligations	Level 2		40,426		24		(7	)		40,443
		$	264,265	$	123	$	(17	)	$	264,371

Interest income was $5.3 million and $4.5 million in 2020 and 2019, respectively.

Investments available for sale exclude an investment in equity classified as a Level 1 investment in our short-term investments with a fair value of $1.0 million and an unrealized gain of $0.3 million at December 31, 2019. As of December 31, 2020, the Level 1 investment had been divested. Unrealized losses were not due to changes in credit risk and we believe investments with an unrealized loss would be held until maturity.

No credit losses on debt securities were recognized in either 2020 or 2019. In its evaluation to determine expected credit losses, management considered all available historical and current information, expectations of future economic conditions, the type of security, the credit rating of the security, and the size of the loss position, as well as other relevant information. The Company does not intend to sell, and is unlikely to be required to sell, any of these available-for-sale investments before their effective maturity or market price recovery.

The carrying amount of our accounts receivable and accounts payable approximates fair value due to the short-term nature of these instruments.

Fair value of financial liabilities:

As of December 31, 2020 and 2019, the fair value of our term loan approximated its carrying value of $46.2 million and $45.1 million, respectively, because it is carried at a market observable interest rate, which is a Level 2 input (see Note 6 – Debt).

As of December 31, 2020, the estimated fair value of our convertible notes was $638.7 million and was based upon observable, Level 2 inputs, including pricing information from recent trades of the convertible notes (see Note 6 – Debt).

As of December 31, 2020 and 2019, the fair value of the RPI Liability related to the sale of future royalties is based on our current estimates of future royalties expected to be paid to RPI, over the life of the arrangement, which are considered Level 3 inputs (see Note 7 – Liability Related to Sale of Future Royalties).

There were no transfers between Level 1, Level 2, and Level 3 during the periods presented.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Balance Sheet Components

12 Months Ended

Dec. 31, 2020

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Balance Sheet Components

Note 5 — Balance Sheet Components

Our property and equipment consisted of (in thousands):

	December 31,
	2020			2019
Property and equipment, net:
Laboratory equipment	$	18,160		$	18,741
Computer equipment and software		2,940			2,940
Office equipment, furniture and fixtures		1,885			1,823
Leasehold improvements		5,872			5,221
Construction in progress		9,130			—
Total property and equipment		37,987			28,725
Less: Accumulated depreciation and amortization		(24,641	)		(24,195	)
	$	13,346		$	4,530

Depreciation expense was $1.8 million for 2020 and $1.3 million for 2019.

Our accrued liabilities were (in thousands):

	December 31,
	2020		2019
Accrued liabilities:
Clinical and preclinical costs	$	6,124	$	2,215
Compensation related		11,787		8,343
Other accrued expenses		1,404		1,565
Total accrued liabilities	$	19,315	$	12,123

We sponsor a 401(k) defined contribution plan covering all employees and contributed $0.9 million and $0.6 million to this plan in 2020 and 2019, respectively.

Debt

12 Months Ended

Dec. 31, 2020

Debt Disclosure [Abstract]

Debt

Note 6 — Debt

Term Loan

Prior to May 17, 2019 we maintained a loan and security agreement dated as of October 19, 2015, as amended (the “Original Loan Agreement”) with the Lenders to fund our working capital and other general corporate needs.

On May 17, 2019, we entered into a new loan and security agreement (the “Term Loan Agreement”) with the Lenders for $45.0 million (the “Term Loan”) and terminated the Original Loan Agreement. The proceeds of the Term Loan were used in part to repay in full all of the outstanding term loans under the Original Loan Agreement in an aggregate principal amount of $42.0 million. On November 6, 2019 and November 7, 2019, the Company entered into a First Amendment and a Second Amendment to the Term Loan Agreement. The Term Loan Agreement, as amended, permits the issuance of the Convertible Notes and Capped Call Transactions discussed below. On July 16, 2020, the Company and the Lenders entered into the Third Amendment to the Term Loan Agreement, which amended the Term Loan Agreement to permit (i) the sale of the Mavacamten Royalty under the RTW Royalty Purchase Agreement and (ii) subject to entry into an intercreditor agreement between Oxford (as security agent for the Lenders) and RTW Royalty Holdings in form and substance reasonably satisfactory to the Lenders and RTW Royalty Holdings, permits the draw of funding under the Funding Agreement and the grant of a security interest to RTW Royalty Holdings in the intellectual property located in the United States and accounts receivable related to CK-274.

The Term Loan was accounted for as a debt modification in a non-troubled debt restructuring based on a comparison of the present value of the cash flows under the terms of the debt immediately before and after the effective date of the Term Loan, which resulted in a change of less than 10%. As a result, issuance costs paid to the lender in connection with the Term Loan were recorded as a reduction of the carrying amount of the debt liability and were not significant. Unamortized issuance costs as of the date of the modification were amortized to interest expense over the repayment term of Term Loan.

Both borrowings under the Original Loan Agreement and Term Loan bear interest at an annual rate equal to the greater of (a) 8.05% or (b) the sum of 6.81% plus the 30-day U.S. LIBOR rate. The borrowing under the Original Loan Agreement was repayable in monthly interest-only payments through November 2019 followed by 35 months of monthly payments of interest and principal. The borrowing under the Term Loan is repayable in monthly interest-only payments through December 31, 2020. The interest-only period was automatically extended until July 1, 2021 as a result of the Company’s initiation of a Phase 2 trial for CK-274 in cardiomyopathy and has been extended through December 31, 2021 as a result of the achievement of positive results in GALACTIC-HF, the trial of omecamtiv mecarbil in chronic heart failure as announced on October 8, 2020. The ultimate interest-only period will be followed by equal monthly payments of principal and interest to the maturity date in December 2023. The ultimate interest-only period will be followed by equal monthly payments of principal and interest to the maturity date in December 2023. We are required to make a final payment upon loan maturity of 6.00% of the notes payable, which we accrete over the life of the Term Loan. Our obligations under the Term Loan Agreement are secured by substantially all our current and future assets, other than our intellectual property.

Interest expense for the Term Loan was $4.9 million, $5.2 million and $3.8 million for 2020, 2019 and 2018 respectively. As of December 31, 2020, the interest rate applicable to borrowings under the Term Loan was 8.05%.

The Term Loan Agreement contains customary representations and warranties and customary affirmative and negative covenants applicable to us and includes customary events of default, including but not limited to the nonpayment of principal or interest, violations of covenants and material adverse changes. Upon an event of default, the Lenders may, among other things, accelerate the loans and foreclose on the collateral. Our obligations under the Term Loan Agreement are secured by substantially all our current and future assets, other than our intellectual property. If the Term Loan becomes subject to mandatory prepayment under these provisions, we are subject to certain prepayment premiums of 3.00% in the first year, 2.00% in the second year and 1.00% in the third year and thereafter. We determined that these contingent prepayment provisions were an embedded component that qualified as a derivative which should be bifurcated from the Term Loan and accounted for separately from the host contract. As of December 31, 2020, the fair value of this embedded derivative was immaterial.

Future minimum payments under the Term Loan Agreement are (in thousands):

Years ending December 31:
2021		3,673
2022		25,330
2023		28,079
Future minimum payments		57,082
Less: Interest and final payment		(12,082	)
Term Loan, gross	$	45,000

Convertible Notes

On November 13, 2019, the Company issued $138.0 million aggregate principal amount of 4.0% convertible senior notes due 2026 (the “2026 Notes”). The 2026 Notes are unsecured obligations and bear interest at an annual rate of 4.0% per year, payable semi-annually on May 15 and December 15 of each year, beginning May 15, 2020. The 2026 Notes are governed by an indenture between the Company and U.S. Bank National Association, as trustee. The 2026 Notes will mature on November 15, 2026, unless earlier repurchased or redeemed by the Company or converted at the option of the holders. The Company may redeem the 2026 Notes prior to the maturity date but is not required to and no sinking fund is provided for the 2026 Notes. The 2026 Notes may be converted, under certain circumstances as described below, based on an initial conversion rate of 94.7811 shares of common stock per $1,000 principal amount (which represents an initial conversion price of $10.55 per share). The conversion rate for the 2026 Notes will be subject to adjustment upon the occurrence of certain specified events. In addition, upon the occurrence of a make-whole fundamental change (as defined in the indenture), the Company will, in certain circumstances, increase the conversion rate by a number of additional shares for a holder that elects to convert its notes in connection with such make-whole fundamental change. The Company received approximately $133.9 million in net proceeds, after deducting the initial purchasers’ discount, from the issuance of the 2026 Notes.

The 2026 Notes may be converted at the option of the holder under any of the following circumstances: (1) during any calendar quarter commencing after the calendar quarter ending on March 31, 2020 (and only during such calendar quarter), if the last reported sale price of the Company’s common stock for at least 20 trading days (whether or not consecutive) during a period of 30 consecutive trading days ending on, and including, the last trading day of the immediately preceding calendar quarter exceeds 127.5% of the last reported sale price of the Company’s common stock on November 7, 2019; (2) during the 5 consecutive business days immediately after any 10 consecutive trading day period (such 10 consecutive trading day period, the “measurement period”) if the trading price per $1,000 principal amount of 2026 Notes for each trading day of the measurement period was less than 98% of the product of the last reported sale price per share of the Company’s common stock on such trading day and the conversion rate on such trading day; (3) upon the occurrence of certain corporate events or distributions on the Company’s common stock; (4) if the Company calls the 2026 Notes for redemption; and (5) at any time from, and including, July 15, 2026 until the close of business on the scheduled trading day immediately before the maturity date, November 15, 2026. The Company will settle conversions by paying or delivering, as applicable, cash, shares of the Company’s common stock, or a combination of cash and shares of the Company’s common stock, at the Company’s election, based on the applicable conversion rate.

The 2026 Notes will be redeemable, in whole or in part, at the Company’s option at any time, and from time to time, on or after November 20, 2023 and, in the case of any partial redemption, on or before the 60th scheduled trading day before the maturity date, at a cash redemption price equal to the principal amount of the 2026 Notes to be redeemed, plus accrued and unpaid interest, if any, to, but excluding, the redemption date but only if the last reported sale price per share of the Company’s common stock exceeds 130% of the conversion price on (1) each of at least 20 trading days, whether or not consecutive, during the 30 consecutive trading days ending on, and including, the trading day immediately before the date the Company sends the related redemption notice; and (2) the trading day immediately before the date the Company sends such notice. If a “fundamental change” (as defined in the indenture) occurs, then, subject to certain exceptions, holders may require the Company to repurchase their 2026 Notes at a cash repurchase price equal to the principal amount of the 2026 Notes to be repurchased, plus accrued and unpaid interest, if any, to, but excluding, the fundamental change repurchase date.

In accounting for the issuance of the 2026 Notes, the Company separated the 2026 Notes into liability and equity components. The carrying amount of the liability component of approximately $84.2 million was calculated by using a discount rate of 12.0%, which was estimated to be the Company’s borrowing rate on the date of the issuance of the notes for a similar debt instrument without the conversion feature. The carrying amount of the equity component of approximately $49.5 million, representing the conversion option, was determined by deducting the fair value of the liability component from the par value of the 2026 Notes. The equity component of the 2026 Notes is included in additional paid-in capital in the consolidated balance sheets and is not remeasured as long as it continues to meet the conditions for equity classification. The difference between the principal amount of the 2026 Notes and the liability component (the “debt discount”) is amortized to interest expense using the effective interest method over the term of the 2026 Notes.

Debt issuance costs for the issuance of the 2026 Notes were approximately $5.0 million, consisting of initial purchasers' discount and other issuance costs. In accounting for the transaction costs, the Company allocated the total amount incurred to the liability and equity components using the same proportions as the proceeds from the 2026 Notes. Transaction costs attributable to the liability component were approximately $3.1 million, were recorded as debt issuance cost (presented as contra debt in the consolidated balance sheet) and are being amortized to interest expense over the term of the 2026 Notes. The transaction costs attributable to the equity component were approximately $1.9 million and were netted with the equity component in stockholders’ equity. As of December 31, 2020, the unamortized debt issuance cost for the 2026 Notes was $2.8 million.

The following table presents the total amount of interest cost recognized relating to the 2026 Notes for 2020 and 2019 (in thousands):

	Years Ended December 31,
	2020		2019
Contractual interest expense	$	5,520	$	721
Accretion of debt discount		5,246		673
Accretion of debt issuance costs		52		6
Total interest costs recognized	$	10,818	$	1,400

The effective interest rate on the liability component of the 2026 Notes was 12.5% for the year ended December 31, 2020, which remains unchanged from the date of issuance. The remaining unamortized debt discount was $45.7 million as of December 31, 2020 and will be amortized over approximately 6.0 years.

