Cover Page - shares	9 Months Ended
Cover Page - shares	Sep. 30, 2023	Oct. 26, 2023
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2023
Document Transition Report	false
Entity File Number	001-35676
Entity Registrant Name	PROTHENA CORPORATION PUBLIC LIMITED COMPANY
Entity Incorporation, State or Country Code	L2
Entity Tax Identification Number	98-1111119
Entity Address, Address Line One	77 Sir John Rogerson’s Quay, Block C
Entity Address, Address Line Two	Grand Canal Docklands
Entity Address, City or Town	Dublin 2,
Entity Address, Postal Zip Code	D02 VK60,
Entity Address, Country	IE
Country Region	353
City Area Code	1
Local Phone Number	236-2500
Title of 12(b) Security	Ordinary Shares, par value $0.01 per share
Trading Symbol	PRTA
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		53,665,349
Amendment Flag	false
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	Q3
Entity Central Index Key	0001559053
Current Fiscal Year End Date	--12-31

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Current assets:
Cash and cash equivalents	$ 670,897	$ 710,406
Accounts Receivable	5,159	0
Prepaid expenses and other current assets	13,196	8,692
Restricted cash, current	1,352	0
Total current assets	690,604	719,098
Non-current assets:
Property and equipment, net	2,433	1,731
Operating lease right-of-use assets	12,629	6,277
Deferred tax assets	29,916	18,204
Restricted cash, non-current	860	2,212
Other non-current assets	10,478	10,513
Total non-current assets	56,316	38,937
Total assets	746,920	758,035
Current liabilities:
Accounts payable	19,458	9,270
Accrued research and development	18,003	10,794
Deferred revenue, current	316	11,442
Lease liability, current	1,817	6,473
Other current liabilities	13,776	12,168
Total current liabilities	53,370	50,147
Non-current liabilities:
Deferred revenue, non-current	67,405	85,293
Operating Lease, Liability, Noncurrent	8,918	0
Other liabilities	0	553
Total non-current liabilities	76,323	85,846
Total liabilities	129,693	135,993
Commitments and contingencies (Note 6)
Shareholders’ equity:
Euro deferred shares, €22 nominal value: Authorized shares — 10,000 at September 30, 2023 and December 31, 2022. Issued and outstanding shares — none at September 30, 2023 and December 31, 2022.	0	0
Ordinary shares, $0.01 par value: Authorized shares — 100,000,000 at September 30, 2023 and December 31, 2022. Issued and outstanding shares — 53,638,615 and 52,103,608 at September 30, 2023 and December 31, 2022, respectively	536	521
Additional paid-in capital	1,529,246	1,454,524
Accumulated deficit	(912,555)	(833,003)
Total shareholders’ equity	617,227	622,042
Total liabilities and shareholders’ equity	$ 746,920	$ 758,035

Condensed Consolidated Balance Sheets (Parenthetical)	Sep. 30, 2023 € / shares shares	Sep. 30, 2023 $ / shares shares	Dec. 31, 2022 € / shares shares	Dec. 31, 2022 $ / shares shares
Shareholders’ equity:
Euro deferred shares, nominal value (in euros per share) \| € / shares	€ 22		€ 22
Euro deferred shares, number of shares authorized (in shares)	10,000	10,000	10,000	10,000
Euro deferred shares, number of issued shares (in shares)	0	0	0	0
Euro deferred shares, number of outstanding shares (in shares)	0	0	0	0
Ordinary shares, par value (in dollars per share) \| $ / shares		$ 0.01		$ 0.01
Ordinary shares, number of authorized shares (in shares)	100,000,000	100,000,000	100,000,000	100,000,000
Ordinary shares, number of issued shares (in shares)	53,638,615	53,638,615	52,103,608	52,103,608
Ordinary shares, number of outstanding shares (in shares)	53,638,615	53,638,615	52,103,608	52,103,608

Condensed Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Total revenue	$ 84,866	$ 1,517	$ 91,054	$ 3,982
Operating expenses:
Research and development	57,913	39,860	158,680	98,691
General and administrative	16,645	11,989	44,895	36,776
Total operating expenses	74,558	51,849	203,575	135,467
Income (loss) from operations	10,308	(50,332)	(112,521)	(131,485)
Other income (expense):
Interest income	8,522	1,913	22,912	2,605
Other income (expense), net	(15)	2	(253)	(70)
Total other income, net	8,507	1,915	22,659	2,535
Income (loss) before income taxes	18,815	(48,417)	(89,862)	(128,950)
Benefit from income taxes	(3,092)	(2,653)	(10,310)	(5,652)
Net income (loss)	$ 21,907	$ (45,764)	$ (79,552)	$ (123,298)
Basic (in dollars per share)	$ 0.41	$ (0.97)	$ (1.50)	$ (2.63)
Diluted (in dollars per share)	$ 0.38	$ (0.97)	$ (1.50)	$ (2.63)
Weighted-average ordinary shares outstanding used in per share calculations- basic (in shares)	53,559	46,986	53,064	46,833
Weighted-average ordinary shares outstanding used in per share calculations- diluted (in shares)	58,004	46,986	53,064	46,833
Collaboration revenue
Total revenue	$ 84,866	$ 1,517	$ 91,004	$ 3,932
Revenue from license and intellectual property
Total revenue	$ 0	$ 0	$ 50	$ 50

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Operating activities
Net loss	$ 21,907	$ (45,764)	$ (79,552)	$ (123,298)
Adjustments to reconcile net loss to cash used in operating activities:
Depreciation			652	548
Share-based compensation	10,944	7,966	29,834	23,889
Deferred income taxes			(11,712)	(7,903)
Reduction in the carrying amount of right-of-use assets			5,221	4,466
Changes in operating assets and liabilities:
Accounts receivable			(5,159)	0
Prepaid and other assets			(6,824)	(4,997)
Accounts payable, accruals and other liabilities			18,496	11,826
Deferred revenue			(29,014)	(3,933)
Operating lease liabilities			(4,810)	(4,443)
Net cash used in operating activities			(82,868)	(103,845)
Investing activities
Purchases of property and equipment			(1,261)	(313)
Net cash used in investing activities			(1,261)	(313)
Financing activities
Proceeds from issuance of ordinary shares upon exercise of stock options			20,972	6,210
Net cash provided by financing activities			44,620	20,692
Net decrease in cash, cash equivalents and restricted cash			(39,509)	(83,466)
Cash, cash equivalents and restricted cash, beginning of the year			712,618	580,446
Cash, cash equivalents and restricted cash, end of the period	673,109	496,980	673,109	496,980
Supplemental disclosures of cash flow information
Cash paid for income taxes			384	2,374
Supplemental disclosures of non-cash investing and financing activities
Receivable from option exercises			0	3,267
Acquisition of property and equipment included in accounts payable and accrued liabilities			93	220
Right-of-use assets obtained in exchange for lease obligations			3,810	151
Reclassification of prepaid lease payments to right-of-use assets upon lease commencement			7,522	0
Receivable from at-the-market offering			0	13,744
Cash and cash equivalents	670,897	495,628	670,897	495,628
Restricted cash, current	1,352	0	1,352	0
Restricted cash, non-current	860	1,352	860	1,352
Total cash, cash equivalents and restricted cash, end of the period	$ 673,109	$ 496,980	673,109	496,980
Public Offering
Financing activities
Proceeds from issuance of ordinary shares in public offering, net			20,689	0
At-The-Market Offering
Financing activities
Proceeds from issuance of ordinary shares in at-the market offering, net			2,959	14,482
Supplemental disclosures of non-cash investing and financing activities
At-the market offering costs included in accounts payable and accrued liabilities			$ 8	$ 15

Condensed Consolidated Statements of Shareholders' Equity - USD ($) $ in Thousands	Total	Public Offering	At-The-Market Offering	Ordinary Shares	Ordinary Shares Public Offering	Ordinary Shares At-The-Market Offering	Additional Paid-in Capital	Additional Paid-in Capital Public Offering	Additional Paid-in Capital At-The-Market Offering	Accumulated Deficit
Beginning balance (in shares) at Dec. 31, 2021				46,660,294
Beginning balance at Dec. 31, 2021	$ 466,042			$ 466			$ 1,181,630			$ (716,054)
Share-based compensation	7,660						7,660
Issuance of ordinary shares upon exercise of stock options (in shares)				89,472
Issuance of ordinary shares upon exercise of stock options	1,475			$ 1			1,474
Net income (loss)	(36,290)									(36,290)
Ending balance (in shares) at Mar. 31, 2022				46,749,766
Ending balance at Mar. 31, 2022	438,887			$ 467			1,190,764			(752,344)
Beginning balance (in shares) at Dec. 31, 2021				46,660,294
Beginning balance at Dec. 31, 2021	466,042			$ 466			1,181,630			(716,054)
Net income (loss)	(123,298)
Ending balance (in shares) at Sep. 30, 2022				47,885,755
Ending balance at Sep. 30, 2022	404,648			$ 479			1,243,521			(839,352)
Beginning balance (in shares) at Mar. 31, 2022				46,749,766
Beginning balance at Mar. 31, 2022	438,887			$ 467			1,190,764			(752,344)
Share-based compensation	8,263						8,263
Issuance of ordinary shares upon exercise of stock options (in shares)				34,659
Issuance of ordinary shares upon exercise of stock options	427			$ 1			426
Issuance of ordinary shares (in shares)						25,416
Issuance of ordinary shares, net of issuance costs			$ 966						$ 966
Net income (loss)	(41,244)									(41,244)
Ending balance (in shares) at Jun. 30, 2022				46,809,841
Ending balance at Jun. 30, 2022	407,299			$ 468			1,200,419			(793,588)
Stock Issuance Costs			(31)
Share-based compensation	7,966						7,966
Issuance of ordinary shares upon exercise of stock options (in shares)				587,301
Issuance of ordinary shares upon exercise of stock options	7,562			$ 6			7,556
Issuance of ordinary shares (in shares)						488,613
Issuance of ordinary shares, net of issuance costs			27,585			$ 5			27,580
Net income (loss)	(45,764)									(45,764)
Ending balance (in shares) at Sep. 30, 2022				47,885,755
Ending balance at Sep. 30, 2022	404,648			$ 479			1,243,521			(839,352)
Stock Issuance Costs			(899)
Beginning balance (in shares) at Dec. 31, 2022				52,103,608
Beginning balance at Dec. 31, 2022	622,042			$ 521			1,454,524			(833,003)
Share-based compensation	8,790						8,790
Issuance of ordinary shares upon exercise of stock options (in shares)				179,474
Issuance of ordinary shares upon exercise of stock options	2,540			$ 2			2,538
Issuance of ordinary shares (in shares)					395,096
Issuance of ordinary shares, net of issuance costs		$ 20,901			$ 4			$ 20,897
Net income (loss)	(46,864)									(46,864)
Ending balance (in shares) at Mar. 31, 2023				52,678,178
Ending balance at Mar. 31, 2023	607,409			$ 527			1,486,749			(879,867)
Stock Issuance Costs		(1,400)
Beginning balance (in shares) at Dec. 31, 2022				52,103,608
Beginning balance at Dec. 31, 2022	$ 622,042			$ 521			1,454,524			(833,003)
Issuance of ordinary shares upon exercise of stock options (in shares)	1,097,550
Net income (loss)	$ (79,552)
Ending balance (in shares) at Sep. 30, 2023				53,638,615
Ending balance at Sep. 30, 2023	617,227			$ 536			1,529,246			(912,555)
Beginning balance (in shares) at Mar. 31, 2023				52,678,178
Beginning balance at Mar. 31, 2023	607,409			$ 527			1,486,749			(879,867)
Share-based compensation	10,100						10,100
Issuance of ordinary shares upon exercise of stock options (in shares)				772,928
Issuance of ordinary shares upon exercise of stock options	15,659			$ 8			15,651
Issuance of ordinary shares (in shares)						42,361
Issuance of ordinary shares, net of issuance costs			3,104						3,104
Adjustment related to December 2022 public offering		$ 2						$ 2
Net income (loss)	(54,595)									(54,595)
Ending balance (in shares) at Jun. 30, 2023				53,493,467
Ending balance at Jun. 30, 2023	581,679			$ 535			1,515,606			(934,462)
Stock Issuance Costs			(119)
Share-based compensation	10,944						10,944
Issuance of ordinary shares upon exercise of stock options (in shares)				145,148
Issuance of ordinary shares upon exercise of stock options	2,711			$ 1			2,710
Adjustment related to the at-the-market offering program			$ (14)						$ (14)
Net income (loss)	21,907									21,907
Ending balance (in shares) at Sep. 30, 2023				53,638,615
Ending balance at Sep. 30, 2023	$ 617,227			$ 536			$ 1,529,246			$ (912,555)

Condensed Consolidated Statements of Shareholders' Equity (Parenthetical) - USD ($) $ in Thousands	3 Months Ended
	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2022	Jun. 30, 2022
At-The-Market Offering
Stock Issuance Costs	$ (119)		$ (899)	$ (31)
Public Offering
Stock Issuance Costs		$ (1,400)

Organization	9 Months Ended
Organization	Sep. 30, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization	Organization Description of Business Prothena Corporation plc (“Prothena” or the “Company”) is a late-stage clinical biotechnology company with expertise in protein dysregulation and a pipeline of investigational therapeutics with the potential to change the course of devastating neurodegenerative and rare peripheral amyloid diseases. Fueled by its deep scientific expertise built over decades of research, the Company is advancing a pipeline of therapeutic candidates for a number of indications and novel targets for which its ability to integrate scientific insights around neurological dysfunction and the biology of misfolded proteins can be leveraged. The Company’s wholly-owned programs include birtamimab for the potential treatment of AL amyloidosis, and a portfolio of programs for the potential treatment of Alzheimer’s disease including PRX012, which targets Amyloid beta (Aβ), and PRX123, a novel dual Aβ-tau vaccine. The Company’s partnered programs include prasinezumab, in collaboration with Roche for the potential treatment of Parkinson’s disease and other related synucleinopathies, and programs that target tau (BMS-986446/PRX005), TDP-43, and an undisclosed target (PRX019) in collaboration with Bristol Myers Squibb (BMS) for the potential treatment of Alzheimer’s disease, amyotrophic lateral sclerosis (ALS), and other neurodegenerative diseases. The Company is also entitled to certain potential milestone payments pursuant to the Company’s share purchase agreement with Novo Nordisk pertaining to the Company’s ATTR amyloidosis business (including NNC6019, formerly PRX004). The Company was formed on September 26, 2012, under the laws of Ireland and re-registered as an Irish public limited company on October 25, 2012. The Company's ordinary shares began trading on The Nasdaq Global Market under the symbol “PRTA” on December 21, 2012, and currently trade on The Nasdaq Global Select Market. Liquidity and Business Risks As of September 30, 2023, the Company had an accumulated deficit of $912.6 million and cash and cash equivalents of $670.9 million. Based on the Company's business plans, management believes that the Company’s cash and cash equivalents at September 30, 2023, are sufficient to meet its obligations for at least the next twelve months. To operate beyond such period, or if the Company elects to increase its spending on research and development programs significantly above current long-term plans or enters into potential licenses and or other acquisitions of complementary technologies, products or companies, the Company may need additional capital. The Company expects to continue to finance future cash needs that exceed its cash from operating activities primarily through its current cash and cash equivalents, payments pursuant to its agreements with Roche, Bristol Myers Squibb, and Novo Nordisk, and, to the extent necessary, through proceeds from public or private equity or debt financings, loans, and other collaborative agreements with corporate partners or other arrangements.

