ALNYLAM PHARMACEUTICALS, INC., 10-Q filed on 10/29/2026
Quarterly Report
v3.26.3
Cover Page - shares
 9 Months Ended
Sep. 30, 2026
Oct. 23, 2026
Cover [Abstract]    
Document Type 10-Q  
Document Quarterly Report true  
Document Period End Date Sep. 30, 2026  
Document Transition Report false  
Entity File Number 001-36407  
Entity Registrant Name ALNYLAM PHARMACEUTICALS, INC.  
Entity Incorporation, State or Country Code DE  
Entity Tax Identification Number 77-0602661  
Entity Address, Address Line One 675 West Kendall Street,  
Entity Address, Address Line Two Henri A. Termeer Square  
Entity Address, City or Town Cambridge  
Entity Address, State or Province MA  
Entity Address, Postal Zip Code 02142  
City Area Code 617  
Local Phone Number 551-8200  
Title of 12(b) Security Common Stock, $0.01 par value per share  
Trading Symbol ALNY  
Security Exchange Name NASDAQ  
Entity Current Reporting Status Yes  
Entity Interactive Data Current Yes  
Entity Filer Category Large Accelerated Filer  
Entity Small Business false  
Entity Emerging Growth Company false  
Entity Shell Company false  
Entity Common Stock, Shares Outstanding   133,937,576
Amendment Flag false  
Document Fiscal Year Focus 2026  
Current Fiscal Year End Date --12-31  
Document Fiscal Period Focus Q3  
Entity Central Index Key 0001178670  
v3.26.3
CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($)
$ in Thousands
Sep. 30, 2026
Dec. 31, 2025
Current assets:    
Cash and cash equivalents $ 1,754,340 $ 1,657,250
Marketable debt securities 1,832,915 1,251,234
Accounts receivable, net 1,084,905 777,567
Inventory 105,907 82,719
Prepaid expenses and other current assets 334,597 281,892
Total current assets 5,112,664 4,050,662
Property, plant and equipment, net 614,910 513,147
Operating lease right-of-use assets 177,950 194,916
Deferred tax assets 2,006,669 125,975
Restricted investments 22,172 22,170
Other assets 60,307 59,461
Total assets 7,994,672 4,966,331
Current liabilities:    
Accounts payable 135,399 115,721
Accrued expenses 1,236,289 1,080,197
Operating lease liabilities 46,083 45,518
Deferred revenue 11,669 4,845
Convertible debt 361,529 0
Liabilities related to the sale of future royalties and development funding 272,037 220,068
Total current liabilities 2,063,006 1,466,349
Operating lease liabilities, net of current portion 203,294 225,087
Convertible debt, net of current portion 651,087 1,007,784
Liabilities related to the sale of future royalties and development funding, net of current portion 1,462,828 1,470,341
Other liabilities 10,605 7,594
Total liabilities 4,390,820 4,177,155
Commitments and contingencies (Note 12)
Stockholders' equity:    
Preferred stock, $0.01 par value per share, 5,000 shares authorized and no shares issued and outstanding as of September 30, 2026 and December 31, 2025 0 0
Common stock, $0.01 par value per share, 250,000 shares authorized; 133,875 shares issued and outstanding as of September 30, 2026; 132,376 shares issued and outstanding as of December 31, 2025 1,339 1,324
Additional paid-in capital 7,811,878 7,510,473
Accumulated other comprehensive loss (44,661) (20,097)
Accumulated deficit (4,164,704) (6,702,524)
Total stockholders' equity 3,603,852 789,176
Total liabilities and stockholders' equity $ 7,994,672 $ 4,966,331
v3.26.3
CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares
Sep. 30, 2026
Dec. 31, 2025
Statement of Financial Position [Abstract]    
Preferred stock, par value (in dollars per share) $ 0.01 $ 0.01
Preferred stock, shares authorized (in shares) 5,000,000 5,000,000
Preferred stock, shares issued (in shares) 0 0
Preferred stock, shares outstanding (in shares) 0 0
Common stock, par value (in dollars per share) $ 0.01 $ 0.01
Common stock, shares authorized (in shares) 250,000,000 250,000,000
Common stock, shares issued (in shares) 133,875,000 132,376,000
Common stock, shares outstanding (in shares) 133,875,000 132,376,000
v3.26.3
CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE (LOSS) INCOME - USD ($)
shares in Thousands, $ in Thousands
 3 Months Ended 9 Months Ended
Sep. 30, 2026
Sep. 30, 2025
Sep. 30, 2026
Sep. 30, 2025
Revenues:        
Total revenues $ 1,458,086 $ 1,249,026 $ 3,916,209 $ 2,616,904
Operating costs and expenses:        
Cost of goods sold 361,750 197,231 867,531 409,443
Cost of collaborations and royalties 0 2,923 3,792 4,705
Research and development 408,538 358,814 1,186,538 947,557
Selling, general and administrative 342,000 322,076 1,012,473 885,339
Total operating costs and expenses 1,112,288 881,044 3,070,334 2,247,044
Income from operations 345,798 367,982 845,875 369,860
Other (expense) income:        
Interest expense (84,372) (67,462) (235,709) (187,227)
Interest income 30,941 28,681 85,682 84,840
Loss related to convertible debt 0 (39,146) 0 (39,146)
Other income (expense), net 3,443 (9,487) (579) 8,564
Total other expense, net (49,988) (87,414) (150,606) (132,969)
Income before income taxes 295,810 280,568 695,269 236,891
Benefit from (provision for) income taxes 1,871,525 12,115 1,842,551 (34,687)
Net income $ 2,167,335 $ 292,683 $ 2,537,820 $ 202,204
Net income per common share — basic (in dollars per share) $ 16.19 $ 2.23 $ 19.02 $ 1.55
Net income per common share — diluted (in dollars per share) $ 15.72 $ 2.14 $ 18.42 $ 1.51
Weighted-average common shares - basic (in shares) 133,828 131,447 133,444 130,590
Weighted-average common shares - diluted (in shares) 138,040 137,348 138,184 134,146
Statements of Comprehensive Income        
Net income $ 2,167,335 $ 292,683 $ 2,537,820 $ 202,204
Other comprehensive (loss) income:        
Unrealized (losses) gains on marketable securities (11,811) 1,131 (19,098) 1,818
Foreign currency translation (losses) gains (801) 6,993 (5,733) 10,764
Defined benefit pension plans, net of tax 89 53 267 161
Total other comprehensive (loss) income (12,523) 8,177 (24,564) 12,743
Comprehensive income 2,154,812 300,860 2,513,256 214,947
Net product revenues        
Revenues:        
Total revenues 1,291,946 851,082 3,500,182 1,991,832
Net revenues from collaborations        
Revenues:        
Total revenues 71,476 351,742 200,716 512,423
Royalty revenue        
Revenues:        
Total revenues $ 94,664 $ 46,202 $ 215,311 $ 112,649
v3.26.3
CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS’ EQUITY - USD ($)
shares in Thousands, $ in Thousands
Total
Cumulative Effect, Period of Adoption, Adjustment
Common Stock
Additional Paid-in Capital
Accumulated Other Comprehensive Loss
Accumulated Deficit
Accumulated Deficit
Cumulative Effect, Period of Adoption, Adjustment
Beginning balance (in shares) at Dec. 31, 2024     129,294        
Beginning balance at Dec. 31, 2024 $ 67,088 $ 271,477 $ 1,293 $ 7,388,061 $ (34,518) $ (7,287,748) $ 271,477
Increase (Decrease) in Stockholders' Equity [Roll Forward]              
Exercise of common stock options, net of tax withholdings (in shares)     423        
Exercise of common stock options, net of tax withholdings 50,985   $ 4 50,981      
Issuance of common stock under equity plans (in shares)     594        
Issuance of common stock under equity plans 0   $ 6 (6)      
Stock-based compensation 57,840     57,840      
Other comprehensive income (loss) (2,999)       (2,999)    
Net income (loss) (18,251)         (18,251)  
Ending balance (in shares) at Mar. 31, 2025     130,311        
Ending balance at Mar. 31, 2025 426,140   $ 1,303 7,496,876 (37,517) (7,034,522)  
Beginning balance (in shares) at Dec. 31, 2024     129,294        
Beginning balance at Dec. 31, 2024 67,088 $ 271,477 $ 1,293 7,388,061 (34,518) (7,287,748) $ 271,477
Increase (Decrease) in Stockholders' Equity [Roll Forward]              
Purchases of capped calls related to convertible senior notes 35,311            
Other comprehensive income (loss) 12,743            
Net income (loss) 202,204            
Ending balance (in shares) at Sep. 30, 2025     131,791        
Ending balance at Sep. 30, 2025 580,247   $ 1,318 7,414,771 (21,775) (6,814,067)  
Beginning balance (in shares) at Mar. 31, 2025     130,311        
Beginning balance at Mar. 31, 2025 426,140   $ 1,303 7,496,876 (37,517) (7,034,522)  
Increase (Decrease) in Stockholders' Equity [Roll Forward]              
Exercise of common stock options, net of tax withholdings (in shares)     556        
Exercise of common stock options, net of tax withholdings 81,061   $ 6 81,055      
Issuance of common stock under equity plans (in shares)     110        
Issuance of common stock under equity plans 0   $ 1 (1)      
Stock-based compensation 112,807     112,807      
Other comprehensive income (loss) 7,565       7,565    
Net income (loss) (72,228)         (72,228)  
Ending balance (in shares) at Jun. 30, 2025     130,977        
Ending balance at Jun. 30, 2025 555,345   $ 1,310 7,690,737 (29,952) (7,106,750)  
Increase (Decrease) in Stockholders' Equity [Roll Forward]              
Exercise of common stock options, net of tax withholdings (in shares)     625        
Exercise of common stock options, net of tax withholdings 80,420   $ 6 80,414      
Issuance of common stock under equity plans (in shares)     189        
Issuance of common stock under equity plans 0   $ 2 (2)      
Stock-based compensation 109,339     109,339      
Purchases of capped calls related to convertible senior notes (430,406)     (430,406)      
Purchase of capped calls related to —% Convertible Senior Notes due 2028 (35,311)     (35,311)      
Other comprehensive income (loss) 8,177       8,177    
Net income (loss) 292,683         292,683  
Ending balance (in shares) at Sep. 30, 2025     131,791        
Ending balance at Sep. 30, 2025 $ 580,247   $ 1,318 7,414,771 (21,775) (6,814,067)  
Beginning balance (in shares) at Dec. 31, 2025 132,376   132,376        
Beginning balance at Dec. 31, 2025 $ 789,176   $ 1,324 7,510,473 (20,097) (6,702,524)  
Increase (Decrease) in Stockholders' Equity [Roll Forward]              
Exercise of common stock options, net of tax withholdings (in shares)     102        
Exercise of common stock options, net of tax withholdings 13,751   $ 1 13,750      
Issuance of common stock under equity plans (in shares)     966        
Issuance of common stock under equity plans 0   $ 9 (9)      
Stock-based compensation 71,259     71,259      
Other comprehensive income (loss) (4,797)       (4,797)    
Net income (loss) 205,991         205,991  
Ending balance (in shares) at Mar. 31, 2026     133,444        
Ending balance at Mar. 31, 2026 $ 1,075,380   $ 1,334 7,595,473 (24,894) (6,496,533)  
Beginning balance (in shares) at Dec. 31, 2025 132,376   132,376        
Beginning balance at Dec. 31, 2025 $ 789,176   $ 1,324 7,510,473 (20,097) (6,702,524)  
Increase (Decrease) in Stockholders' Equity [Roll Forward]              
Purchases of capped calls related to convertible senior notes 0            
Other comprehensive income (loss) (24,564)            
Net income (loss) $ 2,537,820            
Ending balance (in shares) at Sep. 30, 2026 133,875   133,875        
Ending balance at Sep. 30, 2026 $ 3,603,852   $ 1,339 7,811,878 (44,661) (4,164,704)  
Beginning balance (in shares) at Mar. 31, 2026     133,444        
Beginning balance at Mar. 31, 2026 1,075,380   $ 1,334 7,595,473 (24,894) (6,496,533)  
Increase (Decrease) in Stockholders' Equity [Roll Forward]              
Exercise of common stock options, net of tax withholdings (in shares)     182        
Exercise of common stock options, net of tax withholdings 33,758   $ 2 33,756      
Issuance of common stock under equity plans (in shares)     108        
Issuance of common stock under equity plans 0   $ 1 (1)      
Stock-based compensation 87,730     87,730      
Other comprehensive income (loss) (7,244)       (7,244)    
Net income (loss) 164,494         164,494  
Ending balance (in shares) at Jun. 30, 2026     133,734        
Ending balance at Jun. 30, 2026 1,354,118   $ 1,337 7,716,958 (32,138) (6,332,039)  
Increase (Decrease) in Stockholders' Equity [Roll Forward]              
Exercise of common stock options, net of tax withholdings (in shares)     103        
Exercise of common stock options, net of tax withholdings 14,700   $ 2 14,698      
Issuance of common stock under equity plans (in shares)     38        
Stock-based compensation 80,222     80,222      
Other comprehensive income (loss) (12,523)       (12,523)    
Net income (loss) $ 2,167,335         2,167,335  
Ending balance (in shares) at Sep. 30, 2026 133,875   133,875        
Ending balance at Sep. 30, 2026 $ 3,603,852   $ 1,339 $ 7,811,878 $ (44,661) $ (4,164,704)  
v3.26.3
CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($)
$ in Thousands
 9 Months Ended
Sep. 30, 2026
Sep. 30, 2025
Cash flows from operating activities:    
Net income $ 2,537,820 $ 202,204
Adjustments to reconcile net income to net cash provided by operating activities:    
Depreciation and amortization 41,928 42,152
Non-cash interest expense on liabilities related to the sale of future royalties and development funding 226,646 176,235
Stock-based compensation expense 235,897 276,603
Realized and unrealized loss on marketable equity securities 0 2,306
Loss on extinguishment of debt 0 39,146
Deferred income taxes (1,882,763) 24,972
Other 7,845 (31,464)
Changes in operating assets and liabilities:    
Accounts receivable, net (313,300) (544,210)
Inventory (2,131) 22,335
Prepaid expenses and other assets (102,099) (46,734)
Accounts payable, accrued expenses and other liabilities (18,454) 195,745
Deferred revenue 6,824 (52,940)
Net cash provided by operating activities 738,213 306,350
Cash flows from investing activities:    
Purchases of property, plant and equipment (126,345) (35,405)
Purchases of marketable securities (1,346,894) (1,069,170)
Sales and maturities of marketable securities 753,177 1,580,220
Proceeds from maturity of restricted and other investments 68,425 59,775
Purchases of restricted and other investments (22,000) (59,775)
Other investing activities (27,100) (2,150)
Net cash (used in) provided by investing activities (700,737) 473,495
Cash flows from financing activities:    
Proceeds from issuance of 0.00% Convertible Senior Notes due 2028, net 0 646,372
Purchases of capped calls related to 0.00% Convertible Senior Notes due 2028 0 (35,311)
Repayment of 1.00% Convertible Senior Notes due 2027 0 (1,102,659)
Payment of issuance costs for revolving credit agreement 0 (2,414)
Proceeds from exercise of stock options and other types of equity, net 62,183 208,327
Proceeds from liabilities related to the sale of future royalties and development funding 18,000 0
Repayment of liabilities related to the sale of future royalties and development funding (9,865) (10,647)
Other financing activities (16) 0
Net cash provided by (used in) financing activities 70,302 (296,332)
Effect of exchange rate changes on cash, cash equivalents and restricted cash (10,768) 40,637
Net increase in cash, cash equivalents and restricted cash 97,010 524,150
Cash, cash equivalents and restricted cash, beginning of period 1,658,807 968,652
Cash, cash equivalents and restricted cash, end of period 1,755,817 1,492,802
Supplemental disclosure of cash flows:    
Cash paid for interest 195,565 159,565
Cash paid for taxes 29,810 2,375
Operating lease right-of-use assets obtained in exchange for new operating lease liabilities 457 12,379
Supplemental disclosure of noncash investing activities:    
Capital expenditures included in accounts payable and accrued expenses $ 29,227 $ 9,604
v3.26.3
CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS’ EQUITY (DEFICIT) (Parenthetical)
 12 Months Ended
Dec. 31, 2024
Accounting Standards Update [Extensible Enumeration] Accounting Standards Update 2025-07 [Member]
v3.26.3
CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Parenthetical) - Convertible debt
 9 Months Ended
Sep. 12, 2022
Sep. 30, 2026
2028 Notes    
Interest rate (as percent)   0.00%
Convertible Senior Notes Due 2027    
Interest rate (as percent) 1.00% 1.00%
v3.26.3
NATURE OF BUSINESS
 9 Months Ended
Sep. 30, 2026
Organization, Consolidation and Presentation of Financial Statements [Abstract]  
NATURE OF BUSINESS
1. NATURE OF BUSINESS
Alnylam Pharmaceuticals, Inc. (also referred to as Alnylam, the Company, we, our or us) commenced operations on June 14, 2002 as a biopharmaceutical company seeking to develop and commercialize novel therapeutics based on ribonucleic acid interference, or RNAi. We are committed to the advancement of our company strategy of building a multi-product, global, commercial biopharmaceutical company with a deep and sustainable clinical pipeline of RNAi therapeutics for future growth and a robust, organic research engine for sustainable innovation and great potential for patient impact. Since inception, we have focused on discovering, developing and commercializing RNAi therapeutics by establishing and maintaining a strong intellectual property position in the RNAi field, establishing strategic collaborations with leading pharmaceutical and life sciences companies, generating revenues through licensing agreements, and ultimately developing and commercializing RNAi therapeutics globally, either independently or with our strategic collaborators. We have devoted substantially all of our efforts to business planning, research, development, manufacturing and commercializing biopharmaceutical products, acquiring, filing and expanding our intellectual property rights, recruiting our management and technical staff, and raising capital.
As of September 30, 2026, we have six marketed products, including two products that are commercialized by collaborators, and multiple late-stage investigational programs advancing towards potential commercialization. We currently generate worldwide product revenues from four commercialized products, AMVUTTRA, ONPATTRO, GIVLAARI and OXLUMO, primarily in the United States, or U.S., and Europe.
v3.26.3
BASIS OF PRESENTATION AND PRINCIPLES OF CONSOLIDATION
 9 Months Ended
Sep. 30, 2026
Accounting Policies [Abstract]  
BASIS OF PRESENTATION AND PRINCIPLES OF CONSOLIDATION
2. BASIS OF PRESENTATION AND PRINCIPLES OF CONSOLIDATION
The accompanying condensed consolidated financial statements of Alnylam are unaudited and have been prepared in accordance with accounting principles generally accepted in the United States of America, or GAAP, applicable to interim periods and, in the opinion of management, include all normal and recurring adjustments that are necessary to state fairly the results of operations for the reported periods. Our condensed consolidated financial statements have also been prepared on a basis substantially consistent with, and should be read in conjunction with, our audited consolidated financial statements for the year ended December 31, 2025, which were included in our Annual Report on Form 10-K that was filed with the Securities and Exchange Commission on February 12, 2026. The year-end condensed consolidated balance sheet data was derived from our audited financial statements but does not include all disclosures required by GAAP. The results of our operations for any interim period are not necessarily indicative of the results of our operations for any other interim period or for a full fiscal year.