Capped Call Transactions

In connection with the offering of the 2026 Notes, the Company entered into privately-negotiated capped call transactions with one of the underwriters in the offering or its affiliate. The Company used approximately $13.4 million of the net proceeds from the offering of the 2026 Notes to pay the cost of the capped call transactions. The capped call transactions are expected generally to reduce potential dilution to the Company’s common stock upon any conversion of the 2026 Notes and/or offset any cash payments the Company is required to make in excess of the principal amount of converted 2026 Notes, as the case may be, in the event that the market value per share of the Company’s common stock, as measured under the terms of the capped call transactions at the time of exercise, is greater than the strike price of the capped call transactions (which initially corresponds to the initial conversion price of the 2026 Notes, and is subject to certain adjustments), with such reduction and/or offset subject to a cap initially equal to approximately $14.07 per share (which represents a premium of approximately 70% over the last reported sale price of the Company’s common stock on November 7, 2019), subject to certain adjustments. The capped call transactions are separate transactions, entered into by the Company and are not part of the terms of the 2026 Notes.

Given that the transactions meet certain accounting criteria, the convertible note capped call transactions are recorded in stockholders’ equity, and they are not accounted for as derivatives and are not remeasured each reporting period. As of December 31, 2020, the Company had not purchased any shares under the convertible note capped call transactions.

Liability Related to Sale of Future Royalties

12 Months Ended

Dec. 31, 2020

Royalty Liability [Abstract]

Note 7 — Liability Related to Sale of Future Royalties to RPI

In February 2017, we entered into the RPI Royalty Purchase Agreement with RPI under which we sold a portion of our right to receive royalties on potential net sales of omecamtiv mecarbil (and potentially other compounds with the same mechanism of action) under the Amgen Agreement to RPI for a payment of $90.0 million, which is non-refundable even if omecamtiv mecarbil is never commercialized. Concurrently, we entered into a common stock purchase agreement with RPI through which RPI purchased 875,656

shares of the Company’s common stock for $10.0 million. We allocated the consideration and issuance costs on a relative fair value basis to the RPI Liability and the common stock, which resulted in the RPI Liability being initially recognized at $92.3 million.

The RPI Royalty Purchase Agreement further provides that in the event Amgen elects to terminate the Amgen Agreement, we are obliged to enter into an agreement with RPI to preserve RPI’s rights under the RPI Royalty Purchase Agreement, which includes the payment by Cytokinetics of 4.5% of its worldwide net sales of omecamtiv mecarbil and other Amgen Alliance Compounds, subject to a potential increase of up to an additional 1% under certain circumstances (delay in US marketing approval). Our obligation to enter into a new agreement with RPI does not impact our accounting treatment of the RPI Liability or our estimates.

We account for the RPI Liability as a liability primarily because we have significant continuing involvement in generating the royalty stream. If and when omecamtiv mecarbil is commercialized and royalties become payable, we will recognize the portion of royalties paid to RPI as a decrease to the RPI Liability with a corresponding reduction in cash.

The carrying amount of the RPI Liability is based on our estimate of the future royalties to be paid to RPI over the life of the arrangement as discounted using an imputed rate of interest. The excess of future estimated royalty payments over the $92.3 million of allocated proceeds, less issuance costs, is recognized as non-cash interest expense using the effective interest method. The imputed rate of interest on the unamortized portion of the RPI Liability was approximately 15% as of December 31, 2020 and 17% as of December 31, 2019.

We periodically assess the amount and timing of expected royalty payments using a combination of internal projections and forecasts from external sources. To the extent such payments are greater or less than our initial estimates or the timing of such payments is materially different than its original estimates, we will prospectively adjust the amortization of the RPI Liability and the effective interest rate.

There are a number of factors that could materially affect the amount and timing of royalty payments, most of which are not within our control. The RPI Liability is recognized using significant unobservable inputs. These inputs are derived using internal management estimates developed based on third party data, including data historically provided by Amgen, and reflect management’s judgements, current market conditions surrounding competing products, and forecasts. The significant unobservable inputs include the estimated patient population, estimated selling price, estimated peak sales and sales ramp, the expected term of the royalty stream, timing of the expected launch and its impact on the royalty rate as well as the overall probability of a success. A significant change in unobservable inputs could result in a material increase or decrease to the effective interest rate of the RPI Liability.

We have updated the analysis to include the data released on October 8, 2020 relating to GALACTIC-HF. Our estimates regarding the amount and timing of future royalty payments have not changed as a result of Amgen’s election to terminate the Amgen Agreement or Servier’s election to terminate the Servier Agreement.

Changes to the RPI Liability related to the sale of future royalties are as follows (in thousands):

	2020		2019
Beginning balance, January 1	$	143,276	$	122,473
Interest accretion		22,713		20,737
Amortization of issuance costs		79		66
Ending balance, December 31	$	166,068	$	143,276

Stockholders' Equity

12 Months Ended

Dec. 31, 2020

Equity [Abstract]

Stockholders' Equity

Note 8 — Stockholders’ Equity

Common Stock Purchase Agreements

On July 14, 2020, we entered into a CSPA with each of the RTW Investors. The CSPAs provide for the sale and issuance of an aggregate of 2.0 million shares of common stock of Cytokinetics (the “Shares”) at a price per share of $25.00 and an aggregate purchase price of $50.0 million (see Note 3 – Research and Development Arrangements). The cash adjusted for the calculated premium is the $36.5 million fair value of the common stock recorded.

Public Offering of Common Stock

In July 2020, we closed an underwritten public offering of 8.4 million shares of our common stock at a public offering price per share of $24.00, which included the exercise in full by the underwriters of their option to purchase up to 1,093,750 shares of our common stock at the same price. The gross proceeds were $201.3 million and net proceeds were approximately $188.9 million, after deducting underwriting discounts, commissions and offering costs.

Equity Incentive Plan

Our amended and restated 2004 Equity Incentive Plan (the “2004 Plan”) provides for us to grant incentive stock options, nonstatutory stock options, restricted stock, stock appreciation rights, restricted stock units, performance shares and performance units to employees, directors and consultants. We may grant options for terms of up to ten years at prices not lower than 100% of the fair market value of our common stock on the date of grant. Options granted to new employees generally vest 25% after one year and monthly thereafter over a period of four years. Options granted to existing employees generally vest monthly over a period of four years. As of December 31, 2020, we have 2.6 million shares of common stock reserved and available for issuance under the 2004 Plan.

In May 2019, the Company’s stockholders approved an amendment to the Amended and the 2004 Plan to increase the number of authorized shares reserved for issuance under the 2004 Plan by 4.1 million shares. In May 2020, the Company’s board of directors approved an amendment to the 2004 Plan to increase the number of authorized shares reserved for issuance under the 2004 Plan by 0.8 million shares for inducement grants to new employees. We started granting inducement grants in September 2020. As of December 31, 2020, an insignificant number of stock options were granted and 2.6 million authorized shares were available for grant under the 2004 Plan.

Stock option activity in 2020 was as follows:

	Stock Options Outstanding			Weighted Average Exercise Price per Share		Weighted Average Remaining Contractual Life (in years)		Aggregate Intrinsic Value (in millions)
Balance at December 31, 2018		6,454,037		$	8.72
Granted		1,785,673			8.41
Exercised		(126,793	)		7.78
Forfeited		(353,905	)		10.44
Balance at December 31, 2019		7,759,012		$	8.59
Granted		1,944,562			15.59
Exercised		(967,571	)		8.27
Forfeited		(234,054	)		16.06
Balance at December 31, 2020		8,501,949		$	10.02		6.6	$	91.9
Exercisable at December 31, 2020		5,704,396		$	8.91		5.6	$	67.8

We expect all outstanding options to vest. The intrinsic value of stock options exercised, calculated based on the difference between the market value at the date of exercise and the exercise price, was $14.0 million for 2020, $0.5 million for 2019 and $0.7 million for 2018. The intrinsic value of stock options outstanding at December 31, 2020 was $91.9 million.

Restricted stock unit (“RSU”) activity in 2020 was as follows:

	Number of Restricted Stock Units			Weighted Average Award Date Fair Value per Share
Balance at December 31, 2018		546,500		$	8.53
Granted		607,150			7.14
Released		(266,500	)		8.84
Forfeited		(48,075	)		7.34
Balance at December 31, 2019		839,075		$	7.49
Granted		731,225			14.40
Released		(435,450	)		7.72
Forfeited		(18,208	)		10.37
Balance at December 31, 2020		1,116,642		$	11.88

RSUs generally vest annually over two to three years. For 2020, the fair value of RSUs vested, calculated based on the units vested multiplied by the closing price of our common stock on the date of vesting, was $6.1 million.

Employee Stock Purchase Plan

Under our 2015 Employee Stock Purchase Plan (the “ESPP”), employees may purchase common stock up to a specified maximum amount at a price equal to 85% of the fair market value at certain plan-defined dates. In May 2020, the Company’s stockholders approved an amendment to the ESPP to increase the number of common stock shares reserved for issuance under the ESPP by 0.5 million shares.

We issued 11,565 shares at an average price of $14.64 per share during 2020, 172,113 shares at an average price of $6.43 per share in 2019, and 144,822 shares at an average price of $6.40 per share in 2018 pursuant to the ESPP. At December 31, 2020, we have 446,820 shares of common stock reserved for issuance under the ESPP.

Stock-Based Compensation Expense

We use the Black-Scholes option pricing model to determine the fair value of stock option grants to employees and directors and employee stock purchase plan shares. The fair value of share-based payments was estimated on the date of grant based on the following assumptions:

Year Ended December

31, 2020

Year Ended December

31, 2019

Year Ended December

31, 2018

Options

ESPP

Options

ESPP

Options

ESPP

Risk-free interest rate

0.42% to 1.8%

0.11% to 1.8%

1.6% to 3.0%

1.8% to 2.4%

2.3% to 3.0%

1.5% to 2.5%

Volatility

74% to 75%

73% to 76%

73% to 74%

Expected term in years

6.5 to 6.6

0.5

6.5

0.6

6.5

0.5

Expected dividend yield

0%

We use U.S. Treasury zero-coupon issues with remaining terms similar to the expected terms of the options for the risk-free interest rate. We use our own volatility history based on its stock’s trading history and our own historical exercise and forfeiture activity to estimate expected term for option grants. We do not anticipate paying dividends in the foreseeable future and use an expected dividend yield of zero. We do not estimate forfeitures in our stock-based compensation.

We measure compensation expense for restricted stock units at fair value on the date of grant and recognize the expense over the expected vesting period. We recognize stock-based compensation expense on a ratable basis over the requisite service period, generally the vesting period of the award for share-based awards.

Stock-based compensation expense for 2020 and 2019 was as follows (in thousands):

	Years Ended December 31,
	2020		2019		2018
Research and development	$	6,949	$	4,260	$	5,101
General and administrative		10,671		6,499		4,660
	$	17,620	$	10,759	$	9,761

Stock-based compensation expense for share-based awards to non-employees was $0.2 million in 2020, $0.2 million in 2019 and $0.1 million in 2018.

As of December 31, 2020, we expect to recognize $22.2 million of unrecognized compensation cost related to unvested stock options over a weighted-average period of 2.5 years and $7.9 million of unrecognized compensation cost related to unvested restricted stock over a weighted-average period of 1.7 years.

Warrants

Pursuant to the Term Loan agreement described in Note 6 - Debt, we issued a warrant with an exercise price of $9.76 per share to purchase 23,065 shares of our common stock in 2019. The warrant was fully exercisable and expires in May 2029. As of December 31, 2019, warrants to purchase 165,424 shares of our common stock with a weighted average exercise price of $7.25 per share were outstanding. All outstanding warrants are fully exercisable and expire ten years after issuance.

During the first quarter of 2020, in connection with the Term Loan Agreement further described in Note 6 - Debt, we issued a warrant with an exercise price of $10.42 per share to purchase 21,595 shares of our common stock. The warrant was issued in connection with achieving the interest-only extension milestone 1 in the Term Loan Agreement. The warrant was fully exercisable and expires in January 2030. The $0.2 million fair value of the warrant related to the Term Loan was recorded as interest expense in the period.

In July 2020, OTA LLC, an assignee of Oxford, exercised 51,214 warrants with a strike price of $6.59 per share, 48,892 warrants with a strike price of $6.903 per share, and 25,352 warrants with a strike price of $7.10 per share and elected the cashless settlement method. Accordingly, in July 2020, we issued to OTA LLC a total of 95,932 shares of our common stock.

In October 2020, OTA LLC exercised 13,839 warrants with a strike price of $9.755 per share and elected cashless settlement method. Accordingly, in October 2020, we issued OTA LLC a total of 8,958 shares of our common stock.

As of December 31, 2020, we had outstanding warrants issued pursuant to the Original Loan Agreement and Term Loan Agreement with a weighted average exercise price of $9.12 per share to purchase 47,722 shares of our common stock.

Committed Equity Offering

In 2019, we terminated our original Controlled Equity Offering^SM Sales Agreement (the “ATM Facility”) with Cantor Fitzgerald & Co. (“Cantor”) for the sale, in our sole discretion, of shares of our common stock, having an aggregate offering price of up to $75.0 million through Cantor and we entered into a new sales agreement (the “New ATM Facility”) with Cantor, which provides for the sale, in our sole discretion, of shares of our common stock having an aggregate offering price of up to $85.0 million through Cantor, as our sales agent. The issuance and sale of these shares by us pursuant to the New ATM Facility are deemed “at the market” offerings and are registered under the Securities Act of 1933, as amended. We pay a commission of up to 3.0% of gross sales proceeds of any common stock sold under the New ATM Facility. As of 2019, we issued 3,984,849 shares of common stock for net proceeds of $36.2 million under the New ATM Facility.