Summary of Significant Accounting Policies	9 Months Ended
Summary of Significant Accounting Policies	Sep. 30, 2023
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Basis of Preparation and Presentation of Financial Information These accompanying Unaudited Interim Condensed Consolidated Financial Statements have been prepared in accordance with the accounting principles generally accepted in the U.S. (“GAAP”) and with the instructions for Form 10-Q and Regulation S-X statements. Accordingly, they do not include all of the information and notes required for complete financial statements. These interim Condensed Consolidated Financial Statements should be read in conjunction with the Consolidated Financial Statements and Notes thereto contained in the Company’s Annual Report on Form 10-K filed with the U.S. Securities and Exchange Commission (the “SEC”) on February 28, 2023 (the “2022 Form 10-K”). These Unaudited Interim Condensed Consolidated Financial Statements are presented in U.S. dollars, which is the functional currency of the Company and its consolidated subsidiaries. These Unaudited Interim Condensed Consolidated Financial Statements include the accounts of the Company and its consolidated subsidiaries. All intercompany balances and transactions have been eliminated in consolidation. Unaudited Interim Financial Information The accompanying Unaudited Interim Condensed Consolidated Financial Statements and related disclosures are unaudited, have been prepared on the same basis as the annual consolidated financial statements and, in the opinion of management, reflect all adjustments, which include only normal recurring adjustments, necessary for a fair presentation of the results of operations for the periods presented. The year-end condensed consolidated balance sheet data was derived from audited financial statements, however certain information and footnote disclosures normally included in financial statements prepared in accordance with GAAP have been condensed or omitted. The condensed consolidated results of operations for any interim period are not necessarily indicative of the results to be expected for the full year or for any other future year or interim period. Use of Estimates The preparation of the Condensed Consolidated Financial Statements in conformity with GAAP requires management to make judgments, estimates and assumptions that affect the reported amounts of assets, liabilities, revenues and expenses, and related disclosures. On an ongoing basis, management evaluates its estimates, including critical accounting policies or estimates related to revenue recognition, leases and research and development expenses. The Company bases its estimates on historical experience and on various other market specific and other relevant assumptions that management believes to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities that are not readily apparent from other sources. Because of the uncertainties inherent in such estimates, actual results may differ materially from these estimates. Significant Accounting Policies There were no significant changes to the accounting policies during the nine months ended September 30, 2023, from the significant accounting policies described in Note 2 of the Notes to Consolidated Financial Statements in the 2022 Form 10-K. Concentration of Credit Risks and Other Risks and Uncertainties Financial instruments that potentially subject the Company to concentration of credit risk consist of cash and cash equivalents. The Company places its cash equivalents with multiple major and reputable financial institutions. To minimize our risk the Company and its subsidiaries invest pursuant to a Board approved investment policy, which specifies credit quality standards for our investments and limits the amount of credit exposure to any single issue, issuer or type of investment. The majority of cash and cash equivalents are invested in liquid money market funds. Cash deposits held with banks may exceed the amount of insurance provided on such deposits. To date, the Company has not experienced any losses on its deposits of cash and cash equivalents. The Company’s business is primarily conducted in U.S. dollars except for its agreements with contract manufacturers for drug supplies which are denominated in Euros. The Company recorded a loss on foreign currency exchange rate differences of approximately $253,000 and $70,000 during the nine months ended September 30, 2023 and 2022, respectively. If the Company increases its business activities that require the use of foreign currencies, it may be exposed to losses if the Euro and other such currencies continue to strengthen against the U.S. dollar. As of September 30, 2023, and December 31, 2022, approximately $2.4 million and $1.7 million, respectively, of the Company’s property and equipment, net were held in the U.S. and nominal amount were in Ireland. The Company is subject to a number of risks similar to other late-stage clinical biotechnology companies, including, but not limited to, the need to obtain adequate additional funding, possible failure of current or future preclinical testing or clinical trials, its reliance on third parties to conduct its clinical trials, the need to obtain regulatory and marketing approvals for its drug candidates, competitors developing new technological innovations, the need to successfully commercialize and gain market acceptance of the Company’s drug candidates, its right to develop and commercialize its drug candidates pursuant to the terms and conditions of the licenses granted to the Company, protection of proprietary technology, and the need to secure and maintain adequate clinical trial management, manufacturing, packaging, labeling, storage, testing, and distribution arrangements with third parties. The Company also relies on third-party consultants to assist in managing these third parties and assist with its clinical trial operations and manufacturing. If the Company does not successfully commercialize or partner any of its drug candidates, it will be unable to generate product revenue or achieve profitability. Further, the Company is also subject to broad market risks and uncertainties resulting from recent events, such as the COVID-19 pandemic, the Russian invasion of Ukraine, inflation, rising interest rates, and recession risks, as well as supply chain and labor shortages. Segments The Company operates in one segment. The Company’s chief operating decision maker (the “CODM”), its Chief Executive Officer, manages the Company’s operations on a consolidated basis for purposes of allocating resources. When evaluating the Company’s financial performance, the CODM reviews all financial information on a consolidated basis. Recent Accounting Pronouncements There were no new accounting pronouncements or changes to accounting pronouncements during the three and nine months ended September 30, 2023 that are of significance or potential significance to the Company.

Fair Value Measurements	9 Months Ended
Fair Value Measurements	Sep. 30, 2023
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements The Company measures certain financial assets and liabilities at fair value on a recurring basis, including cash equivalents. Fair value is an exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. As such, fair value is a market-based measurement that should be determined based on assumptions that market participants would use in pricing an asset or a liability. A three-tier fair value hierarchy is established as a basis for considering such assumptions and for inputs used in the valuation methodologies in measuring fair value: Level 1 — Observable inputs such as quoted prices (unadjusted) for identical assets or liabilities in active markets. Level 2 — Include other inputs that are based upon quoted prices for similar instruments in active markets, quoted prices for identical or similar instruments in markets that are not active, and model-based valuation techniques for which all significant inputs are observable in the market or can be derived from observable market data. Where applicable, these models project future cash flows and discount the future amounts to a present value using market-based observable inputs including interest rate curves, foreign exchange rates, and credit ratings. Level 3 — Unobservable inputs that are supported by little or no market activities, which would require the Company to develop its own assumptions. The fair value hierarchy also requires an entity to maximize the use of observable inputs and minimize the use of unobservable inputs when measuring fair value. The carrying amounts of certain financial instruments, such as cash equivalents, accounts receivable, accounts payable and accrued liabilities, approximate fair value due to their relatively short maturities, and low market interest rates, if applicable. Based on the fair value hierarchy, the Company classifies its cash equivalents within Level 1. This is because the Company values its cash equivalents using quoted market prices. The Company’s Level 1 securities consisted of $647.1 million and $599.1 million in money market funds included in cash and cash equivalents at September 30, 2023, and December 31, 2022, respectively.

- 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

Composition of Certain Balance Sheet Items

9 Months Ended

Sep. 30, 2023

Composition of Certain Balance Sheet Items [Abstract]

Composition of Certain Balance Sheet Items

Prepaid and Other Current Assets


	September 30,		December 31,
	2023		2022
Prepaid R&D expenses	$	7,927	$	5,325
Prepaid G&A expenses	2,218		1,597
Receivable from stock option exercises in-transit	—		62
Other	3,051		1,708
Prepaid and other current assets	$	13,196	$	8,692

Property and Equipment, net

Property and equipment, net consisted of the following (in thousands):


	September 30,		December 31,
	2023		2022
Machinery and equipment	$	10,863	$	9,901
Leasehold improvements	1,498		1,498
Purchased computer software	1,892		1,500
	14,253		12,899
Less: accumulated depreciation and amortization	(11,820)		(11,168)
Property and equipment, net	$	2,433	$	1,731

Depreciation expense was $0.2 million and $0.7 million for the three and nine months ended September 30, 2023 respectively, compared to $0.2 million and $0.5 million for the three and nine months ended September 30, 2022, respectively.

Other Current Liabilities

Other current liabilities consisted of the following (in thousands):


	September 30,		December 31,
	2023		2022
Payroll and related expenses	$	10,670	$	11,060
Professional services	1,259		605
Other	1,847		503
Other current liabilities	$	13,776	$	12,168

Net Income (Loss) Per Ordinary Share

9 Months Ended

Sep. 30, 2023

Earnings Per Share [Abstract]

Net Income (Loss) Per Ordinary Share

Basic net income (loss) per ordinary share is calculated by dividing net income (loss) by the weighted-average number of ordinary shares outstanding during the period. Shares used in diluted net income per ordinary share would include the dilutive effect of ordinary shares potentially issuable upon the exercise of stock options outstanding. However, potentially issuable ordinary shares are not used in computing diluted net loss per ordinary share as their effect would be anti-dilutive due to the loss recorded during the nine months ended September 30, 2023 and three and nine months ended September 30, 2022, and therefore diluted net loss per share is equal to basic net loss per share. During the three months ended September 30, 2023, diluted net income per ordinary share is computed by giving effect to all dilutive potential ordinary shares including options.

Net income (loss) per ordinary share was determined as follows (in thousands, except per share amounts):


	Three Months Ended September 30,				Nine Months Ended September 30,
	2023		2022		2023		2022
Numerator:
Net income (loss)	$	21,907	$	(45,764)	$	(79,552)	$	(123,298)
Denominator:
Weighted-average ordinary shares outstanding used in per share calculations - basic	53,559		46,986		53,064		46,833
Weighted-average ordinary shares outstanding used in per share calculations - diluted	58,004		46,986		53,064		46,833
Net income (loss) per share:
Basic net income (loss) per ordinary share	$	0.41	$	(0.97)	$	(1.50)	$	(2.63)
Diluted net income (loss) per ordinary share	$	0.38	$	(0.97)	$	(1.50)	$	(2.63)

The equivalent ordinary shares not included in diluted net income (loss) per share because their effect would be anti-dilutive are as follows (in thousands):


	Three Months Ended September 30,		Nine Months Ended September 30,
	2023	2022	2023	2022
Stock options to purchase ordinary shares	2,110	10,019	9,939	10,019
Restricted Stock Units (RSU)	27	—	27	—
Total	2,137	10,019	9,966	10,019

Commitment and Contingencies

9 Months Ended

Sep. 30, 2023

Commitments and Contingencies Disclosure [Abstract]

Commitment and Contingencies

Commitments and Contingencies

Lease Commitments

The Company currently has four leases relating to its facilities in South San Francisco and Brisbane, California, and Dublin, Ireland.

South San Francisco Facility

The Company has a noncancelable operating sublease (the “Lease”) covering 128,751 square feet of office and laboratory space in South San Francisco, California, U.S. (the “SSF Facility”). The Lease includes a free rent period and escalating rent payments and has a remaining lease term of 0.25 years that expires on December 31, 2023, unless terminated earlier. The Company's obligation to pay rent commenced on August 1, 2016.

Total operating lease cost was $1.6 million and $4.8 million for the three and nine months ended September 30, 2023 respectively and $1.6 million and $4.8 million for the three and nine months ended September 30, 2022, respectively. Total cash paid against the operating lease liability was $1.6 million and $4.9 million for the three and nine months ended September 30, 2023 respectively and $1.6 million and $4.7 million for the three and nine months ended September 30, 2022, respectively.

The discount rate used to determine the lease liability was 4.25%

The Company obtained a standby letter of credit in April 2016 in the initial amount of $4.1 million, which may be drawn down by the sublandlord in the event the Company fails to fully and faithfully perform all of its obligations under the Lease and to compensate the sublandlord for all losses and damages the sublandlord may suffer as a result of the occurrence of any default on the part of Company not cured within the applicable cure period. This standby letter of credit is collateralized by a certificate of deposit of the same amount which is classified as restricted cash. The Company was entitled to a $1.4 million reduction in the face amount of the standby letter of credit on the third anniversary of the contractual rent commencement, which was received in 2019, and another $1.4 million on the fifth anniversary of the contractual rent commencement, which was received in September 2021. As a condition to the reduction of the standby letter of credit amount, no uncured default by the Company shall then exist under the Lease. As of September 30, 2023, none of the remaining standby letter of credit amount of $1.4 million has been used.

Sub-Sublease of South San Francisco Facility

On July 18, 2018, the Company entered into a Sub-Sublease Agreement (the “Sub-Sublease”) with Assembly Biosciences, Inc. (the “Sub-Subtenant”) to sub-sublease approximately 46,641 square feet of office and laboratory space of the SSF Facility to the Sub-Subtenant. The Sub-Sublease is considered an operating lease under ASC 842. For the three and nine months ended September 30, 2023, the Company recorded $0.7 million and $2.2 million respectively and $0.7 million, and $2.2 million for the three and nine months ended September 30, 2022 respectively, of sub-lease rental income as an offset to its operating expenses.