The accompanying condensed consolidated financial statements reflect the operations of Alnylam and our wholly-owned subsidiaries. All intercompany accounts and transactions have been eliminated. We evaluate variable interests in a variable interest entity, or VIE, and consolidate VIEs when we are the primary beneficiary. Determination of whether we are the primary beneficiary of each VIE is based on an assessment of whether we possess both (i) the power to direct the activities that most significantly affect the VIE’s economic performance and (ii) the obligation to absorb losses or the right to receive benefits that could be significant to the VIE. We continuously reevaluate the accounting for our VIEs upon the occurrence of events that could change the primary beneficiary conclusion. The maximum risk of loss related to our VIEs is generally limited to the carrying value of the investment in such entities, but may also include prepaid expenses recognized for advances made to a VIE and future funding commitments, if applicable.
Certain prior period amounts in the condensed consolidated financial statements have been retrospectively adjusted to reflect the guidance of Accounting Standards Update, or ASU, 2025-07, Derivatives Scope Refinements and Scope Clarification for Share-Based Noncash Consideration from a Customer in a Revenue Contract, which we adopted in the fourth quarter of 2025 on a modified retrospective basis as of January 1, 2025. Refer to Note 2 of the Notes to Consolidated Financial Statements included in our Annual Report on Form 10-K for the year ended December 31, 2025.
Our significant accounting policies are described in Note 2 of the Notes to Consolidated Financial Statements included in our Annual Report on Form 10-K for the year ended December 31, 2025. There have been no material changes to our significant accounting policies during the nine months ended September 30, 2026.
Use of Estimates
The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities as of the date of the condensed consolidated financial statements and the reported amounts of revenues and expenses during the reporting period. In our condensed consolidated financial statements, we use estimates and assumptions related to our inventory valuation and related reserves, clinical accruals, liabilities related to the sale of future royalties and development funding, income taxes, deferred tax asset valuation allowances, revenue recognition and related allowances and reserves, research and development expenses, and stock-based compensation expense. We base our estimates on historical experience and on various other
assumptions that we believe to be reasonable. Actual results could differ from those estimates. Changes in estimates are reflected in reported results in the period in which they become known.
Liquidity
Based on our current operating plan, we believe that our cash, cash equivalents, marketable securities, as well as the revenue we expect to generate from product sales and under our existing collaborations, including royalties on sales of Leqvio and Qfitlia, and available borrowing capacity under the revolving credit agreement, or the Revolving Credit Agreement, as of September 30, 2026, will be sufficient to satisfy our near-term capital and operating needs for at least the next 12 months from the filing date of this Quarterly Report on Form 10-Q. Please refer to Note 8, Convertible Debt and Other Financing, for further information related to the Revolving Credit Agreement.
Recent Accounting Pronouncements
In September 2025, the Financial Accounting Standards Board, or FASB, issued ASU 2025-06, Targeted Improvements to the Accounting for Internal-Use Software, which modernizes the guidance for internal-use software costs by increasing the operability of the recognition guidance considering different methods of software development. The standard will be effective for annual reporting periods beginning after December 15, 2027, as well as interim reporting periods within those annual reporting periods, with early adoption permitted. The standard updates may be applied on a prospective, retrospective, or modified retrospective approach. We are currently evaluating the impact this guidance could have on our condensed consolidated financial statements and related disclosures.
In November 2024, the FASB issued ASU 2024-03, Disaggregation of Income Statement Expenses, or ASU 2024-03, which is intended to improve disclosures by requiring additional information about specific expense categories in the notes to the financial statements on an annual and interim basis. Additionally, in January 2025, the FASB issued ASU 2025-01, clarifying that ASU 2024-03 will be effective for annual reporting periods beginning after December 15, 2026 and interim reporting periods beginning after December 15, 2027, with early adoption permitted. The standard updates may be applied on either a prospective or retrospective basis. We are currently evaluating the disclosure requirements related to ASU 2024-03.
v3.26.3
NET PRODUCT REVENUES
 9 Months Ended
Sep. 30, 2026
Revenue from Contract with Customer [Abstract]  
NET PRODUCT REVENUES
3. NET PRODUCT REVENUES
Net product revenues, classified based on the geographic region in which the product is sold and by franchise (“TTR,” which includes AMVUTTRA and ONPATTRO, and “Rare,” which includes GIVLAARI and OXLUMO) consisted of the following:
Three Months Ended September 30,Nine Months Ended September 30,
(In thousands)2026202520262025
AMVUTTRA
United States$908,596 $530,347 $2,420,229 $1,089,657 
Europe130,718 111,944 363,041 284,900 
Rest of World91,049 43,012 248,786 112,691 
Total1,130,363 685,303 3,032,056 1,487,248 
ONPATTRO
United States9,705 12,480 29,734 50,105 
Europe4,762 19,678 17,835 67,465 
Rest of World5,129 6,917 10,969 23,532 
Total19,596 39,075 58,538 141,102 
Total TTR
1,149,959 724,378 3,090,594 1,628,350 
GIVLAARI
United States57,459 50,426 164,550 149,371 
Europe20,872 18,706 65,485 58,216 
Rest of World11,156 4,742 23,610 14,104 
Total89,487 73,874 253,645 221,691 
OXLUMO
United States18,429 20,727 53,939 50,855 
Europe23,213 22,346 70,281 65,259 
Rest of World10,858 9,757 31,723 25,677 
Total52,500 52,830 155,943 141,791 
Total Rare
141,987 126,704 409,588 363,482 
Total net product revenues$1,291,946 $851,082 $3,500,182 $1,991,832 
As of September 30, 2026 and December 31, 2025, net product revenue-related receivables of $906.2 million and $669.5 million, respectively, were included in accounts receivable, net on our condensed consolidated balance sheets.
The following table summarizes balances and activity in each product revenue allowance and reserve category:
(In thousands)Chargebacks and Rebates
Other Incentives and Allowances
Total
Beginning balance as of December 31, 2025
$399,853 $25,797 $425,650 
Provision related to current year sales
968,692 95,819 1,064,511 
Provision related to prior years’ sales
(6,045)(992)(7,037)
Credit or payments made during the period for current year sales
(598,591)(71,712)(670,303)
Credit or payments made during the period for prior years’ sales
(239,525)(16,323)(255,848)
Total as of September 30, 2026
$524,384 $32,589 $556,973 
v3.26.3
COLLABORATIONS
 9 Months Ended
Sep. 30, 2026
Organization, Consolidation and Presentation of Financial Statements [Abstract]  
COLLABORATIONS
4. COLLABORATIONS
Product Collaborations
Net revenues from collaborations consisted of the following:
Three Months Ended September 30,Nine Months Ended September 30,
(In thousands)2026202520262025
Roche
$39,107 $326,604 $116,636 $361,927 
Regeneron Pharmaceuticals32,334 22,542 83,690 106,123 
Other35 2,596 390 44,373 
Total net revenues from collaborations
$71,476 $351,742 $200,716 $512,423 
The following table presents the balance of our receivables and contract liabilities related to our collaboration agreements:
(In thousands)As of September 30, 2026As of December 31, 2025
Receivables included in accounts receivable, net
$89,603 $48,823 
Contract liabilities included in deferred revenue$11,669 $4,845 
We recognized net revenues from collaborations of $4.0 million and $4.8 million in the three and nine months ended September 30, 2026, respectively, and $12.5 million and $53.6 million in the three and nine months ended September 30, 2025, respectively, each of which was included in the contract liability balance at the beginning of the applicable period.
To determine revenue recognized in the period from contract liabilities, we first allocate revenue to the individual contract liability balance outstanding at the beginning of the period until the revenue exceeds that balance. If additional consideration is received on those contracts in subsequent periods, we assume all revenue recognized in the reporting period first applies to the beginning contract liability as opposed to a portion applying to the new consideration for the period.
Roche
On July 21, 2023, or the Effective Date, we entered into a Collaboration and License Agreement, or the Roche Agreement, with F. Hoffmann-La Roche Ltd. and Genentech, Inc., or, collectively, Roche, pursuant to which we and Roche established a worldwide, strategic collaboration for the joint development of zilebesiran. Zilebesiran is our investigational small interfering RNA, or siRNA, therapeutic targeting liver-expressed angiotensinogen, which is currently in Phase 3 clinical development for the treatment of hypertension.
Under the Roche Agreement, we granted to Roche (i) co-exclusive rights to develop zilebesiran worldwide and commercialize zilebesiran in the U.S., referred to as the Co-Commercialization Territory, (ii) exclusive rights to commercialize zilebesiran outside of the U.S., referred to as the Roche Territory, and (iii) non-exclusive rights to manufacture zilebesiran for the development and commercialization of zilebesiran in the Roche Territory.
We lead the global clinical development for zilebesiran. We are responsible for forty percent (40%) and Roche is responsible for the remaining sixty percent (60%) of development costs incurred in the conduct of development activities that support regulatory approval of zilebesiran globally. We and Roche share equally (50/50) all costs incurred in connection with development activities that are conducted to support regulatory approval of zilebesiran solely in the Co-Commercialization
Territory if incremental development activities are needed. Roche is solely responsible for all costs incurred in the conduct of development activities that primarily support regulatory approval in the Roche Territory. Upon regulatory approval, Roche has the exclusive right to commercialize zilebesiran in the Roche Territory and will pay us tiered, low double-digit royalties based on net sales of zilebesiran on a country-by-country basis during the applicable royalty term. We and Roche will co-commercialize zilebesiran in the Co-Commercialization Territory and share equally (50/50) in profits and losses (including commercialization costs).
Roche has the right to terminate the Roche Agreement for any or no reason at all upon prior written notice. In addition, either party may terminate the Roche Agreement for a material breach by, or insolvency of, the other party, subject to a cure period. Unless earlier terminated pursuant to its terms, the Roche Agreement will remain in effect until expiration on a country-by-country basis (a) in the Roche Territory, upon expiration of the applicable royalty term in the applicable country and (b) in the Co-Commercialization Territory, upon expiration of the term of the co-commercialization efforts.
As of the Effective Date, we identified the following promises in the Roche Agreement that were evaluated under the scope of Accounting Standards Codification, or ASC, Topic 606, Revenue from Contracts with Customers, or ASC 606: (i) a co-exclusive license to develop zilebesiran worldwide and commercialize zilebesiran within the Co-Commercialization Territory, a non-exclusive license to manufacture zilebesiran in the Roche Territory solely for purposes of developing and commercializing zilebesiran in the Roche Territory, and an exclusive license to commercialize zilebesiran in the Roche Territory, collectively referred to as the Roche License Obligation, (ii) development services, including the manufacture of clinical supply, that support regulatory approval of zilebesiran, referred to as the Roche Development Services Obligation, and (iii) a technology transfer of the existing manufacturing process for zilebesiran, referred to as the Roche Technology Transfer Obligation. The three performance obligations under the Roche Agreement are collectively referred to as the Roche Performance Obligations.
We determined that the Roche License Obligation, Roche Development Services Obligation and Roche Technology Transfer Obligation were reflective of a vendor-customer relationship and therefore represented performance obligations within the scope of ASC 606. The Roche License Obligation was considered functional intellectual property and distinct from other promises under the contract as Roche can benefit from the licenses on its own or together with other readily available resources. As the licenses were delivered at the same time, they were considered one performance obligation at contract inception. The Roche Development Services Obligation was considered distinct as Roche could benefit from the development services together with the licenses transferred by us at the inception of the agreement. The development services are not expected to significantly modify or customize the initial intellectual property as zilebesiran was in Phase 2 of clinical development at contract inception. The Roche Technology Transfer Obligation was distinct as Roche can benefit from the manufacturing license transferred by us at the inception of the agreement given the advancements of our RNAi platform and our utilization of third-party contract manufacturing organizations to manufacture zilebesiran. Therefore, each represented a separate performance obligation within the contract with a customer under the scope of ASC 606 at contract inception.
We consider the collaborative activities associated with the co-commercialization of zilebesiran in the U.S. to be a separate unit of account within the scope of ASC Topic 808, Collaborative Arrangements, as we and Roche are both active participants in the commercialization activities and are exposed to significant risks and rewards that are dependent on the commercial success of the activities in the arrangement.
Based on the standalone selling prices of each performance obligation as of the Effective Date, we allocated the variable consideration related to the estimated reimbursements for the Roche Development Services Obligation and the Roche Technology Transfer Obligation to each performance obligation as the terms of the variable payment relate specifically to our efforts to satisfy the performance obligation. We allocated the fixed upfront consideration entirely to the Roche License Obligation as the value of the fixed consideration together with the expected value of the remaining development and regulatory milestones, sales-based milestones, and royalties, all of which are either currently constrained at inception or subject to the sales- or usage-based royalty exception, approximates the standalone selling price of the Roche License Obligation. This allocation is consistent with the allocation objective of ASC 606 when considering all of the performance obligations and payment terms in the contract.
The Roche License Obligation was satisfied at a point in time upon transfer of the license to Roche. Control of the licenses was transferred on the Effective Date and Roche could begin to use and benefit from the licenses. Because of this, all consideration allocated to the Roche License Obligation, including the upfront payment, milestones and royalties, is recognized when these amounts are no longer considered fully constrained or when the related sales occur for amounts subject to the sales-or-usage based royalty exception of ASC 606. For the Roche Development Services Obligation, we measure proportional performance over time using an input method based on cost incurred relative to the total estimated cost of the obligation, on a quarterly basis, by determining the proportion of effort incurred as a percentage of total effort we expect to expend. This ratio is applied to the transaction price allocated to the obligation. As all costs in the proportional performance model are allowable for reimbursement from Roche, and the assumptions used to determine the total estimated cost of the obligation are consistent with the assumptions used to determine the transaction price allocated to the obligation, the revenue recognized for this obligation
will approximate 60% of the actual reimbursable cost incurred. Management has applied significant judgment in the process of developing our estimates. We re-evaluate the transaction price as of the end of each reporting period and as of September 30, 2026, the total transaction price was determined to be $1.74 billion.
The following table provides a summary of the transaction price allocated to each performance obligation:
(In thousands)
As of September 30, 2026
Roche License Obligation
$675,000 
Roche Development Services Obligation
1,061,167 
Roche Technology Transfer Obligation
2,000 
$1,738,167 
Net revenues from collaborations recognized under the Roche Agreement consisted of the following:
Three Months Ended September 30,Nine Months Ended September 30,
(In thousands)2026202520262025
Roche License Obligation
$— $300,000 $— $300,000 
Roche Development Services Obligation
$37,557 $25,166 112,196 57,696 
Other
1,550 1,438 4,440 4,231 
Total
$39,107 $326,604 $116,636 $361,927 
As of September 30, 2026, the aggregate amount of the transaction price allocated to the Roche Performance Obligations that was unsatisfied was $792.2 million, which is expected to be recognized through the term of the Roche Agreement based on our input method model as the services are performed. We incurred research and development costs related to our collaboration with Roche of $66.5 million and $201.0 million during the three and nine months ended September 30, 2026, respectively, and $44.8 million and $105.6 million during the three and nine months ended September 30, 2025, respectively.
Regeneron Pharmaceuticals, Inc.
Overview
In 2019, we entered into a global, strategic collaboration with Regeneron Pharmaceuticals, Inc., or Regeneron, to discover, develop and commercialize RNAi therapeutics for a broad range of diseases by addressing therapeutic targets expressed in the eye and central nervous system, or CNS, in addition to a select number of targets expressed in the liver, which we refer to as the Regeneron Collaboration. The Regeneron Collaboration is governed by a Master Agreement, referred to as the Regeneron Master Agreement. In connection with the Regeneron Master Agreement, we and Regeneron entered into (i) a co-co collaboration agreement covering the continued development of cemdisiran, our C5 siRNA, currently in development for C5 complement-mediated diseases, as a monotherapy, or the C5 Co-Co Collaboration Agreement, and (ii) a license agreement to evaluate anti-C5 antibody-siRNA combinations for C5 complement-mediated diseases including evaluating the combination of Regeneron’s pozelimab and cemdisiran, or the C5 License Agreement. The Regeneron Master Agreement, the C5 Co-Co Collaboration Agreement and the C5 License Agreement were accounted for as a single arrangement because the agreements were negotiated together.
In November 2022, Regeneron exercised its right under the C5 Co-Co Collaboration Agreement to opt-out of the further development and commercialization of cemdisiran monotherapy. As a result of Regeneron’s decision to opt-out, the licenses granted to Regeneron under the C5 Co-Co Collaboration Agreement reverted to us, we had the sole right to continue to develop and commercialize cemdisiran monotherapy, and Regeneron no longer shared in the costs on any monotherapy program. Regeneron remained eligible to receive tiered, double-digit royalties on net sales of cemdisiran as a monotherapy.
In June 2024, we entered into an amended and restated C5 License Agreement, or the Amended C5 License Agreement, which terminated the C5 Co-Co Collaboration Agreement and granted Regeneron a worldwide license to cemdisiran as a monotherapy in addition to the license to cemdisiran in combination with anti-C5 antibodies. Through the Amended C5 License Agreement, Regeneron is now solely responsible for development, manufacturing and commercialization of cemdisiran as a monotherapy and in combination with anti-C5 antibodies. As part of the Amended C5 License Agreement, we provided manufacturing technology transfer services for cemdisiran to Regeneron. Regeneron provided us with an upfront payment of $10.0 million, and we will receive certain milestone payments upon receipt of regulatory approval for cemdisiran as a monotherapy, and tiered double-digit royalties on net sales. The Amended C5 License Agreement did not change our rights to receive low double-digit royalties and commercial milestones of up to $325.0 million on any potential product sales if cemdisiran is used as part of a combination product.
Under the terms of the Regeneron Collaboration, we worked exclusively with Regeneron to discover RNAi therapeutics for eye and CNS diseases and a select number of target genes expressed in the liver for an initial research period, or the Initial Research Term. The Initial Research Term expired in May 2026. As a result of such expiration, we will no longer work exclusively with Regeneron to discover RNAi therapeutics for eye and CNS diseases. We will, however, continue to collaborate exclusively with Regeneron on the programs targeting gene targets that were nominated during the Initial Research Term, provided that lead candidates for such targets are designated within two years of the expiration of the Initial Research Term.
Regeneron leads development and commercialization for all programs targeting eye diseases (subject to limited exceptions), entitling us to certain potential milestone and royalty payments pursuant to the terms of a license agreement, the form of which has been agreed upon by the parties. We and Regeneron are alternating leadership on CNS and liver programs, with the lead party retaining global development and commercial responsibility. For such CNS and liver programs, both we and Regeneron have the option at lead candidate selection to enter into a co-co collaboration agreement, the form of which has been agreed upon by the parties, whereby both companies will share equally all costs of, and profits from, all development and commercialization activities under the program. If the non-lead party elects to not enter into a co-co collaboration agreement with respect to a given CNS or liver program, we and Regeneron will enter into a license agreement with respect to such program and the lead party will be the “Licensee” for the purposes of the license agreement. If the lead party for a CNS or liver program elects to not enter into the co-co collaboration agreement, then we and Regeneron will enter into a license agreement with respect to such program and leadership of the program will transfer to the other party and the former non-lead party will be the “Licensee” for the purposes of the license agreement.
In connection with the Regeneron Master Agreement, we remain eligible to receive an additional $100.0 million milestone payment upon achievement of certain criteria during early clinical development for an eye program. We and Regeneron are continuing to advance programs nominated during the Initial Research Term. For each of these programs, Regeneron will provide us with $2.5 million in funding at program initiation and an additional $2.5 million at lead candidate identification.
For any license agreement subsequently entered into, the licensee will generally be responsible for its own costs and expenses incurred in connection with the development and commercialization of the collaboration products. The licensee will pay to the licensor certain development and/or commercialization milestone payments totaling up to $150.0 million for each collaboration product. In addition, following the first commercial sale of the applicable collaboration product under a license agreement, the licensee is required to make certain tiered royalty payments, ranging from low double-digits up to 20%, to the licensor based on the aggregate annual net sales of the collaboration product, subject to customary reductions.