Claims Settlement

In the first quarter of 2020, we received $2.2 million from a claims settlement with certain institutional investors that were beneficial owners of our common stock related to the disgorgement of short swing profits pursuant to Section 16(b) of the Securities Exchange Act of 1934, as amended. This settlement was recognized in equity as additional paid-in capital.

Commitments and Contingencies

12 Months Ended

Dec. 31, 2020

Commitments And Contingencies Disclosure [Abstract]

Commitments and Contingencies

Note 9 — Commitments and Contingencies

Leases

Our lease for 280 and 256 East Grand Avenue, South San Francisco, California for our existing facilities expires in 2021 and includes rental payments on a graduated scale and payment of certain operating expenses. As of December 31, 2020, the remaining lease term is 0.5 years and the discount rate used to determine the related operating lease liability was 9.0%.

In July 2019, we amended the lease agreement in connection with our leasing of additional premises at 250 East Grand Avenue, South San Francisco, California (the “Expansion Lease”) for 9,530 square feet of office space. The Expansion Lease has an initial term of 39 months, and commenced in January 2020. As of December 31, 2020, the remaining lease term of the Expansion Lease is 2.3 years and the discount rate used to determine the related operating lease liability was 11.5%.

In July 2019, we entered into a lease agreement for approximately 234,892 square feet of office and laboratory space at a facility located in South San Francisco, California (the “Oyster Point Lease”). The Oyster Point Lease has an initial term of twelve years, and is expected to commence in September 2021 and we have two consecutive five-year options to extend the lease. Subject to rent abatement for the first two months of the Oyster Point Lease, we will be required to pay $5.45 per square foot for 159,891 square feet for the first twelve months of the lease term, which will increase at a rate of 3.5% per year. After the first twelve months of the Oyster Point Lease, rent will be payable on the entire leased square footage. We paid fifty percent of the security deposit amount on December 31, 2019 and the remaining fifty percent was paid in December 2020. The landlord will provide a tenant improvement allowance of $35.3 million for costs relating to the initial design and construction of the improvements. We will pay certain operating costs of the facility and have certain rights to sublease under the related lease agreement. The total commitment of undiscounted lease payments for the Oyster Point Lease was $217.7 million at December 31, 2020.

While we had $9.1 million in construction in progress related to the Oyster Point Lease as of December 31, 2020, the Company has not recognized a right-of-use asset or aggregate lease liability as of December 31, 2020 for the Oyster Point Lease as the underlying assets were unavailable to use by the Company at any time in the period ended December 31, 2020.

The undiscounted future non-cancellable lease payments under the lease agreements as of December 31, 2020 is as follows (in thousands):

Years ending December 31:
2021	$	4,616
2022		12,694
2023		16,194
2024		16,648
2025		17,231
Thereafter		153,689
Total undiscounted future lease payments		221,072
Less: Undiscounted lease payments related to Oyster Point Lease		(217,667	)
Less: Present value adjustments		(180	)
Total lease liability	$	3,225

As of December 31, 2020, future minimum lease payments under noncancelable operating leases were $4.6 million in 2021, $12.7 million in 2022 and $16.2 million in 2023.

Cash paid for amounts included in the measurement of lease liabilities for the years ended December 31, 2020 and 2019 was $6.7 million and $5.0 million, respectively, and was included in net cash provided by operating activities in our consolidated statements of cash flows.

Rent expenses were $5.7 million, $5.1 million and $5.0 million for 2020, 2019 and 2018, respectively.

Income Taxes

12 Months Ended

Dec. 31, 2020

Income Tax Disclosure [Abstract]

Income Taxes

Note 10 — Income Taxes

We did not record an income tax provision in 2020, 2019 and 2018 because we had net taxable losses. Our significant jurisdictions are the United States and California.

The following reconciles the statutory federal income tax rate to our effective tax rate:

	Years Ended December 31,
	2020			2019			2018
Tax at federal statutory tax rate		21	%		21	%		21	%
State tax, net of federal benefits		1	%		3	%		0	%
Change in state effected rates		(2	)%		4	%		(4	)%
Tax credits, net		3	%		3	%		1	%
Change in valuation allowance		(23	)%		(30	)%		(17	)%
Stock-based compensation		1	%		(1	)%		(1	)%
Other		(1	)%		0	%		0	%
Total		0	%		(0	)%		(0	)%

Deferred tax assets, net, reflecting the net tax effect of temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes, were as follows (in thousands):

	As of December 31,
	2020			2019
Deferred tax assets:
Net operating loss carryforwards	$	162,514		$	143,228
Tax credits		71,976			67,892
Liability related to sale of future royalties		36,989			35,213
Reserves and accruals		10,876			8,690
Capitalized R&D		2,370			3,949
Long-term lease liability		718			1,674
Depreciation and amortization		746			722
Other		—			58
Total noncurrent deferred tax assets		286,189			261,426
Deferred tax liabilities:
Accounting method change		(927	)		(2,047	)
Operating lease right-of-use assets		(651	)		(1,484	)
Convertible notes		(9,832	)		(12,011	)
Total noncurrent deferred tax liabilities		(11,410	)		(15,542	)
Less: Valuation allowance		(274,779	)		(245,884	)
Net deferred tax assets	$	—		$	—

Realization of deferred tax assets is dependent upon future earnings, if any, the timing and amount of which are uncertain. Based upon the weight of available evidence, which includes our historical operating performance, reported cumulative net losses since inception, expected future losses, and difficulty in accurately forecasting our future results and an assessment of both positive and negative evidence when determining whether it is more likely than not that deferred tax assets are recoverable, we maintained a full valuation allowance on the net deferred tax assets as of December 31, 2020 and 2019. The valuation allowance increased by $28.9 million in 2020 and increased by $24.8 million in 2019.

At December 31, 2020 federal NOL carryforwards were $662.9 million and apportioned state NOL carryforwards before federal benefits were $317.0 million. If not utilized, federal and state operating loss carryforwards incurred prior to 2018 will begin to expire in various amounts beginning 2022 and 2028, respectively.

At December 31, 2020, tax credits of $68.4 million and $16.6 million for federal and state income tax purposes, respectively consisted of Research and Development Credits and Orphan Drug Credits. If not utilized, the federal carryforwards will expire in various amounts beginning in 2021. California based credit carryforwards do not expire.

In general, under Section 382 of the Internal Revenue Code (“Section 382”), a corporation that undergoes an ‘ownership change’ is subject to limitations on its ability to utilize its pre-change net operating losses and tax credits to offset future taxable income. We do not believe it has experienced an ownership change since 2006, however, a portion of its NOLs and tax credits prior to 2007 will be subject to limitations under Section 382.

Activity related to our gross unrecognized tax benefits were (in thousands):

	Years Ended December 31,
	2020			2019		2018
Balance at the beginning of the year	$	9,922		$	9,475	$	9,365
Decrease related to prior year tax positions		(3	)		—		—
Increase related to current year tax positions		603			447		110
Balance at the end of the year	$	10,522		$	9,922	$	9,475

We are subject to income tax examination for all fiscal years with unutilized NOLs and tax credit carryforwards. Included in the balance of unrecognized tax benefits as of December 31, 2020, 2019 and 2018 are $9.6 million, $9.1 million and $8.6 million of tax benefits, respectively, that, if recognized, would result in adjustments to other tax accounts, primarily deferred taxes.

- Definition

The entire disclosure for income taxes. Disclosures may include net deferred tax liability or asset recognized in an enterprise's statement of financial position, net change during the year in the total valuation allowance, approximate tax effect of each type of temporary difference and carryforward that gives rise to a significant portion of deferred tax liabilities and deferred tax assets, utilization of a tax carryback, and tax uncertainties information.

+ References + Details

Subsequent Events

12 Months Ended

Dec. 31, 2020

Subsequent Events [Abstract]

Subsequent Events

Note 11 — Subsequent Events

In January 2021, we entered into a Second Amendment to the Oyster Point Lease. The Second Amendment increases the tenant improvement allowance by $8.2 million, to cover the construction obligations of the improvements on the Oyster Point Lease. In addition, subject to rent abatement for the two months commencing in October 2021, the base rent for the initial lease term will be increased by $0.1 million per month, commencing in September 2021, to repay the additional tenant improvement allowance to the landlord with interest at a rate of 8%. We will pay certain operating costs of the facility under the amended agreement.

Organization and Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2020

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Organization

Cytokinetics, Incorporated (the “Company”, “we” or “our”) was incorporated under the laws of the state of Delaware on August 5, 1997. We are a late-stage biopharmaceutical company focused on the discovery and development of novel small molecule therapeutics that modulate muscle function for the potential treatment of serious diseases and medical conditions.

Our financial statements contemplate the conduct of our operations in the normal course of business. We have incurred an accumulated deficit of $992.3 million since inception and there can be no assurance that we will attain profitability. We had a net loss of $127.3 million and net cash provided by operations of $8.9 million for the year ended December 31, 2020. Cash, cash equivalents and investments increased to $501.0 million as of December 31, 2020 from $267.8 million as of December 31, 2019. We anticipate that we will have operating losses and net cash outflows in future periods.

We are subject to risks common to late stage biopharmaceutical companies including, but not limited to, development of new drug candidates, dependence on key personnel, and the ability to obtain additional capital as needed to fund our future plans. Our liquidity will be impaired if sufficient additional capital is not available on terms acceptable to us. To date, we have funded operations primarily through sales of our common stock, contract payments under our collaboration agreements, sale of future royalties, debt financing arrangements, government grants and interest income. Until we achieve profitable operations, we intend to continue to fund operations through payments from strategic collaborations, additional sales of equity securities, grants and debt financings. We have never generated revenues from commercial sales of our drugs and may not have drugs to market for at least several years, if ever. Our success is dependent on our ability to enter into new strategic collaborations and/or raise additional capital and to successfully develop and market one or more of our drug candidates. As a result, we may choose to raise additional capital through equity or debt financings to continue to fund operations in the future. We cannot be certain that sufficient funds will be available from such a financing or through a collaborator when required or on satisfactory terms. Additionally, there can be no assurance that our drug candidates will be accepted in the marketplace or that any future products can be developed or manufactured at an acceptable cost. These factors could have a material adverse effect on our future financial results, financial position and cash flows.

Based on the current status of our research and development plans, we believe that our existing cash, cash equivalents and investments will be sufficient to fund our cash requirements for at least the next 12 months after the issuance of the consolidated financial statements. If, at any time, our prospects for financing our research and development programs decline, we may decide to reduce research and development expenses by delaying, discontinuing or reducing our funding of one or more of our research or development programs. Alternatively, we might raise funds through strategic collaborations, public or private financings or other arrangements. Such funding, if needed, may not be available on favorable terms, or at all. The financial statements do not include any adjustments that might result from the outcome of this uncertainty.

Use of Estimates

The preparation of financial statements in conformity with accounting principles generally accepted in the United States requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosures of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.

Basis of Presentation

The consolidated financial statements include the accounts of Cytokinetics, Incorporated and its wholly-owned subsidiary and have been prepared in accordance with U.S. generally accepted accounting principles (“US GAAP”). Intercompany transactions and balances have been eliminated in consolidation. Certain prior period amounts have been reclassified to conform the prior period presentation to the current year.

Concentration of Credit Risk and Other Risks and Uncertainties

Financial instruments that potentially subject us to concentrations of risk consist principally of cash and cash equivalents, investments, and accounts receivable.

Our cash, cash equivalents and investments are invested in deposits with two major financial institutions in the United States. Deposits in these banks may exceed the amount of insurance provided on such deposits.

Our exposure to credit risk associated with non-payment is limited to our strategic partners Amgen Inc. (“Amgen”), Astellas Pharma Inc. (“Astellas”) and Ji Xing Pharmaceuticals Limited (“Ji Xing”) and any material non-payment from our partners would result in a material breach of the agreements underlying our strategic partnerships.

Drug candidates we develop may require approvals or clearances from the U.S. Food and Drug Administration (“FDA”) or other regulatory agencies prior to commercial sales. There can be no assurance that our drug candidates will receive any of the required approvals or clearances. If we were to be denied approval, or clearance or any such approval or clearance was to be delayed, it would have a material adverse impact on us.

Cash and Cash Equivalents

We consider all highly liquid investments with a maturity of three months or less at the time of purchase to be cash equivalents.

Investments

Available-for-sale investments. Our investments consist of U.S. Treasury securities, agency bonds, commercial paper, corporate debt and money market funds. We designate all investments as available-for-sale and report them at fair value, based on quoted market prices, with unrealized gains and losses recorded in accumulated other comprehensive income and loss. The cost of securities sold is based on the specific-identification method. Investments with original maturities greater than three months and remaining maturities of one year or less are classified as short-term investments. Investments with remaining maturities greater than one year are classified as long-term investments. The amortized cost of debt securities in this category is adjusted for amortization of premiums and accretion of discounts to maturity. Such amortization is included in Interest and other income, net. Recognized gains and losses and declines in value judged to be other-than-temporary, if any, on available-for-sale securities are included in Interest and other income, net. Interest and dividends on securities classified as available-for-sale are included in Interest and other income, net.