The Sub-Sublease provides for initial annual base rent for the complete Sub-Subleased Premises of approximately $2.7 million, with increases of approximately 3.5% in annual base rent on September 1, 2019, and each anniversary thereof. The Sub-Sublease rental income excludes reimbursements for executory costs received from the Sub-Subtenant. The Sub-Sublease became effective on September 24, 2018, and has a term of 5.2 years which terminates on December 15, 2023. The Sub-Sublease will terminate if the Lease or the corresponding master lease terminates. The Company or the Sub-Subtenant may elect, subject to limitations set forth in the Sub-Sublease, to terminate the Sub-Sublease following a material casualty or condemnation affecting the Subleased Premises. The Company may terminate the Sub-Sublease following an event of default,

which is defined in the Sub-Sublease to include, among other things, non-payment of amounts owing by the Sub-Subtenant under the Sub-Sublease.

The Company is required under the Lease to pay to the sublandlord 50% of that portion of the cash sums and other economic consideration received from the Sub-Subtenant that exceeds the base rent paid by the Company to the sublandlord after deducting certain of the Company’s costs.

Dublin

In June 2021, the Company entered into a lease agreement for office space in Dublin, Ireland, which commenced in August 2021 and had an initial term of one year. In April 2023, the Company renewed the lease for another one year with a termination date of July 2024. In addition, the Company entered into a lease agreement for additional office space in Dublin, Ireland, which commenced in August 2023 and has an initial term of one year. Both of these leases have an automatic renewal clause, pursuant to which the agreement will be extended automatically for successive periods equal to the current term, unless the agreement is cancelled by the Company.

Brisbane Facility

On October 28, 2022, Prothena Biosciences Inc, a wholly owned subsidiary of the Company, entered into a noncancelable operating sublease (the "Brisbane Sublease") to sublease approximately 31,157 square feet of office and laboratory space located in Brisbane, California (the “Brisbane Facility”) with Arcus Biosciences, Inc., (the "Sublandlord"). The Brisbane Sublease became effective on October 28, 2022. The Brisbane Sublease provides that the Company's obligation to pay rent commenced on July 1, 2023, which is subject to abatement for the first six months following such date, with the exception of the seventh rent payment that was due upon execution of the Brisbane Sublease. The Company is obligated to make lease payments totaling approximately $14.9 million over the lease term, which expires on September 30, 2028, unless terminated earlier. The Brisbane Sublease further provides that the Company is obligated to pay to the Sublandlord certain costs, including taxes and operating expenses. The Company has the option to extend the sublease by providing written notice at least nine months prior to the expiration of the sublease term. As of September 30, 2023, the Brisbane Sublease has a remaining lease term of 5.0 years.

The Brisbane Sublease is considered an operating lease and the accounting lease commencement date was on July 31, 2023 when the Company gained control over physical access to the Brisbane Facility. The Company recorded a right-of-use asset of approximately $11.4 million and lease liability of approximately $3.6 million relating to the Brisbane Sublease on the lease commencement date. The discount rate used to determine the lease liability was 5.76%. The initial measurement of right-of-use asset for the Brisbane Sublease includes the tenant improvement added by the Company wherein the lessor was deemed the accounting owner.

The Company is entitled to an improvement allowance of up to $9.3 million, to be used for costs incurred by the Company to construct certain improvements to the Brisbane Facility and to prepare for the Company's occupancy of the Brisbane Facility. As of September 30, 2023, $5.5 million has been received from the Sublandlord and the Company is obligated to fund construction costs incurred in excess of the improvement allowance.

Total operating lease cost for the Brisbane Sublease was $0.5 million and $0.5 million for the three and nine months ended September 30, 2023, respectively. Total cash paid against the operating lease liability was $0.2 million and $0.2 million for the three and nine months ended September 30, 2023, respectively.

In conjunction with the Brisbane Sublease, the Company obtained a standby letter of credit in the initial amount of $0.9 million, which may be drawn down by the Sublandlord in the event the Company fails to fully and faithfully perform all of its obligations under the Brisbane Sublease and to compensate the Sublandlord for all losses and damages the Sublandlord may suffer as a result of the occurrence of any default on the part of the Company not cured within the applicable cure period. As of September 30, 2023, none of the standby letter of credit amount of $0.9 million has been used.

Future minimum payments under the above-described noncancelable operating leases, including a reconciliation to the lease liabilities recognized in the Condensed Consolidated Balance Sheets, and future minimum rentals to be received under the Sub-Sublease as of September 30, 2023, are as follows (in thousands):


Year Ended December 31,	Operating Leases		Sub-Sublease Rental
2023 (3 months)	1,713		672
2024	2,828		—
2025	3,052		—
2026	3,158		—
2027	3,269		—
Thereafter	2,523		—
Total	$	16,543	$	672
Less: Present value adjustment	(5,808)
Lease liability	$	10,735

Indemnity Obligations

The Company has entered into indemnification agreements with its current and former directors and officers and certain key employees. These agreements contain provisions that may require the Company, among other things, to indemnify such persons against certain liabilities that may arise because of their status or service and advance their expenses incurred as a result of any indemnifiable proceedings brought against them. The obligations of the Company pursuant to the indemnification agreements continue during such time as the indemnified person serves the Company and continues thereafter until such time as a claim can be brought. The maximum potential amount of future payments the Company could be required to make under these indemnification agreements is unlimited; however, the Company has a director and officer liability insurance policy that limits its exposure and enables the Company to recover a portion of any future amounts paid. As a result of its insurance policy coverage, the Company believes the estimated fair value of these indemnification agreements is minimal. Accordingly, the Company had no liabilities recorded for these agreements as of September 30, 2023, and 2022.

Other Commitments

In the normal course of business, the Company enters into various firm purchase commitments primarily related to research and development activities. As of September 30, 2023, the Company had non-cancelable purchase commitments to suppliers for $14.6 million of which $8.3 million is included in current liabilities, and contractual obligations under license agreements of $0.4 million of which $15,000 is included in current liabilities. The following is a summary of the Company's non-cancelable purchase commitments and contractual obligations as of September 30, 2023 (in thousands):


	Total		2023		2024		2025		2026		2027		Thereafter
Purchase Obligations (1)	$	14,584	$	14,426	$	122	$	36	$	—	$	—	$	—
Contractual obligations under license agreements	402		64		64		64		60		60		90
Total	$	14,986	$	14,490	$	186	$	100	$	60	$	60	$	90

________________

(1) Purchase obligations consist of non-cancelable purchase commitments to suppliers and contract research organizations.