For any co-co collaboration agreement subsequently entered into, we and Regeneron will share equally all costs of, and profits from, development and commercialization activities. Reimbursement of our share of costs will be recognized as a reduction to research and development expense in the condensed consolidated statements of operations and comprehensive income. In the event that a party exercises its opt-out right, the lead party will be responsible for all costs and expenses incurred in connection with the development and commercialization of the collaboration products under the applicable co-co collaboration agreement, subject to continued sharing of costs through defined points. If a party exercises its opt-out right, following the first commercial sale of the applicable collaboration product under a co-co collaboration agreement, the lead party is required to make certain tiered royalty payments, ranging from low double-digits up to 20%, to the other party based on the aggregate annual net sales of the collaboration product and the timing of the exercise of the opt-out right, subject to customary reductions and a reduction for opt-out transition costs.
Contract Modification
In June 2024, we determined the Amended C5 License Agreement does not meet the requirements to account for the contract modification as a separate contract under ASC 606 because the consideration exchanged for the additional distinct goods and services does not reflect the standalone selling price. Therefore, we have accounted for the Amended C5 License Agreement and Regeneron Master Agreement as a single combined contract. The modification date was determined to be the June 2024 effective date of the Amended C5 License Agreement.
Our performance obligations subsequent to the contract modification included: (i) a research license and research services, collectively referred to as the Research Services Obligation; (ii) a worldwide license to cemdisiran for combination therapies, and manufacturing and development service obligations, collectively referred to as the C5 License Obligation; (iii) a worldwide license to cemdisiran for monotherapies, referred to as the C5 Monotherapy Obligation; and (iv) a technology transfer of the existing manufacturing process for cemdisiran, referred to as the Regeneron Technology Transfer Obligation.
The Amended C5 License Agreement did not change the Research Services Obligation or the C5 License Obligation, which were both performance obligations at the inception of our global, strategic collaboration with Regeneron prior to the contract modification. The Amended C5 License Agreement resulted in two additional performance obligations, which were the C5 Monotherapy Obligation and the Regeneron Technology Transfer Obligation. The C5 Monotherapy Obligation was
considered functional intellectual property and distinct from other promises as Regeneron can benefit from the cemdisiran monotherapy license on its own or together with other readily available resources and the license is separately identifiable from the other promises in the contract. The Regeneron Technology Transfer Obligation was distinct as Regeneron can benefit from the cemdisiran monotherapy license transferred by us without the technology transfer given cemdisiran was in an advanced stage of clinical development and our utilization of third-party contract manufacturing organizations to manufacture cemdisiran. Therefore, the C5 Monotherapy Obligation and the Regeneron Technology Transfer Obligation each represented a separate performance obligation.
The initial transaction price of $191.5 million allocated to the C5 Monotherapy Obligation was recognized immediately as this obligation was satisfied at a point in time upon transfer of the license to Regeneron. Control of the license was transferred in June 2024 as Regeneron could begin to use and benefit from the license on its own or together with other readily available resources to generate economic benefit from the license. The remaining variable consideration allocated to the C5 Monotherapy Obligation, including milestones and royalties, will be recognized immediately when these amounts are no longer considered fully constrained or when the related sales occur for amounts subject to the sales-or-usage based royalty exception of ASC 606. In the three months ended March 31, 2025, we completed our obligations related to the C5 License Obligation and the Regeneron Technology Transfer Obligation.
We continue to perform work in satisfaction of the remaining unsatisfied performance obligation, the Research Services Obligation. For this performance obligation, we measure proportional performance over time using an input method based on cost incurred relative to the total estimated costs for each of the identified obligations by determining the proportion of effort incurred as a percentage of total effort we expect to expend. This ratio is applied to the transaction price allocated to the obligation. Management has applied significant judgment in the process of developing our estimates. Any changes to these estimates will be recognized in the period in which they change as a cumulative catch-up. We re-evaluate the transaction price as of the end of each reporting period and as of September 30, 2026, the total transaction price was determined to be $100.5 million related to this obligation. As of September 30, 2026, the aggregate amount of the transaction price that was unsatisfied was $20.9 million, which is expected to be recognized through the term of the Regeneron Collaboration based on our input method model as the services are performed.
Net revenues from collaborations recognized under the Regeneron Collaboration consisted of the following:
Three Months Ended September 30,Nine Months Ended September 30,
(In thousands)2026202520262025
Research Services Obligation
$7,345 $12,540 $13,176 $39,306 
C5 License Obligation
— — — 21,370 
Regeneron Technology Transfer Obligation
— — — 2,431 
Other license programs
24,989 10,002 70,514 43,016 
Total
$32,334 $22,542 $83,690 $106,123 
Revenue recognized for the “Other license programs” relates to twelve separate programs subject to individual agreements with Regeneron.
Deferred revenue is classified as either current or noncurrent in the condensed consolidated balance sheets based on the period the revenue is expected to be recognized. Current deferred revenue was $11.7 million and $4.8 million as of September 30, 2026 and December 31, 2025, respectively, related only to the Research Services Obligation.
We incurred research and development costs related to the Regeneron Collaboration of $9.8 million and $33.0 million during the three and nine months ended September 30, 2026, respectively, and $14.6 million and $46.1 million during the three and nine months ended September 30, 2025, respectively.
Vir Biotechnology, Inc.
In March 2025, we and Vir Biotechnology, Inc., or Vir, entered into an amended and restated collaboration and license agreement, or the Amended Vir Agreement, relating to elebsiran (formerly ALN-HBV02 (VIR-2218)). Vir remains solely responsible for development, manufacturing and commercialization of elebsiran. In connection with execution of the Amended Vir Agreement, Vir made a $30.0 million payment, and we remain entitled to receive milestone payments upon the achievement of specified regulatory and commercial milestones, and royalties on the net sales of elebsiran ranging from low-to-mid teen percentages. Because the license rights have already been delivered and we have no other remaining performance obligations under the Amended Vir Agreement, the $30.0 million payment was recognized within net revenues from collaborations during the three months ended March 31, 2025.
Other Collaborations
In addition to the collaboration agreements discussed above, we have various other collaboration agreements that are not individually significant to our operating results or financial condition at this time. Pursuant to the terms of those agreements, we may be required to pay, or we may receive, additional amounts contingent upon the occurrence of various future events (e.g., upon the achievement of various development and commercial milestones) which in the aggregate could be significant. We may also incur, or be reimbursed for, significant research and development costs. In addition, if any products related to these collaborations are approved for sale, we may be required to pay, or we may receive, royalties on future sales. The payment or receipt of these amounts, however, is contingent upon the occurrence of various future events. Due to the uncertainty of pharmaceutical development and the high historical failure rates generally associated with drug development and commercialization, it is possible we may not receive any such payments under all of our existing collaboration and license agreements, including the agreements described within this note.
Inceptive Nucleics, Inc.
In June 2026, we entered into a collaboration agreement with Inceptive Nucleics, Inc., or Inceptive, that is designed to accelerate the discovery of novel RNAi therapeutics by integrating Inceptive’s generative artificial intelligence, or AI, models with our pipeline, which we refer to as the Inceptive Collaboration. Under the terms of the Inceptive Collaboration, we and Inceptive will jointly conduct multiple research programs to develop drug discovery models. The Inceptive Collaboration will be governed by a joint steering committee. The initial research term of the Inceptive Collaboration is three years and may be extended by mutual agreement of the parties. Inceptive granted to us an exclusive, worldwide, perpetual and irrevocable, royalty-free, transferable, sublicensable license, to certain of its intellectual property to exploit compounds and products developed as part of the Inceptive Collaboration. We have the unilateral right to terminate the Inceptive Collaboration at any time, in its entirety or on a research program-by-research program basis, upon 30 days’ advance written notice to Inceptive.
We also entered into a stock purchase agreement with Inceptive pursuant to which we purchased shares of Inceptive’s preferred stock for a total purchase price of $15.0 million. The preferred shares we purchased represented a mid-single digit ownership interest in the outstanding equity of Inceptive. The investment in preferred stock is a variable interest and Inceptive is a variable interest entity, however, we are not the primary beneficiary as we do not have the power to direct the activities that most significantly impact the economic performance of Inceptive.
The investment in Inceptive’s preferred stock does not have a readily determinable fair value. We recognized the investment at cost and will adjust the carrying value for any impairments, plus or minus changes resulting from observable price changes in orderly transactions for the identical or a similar investment of the same issuer. The investment in preferred stock is recorded in other assets on the condensed consolidated balance sheet as of September 30, 2026.
v3.26.3
FAIR VALUE MEASUREMENTS
 9 Months Ended
Sep. 30, 2026
Fair Value Disclosures [Abstract]  
FAIR VALUE MEASUREMENTS
5. FAIR VALUE MEASUREMENTS
The following tables present information about our financial assets that are measured at fair value on a recurring basis and indicate the fair value hierarchy of the valuation techniques we utilized to determine such fair value:
(In thousands)As of September 30, 2026Quoted Prices in Active Markets
(Level 1)		Significant Observable Inputs
(Level 2)		Significant Unobservable Inputs
(Level 3)
Financial assets
Cash equivalents:
Money market funds$173,768 $173,768 $— $— 
U.S. treasury securities34,948 — 34,948 — 
Commercial paper9,265 — 9,265 — 
Marketable debt securities:
U.S. treasury securities847,996 — 847,996 — 
Corporate notes514,295 — 514,295 — 
U.S. government-sponsored enterprise securities451,805 — 451,805 — 
Commercial paper18,819 — 18,819 — 
Restricted cash (money market funds)570 570 — — 
Total financial assets$2,051,466 $174,338 $1,877,128 $— 
(In thousands)As of December 31, 2025Quoted Prices in Active Markets
(Level 1)		Significant Observable Inputs
(Level 2)		Significant Unobservable Inputs
(Level 3)
Financial assets
Cash equivalents:
Money market funds$140,445 $140,445 $— $— 
U.S. treasury securities18,952 — 18,952 — 
U.S. government-sponsored enterprise securities2,690 — 2,690 — 
Commercial paper1,995 — 1,995 — 
Marketable debt securities:
U.S. treasury securities653,341 — 653,341 — 
Corporate notes333,241 — 333,241 — 
U.S. government-sponsored enterprise securities252,634 — 252,634 — 
Commercial paper7,017 — 7,017 — 
Municipal securities5,001 — 5,001 — 
Restricted cash (money market funds)917 917 — — 
Total financial assets$1,416,233 $141,362 $1,274,871 $— 
During the three and nine months ended September 30, 2026 and 2025, there were no transfers into or out of Level 3 financial assets or liabilities. The carrying amounts reflected on our condensed consolidated balance sheets for cash, accounts receivable, net, other current assets, accounts payable and accrued expenses approximate fair value due to their short-term maturities.
v3.26.3
MARKETABLE DEBT SECURITIES
 9 Months Ended
Sep. 30, 2026
Investments, Debt and Equity Securities [Abstract]  
MARKETABLE DEBT SECURITIES
6. MARKETABLE DEBT SECURITIES
We invest our excess cash balances in marketable debt securities and, at each balance sheet date presented, we classify all of our investments in debt securities as available-for-sale and as current assets as they represent the investment of funds available for current operations. We did not record any impairment charges related to our marketable debt securities during the three and nine months ended September 30, 2026 or 2025.
The following tables summarize our marketable debt securities:
As of September 30, 2026
(In thousands)Amortized
Cost
Gross Unrealized Gains
Gross Unrealized Losses
Fair Value
U.S. treasury securities$890,175 $17 $(7,248)$882,944 
Corporate notes518,707 11 (4,423)514,295 
U.S. government-sponsored enterprise securities455,852 4 (4,051)451,805 
Commercial paper28,132 — (48)28,084 
Total$1,892,866 $32 $(15,770)$1,877,128 
As of December 31, 2025
(In thousands)Amortized
Cost
Gross Unrealized Gains
Gross Unrealized Losses
Fair Value
U.S. treasury securities$670,566 $1,736 $(9)$672,293 
Corporate notes332,104 1,152 (15)333,241 
U.S. government-sponsored enterprise securities254,829 559 (64)255,324 
Commercial paper9,012 — — 9,012 
Municipal securities5,000 1 — 5,001 
Total$1,271,511 $3,448 $(88)$1,274,871 
The fair values of our marketable debt securities by classification in the condensed consolidated balance sheets were as follows:
(In thousands)As of September 30, 2026As of December 31, 2025
Marketable debt securities$1,832,915 $1,251,234 
Cash and cash equivalents44,213 23,637 
Total$1,877,128 $1,274,871 
v3.26.3
OTHER BALANCE SHEET DETAILS
 9 Months Ended
Sep. 30, 2026
Organization, Consolidation and Presentation of Financial Statements [Abstract]  
OTHER BALANCE SHEET DETAILS
7. OTHER BALANCE SHEET DETAILS
Inventory
The components of inventory are summarized as follows:
(In thousands)As of September 30, 2026As of December 31, 2025
Raw materials$18,016 $14,184 
Work in process
58,798 65,122 
Finished goods40,421 32,338 
Total inventory
$117,235 $111,644 
As of September 30, 2026 and December 31, 2025, we had $11.3 million and $28.9 million, respectively, of long-term inventory included within other assets in our condensed consolidated balance sheets as we anticipate it being consumed beyond our normal operating cycle.
Cash, Cash Equivalents and Restricted Cash
The following table provides a reconciliation of cash, cash equivalents and restricted cash reported within our condensed consolidated balance sheets to the totals of these amounts shown in the condensed consolidated statements of cash flows:
As of September 30,
(In thousands)20262025
Cash and cash equivalents$1,754,340 $1,490,249 
Total restricted cash included in other assets1,477 2,553 
Total cash, cash equivalents, and restricted cash shown in the condensed consolidated statements of cash flows
$1,755,817 $1,492,802 
Accumulated Other Comprehensive Loss
The following tables summarize the changes in accumulated other comprehensive loss, by component:
(In thousands)Loss on Investment in Joint Venture
Defined Benefit Pension
Plans, Net of Tax
Unrealized Gains (Losses) from Debt
Securities
Foreign Currency Translation
Adjustment
Total Accumulated Other
Comprehensive Loss
Balance as of December 31, 2025$(32,792)$(3,268)$3,360 $12,603 $(20,097)
Other comprehensive loss before reclassifications
— — (14,214)(5,733)(19,947)
Amounts reclassified from accumulated other comprehensive loss
— 267 (4,884)— (4,617)
Net other comprehensive income (loss)
— 267 (19,098)(5,733)(24,564)
Balance as of September 30, 2026$(32,792)$(3,001)$(15,738)$6,870 $(44,661)
(In thousands)Loss on Investment in Joint Venture
Defined Benefit Pension
Plans, Net of Tax
Unrealized Gains (Losses) from Debt
Securities
Foreign Currency Translation
Adjustment
Total Accumulated Other Comprehensive Loss
Balance as of December 31, 2024$(32,792)$(4,249)$1,544 $979 $(34,518)
Other comprehensive income before reclassifications— — 3,001 10,764 13,765 
Amounts reclassified from accumulated other comprehensive loss
— 161 (1,183)— (1,022)
Net other comprehensive income— 161 1,818 10,764 12,743 
Balance as of September 30, 2025$(32,792)$(4,088)$3,362 $11,743 $(21,775)
Amounts reclassified out of accumulated other comprehensive loss relate to settlements of marketable debt securities and amortization of our pension obligation which are recorded as other income (expense), net in the condensed consolidated statements of operations and comprehensive income.
v3.26.3
CONVERTIBLE DEBT AND OTHER FINANCING
 9 Months Ended
Sep. 30, 2026
Debt Disclosure [Abstract]  
CONVERTIBLE DEBT AND OTHER FINANCING
8. CONVERTIBLE DEBT AND OTHER FINANCING
Convertible Senior Notes Due 2028
On September 8, 2025, we commenced a private offering of $575.0 million in aggregate principal amount of 0.00% convertible senior notes due 2028, or the Initial 2028 Notes. On September 10, 2025, the initial purchasers in such offering exercised their option to purchase an additional $86.3 million in aggregate principal amount of our 0.00% convertible senior notes due 2028, or the Additional 2028 Notes, and together with the Initial 2028 Notes referred to as the 2028 Notes, bringing the total aggregate principal amount of the 2028 Notes issued and outstanding to $661.3 million. The 2028 Notes are our senior unsecured obligations. The 2028 Notes were issued pursuant to an indenture, dated September 12, 2025, or the 2025 Indenture, between us and The Bank of New York Mellon, as trustee. The 2025 Indenture includes customary covenants and sets forth certain events of default after which the 2028 Notes may be declared immediately due and payable and sets forth certain types of bankruptcy or insolvency events of default involving us after which the 2028 Notes become automatically due and payable. The 2028 Notes will mature on September 15, 2028, unless earlier converted, redeemed or repurchased. The 2028 Notes will not bear regular interest.
Before June 15, 2028, noteholders will have the right to convert their 2028 Notes in certain circumstances and during specified periods: (1) during any calendar quarter commencing after the calendar quarter ending on December 31, 2025 (and only during such calendar quarter), if the last reported sale price of our common stock for at least 20 trading days (whether or not consecutive) during a period of 30 consecutive trading days ending on, and including, the last trading day of the immediately preceding calendar quarter is greater than or equal to 130% of the conversion price on each applicable trading day; (2) during the five business day period after any ten consecutive trading day period in which the trading price per $1,000 principal amount of the 2028 Notes for each trading day of that ten consecutive trading day period was less than 98% of the product of the last reported sale price of our common stock and the conversion rate on such trading day; (3) if we call any or all of the 2028 Notes for redemption; or (4) upon the occurrence of specified corporate events. From and after June 15, 2028, the 2028 Notes will be convertible at the option of the noteholders at any time prior to the close of business on the second scheduled trading day immediately preceding the maturity date.
We will settle any conversions of the 2028 Notes by paying or delivering, as applicable, cash, shares of our common stock, or a combination of cash and shares of common stock, at our election. The conversion rate for the 2028 Notes will initially be 1.4923 shares of common stock per $1,000 principal amount of 2028 Notes, which is equivalent to an initial conversion price of approximately $670.11 per share of common stock. The initial conversion price represents a premium of approximately 40% above the U.S. composite volume weighted average price of our common stock from 12:30 p.m. through 4:00 p.m. Eastern Daylight Time on September 9, 2025, which was $478.63 per share. The conversion rate is subject to adjustment under certain circumstances in accordance with the terms of the 2025 Indenture.
We may not redeem the 2028 Notes prior to September 20, 2027. We may redeem for cash all or any portion of the 2028 Notes (subject to certain limitations), at our option, on or after September 20, 2027 and on or prior to the 21st scheduled trading day immediately preceding the maturity date, if the last reported sale price of our common stock has been at least 130% of the conversion price then in effect for at least 20 trading days (whether or not consecutive), including the trading day immediately preceding the date on which we provide notice of redemption, during any 30 consecutive trading day period ending on, and including, the trading day immediately preceding the date on which we provide notice of redemption at a redemption price equal to 100% of the principal amount of the 2028 Notes to be redeemed, plus any accrued and unpaid special interest to, but
excluding, the redemption date. No sinking fund is provided for the 2028 Notes, which means that we are not required to redeem or retire the 2028 Notes periodically.
If we undergo a fundamental change, which includes certain change of control events or a termination of trading of our common stock, then subject to certain conditions, holders may require us to repurchase for cash all or any portion of their notes at a fundamental change repurchase price equal to 100% of the principal amount of the 2028 Notes to be repurchased plus accrued and unpaid special interest. In addition, if specific corporate events occur prior to the maturity date or if we issue a notice of redemption, we will increase the conversion rate by pre-defined amounts for holders who elect to convert their notes in connection with such corporate event. The conditions allowing holders of the 2028 Notes to convert were not met during the quarter ended September 30, 2026.