All of our available-for-sale investments are subject to a periodic impairment review. If an impairment is the result of a credit loss, we recognize an allowance for credit losses (“ACL”). ACL’s reflect management’s current estimate of credit losses that are expected to occur over the remaining life of a financial asset. We recognize an impairment charge when a decline in the fair value of investments below the cost basis is judged to be other-than-temporary. Factors we consider in assessing whether an other-than-temporary impairment has occurred include: the nature of the investment; whether the decline in fair value is attributable to specific adverse conditions affecting the investment; the financial condition of the investee; the severity and the duration of the impairment; and whether we have the intent and ability to hold the investment to maturity. When we determine that an other-than-temporary impairment has occurred, the investment is written down to its market value at the end of the period in which it is determined that an other-than-temporary decline has occurred.

Property and Equipment, net

Property and equipment are stated at cost less accumulated depreciation and are depreciated on a straight-line basis over the estimated useful lives of the related assets, which are generally three years for computer equipment and software, five years for laboratory equipment and office equipment, and seven years for furniture and fixtures. Amortization of leasehold improvements is computed using the straight-line method over the shorter of the remaining lease term or the estimated useful life of the related assets, typically ranging from three to seven years. Upon sale or retirement of assets, the costs and related accumulated depreciation and amortization are removed from the balance sheet and the resulting gain or loss is reflected in operations.

Impairment of Long-lived Assets

We review long-lived assets, including property and equipment, for impairment whenever events or changes in business circumstances indicate that the carrying amount of the assets may not be fully recoverable. Impairment is measured as the amount by which the carrying amount of a long-lived asset exceeds its fair value. We would recognize an impairment loss when estimated undiscounted future cash flows expected to result from the use of the asset and its eventual disposition are materially less than its carrying amount.

Leases

We adopted Accounting Standards Update No. 2016-02, Leases (“Topic 842”) on January 1, 2019 using the modified retrospective approach. In adopting Topic 842, we recognized a right-of-use asset and a short-term and long-term lease liability on our consolidated balance sheets for our existing facilities leases with Britannia Pointe Grand Limited Partnership (the “Britannia Leases”). The right-of-use asset is based on the liability adjusted for any prepaid or deferred rent. We determined the lease term at the commencement date by considering whether renewal options and termination options are reasonably assured of exercise. In determining the present value of lease payments, we estimated our incremental borrowing rate based on information available when we adopted Topic 842. We base the Britannia Leases liability on the present value of remaining lease payments over the remaining terms of the Britannia Leases, using an estimated rate of interest that we would pay to borrow equivalent funds on a collateralized basis at the lease commencement date. We evaluated our other contracts and determined that, except for the Britannia Leases, none of our contracts contained a lease as defined in Topic 842.

We elected the package of practical expedients permitted under the transition guidance within Topic 842, which among other things, allowed us to carry forward the historical lease classification of those leases in place as of January 1, 2019. We also elected to exclude from our consolidated balance sheets recognition of leases having a term of 12 months or less (short-term leases) and elected to not separate lease components and non-lease components for Britannia Leases.

We recorded a lease liability of $10.7 million and a corresponding right-of-use asset of $9.6 million upon adoption of the new lease standard on January 1, 2019.

We recognize rent expense for operating leases on a straight-line basis over the lease term in operating expenses on the consolidated statements of operations.

Prior period amounts continue to be reported in accordance with our historic accounting under previous lease guidance, ASC 840, Leases (“Topic 840”).

Revenue Recognition

We recognize revenue when we transfer promised goods or services to customers in an amount that reflects the consideration for those goods or services. To recognize revenue from a contract with a customer, we:

(i)

identify our contracts with our customers;

(ii)

identify our distinct performance obligations in each contract;

(iii)

determine the transaction price of each contract;

(iv)

allocate the transaction price to the performance obligations; and

(v)

recognize revenue as we satisfy our performance obligations.

At contract inception, we assess the goods or services promised within each contract and assess whether each promised good or service is distinct and determine those that are performance obligations. We then recognize as revenue the amount of the transaction price that is allocated to the respective performance obligation when (or as) the performance obligation is satisfied.

Collaborative Arrangements

We enter into collaborative arrangements with partners that typically include payment to us for one of more of the following: (i) license fees; (ii) milestone payments related to the achievement of developmental, regulatory, or commercial goals; (iii) royalties on net sales of licensed products; and (iv) research and development cost reimbursements. Each of these payments results in collaboration or other revenues. Where a portion of non-refundable up-front fees or other payments received are allocated to continuing performance obligations under the terms of a collaborative arrangement, they are recorded as deferred revenue and recognized as revenue when (or as) the underlying performance obligation is satisfied.

As part of the accounting for these arrangements, we must develop estimates and assumptions that require judgment to determine the underlying stand-alone selling price for each performance obligation which determines how the transaction price is allocated among the performance obligations. The stand-alone selling price may include such items as, forecasted revenues, development timelines, reimbursement rates for personnel costs, discount rates and probabilities of technical and regulatory success, to determine the transaction price to allocate to each performance obligation.

For our collaboration agreements that include more than one performance obligation, such as a license combined with a commitment to perform research and development services, we make judgments to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress for purposes of recognizing revenue from non-refundable, up-front fees. We evaluate our progress each reporting period and, if necessary, adjust the measure of a performance obligation and related revenue recognition.

License Fees: If a license to our intellectual property is determined to be distinct from the other performance obligations identified in the arrangement, we recognize revenues from non-refundable, up-front fees allocated to the license when the license is transferred to the licensee and the licensee is able to use and benefit from the license. For licenses that are bundled with other promises, we utilize judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress for purposes of recognizing revenue from non-refundable, up-front license fees. We evaluate the measure of progress each reporting period and, if necessary, adjust the measure of performance and related revenue recognition.

Milestone Payments: We use judgment to determine whether a milestone is considered probable of being reached. Using the most likely amount method, we include the value of a milestone payment in the consideration for a contract at inception if we then conclude achieving the milestone is more likely than not. Otherwise, we exclude the value of a milestone payment from contract consideration at inception and recognize revenue for a milestone at a later date, when we judge that it is probable the milestone will be achieved. If we conclude it is probable that a significant revenue reversal would not occur, the associated milestone is included in the transaction price. We then allocate the transaction price to each performance obligation on a relative stand-alone selling price basis, for which we recognize revenue as or when the performance obligations under the contract are satisfied. At the end of each subsequent reporting period, we re-evaluate the probability of achievement of such milestones and any related constraint, and if necessary, adjust our estimate of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis, which would affect license, collaboration and other revenues and earnings in the period of adjustment.

Royalties: For contracts that include sales-based royalties, we recognize revenue at the later of (i) when the related sales occur, or (ii) when the performance obligation to which some or all of the royalty has been allocated has been satisfied. To date, we have not recognized any royalty revenues resulting from contracts.

Research and Development Cost Reimbursements: Our joint programs with Astellas under that certain License and Collaboration Agreement for Other Skeletal Sarcomere Activators, dated April 23, 2020, as amended (the “Astellas OSSA Agreement”), and with Amgen under that certain Collaboration and Option Agreement, dated December 29, 2006, as amended (the “Amgen Agreement”), include promises of research and development services. We have determined that these services collectively are distinct from the licenses provided to Astellas and Amgen under such agreements, and as such, these promises are accounted for as a separate performance obligation recorded over time. We recognize revenue for these services as the performance obligations are satisfied, which we estimate using internal research and development costs incurred.

Accrued Research and Development Expenditures

A substantial portion of our preclinical studies and all of our clinical trials have been performed by third-party contract research organizations (“CROs”) and other vendors and our accruals for expenses for preclinical studies and clinical trials may be significant. For preclinical studies, the significant factors used in estimating accruals include the percentage of work completed to date and contract milestones achieved. For clinical trial expenses, the significant factors used in estimating accruals include the number of patients enrolled, duration of enrollment, milestones achieved and percentage of work completed to date. We monitor patient enrollment levels and related activities to the extent practicable through internal reviews, correspondence and status meetings with CROs, and review of contractual terms. We depend on the timeliness and accuracy of data provided by our CROs and other vendors to accrue expenses. If we receive and rely on incomplete or inaccurate data, accruals and expenses may be too high or too low at a given point in time and corresponding adjustments to accruals and expenses would be made in future periods when the actual expense becomes known.

Liability Related to Sale of Future Royalties

We treat our liability to RPI Finance Trust (“RPI”) related to sale of future royalties under that certain Royalty Purchase Agreement, dated February 1, 2017 (the “RPI Royalty Purchase Agreement”) pursuant to which we sold a portion of our right to receive royalties from Amgen on potential net sales of omecamtiv mecarbil as a debt financing, to be amortized under the effective interest rate method over the life of the related royalty stream.

Our liability to RPI related to sale of future royalties under the RPI Royalty Purchase Agreement (the “RPI Liability”) and related amortization are based on our current estimates of future royalties expected to be paid over the life of the arrangement. Concurrently with our entry into the RPI Royalty Purchase Agreement, we entered into a common stock purchase agreement with RPI. We allocated the consideration and issuance costs on a relative fair value basis to the RPI Liability and the common stock.

The RPI Royalty Purchase Agreement further provides that in the event Amgen elects to terminate the Amgen Agreement, we are obliged to enter into an agreement with RPI to preserve RPI’s rights under the RPI Royalty Purchase Agreement, which includes the payment by Cytokinetics of 4.5% of its worldwide net sales of omecamtiv mecarbil and other compounds with the same mechanism of action as omecamtiv mecarbil that are subject to the Amgen Agreement (together the “Amgen Alliance Compounds”), subject to a potential increase of up to an additional 1% under certain circumstances (delay in US marketing approval). Our obligation to enter into a new agreement with RPI does not impact our accounting treatment of the RPI Liability or our estimates.

The RPI Liability will be recognized using significant unobservable inputs. These inputs are derived using internal management estimates developed based on third party data and reflect management’s judgements, current market conditions surrounding competing products, and forecasts. The significant unobservable inputs include the estimated patient population, estimated selling price, estimated peak sales and sales ramp, the expected term of the royalty stream, timing of the expected launch and its impact on the royalty rate. A significant change in unobservable inputs could result in a material increase or decrease to the effective interest rate of the RPI Liability.

We will periodically assess the amount and timing of expected royalty payments using a combination of internal projections and forecasts from external sources. To the extent our future estimates of future royalty payments are greater or less than previous estimates or the estimated timing of such payments is materially different than previous estimates, we will adjust the amortization of the RPI Liability related to sale of future royalties and prospectively recognize the related non-cash interest expense. We have updated the analysis to include the data released on October 8, 2020 relating to GALACTIC-HF. Our estimates regarding the amount and timing of future royalty payments have not changed as a result of Amgen’s election to terminate the Amgen Agreement or Servier’s election to terminate the sublicense agreement (the “Servier Agreement”) between Amgen and Les Laboratoires Servier and Institut de Recherches Internationales Servier (“Servier”) respectively.

We account for the RPI Liability, as a liability primarily because we have significant continuing involvement in generating the royalty stream. If and when omecamtiv mecarbil is commercialized and royalties become due, we will recognize the portion of royalties paid to RPI as a decrease to the RPI Liability and a corresponding reduction in cash.

Research and Development Expenditures

Research and development costs are charged to operations as incurred. Research and development expenses consist primarily of clinical manufacturing costs, preclinical study expenses, consulting and other third-party costs, employee compensation, supplies and materials, allocation of overhead and occupancy costs, facilities costs and depreciation of equipment.

Income Taxes

We account for income taxes under the asset and liability method. Under this method, deferred tax assets and liabilities are determined based on the difference between the financial statement and tax basis of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to affect taxable income. Valuation allowances are established when necessary to reduce deferred tax assets to the amounts expected to be realized.

We recognize uncertain tax positions taken or expected to be taken on a tax return. Tax positions are initially recognized when it is more likely than not that the position will be sustained upon examination by the tax authorities. Such tax positions are initially and subsequently measured as the largest amount of tax benefit that is more likely than not of being realized upon ultimate settlement with the tax authority assuming full knowledge of the position and relevant facts.

We recognize interest accrued related to unrecognized tax benefits and penalties as income tax expense.

In December 2019, the FASB issued ASU 2019-12, Simplifying the Accounting for Income Taxes (“ASU 2019-12”), as part of its Simplification Initiative to reduce the cost and complexity in accounting for income taxes. ASU 2019-12 removes certain exceptions related to the approach for intraperiod tax allocation, the methodology for calculating income taxes in an interim period and the recognition of deferred tax liabilities for outside basis differences. ASU 2019-12 also amends other aspects of Topic 740, Income Taxes, to help simplify and promote consistent application of US GAAP. The guidance is effective for interim and annual periods beginning after December 15, 2020, with early adoption permitted. We early adopted ASU 2019-12 in 2019 and it did not have a material impact on the Consolidated Financial Statements.