Significant Agreements	9 Months Ended
Significant Agreements	Sep. 30, 2023
Collaborative Agreement [Abstract]
Significant Agreements	Significant Agreements Roche License Agreement In December 2013, the Company through its wholly owned subsidiary Prothena Biosciences Limited and Prothena Biosciences Inc entered into a License, Development, and Commercialization Agreement (the “License Agreement”) with F. Hoffmann-La Roche Ltd. and Hoffmann-La Roche Inc. (together, “Roche”) to develop and commercialize certain antibodies that target α-synuclein, including prasinezumab, which are referred to collectively as “Licensed Products.” Upon the effectiveness of the License Agreement in January 2014, the Company granted to Roche an exclusive, worldwide license to develop, make, have made, use, sell, offer to sell, import and export the Licensed Products. The Company retained certain rights to conduct development of the Licensed Products and an option to co-promote prasinezumab in the U.S. During the term of the License Agreement, the Company and Roche will work exclusively with each other to research and develop antibody products targeting alpha-synuclein (or α-synuclein) potentially including incorporation of Roche’s proprietary Brain Shuttle™ technology to potentially increase delivery of therapeutic antibodies to the brain. The License Agreement provided for Roche making an upfront payment to the Company of $30.0 million, which was received in February 2014; making a clinical milestone payment of $15.0 million upon initiation of the Phase 1 clinical trial for prasinezumab, which was received in May 2014; making a clinical milestone payment of $30.0 million upon dosing of the first patient in the Phase 2 clinical trial for prasinezumab, which was achieved in June 2017; and making a clinical milestone payment of $60.0 million upon dosing of the first patient in the global Phase 2b PADOVA study for prasinezumab, which was achieved in May 2021. For prasinezumab, Roche is obligated to pay: •up to $290.0 million upon the achievement of development, regulatory, and various first commercial sales milestones; •up to $155.0 million upon achievement of U.S. commercial sales milestones; •up to $175.0 million upon achievement of ex-U.S. commercial sales milestones; and •tiered, high single-digit to high double-digit royalties in the teens based on U.S. and ex-U.S. annual net sales, subject to certain adjustments, with respect to the applicable Licensed Product. Roche bore 100% of the cost of conducting the research collaboration under the License Agreement during the research term, which expired December 31, 2017. In May 2021, the Company exercised its rights under the terms of License Agreement to receive potential U.S. commercial sales milestone and royalties, in lieu of a U.S. profit and loss share for prasinezumab in Parkinson’s disease. Thus in the U.S., through May 28, 2021, the parties shared all development costs, all of which were allocated 70% to Roche and 30% to the Company, for prasinezumab in the Parkinson’s disease indication. If the Company opts in to participate in co-development and co-funding for any other Licensed Products and/or indications, the parties will share all development and commercialization costs, as well as profits, all of which will be allocated 70% to Roche and 30% to the Company. The Company initiated a Phase 1 clinical trial for prasinezumab in 2014. Following the Phase 1 clinical trial, Roche became primarily responsible for developing, obtaining and maintaining regulatory approval for and commercializing Licensed Products. Roche also became responsible for the clinical and commercial manufacture and supply of Licensed Products. In addition, the Company has an option under the License Agreement to co-promote prasinezumab in the U.S. in the Parkinson’s disease indication. If the Company exercises such option, it may also elect to co-promote additional Licensed Products in the U.S. approved for Parkinson’s disease. Outside the U.S., Roche will have responsibility for developing and commercializing the Licensed Products. Roche bears all costs that are specifically related to obtaining or maintaining regulatory approval outside the U.S. and will pay the Company a variable royalty based on annual net sales of the Licensed Products outside the U.S. The License Agreement continues on a country-by-country basis until the expiration of all payment obligations under the License Agreement. The License Agreement may also be terminated (i) by Roche at will after the first anniversary of the effective date of the License Agreement, either in its entirety or on a Licensed Product-by-Licensed Product basis, upon 90 days’ prior written notice to the Company prior to first commercial sale and 180 days’ prior written notice to Prothena after first commercial sale, (ii) by either party, either in its entirety or on a Licensed Product-by-Licensed Product or region-by-region basis, upon written notice in connection with a material breach uncured 90 days after initial written notice, and (iii) by either party, in its entirety, upon insolvency of the other party. The License Agreement may be terminated by either party on a patent-by-patent and country-by-country basis if the other party challenges a given patent in a given country. The Company’s rights to co-develop Licensed Products under the License Agreement will terminate if the Company commences certain studies for certain types of competitive products. The Company’s rights to co-promote Licensed Products under the License Agreement will terminate if the Company commences a Phase 3 study for such competitive products. The License Agreement cannot be assigned by either party without the prior written consent of the other party, except to an affiliate of such party or in the event of a merger or acquisition of such party, subject to certain conditions. The License Agreement also includes customary provisions regarding, among other things, confidentiality, intellectual property ownership, patent prosecution, enforcement and defense, representations and warranties, indemnification, insurance, and arbitration and dispute resolution. Performance Obligations As of September 30, 2023, and December 31, 2022, there were no remaining performance obligations under License Agreement since the obligations related to research and development activities were only for the Phase 1 clinical trial and the remaining obligations were delivered or performed. Milestone Accounting Under the License Agreement, only if the U.S. and or global options are exercised, the Company is eligible to receive milestone payments upon the achievement of development, regulatory and various first commercial sales milestones. Milestone payments are evaluated under ASC Topic 606. Factors considered in this determination included scientific and regulatory risk that must be overcome to achieve each milestone, the level of effort and investment required to achieve the milestone, and the monetary value attributed to the milestone. Accordingly, the Company estimates payments in the transaction price based on the most likely approach, which considers the single most likely amount in a range of possible amounts related to the achievement of these milestones. Additionally, milestone payments are included in the transaction price only when the Company can conclude it is probable that a significant revenue reversal will not occur in future periods when the milestone is achieved. The Company excludes the milestone payments and royalties in the initial transaction price calculation because such payments are considered to be variable considerations with constraint. Such milestone payments and royalties will be recognized as revenue once the Company can conclude it is probable that a significant revenue reversal will not occur in future periods. The clinical and regulatory milestones under the License Agreement after the point at which the Company could opt out are considered to be variable considerations with constraint due to the fact that active participation in the development activities that generate the milestones is not required under the License Agreement, and the Company can opt out of these activities. There are no refunds or claw-back provisions and the milestones are uncertain of occurrence even after the Company has opted out. Based on this determination, these milestones will be recognized when the Company can conclude it is probable that a significant revenue reversal will not occur in future periods. Collaboration Agreement with Bristol Myers Squibb Overview On March 20, 2018, the Company, through its wholly owned subsidiary Prothena Biosciences Limited (“PBL”), entered into a Master Collaboration Agreement (the “Collaboration Agreement”) with Celgene Switzerland LLC (“Celgene”), a subsidiary of Celgene Corporation (which was acquired by Bristol Myers Squibb (“BMS”) in November 2019), pursuant to which Prothena granted to Celgene a right to elect in its sole discretion to exclusively license rights both in the U.S. (the “US Rights”) and on a global basis (the “Global Rights”), with respect to the Company’s programs to develop and commercialize antibodies targeting tau, TDP-43 and an undisclosed target (the “Collaboration Targets”). For each such program, BMS may exercise its US Rights at the IND filing, and if it so exercises such US Rights would also have a right to expand the license to Global Rights. If BMS exercises its US Rights for a program, then following the first to occur of (a) completion by the Company, in its discretion and at its cost, of Phase 1 clinical trials for such program or (b) the date on which BMS elects to assume responsibility for completing such Phase 1 clinical trials (at its cost), BMS would have decision making authority over development activities and all regulatory, manufacturing and commercialization activities in the U.S. As discussed below, BMS exercised its US Rights for the tau/BMS-986446 (formerly PRX005) Collaboration Target and on July 30, 2021, PBL entered into a U.S. License Agreement granting BMS the exclusive license to develop, manufacture and commercialize antibody products in the United States targeting tau (the “Tau US License Agreement”). Subsequently, BMS exercised its Global Rights for the tau/BMS-986446 Collaboration Target and on July 5, 2023, PBL entered into a Global License Agreement granting BMS the exclusive license to develop, manufacture and commercialize tau Collaboration Products globally for any and all uses or purposes with respect to any human or animal disease, disorder or condition (the “Tau Global License Agreement”). The Tau Global License Agreement supersedes and replaces the Tau US License Agreement in its entirety. The Collaboration Agreement provided for Celgene making an upfront payment to the Company of $100.0 million which was received in April 2018, plus future potential license exercise payments and regulatory and commercial milestones for each program under the Collaboration Agreement, as well as royalties on net sales of any resulting marketed products. In connection with the Collaboration Agreement, the Company and Celgene entered into a Share Subscription Agreement on March 20, 2018, under which Celgene subscribed to 1,174,536 of the Company’s ordinary shares for a price of $42.57 per share, for a total of approximately $50.0 million. BMS US and Global Rights and Licenses On a program-by-program basis, beginning on the effective date of the Collaboration Agreement and ending on the date that the IND Option term expires for such program (which generally occurs sixty days after the date on which the Company delivers to BMS the first complete data package for an IND that was filed for a lead candidate from the relevant program), BMS may elect in its sole discretion to exercise its US Rights to receive an exclusive license to develop, manufacture and commercialize antibodies targeting the applicable Collaboration Target in the U.S. (the “US License”). If BMS exercises its US Rights for a collaboration program, it is obligated to pay the Company an exercise fee of approximately $80.0 million per program. Thereafter, following the first to occur of (a) completion by the Company, in its discretion and at its cost, of Phase 1 clinical trials for such program or (b) BMS’s election to assume responsibility to complete such Phase 1 clinical trials (at its cost), BMS would have the sole right to develop, manufacture and commercialize antibody products targeting the relevant Collaboration Target for such program (the “Collaboration Products”) in the U.S. On a program-by-program basis, following completion of a Phase 1 clinical trial for a collaboration program for which BMS has previously exercised its US Rights, BMS may elect in its sole discretion to exercise its Global Rights with respect to such collaboration program to receive a worldwide, exclusive license to develop, manufacture and commercialize antibodies targeting the applicable Collaboration Target (the “Global License”). If BMS exercises its Global Rights, BMS would be obligated to pay the Company an additional exercise fee of $55.0 million for such collaboration program. The Global Rights would then replace the US Rights for that collaboration program, and BMS would have decision making authority over developing, obtaining and maintaining regulatory approval for, manufacturing and commercializing the Collaboration Products worldwide. After BMS’s exercise of Global Rights for a collaboration program, the Company is eligible to receive up to $562.5 million in regulatory and commercial milestones per program. Following an exercise by BMS of either US Rights or Global Rights for such collaboration program, the Company will also be eligible to receive tiered royalties on net sales of Collaboration Products ranging from high single digit to high teen percentages, on a weighted average basis depending on the achievement of certain net sales thresholds. Such exercise fees, milestones and royalty payments are subject to certain reductions as specified in the Collaboration Agreement, the agreement for US Rights and the agreement for Global Rights. BMS will continue to pay royalties on a Collaboration Product-by-Collaboration Product and country-by-country basis, until the latest of (i) expiration of certain patents covering the Collaboration Product, (ii) expiration of all regulatory exclusivity for the Collaboration Product, and (iii) an agreed period of time after the first commercial sale of the Collaboration Product in the applicable country (the “Royalty Term”). Term and Termination The research term under the Collaboration Agreement continues for a period of six years, which BMS may extend for up to two additional 12-month periods by paying an extension fee of $10.0 million per extension period. The term of the Collaboration Agreement continues until the last to occur of the following: (i) expiration of the research term; (ii) expiration of all US Rights terms; and (iii) expiration of all Global Rights terms. The term of any US License or Global License would continue on a Licensed Product-by-Licensed Product and country-by-country basis until the expiration of all Royalty Terms under such agreement. The Collaboration Agreement may be terminated (i) by either party on a program-by-program basis if the other party remains in material breach of the Collaboration Agreement following a cure period to remedy the material breach, (ii) by BMS at will on a program-by-program basis or in its entirety, (iii) by either party, in its entirety, upon insolvency of the other party, or (iv) by the Company, in its entirety, if BMS challenges a patent licensed by the Company to BMS under the Collaboration Agreement. Performance Obligations The Company assessed the Collaboration Agreement and concluded that it represented a contract with a customer within the scope of ASC 606. Per ASC 606, a performance obligation is defined as a promise to transfer a good or service or a series of distinct goods or services. At inception of the Collaboration Agreement, the Company is not obligated to transfer the US License or Global License to BMS unless BMS exercises its US Rights or Global Rights, respectively, and the Company is not obligated to perform development activities under the development plan during preclinical and Phase 1 clinical trials including the regulatory filing of the IND. The discovery, preclinical and clinical development activities performed by the Company are to be performed at the Company’s discretion and are not promised goods or services and therefore are not considered performance obligations under ASC 606, unless and until the Company agrees to perform the Phase 1 clinical trials (after the IND option exercise) that are determined to be performance obligations at the time the option is exercised. Per the terms of the Collaboration Agreement, the Company may conduct discovery activities to characterize, identify and generate antibodies to become collaboration candidates that target such Collaboration Target, and thereafter may pre-clinically develop collaboration candidates to identify lead candidates that target such Collaboration Target and file an IND with the U.S. Food and Drug Administration (the “FDA”) for a Phase 1 clinical trial for such lead candidates. In the event the Company agrees to be involved in a Phase 1 clinical trial, the Company will further evaluate whether any such promise represents a performance obligation at the time the option is exercised. If it is concluded that the Company has obligated itself to an additional performance obligation besides the license granted at IND option exercise, then the effects of the changes in the arrangement will be evaluated under the modification guidance of ASC 606. The Company is not obligated to perform manufacturing activities. Per the terms of the Collaboration Agreement, to the extent that the Company, at its discretion, conducts a program, the Company shall be responsible for the manufacture of collaboration candidates and collaboration products for use in such program, as well as the associated costs. Delivery of manufactured compound (clinical product supply) is not deemed a performance obligation under ASC 606 as the Company is not obligated to transfer supply of collaboration product to BMS unless BMS exercises its right to participate in the Phase 1 development. Compensation for the Company’s provision of inventory supply, to the extent requested by BMS would be paid to the Company by BMS at a reasonable stand-alone selling price for such supply. Given that (i) there is substantial uncertainty about the development of the programs, (ii) the pricing for the inventory is at its standalone selling price and (iii) the manufacturing services require the entity to transfer additional goods or services that are incremental to the goods and services provided prior to the resolution of the contingency, the Company’s supply of product is not a material right. Therefore, the inventory supply is not considered a performance obligation unless and until, requested by BMS. In addition to the grant of the US License after BMS exercises its US Rights for a program, BMS is entitled to receive certain ancillary development services from the Company, such as technology transfer assistance, regulatory support, safety data reporting activities and transition supply, if requested by BMS. In addition to the grant of the Global License after BMS exercises the Global Rights for a program, BMS is entitled to receive certain ancillary development services from the Company, such as ongoing clinical trial support upon request by BMS, transition supply, if requested by BMS, and regulatory support for coordination of pharmacovigilance matters. The Company evaluated the potential obligations to transfer the US Licenses and Global Licenses and performance of the ancillary development services subsequent to exercise of the US Rights and Global Rights, if the options are exercised by BMS, under ASC 606-10-55-42 and 55-43 to determine whether the US Rights or the Global Rights provided BMS a “material right” and concluded that BMS’s options to exercise its US Rights and Global Rights represented “material rights” to BMS that it would not have received without entering into the Agreement. There were a total of six options at inception including US Rights and Global Rights to acquire a US License and a Global License, respectively, and rights to request certain development services (following exercise of the US Rights and Global Rights, respectively) for each of the three programs, with four options remaining as of September 30, 2023. Per ASC 606, the US Rights and Global Rights are material rights and therefore are performance obligations. The goods and services underlying the options are not accounted for as separate performance obligations, but rather become performance obligations, if and when, an option is exercised. US License Agreement for the Tau/BMS-986446 Collaboration Target On July 30, 2021, the Company entered into the Tau US License Agreement. The Tau US License Agreement included an upfront payment of $80.0 million. The Tau US License Agreement included the following distinct performance obligations: (1) the delivery of the US License for tau/BMS-986446 Collaboration Target (“Tau US License Obligation”); and (2) the Company’s obligation to provide development activities under the development plan during any Phase 1 clinical trials (the “Tau US Development Services Obligation”). Revenue allocated to the Tau US License Obligation is recognized when the Company has satisfied its obligation at a point in time, while the revenue allocated to the Tau US Development Services Obligation are recognized over time using an input-based model. Global License Agreement for the Tau/BMS-986446 Collaboration Target On July 5, 2023, the Company entered into the Tau Global License Agreement, which as discussed above supersedes and replaces the Tau US License Agreement in its entirety. The Company received the associated option exercise fee of $55.0 million in August 2023 and it will be eligible to receive regulatory and sales milestones up to $562.5 million upon achievement of certain developmental events, including regulatory approval of a tau Collaboration Product, and on BMS achieving certain annual net sales thresholds in the United States and worldwide. The Company also will be eligible to receive tiered royalties on net sales of tau Collaboration Products, ranging from high single digit to high teen percentages, on a weighted average basis depending on the achievement of certain net sales thresholds. The Company’s distinct performance obligation under the Tau Global License Agreement was limited to the delivery of the Global License for tau/BMS-986446 Collaboration Target (“Tau Global License Obligation”). Revenue allocated to the Tau Global License Obligation is recognized when the Company has satisfied its obligation at a point in time. Transaction Price At the inception of the Collaboration Agreement, the Company did not transfer any goods or services to BMS (formerly Celgene) that are material. Accordingly, the Company has concluded that the initial transaction price will be recognized as a contract liability and will be deferred until the Company transfers control of goods or services to BMS (which would be when BMS exercises the US Right or Global Right and receives control of the US License or Global License for at least one of the programs), or when the IND Option term expires if BMS does not exercise the US Right (which is generally sixty days after the date on which the Company delivers to BMS the first complete data package for an IND that was filed for a lead candidate from the relevant program), or when the Phase 1 Option term expires if BMS does not exercise the Global Right (which is generally ninety days after the date on which the Company delivers to BMS the first complete data package for a Phase 1 clinical trial for a lead candidate from the relevant program) or at the termination of the Collaboration Agreement, whichever occurs first. At such point that the Company transfers control of goods or services to BMS, or when the option expires, the Company will recognize revenue as a continuation of the original contract. Under this approach, the Company will treat the consideration allocated to the material right as an addition to the consideration for the goods or services underlying the contract option. At inception of the Collaboration Agreement, the Company estimated the standalone selling price for each performance obligation (i.e., the US Rights and Global Rights by program). The estimate of standalone selling price for the US Rights and Global Rights by program was based on the adjusted market assessment approach using a discounted cash flow model. The key assumptions used in the discounted cash flow model included the market opportunity for commercialization of each program in the U.S. or globally depending on the license, the probability of successfully developing and commercializing a given program target, the estimated remaining development costs for the respective program, the estimated time to commercialization of the drug for that program and a discount rate. The initial transaction price under the Collaboration Agreement, pursuant to ASC 606, was $110.2 million, including the $100.0 million upfront payment and $10.2 million premium on the ordinary shares purchased under the SSA. The Company allocated the initial transaction price across the US Rights and Global Rights for each program in a range of approximately $15-$25 million and $10-$18 million, respectively. The Company did not include the option fees in the initial transaction price because such fees are contingent on the options to the US Rights and the Global Rights being exercised. Upon the exercise of the US Rights and the Global Rights for a program, the Company will have the obligation to deliver the US License and Global License and provide certain ancillary development services if requested by BMS, subsequent to its exercise of the US Rights and Global Rights, respectively, for such program. The Company will include the option fees in the transaction price at the point in time a material right is exercised and the Company transfers control of the goods and services to BMS. In addition, the Company did not include in the initial transaction price certain clinical and regulatory milestone payments since they relate to licenses for which BMS has not yet exercised its option to obtain and these variable considerations are constrained due to the likelihood of a significant revenue reversal. Upon entering into the Tau US License Agreement, the Company granted BMS a US License for the tau/BMS-986446 Collaboration Target, which transferred control of such underlying US License to BMS. Following execution of the Tau US License Agreement, BMS paid the Company a $80.0 million option exercise fee. Under the continuation of the original contract method, the Company computed the relative sales price after the Company transferred control of the US License for tau/BMS-986446. The Company used the original allocated consideration for the US Right for tau/BMS-986446 of $24.9 million (computed at the inception of the contract) plus the $80.0 million option exercise fee to arrive at the total transaction price of approximately $104.9 million. This total transaction price was further allocated using the relative sales price method between the Tau US License Obligation and the Tau US Development Services Obligation. The best estimate of selling price for the US License for tau/BMS-986446 was based on a discounted cash flow model. The key assumptions used in the discounted cash flow model used to determine the best estimate of selling price for the license included the market opportunity for commercialization of tau/BMS-986446, the probability of successfully developing/commercializing BMS-986446, the remaining development costs for tau/BMS-986446, and the estimated time to commercialization of tau/BMS-986446. Based on the relative selling price method, the amount that the Company allocated to the performance obligations is as follows: $77.5 million to the license to be recognized concurrent with the delivery of the license; and $27.5 million as development services to be recognized based on percentage of completion over the service period estimated to be from 2021-2024. Upon entering into the Tau Global License Agreement, the Company granted BMS a Global License for the tau/BMS-986446 Collaboration Target, which transferred control of such underlying Global License to BMS. Following execution of the Tau Global License Agreement, BMS paid the Company a $55.0 million option exercise fee. Under the continuation of the original contract method, the Company computed the relative sales price after the Company transferred control of the Global License for tau/BMS-986446. The Company used the original allocated consideration for the Global Right for tau/BMS-986446 of $17.9 million (computed at the inception of the contract) plus the $55.0 million option exercise fee to arrive at the total transaction price of approximately $72.9 million. Given that the Company’s distinct performance obligation under the Tau Global License Agreement was limited to the Tau Global License Obligation no further allocation was required. Significant Payment Terms The upfront payment of $100.0 million was received in April 2018, while all option fees and milestone payments are due within 30 days after the achievement of the relevant milestone by BMS or receipt by BMS of an invoice for such an amount from the Company. The Collaboration Agreement does not have a significant financing component since a substantial amount of consideration promised by BMS to the Company is variable and the amount of such variable consideration varies based upon the occurrence or non-occurrence of future events that are not within the control of either BMS or the Company. Variable considerations related to clinical and regulatory milestone payments and option fees are constrained due to the likelihood of a significant revenue reversal. Revenue and Expense Recognition For the three and nine months ended September 30, 2023, collaboration revenue from BMS of $84.9 million and $91.0 million and for three and nine months ended September 30, 2022, $1.5 million and $3.9 million, respectively. Collaboration revenue for the three and nine months ended September 30, 2023 included $72.9 million recognized for the tau Global License Obligation ($55.0 million tau global option exercise fee and $17.9 million of deferred revenue recognized for the Global Right for the tau Collaboration Product), $4.7 million under a supply agreement with BMS and the remainder was primarily recognized for tau US Development Services Obligation. As of September 30, 2023, the aggregate amount of the transaction price allocated to the performance obligations that are unsatisfied was $0.3 million. The Company had $5.2 million and nil accounts receivable from BMS at September 30, 2023, and December 31, 2022, respectively. Deferred Revenue The deferred revenue balance at the beginning of the quarter ended September 30, 2023 was $92.5 million of which $17.9 million was recognized as revenue for the Global Right for the tau Collaboration Product and $6.9 million was recognized as revenue related to the Tau US Development Services Obligation performed during the quarter ended September 30, 2023. As of September 30, 2023, the deferred revenue balance was $67.7 million, of which $0.3 million was current and the balance of $67.4 million was long term deferred revenue. The deferred revenue balance as of September 30, 2023, includes amounts deferred related to outstanding US Rights and Global Rights of $67.4 million and unsatisfied performance obligations for the US Rights for the tau/BMS-986446 program of $0.3 million. Milestone and Royalties Accounting The Company is eligible to receive milestone payments of up to $90.0 million per program upon the achievement of certain specified regulatory milestones and milestone payments of up to $375.0 million per program upon the achievement of certain specified commercial sales milestones under the US License for such program. The Company is also eligible to receive milestone payments of up to $187.5 million per program upon the achievement of certain specified regulatory milestones and milestone payments of up $375.0 million per program upon the achievement of certain specified commercial sale milestones under the Global License for such program. Milestone payments are evaluated under ASC Topic 606. Factors considered in this determination included scientific and regulatory risk that must be overcome to achieve each milestone, the level of effort and investment required to achieve the milestone, and the monetary value attributed to the milestone. Accordingly, the Company estimates payments in the transaction price based on the most likely approach, which considers the single most likely amount in a range of possible amounts related to the achievement of these milestones. Additionally, milestone payments are included in the transaction price only when the Company can conclude it is probable that a significant revenue reversal will not occur in future periods. The Company excluded the milestone payments and royalties in the initial transaction price because such payments are considered to be variable considerations with constraint. Such milestone payments and royalties will be recognized as revenue at a point in time when the Company can conclude it is probable that a significant revenue reversal will not occur in future periods. The Company did not achieve any clinical and regulatory milestones under the Collaboration Agreement during the three and nine months ended September 30, 2023 and 2022. Novo Nordisk Share Purchase Agreement On July 8, 2021, the Company together with its wholly owned subsidiary, Prothena Biosciences Limited (“PBL”), entered into a definitive share purchase agreement with Novo Nordisk A/S and Novo Nordisk Region Europe A/S (each an unrelated party). Under the terms of such agreement, Novo Nordisk acquired PBL’s wholly-owned subsidiary, Neotope Neuroscience Limited (“NNL”) and gained full worldwide rights to the intellectual property and related rights to the Company’s ATTR amyloidosis business and pipeline. Upon consummation of the transaction, NNL ceased to be a related party of PBL. The aggregate purchase price consisted of an upfront payment of $60.0 million in cash, subject to customary purchase price adjustments. Should Novo Nordisk achieve certain stages of development or commercialization for products or product candidates containing NNC6019 (formerly PRX004) or a derivative thereof in ATTR amyloidosis, PBL is entitled to receive certain milestone payments based on specified development and commercial milestones. The development and commercialization milestone payments will be discounted if the milestone events are achieved with respect to other indications. Should Novo Nordisk achieve specified thresholds of worldwide, annual net sales of the milestone products, regardless of indication, PBL will also be entitled to receive specified one-time net sales milestone payments. All milestone payments attributable to an achieved milestone will be paid to PBL, subject to Novo Nordisk’s offset right for indemnity claims or unpaid amounts in respect of any purchase price adjustment. The upfront payment of $60.0 million was accounted for as revenue in 2021. In addition to the upfront payment, Novo Nordisk agreed to pay for certain out of pocket expenses under the Transition Services Agreement, which netted to $0.7 million after closing adjustments related to the sale of the ATTR amyloidosis business and pipeline. Contingent Consideration /Milestone Accounting In December 2022, the Company received a $40.0 million development milestone payment related to the continued advancement of NNC6019 in a Phase 2 clinical trial for the treatment of ATTR cardiomyopathy. This amount was accounted for as revenue from license and intellectual property in 2022. The Company is eligible to receive additional development and sales milestone payments from Novo Nordisk totaling up to $1.13 billion upon achievement of certain specified development and commercial sales milestones under the share purchase agreement. The Company excluded the milestone payments in the initial transaction price because such payments are considered to be variable considerations with constraint. Such milestone payments will be recognized as revenue at a point in time when the Company can conclude it is probable that a significant revenue reversal will not occur in future periods. Revenue Recognition Total revenue recognized related to the transaction during the nine months ended September 30, 2023 and 2022 was nil and nil, respectively. The Company had no accounts receivable from Novo Nordisk as of September 30, 2023 and December 31, 2022, respectively.