The 2028 Notes were issued at par. As of September 30, 2026 and December 31, 2025, the 2028 Notes were classified as a long-term liability on the condensed consolidated balance sheets and had a carrying value of $651.1 million and $647.2 million, respectively, representing the outstanding principal amount, net of unamortized issuance costs of $10.2 million and $14.0 million, respectively. The issuance costs are amortized to interest expense over the contractual term of the 2028 Notes. As of September 30, 2026 and December 31, 2025, the estimated fair value of the 2028 Notes was approximately $605.9 million and $637.0 million, respectively, which was determined based on the last actively traded price per $100 of the 2028 Notes (Level 2) on the respective dates. As of September 30, 2026 and December 31, 2025, the effective interest rate of the 2028 Notes was 1%.
We used the net proceeds from the issuance of the 2028 Notes to pay the cost of the 2025 Capped Call Transactions, and the remainder of the net proceeds, together with cash on hand, to repurchase $637.8 million aggregate principal amount of the 2027 Notes, as further discussed below.
2025 Capped Call Transactions
In September 2025, in connection with the pricing of the 2028 Notes, we entered into privately negotiated capped call transactions, or 2025 Capped Call Transactions. The 2025 Capped Call Transactions initially cover, subject to customary anti-dilution adjustments, the number of shares of common stock that underlie the 2028 Notes. The initial cap price of the 2025 Capped Call Transactions is $837.61 per share, and is subject to certain adjustments under the terms of the 2025 Capped Call Transactions.
The 2025 Capped Call Transactions are not part of the terms of the 2028 Notes and are accounted for as separate transactions. As these transactions are indexed to our own stock and are considered equity classified, they are recorded in stockholders’ equity and are not accounted for as derivatives. The cost incurred in connection with the 2025 Capped Call Transactions of $35.3 million was recorded as a reduction to additional paid-in capital on our condensed consolidated balance sheet and the fair value of the capped call instrument is not remeasured each reporting period.
Convertible Senior Notes Due 2027
On September 12, 2022, we commenced a private offering of $900.0 million in aggregate principal amount of 1.00% Convertible Senior Notes due 2027, or the Initial 2027 Notes. On September 13, 2022, the initial purchasers in such offering exercised their option to purchase an additional $135.0 million in aggregate principal amount of our 1.00% Convertible Senior Notes due 2027, or the Additional 2027 Notes, and together with the Initial 2027 Notes collectively referred to as the 2027 Notes, bringing the total aggregate principal amount of the 2027 Notes to $1.04 billion. The 2027 Notes were issued pursuant to an indenture, dated September 15, 2022, or the 2022 Indenture. The 2022 Indenture includes customary covenants and sets forth certain events of default after which the 2027 Notes may be declared immediately due and payable and sets forth certain types of bankruptcy or insolvency events of default involving us after which the 2027 Notes become automatically due and payable. The 2027 Notes were issued at par.
The 2027 Notes will mature on September 15, 2027, unless earlier converted, redeemed or repurchased. The 2027 Notes bear interest at a rate of 1.00% per year payable semiannually in arrears on March 15 and September 15 of each year, beginning on March 15, 2023. The 2027 Notes are convertible at the option of the noteholder on or after June 15, 2027. Prior to June 15, 2027, the 2027 Notes are convertible only under the following circumstances: (1) during any calendar quarter commencing after the calendar quarter ending on December 31, 2022 (and only during such calendar quarter), if the last reported sale price of our common stock for at least 20 trading days (whether or not consecutive) during a period of 30 consecutive trading days ending on, and including, the last trading day of the immediately preceding calendar quarter is greater than or equal to 130% of the conversion price on each applicable trading day; (2) during the five business day period after any ten consecutive trading day period in which the trading price per $1,000 principal amount of the 2027 Notes for each trading day of that ten consecutive trading day period was less than 98% of the product of the last reported sale price of our common stock and the conversion rate of the 2027 Notes on such trading day; (3) if we call any or all of the 2027 Notes for redemption; or (4) upon the occurrence of specific corporate events as set forth in the 2022 Indenture governing the 2027 Notes.
We will settle any conversions of the 2027 Notes by paying or delivering, as applicable, cash, shares of our common stock, or a combination of cash and shares of common stock, at our election. The initial conversion rate for the 2027 Notes is 3.4941 shares of common stock per $1,000 principal amount, which is equivalent to an initial conversion price of approximately $286.20 per share of common stock, which represents a premium of approximately 35% over the last reported sale price of common stock of $212.00 per share on September 12, 2022. The conversion rate is subject to adjustment under certain circumstances in accordance with the terms of the 2022 Indenture. The condition allowing holders of the 2027 Notes to convert was not met in the third quarter of 2026, and the 2027 Notes will not be convertible in the fourth quarter of 2026.
We are able to redeem the 2027 Notes after September 20, 2025. We may redeem for cash equal to 100% of the principal amount of the 2027 Notes being redeemed plus accrued and unpaid interest of all or any portion of the 2027 Notes, at our option, on or after September 20, 2025, if the last reported sale price of our common stock has been at least 130% of the conversion price then in effect for at least 20 trading days (whether or not consecutive) during any 30 consecutive trading day period. As of September 30, 2026, we have not redeemed any of the 2027 Notes under this option.
No sinking fund is provided for the 2027 Notes and therefore we are not required to redeem or retire the 2027 Notes periodically. If we undergo a fundamental change, which includes certain change of control events or a termination of trading of our common stock, then subject to certain conditions, holders may require us to repurchase for cash all or any portion of their 2027 Notes at a fundamental change repurchase price equal to 100% of the principal amount of the 2027 Notes to be repurchased plus accrued and unpaid interest. In addition, if specific corporate events occur prior to the maturity date or if we issue a notice of redemption, we will increase the conversion rate by pre-defined amounts for holders who elect to convert their notes in connection with such corporate event.
In September 2025, concurrently with the pricing of the 2028 Notes, we entered into privately negotiated transactions with certain holders of the 2027 Notes to repurchase for cash $637.8 million aggregate principal amount of the outstanding 2027 Notes for a total repurchase cost (including accrued and unpaid interest of $3.1 million) of approximately $1.11 billion. The repurchase was accounted for as an induced conversion. We recorded an inducement expense of $39.1 million within loss related to convertible debt in the consolidated statements of operations and comprehensive income (loss) for the year ended December 31, 2025 and a charge to additional paid-in capital of $430.4 million within stockholders’ equity.
In December 2025, we entered into privately negotiated transactions with certain holders of the 2027 Notes to repurchase for cash $34.4 million aggregate principal amount of the outstanding 2027 Notes for a total repurchase cost (including accrued and unpaid interest of $0.1 million) of approximately $52.3 million. The repurchase was accounted for as an induced conversion. We recorded an inducement expense of $3.3 million within loss related to convertible debt in the consolidated statements of operations and comprehensive income (loss) for the year ended December 31, 2025 and a charge to additional paid-in capital of $14.8 million within stockholders’ equity.
As of September 30, 2026 and December 31, 2025, we had $362.8 million aggregate principal amount of the 2027 Notes outstanding. As of September 30, 2026 and December 31, 2025, the 2027 Notes had a carrying value of $361.5 million and $360.5 million, respectively, representing outstanding principal amount net of unamortized issuance costs of $1.3 million and $2.3 million, respectively. The issuance costs are amortized to interest expense over the contractual term of the 2027 Notes. The 2027 Notes were classified as a current liability on the condensed consolidated balance sheet as of September 30, 2026 as the maturity date is within 12 months from the balance sheet date. The 2027 Notes were classified as a long-term liability on the condensed consolidated balance sheet as of December 31, 2025. As of September 30, 2026 and December 31, 2025, the estimated fair value of the 2027 Notes was approximately $391.8 million and $534.1 million, respectively, which was determined based on the last actively traded price per $100 of the 2027 Notes (Level 2) on the respective dates. As of September 30, 2026 and December 31, 2025, the effective interest rate of the 2027 Notes was 1%.
2022 Capped Call Transactions
In 2022, in connection with the pricing of the 2027 Notes, we entered into privately negotiated capped call transactions, or 2022 Capped Call Transactions. The 2022 Capped Call Transactions initially cover, subject to customary anti-dilution adjustments, the number of shares of common stock that underlie the 2027 Notes. The cap price of the 2022 Capped Call Transactions is initially $424.00 per share, which represents a premium of 100% over the last reported sale price of common stock of $212.00 per share on September 12, 2022, and is subject to certain adjustments under the terms of the 2022 Capped Call Transactions. As of September 30, 2026, the 2022 Capped Call Transactions remained outstanding. Because these transactions are indexed to our own stock and are considered equity classified, they were recorded in stockholders’ equity and are not accounted for as derivatives. The cost incurred to purchase the 2022 Capped Calls was recorded as a reduction to additional paid-in capital on our condensed consolidated balance sheets and the fair value of the capped call instrument is not remeasured each reporting period.
Revolving Credit Agreement
On September 30, 2025, we entered into the Revolving Credit Agreement, which provides for a $500.0 million revolving line of credit, including a $150.0 million sublimit for issuance of letters of credit. The Revolving Credit Agreement matures in September 2030, subject to earlier springing maturity under certain circumstances.
Borrowings, if any, will bear interest, at our option, at a base rate plus an applicable margin ranging from 0.50% to 1.50% based upon the total leverage ratio or a term Secured Overnight Financing Rate (or an alternative currency term rate) plus an applicable margin ranging from 1.50% to 2.50% based upon the total leverage ratio. We are required to pay, on a quarterly basis, a commitment fee ranging from 0.20% to 0.35% (depending on our total leverage ratio) of unused available commitments under the Revolving Credit Agreement. We are also obligated to pay the administrative agent fees customary for revolving credit facilities of this size and type.
The Revolving Credit Agreement contains customary affirmative and negative covenants and conditions to borrowing, as well as customary events of default. In addition, the Revolving Credit Agreement contains financial covenants that require us to maintain a total leverage ratio less than or equal to 3.75:1.00 and an interest coverage ratio greater than or equal to 3.00:1.00, each tested at the end of each fiscal quarter. As of September 30, 2026, we were in compliance with the financial covenants.
As of September 30, 2026 and December 31, 2025, we had no borrowings and $17.5 million of letters of credit outstanding under the Revolving Credit Agreement.
v3.26.3
LIABILITIES RELATED TO THE SALE OF FUTURE ROYALTIES AND DEVELOPMENT FUNDING
 9 Months Ended
Sep. 30, 2026
Related Party Transactions [Abstract]  
LIABILITIES RELATED TO THE SALE OF FUTURE ROYALTIES AND DEVELOPMENT FUNDING
9. LIABILITIES RELATED TO THE SALE OF FUTURE ROYALTIES AND DEVELOPMENT FUNDING
Development Funding Liabilities
In August 2020, we entered into a co-development agreement, referred to as the Development Funding Agreement, with BXLS V Bodyguard – PCP L.P. and BXLS Family Investment Partnership V – ESC L.P., collectively referred to as Blackstone Life Sciences, pursuant to which Blackstone Life Sciences will provide up to $150.0 million in funding for the clinical development of vutrisiran and zilebesiran, two of our cardiometabolic programs. As of September 30, 2026, Blackstone Life Sciences has provided $70.0 million to fund vutrisiran development costs related to the HELIOS-B Phase 3 clinical trial and $26.0 million to fund Phase 2 clinical trials of zilebesiran. Additionally, Blackstone Life Sciences is obligated to fund $36.0 million for the Phase 3 clinical trial of zilebesiran following development milestones triggered in September 2025 and June 2026, of which $24.0 million has been provided as of September 30, 2026. The amount of funding ultimately provided by Blackstone Life Sciences for the Phase 3 clinical trial of zilebesiran is dependent on us achieving the remaining specified development milestones. As agreed between Blackstone Life Sciences and the Company, we retain sole responsibility for the development and commercialization of both vutrisiran and zilebesiran.
As consideration for Blackstone Life Sciences’ funding for vutrisiran clinical development costs, we agreed to pay Blackstone Life Sciences $175.0 million triggered upon obtaining regulatory approval of vutrisiran for ATTR amyloidosis with cardiomyopathy, or ATTR-CM, and a 1.0% royalty on net sales of vutrisiran for a 10-year term beginning upon the first commercial sale following regulatory approval of vutrisiran for ATTR-CM. In March 2025, we obtained a regulatory approval from the U.S. Food and Drug Administration, or FDA, for vutrisiran for ATTR-CM, triggering the $175.0 million payable to Blackstone Life Sciences in eight equal quarterly payments over two years.
In September 2023, we announced positive topline results from the KARDIA-1 Phase 2 clinical trial of zilebesiran, triggering the achievement of the development milestone of $84.5 million payable to Blackstone Life Sciences in 16 equal quarterly payments over four years, as consideration for Blackstone Life Sciences’ funding for Phase 2 clinical development costs of zilebesiran. As consideration for funding for Phase 3 clinical development costs of zilebesiran, we agreed to pay Blackstone Life Sciences $243.0 million in 16 equal quarterly payments over four years triggered upon regulatory approval of zilebesiran in specified countries, unless it is later withdrawn from the market following a mandatory recall.
Our payment obligations under the Development Funding Agreement are secured, subject to certain exceptions, by security interests in intellectual property owned by us relating to vutrisiran and zilebesiran, as well as in our bank account in which the funding deposits will be made.
We and Blackstone Life Sciences each have the right to terminate the Development Funding Agreement in its entirety in the event of the other party’s bankruptcy or similar proceedings. We and Blackstone Life Sciences may each terminate the Development Funding Agreement in its entirety or with respect to either product in the event of an uncured material breach by the other party, or with respect to a product for certain patient health and safety reasons, or if regulatory approval in specified major market countries is not obtained for the product following the completion of clinical trials for the product. In addition, Blackstone Life Sciences has the right to terminate the Development Funding Agreement in its entirety upon the occurrence of certain events affecting our ability to make payments under the agreement or to develop or commercialize the products, or upon a change of control of us. Blackstone Life Sciences may also terminate the Development Funding Agreement with respect to a
product if the joint steering committee elects to terminate the development program for that product in its entirety, if certain clinical endpoints are not achieved for that product or, with respect to vutrisiran only, if our right to develop or commercialize vutrisiran is enjoined in a specified major market as a result of an alleged patent infringement. In certain termination circumstances, we will be obligated to pay Blackstone Life Sciences an amount that is equal to, or a multiplier of, the development funding received from Blackstone Life Sciences, and we may remain obligated under certain circumstances to make the payments to Blackstone Life Sciences described above should we obtain regulatory approval for zilebesiran following termination.
The debt obligations to repay Blackstone Life Sciences for the vutrisiran and zilebesiran funding are accreted from the initial carrying amount to the total payment amount using the effective interest rate method over the life of the Development Funding Agreement. The effective interest rate is determined based on the proceeds received and projections of the amounts and timing of the future cash flows. The accretion is recorded as interest expense in the condensed consolidated statements of operations and comprehensive income. We recognize the proceeds received and the principal portion of payments made to Blackstone Life Sciences as financing activities within the condensed consolidated statements of cash flows. As of September 30, 2026 and December 31, 2025, our estimates of total interest expense resulted in an effective annual interest rate of 47% and 46%, respectively, related to vutrisiran and 31% and 32%, respectively, related to zilebesiran.
As payments are made to Blackstone Life Sciences, the balance of the liabilities is effectively repaid over the life of the Development Funding Agreement. The exact timing and amount of repayment is likely to change each reporting period. A significant increase or decrease in vutrisiran global net product revenues will materially impact the liability related to the vutrisiran payments and interest expense recognized. At each balance sheet date, we assess the expected payments to Blackstone Life Sciences and we prospectively adjust the amortization of the liabilities and the related interest expense.
The following table shows the activity with respect to the vutrisiran development funding liability, in thousands:
Carrying value as of December 31, 2025
$194,153 
Interest expense
69,133 
Amount paid
(92,908)
Carrying value as of September 30, 2026
$170,378 
As of September 30, 2026 and December 31, 2025, we had $76.0 million and $94.5 million, respectively, within liabilities related to the sale of future royalties and development funding and $94.4 million and $99.7 million, respectively, within liabilities related to the sale of future royalties and development funding, net of current portion on our condensed consolidated balance sheets related to the vutrisiran development funding liability.
The following table shows the activity with respect to the zilebesiran development funding liability, in thousands:
Carrying value as of December 31, 2025
$17,047 
Interest expense
5,979 
Amount paid
(15,844)
Amount received
18,000 
Carrying value as of September 30, 2026
$25,182 
As of September 30, 2026 and December 31, 2025, we had $6.9 million and $6.8 million, respectively, within liabilities related to the sale of future royalties and development funding and $18.3 million and $10.3 million, respectively, within liabilities related to the sale of future royalties and development funding, net of current portion on our condensed consolidated balance sheets related to the zilebesiran development funding liability.
The fair values of the vutrisiran and zilebesiran development funding liabilities were $479.3 million and $120.1 million, respectively, as of September 30, 2026, and $541.3 million and $116.2 million, respectively, as of December 31, 2025, based on our current estimates of future payments over the life of the arrangements and an estimated market participant weighted average cost of capital, which are considered Level 3 inputs.
Liability Related to the Sale of Future Royalties
In April 2020, we entered into a purchase and sale agreement, or Purchase Agreement, with BX Bodyguard Royalties L.P. (an affiliate of The Blackstone Group Inc.), or Blackstone Royalties, pursuant to which Blackstone Royalties acquired a percentage of royalties payable, or the Royalty Interest, initially set at 50% with respect to net sales by MDCO, its affiliates or
sublicensees of inclisiran (or the branded drug product, Leqvio) and any other licensed products under the MDCO License Agreement, and 75% of the commercial milestone payments payable under the MDCO License Agreement, together with the Royalty Interest, the Purchased Interest. If Blackstone Royalties does not receive payments in respect to the Royalty Interest by December 31, 2029, equaling at least $1.00 billion, Blackstone Royalties will receive the Royalty Interest at 55% beginning on January 1, 2030. In consideration for the sale of the Purchased Interest, Blackstone Royalties paid us $1.00 billion.
Due to our continuing involvement and an obligation to repay Blackstone Royalties, we recorded the proceeds from this transaction as a debt, net of closing costs, on our condensed consolidated balance sheets. The debt obligations to repay the Purchased Interest are accreted from the initial carrying amount to the total payment amount using the effective interest rate method over the life of the Purchase Agreement. The effective interest rate is determined based on the proceeds received and projections of the amounts and timing of the future cash flows. The accretion is recorded as interest expense in the condensed consolidated statements of operations and comprehensive income. As of September 30, 2026 and December 31, 2025, our estimate of this total interest expense resulted in an effective annual interest rate of 15% and 10%, respectively. These estimates contain assumptions that impact both the amount recorded at execution and the interest expense that will be recognized in future periods. We account for any royalties and commercial milestones due to us under the MDCO License Agreement as revenue on our condensed consolidated statements of operations and comprehensive income.
As payments are made to Blackstone Royalties, the balance of the liability is effectively repaid over the life of the Purchase Agreement. The exact timing and amount of repayment is likely to change each reporting period. A significant increase or decrease in Leqvio global net revenue will materially impact the liability, interest expense and the time period for repayment. At each balance sheet date, we assess the expected payments to Blackstone Royalties and we prospectively adjust the amortization of the liability and the related interest expense.
As of September 30, 2026 and December 31, 2025, the carrying value of the liability was $1.54 billion and $1.48 billion, net of closing costs of $7.7 million and $8.3 million, respectively. As of September 30, 2026 and December 31, 2025, the fair value of the liability was $2.03 billion and $1.61 billion, respectively, based on our current estimates of future payments over the life of the arrangements and an estimated market participant weighted average cost of capital, which are considered Level 3 inputs.