The only aspect of ASU 2019-12 that had a material impact on our consolidated financial statements was the removal of the exception related to intraperiod tax allocation. Starting in 2019, we followed the general intraperiod allocation of tax expense. We have a loss from continuing operations and subsequent to the adoption of ASU 2019-12, we determined the amount attributable to continuing operations without regard to the tax effect of other items. We prospectively applied the ASU 2019-12 amendment related to intraperiod tax allocation.

Had the Company not adopted ASU 2019-12, upon issuance of the convertible notes in 2019 (see Note 6 – Debt) a $12.0 million deferred tax benefit would have been recognized along with corresponding decreases to net loss and accumulated deficit. The Company had no intraperiod tax allocation items in prior years.

Due to our net loss position, the income tax benefit generated without the adoption of ASU 2019-12 was a non-cash benefit. The adoption of ASU 2019-12 did not impact our cash flows.

Stock-Based Compensation

We maintain equity incentive plans under which incentive stock options may be granted to employees and nonqualified stock options, restricted stock awards, restricted stock units and stock appreciation rights may be granted to employees, directors, consultants and advisors. In addition, we maintain an employee stock purchase plan (“ESPP”) under which employees may purchase shares of our common stock through payroll deductions.

Stock-based compensation expense related to stock options granted to employees and directors is recognized based on the grant date estimated fair values using the Black Scholes option pricing model. The value of the portion of the award that is ultimately expected to vest is recognized as expense ratably over the requisite service period.

Stock-based compensation expense related to restricted stock units granted to employees is recognized based on the grant-date fair value of each award and recorded as expense over the vesting period using the ratable method.

Stock-based compensation expense related to the ESPP is recognized based on the fair value of each award estimated on the first day of the offering period using the Black Scholes option pricing model and recorded as expense over the service period using the straight-line method.

Amortization of Debt Discount and Issuance Costs

Debt discount and issuance costs, consisting of legal and other fees directly related to the debt as well as the discount created by the bifurcation of the equity component and the debt component of the convertible senior notes due 2026 (the “2026 Notes”), are offset against gross proceeds from the issuance of debt and are amortized to interest expense over the estimated life of the debt based on the effective interest method.

Recent Accounting Pronouncements

Recent Accounting Standards

In June 2016, the Financial Accounting Standards Board (“FASB”) issued ASU 2016-13, ‘Financial Instruments — Credit Losses — Measurement of Credit Losses on Financial Instruments (“ASU 2016-13”), which requires that financial assets measured at amortized cost be presented at the net amount expected to be collected. The measurement of expected credit losses is based on historical experience, current conditions, and reasonable and supportable forecasts that affect collectability. ASU 2016-13 also eliminates the concept of “other-than-temporary” impairment when evaluating available-for-sale debt securities and instead focuses on determining whether any impairment is a result of a credit loss or other factors. An entity will recognize an allowance for credit losses on available-for-sale debt securities rather than an other-than-temporary impairment that reduces the cost basis of the investment. ASU 2016-13 is effective for annual and interim reporting periods beginning after December 15, 2019. We adopted ASU 2016-13 as of January 1, 2020 and the adoption did not have a material impact on the Consolidated Financial Statements.

In August 2018, the FASB issued ASU 2018-15, Intangibles-Goodwill and Other-Internal-Use Software (Subtopic 350-40): Customer's Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract, which expands the scope of costs associated with cloud computing arrangements that must be capitalized. Under the new guidance, costs associated with implementing a cloud computing arrangement that is a service contract must be capitalized and expensed over the term of the hosting arrangement. This guidance should be applied either retrospectively or prospectively to all implementation costs incurred after the date of adoption. We adopted ASU 2018-15 on January 1, 2020 and the adoption did not have a material impact on the Consolidated Financial Statements.

In November 2018, the FASB issued ASU 2018-18, Collaborative Arrangements (Topic 808): Clarifying the Interaction between Topic 808 and Topic 606, Revenue from Contracts with Customers, (“ASU 2018-18”), which makes targeted improvements to clarify the interaction between Topic 808, Collaborative Arrangements, and Topic 606, Revenue from Contracts with Customers. ASU 2018-18 is effective for fiscal years beginning after December 15, 2019, and interim periods within those fiscal years. We adopted ASU 2018-18 on January 1, 2020 and the adoption did not have a material impact on the Consolidated Financial Statements.

In November 2019, the FASB issued ASU 2019-08, Compensation-Stock Compensation (Topic 718) and Revenue from Contracts with Customers (Topic 606): Codification Improvements-Share-Based Consideration Payable to a Customer, which requires that an entity measure and classify share-based payment awards granted to a customer by applying the guidance in Topic 718. The amount recorded as a reduction of the transaction price is required to be measured on the basis of the grant-date fair value of the share-based payment award. We have adopted ASU 2019-08 as of January 1, 2020 and the adoption did not have any impact on the Consolidated Financial Statements.

In March 2020, the FASB issued ASU 2020-04, Reference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting (“ASU 2020-04’). ASU 2020-04 provides optional guidance for a limited period of time to ease the potential burden associated with the expected market transition from the London Inter-Bank Offer Rate ("LIBOR") to alternative reference rates. Companies can apply ASU 2020-04 immediately, however the guidance will only be available until December 31, 2022. The Company’s term loan utilizes LIBOR as the reference rate and we are currently evaluating the impact that adopting this new accounting standard will have on our Consolidated Financial Statements and related disclosures.

In August 2020, the FASB issued ASU 2020-06, Debt-Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging-Contracts in Entity’s Own Equity (Subtopic 815-40): Accounting for Convertible Instruments and Contracts in an Entity’s Own Equity (“ASU 2020-06”). ASU 2020-06 amends the guidance on convertible instruments and the derivatives scope exception for contracts in an entity's own equity, and also improves and amends the related earnings per share guidance. ASU 2020-06 will be effective for annual reporting periods after December 15, 2021 and interim periods within those annual periods and early adoption is permitted. We are currently evaluating the impact that adopting this new accounting standard will have on our Consolidated Financial Statements and related disclosures.

Net Loss Per Share (Tables)

12 Months Ended

Dec. 31, 2020

Earnings Per Share [Abstract]

Instruments Excluded from the Computation of Diluted Net Loss Per Share

The following instruments were excluded from the computation of diluted net loss per share for the periods presented because their effect would have been antidilutive (in thousands):

	Years Ended December 31,
	2020		2019		2018
Options to purchase common stock		8,510		7,759		5,476
Warrants to purchase common stock		48		165		116
Restricted stock and performance units		1,117		839		547
Shares issuable related to the ESPP		12		27		107
Shares issuable upon conversion of convertible notes		16,675		16,675		—
Total shares		26,362		25,465		6,246

Research and Development Arrangements (Tables)

12 Months Ended

Dec. 31, 2020

Research And Development [Abstract]

Schedule of Changes in Contract Assets

Our contract assets changed during the period, as follows (in thousands):

	December 31,
	2020		2019			2018
Contract asset from the 2016 Astellas Amendment
Balance at beginning of period	$	—	$	4,554		$	9,708
Services performed		—		—			11,713
Cash received for services		—		(4,554	)		(16,867	)
Balance at end of period	$	—	$	—		$	4,554

Summary of License Revenues and Research and Development Revenues

License revenues and research and development revenues from Astellas for 2020, 2019 and 2018 were as follows (in thousands):

	Years Ended December 31,
	2020		2019		2018
License revenues	$	—	$	—	$	5,133
Reimbursements		6,555		13,106		22,253
Milestone fees		—		—		2,000
	$	6,555	$	13,106	$	29,386

Schedule of Private Placement

The RTW Transactions were entered into with parties that are affiliated and in contemplation of one another and, accordingly, we have assessed the accounting for these transactions in the aggregate. We concluded that there were three units of accounting in the RTW Transactions as further described below. The Company allocated the total consideration in accordance with ASC 820, Fair Value Measurement, and ASC 606, Revenue from Contracts with Customers, as follows (in thousands):

	Allocated Consideration
Units of Accounting:
License and collaboration (residual)	$	36,501
Royalty (fair value)		87,000
Common stock (fair value)		36,499
Total consideration	$	160,000

Summary of License Revenue and Milestone

License revenues and milestone revenues for 2020, 2019 and 2018 were as follows (in thousands):

	Years Ended December 31,
	2020		2019		2018
License revenues	$	36,501	$	—	$	—
Milestone revenues		2,500		—		-
	$	39,001	$	—	$	—

Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2020

Fair Value Disclosures [Abstract]

Summary of Fair Value of Financial Assets Consists of Cash Equivalents and Investments Classified as Available-for-sale Securities Measured on Recurring Basis

The follow tables set forth the fair value of our financial assets, which consists of cash equivalents and investments classified as available-for-sale securities, that were measured on a recurring basis (in thousands):

	December 31, 2020
	Fair Value Hierarchy Level	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
Money market funds	Level 1	$	80,050	$	—	$	—		$	80,050
U.S. Treasury securities	Level 1		274,407		147		(8	)		274,546
Agency bonds	Level 2		51,581		15		(3	)		51,593
Commercial paper	Level 2		49,500		3		(1	)		49,502
Corporate obligations	Level 2		42,392		7		(11	)		42,388
		$	497,930	$	172	$	(23	)	$	498,079

	December 31, 2019
	Fair Value Hierarchy Level	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
Money market funds	Level 1	$	31,535	$	—	$	—		$	31,535
U.S. Treasury securities	Level 1		134,845		72		(1	)		134,916
Agency bonds	Level 2		47,024		23		(9	)		47,038
Commercial paper	Level 2		10,435		4		—			10,439
Corporate obligations	Level 2		40,426		24		(7	)		40,443
		$	264,265	$	123	$	(17	)	$	264,371

Balance Sheet Components (Tables)

12 Months Ended

Dec. 31, 2020

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Summary of Property and Equipment

Our property and equipment consisted of (in thousands):

	December 31,
	2020			2019
Property and equipment, net:
Laboratory equipment	$	18,160		$	18,741
Computer equipment and software		2,940			2,940
Office equipment, furniture and fixtures		1,885			1,823
Leasehold improvements		5,872			5,221
Construction in progress		9,130			—
Total property and equipment		37,987			28,725
Less: Accumulated depreciation and amortization		(24,641	)		(24,195	)
	$	13,346		$	4,530

Summary of Accrued Liabilities

Our accrued liabilities were (in thousands):

	December 31,
	2020		2019
Accrued liabilities:
Clinical and preclinical costs	$	6,124	$	2,215
Compensation related		11,787		8,343
Other accrued expenses		1,404		1,565
Total accrued liabilities	$	19,315	$	12,123

Debt (Tables)

12 Months Ended

Dec. 31, 2020

Debt Disclosure [Abstract]

Schedule of Future Minimum Payments under Term Loan Agreement

Future minimum payments under the Term Loan Agreement are (in thousands):

Years ending December 31:
2021		3,673
2022		25,330
2023		28,079
Future minimum payments		57,082
Less: Interest and final payment		(12,082	)
Term Loan, gross	$	45,000

Schedule of Interest Cost Relating to 2026 Notes

The following table presents the total amount of interest cost recognized relating to the 2026 Notes for 2020 and 2019 (in thousands):

	Years Ended December 31,
	2020		2019
Contractual interest expense	$	5,520	$	721
Accretion of debt discount		5,246		673
Accretion of debt issuance costs		52		6
Total interest costs recognized	$	10,818	$	1,400

Liability Related to Sale of Future Royalties (Tables)

12 Months Ended

Dec. 31, 2020

Royalty Liability [Abstract]

Schedule of Activity within Liabilities Related to Sale of Future Royalties

Changes to the RPI Liability related to the sale of future royalties are as follows (in thousands):

	2020		2019
Beginning balance, January 1	$	143,276	$	122,473
Interest accretion		22,713		20,737
Amortization of issuance costs		79		66
Ending balance, December 31	$	166,068	$	143,276

Stockholders' Equity (Tables)

12 Months Ended

Dec. 31, 2020

Equity [Abstract]

Summary of Stock Option Activity

Stock option activity in 2020 was as follows:

	Stock Options Outstanding			Weighted Average Exercise Price per Share		Weighted Average Remaining Contractual Life (in years)		Aggregate Intrinsic Value (in millions)
Balance at December 31, 2018		6,454,037		$	8.72
Granted		1,785,673			8.41
Exercised		(126,793	)		7.78
Forfeited		(353,905	)		10.44
Balance at December 31, 2019		7,759,012		$	8.59
Granted		1,944,562			15.59
Exercised		(967,571	)		8.27
Forfeited		(234,054	)		16.06
Balance at December 31, 2020		8,501,949		$	10.02		6.6	$	91.9
Exercisable at December 31, 2020		5,704,396		$	8.91		5.6	$	67.8

Summary of Restricted Stock Unit Activity

Restricted stock unit (“RSU”) activity in 2020 was as follows:

	Number of Restricted Stock Units			Weighted Average Award Date Fair Value per Share
Balance at December 31, 2018		546,500		$	8.53
Granted		607,150			7.14
Released		(266,500	)		8.84
Forfeited		(48,075	)		7.34
Balance at December 31, 2019		839,075		$	7.49
Granted		731,225			14.40
Released		(435,450	)		7.72
Forfeited		(18,208	)		10.37
Balance at December 31, 2020		1,116,642		$	11.88

Fair Value of Share-Based Payments was Estimated on Date of Grant Based on Assumptions

We use the Black-Scholes option pricing model to determine the fair value of stock option grants to employees and directors and employee stock purchase plan shares. The fair value of share-based payments was estimated on the date of grant based on the following assumptions:

Year Ended December

31, 2020

Year Ended December

31, 2019

Year Ended December

31, 2018

Options

ESPP

Options

ESPP

Options

ESPP

Risk-free interest rate

0.42% to 1.8%

0.11% to 1.8%

1.6% to 3.0%

1.8% to 2.4%

2.3% to 3.0%

1.5% to 2.5%

Volatility

74% to 75%

73% to 76%

73% to 74%

Expected term in years

6.5 to 6.6

0.5

6.5

0.6

6.5

0.5

Expected dividend yield

0%

Summary of Stock-Based Compensation Expense

Stock-based compensation expense for 2020 and 2019 was as follows (in thousands):

	Years Ended December 31,
	2020		2019		2018
Research and development	$	6,949	$	4,260	$	5,101
General and administrative		10,671		6,499		4,660
	$	17,620	$	10,759	$	9,761

Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2020

Commitments And Contingencies Disclosure [Abstract]

Schedule of Undiscounted Future Non-cancellable Lease Payments under the Lease Agreements

The undiscounted future non-cancellable lease payments under the lease agreements as of December 31, 2020 is as follows (in thousands):

Years ending December 31:
2021	$	4,616
2022		12,694
2023		16,194
2024		16,648
2025		17,231
Thereafter		153,689
Total undiscounted future lease payments		221,072
Less: Undiscounted lease payments related to Oyster Point Lease		(217,667	)
Less: Present value adjustments		(180	)
Total lease liability	$	3,225

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2020

Income Tax Disclosure [Abstract]

Reconciliation of Statutory Federal Income Tax Rate to Effective Tax Rate

The following reconciles the statutory federal income tax rate to our effective tax rate:

	Years Ended December 31,
	2020			2019			2018
Tax at federal statutory tax rate		21	%		21	%		21	%
State tax, net of federal benefits		1	%		3	%		0	%
Change in state effected rates		(2	)%		4	%		(4	)%
Tax credits, net		3	%		3	%		1	%
Change in valuation allowance		(23	)%		(30	)%		(17	)%
Stock-based compensation		1	%		(1	)%		(1	)%
Other		(1	)%		0	%		0	%
Total		0	%		(0	)%		(0	)%

Summary of Deferred Tax Assets, Net

Deferred tax assets, net, reflecting the net tax effect of temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes, were as follows (in thousands):

	As of December 31,
	2020			2019
Deferred tax assets:
Net operating loss carryforwards	$	162,514		$	143,228
Tax credits		71,976			67,892
Liability related to sale of future royalties		36,989			35,213
Reserves and accruals		10,876			8,690
Capitalized R&D		2,370			3,949
Long-term lease liability		718			1,674
Depreciation and amortization		746			722
Other		—			58
Total noncurrent deferred tax assets		286,189			261,426
Deferred tax liabilities:
Accounting method change		(927	)		(2,047	)
Operating lease right-of-use assets		(651	)		(1,484	)
Convertible notes		(9,832	)		(12,011	)
Total noncurrent deferred tax liabilities		(11,410	)		(15,542	)
Less: Valuation allowance		(274,779	)		(245,884	)
Net deferred tax assets	$	—		$	—

Schedule of Activity Related to our Gross Unrecognized Tax Benefits

Activity related to our gross unrecognized tax benefits were (in thousands):

	Years Ended December 31,
	2020			2019		2018
Balance at the beginning of the year	$	9,922		$	9,475	$	9,365
Decrease related to prior year tax positions		(3	)		—		—
Increase related to current year tax positions		603			447		110
Balance at the end of the year	$	10,522		$	9,922	$	9,475

Organization and Accounting Policies - Additional Information (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2020 USD ($) Financial_Institution Obligation	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Jan. 01, 2019 USD ($)	Feb. 28, 2017
Summary Of Significant Accounting Policies [Line Items]
Accumulated deficit incurred	$ (992,306)	$ (865,016)
Net loss	(127,290)	(121,692)	$ (106,289)
Net cash provided by (used in) operating activities	8,943	(90,907)	$ (101,215)
Cash, cash equivalents and investments	$ 501,000	$ 267,800
Cash requirements term	12 months
Number of major financial institutions \| Financial_Institution	2
Lease, practical expedients, package		true
Operating lease liability	$ 3,225			$ 10,700
Operating lease, right-of-use asset				$ 9,600
Without Adoption of ASU 2019-12 [Member]
Summary Of Significant Accounting Policies [Line Items]
Deferred tax benefit		$ 12,000
Royalty Purchase Agreement [Member] \| Omecamtiv Mecarbil [Member]
Summary Of Significant Accounting Policies [Line Items]
Percent of royalty on net sale	4.50%
Additional percent of royalty on net sale	1.00%
Minimum [Member]
Summary Of Significant Accounting Policies [Line Items]
Number of performance obligation \| Obligation	1
Minimum [Member] \| Royalty Purchase Agreement [Member]
Summary Of Significant Accounting Policies [Line Items]
Percent of royalty on net sale					4.50%
Computer Equipment and Software [Member]
Summary Of Significant Accounting Policies [Line Items]
Property and equipment estimated useful lives	3 years
Laboratory Equipment and Office Equipment [Member]
Summary Of Significant Accounting Policies [Line Items]
Property and equipment estimated useful lives	5 years
Furniture and Fixtures [Member]
Summary Of Significant Accounting Policies [Line Items]
Property and equipment estimated useful lives	7 years
Leasehold Improvements [Member] \| Minimum [Member]
Summary Of Significant Accounting Policies [Line Items]
Property and equipment estimated useful lives	3 years
Leasehold Improvements [Member] \| Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Property and equipment estimated useful lives	7 years

Net Loss Per Share - Instruments Excluded from the Computation of Diluted Net Loss Per Share (Detail) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total shares	26,362	25,465	6,246
Options to Purchase Common Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total shares	8,510	7,759	5,476
Warrants to Purchase Common Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total shares	48	165	116
Restricted Stock and Performance Units [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total shares	1,117	839	547
Shares Issuable Related to the ESSP [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total shares	12	27	107
Shares Issuable Upon Conversion of Convertible Notes [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total shares	16,675	16,675	0

Research and Development Arrangements - Schedule of Changes in Contract Assets and Liabilities (Detail) - 2016 Astellas Agreement [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenue Recognition Multiple Deliverable Arrangements [Line Items]
Balance at beginning of period	$ 0	$ 4,554	$ 9,708
Services performed	0	0	11,713
Cash received for services	0	(4,554)	(16,867)
Balance at end of period	$ 0	$ 0	$ 4,554

Research and Development Arrangements - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands		2 Months Ended	12 Months Ended
	Jul. 14, 2020	Apr. 30, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2016	Jan. 14, 2024
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total revenues			$ 55,828	$ 26,868	$ 31,501
Accounts receivable			4,420	5,163
Amount received as milestone payment			2,500
Long-term deferred revenue			87,000	0
Net proceeds of issuance of common stock			0	36,214	0
License And Collaboration Agreement [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront Payment Received	$ 25,000
Royalty Purchase Agreement [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Sale of interest in future royalties			85,000
Fair Value of Royalty			87,000
Long-term deferred revenue			87,000
Common Stock Purchase Agreement [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Issuance of common stock upon private placement, shares	2,000,000.0
Shares Issued, price per share	$ 25.00
Net proceeds of issuance of common stock	$ 50,000
Excess amount paid over the fair value of the shares	13,500
Fair value of common stock	$ 36,500
Common stock purchase agreement date	Jul. 14, 2020
Funding Agreement [Member] \| Forecast
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Potential milestone receivable							$ 45,000
Maximum [Member] \| License And Collaboration Agreement [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Potential milestone receivable	$ 200,000
Maximum [Member] \| Funding Agreement [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Potential milestone receivable	$ 90,000
Research and Development Revenues [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total revenues			16,527	26,868	26,368
License [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total revenues			36,501	0	5,133
Amgen \| Research And Development Milestone Grant And Other Revenues Net
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total revenues			10,000	13,800	1,900
Amgen \| Research and Development Revenues [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Accounts receivable			1,700	3,300
Astellas [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total revenues			6,555	13,106	29,386
Astellas [Member] \| Accounting Standards Update 2014-09
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Accounts receivable			2,700	1,900
Astellas [Member] \| 2016 Astellas Amendment [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue recognition, Non-refundable upfront amendment fee						$ 35,000
Amount received as milestone payment						15,000
Revenue recognition over performance period						44,200
Allocated consideration						$ 94,200
Astellas [Member] \| 2016 Astellas Amendment [Member] \| Maximum [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Payment of development costs for clinical trials of reldesemtiv		$ 12,000
Astellas [Member] \| License [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total revenues			0	$ 0	$ 5,133
Astellas O S S A Agreement \| 2016 Astellas Amendment [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Research milestone payments			1,000
Astellas O S S A Agreement \| 2016 Astellas Amendment [Member] \| Maximum [Member] \| Commercial Milestones
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Potential amount receivable under collaboration agreement			250,000
Astellas O S S A Agreement \| 2016 Astellas Amendment [Member] \| Minimum [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Potential amount receivable under collaboration agreement			$ 200,000

Research and Development Arrangements - Summary of License Revenues and Research and Development Revenues (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Research And Development Arrangement Contract To Perform For Others [Line Items]
Total revenues	$ 55,828	$ 26,868	$ 31,501
Astellas [Member]
Research And Development Arrangement Contract To Perform For Others [Line Items]
Total revenues	6,555	13,106	29,386
License [Member]
Research And Development Arrangement Contract To Perform For Others [Line Items]
Total revenues	36,501	0	5,133
License [Member] \| Astellas [Member]
Research And Development Arrangement Contract To Perform For Others [Line Items]
Total revenues	0	0	5,133
Reimbursements [Member] \| Astellas [Member]
Research And Development Arrangement Contract To Perform For Others [Line Items]
Total revenues	6,555	13,106	22,253
Milestone Fees [Member] \| Astellas [Member]
Research And Development Arrangement Contract To Perform For Others [Line Items]
Total revenues	$ 0	$ 0	$ 2,000

- Definition

Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 30
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8906-108599

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 40
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e9031-108599

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 41
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e9038-108599

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8933-108599

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
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-Subparagraph (a)
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Reference 6: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
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-Paragraph 4
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Reference 7: http://www.xbrl.org/2003/role/disclosureRef
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Reference 11: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
-Topic 924
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-Paragraph 1
-Subparagraph (SAB Topic 11.L)
-URI http://asc.fasb.org/extlink&oid=6472922&loc=d3e499488-122856

+ Details

Research and Development Arrangements - Schedule of Private Placement (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Allocated Transaction Prices Of Collaborative Arrangements [Line Items]
Total revenues	$ 55,828	$ 26,868	$ 31,501
Collaborative Arrangement [Member]
Allocated Transaction Prices Of Collaborative Arrangements [Line Items]
Total revenues	39,001	$ 0	$ 0
Collaborative Arrangement [Member] \| RTW [Member]
Allocated Transaction Prices Of Collaborative Arrangements [Line Items]
Total consideration	160,000
Collaborative Arrangement [Member] \| RTW [Member] \| Common Stock [Member]
Allocated Transaction Prices Of Collaborative Arrangements [Line Items]
Fair value of common stock	36,499
Collaborative Arrangement [Member] \| RTW [Member] \| License And Collaboration [Member]
Allocated Transaction Prices Of Collaborative Arrangements [Line Items]
Total revenues	36,501
Collaborative Arrangement [Member] \| RTW [Member] \| Royalty [Member]
Allocated Transaction Prices Of Collaborative Arrangements [Line Items]
Fair Value of Royalty	$ 87,000

Research and Development Arrangements - Summary of License Revenue and Milestone (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Research And Development Arrangement Contract To Perform For Others [Line Items]
Total revenues	$ 55,828	$ 26,868	$ 31,501
License [Member]
Research And Development Arrangement Contract To Perform For Others [Line Items]
Total revenues	36,501	0	5,133
Collaborative Arrangement [Member]
Research And Development Arrangement Contract To Perform For Others [Line Items]
Total revenues	39,001	0	0
Collaborative Arrangement [Member] \| License [Member] \| RTW [Member]
Research And Development Arrangement Contract To Perform For Others [Line Items]
Total revenues	36,501	0	0
Collaborative Arrangement [Member] \| Milestone Revenues [Member] \| RTW [Member]
Research And Development Arrangement Contract To Perform For Others [Line Items]
Total revenues	$ 2,500	$ 0	$ 0