Shareholders' Equity	9 Months Ended
Shareholders' Equity	Sep. 30, 2023
Equity [Abstract]
Shareholders' Equity	Shareholders' Equity Ordinary Shares As of September 30, 2023, the Company had 100,000,000 ordinary shares authorized for issuance with a par value of $0.01 per ordinary share and 53,638,615 ordinary shares issued and outstanding. Each ordinary share is entitled to one vote and, on a pro rata basis, to dividends when declared and the remaining assets of the Company in the event of a winding up. Euro Deferred Shares As of September 30, 2023, the Company had 10,000 Euro Deferred Shares authorized for issuance with a nominal value of €22 per share. No Euro Deferred Shares are outstanding at September 30, 2023. The rights and restrictions attaching to the Euro Deferred Shares rank pari passu with the ordinary shares and are treated as a single class in all respects. December 2022 Offering In December 2022, the Company completed an underwritten public offering of an aggregate of 3,250,000 of its ordinary shares at a public offering price of $56.50 per ordinary share. The Company received aggregate net proceeds of approximately $172.4 million, after deducting the underwriting discount and offering costs. In January 2023, the Company issued an additional 395,096 ordinary shares resulting from the underwriter’s partial exercise of their 30-day option to purchase up to an additional 487,500 ordinary shares of as part of the December 2022 underwritten public offering. The Company received approximately $20.9 million proceeds from the exercise, net of underwriting discount but before deducting any offering costs. At-the-Market Offering In December 2021, the Company entered into an Equity Distribution Agreement (the “December 2021 Distribution Agreement”), pursuant to which the Company may issue and sell, from time to time, the Company's ordinary shares. In connection with entering into the December 2021 Distribution Agreement, on December 23, 2021, the Company filed with the SEC a prospectus supplement relating to the offer, issuance and sale of up to $250.0 million of the Company’s ordinary shares pursuant to the December 2021 Distribution Agreement. For the three and nine months ended September 30, 2023, the Company sold and issued nil and 42,361 ordinary shares, respectively, pursuant to the December 2021 Distribution Agreement. For the nine months ended September 30, 2023, total gross proceeds was approximately $3.2 million before deducting underwriting discounts, commissions, and other offering expenses payable by the Company of $0.1 million. As of September 30, 2023, the Company has sold and issued 953,589 ordinary shares for total gross proceeds of approximately $56.3 million before deducting underwriting discounts, commissions, and other offering expenses payable by the Company of $1.8 million. The issuance and sale of the Company’s ordinary shares pursuant to the December 2021 Distribution Agreement is deemed an “at-the-market” offering and is registered under the Securities Act of 1933, as amended.

- Definition

The entire disclosure for equity.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
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-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (b)
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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Reference 5: http://www.xbrl.org/2003/role/disclosureRef
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Reference 6: http://www.xbrl.org/2003/role/disclosureRef
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Reference 7: http://www.xbrl.org/2003/role/disclosureRef
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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://fasb.org/us-gaap/role/ref/legacyRef
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Reference 11: http://www.xbrl.org/2003/role/disclosureRef
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Reference 12: http://www.xbrl.org/2003/role/disclosureRef
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Reference 13: http://www.xbrl.org/2003/role/disclosureRef
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Reference 14: http://www.xbrl.org/2003/role/disclosureRef
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Reference 15: http://www.xbrl.org/2003/role/disclosureRef
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Reference 16: http://www.xbrl.org/2003/role/disclosureRef
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Reference 17: http://www.xbrl.org/2003/role/disclosureRef
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Reference 18: http://www.xbrl.org/2003/role/disclosureRef
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Reference 19: http://www.xbrl.org/2003/role/disclosureRef
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+ Details

Share-Based Compensation

9 Months Ended

Sep. 30, 2023

Share-Based Payment Arrangement [Abstract]

Share-Based Compensation

Equity Incentive Plans

The Company’s equity incentive plans, the 2018 Long Term Incentive Plan, as amended (the “2018 LTIP”), 2020 Employment Inducement Incentive Plan, as amended (the “2020 EIIP”), and previously, the Amended and Restated 2012 Long Term Incentive Plan (the “2012 LTIP”), reserve ordinary shares for the issuance of ISOs, NQSOs, SARs, restricted shares, RSUs, performance bonus awards, performance share units awards, dividend equivalents and other share or cash-based awards to eligible individuals. Options granted under each of the 2018 LTIP, 2020 EIIP, and 2012 LTIP expire no later than ten years from the date of grant.

In May 2023, the Company’s shareholders approved an amendment to the 2018 LTIP to increase the number of ordinary shares available for issuance under the 2018 LTIP by 2,000,000 ordinary shares. As of September 30, 2023, the number of ordinary shares authorized under the 2018 LTIP was 14,614,183. Upon adoption of the 2018 LTIP, no new awards are permitted under the 2012 LTIP.

As of September 30, 2023, the number of ordinary shares authorized under the 2020 EIIP was 1,485,000 and 35,834 ordinary shares remained available for future awards under the 2020 EIIP. The Company’s Board of Directors has adopted a

series of amendments to increase the ordinary shares available for issuance under the 2020 EIIP and it reserves the right to both amend the 2020 EIIP to increase the number of ordinary shares available and make additional awards to key new hires.

The Company granted 245,250 and 193,500 options during the three months ended September 30, 2023 and 2022, respectively, and 1,731,621 and 2,219,686 options during the nine months ended September 30, 2023 and 2022, respectively, in aggregate under its equity plans. The Company’s option awards generally vest over four years, while RSUs vest over two years. As of September 30, 2023, 3,556,448 ordinary shares remained available for grant under its equity plans, 27,000 RSUs were outstanding and unvested, and options to purchase 9,939,093 ordinary shares in aggregate under the Company’s equity plans were outstanding with a weighted-average exercise price of approximately $29.15 per share.

Share-based Compensation Expense

The Company estimates the fair value of share-based compensation on the date of grant using an option-pricing model. The Company uses the Black-Scholes model to value share-based compensation, excluding RSUs, which the Company values using the fair market value of its ordinary shares on the date of grant. The Black-Scholes option-pricing model determines the fair value of share-based payment awards based on the share price on the date of grant and is affected by assumptions regarding a number of complex and subjective variables. These variables include, but are not limited to, the Company’s share price, volatility over the expected life of the awards and actual and projected employee stock option exercise behaviors. The simplified method has been used to estimate the expected life of all options in previous years. Beginning January 1, 2023, expected term was estimated based on historical experience. Although the fair value of share options granted by the Company is estimated by the Black-Scholes model, the estimated fair value may not be indicative of the fair value observed in a willing buyer and seller market transaction.

As share-based compensation expense recognized in the Condensed Consolidated Financial Statements is based on awards ultimately expected to vest, it has been reduced for estimated forfeitures. The estimated forfeiture rate as of September 30, 2023 was 8%. Changes in our estimates and assumptions relating to forfeitures may cause us to realize material changes in stock-based compensation expense in the future.

The amount of unearned share-based compensation related to unvested stock options at September 30, 2023, is $100.4 million. The weighted-average period over which the unearned share-based compensation related to stock options is expected to be recognized is 2.58 years.

Share-based compensation expense recorded in these Condensed Consolidated Financial Statements for the three and nine months ended September 30, 2023 and 2022, was based on awards granted under the 2012 LTIP, the 2018 LTIP, and the 2020 EIIP.

The following table summarizes share-based compensation expense for the periods presented (in thousands):


	Three Months Ended September 30,				Nine Months Ended September 30,
	2023		2022		2023		2022
Research and development	$	4,948	$	4,176	$	14,178	$	11,268
General and administrative	5,996		3,790		15,656		12,621
Total share-based compensation expense	$	10,944	$	7,966	$	29,834	$	23,889

The Company recognized tax benefits from share-based awards of $1.9 million and $1.5 million for the three months ended September 30, 2023 and 2022, respectively and $5.3 million and $4.5 million for the nine months ended September 30, 2023 and 2022, respectively.

The fair value of the options granted to employees and non-employee directors during the three and nine months ended September 30, 2023 and 2022 was estimated as of the grant date using the Black-Scholes option-pricing model assuming the weighted-average assumptions listed in the following table:


	Three Months Ended September 30,		Nine Months Ended September 30,
	2023	2022	2023	2022
Expected volatility	76.8%	82.3%	81.3%	82.2%
Risk-free interest rate	4.3%	2.9%	4.2%	2.1%
Expected dividend yield	—%	—%	—%	—%
Expected term (in years)	4.42	6.00	4.81	6.00
Weighted average grant date fair value	$40.83	$20.38	$37.67	$22.53

The fair value of employee stock options is being amortized on a straight-line basis over the requisite service period for each award. Each of the inputs discussed above is subjective and generally requires significant management judgment to determine.