The following table shows the activity with respect to the liability, in thousands:
Carrying value as of December 31, 2025
$1,479,209 
Interest expense
151,534 
Payments(91,438)
Carrying value as of September 30, 2026
$1,539,305 
As of September 30, 2026 and December 31, 2025, we had $189.2 million and $118.8 million, respectively, within liabilities related to the sale of future royalties and development funding and $1.35 billion and $1.36 billion, respectively, within liabilities related to the sale of future royalties and development funding, net of current portion related to the Purchased Interest.
v3.26.3
STOCK-BASED COMPENSATION
 9 Months Ended
Sep. 30, 2026
Share-Based Payment Arrangement [Abstract]  
STOCK-BASED COMPENSATION
10. STOCK-BASED COMPENSATION
The following table summarizes stock-based compensation expense included in operating costs and expenses on our condensed consolidated statements of operations and comprehensive income, and stock-based compensation charges included in additional paid-in capital on our condensed consolidated statements of stockholders' equity:
Three Months Ended September 30,Nine Months Ended September 30,
(In thousands)2026202520262025
Research and development$32,861 $48,725 $98,867 $122,075 
Selling, general and administrative46,257 59,486 137,030 154,528 
Total stock-based compensation expense
79,118 108,211 235,897 276,603 
Capitalized stock-based compensation costs
1,104 1,128 3,314 3,383 
Total stock-based compensation charges
$80,222 $109,339 $239,211 $279,986 
v3.26.3
NET INCOME (LOSS) PER COMMON SHARE
 9 Months Ended
Sep. 30, 2026
Earnings Per Share [Abstract]  
NET INCOME (LOSS) PER COMMON SHARE
11. NET INCOME (LOSS) PER COMMON SHARE
We compute basic net income (loss) per common share by dividing net income (loss) by the weighted-average number of common shares outstanding. Diluted net income per common share utilizing the treasury stock and if-converted methods is based upon the weighted-average number of common shares and dilutive potential common share equivalents outstanding during the period. For periods in which we have generated a net loss, diluted net loss per common share is the same as basic net loss per common share, as the inclusion of potentially dilutive common shares would be anti-dilutive.
The following table sets forth the computation of basic and diluted net income (loss) per share:
Three Months Ended September 30,Nine Months Ended September 30,
(In thousands, except per share amounts)
2026202520262025
Net income, as reported$2,167,335 $292,683 $2,537,820 $202,204 
Adjustment for the elimination of interest expense on the convertible debt
2,067 1,608 7,091 — 
Net income, for use in diluted income per share$2,169,402 $294,291 $2,544,911 $202,204 
Weighted-average common shares — basic
133,828 131,447 133,444 130,590 
Effect of dilutive securities:
Convertible debt2,255 1,583 2,255 — 
Options to purchase common stock, inclusive of performance-based stock options1,305 2,454 1,605 2,245 
Restricted stock units, inclusive of performance-based restricted stock units
650 1,847 877 1,304 
Employee stock purchase program
2 17 3 7 
Weighted-average common shares — diluted
138,040 137,348 138,184 134,146 
Net income per common share — basic$16.19 $2.23 $19.02 $1.55 
Net income per common share — diluted$15.72 $2.14 $18.42 $1.51 
The following table sets forth the potential weighted-average common shares excluded from the calculation of diluted net income (loss) per common share because their inclusion would be anti-dilutive:
Three Months Ended
September 30,		Nine Months Ended
September 30,
(In thousands)2026202520262025
Options to purchase common stock, inclusive of performance-based stock options424 — 298 157 
Unvested restricted stock units, inclusive of performance-based restricted stock units933 3 581 7 
Convertible debt— 1,788 — 3,491 
Total1,357 1,791 879 3,655 
The effect of the 2022 Capped Call Transactions and 2025 Capped Call Transactions was also excluded from the calculation of diluted net income (loss) per share because exercise of these transactions would potentially reduce the number of shares of the Company’s common stock outstanding and, therefore, would be anti-dilutive. In each of the three and nine months ended September 30, 2026, we excluded 8.5 million shares and in the three and nine months ended September 30, 2025, we excluded 5.8 million shares and 5.4 million shares, respectively, related to these transactions.
v3.26.3
COMMITMENTS AND CONTINGENCIES
 9 Months Ended
Sep. 30, 2026
Commitments and Contingencies Disclosure [Abstract]  
COMMITMENTS AND CONTINGENCIES
12. COMMITMENTS AND CONTINGENCIES
Technology License and Other Commitments
We have licensed from third parties the rights to use certain technologies and information in our research processes as well as in any other products we may develop. In accordance with the related license or technology agreements, we are required to make certain fixed payments to the licensor or a designee of the licensor over various agreement terms. Many of these agreement terms are consistent with the remaining lives of the underlying intellectual property that we have licensed. As of
September 30, 2026, our commitments over the next five years to make fixed and noncancellable payments under existing license agreements were not material.
Legal Matters
From time to time, we may be a party to litigation, arbitration or other legal proceedings in the ordinary course of our business activities, including the following types of matters which are common to companies in our industry:
•Patent litigation, which typically involves challenges to the coverage and/or validity of patents on various products or product candidates, processes or dosage forms. An adverse outcome could result in loss of patent protection for a product or product candidates, a significant loss of revenues from a product or impairment of the value of associated assets.
•Product liability and other product-related litigation related to our products, which could include personal injury, consumer fraud, off-label promotion, securities, antitrust and breach of contract claims, among others, and often involves highly complex issues relating to medical causation, label warnings and reliance on those warnings, scientific evidence and findings, actual, provable injury and other matters.
•Commercial and other asserted or unasserted matters, which can include acquisition-, licensing-, intellectual property-, collaboration- or co-promotion-related and product-pricing claims and environmental claims and proceedings, which can involve complexities that will vary from matter to matter.
•Government investigations, which often are related to the extensive regulation of pharmaceutical companies by national, state and local government agencies in the U.S. and in other jurisdictions.
The outcome of any such legal proceedings, regardless of the merits, is inherently uncertain. In addition, litigation and related matters are costly and may divert the attention of our management and other resources that would otherwise be engaged in other activities. If we were unable to prevail in any such legal proceedings, it could have a materially adverse effect on our business, results of operations, liquidity and financial condition.
If we determine that it is probable that future expenditures will be made for a particular matter and such expenditures can be reasonably estimated, we accrue a loss contingency based on our best estimate of the probable range of loss. We accrue the minimum amount within the probable range of loss if no amount within the range is more likely than another. If we determine that future expenditures are not probable, or probable but not reasonably estimated, we do not accrue a loss contingency. If we determine that a material loss is reasonably possible and the range of loss can be estimated, we disclose the possible range of loss. On a quarterly basis, we evaluate developments with these claims and legal proceedings that could result in a loss contingency accrual, or an increase or decrease to a previously accrued loss contingency. There were no material loss contingencies accrued as of September 30, 2026 or December 31, 2025.
Patent Litigation
On December 12, 2024, The Board of Regents of the University of Texas System filed a lawsuit in the U.S. District Court for the Western District of Texas, or the Texas District Court, alleging that we infringe U.S. Patent No. 8,895,717 by making, using and commercializing ONPATTRO in the U.S. On December 15, 2025, the Texas District Court denied our motion to dismiss and granted our motion to transfer and ordered the case transferred to the U.S. District Court for the District of Massachusetts. The case is now proceeding in the District of Massachusetts. Trial is scheduled for August 2027.
On March 13, 2026, we and our collaborators, Novartis Pharmaceuticals Corp., Novartis Technology LLC, and The Medicines Company, filed a patent infringement lawsuit against Cipla USA Inc. and Cipla Ltd, or collectively Cipla, in the U.S. District Court for the District of Delaware based on Cipla’s abbreviated new drug application seeking approval from the FDA to market a generic version of Leqvio (inclisiran).
On September 16, 2026, we filed a patent infringement lawsuit against Cipla in the U.S. District Court for the District of Delaware based on Cipla’s abbreviated new drug application seeking approval from the FDA to market a generic version of AMVUTTRA (vutrisiran).
Government Investigation
In October 2025, we received a subpoena from the U.S. Attorney’s Office for the District of Massachusetts seeking documents pertaining to our government price reporting for AMVUTTRA, ONPATTRO, OXLUMO and GIVLAARI, including certain fee and discount arrangements with distributors, and certain other related documents and communications. We have produced records responsive to the subpoena and are continuing to engage with the U.S. Attorney’s Office.
Indemnification Obligations
In connection with license agreements we may enter with companies to obtain rights to intellectual property, we may be required to indemnify such companies for certain damages arising in connection with the intellectual property rights licensed under the agreements. Under such agreements, we may be responsible for paying the costs of any litigation relating to the license agreements or the underlying intellectual property rights, including the costs associated with certain litigation regarding the licensed intellectual property. We are also a party to a number of agreements entered into in the ordinary course of business, which contain typical provisions that obligate us to indemnify the other parties to such agreements upon the occurrence of certain events, including litigation or other legal proceedings. In addition, we have agreed to indemnify our officers and directors for expenses, judgments, fines, penalties, excise taxes, and settlement amounts paid in connection with any threatened, pending or completed litigation proceedings, in which an officer or director was, is or will be involved as a party, on account of such person’s status as an officer or director, or by reason of any action taken by the officer or director while acting in such capacity, subject to certain limitations. These indemnification costs are charged to selling, general and administrative expense.
Our maximum potential future liability under any such indemnification provisions is uncertain. We have reviewed the estimated aggregate fair value of our potential liabilities under all such indemnification provisions and have not recorded any related liability as of September 30, 2026 or December 31, 2025.
v3.26.3
SEGMENT INFORMATION
 9 Months Ended
Sep. 30, 2026
Segment Reporting [Abstract]  
SEGMENT INFORMATION
13. SEGMENT INFORMATION
We operate in a single segment dedicated to the discovery, development, manufacturing and commercialization of RNAi therapeutics. Consistent with our management reporting, results of our operations are reported on a consolidated basis for purposes of segment reporting. Our Chief Executive Officer, or CEO, as the chief operating decision maker evaluates performance and decides how to allocate resources based on consolidated net income (loss) that is reported on the condensed consolidated statements of operations and comprehensive income. The measure of segment assets is reported on the condensed consolidated balance sheets as total assets. Please refer to the condensed consolidated financial statements for further information related to these measures of segment performance. In addition, research and development and selling, general and administrative expenses are significant segment expenses regularly provided to the CEO with the following categories:
Research and Development
Three Months Ended
September 30,		Nine Months Ended
September 30,
(In thousands)
2026202520262025
Clinical research and outside services$239,525 $170,756 $683,008 $438,791 
Compensation and related121,722 146,089 371,410 388,726 
Occupancy and all other costs(1)
47,291 41,969 132,120 120,040 
Total research and development expense
$408,538 $358,814 $1,186,538 $947,557 
Selling, General and Administrative
Three Months Ended
September 30,		Nine Months Ended
September 30,
(In thousands)
2026202520262025
Compensation and related
$167,544 $188,669 $497,240 $511,339 
Consulting and professional services
118,917 88,738 344,815 236,062 
Occupancy and all other costs(1)
55,539 44,669 170,418 137,938 
Total selling, general and administrative expense
$342,000 $322,076 $1,012,473 $885,339 
(1) Occupancy and all other costs includes facilities, information technology, depreciation and certain departmental expenses.
v3.26.3
INCOME TAXES
 9 Months Ended
Sep. 30, 2026
Income Tax Disclosure [Abstract]  
INCOME TAXES
14. INCOME TAXES

We recorded an income tax benefit of $1.87 billion and $1.84 billion for the three and nine months ended September 30, 2026, respectively, compared with an income tax benefit of $12.1 million for the three months ended September 30, 2025 and income tax expense of $34.7 million for the nine months ended September 30, 2025. The 2026 income tax benefit was primarily attributable to the release of valuation allowances on certain U.S. federal and state deferred tax assets in the three months ended September 30, 2026.

We evaluate the realizability of our deferred tax assets quarterly, considering the relative weight of positive and negative evidence in each relevant tax jurisdiction. During the three months ended September 30, 2026, we concluded, based on sustained profitability and our expectations for future taxable income, that it was more likely than not that certain U.S. federal and state deferred tax assets would be realized. Accordingly, we released $1.95 billion of valuation allowance related to deferred tax assets from prior years and recognized the release as a discrete income tax benefit during the three months ended September 30, 2026. The income tax effects of changes in valuation allowances relating to current-year estimated ordinary income were reflected in the estimated annual effective tax rate, as applicable. We continue to maintain valuation allowances on certain net operating loss carryforwards and tax credit deferred tax assets for which realization is not considered more likely than not, including state research and development tax credits. The valuation allowance on state research and development tax credits reflects our expectation that future credit generation will exceed the amount expected to be utilized under applicable state tax rules. We will continue to reassess the realizability of our deferred tax assets each quarter.
v3.26.3
Insider Trading Arrangements
 3 Months Ended
Sep. 30, 2026
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
Tolga Tanguler [Member]  
Trading Arrangements, by Individual  
Material Terms of Trading Arrangement
Tolga Tanguler, Chief Commercialization Officer

On August 24, 2026, Tolga Tanguler, our Chief Commercialization Officer, entered into a Rule 10b5-1 trading plan that provides that Mr. Tanguler, acting through a broker, may sell up to an aggregate of 22,438 shares of our common stock received upon the settlement of awards granted to Mr. Tanguler as equity incentive compensation, subject to adjustments for stock splits, stock combinations, stock dividends and other similar changes to our common stock. Sales of shares under the plan may only occur from November 23, 2026 to August 6, 2027. The plan is scheduled to terminate on August 6, 2027, subject to earlier termination upon the sale of all shares subject to the plan, upon termination by Mr. Tanguler or the broker, or as otherwise provided in the plan.
Name Tolga Tanguler
Title Chief Commercialization Officer
Rule 10b5-1 Arrangement Adopted true
Adoption Date August 24, 2026
Expiration Date August 6, 2027
Arrangement Duration 256 days
Aggregate Available 22,438
v3.26.3
BASIS OF PRESENTATION AND PRINCIPLES OF CONSOLIDATION (Policies)
 9 Months Ended
Sep. 30, 2026
Accounting Policies [Abstract]  
Basis of Presentation and Principles of Consolidation
The accompanying condensed consolidated financial statements of Alnylam are unaudited and have been prepared in accordance with accounting principles generally accepted in the United States of America, or GAAP, applicable to interim periods and, in the opinion of management, include all normal and recurring adjustments that are necessary to state fairly the results of operations for the reported periods. Our condensed consolidated financial statements have also been prepared on a basis substantially consistent with, and should be read in conjunction with, our audited consolidated financial statements for the year ended December 31, 2025, which were included in our Annual Report on Form 10-K that was filed with the Securities and Exchange Commission on February 12, 2026. The year-end condensed consolidated balance sheet data was derived from our audited financial statements but does not include all disclosures required by GAAP. The results of our operations for any interim period are not necessarily indicative of the results of our operations for any other interim period or for a full fiscal year.
The accompanying condensed consolidated financial statements reflect the operations of Alnylam and our wholly-owned subsidiaries. All intercompany accounts and transactions have been eliminated. We evaluate variable interests in a variable interest entity, or VIE, and consolidate VIEs when we are the primary beneficiary. Determination of whether we are the primary beneficiary of each VIE is based on an assessment of whether we possess both (i) the power to direct the activities that most significantly affect the VIE’s economic performance and (ii) the obligation to absorb losses or the right to receive benefits that could be significant to the VIE. We continuously reevaluate the accounting for our VIEs upon the occurrence of events that could change the primary beneficiary conclusion. The maximum risk of loss related to our VIEs is generally limited to the carrying value of the investment in such entities, but may also include prepaid expenses recognized for advances made to a VIE and future funding commitments, if applicable.
Certain prior period amounts in the condensed consolidated financial statements have been retrospectively adjusted to reflect the guidance of Accounting Standards Update, or ASU, 2025-07, Derivatives Scope Refinements and Scope Clarification for Share-Based Noncash Consideration from a Customer in a Revenue Contract, which we adopted in the fourth quarter of 2025 on a modified retrospective basis as of January 1, 2025. Refer to Note 2 of the Notes to Consolidated Financial Statements included in our Annual Report on Form 10-K for the year ended December 31, 2025.
Our significant accounting policies are described in Note 2 of the Notes to Consolidated Financial Statements included in our Annual Report on Form 10-K for the year ended December 31, 2025. There have been no material changes to our significant accounting policies during the nine months ended September 30, 2026.
Use of Estimates
Use of Estimates
The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities as of the date of the condensed consolidated financial statements and the reported amounts of revenues and expenses during the reporting period. In our condensed consolidated financial statements, we use estimates and assumptions related to our inventory valuation and related reserves, clinical accruals, liabilities related to the sale of future royalties and development funding, income taxes, deferred tax asset valuation allowances, revenue recognition and related allowances and reserves, research and development expenses, and stock-based compensation expense. We base our estimates on historical experience and on various other
assumptions that we believe to be reasonable. Actual results could differ from those estimates. Changes in estimates are reflected in reported results in the period in which they become known.
Liquidity
Liquidity
Based on our current operating plan, we believe that our cash, cash equivalents, marketable securities, as well as the revenue we expect to generate from product sales and under our existing collaborations, including royalties on sales of Leqvio and Qfitlia, and available borrowing capacity under the revolving credit agreement, or the Revolving Credit Agreement, as of September 30, 2026, will be sufficient to satisfy our near-term capital and operating needs for at least the next 12 months from the filing date of this Quarterly Report on Form 10-Q. Please refer to Note 8, Convertible Debt and Other Financing, for further information related to the Revolving Credit Agreement.
Recent Accounting Pronouncements
Recent Accounting Pronouncements
In September 2025, the Financial Accounting Standards Board, or FASB, issued ASU 2025-06, Targeted Improvements to the Accounting for Internal-Use Software, which modernizes the guidance for internal-use software costs by increasing the operability of the recognition guidance considering different methods of software development. The standard will be effective for annual reporting periods beginning after December 15, 2027, as well as interim reporting periods within those annual reporting periods, with early adoption permitted. The standard updates may be applied on a prospective, retrospective, or modified retrospective approach. We are currently evaluating the impact this guidance could have on our condensed consolidated financial statements and related disclosures.