- Definition

Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 30
-Subparagraph (a)
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
-Topic 280
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-Paragraph 32
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Reference 5: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
-Topic 280
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Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 4
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-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130543-203045

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 8: http://www.xbrl.org/2003/role/disclosureRef
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Reference 9: http://www.xbrl.org/2003/role/disclosureRef
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Reference 10: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130545-203045

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 11.L)
-URI http://asc.fasb.org/extlink&oid=6472922&loc=d3e499488-122856

+ Details

Fair Value Measurements - Summary of Fair Value of Financial Assets Consists of Cash Equivalents and Investments Classified as Available-for-sale Securities Measured on Recurring Basis (Detail) - Fair Value, Measurements, Recurring [Member] - Cash and Cash Equivalents and Investments [Member] - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	$ 497,930	$ 264,265
Unrealized Gains	172	123
Unrealized Losses	(23)	(17)
Fair Value	498,079	264,371
Money Market Funds [Member] \| Fair Value Measurements Using Level 1 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	80,050	31,535
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	80,050	31,535
U.S. Treasury Securities [Member] \| Fair Value Measurements Using Level 1 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	274,407	134,845
Unrealized Gains	147	72
Unrealized Losses	(8)	(1)
Fair Value	274,546	134,916
Agency Bonds [Member] \| Fair Value Measurements Using Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	51,581	47,024
Unrealized Gains	15	23
Unrealized Losses	(3)	(9)
Fair Value	51,593	47,038
Commercial Paper [Member] \| Fair Value Measurements Using Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	49,500	10,435
Unrealized Gains	3	4
Unrealized Losses	(1)	0
Fair Value	49,502	10,439
Corporate Obligations [Member] \| Fair Value Measurements Using Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	42,392	40,426
Unrealized Gains	7	24
Unrealized Losses	(11)	(7)
Fair Value	$ 42,388	$ 40,443

Fair Value Measurements - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Fair Value Disclosures [Abstract]
Interest Income	$ 5,300,000	$ 4,500,000
Available for sale investments, fair value		1,000,000.0
Available for sale investments, unrealized gain		300,000
Credit losses on debt securities	0	0
Long-term debt, fair value	46,200,000	$ 45,100,000
Convertible debt, fair value	638,700
Fair value of liabilities transferred from level 1 to level 2	0
Fair value of liabilities transferred from level 2 to level 1	0
Fair value of liabilities transferred into level 3	0
Fair value of liabilities transferred from level 3	$ 0

Balance Sheet Components - Summary of Property and Equipment (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Property Plant And Equipment [Line Items]
Total property and equipment	$ 37,987	$ 28,725
Less: Accumulated depreciation and amortization	(24,641)	(24,195)
Total property and equipment, net	13,346	4,530
Laboratory Equipment [Member]
Property Plant And Equipment [Line Items]
Total property and equipment	18,160	18,741
Computer Equipment and Software [Member]
Property Plant And Equipment [Line Items]
Total property and equipment	2,940	2,940
Office Equipment, Furniture and Fixtures [Member]
Property Plant And Equipment [Line Items]
Total property and equipment	1,885	1,823
Leasehold Improvements [Member]
Property Plant And Equipment [Line Items]
Total property and equipment	5,872	5,221
Construction in Progress [Member]
Property Plant And Equipment [Line Items]
Total property and equipment	$ 9,130	$ 0

Balance Sheet Components - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Deferred Costs Capitalized Prepaid And Other Assets Disclosure [Abstract]
Depreciation expense	$ 1.8	$ 1.3
Employer contributions under the plan	$ 0.9	$ 0.6

Balance Sheet Components - Summary of Accrued Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Accrued liabilities:
Clinical and preclinical costs	$ 6,124	$ 2,215
Compensation related	11,787	8,343
Other accrued expenses	1,404	1,565
Total accrued liabilities	$ 19,315	$ 12,123

Debt - Additional Information (Detail)			12 Months Ended
Debt - Additional Information (Detail)	Nov. 13, 2019 USD ($) $ / shares shares	Nov. 07, 2019 $ / shares	Dec. 31, 2020 USD ($) Installment Day	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	May 17, 2019 USD ($)
Debt Instrument [Line Items]
Interest expense			$ 15,963,000	$ 6,623,000	$ 3,797,000
Net proceeds from convertible notes, net of debt discount and issuance costs			0	133,860,000	0
Purchase of capped call options associated with convertible notes			0	13,386,000	0
Cap price of capped call transactions \| $ / shares		$ 14.07
Capped call premium percentage of sale price of common stock		70.00%
Oxford and Silicon Valley Bank [Member] \| Term Loan Agreement [Member]
Debt Instrument [Line Items]
Principal amount of original loan						$ 45,000,000.0
Oxford and Silicon Valley Bank [Member] \| 2019 Term Loan [Member] \| Term Loan Agreement [Member]
Debt Instrument [Line Items]
Principal amount of original loan						$ 42,000,000.0
Interest expense			$ 4,900,000	$ 5,200,000	$ 3,800,000
Stated interest rate on the amounts borrowed under the Agreement			8.05%
Prepayment fee percentage in fiscal year			3.00%
Prepayment fee percentage in year two			2.00%
Prepayment fee percentage in year three			1.00%
Oxford and Silicon Valley Bank [Member] \| 2019 Term Loan [Member] \| Amended Loan Agreement [Member]
Debt Instrument [Line Items]
Loan repayment terms			The borrowing under the Original Loan Agreement was repayable in monthly interest-only payments through November 2019 followed by 35 months of monthly payments of interest and principal.
Number of instalments description			35 months of monthly payments of interest and principal
Number of instalments \| Installment			35
Debt instrument, applicable interest rate for scenario 1			8.05%
Debt instrument, base interest rate for scenario 2			6.81%
Interest rate description			Both borrowings under the Original Loan Agreement and Term Loan bear interest at an annual rate equal to the greater of (a) 8.05% or (b) the sum of 6.81% plus the 30-day U.S. LIBOR rate
Debt instrument, maturity year and month			2023-12
Oxford and Silicon Valley Bank [Member] \| 2019 Term Loan [Member] \| New Loan and Security Agreement [Member]
Debt Instrument [Line Items]
Loan repayment terms			The borrowing under the Term Loan is repayable in monthly interest-only payments through December 31, 2020. The interest-only period was automatically extended until July 1, 2021 as a result of the Company’s initiation of a Phase 2 trial for CK-274 in cardiomyopathy and has been extended through December 31, 2021 as a result of the achievement of positive results in GALACTIC-HF, the trial of omecamtiv mecarbil in chronic heart failure as announced on October 8, 2020. The ultimate interest-only period will be followed by equal monthly payments of principal and interest to the maturity date in December 2023. The ultimate interest-only period will be followed by equal monthly payments of principal and interest to the maturity date in December 2023.
Final payment fee percentage			6.00%
2026 Notes [Member]
Debt Instrument [Line Items]
Principal amount of original loan	$ 138,000,000.0
Number of instalments description			payable semi-annually on May 15 and December 15 of each year, beginning May 15, 2020
Convertible notes, interest rate	4.00%
Convertible notes, maturity date	Nov. 15, 2026
Convertible notes, sinking fund	$ 0
Convertible notes, shares issued \| shares	94.7811
Convertible notes, principal amount	$ 1,000
Convertible notes, initial conversion price \| $ / shares	$ 10.55
Convertible notes, type of equity security issued			common stock
Net proceeds from convertible notes, net of debt discount and issuance costs	$ 133,900,000
Convertible notes, conversion description			The 2026 Notes may be converted at the option of the holder under any of the following circumstances: (1) during any calendar quarter commencing after the calendar quarter ending on March 31, 2020 (and only during such calendar quarter), if the last reported sale price of the Company’s common stock for at least 20 trading days (whether or not consecutive) during a period of 30 consecutive trading days ending on, and including, the last trading day of the immediately preceding calendar quarter exceeds 127.5% of the last reported sale price of the Company’s common stock on November 7, 2019; (2) during the 5 consecutive business days immediately after any 10 consecutive trading day period (such 10 consecutive trading day period, the “measurement period”) if the trading price per $1,000 principal amount of 2026 Notes for each trading day of the measurement period was less than 98% of the product of the last reported sale price per share of the Company’s common stock on such trading day and the conversion rate on such trading day; (3) upon the occurrence of certain corporate events or distributions on the Company’s common stock; (4) if the Company calls the 2026 Notes for redemption; and (5) at any time from, and including, July 15, 2026 until the close of business on the scheduled trading day immediately before the maturity date, November 15, 2026. The Company will settle conversions by paying or delivering, as applicable, cash, shares of the Company’s common stock, or a combination of cash and shares of the Company’s common stock, at the Company’s election, based on the applicable conversion rate.
Convertible notes, redemption description			The 2026 Notes will be redeemable, in whole or in part, at the Company’s option at any time, and from time to time, on or after November 20, 2023 and, in the case of any partial redemption, on or before the 60th scheduled trading day before the maturity date, at a cash redemption price equal to the principal amount of the 2026 Notes to be redeemed, plus accrued and unpaid interest, if any, to, but excluding, the redemption date but only if the last reported sale price per share of the Company’s common stock exceeds 130% of the conversion price on (1) each of at least 20 trading days, whether or not consecutive, during the 30 consecutive trading days ending on, and including, the trading day immediately before the date the Company sends the related redemption notice; and (2) the trading day immediately before the date the Company sends such notice. If a “fundamental change” (as defined in the indenture) occurs, then, subject to certain exceptions, holders may require the Company to repurchase their 2026 Notes at a cash repurchase price equal to the principal amount of the 2026 Notes to be repurchased, plus accrued and unpaid interest, if any, to, but excluding, the fundamental change repurchase date.
Carrying amount of the liability component	$ 84,200,000
Debt instrument interest, discount rate	12.00%
Carrying amount of the equity component	$ 49,500,000
Debt issuance costs	5,000,000.0
Unamortized debt issuance cost			$ 2,800,000
Debt instrument, unamortized discount			$ 45,700,000
Unamortized debt discount amortization period			6 years
2026 Notes [Member] \| Equity [Member]
Debt Instrument [Line Items]
Debt issuance costs	1,900,000
2026 Notes [Member] \| Liability [Member]
Debt Instrument [Line Items]
Debt issuance costs	$ 3,100,000
Debt instrument effective interest rate			12.50%
2026 Notes [Member] \| Debt Instrument Convertible Covenant One [Member]
Debt Instrument [Line Items]
Convertible notes, percentage of conversion price			127.50%
Convertible notes, trading days \| Day			20
Convertible notes, consecutive trading days \| Day			30
2026 Notes [Member] \| Debt Instrument Convertible Covenant Two [Member]
Debt Instrument [Line Items]
Convertible notes, percentage of last reported sale price of common stock			98.00%
Convertible notes, trading days \| Day			5
Convertible notes, consecutive trading days \| Day			10

Debt - Schedule of Future Minimum Payments under Term Loan Agreement (Detail) - Term Loan Agreement [Member] - Oxford and Silicon Valley Bank [Member] $ in Thousands	Dec. 31, 2020 USD ($)
Debt Instrument [Line Items]
2021	$ 3,673
2022	25,330
2023	28,079
Future minimum payments	57,082
Long-term debt, alternative
Future minimum payments	57,082
Less: Interest and final payment	(12,082)
Term Loan, gross	$ 45,000

Debt - Schedule of Interest Cost Relating to 2026 Notes (Detail) - 2026 Notes [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Contractual interest expense	$ 5,520	$ 721
Accretion of debt discount	5,246	673
Accretion of debt issuance costs	52	6
Total interest costs recognized	$ 10,818	$ 1,400

Liability Related to Sale of Future Royalties to RPI - Additional Information (Detail) - USD ($) $ in Thousands	1 Months Ended
	Feb. 28, 2017	Dec. 31, 2020	Dec. 31, 2019
Liability Related to Sale of Future Royalties [Line Items]
Purchase of common stock shares		71,015,183	59,172,124
Liabilities		$ 420,420	$ 300,751
Royalty Purchase Agreement [Member]
Liability Related to Sale of Future Royalties [Line Items]
Cash payment under royalty agreement	$ 90,000
Purchase of common stock shares	875,656
Stock issued during period, value, issued for services	$ 10,000
Liabilities	$ 92,300
Imputed rate of interest on unamortized liability		15.00%	17.00%
Royalty Purchase Agreement [Member] \| Minimum [Member]
Liability Related to Sale of Future Royalties [Line Items]
Percent of royalty on net sale	4.50%
Royalty Purchase Agreement [Member] \| Maximum [Member]
Liability Related to Sale of Future Royalties [Line Items]
Additional percent of royalty on net sale	1.00%

Liability Related to Sale of Future Royalties to RPI - Schedule Represents Allocation of Transaction Consideration on a Relative Fair Value Basis to the Liability and the Common Stock (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Royalty Liability [Abstract]
Liability related to sale of future royalties beginning balance	$ 143,276	$ 122,473
Interest accretion	22,713	20,737
Amortization of issuance costs	79	66
Liability related to sale of future royalties ending balance	$ 166,068	$ 143,276