The following table summarizes the Company’s stock option activity during the nine months ended September 30, 2023:


	Options	Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (years)	Aggregate Intrinsic Value (in thousands)
Outstanding at December 31, 2022	9,479,998	$	23.16	6.82	$	354,856
Granted	1,731,621	56.94
Exercised	(1,097,550)	19.05
Forfeited	(174,976)	43.04
Expired	—	—
Outstanding at September 30, 2023	9,939,093	$	29.15	6.84	$	212,009
Vested and expected to vest at September 30, 2023	9,562,960	$	28.48	6.75	$	209,155
Vested at September 30, 2023	6,095,330	$	20.52	5.68	$	172,377

The total intrinsic value of options exercised was $5.7 million and $20.0 million during the three months ended September 30, 2023 and 2022, respectively, and $51.1 million and $22.6 million during the nine months ended September 30, 2023 and 2022, respectively, determined as of the date of exercise.

The following table summarizes the activity and related information for RSUs during the nine months ended September 30, 2023:


	Number of Units	Weighted Average Grant-Date Fair Value	Weighted Average Remaining Contractual Term (years)	Aggregate Intrinsic Value (in thousands)
Outstanding at December 31, 2022	23,000	$60.89	1.67	$1,386
Units Granted	4,000	68.71
Units Vested	—	—
Units Forfeited	—	—
Outstanding at September 30, 2023	27,000	$62.05	1.01	$1,303

The fair value of RSUs was determined on the date of grant based on the market price of the Company’s ordinary shares as of that date. The fair value of the RSUs is recognized as an expense on a straight-line basis over the vesting period of each RSU. Upon the vesting of the RSUs, a portion of the shares vested are sold by the employee to satisfy employee withholding tax requirements (sell-to-cover). The total fair value of shares vested during the nine months ended September 30, 2023 was nil. As of September 30, 2023, total compensation cost not yet recognized related to unvested RSUs was $1.1 million, which is expected to be recognized over a weighted-average period of 1.26 years. RSUs settle into ordinary shares upon vesting.

Income Taxes	9 Months Ended
Income Taxes	Sep. 30, 2023
Income Tax Disclosure [Abstract]
Income Taxes	Income TaxesThe major taxing jurisdictions for the Company are Ireland and the U.S. The Company recorded an income tax benefit of $3.1 million and $10.3 million for the three and nine months ended September 30, 2023 as compared to $2.7 million and $5.7 million for the three and nine months ended September 30, 2022, respectively. The provision for income taxes differs from the statutory tax rate of 12.5% applicable to Ireland primarily due to Irish net operating losses for which a tax provision benefit is not recognized, U.S. income taxed at different rates, adjustments to deferred tax assets for the deductibility of stock compensation and capitalization of research and development costs. The Company has historically computed its interim period provision for (benefit from) income taxes by applying its forecasted effective tax rate to year-to-date earnings. However, due to a significant amount of U.S. permanent differences relative to the amount of U.S. forecasted income used in computing the effective tax rate, the effective tax rate is highly sensitive to minor fluctuations in U.S. forecasted income. As such, the Company has computed the U.S. component of the consolidated provision for (benefit from) income taxes for the three and nine months ended September 30, 2023 using an actual year-to-date tax calculation. The non-U.S. tax expense continues to be zero due to cumulative historic and year-to-date losses and a full valuation allowance on our deferred tax assets in our non-U.S. jurisdictions. Deferred income taxes reflect the net tax effect of temporary differences between the carrying amount of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes. The Company's deferred tax assets (“DTA”) are composed primarily of its Irish subsidiaries' net operating loss carryforwards, California net operating loss carryforwards available to reduce future taxable income of the Company's U.S. subsidiaries, federal and California tax credit carryforwards, share-based compensation, capitalized R&D, and other temporary differences. The Company maintains a valuation allowance against certain U.S. federal and state and Irish deferred tax assets. Each reporting period, the Company evaluates the need for a valuation allowance on its deferred tax assets by jurisdiction. No provision for income tax in Ireland has been recognized on undistributed earnings of the Company’s U.S. subsidiaries as the Company considers the U.S. earnings to be indefinitely reinvested.

- 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

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
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-URI https://asc.fasb.org//1943274/2147480990/946-20-50-13

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-Section S99
-Paragraph 1
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+ Details

Pay vs Performance Disclosure - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
Pay vs Performance Disclosure - USD ($) $ in Thousands	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Sep. 30, 2023	Sep. 30, 2022
Pay vs Performance Disclosure
Net income (loss)	$ 21,907	$ (54,595)	$ (46,864)	$ (45,764)	$ (41,244)	$ (36,290)	$ (79,552)	$ (123,298)

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References

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+ Details

Insider Trading Arrangements	3 Months Ended	9 Months Ended
Insider Trading Arrangements	Sep. 30, 2023 shares	Sep. 30, 2023 shares
Trading Arrangements, by Individual
Non-Rule 10b5-1 Arrangement Adopted	false
Rule 10b5-1 Arrangement Terminated	false
Non-Rule 10b5-1 Arrangement Terminated	false
Dennis J. Selkoe [Member]
Trading Arrangements, by Individual
Material Terms of Trading Arrangement		On August 10, 2023, Dennis J. Selkoe, director, adopted a Rule 10b5-1 trading arrangement that is intended to satisfy the affirmative defense of Rule 10b5-1(c) for the sale of up to 20,000 shares of the Company’s ordinary shares until November 15, 2024.
Name	Dennis J. Selkoe
Title	director
Rule 10b5-1 Arrangement Adopted	true
Adoption Date	August 10, 2023
Arrangement Duration	463 days
Aggregate Available	20,000	20,000
Michael J. Malecek [Member]
Trading Arrangements, by Individual
Material Terms of Trading Arrangement		On August 8, 2023, Michael J. Malecek, Chief Legal Officer, adopted a Rule 10b5-1 trading arrangement that is intended to satisfy the affirmative defense of Rule 10b5-1(c) for the sale of up to 88,000 shares of the Company’s ordinary shares until November 30, 2024.
Name	Michael J. Malecek
Title	Chief Legal Officer
Rule 10b5-1 Arrangement Adopted	true
Adoption Date	August 8, 2023
Arrangement Duration	480 days
Aggregate Available	88,000	88,000

Summary of Significant Accounting Policies (Policies)	9 Months Ended
Summary of Significant Accounting Policies (Policies)	Sep. 30, 2023
Accounting Policies [Abstract]
Basis of Preparation and Presentation of Financial Information	Basis of Preparation and Presentation of Financial Information These accompanying Unaudited Interim Condensed Consolidated Financial Statements have been prepared in accordance with the accounting principles generally accepted in the U.S. (“GAAP”) and with the instructions for Form 10-Q and Regulation S-X statements. Accordingly, they do not include all of the information and notes required for complete financial statements. These interim Condensed Consolidated Financial Statements should be read in conjunction with the Consolidated Financial Statements and Notes thereto contained in the Company’s Annual Report on Form 10-K filed with the U.S. Securities and Exchange Commission (the “SEC”) on February 28, 2023 (the “2022 Form 10-K”). These Unaudited Interim Condensed Consolidated Financial Statements are presented in U.S. dollars, which is the functional currency of the Company and its consolidated subsidiaries. These Unaudited Interim Condensed Consolidated Financial Statements include the accounts of the Company and its consolidated subsidiaries. All intercompany balances and transactions have been eliminated in consolidation. Unaudited Interim Financial Information The accompanying Unaudited Interim Condensed Consolidated Financial Statements and related disclosures are unaudited, have been prepared on the same basis as the annual consolidated financial statements and, in the opinion of management, reflect all adjustments, which include only normal recurring adjustments, necessary for a fair presentation of the results of operations for the periods presented. The year-end condensed consolidated balance sheet data was derived from audited financial statements, however certain information and footnote disclosures normally included in financial statements prepared in accordance with GAAP have been condensed or omitted. The condensed consolidated results of operations for any interim period are not necessarily indicative of the results to be expected for the full year or for any other future year or interim period.
Use of Estimates	Use of Estimates The preparation of the Condensed Consolidated Financial Statements in conformity with GAAP requires management to make judgments, estimates and assumptions that affect the reported amounts of assets, liabilities, revenues and expenses, and related disclosures. On an ongoing basis, management evaluates its estimates, including critical accounting policies or estimates related to revenue recognition, leases and research and development expenses. The Company bases its estimates on historical experience and on various other market specific and other relevant assumptions that management believes to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities that are not readily apparent from other sources. Because of the uncertainties inherent in such estimates, actual results may differ materially from these estimates.
Segment and Concentration of Risk	Concentration of Credit Risks and Other Risks and Uncertainties Financial instruments that potentially subject the Company to concentration of credit risk consist of cash and cash equivalents. The Company places its cash equivalents with multiple major and reputable financial institutions. To minimize our risk the Company and its subsidiaries invest pursuant to a Board approved investment policy, which specifies credit quality standards for our investments and limits the amount of credit exposure to any single issue, issuer or type of investment. The majority of cash and cash equivalents are invested in liquid money market funds. Cash deposits held with banks may exceed the amount of insurance provided on such deposits. To date, the Company has not experienced any losses on its deposits of cash and cash equivalents. The Company’s business is primarily conducted in U.S. dollars except for its agreements with contract manufacturers for drug supplies which are denominated in Euros. The Company recorded a loss on foreign currency exchange rate differences of approximately $253,000 and $70,000 during the nine months ended September 30, 2023 and 2022, respectively. If the Company increases its business activities that require the use of foreign currencies, it may be exposed to losses if the Euro and other such currencies continue to strengthen against the U.S. dollar. As of September 30, 2023, and December 31, 2022, approximately $2.4 million and $1.7 million, respectively, of the Company’s property and equipment, net were held in the U.S. and nominal amount were in Ireland. The Company is subject to a number of risks similar to other late-stage clinical biotechnology companies, including, but not limited to, the need to obtain adequate additional funding, possible failure of current or future preclinical testing or clinical trials, its reliance on third parties to conduct its clinical trials, the need to obtain regulatory and marketing approvals for its drug candidates, competitors developing new technological innovations, the need to successfully commercialize and gain market acceptance of the Company’s drug candidates, its right to develop and commercialize its drug candidates pursuant to the terms and conditions of the licenses granted to the Company, protection of proprietary technology, and the need to secure and maintain adequate clinical trial management, manufacturing, packaging, labeling, storage, testing, and distribution arrangements with third parties. The Company also relies on third-party consultants to assist in managing these third parties and assist with its clinical trial operations and manufacturing. If the Company does not successfully commercialize or partner any of its drug candidates, it will be unable to generate product revenue or achieve profitability. Further, the Company is also subject to broad market risks and uncertainties resulting from recent events, such as the COVID-19 pandemic, the Russian invasion of Ukraine, inflation, rising interest rates, and recession risks, as well as supply chain and labor shortages. Segments The Company operates in one segment. The Company’s chief operating decision maker (the “CODM”), its Chief Executive Officer, manages the Company’s operations on a consolidated basis for purposes of allocating resources. When evaluating the Company’s financial performance, the CODM reviews all financial information on a consolidated basis.
Recent Accounting Pronouncements	Recent Accounting Pronouncements There were no new accounting pronouncements or changes to accounting pronouncements during the three and nine months ended September 30, 2023 that are of significance or potential significance to the Company.

Composition of Certain Balance Sheet Items (Tables)

9 Months Ended

Sep. 30, 2023

Composition of Certain Balance Sheet Items [Abstract]

Schedule of Prepaid and Other Current Assets


	September 30,		December 31,
	2023		2022
Prepaid R&D expenses	$	7,927	$	5,325
Prepaid G&A expenses	2,218		1,597
Receivable from stock option exercises in-transit	—		62
Other	3,051		1,708
Prepaid and other current assets	$	13,196	$	8,692

Schedule of Property and Equipment

Property and equipment, net consisted of the following (in thousands):


	September 30,		December 31,
	2023		2022
Machinery and equipment	$	10,863	$	9,901
Leasehold improvements	1,498		1,498
Purchased computer software	1,892		1,500
	14,253		12,899
Less: accumulated depreciation and amortization	(11,820)		(11,168)
Property and equipment, net	$	2,433	$	1,731

Schedule of Other Current Liabilities

Other current liabilities consisted of the following (in thousands):


	September 30,		December 31,
	2023		2022
Payroll and related expenses	$	10,670	$	11,060
Professional services	1,259		605
Other	1,847		503
Other current liabilities	$	13,776	$	12,168

Net Income (Loss) Per Ordinary Share (Tables)

9 Months Ended

Sep. 30, 2023

Earnings Per Share [Abstract]

Calculation of Basic and Diluted Net Income (Loss) Per Ordinary Share

Net income (loss) per ordinary share was determined as follows (in thousands, except per share amounts):


	Three Months Ended September 30,				Nine Months Ended September 30,
	2023		2022		2023		2022
Numerator:
Net income (loss)	$	21,907	$	(45,764)	$	(79,552)	$	(123,298)
Denominator:
Weighted-average ordinary shares outstanding used in per share calculations - basic	53,559		46,986		53,064		46,833
Weighted-average ordinary shares outstanding used in per share calculations - diluted	58,004		46,986		53,064		46,833
Net income (loss) per share:
Basic net income (loss) per ordinary share	$	0.41	$	(0.97)	$	(1.50)	$	(2.63)
Diluted net income (loss) per ordinary share	$	0.38	$	(0.97)	$	(1.50)	$	(2.63)

Ordinary Shares Equivalent Not Included in Diluted Net Income (Loss) Per Ordinary Share

The equivalent ordinary shares not included in diluted net income (loss) per share because their effect would be anti-dilutive are as follows (in thousands):


	Three Months Ended September 30,		Nine Months Ended September 30,
	2023	2022	2023	2022
Stock options to purchase ordinary shares	2,110	10,019	9,939	10,019
Restricted Stock Units (RSU)	27	—	27	—
Total	2,137	10,019	9,966	10,019

Commitments and Contingencies (Tables)

9 Months Ended

Sep. 30, 2023

Commitments and Contingencies Disclosure [Abstract]

Schedule of lease liability maturity analysis and future minimum rentals to be received

Future minimum payments under the above-described noncancelable operating leases, including a reconciliation to the lease liabilities recognized in the Condensed Consolidated Balance Sheets, and future minimum rentals to be received under the Sub-Sublease as of September 30, 2023, are as follows (in thousands):


Year Ended December 31,	Operating Leases		Sub-Sublease Rental
2023 (3 months)	1,713		672
2024	2,828		—
2025	3,052		—
2026	3,158		—
2027	3,269		—
Thereafter	2,523		—
Total	$	16,543	$	672
Less: Present value adjustment	(5,808)
Lease liability	$	10,735

Schedule of Contractual Obligations by Fiscal Year Maturity

The following is a summary of the Company's non-cancelable purchase commitments and contractual obligations as of September 30, 2023 (in thousands):


	Total		2023		2024		2025		2026		2027		Thereafter
Purchase Obligations (1)	$	14,584	$	14,426	$	122	$	36	$	—	$	—	$	—
Contractual obligations under license agreements	402		64		64		64		60		60		90
Total	$	14,986	$	14,490	$	186	$	100	$	60	$	60	$	90

________________

(1) Purchase obligations consist of non-cancelable purchase commitments to suppliers and contract research organizations.