In November 2024, the FASB issued ASU 2024-03, Disaggregation of Income Statement Expenses, or ASU 2024-03, which is intended to improve disclosures by requiring additional information about specific expense categories in the notes to the financial statements on an annual and interim basis. Additionally, in January 2025, the FASB issued ASU 2025-01, clarifying that ASU 2024-03 will be effective for annual reporting periods beginning after December 15, 2026 and interim reporting periods beginning after December 15, 2027, with early adoption permitted. The standard updates may be applied on either a prospective or retrospective basis. We are currently evaluating the disclosure requirements related to ASU 2024-03.
v3.26.3
NET PRODUCT REVENUES (Tables)
 9 Months Ended
Sep. 30, 2026
Revenue from Contract with Customer [Abstract]  
Schedule of Deferred Revenue Activity
Net product revenues, classified based on the geographic region in which the product is sold and by franchise (“TTR,” which includes AMVUTTRA and ONPATTRO, and “Rare,” which includes GIVLAARI and OXLUMO) consisted of the following:
Three Months Ended September 30,Nine Months Ended September 30,
(In thousands)2026202520262025
AMVUTTRA
United States$908,596 $530,347 $2,420,229 $1,089,657 
Europe130,718 111,944 363,041 284,900 
Rest of World91,049 43,012 248,786 112,691 
Total1,130,363 685,303 3,032,056 1,487,248 
ONPATTRO
United States9,705 12,480 29,734 50,105 
Europe4,762 19,678 17,835 67,465 
Rest of World5,129 6,917 10,969 23,532 
Total19,596 39,075 58,538 141,102 
Total TTR
1,149,959 724,378 3,090,594 1,628,350 
GIVLAARI
United States57,459 50,426 164,550 149,371 
Europe20,872 18,706 65,485 58,216 
Rest of World11,156 4,742 23,610 14,104 
Total89,487 73,874 253,645 221,691 
OXLUMO
United States18,429 20,727 53,939 50,855 
Europe23,213 22,346 70,281 65,259 
Rest of World10,858 9,757 31,723 25,677 
Total52,500 52,830 155,943 141,791 
Total Rare
141,987 126,704 409,588 363,482 
Total net product revenues$1,291,946 $851,082 $3,500,182 $1,991,832 
Schedule of Balances and Activity in Each Product Revenue Allowance and Reserve Category
The following table summarizes balances and activity in each product revenue allowance and reserve category:
(In thousands)Chargebacks and Rebates
Other Incentives and Allowances
Total
Beginning balance as of December 31, 2025
$399,853 $25,797 $425,650 
Provision related to current year sales
968,692 95,819 1,064,511 
Provision related to prior years’ sales
(6,045)(992)(7,037)
Credit or payments made during the period for current year sales
(598,591)(71,712)(670,303)
Credit or payments made during the period for prior years’ sales
(239,525)(16,323)(255,848)
Total as of September 30, 2026
$524,384 $32,589 $556,973 
v3.26.3
COLLABORATIONS (Tables)
 9 Months Ended
Sep. 30, 2026
Organization, Consolidation and Presentation of Financial Statements [Abstract]  
Schedule of Revenue from Collaborators
Net revenues from collaborations consisted of the following:
Three Months Ended September 30,Nine Months Ended September 30,
(In thousands)2026202520262025
Roche
$39,107 $326,604 $116,636 $361,927 
Regeneron Pharmaceuticals32,334 22,542 83,690 106,123 
Other35 2,596 390 44,373 
Total net revenues from collaborations
$71,476 $351,742 $200,716 $512,423 
Net revenues from collaborations recognized under the Roche Agreement consisted of the following:
Three Months Ended September 30,Nine Months Ended September 30,
(In thousands)2026202520262025
Roche License Obligation
$— $300,000 $— $300,000 
Roche Development Services Obligation
$37,557 $25,166 112,196 57,696 
Other
1,550 1,438 4,440 4,231 
Total
$39,107 $326,604 $116,636 $361,927 
Net revenues from collaborations recognized under the Regeneron Collaboration consisted of the following:
Three Months Ended September 30,Nine Months Ended September 30,
(In thousands)2026202520262025
Research Services Obligation
$7,345 $12,540 $13,176 $39,306 
C5 License Obligation
— — — 21,370 
Regeneron Technology Transfer Obligation
— — — 2,431 
Other license programs
24,989 10,002 70,514 43,016 
Total
$32,334 $22,542 $83,690 $106,123 
Schedule of Deferred Revenue
The following table presents the balance of our receivables and contract liabilities related to our collaboration agreements:
(In thousands)As of September 30, 2026As of December 31, 2025
Receivables included in accounts receivable, net
$89,603 $48,823 
Contract liabilities included in deferred revenue$11,669 $4,845 
Schedule of Allocated Transaction Price Based on Accounting Guidance
The following table provides a summary of the transaction price allocated to each performance obligation:
(In thousands)
As of September 30, 2026
Roche License Obligation
$675,000 
Roche Development Services Obligation
1,061,167 
Roche Technology Transfer Obligation
2,000 
$1,738,167 
v3.26.3
FAIR VALUE MEASUREMENTS (Tables)
 9 Months Ended
Sep. 30, 2026
Fair Value Disclosures [Abstract]  
Schedule of Fair Value of Assets Measured on a Recurring Basis
The following tables present information about our financial assets that are measured at fair value on a recurring basis and indicate the fair value hierarchy of the valuation techniques we utilized to determine such fair value:
(In thousands)As of September 30, 2026Quoted Prices in Active Markets
(Level 1)		Significant Observable Inputs
(Level 2)		Significant Unobservable Inputs
(Level 3)
Financial assets
Cash equivalents:
Money market funds$173,768 $173,768 $— $— 
U.S. treasury securities34,948 — 34,948 — 
Commercial paper9,265 — 9,265 — 
Marketable debt securities:
U.S. treasury securities847,996 — 847,996 — 
Corporate notes514,295 — 514,295 — 
U.S. government-sponsored enterprise securities451,805 — 451,805 — 
Commercial paper18,819 — 18,819 — 
Restricted cash (money market funds)570 570 — — 
Total financial assets$2,051,466 $174,338 $1,877,128 $— 
(In thousands)As of December 31, 2025Quoted Prices in Active Markets
(Level 1)		Significant Observable Inputs
(Level 2)		Significant Unobservable Inputs
(Level 3)
Financial assets
Cash equivalents:
Money market funds$140,445 $140,445 $— $— 
U.S. treasury securities18,952 — 18,952 — 
U.S. government-sponsored enterprise securities2,690 — 2,690 — 
Commercial paper1,995 — 1,995 — 
Marketable debt securities:
U.S. treasury securities653,341 — 653,341 — 
Corporate notes333,241 — 333,241 — 
U.S. government-sponsored enterprise securities252,634 — 252,634 — 
Commercial paper7,017 — 7,017 — 
Municipal securities5,001 — 5,001 — 
Restricted cash (money market funds)917 917 — — 
Total financial assets$1,416,233 $141,362 $1,274,871 $— 
v3.26.3
MARKETABLE DEBT SECURITIES (Tables)
 9 Months Ended
Sep. 30, 2026
Investments, Debt and Equity Securities [Abstract]  
Schedule of Marketable Debt Securities
The following tables summarize our marketable debt securities:
As of September 30, 2026
(In thousands)Amortized
Cost
Gross Unrealized Gains
Gross Unrealized Losses
Fair Value
U.S. treasury securities$890,175 $17 $(7,248)$882,944 
Corporate notes518,707 11 (4,423)514,295 
U.S. government-sponsored enterprise securities455,852 4 (4,051)451,805 
Commercial paper28,132 — (48)28,084 
Total$1,892,866 $32 $(15,770)$1,877,128 
As of December 31, 2025
(In thousands)Amortized
Cost
Gross Unrealized Gains
Gross Unrealized Losses
Fair Value
U.S. treasury securities$670,566 $1,736 $(9)$672,293 
Corporate notes332,104 1,152 (15)333,241 
U.S. government-sponsored enterprise securities254,829 559 (64)255,324 
Commercial paper9,012 — — 9,012 
Municipal securities5,000 1 — 5,001 
Total$1,271,511 $3,448 $(88)$1,274,871 
Schedule of Fair Value of Marketable Debt Securities
The fair values of our marketable debt securities by classification in the condensed consolidated balance sheets were as follows:
(In thousands)As of September 30, 2026As of December 31, 2025
Marketable debt securities$1,832,915 $1,251,234 
Cash and cash equivalents44,213 23,637 
Total$1,877,128 $1,274,871 
v3.26.3
OTHER BALANCE SHEET DETAILS (Tables)
 9 Months Ended
Sep. 30, 2026
Organization, Consolidation and Presentation of Financial Statements [Abstract]  
Schedule of Inventory
The components of inventory are summarized as follows:
(In thousands)As of September 30, 2026As of December 31, 2025
Raw materials$18,016 $14,184 
Work in process
58,798 65,122 
Finished goods40,421 32,338 
Total inventory
$117,235 $111,644 
Schedule of Reconciliation of Cash, Cash Equivalents And Restricted Cash
The following table provides a reconciliation of cash, cash equivalents and restricted cash reported within our condensed consolidated balance sheets to the totals of these amounts shown in the condensed consolidated statements of cash flows:
As of September 30,
(In thousands)20262025
Cash and cash equivalents$1,754,340 $1,490,249 
Total restricted cash included in other assets1,477 2,553 
Total cash, cash equivalents, and restricted cash shown in the condensed consolidated statements of cash flows
$1,755,817 $1,492,802 
Schedule of Changes in Accumulated Other Comprehensive Loss
The following tables summarize the changes in accumulated other comprehensive loss, by component:
(In thousands)Loss on Investment in Joint Venture
Defined Benefit Pension
Plans, Net of Tax
Unrealized Gains (Losses) from Debt
Securities
Foreign Currency Translation
Adjustment
Total Accumulated Other
Comprehensive Loss
Balance as of December 31, 2025$(32,792)$(3,268)$3,360 $12,603 $(20,097)
Other comprehensive loss before reclassifications
— — (14,214)(5,733)(19,947)
Amounts reclassified from accumulated other comprehensive loss
— 267 (4,884)— (4,617)
Net other comprehensive income (loss)
— 267 (19,098)(5,733)(24,564)
Balance as of September 30, 2026$(32,792)$(3,001)$(15,738)$6,870 $(44,661)
(In thousands)Loss on Investment in Joint Venture
Defined Benefit Pension
Plans, Net of Tax
Unrealized Gains (Losses) from Debt
Securities
Foreign Currency Translation
Adjustment
Total Accumulated Other Comprehensive Loss
Balance as of December 31, 2024$(32,792)$(4,249)$1,544 $979 $(34,518)
Other comprehensive income before reclassifications— — 3,001 10,764 13,765 
Amounts reclassified from accumulated other comprehensive loss
— 161 (1,183)— (1,022)
Net other comprehensive income— 161 1,818 10,764 12,743 
Balance as of September 30, 2025$(32,792)$(4,088)$3,362 $11,743 $(21,775)
v3.26.3
LIABILITIES RELATED TO THE SALE OF FUTURE ROYALTIES AND DEVELOPMENT FUNDING (Tables)
 9 Months Ended
Sep. 30, 2026
Related Party Transactions [Abstract]  
Schedule of Fair Value, Liabilities
The following table shows the activity with respect to the vutrisiran development funding liability, in thousands:
Carrying value as of December 31, 2025
$194,153 
Interest expense
69,133 
Amount paid
(92,908)
Carrying value as of September 30, 2026
$170,378 
The following table shows the activity with respect to the zilebesiran development funding liability, in thousands:
Carrying value as of December 31, 2025
$17,047 
Interest expense
5,979 
Amount paid
(15,844)
Amount received
18,000 
Carrying value as of September 30, 2026
$25,182 
Schedule of Royalty Liability
The following table shows the activity with respect to the liability, in thousands:
Carrying value as of December 31, 2025
$1,479,209 
Interest expense
151,534 
Payments(91,438)
Carrying value as of September 30, 2026
$1,539,305 
v3.26.3
STOCK-BASED COMPENSATION (Tables)
 9 Months Ended
Sep. 30, 2026
Share-Based Payment Arrangement [Abstract]  
Schedule of Stock Based Compensation
The following table summarizes stock-based compensation expense included in operating costs and expenses on our condensed consolidated statements of operations and comprehensive income, and stock-based compensation charges included in additional paid-in capital on our condensed consolidated statements of stockholders' equity:
Three Months Ended September 30,Nine Months Ended September 30,
(In thousands)2026202520262025
Research and development$32,861 $48,725 $98,867 $122,075 
Selling, general and administrative46,257 59,486 137,030 154,528 
Total stock-based compensation expense
79,118 108,211 235,897 276,603 
Capitalized stock-based compensation costs
1,104 1,128 3,314 3,383 
Total stock-based compensation charges
$80,222 $109,339 $239,211 $279,986 
v3.26.3
NET INCOME (LOSS) PER COMMON SHARE (Tables)
 9 Months Ended
Sep. 30, 2026
Earnings Per Share [Abstract]  
Schedule of Basic and Diluted Net Income (Loss) Per Share
The following table sets forth the computation of basic and diluted net income (loss) per share:
Three Months Ended September 30,Nine Months Ended September 30,
(In thousands, except per share amounts)
2026202520262025
Net income, as reported$2,167,335 $292,683 $2,537,820 $202,204 
Adjustment for the elimination of interest expense on the convertible debt
2,067 1,608 7,091 — 
Net income, for use in diluted income per share$2,169,402 $294,291 $2,544,911 $202,204 
Weighted-average common shares — basic
133,828 131,447 133,444 130,590 
Effect of dilutive securities:
Convertible debt2,255 1,583 2,255 — 
Options to purchase common stock, inclusive of performance-based stock options1,305 2,454 1,605 2,245 
Restricted stock units, inclusive of performance-based restricted stock units
650 1,847 877 1,304 
Employee stock purchase program
2 17 3 7 
Weighted-average common shares — diluted
138,040 137,348 138,184 134,146 
Net income per common share — basic$16.19 $2.23 $19.02 $1.55 
Net income per common share — diluted$15.72 $2.14 $18.42 $1.51 
Schedule of Common Share Equivalents Excluded from the Calculation of Net Loss Per Common Share
The following table sets forth the potential weighted-average common shares excluded from the calculation of diluted net income (loss) per common share because their inclusion would be anti-dilutive:
Three Months Ended
September 30,		Nine Months Ended
September 30,
(In thousands)2026202520262025
Options to purchase common stock, inclusive of performance-based stock options424 — 298 157 
Unvested restricted stock units, inclusive of performance-based restricted stock units933 3 581 7 
Convertible debt— 1,788 — 3,491 
Total1,357 1,791 879 3,655 
v3.26.3
SEGMENT INFORMATION (Tables)
 9 Months Ended
Sep. 30, 2026
Segment Reporting [Abstract]  
Schedule of Expenses by Segment In addition, research and development and selling, general and administrative expenses are significant segment expenses regularly provided to the CEO with the following categories:
Research and Development
Three Months Ended
September 30,		Nine Months Ended
September 30,
(In thousands)
2026202520262025
Clinical research and outside services$239,525 $170,756 $683,008 $438,791 
Compensation and related121,722 146,089 371,410 388,726 
Occupancy and all other costs(1)
47,291 41,969 132,120 120,040 
Total research and development expense
$408,538 $358,814 $1,186,538 $947,557 
Selling, General and Administrative
Three Months Ended
September 30,		Nine Months Ended
September 30,
(In thousands)
2026202520262025
Compensation and related
$167,544 $188,669 $497,240 $511,339 
Consulting and professional services
118,917 88,738 344,815 236,062 
Occupancy and all other costs(1)
55,539 44,669 170,418 137,938 
Total selling, general and administrative expense
$342,000 $322,076 $1,012,473 $885,339 
(1) Occupancy and all other costs includes facilities, information technology, depreciation and certain departmental expenses
v3.26.3
NATURE OF BUSINESS (Details)
Sep. 30, 2026
product
Organization, Consolidation and Presentation of Financial Statements [Abstract]  
Number of marketed products 6
Number of partnered products 2
Number of commercialized products 4
v3.26.3
NET PRODUCT REVENUES - Schedule of Net Product Revenues (Detail) - USD ($)
$ in Thousands
 3 Months Ended 9 Months Ended
Sep. 30, 2026
Sep. 30, 2025
Sep. 30, 2026
Sep. 30, 2025
Disaggregation of Revenue [Line Items]        
Total revenues $ 1,458,086 $ 1,249,026 $ 3,916,209 $ 2,616,904
Net product revenues        
Disaggregation of Revenue [Line Items]        
Total revenues 1,291,946 851,082 3,500,182 1,991,832
Total TTR        
Disaggregation of Revenue [Line Items]        
Total revenues 1,149,959 724,378 3,090,594 1,628,350
AMVUTTRA        
Disaggregation of Revenue [Line Items]        
Total revenues 1,130,363 685,303 3,032,056 1,487,248
ONPATTRO        
Disaggregation of Revenue [Line Items]        
Total revenues 19,596 39,075 58,538 141,102
Total Rare        
Disaggregation of Revenue [Line Items]        
Total revenues 141,987 126,704 409,588 363,482
GIVLAARI        
Disaggregation of Revenue [Line Items]        
Total revenues 89,487 73,874 253,645 221,691
OXLUMO        
Disaggregation of Revenue [Line Items]        
Total revenues 52,500 52,830 155,943 141,791
United States | AMVUTTRA        
Disaggregation of Revenue [Line Items]        
Total revenues 908,596 530,347 2,420,229 1,089,657
United States | ONPATTRO        
Disaggregation of Revenue [Line Items]        
Total revenues 9,705 12,480 29,734 50,105
United States | GIVLAARI        
Disaggregation of Revenue [Line Items]        
Total revenues 57,459 50,426 164,550 149,371
United States | OXLUMO        
Disaggregation of Revenue [Line Items]        
Total revenues 18,429 20,727 53,939 50,855
Europe | AMVUTTRA        
Disaggregation of Revenue [Line Items]        
Total revenues 130,718 111,944 363,041 284,900
Europe | ONPATTRO        
Disaggregation of Revenue [Line Items]        
Total revenues 4,762 19,678 17,835 67,465
Europe | GIVLAARI        
Disaggregation of Revenue [Line Items]        
Total revenues 20,872 18,706 65,485 58,216
Europe | OXLUMO        
Disaggregation of Revenue [Line Items]        
Total revenues 23,213 22,346 70,281 65,259
Rest of World | AMVUTTRA        
Disaggregation of Revenue [Line Items]        
Total revenues 91,049 43,012 248,786 112,691
Rest of World | ONPATTRO        
Disaggregation of Revenue [Line Items]        
Total revenues 5,129 6,917 10,969 23,532
Rest of World | GIVLAARI        
Disaggregation of Revenue [Line Items]        
Total revenues 11,156 4,742 23,610 14,104
Rest of World | OXLUMO        
Disaggregation of Revenue [Line Items]        
Total revenues $ 10,858 $ 9,757 $ 31,723 $ 25,677
v3.26.3
NET PRODUCT REVENUES - Additional Information (Detail) - USD ($)
$ in Thousands
Sep. 30, 2026
Dec. 31, 2025
Disaggregation of Revenue [Line Items]    
Net product revenue-related receivables $ 1,084,905 $ 777,567
Net product revenues    
Disaggregation of Revenue [Line Items]    
Net product revenue-related receivables $ 906,200 $ 669,500
v3.26.3
NET PRODUCT REVENUES - Schedule of Balances and Activity in Each Product Revenue Allowance and Reserve Category (Detail)
$ in Thousands
 9 Months Ended
Sep. 30, 2026
USD ($)
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]  
Beginning balance $ 425,650
Provision related to current year sales 1,064,511
Provision related to prior years’ sales (7,037)
Credit or payments made during the period for current year sales (670,303)
Credit or payments made during the period for prior years’ sales (255,848)
Ending balance 556,973
Chargebacks and Rebates  
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]  
Beginning balance 399,853
Provision related to current year sales 968,692
Provision related to prior years’ sales (6,045)
Credit or payments made during the period for current year sales (598,591)
Credit or payments made during the period for prior years’ sales (239,525)
Ending balance 524,384
Other Incentives and Allowances  
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]  
Beginning balance 25,797
Provision related to current year sales 95,819
Provision related to prior years’ sales (992)
Credit or payments made during the period for current year sales (71,712)
Credit or payments made during the period for prior years’ sales (16,323)
Ending balance $ 32,589
v3.26.3
COLLABORATIONS - Schedule of Revenue from Collaborators (Detail) - USD ($)
$ in Thousands
 3 Months Ended 9 Months Ended
Sep. 30, 2026
Sep. 30, 2025
Sep. 30, 2026
Sep. 30, 2025
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]        
Total revenues $ 1,458,086 $ 1,249,026 $ 3,916,209 $ 2,616,904
Regeneron Pharmaceuticals        
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]        
Total revenues 32,334 22,542 83,690 106,123
Net revenues from collaborations        
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]        
Total revenues 71,476 351,742 200,716 512,423
Net revenues from collaborations | Roche        
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]        
Total revenues 39,107 326,604 116,636 361,927
Net revenues from collaborations | Regeneron Pharmaceuticals        
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]        
Total revenues 32,334 22,542 83,690 106,123
Net revenues from collaborations | Other        