Stockholders' Equity - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands		1 Months Ended			3 Months Ended	12 Months Ended
	Jul. 14, 2020	Oct. 31, 2020	Jul. 31, 2020	May 31, 2020	Mar. 31, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Net proceeds of issuance of common stock						$ 0	$ 36,214	$ 0
Intrinsic value of stock options outstanding						91,900
Non-cash stock-based compensation expense						$ 17,620	$ 10,759	9,761
Warrants outstanding to purchase upon exercise of common stock						23,065
Warrants exercise price						$ 9.76
Warrants expiration date						2029-05
Outstanding warrants						165,424
Outstanding warrants, weighted average exercise price						$ 7.25
Expiry period of warrants after date of issuance						10 years
Common stock, shares issued						71,015,183	59,172,124
Commision of gross sales proceeds						3.00%
Claims settlement					$ 2,200	$ 2,151	$ 0	0
OTA LLC [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock, shares issued		8,958	95,932
Warrant 1 [Member] \| OTA LLC [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Warrants exercise price		$ 9.755	$ 6.59
Exercise of stock options, shares		13,839	51,214
Warrant 2 [Member] \| OTA LLC [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Warrants exercise price			$ 6.903
Exercise of stock options, shares			48,892
Warrant 3 [Member] \| OTA LLC [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Warrants exercise price			$ 7.10
Exercise of stock options, shares			25,352
New ATM Facility [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Net proceeds of issuance of common stock							$ 36,200
Common stock, shares issued							3,984,849
Oxford and Silicon Valley Bank [Member] \| New Loan and Security Agreement [Member] \| 2019 Term Loan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Warrants outstanding to purchase upon exercise of common stock						21,595
Warrants exercise price						$ 10.42
Warrants expiration date						2030-01
Outstanding warrants						47,722
Outstanding warrants, weighted average exercise price						$ 9.12
Amortization of discount on debt						$ 200
Maximum [Member] \| ATM Facility [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock offering price						75,000
Maximum [Member] \| New ATM Facility [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock offering price						85,000
Restricted Stock Units (RSUs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share based compensation, vested restricted stock units, total fair value						6,100
Unrecognized compensation cost						$ 7,900
Weighted-average period						1 year 8 months 12 days
Restricted Stock Units (RSUs) \| Minimum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period						2 years
Restricted Stock Units (RSUs) \| Maximum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period						3 years
Options [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation cost						$ 22,200
Weighted-average period						2 years 6 months
2004 Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Option grant prices as percentage of the fair market value of the common stock						100.00%
Term to grant nonstatutory stock options and incentive stock options						10 years
Percentage of options grant to new employees						25.00%
Shares of common stock reserved for issuance						2,600,000
Shares of common stock available for issuance						2,600,000
Number of authorized shares reserved for issuance				800,000		4,100,000
Share based compensation, options exercised, total intrinsic value						$ 14,000	$ 500	$ 700
Intrinsic value of stock options outstanding						$ 91,900
2004 Plan [Member] \| New Employee [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Award vesting right						Options granted to new employees generally vest 25% after one year and monthly thereafter over a period of four years
Period from percentage of stock option vested						1 year
Vesting period						4 years
2004 Plan [Member] \| Existing Employee [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Award vesting right						Options granted to existing employees generally vest monthly over a period of four years.
Vesting period						4 years
ESPP [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Option grant prices as percentage of the fair market value of the common stock						85.00%
Shares of common stock reserved for issuance						446,820
Increase in common stock shares reserved for issuance				500,000
Issuance of common stock pursuant to ESPP, shares						11,565	172,113	144,822
Issuance of common stock pursuant to ESPP, per share						$ 14.64	$ 6.43	$ 6.40
Non-employee Stock-Based Compensation [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Non-cash stock-based compensation expense						$ 200	$ 200	$ 100
Underwritten Public Offering [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Sales of common stock, number of shared issued			8,400,000
Sale of stock, price per share			$ 24.00
Common stock, shares issued			1,093,750
Gross proceeds, consideration received on transaction			$ 201,300
Net proceeds, consideration received on transaction			$ 188,900
Common Stock Purchase Agreement [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Issuance of common stock upon private placement, shares	2,000,000.0
Shares issued, price per share	$ 25.00
Net proceeds of issuance of common stock	$ 50,000
Cash adjusted for the calculated premium	$ 36,500

Stockholders' Equity - Summary of Stock Option Activity (Detail) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock Options Outstanding, Beginning Balance	7,759,012	6,454,037
Stock Options Outstanding, Granted	1,944,562	1,785,673
Stock Options Outstanding, Forfeited	(234,054)	(353,905)
Stock Options Outstanding, Ending Balance	8,501,949	7,759,012
Stock Options Outstanding, Exercisable	5,704,396
Weighted Average Exercise Price per Share, Beginning Balance	$ 8.59	$ 8.72
Weighted Average Exercise Price per Share, Granted	15.59	8.41
Weighted Average Exercise Price per Share, Exercised	8.27	7.78
Weighted Average Exercise Price per Share, Forfeited	16.06	10.44
Weighted Average Exercise Price per Share, Ending Balance	10.02	$ 8.59
Weighted Average Exercise Price per Share, Exercisable	$ 8.91
Weighted Average Remaining Contractual Life	6 years 7 months 6 days
Weighted Average Remaining Contractual Life, Exercisable at December 31, 2019	5 years 7 months 6 days
Aggregate Intrinsic Value	$ 91.9
Aggregate Intrinsic Value, Exercisable at December 31, 2019	$ 67.8
Common Stock [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock Options Outstanding, Exercised	(967,571)	(126,793)

Stockholders' Equity - Summary of Restricted Stock Unit Activity (Detail) - Restricted Stock Units (RSUs) - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Restricted Stock Units, Beginning Balance	839,075	546,500
Number of Restricted Stock Units, Granted	731,225	607,150
Number of Restricted Stock Units, Released	(435,450)	(266,500)
Number of Restricted Stock Units, Forfeited	(18,208)	(48,075)
Number of Restricted Stock Units, Ending Balance	1,116,642	839,075
Weighted Average Award Date Fair Value per Share, Beginning Balance	$ 7.49	$ 8.53
Weighted Average Award Date Fair Value per Share, Granted	14.40	7.14
Weighted Average Award Date Fair Value per Share, Released	7.72	8.84
Weighted Average Award Date Fair Value per Share, Forfeited	10.37	7.34
Weighted Average Award Date Fair Value per Share, Ending Balance	$ 11.88	$ 7.49

Stockholders' Equity - Fair Value of Share-Based Payments was Estimated on Date of Grant Based on Assumptions (Detail)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Options [Member]
Deferred Compensation Arrangement With Individual Share Based Payments [Line Items]
Risk-free interest rate, minimum	0.42%	1.60%	2.30%
Risk-free interest rate, maximum	1.80%	3.00%	3.00%
Volatility, minimum	74.00%	73.00%	73.00%
Volatility, maximum	75.00%	76.00%	74.00%
Expected term in years		6 years 6 months	6 years 6 months
Expected dividend yield	0.00%	0.00%	0.00%
Minimum [Member] \| Options [Member]
Deferred Compensation Arrangement With Individual Share Based Payments [Line Items]
Expected term in years	6 years 6 months
Maximum [Member] \| Options [Member]
Deferred Compensation Arrangement With Individual Share Based Payments [Line Items]
Expected term in years	6 years 7 months 6 days
ESPP [Member]
Deferred Compensation Arrangement With Individual Share Based Payments [Line Items]
Risk-free interest rate, minimum	0.11%	1.80%	1.50%
Risk-free interest rate, maximum	1.80%	2.40%	2.50%
Volatility, minimum	74.00%	73.00%	73.00%
Volatility, maximum	75.00%	76.00%	74.00%
Expected term in years	6 months	7 months 6 days	6 months
Expected dividend yield	0.00%	0.00%	0.00%

Stockholders' Equity - Summary of Stock-Based Compensation Expense (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	$ 17,620	$ 10,759	$ 9,761
Research and Development [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	6,949	4,260	5,101
General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	$ 10,671	$ 6,499	$ 4,660

Commitments and Contingencies - Additional Information (Detail) $ in Thousands	1 Months Ended	12 Months Ended
	Jul. 31, 2019 USD ($) ft² USD_per_sqft	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Lessee Lease Description [Line Items]
Lease expiration year		2021
Weighted average remaining lease term		6 months
Weighted average discount rate		9.00%
Future minimum lease payments under noncancelable operating leases in 2021		$ 4,616
Future minimum lease payments under noncancelable operating leases in 2022		12,694
Future minimum lease payments under noncancelable operating leases in 2023		16,194
Cash paid included in net cash used in operating activities		6,700	$ 5,000
Rent expense		$ 5,700	$ 5,100	$ 5,000
Expansion Lease [Member]
Lessee Lease Description [Line Items]
Weighted average remaining lease term		2 years 3 months 18 days
Weighted average discount rate		11.50%
Area of land under lease agreement \| ft²	9,530
Initial lease term	39 months
Operating lease commencement period	2020-01
Oyster Point Lease [Member] \| California [Member]
Lessee Lease Description [Line Items]
Area of land under lease agreement \| ft²	234,892
Initial lease term	12 years
Operating lease commencement period	2021-09
Operating lease, term description	we have two
Rent payment required to be pay for lease per square foot \| USD_per_sqft	5.45
Area of land \| ft²	159,891
Increase in operating lease rate annual payment	3.50%
Percentage of lease security deposit		50.00%	50.00%
Lease agreement allowances for tenant improvements	$ 35,300
Undiscounted lease payments		$ 217,700
Construction in progress		$ 9,100

Commitments and Contingencies - Schedule of Undiscounted Future Non-cancellable Lease Payments under the Lease Agreements (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Jan. 01, 2019
Leases [Abstract]
2021	$ 4,616
2022	12,694
2023	16,194
2024	16,648
2025	17,231
Thereafter	153,689
Total undiscounted future lease payments	221,072
Less: Undiscounted lease payments related to Oyster Point Lease	(217,667)
Less: Present value adjustments	(180)
Total lease liability	$ 3,225	$ 10,700

Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Contingency [Line Items]
Provision for income tax	$ 0	$ 0	$ 0
Increase (decrease) in valuation allowance	$ 28,900,000	24,800,000
Research and development credits and orphan drug credits, federal carryforwards will expire	2021
Unrecognized tax benefits	$ 9,600,000	$ 9,100,000	$ 8,600,000
Federal Tax [Member]
Income Tax Contingency [Line Items]
Net operating loss carryforwards	$ 662,900,000
Net operating loss carryforwards expiration	2022
Credit carryforwards for federal and state	$ 68,400,000
Federal and State Tax [Member]
Income Tax Contingency [Line Items]
Net operating loss carryforwards	$ 317,000,000.0
Net operating loss carryforwards expiration	2028
Credit carryforwards for federal and state	$ 16,600,000

Income Taxes - Reconciliation of Statutory Federal Income Tax Rate to Effective Tax Rate (Detail)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Tax at federal statutory tax rate	21.00%	21.00%	21.00%
State tax, net of federal benefits	1.00%	3.00%	0.00%
Change in state effected rates	(2.00%)	4.00%	(4.00%)
Tax credits, net	3.00%	3.00%	1.00%
Change in valuation allowance	(23.00%)	(30.00%)	(17.00%)
Stock-based compensation	1.00%	(1.00%)	(1.00%)
Other	(1.00%)	0.00%	0.00%
Total	0.00%	0.00%	0.00%

Income Taxes - Summary of Deferred Tax Assets, Net (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Deferred tax assets:
Net operating loss carryforwards	$ 162,514	$ 143,228
Tax credits	71,976	67,892
Liability related to sale of future royalties	36,989	35,213
Reserves and accruals	10,876	8,690
Capitalized R&D	2,370	3,949
Long-term lease liability	718	1,674
Depreciation and amortization	746	722
Other	0	58
Total noncurrent deferred tax assets	286,189	261,426
Deferred tax liabilities:
Accounting method change	(927)	(2,047)
Operating lease right-of-use assets	(651)	(1,484)
Convertible notes	(9,832)	(12,011)
Total noncurrent deferred tax liabilities	(11,410)	(15,542)
Less: Valuation allowance	(274,779)	(245,884)
Net deferred tax assets	$ 0	$ 0

Income Taxes - Schedule of Activity Related to our Gross Unrecognized Tax Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Balance at the beginning of the year	$ 9,922	$ 9,475	$ 9,365
Decrease related to prior year tax positions	(3)	0	0
Increase related to current year tax positions	603	447	110
Balance at the end of the year	$ 10,522	$ 9,922	$ 9,475

Subsequent Events - Additional Information (Detail) - Expansion Lease [Member] - CALIFORNIA $ in Millions	Jan. 31, 2021 USD ($)
Subsequent Event [Line Items]
Additional lease agreement allowances for tenant improvements	$ 8.2
Base rent increase during initial lease term	$ 0.1
Commencement date for base rent increments during initial lease term	Sep. 30, 2021
Interet rate for repayment of additional tenant improvement allowances	8.00%
Commencement date of rent abatement	2021-10