Share-Based Compensation (Tables)

9 Months Ended

Sep. 30, 2023

Share-Based Payment Arrangement [Abstract]

Summary of Share-Based Compensation Expense

The following table summarizes share-based compensation expense for the periods presented (in thousands):


	Three Months Ended September 30,				Nine Months Ended September 30,
	2023		2022		2023		2022
Research and development	$	4,948	$	4,176	$	14,178	$	11,268
General and administrative	5,996		3,790		15,656		12,621
Total share-based compensation expense	$	10,944	$	7,966	$	29,834	$	23,889

Fair Value of Options Granted

The fair value of the options granted to employees and non-employee directors during the three and nine months ended September 30, 2023 and 2022 was estimated as of the grant date using the Black-Scholes option-pricing model assuming the weighted-average assumptions listed in the following table:


	Three Months Ended September 30,		Nine Months Ended September 30,
	2023	2022	2023	2022
Expected volatility	76.8%	82.3%	81.3%	82.2%
Risk-free interest rate	4.3%	2.9%	4.2%	2.1%
Expected dividend yield	—%	—%	—%	—%
Expected term (in years)	4.42	6.00	4.81	6.00
Weighted average grant date fair value	$40.83	$20.38	$37.67	$22.53

Summary of Company's Share Option Activity

The following table summarizes the Company’s stock option activity during the nine months ended September 30, 2023:


	Options	Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (years)	Aggregate Intrinsic Value (in thousands)
Outstanding at December 31, 2022	9,479,998	$	23.16	6.82	$	354,856
Granted	1,731,621	56.94
Exercised	(1,097,550)	19.05
Forfeited	(174,976)	43.04
Expired	—	—
Outstanding at September 30, 2023	9,939,093	$	29.15	6.84	$	212,009
Vested and expected to vest at September 30, 2023	9,562,960	$	28.48	6.75	$	209,155
Vested at September 30, 2023	6,095,330	$	20.52	5.68	$	172,377

Share-Based Payment Arrangement, Outstanding Award, Activity, Excluding Option

The following table summarizes the activity and related information for RSUs during the nine months ended September 30, 2023:


	Number of Units	Weighted Average Grant-Date Fair Value	Weighted Average Remaining Contractual Term (years)	Aggregate Intrinsic Value (in thousands)
Outstanding at December 31, 2022	23,000	$60.89	1.67	$1,386
Units Granted	4,000	68.71
Units Vested	—	—
Units Forfeited	—	—
Outstanding at September 30, 2023	27,000	$62.05	1.01	$1,303

Organization - Additional Information (Detail) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022	Sep. 30, 2022
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Accumulated deficit	$ (912,555)	$ (833,003)
Cash and cash equivalents	$ 670,897	$ 710,406	$ 495,628

- Definition

Amount of accumulated undistributed earnings (deficit).

+ References + Details

Summary of Significant Accounting Policies - Additional Information (Details)	9 Months Ended
	Sep. 30, 2023 USD ($) segment	Sep. 30, 2022 USD ($)	Dec. 31, 2022 USD ($)
Significant accounting policies [line item]
Foreign Currency Transactions Gain (Loss)	$ (253,000)	$ (70,000)
Property and equipment, net	$ 2,433,000		$ 1,731,000
Number of operating segments \| segment	1
UNITED STATES
Significant accounting policies [line item]
Property and equipment, net	$ 2,433,000		1,700,000
IRELAND
Significant accounting policies [line item]
Property and equipment, net	$ 0		$ 0

Fair Value Measurements - Additional Information (Detail) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Level 1
Fair Value Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds at carrying value	$ 647.1	$ 599.1

Composition of Certain Balance Sheet Items - Schedule of Property and Equipment (Detail) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Composition of Certain Balance Sheet Items [Abstract]
Machinery and equipment	$ 10,863	$ 9,901
Leasehold improvements	1,498	1,498
Purchased computer software	1,892	1,500
Property and equipment, gross	14,253	12,899
Less: accumulated depreciation and amortization	(11,820)	(11,168)
Property and equipment, net	$ 2,433	$ 1,731

Composition of Certain Balance Sheet Items - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Composition of Certain Balance Sheet Items [Abstract]
Depreciation expense	$ 0.2	$ 0.2	$ 0.7	$ 0.5

Composition of Certain Balance Sheet Items - Schedule of Other Current Liabilities (Detail) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Composition of Certain Balance Sheet Items [Abstract]
Payroll and related expenses	$ 10,670	$ 11,060
Professional services	1,259	605
Other	1,847	503
Other current liabilities	$ 13,776	$ 12,168

Composition of Certain Balance Sheet Items - Schedule of Prepaid Expenses and Other Current Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Composition of Certain Balance Sheet Items [Abstract]
Prepaid R&D expenses	$ 7,927	$ 5,325
Prepaid G&A expenses	2,218	1,597
Receivable from stock option exercises in-transit	0	62
Other	3,051	1,708
Prepaid expenses and other current assets	$ 13,196	$ 8,692

Net Income (Loss) Per Ordinary Share - Calculation of Basic and Diluted Net Income (Loss) Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Sep. 30, 2023	Sep. 30, 2022
Numerator:
Net income (loss)	$ 21,907	$ (54,595)	$ (46,864)	$ (45,764)	$ (41,244)	$ (36,290)	$ (79,552)	$ (123,298)
Denominator:
Weighted-average ordinary shares outstanding used in per share calculations- basic (in shares)	53,559			46,986			53,064	46,833
Weighted-average ordinary shares outstanding used in per share calculations- diluted (in shares)	58,004			46,986			53,064	46,833
Net Income (Loss) Per Share, Basic and Diluted
Basic (in dollars per share)	$ 0.41			$ (0.97)			$ (1.50)	$ (2.63)
Diluted (in dollars per share)	$ 0.38			$ (0.97)			$ (1.50)	$ (2.63)

- Definition

The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

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-URI https://asc.fasb.org//1943274/2147482810/280-10-50-32

Reference 31: http://www.xbrl.org/2003/role/disclosureRef
-Topic 260
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 60B
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482689/260-10-45-60B

Reference 32: http://www.xbrl.org/2003/role/exampleRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 31
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-31

Reference 33: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 32
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-32

Reference 34: http://www.xbrl.org/2003/role/disclosureRef
-Topic 205
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 7
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483499/205-20-50-7

Reference 35: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 230
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 28
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482740/230-10-45-28

Reference 36: http://www.xbrl.org/2003/role/disclosureRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 1A
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482790/220-10-45-1A

Reference 37: http://www.xbrl.org/2003/role/disclosureRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 1B
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482790/220-10-45-1B

Reference 38: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(20))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483621/220-10-S99-2

Reference 39: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 942
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04(22))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483589/942-220-S99-1

+ Details

Net Income (Loss) Per Ordinary Share - Ordinary Shares Equivalent Not Included in Diluted Net Income (Loss) Per Share (Detail) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Equivalent ordinary shares not included in diluted net income (loss) per share(in shares)	2,137,000	10,019,000	9,966,000	10,019,000
Stock options to purchase ordinary shares
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Equivalent ordinary shares not included in diluted net income (loss) per share(in shares)	2,110,000	10,019,000	9,939,000	10,019,000
Restricted Stock Units (RSU)
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Equivalent ordinary shares not included in diluted net income (loss) per share(in shares)	27,000	0	27,000	0

Commitment and Contingencies - Lease Narrative (Details)			1 Months Ended		3 Months Ended		9 Months Ended
	Sep. 24, 2018	Jul. 18, 2018 USD ($) ft²	Apr. 30, 2016 USD ($)	Mar. 31, 2016 ft²	Sep. 30, 2023 USD ($)	Sep. 30, 2022 USD ($)	Sep. 30, 2023 USD ($)	Sep. 30, 2022 USD ($)	Apr. 19, 2023	Apr. 11, 2023	Aug. 01, 2021
Lease Description [Line Items]
Operating lease, future minimum payments due					$ 16,543,000		$ 16,543,000
South San Francisco, California
Lease Description [Line Items]
Operating lease (area) \| ft²				128,751
Operating lease, weighted average remaining lease term					3 months		3 months
Lease expiration date				Dec. 31, 2023
Operating lease cost					$ 1,600,000	$ 1,600,000	$ 4,800,000	$ 4,800,000
Operating lease, payments					$ 1,600,000	1,600,000	$ 4,900,000	4,700,000
Discount rate, percent					4.25%		4.25%
Area of sub-sublease rental \| ft²		46,641
Sublease income					$ 700,000	$ 700,000	$ 2,200,000	$ 2,200,000
Sub-sublease rentals, initial annual base rent		$ 2,700,000
Sub-sublease rentals, percent annual rent increase		3.50%
Sub-sublease rentals, term of contract	5 years 2 months 12 days
Sub-sublease rentals, percent of rental gain attributable to sublandlord		50.00%
Term of contract (in years)				7 years 9 months 30 days
Dublin, Ireland
Lease Description [Line Items]
Operating lease, Dublin, term of contract (in years)									1 year		1 year
Operating lease, Dublin, renewal term of contract (in years)										1 year
Letter of Credit \| South San Francisco, California
Lease Description [Line Items]
Line of credit facility			$ 4,100,000
Face amount reduction on third anniversary			1,400,000
Face amount reduction on fifth anniversary			$ 1,400,000
Line of credit has been used					0		0
Restricted cash					$ 1,400,000		$ 1,400,000

Commitment and Contingencies - New Brisbane Facility (Details)		3 Months Ended	9 Months Ended
	Oct. 28, 2022 USD ($) ft²	Sep. 30, 2023 USD ($)	Sep. 30, 2023 USD ($)	Jul. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)
Lease Description [Line Items]
Operating lease, future minimum payments due		$ 16,543,000	$ 16,543,000
Operating lease right-of-use assets		12,629,000	12,629,000		$ 6,277,000
Lease liability		$ 10,735,000	$ 10,735,000
Brisbane, California
Lease Description [Line Items]
Operating lease (area) \| ft²	31,157
Operating lease, future minimum payments due	$ 14,900,000
Operating lease, weighted average remaining lease term		5 years	5 years
Operating lease right-of-use assets				$ 11,400,000
Lease liability				$ 3,600,000
Discount rate, percent				5.76%
Tenant improvement allowance	9,300,000
Tenant improvement allowance received			$ 5,500,000
Operating lease cost		$ 500,000	500,000
Operating lease, payments		200,000	200,000
Brisbane, California \| Standby Letters of Credit
Lease Description [Line Items]
Restricted cash	$ 900,000
Line of credit has been used		$ 0	$ 0

Commitment and Contingencies - Schedule of Lease Liability Maturity Analysis and Future Minimum Rentals to be Received - (Details) $ in Thousands	Sep. 30, 2023 USD ($)
Operating Lease
2023 (3 months)	$ 1,713
2024	2,828
2025	3,052
2026	3,158
2027	3,269
Thereafter	2,523
Total	16,543
Less: Present value adjustment	(5,808)
Lease liability	10,735
Sub-Sublease Rental
2023 (3 months)	672
2024	0
2025	0
2026	0
2027	0
Thereafter	0
Total	$ 672

Commitment and Contingencies - Commitment Narrative (Details)
$ in Thousands

Sep. 30, 2023

USD ($)

Long-term Purchase Commitment [Line Items]

Purchase obligation

$ 14,584

^[1]

Contractual obligations under license agreements

400

Accrued Current Liabilities

Long-term Purchase Commitment [Line Items]

Commitment to suppliers included in accrued current liabilities

8,300

Contractual obligations under license agreements included in accrued current liabilities

$ 15

[1]	Purchase obligations consist of non-cancelable purchase commitments to suppliers and contract research organizations.

Commitment and Contingencies - Contractual Obligations (Details)
$ in Thousands

Sep. 30, 2023

USD ($)

Purchase Obligations

Total

$ 14,584

^[1]

2023

14,426

^[1]

2024

122

^[1]

2025

36

^[1]

2026

0

^[1]

2027

0

^[1]

Thereafter

0

^[1]

Contractual obligations under license agreements

Total

400

Total

14,986

14,490

186

100

60

60

90

License Agreements [Member]

Contractual obligations under license agreements

402

64

64

64

60

60

$ 90

[1]	Purchase obligations consist of non-cancelable purchase commitments to suppliers and contract research organizations.