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]        
Total revenues $ 35 $ 2,596 $ 390 $ 44,373
v3.26.3
COLLABORATIONS - Schedule of Balance of Receivables and Contract Liabilities Related to Collaboration Agreements (Detail) - USD ($)
$ in Thousands
Sep. 30, 2026
Dec. 31, 2025
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]    
Receivables included in accounts receivable, net $ 1,084,905 $ 777,567
Contract liabilities included in deferred revenue 11,669 4,845
Net revenues from collaborations    
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]    
Receivables included in accounts receivable, net 89,603 48,823
Contract liabilities included in deferred revenue $ 11,669 $ 4,845
v3.26.3
COLLABORATIONS - Additional Information (Detail)
$ in Thousands
 1 Months Ended 3 Months Ended 9 Months Ended 12 Months Ended
Jul. 21, 2023
performance_obligation
Jun. 30, 2026
USD ($)
Mar. 31, 2025
USD ($)
Jun. 30, 2024
USD ($)
performance_obligation
Sep. 30, 2026
USD ($)
Sep. 30, 2025
USD ($)
Mar. 31, 2025
USD ($)
Sep. 30, 2026
USD ($)
program
Sep. 30, 2025
USD ($)
Dec. 31, 2019
USD ($)
Dec. 31, 2025
USD ($)
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]                      
Contract with customer liability revenue recognized         $ 4,000 $ 12,500   $ 4,800 $ 53,600    
Research and development         408,538 358,814   $ 1,186,538 947,557    
Number of separate programs | program               12      
Deferred revenue         11,669     $ 11,669     $ 4,845
Total revenues         1,458,086 1,249,026   3,916,209 2,616,904    
Collaborations                      
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]                      
Total revenues         71,476 351,742   200,716 512,423    
Roche | License                      
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]                      
Transaction price         1,740,000     1,740,000      
Regeneron Pharmaceuticals                      
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]                      
Total revenues         32,334 22,542   83,690 106,123    
Regeneron Pharmaceuticals | Research Services Obligation                      
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]                      
Deferred revenue         11,700     $ 11,700     $ 4,800
Vir Biotechnology, Inc. | Collaborations                      
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]                      
Total revenues     $ 30,000       $ 30,000        
Inceptive Nucleics, Inc                      
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]                      
Collaboration agreement, initial research term   3 years                  
Collaboration agreement, right to terminate, written advance notice period   30 days                  
Purchase price   $ 15,000                  
Roche Collaboration and License Agreement                      
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]                      
Development costs, percentage responsible 40.00%                    
Profit and loss sharing percentage 50.00%                    
Number of performance obligations | performance_obligation 3                    
Roche Collaboration and License Agreement | Roche                      
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]                      
Development costs, percentage responsible 60.00%                    
Profit and loss sharing percentage 50.00%                    
Actual reimbursement of transactional price (as percent)               60.00%      
Transaction price         1,738,167     $ 1,738,167      
Remaining performance obligation         792,200     792,200      
Research and development         66,500 44,800   201,000 105,600    
Total revenues         39,107 326,604   116,636 361,927    
Global Strategic Collaboration | Regeneron Pharmaceuticals                      
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]                      
Number of performance obligations | performance_obligation       2              
Remaining performance obligation         20,900     20,900      
Research and development         9,800 14,600   33,000 46,100    
Upfront payment       $ 10,000              
Maximum royalties and commercial milestone payments upon potential product sale       $ 325,000              
Designated candidates, period after expiration of initial research term       2 years              
Maximum additional milestone payments to be receive upon achievement of certain criteria                   $ 100,000  
Maximum percentage of royalty payments                   20.00%  
Global Strategic Collaboration | Regeneron Pharmaceuticals | Maximum                      
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]                      
Collaborative arrangement milestone payments, per collaboration project                   $ 150,000  
Royalty rate                   20.00%  
Global Strategic Collaboration | Regeneron Pharmaceuticals | Funding At Program Initiation                      
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]                      
Potential proceeds from collaboration arrangement                   $ 2,500  
Global Strategic Collaboration | Regeneron Pharmaceuticals | Funding At Lead Candidate Identification                      
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]                      
Potential proceeds from collaboration arrangement                   $ 2,500  
Global Strategic Collaboration | Regeneron Pharmaceuticals | C5 Monotherapy Obligation                      
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]                      
Fixed consideration       $ 191,500              
Global Strategic Collaboration | Regeneron Pharmaceuticals | Research Services Obligation                      
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]                      
Transaction price         100,500     100,500      
Total revenues         $ 7,345 $ 12,540   $ 13,176 $ 39,306    
v3.26.3
COLLABORATIONS - Schedule of Transaction Price Allocated (Details) - Roche - Roche Collaboration and License Agreement
$ in Thousands
Sep. 30, 2026
USD ($)
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]  
Transaction price $ 1,738,167
Roche License Obligation  
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]  
Transaction price 675,000
Roche Development Services Obligation  
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]  
Transaction price 1,061,167
Roche Technology Transfer Obligation  
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]  
Transaction price $ 2,000
v3.26.3
COLLABORATIONS - Schedule of Net Revenues From Collaborations (Details) - USD ($)
$ in Thousands
 3 Months Ended 9 Months Ended
Sep. 30, 2026
Sep. 30, 2025
Sep. 30, 2026
Sep. 30, 2025
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]        
Total revenues $ 1,458,086 $ 1,249,026 $ 3,916,209 $ 2,616,904
Roche | Roche Collaboration and License Agreement        
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]        
Total revenues 39,107 326,604 116,636 361,927
Roche | Roche License Obligation | Roche Collaboration and License Agreement        
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]        
Total revenues 0 300,000 0 300,000
Roche | Roche Development Services Obligation | Roche Collaboration and License Agreement        
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]        
Total revenues 37,557 25,166 112,196 57,696
Roche | Other | Roche Collaboration and License Agreement        
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]        
Total revenues $ 1,550 $ 1,438 $ 4,440 $ 4,231
v3.26.3
COLLABORATIONS - Schedule of Revenue Recognized under Collaboration (Details) - USD ($)
$ in Thousands
 3 Months Ended 9 Months Ended
Sep. 30, 2026
Sep. 30, 2025
Sep. 30, 2026
Sep. 30, 2025
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]        
Revenue recognized $ 1,458,086 $ 1,249,026 $ 3,916,209 $ 2,616,904
Regeneron Pharmaceuticals        
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]        
Revenue recognized 32,334 22,542 83,690 106,123
Regeneron Pharmaceuticals | Research Services Obligation | Global Strategic Collaboration        
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]        
Revenue recognized 7,345 12,540 13,176 39,306
Regeneron Pharmaceuticals | C5 License Obligation | Global Strategic Collaboration        
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]        
Revenue recognized 0 0 0 21,370
Regeneron Pharmaceuticals | Regeneron Technology Transfer Obligation | Global Strategic Collaboration        
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]        
Revenue recognized 0 0 0 2,431
Regeneron Pharmaceuticals | Other license programs | Global Strategic Collaboration        
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]        
Revenue recognized $ 24,989 $ 10,002 $ 70,514 $ 43,016
v3.26.3
FAIR VALUE MEASUREMENTS - Schedule of Fair Value of Assets Measured on a Recurring Basis (Detail) - USD ($)
$ in Thousands
Sep. 30, 2026
Dec. 31, 2025
Financial assets    
Cash equivalents $ 44,213 $ 23,637
Total financial assets 2,051,466 1,416,233
Commercial paper | Recurring    
Financial assets    
Cash equivalents 9,265  
U.S. treasury securities    
Financial assets    
Marketable debt securities 847,996 653,341
Corporate notes    
Financial assets    
Marketable debt securities 514,295 333,241
U.S. government-sponsored enterprise securities    
Financial assets    
Marketable debt securities 451,805 252,634
Commercial paper    
Financial assets    
Marketable debt securities 18,819 7,017
Municipal securities    
Financial assets    
Marketable debt securities   5,001
Quoted Prices in Active Markets (Level 1)    
Financial assets    
Total financial assets 174,338 141,362
Quoted Prices in Active Markets (Level 1) | Commercial paper | Recurring    
Financial assets    
Cash equivalents 0  
Quoted Prices in Active Markets (Level 1) | U.S. treasury securities    
Financial assets    
Marketable debt securities 0 0
Quoted Prices in Active Markets (Level 1) | Corporate notes    
Financial assets    
Marketable debt securities 0 0
Quoted Prices in Active Markets (Level 1) | U.S. government-sponsored enterprise securities    
Financial assets    
Marketable debt securities 0 0
Quoted Prices in Active Markets (Level 1) | Commercial paper    
Financial assets    
Marketable debt securities 0 0
Quoted Prices in Active Markets (Level 1) | Municipal securities    
Financial assets    
Marketable debt securities   0
Significant Observable Inputs (Level 2)    
Financial assets    
Total financial assets 1,877,128 1,274,871
Significant Observable Inputs (Level 2) | Commercial paper | Recurring    
Financial assets    
Cash equivalents 9,265  
Significant Observable Inputs (Level 2) | U.S. treasury securities    
Financial assets    
Marketable debt securities 847,996 653,341
Significant Observable Inputs (Level 2) | Corporate notes    
Financial assets    
Marketable debt securities 514,295 333,241
Significant Observable Inputs (Level 2) | U.S. government-sponsored enterprise securities    
Financial assets    
Marketable debt securities 451,805 252,634
Significant Observable Inputs (Level 2) | Commercial paper    
Financial assets    
Marketable debt securities 18,819 7,017
Significant Observable Inputs (Level 2) | Municipal securities    
Financial assets    
Marketable debt securities   5,001
Significant Unobservable Inputs (Level 3)    
Financial assets    
Total financial assets 0 0
Significant Unobservable Inputs (Level 3) | Commercial paper | Recurring    
Financial assets    
Cash equivalents 0  
Significant Unobservable Inputs (Level 3) | U.S. treasury securities    
Financial assets    
Marketable debt securities 0 0
Significant Unobservable Inputs (Level 3) | Corporate notes    
Financial assets    
Marketable debt securities 0 0
Significant Unobservable Inputs (Level 3) | U.S. government-sponsored enterprise securities    
Financial assets    
Marketable debt securities 0 0
Significant Unobservable Inputs (Level 3) | Commercial paper    
Financial assets    
Marketable debt securities 0 0
Significant Unobservable Inputs (Level 3) | Municipal securities    
Financial assets    
Marketable debt securities   0
Money market funds    
Financial assets    
Cash equivalents 173,768 140,445
Restricted cash (money market funds) 570 917
Money market funds | Quoted Prices in Active Markets (Level 1)    
Financial assets    
Cash equivalents 173,768 140,445
Restricted cash (money market funds) 570 917
Money market funds | Significant Observable Inputs (Level 2)    
Financial assets    
Cash equivalents 0 0
Restricted cash (money market funds) 0 0
Money market funds | Significant Unobservable Inputs (Level 3)    
Financial assets    
Cash equivalents 0 0
Restricted cash (money market funds) 0 0
U.S. treasury securities    
Financial assets    
Cash equivalents 34,948 18,952
U.S. treasury securities | Quoted Prices in Active Markets (Level 1)    
Financial assets    
Cash equivalents 0 0
U.S. treasury securities | Significant Observable Inputs (Level 2)    
Financial assets    
Cash equivalents 34,948 18,952
U.S. treasury securities | Significant Unobservable Inputs (Level 3)    
Financial assets    
Cash equivalents $ 0 0
U.S. government-sponsored enterprise securities    
Financial assets    
Cash equivalents   2,690
U.S. government-sponsored enterprise securities | Quoted Prices in Active Markets (Level 1)    
Financial assets    
Cash equivalents   0
U.S. government-sponsored enterprise securities | Significant Observable Inputs (Level 2)    
Financial assets    
Cash equivalents   2,690
U.S. government-sponsored enterprise securities | Significant Unobservable Inputs (Level 3)    
Financial assets    
Cash equivalents   0
Commercial paper    
Financial assets    
Cash equivalents   1,995
Commercial paper | Quoted Prices in Active Markets (Level 1)    
Financial assets    
Cash equivalents   0
Commercial paper | Significant Observable Inputs (Level 2)    
Financial assets    
Cash equivalents   1,995
Commercial paper | Significant Unobservable Inputs (Level 3)    
Financial assets    
Cash equivalents   $ 0
v3.26.3
MARKETABLE DEBT SECURITIES - Schedule of Marketable Debt Securities (Detail) - USD ($)
$ in Thousands
Sep. 30, 2026
Dec. 31, 2025
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost $ 1,892,866 $ 1,271,511
Gross Unrealized Gains 32 3,448
Gross Unrealized Losses (15,770) (88)
Fair Value 1,877,128 1,274,871
U.S. treasury securities    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 890,175 670,566
Gross Unrealized Gains 17 1,736
Gross Unrealized Losses (7,248) (9)
Fair Value 882,944 672,293
Corporate notes    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 518,707 332,104
Gross Unrealized Gains 11 1,152
Gross Unrealized Losses (4,423) (15)
Fair Value 514,295 333,241
U.S. government-sponsored enterprise securities    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 455,852 254,829
Gross Unrealized Gains 4 559
Gross Unrealized Losses (4,051) (64)
Fair Value 451,805 255,324
Commercial paper    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 28,132 9,012
Gross Unrealized Gains 0 0
Gross Unrealized Losses (48) 0
Fair Value $ 28,084 9,012
Municipal securities    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost   5,000
Gross Unrealized Gains   1
Gross Unrealized Losses   0
Fair Value   $ 5,001
v3.26.3
MARKETABLE DEBT SECURITIES - Schedule of Fair Value of Marketable Debt Securities (Detail) - USD ($)
$ in Thousands
Sep. 30, 2026
Dec. 31, 2025
Investments, Debt and Equity Securities [Abstract]    
Marketable debt securities $ 1,832,915 $ 1,251,234
Cash and cash equivalents 44,213 23,637
Total $ 1,877,128 $ 1,274,871
v3.26.3
OTHER BALANCE SHEET DETAILS - Schedule of Inventory (Detail) - USD ($)
$ in Thousands
Sep. 30, 2026
Dec. 31, 2025
Organization, Consolidation and Presentation of Financial Statements [Abstract]    
Raw materials $ 18,016 $ 14,184
Work in process 58,798 65,122
Finished goods 40,421 32,338
Total inventory $ 117,235 $ 111,644
v3.26.3
OTHER BALANCE SHEET DETAILS - Narrative (Detail) - USD ($)
$ in Millions
Sep. 30, 2026
Dec. 31, 2025
Organization, Consolidation and Presentation of Financial Statements [Abstract]    
Long-term inventory $ 11.3 $ 28.9
v3.26.3
OTHER BALANCE SHEET DETAILS - Schedule of Reconciliation of Cash, Cash Equivalents and Restricted Cash (Detail) - USD ($)
$ in Thousands
Sep. 30, 2026
Dec. 31, 2025
Sep. 30, 2025
Dec. 31, 2024
Organization, Consolidation and Presentation of Financial Statements [Abstract]        
Cash and cash equivalents $ 1,754,340 $ 1,657,250 $ 1,490,249  
Total restricted cash included in other assets 1,477   2,553  
Total cash, cash equivalents, and restricted cash shown in the condensed consolidated statements of cash flows $ 1,755,817 $ 1,658,807 $ 1,492,802 $ 968,652
v3.26.3
OTHER BALANCE SHEET DETAILS - Schedule of Changes in Accumulated Other Comprehensive Loss (Details) - USD ($)
$ in Thousands
 3 Months Ended 9 Months Ended
Sep. 30, 2026
Jun. 30, 2026
Mar. 31, 2026
Sep. 30, 2025
Jun. 30, 2025
Mar. 31, 2025
Sep. 30, 2026
Sep. 30, 2025
AOCI Attributable to Parent, Net of Tax [Roll Forward]                
Beginning balance $ 1,354,118 $ 1,075,380 $ 789,176 $ 555,345 $ 426,140 $ 67,088 $ 789,176 $ 67,088
Other comprehensive loss before reclassifications             (19,947) 13,765
Amounts reclassified from accumulated other comprehensive loss             (4,617) (1,022)
Total other comprehensive (loss) income (12,523) (7,244) (4,797) 8,177 7,565 (2,999) (24,564) 12,743
Ending balance 3,603,852 1,354,118 1,075,380 580,247 555,345 426,140 3,603,852 580,247
Accumulated Other Comprehensive Loss                
AOCI Attributable to Parent, Net of Tax [Roll Forward]                
Beginning balance (32,138) (24,894) (20,097) (29,952) (37,517) (34,518) (20,097) (34,518)
Total other comprehensive (loss) income (12,523) (7,244) (4,797) 8,177 7,565 (2,999)    
Ending balance (44,661) $ (32,138) (24,894) (21,775) $ (29,952) (37,517) (44,661) (21,775)
Loss on Investment in Joint Venture                
AOCI Attributable to Parent, Net of Tax [Roll Forward]                
Beginning balance     (32,792)     (32,792) (32,792) (32,792)
Other comprehensive loss before reclassifications             0 0
Amounts reclassified from accumulated other comprehensive loss             0 0
Total other comprehensive (loss) income             0 0
Ending balance (32,792)     (32,792)     (32,792) (32,792)
Defined Benefit Pension Plans, Net of Tax                
AOCI Attributable to Parent, Net of Tax [Roll Forward]                
Beginning balance     (3,268)     (4,249) (3,268) (4,249)
Other comprehensive loss before reclassifications             0 0
Amounts reclassified from accumulated other comprehensive loss             267 161
Total other comprehensive (loss) income             267 161
Ending balance (3,001)     (4,088)     (3,001) (4,088)
Unrealized Gains (Losses) from Debt Securities                
AOCI Attributable to Parent, Net of Tax [Roll Forward]                
Beginning balance     3,360     1,544 3,360 1,544
Other comprehensive loss before reclassifications             (14,214) 3,001
Amounts reclassified from accumulated other comprehensive loss             (4,884) (1,183)
Total other comprehensive (loss) income             (19,098) 1,818
Ending balance (15,738)     3,362     (15,738) 3,362
Foreign Currency Translation Adjustment                
AOCI Attributable to Parent, Net of Tax [Roll Forward]                
Beginning balance     $ 12,603     $ 979 12,603 979
Other comprehensive loss before reclassifications             (5,733) 10,764
Amounts reclassified from accumulated other comprehensive loss             0 0
Total other comprehensive (loss) income             (5,733) 10,764
Ending balance $ 6,870     $ 11,743     $ 6,870 $ 11,743
v3.26.3
CONVERTIBLE DEBT AND OTHER FINANCING - Convertible Senior Notes (Details)
 1 Months Ended 3 Months Ended 9 Months Ended 12 Months Ended
Sep. 12, 2025
USD ($)
day
$ / shares
Sep. 15, 2022
day
$ / shares
Sep. 12, 2022
USD ($)
Dec. 31, 2025
USD ($)
$ / shares
Sep. 30, 2025
USD ($)
Sep. 30, 2026
USD ($)
$ / shares
Sep. 30, 2025
USD ($)
Sep. 30, 2026
USD ($)
$ / shares
Sep. 30, 2025
USD ($)
Dec. 31, 2025
USD ($)
$ / shares
Sep. 10, 2025
USD ($)
Sep. 08, 2025
USD ($)
Sep. 13, 2022
USD ($)
Debt Instrument [Line Items]                          
Common stock, par value (in dollars per share) | $ / shares       $ 0.01   $ 0.01   $ 0.01   $ 0.01      
Cash paid for interest               $ 195,565,000 $ 159,565,000        