Significant Agreements - Roche License Agreement (Details) - USD ($) $ in Thousands		1 Months Ended			3 Months Ended		9 Months Ended
	May 05, 2021	Jun. 30, 2017	May 31, 2014	Feb. 28, 2014	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
License Agreement [Line Items]
Accounts receivable					$ 5,159		$ 5,159		$ 0
Collaboration revenue					84,866	$ 1,517	$ 91,054	$ 3,982
Collaborative Arrangement
License Agreement [Line Items]
Portion of revenue and expenses attributable to company, Percentage							30.00%
Roche
License Agreement [Line Items]
Milestone achievement, Clinical milestone	$ 60,000
Revenue, Remaining performance obligation, Amount					0		$ 0		$ 0
Roche \| Collaborative Arrangement
License Agreement [Line Items]
Collaboration revenue, License, Upfront payment				$ 30,000
Milestone payment received, Clinical milestone			$ 15,000
Milestone achievement, Clinical milestone		$ 30,000
Potential payment upon achievement of development, regulatory and various first commercial sales milestones							290,000
Potential payment for achievement of non U.S. commercial sales milestones							$ 175,000
Portion of revenue and expenses attributable to company, Percentage							70.00%
Potential alternative commercial sales milestones							$ 155,000
License agreement, Cost allocation, Percentage							100.00%
Collaboration revenue
License Agreement [Line Items]
Collaboration revenue					$ 84,866	$ 1,517	$ 91,004	$ 3,932

Significant Agreements - Bristol Myers Squibb Collaboration Agreement (Details)				3 Months Ended		9 Months Ended
	Jul. 05, 2023 USD ($)	Jul. 30, 2021 USD ($)	Mar. 20, 2018 USD ($) agreement_term $ / shares shares	Sep. 30, 2023 USD ($)	Sep. 30, 2022 USD ($)	Sep. 30, 2023 USD ($)	Sep. 30, 2022 USD ($)	Jun. 30, 2023 USD ($)	Dec. 31, 2022 USD ($)
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Deferred revenue, current				$ 316,000		$ 316,000			$ 11,442,000
Collaboration revenue				84,866,000	$ 1,517,000	91,054,000	$ 3,982,000
Accounts receivable				5,159,000		5,159,000			0
Deferred revenue, non-current				67,405,000		67,405,000			85,293,000
Collaboration Program, US Rights
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Collaboration agreement, potential regulatory milestone payments per program			$ 90,000,000
Collaboration agreement, potential commercial milestone payments per program			375,000,000
Collaboration Program, US Rights \| Minimum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Collaboration agreement, expected allocation of initial transaction price			15,000,000
Collaboration Program, US Rights \| Maximum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Collaboration agreement, expected allocation of initial transaction price			25,000,000
Collaboration Program, Global Rights
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Collaboration agreement, potential regulatory milestone payments per program			187,500,000
Collaboration agreement, potential commercial milestone payments per program			375,000,000
Collaboration Program, Global Rights \| Minimum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Collaboration agreement, expected allocation of initial transaction price			10,000,000
Collaboration Program, Global Rights \| Maximum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Collaboration agreement, expected allocation of initial transaction price			18,000,000
Collaboration revenue
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Collaboration revenue				84,866,000	1,517,000	91,004,000	3,932,000
BMS (formerly Celgene)
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Collaboration agreement, upfront payment			$ 100,000,000
BMS (formerly Celgene) \| Private Placement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Share subscription agreement, number of ordinary shares issued in transaction (in shares) \| shares			1,174,536
Share subscription agreement, price per share (in dollars per share) \| $ / shares			$ 42.57
Share subscription agreement, consideration received on transaction			$ 50,000,000
Bristol Myers Squibb
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Collaboration agreement, potential regulatory and commercial milestone payments per program			$ 562,500,000
Collaboration agreement, term of agreement			6 years
Collaboration agreement, number of additional 12 month period extension allowed \| agreement_term			2
Collaboration agreement, extension fee per extension period			$ 10,000,000
Collaboration revenue				84,900,000	$ 1,500,000	91,000,000	$ 3,900,000
Deferred Revenue				67,700,000		67,700,000		$ 92,500,000
Deferred revenue, non-current				67,400,000		67,400,000
Bristol Myers Squibb \| Collaboration Program, US Rights
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Collaboration agreement, exercise fee per program			80,000,000
Deferred revenue, current				300,000		300,000
Bristol Myers Squibb \| Collaboration Program, Global Rights
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Collaboration agreement, exercise fee per program			55,000,000
Bristol Myers Squibb \| Collaboration Revenue, US License
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Allocated consideration to performance obligations		$ 77,500,000
Bristol Myers Squibb \| Collaboration Revenue, US Development Services
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Allocated consideration to performance obligations		27,500,000
Bristol Myers Squibb \| Collaboration Program, Tau/ PRX005
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Collaboration Agreement, Allocation of Initial Transaction Price			$ 24,900,000
Collaboration Agreement, Total Transaction Price, PRX005 US		104,900,000
Collaboration Program, PRX005 US License Agreement, Upfront Payment		$ 80,000,000
Bristol Myers Squibb \| US Rights and Global Rights
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Deferred Revenue				67,400,000		67,400,000
Bristol Myers Squibb \| Collaboration Program, Global, Tau/ PRX005
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Collaboration agreement, potential regulatory and commercial milestone payments per program	$ 562,500,000
Collaboration Agreement, Allocation of Initial Transaction Price	17,900,000
Collaboration Program, Global Exercise Fee	55,000,000
Collaboration Agreement, Total Transaction Price, PRX005 Global	$ 72,900,000
Bristol Myers Squibb \| Supply Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Collaboration Revenue, Transaction Price				4,700,000		4,700,000
BMS (formerly Celgene)
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Collaboration agreement, option fees and milestone payments, payment term			30 days
BMS (formerly Celgene) \| Private Placement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Share subscription agreement, premium received on transaction			$ 10,200,000
Collaborative Arrangement \| Bristol Myers Squibb
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Accounts receivable				5,200,000		5,200,000			$ 0
Collaborative Arrangement \| BMS (formerly Celgene)
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Collaboration agreement, Initial transaction price			$ 110,200,000
Collaboration Program, Tau/ PRX005 \| Bristol Myers Squibb
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Collaboration revenue				6,900,000
Revenue, Remaining performance obligation, Amount				$ 300,000		$ 300,000

Significant Agreements - Novo Nordisk Share Purchase Agreement (Details) - USD ($)		1 Months Ended	9 Months Ended
	Jul. 08, 2021	Dec. 31, 2022	Sep. 30, 2023	Sep. 30, 2022
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Accounts receivable		$ 0	$ 5,159,000
Novo Nordisk
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Accounts receivable		0	0
Share Purchase Agreement, Upfront Payment	$ 60,000,000
Share Purchase Agreement, Potential Payment Upon Achievement of Development and Sales Milestones			1,130,000,000
Revenue from License and Intellectual Property, Share Purchase Agreement			$ 0	$ 0
Milestone achievement, Clinical milestone		$ 40,000,000
Novo Nordisk \| Transition services
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Revenue from License and Intellectual Property, Share Purchase Agreement	$ 700,000

Shareholders' Equity - Additional Information (Details)	9 Months Ended
Shareholders' Equity - Additional Information (Details)	Sep. 30, 2023 vote € / shares shares	Sep. 30, 2023 $ / shares shares	Dec. 31, 2022 € / shares shares	Dec. 31, 2022 $ / shares shares
Equity [Abstract]
Ordinary shares, number of authorized shares (in shares)	100,000,000	100,000,000	100,000,000	100,000,000
Ordinary shares, par value (in dollars per share) \| $ / shares		$ 0.01		$ 0.01
Ordinary shares, number of issued shares (in shares)	53,638,615	53,638,615	52,103,608	52,103,608
Ordinary shares, number of outstanding shares (in shares)	53,638,615	53,638,615	52,103,608	52,103,608
Euro deferred shares, number of shares authorized (in shares)	10,000	10,000	10,000	10,000
Euro deferred shares, nominal value (in euros per share) \| € / shares	€ 22		€ 22
Euro deferred shares, number of outstanding shares (in shares)	0	0	0	0
Number of Votes \| vote	1

Shareholders' Equity - December 2022 Public Offering - (Details) - Underwritten Public Offering - USD ($) $ / shares in Units, $ in Millions	Jan. 18, 2023	Dec. 19, 2022
Sale of Ordinary Shares [Line Items]
Price per share at public offering (in dollars per share)		$ 56.50
Ordinary Shares
Sale of Ordinary Shares [Line Items]
Issuance of ordinary shares (in shares)	395,096	3,250,000
Proceeds from issuance of ordinary shares in public offering, net	$ 20.9	$ 172.4
Underwritten Public Offering, Maximum Number Of Shares, Underwriters Option to Purchase		487,500

Shareholders' Equity - At-the-Market Offering (Details) - USD ($)		3 Months Ended	9 Months Ended
	Dec. 23, 2021	Sep. 30, 2023	Sep. 30, 2023
Sale of Ordinary Shares [Line Items]
Common stock, cumulative number of shares issued (in shares)		953,589	953,589
Proceeds from issuance of common stock, cumulative gross amount		$ 56,300,000	$ 56,300,000
Stock issuance costs, cumulative amount		$ 1,800,000	1,800,000
December 2021 At-The-Market Offering
Sale of Ordinary Shares [Line Items]
Stock Issuance Costs			$ 100,000
Ordinary Shares \| December 2021 At-The-Market Offering
Sale of Ordinary Shares [Line Items]
Maximum proceeds from sale of ordinary shares	$ 250,000,000
Issuance of ordinary shares (in shares)		0	42,361
Proceeds from issuance of common stock, cumulative gross amount		$ 3,200,000	$ 3,200,000

Share-Based Compensation - Additional Information (Details) - USD ($)		3 Months Ended		9 Months Ended
	May 16, 2023	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Share-based Payment [Line Items]
Number of shares available for grant (in shares)		3,556,448		3,556,448
Grant period				10 years
Options, granted (in shares)		245,250	193,500	1,731,621	2,219,686
Vesting period (in years)				4 years
Options outstanding (in shares)		9,939,093		9,939,093		9,479,998
Weighted average exercise price (in dollars per share)		$ 29.15		$ 29.15		$ 23.16
Tax benefit recognized from share-based compensation expense		$ 1,900,000	$ 1,500,000	$ 5,300,000	$ 4,500,000
Share-Based Payment Arrangement, Estimated Forfeiture Rate		8.00%		8.00%
Restricted Stock Units (RSU)
Share-based Payment [Line Items]
Vesting period (in years)				2 years
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Number		27,000		27,000		23,000
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition				1 year 3 months 3 days
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value		$ 62.05		$ 62.05		$ 60.89
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Vested in Period, Fair Value		$ 0		$ 0
Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount		1,100,000		1,100,000
Stock options to purchase ordinary shares
Share-based Payment [Line Items]
Share-based Payment Arrangement, Nonvested Award, Option, Cost Not yet Recognized, Amount		100,400,000		$ 100,400,000
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition				2 years 6 months 29 days
Intrinsic value of options exercised		$ 5,700,000	$ 20,000,000	$ 51,100,000	$ 22,600,000
2018 Long Term Incentive Plan
Share-based Payment [Line Items]
Number of additional shares authorized (in shares)	2,000,000
Authorized shares for issuance (in shares)		14,614,183		14,614,183
2020 Employment Inducement Incentive Plan
Share-based Payment [Line Items]
Authorized shares for issuance (in shares)		1,485,000		1,485,000
Number of shares available for grant (in shares)		35,834		35,834

Share-Based Compensation - Summary of Share-Based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	$ 10,944	$ 7,966	$ 29,834	$ 23,889
Research and development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	4,948	4,176	14,178	11,268
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	$ 5,996	$ 3,790	$ 15,656	$ 12,621

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 35
-Paragraph 1D
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480483/718-10-35-1D

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 35
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480483/718-10-35-3

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)(1)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)(2)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)(3)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(i)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(ii)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iii)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iv)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480429/718-10-50-2

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iv)(01)
-Publisher FASB
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+ Details

Share-Based Compensation - Fair Value of Options Granted (Details) - $ / shares	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Share-Based Payment Arrangement [Abstract]
Expected volatility	76.80%	82.30%	81.30%	82.20%
Risk-free interest rate	4.30%	2.90%	4.20%	2.10%
Expected dividend yield	0.00%	0.00%	0.00%	0.00%
Expected life (in years)	4 years 5 months 1 day	6 years	4 years 9 months 21 days	6 years
Weighted average fair value (in dollars per share)	$ 40.83	$ 20.38	$ 37.67	$ 22.53

Share-based Compensation - Share-based Compensation Plan - Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Share-Based Payment, Options, Outstanding [Roll Forward]
Options, outstanding beginning balance (in shares)			9,479,998
Options, granted (in shares)	245,250	193,500	1,731,621	2,219,686
Options, exercised (in shares)			(1,097,550)
Options, forfeited (in shares)			(174,976)
Options, expired (in shares)			0
Options, outstanding ending balance (in shares)	9,939,093		9,939,093		9,479,998
Options, vested and expected to vest ending balance (in shares)	9,562,960		9,562,960
Options, Vested (in shares)			6,095,330
Share-Based Payment, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Weighted average exercise price, outstanding beginning balance (in dollars per share)			$ 23.16
Weighted average exercise price, granted (in dollars per share)			56.94
Weighted average exercise price, exercised (in dollars per share)			19.05
Weighted average exercise price, forfeited (in dollars per share)			43.04
Weighted average exercise price, expired (in dollars per share)			0
Weighted average exercise price, outstanding ending balance (in dollars per share)	$ 29.15		29.15		$ 23.16
Weighted average exercise price, vested and expected to vest, ending balance (in dollars per share)	28.48		28.48
Weighted Average Exercise Price, vested (in dollars per shares)	$ 20.52		$ 20.52
Share-Based Payment, Options, Additional Disclosures [Abstract]
Weighted average remaining contractual term, outstanding (in years)			6 years 10 months 2 days		6 years 9 months 25 days
Weighted average remaining contractual term, vested and expected to vest (in years)			6 years 9 months
Weighted Average Remaining Contractual Term, vested (in years)			5 years 8 months 4 days
Aggregate intrinsic value, outstanding	$ 212,009		$ 212,009		$ 354,856
Aggregate intrinsic value, vested and expected to vest, ending balance	209,155		209,155
Aggregate intrinsic value, vested	$ 172,377		$ 172,377

Share-Based Compensation - RSUs Activity (Details) - Restricted Stock Units (RSU) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2023	Dec. 31, 2022
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Number	27,000	23,000
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value	$ 62.05	$ 60.89
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period	4,000
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value	$ 68.71
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Vested in Period	0
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value	$ 0
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Forfeited in Period	0
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value	$ 0
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Outstanding, Weighted Average Remaining Contractual Terms	1 year 3 days	1 year 8 months 1 day
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Aggregate Intrinsic Value, Outstanding	$ 1,303	$ 1,386

Income Taxes - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Income Taxes [Line Items]
Income tax expense (benefit)	$ (3,092)	$ (2,653)	$ (10,310)	$ (5,652)
Revenue Commissioners, Ireland
Income Taxes [Line Items]
Effective income tax rate, percent			12.50%

- Definition

Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

+ References + Details