Repurchase cost including accrued and unpaid interest               0 1,102,659,000        
Loss related to convertible debt           $ 0 $ 39,146,000 0 39,146,000 $ 39,100,000      
Repurchase of 1.00% Convertible Senior Notes due 2027                   430,400,000      
2028 Notes | Convertible debt                          
Debt Instrument [Line Items]                          
Aggregate principal amount $ 661,300,000                        
Interest rate (as percent)                       0.00%  
Debt instrument, conversion price (in dollars per share) | $ / shares $ 670.11                        
Initial conversion price, premium, percentage 40.00%                        
Debt instrument conversion ratio 0.0014923                        
Share price (in dollars per share) | $ / shares $ 478.63                        
Long term debt outstanding       $ 647,200,000   651,100,000   651,100,000   647,200,000      
Debt issuance costs       14,000,000.0   10,200,000   10,200,000   14,000,000.0      
Fair value of long-term debt       $ 637,000,000.0   $ 605,900,000   $ 605,900,000   $ 637,000,000.0      
Effective interest rate (as percent)       1.00%   1.00%   1.00%   1.00%      
Interest rate (as percent)               0.00%          
2028 Notes | Debt Conversion Terms One | Convertible debt                          
Debt Instrument [Line Items]                          
Trading days threshold | day 20                        
Consecutive trading days threshold | day 30                        
Percentage of stock price trigger 130.00%                        
2028 Notes | Debt Conversion Terms Two | Convertible debt                          
Debt Instrument [Line Items]                          
Trading days threshold | day 5                        
Consecutive trading days threshold | day 10                        
Percentage of stock price trigger 98.00%                        
2028 Notes | Debt Conversion Terms Three | Convertible debt                          
Debt Instrument [Line Items]                          
Trading days threshold | day 20                        
Consecutive trading days threshold | day 30                        
Percentage of stock price trigger 130.00%                        
Debt instrument, redemption price percentage 100.00%                        
Sinking fund payment $ 0                        
Initial 2028 Notes | Convertible debt                          
Debt Instrument [Line Items]                          
Aggregate principal amount                       $ 575,000,000.0  
Initial 2028 Notes | Debt Conversion Terms Three | Convertible debt                          
Debt Instrument [Line Items]                          
Debt instrument, redemption price percentage 100.00%                        
Additional 2028 Notes | Convertible debt                          
Debt Instrument [Line Items]                          
Aggregate principal amount                     $ 86,300,000    
Convertible Senior Notes Due 2027 | Convertible debt                          
Debt Instrument [Line Items]                          
Aggregate principal amount     $ 900,000,000.0                   $ 1,040,000,000.00
Debt instrument, conversion price (in dollars per share) | $ / shares   $ 286.20                      
Initial conversion price, premium, percentage   35.00%                      
Debt instrument conversion ratio   0.0034941                      
Long term debt outstanding       $ 360,500,000   $ 361,500,000   $ 361,500,000   $ 360,500,000      
Debt issuance costs       2,300,000   1,300,000   1,300,000   2,300,000      
Fair value of long-term debt       $ 534,100,000   $ 391,800,000   $ 391,800,000   $ 534,100,000      
Effective interest rate (as percent)       1.00%   1.00%   1.00%   1.00%      
Repayments of long-term debt               $ 637,800,000          
Interest rate (as percent)     1.00%         1.00%          
Common stock, par value (in dollars per share) | $ / shares   $ 212.00                      
Debt, repurchased       $ 34,400,000 $ 637,800,000   $ 637,800,000   $ 637,800,000 $ 34,400,000      
Cash paid for interest       100,000 3,100,000                
Repurchase cost including accrued and unpaid interest       52,300,000 $ 1,110,000,000                
Loss related to convertible debt                   3,300,000      
Repurchase of 1.00% Convertible Senior Notes due 2027                   14,800,000      
Long term debt outstanding       $ 362,800,000   $ 362,800,000   $ 362,800,000   $ 362,800,000      
Convertible Senior Notes Due 2027 | Debt Conversion Terms One | Convertible debt                          
Debt Instrument [Line Items]                          
Trading days threshold | day   20                      
Consecutive trading days threshold | day   30                      
Percentage of stock price trigger   130.00%                      
Convertible Senior Notes Due 2027 | Debt Conversion Terms Two | Convertible debt                          
Debt Instrument [Line Items]                          
Trading days threshold | day   5                      
Consecutive trading days threshold | day   10                      
Percentage of stock price trigger   98.00%                      
Convertible Senior Notes Due 2027 | Debt Conversion Terms Four | Convertible debt                          
Debt Instrument [Line Items]                          
Trading days threshold | day   20                      
Consecutive trading days threshold | day   30                      
Percentage of stock price trigger   130.00%                      
Debt instrument, redemption price percentage   100.00%                      
Convertible Senior Notes Due 2027, Additional Amount | Convertible debt                          
Debt Instrument [Line Items]                          
Aggregate principal amount                         $ 135,000,000.0
v3.26.3
CONVERTIBLE DEBT AND OTHER FINANCING - Capped Call Transactions (Details)
$ / shares in Units, $ in Thousands
 1 Months Ended 3 Months Ended
Sep. 30, 2025
USD ($)
$ / shares
Sep. 30, 2025
USD ($)
Sep. 30, 2026
$ / shares
Dec. 31, 2025
$ / shares
Sep. 12, 2022
$ / shares
$ / Unit
Debt Instrument [Line Items]          
Purchase of capped calls related to —% Convertible Senior Notes due 2028 | $ $ 35,300 $ 35,311      
Common stock, par value (in dollars per share)     $ 0.01 $ 0.01  
2022 Capped Call Transactions | Convertible debt          
Debt Instrument [Line Items]          
Cap price (in dollars per share) | $ / Unit         424.00
Premium on capped call transactions         1
Common stock, par value (in dollars per share)         $ 212.00
Call Option          
Debt Instrument [Line Items]          
Cap price (in dollars per share) $ 837.61        
v3.26.3
CONVERTIBLE DEBT AND OTHER FINANCING - Revolving Credit Agreement (Details) - Revolving Credit Agreement - Line of Credit
$ in Millions
Sep. 30, 2025
USD ($)
Sep. 30, 2026
USD ($)
Dec. 31, 2025
USD ($)
Debt Instrument [Line Items]      
Issuance of letters of credit   $ 17.5 $ 17.5
Revolving Credit Facility      
Debt Instrument [Line Items]      
Aggregate principal amount $ 500.0    
Covenant, leverage ratio, minimum 3.75    
Covenant, interest coverage ratio, maximum 3.00    
Outstanding borrowings   $ 0.0 $ 0.0
Revolving Credit Facility | Minimum      
Debt Instrument [Line Items]      
Commitment fee on the unused portion of leverage ratio 0.20%    
Revolving Credit Facility | Minimum | Base Rate      
Debt Instrument [Line Items]      
Leverage ratio 0.50%    
Revolving Credit Facility | Minimum | Secured Overnight Financing Rate (SOFR)      
Debt Instrument [Line Items]      
Leverage ratio 1.50%    
Revolving Credit Facility | Maximum      
Debt Instrument [Line Items]      
Commitment fee on the unused portion of leverage ratio 0.35%    
Revolving Credit Facility | Maximum | Base Rate      
Debt Instrument [Line Items]      
Leverage ratio 1.50%    
Revolving Credit Facility | Maximum | Secured Overnight Financing Rate (SOFR)      
Debt Instrument [Line Items]      
Leverage ratio 2.50%    
Letter of Credit      
Debt Instrument [Line Items]      
Aggregate principal amount $ 150.0    
v3.26.3
LIABILITIES RELATED TO THE SALE OF FUTURE ROYALTIES AND DEVELOPMENT FUNDING - Additional Information (Detail)
$ in Thousands
 1 Months Ended
Sep. 30, 2026
USD ($)
Sep. 30, 2026
USD ($)
Jun. 30, 2026
USD ($)
Sep. 30, 2025
USD ($)
Mar. 31, 2025
USD ($)
payment
Sep. 30, 2023
USD ($)
payment
Aug. 31, 2020
USD ($)
program
Apr. 30, 2020
USD ($)
Jan. 01, 2030
Dec. 31, 2025
USD ($)
Liability Related To The Sale Of Future Royalties [Line Items]                    
Number of cardiometabolic programs | program             2      
Liabilities related to the sale of future royalties and development funding $ 272,037 $ 272,037               $ 220,068
Liabilities related to the sale of future royalties and development funding, net of current portion $ 1,462,828 $ 1,462,828               $ 1,470,341
Vutrisiran                    
Liability Related To The Sale Of Future Royalties [Line Items]                    
Effective interest rate 47.00% 47.00%               46.00%
Liabilities related to the sale of future royalties and development funding $ 76,000 $ 76,000               $ 94,500
Liabilities related to the sale of future royalties and development funding, net of current portion $ 94,400 $ 94,400               $ 99,700
Zilebesrian                    
Liability Related To The Sale Of Future Royalties [Line Items]                    
Effective interest rate 31.00% 31.00%               32.00%
Liabilities related to the sale of future royalties and development funding $ 6,900 $ 6,900               $ 6,800
Liabilities related to the sale of future royalties and development funding, net of current portion 18,300 18,300               10,300
Blackstone Life Sciences | Vutrisiran and ALN-AGT | Net revenues from collaborations                    
Liability Related To The Sale Of Future Royalties [Line Items]                    
Maximum funding             $ 150,000      
Blackstone Life Sciences | HELIOS-B Phase 3 Clinical Trial | Net revenues from collaborations                    
Liability Related To The Sale Of Future Royalties [Line Items]                    
Maximum funding   70,000                
Blackstone Life Sciences | ALN-AGT Phase 2 Clinical Trial                    
Liability Related To The Sale Of Future Royalties [Line Items]                    
Development milestone payable           $ 84,500        
Blackstone Life Sciences | ALN-AGT Phase 2 Clinical Trial | Net revenues from collaborations                    
Liability Related To The Sale Of Future Royalties [Line Items]                    
Maximum funding   26,000                
Number of quarterly payments | payment           16        
Fixed payment, term (in years)           4 years        
Blackstone Life Sciences | ALN-AGT Phase 3 Clinical Trial | Net revenues from collaborations                    
Liability Related To The Sale Of Future Royalties [Line Items]                    
Maximum funding 24,000   $ 36,000 $ 36,000            
Development milestone payable           $ 243,000        
Number of quarterly payments | payment           16        
Fixed payment, term (in years)           4 years        
Blackstone Life Sciences | Vutrisiran                    
Liability Related To The Sale Of Future Royalties [Line Items]                    
Development milestone payable         $ 175,000          
Blackstone Life Sciences | Vutrisiran | Net revenues from collaborations                    
Liability Related To The Sale Of Future Royalties [Line Items]                    
Royalties payable, percent             1.00%      
Royalties payable, term (in years)             10 years      
Number of quarterly payments | payment         8          
Fixed payment, term (in years)         2 years          
Blackstone Life Sciences | Development Milestone                    
Liability Related To The Sale Of Future Royalties [Line Items]                    
Development milestone payable             $ 175,000      
Vutrisiran                    
Liability Related To The Sale Of Future Royalties [Line Items]                    
Royalty and development funding liability, fair value 479,300 479,300               541,300
Zilebesrian                    
Liability Related To The Sale Of Future Royalties [Line Items]                    
Royalty and development funding liability, fair value 120,100 120,100               116,200
Blackstone Group Inc.                    
Liability Related To The Sale Of Future Royalties [Line Items]                    
Liabilities related to the sale of future royalties and development funding 189,200 189,200               118,800
Liabilities related to the sale of future royalties and development funding, net of current portion $ 1,350,000 $ 1,350,000               $ 1,360,000
Blackstone Group Inc. | Net revenues from collaborations                    
Liability Related To The Sale Of Future Royalties [Line Items]                    
Collaborative arrangement, royalties and commercial milestones acquired by collaborator, percent               50.00%    
Commercial milestones acquired by collaborator, percent               75.00%    
Expected royalty interest payments               $ 1,000,000    
Consideration received               $ 1,000,000    
Interest rate 15.00% 15.00%               10.00%
Liabilities related to the sale of future royalties and development funding, net of current portion $ 1,539,305 $ 1,539,305               $ 1,479,209
Closing costs 7,700 7,700               8,300
Fair value of liability $ 2,030,000 $ 2,030,000               $ 1,610,000
Blackstone Group Inc. | Net revenues from collaborations | Forecast                    
Liability Related To The Sale Of Future Royalties [Line Items]                    
Collaborative arrangement, royalties and commercial milestones acquired by collaborator, percent                 55.00%  
v3.26.3
LIABILITIES RELATED TO THE SALE OF FUTURE ROYALTIES AND DEVELOPMENT FUNDING - Schedule of Fair Value, Liabilities (Details) - Obligations
$ in Thousands
 9 Months Ended
Sep. 30, 2026
USD ($)
Vutrisiran  
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]  
Beginning balance $ 194,153
Interest expense 69,133
Amount paid (92,908)
Ending balance 170,378
Zilebesrian  
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]  
Beginning balance 17,047
Interest expense 5,979
Amount paid (15,844)
Amount received 18,000
Ending balance $ 25,182
v3.26.3
LIABILITIES RELATED TO THE SALE OF FUTURE ROYALTIES AND DEVELOPMENT FUNDING - Schedule of Future Royalties (Details) - Blackstone Group Inc. - Net revenues from collaborations
$ in Thousands
 9 Months Ended
Sep. 30, 2026
USD ($)
Royalty Liability Rollforward [Abstract]  
Beginning balance $ 1,479,209
Interest expense 151,534
Payments (91,438)
Ending balance $ 1,539,305
v3.26.3
STOCK-BASED COMPENSATION - Schedule of Share-Based Compensation Expenses Included Operating Costs and Expense (Detail) - USD ($)
$ in Thousands
 3 Months Ended 9 Months Ended
Sep. 30, 2026
Sep. 30, 2025
Sep. 30, 2026
Sep. 30, 2025
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Total stock-based compensation expense $ 79,118 $ 108,211 $ 235,897 $ 276,603
Capitalized stock-based compensation costs 1,104 1,128 3,314 3,383
Total stock-based compensation charges 80,222 109,339 239,211 279,986
Income Statement Location: us-gaap:ResearchAndDevelopmentExpense        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Total stock-based compensation expense 32,861 48,725 98,867 122,075
Income Statement Location: us-gaap:SellingGeneralAndAdministrativeExpense        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Total stock-based compensation expense $ 46,257 $ 59,486 $ 137,030 $ 154,528
v3.26.3
NET INCOME (LOSS) PER COMMON SHARE - Schedule of Basic and Diluted Net (Loss) Income Per Share (Detail) - USD ($)
$ / shares in Units, shares in Thousands, $ in Thousands
 3 Months Ended 9 Months Ended
Sep. 30, 2026
Jun. 30, 2026
Mar. 31, 2026
Sep. 30, 2025
Jun. 30, 2025
Mar. 31, 2025
Sep. 30, 2026
Sep. 30, 2025
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]                
Net income, as reported $ 2,167,335 $ 164,494 $ 205,991 $ 292,683 $ (72,228) $ (18,251) $ 2,537,820 $ 202,204
Adjustment for the elimination of interest expense on the convertible debt 2,067     1,608     7,091 0
Net income, for use in diluted income per share $ 2,169,402     $ 294,291     $ 2,544,911 $ 202,204
Weighted-average common shares - basic (in shares) 133,828     131,447     133,444 130,590
Effect of dilutive securities:                
Convertible debt (in shares) 2,255     1,583     2,255 0
Weighted-average common shares - diluted (in shares) 138,040     137,348     138,184 134,146
Net income per common share — basic (in dollars per share) $ 16.19     $ 2.23     $ 19.02 $ 1.55
Net income per common share — diluted (in dollars per share) $ 15.72     $ 2.14     $ 18.42 $ 1.51
Options to purchase common stock, inclusive of performance-based stock options                
Effect of dilutive securities:                
Options, RSUs, and ESPP (in shares) 1,305     2,454     1,605 2,245
Restricted stock units, inclusive of performance-based restricted stock units                
Effect of dilutive securities:                
Options, RSUs, and ESPP (in shares) 650     1,847     877 1,304
Employee stock purchase program                
Effect of dilutive securities:                
Options, RSUs, and ESPP (in shares) 2     17     3 7
v3.26.3
NET INCOME (LOSS) PER COMMON SHARE - Schedule of Common Share Equivalents Excluded from Calculation of Net Loss Per Common Share (Detail) - shares
shares in Thousands
 3 Months Ended 9 Months Ended
Sep. 30, 2026
Sep. 30, 2025
Sep. 30, 2026
Sep. 30, 2025
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]        
Anti-dilutive securities excluded from computation of earnings per share (in shares) 1,357 1,791 879 3,655
Options to purchase common stock, inclusive of performance-based stock options        
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]        
Anti-dilutive securities excluded from computation of earnings per share (in shares) 424 0 298 157
Unvested restricted stock units, inclusive of performance-based restricted stock units        
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]        
Anti-dilutive securities excluded from computation of earnings per share (in shares) 933 3 581 7
Convertible debt        
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]        
Anti-dilutive securities excluded from computation of earnings per share (in shares) 0 1,788 0 3,491
v3.26.3
NET INCOME (LOSS) PER COMMON SHARE - Narrative (Detail) - shares
shares in Thousands
 3 Months Ended 9 Months Ended
Sep. 30, 2026
Sep. 30, 2025
Sep. 30, 2026
Sep. 30, 2025
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]        
Anti-dilutive securities excluded from computation of earnings per share (in shares) 1,357 1,791 879 3,655
2022 and 2025 Capped Call Transactions        
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]        
Anti-dilutive securities excluded from computation of earnings per share (in shares) 8,500 5,800 8,500 5,400
v3.26.3
COMMITMENTS AND CONTINGENCIES (Details) - USD ($)
$ in Thousands
Sep. 30, 2026
Dec. 31, 2025
Commitments and Contingencies Disclosure [Abstract]    
Loss contingencies accrued $ 0 $ 0
v3.26.3
SEGMENT INFORMATION - Narrative (Details)
 9 Months Ended
Sep. 30, 2026
segment
Segment Reporting [Abstract]  
Number of reporting segments 1
Number of Reportable Segments 1
v3.26.3
SEGMENT INFORMATION - Schedule of Expenses by Segment (Details) - USD ($)
$ in Thousands
 3 Months Ended 9 Months Ended
Sep. 30, 2026
Sep. 30, 2025
Sep. 30, 2026
Sep. 30, 2025
Segment Reporting [Line Items]        
Total research and development expense $ 408,538 $ 358,814 $ 1,186,538 $ 947,557
Total selling, general and administrative expense 342,000 322,076 1,012,473 885,339
Single Reportable Segment        
Segment Reporting [Line Items]        
Total research and development expense 408,538 358,814 1,186,538 947,557
Total selling, general and administrative expense 342,000 322,076 1,012,473 885,339
Compensation and related | Single Reportable Segment        
Segment Reporting [Line Items]        
Total selling, general and administrative expense 167,544 188,669 497,240 511,339
Consulting and professional services | Single Reportable Segment        
Segment Reporting [Line Items]        
Total selling, general and administrative expense 118,917 88,738 344,815 236,062
Occupancy and all other costs | Single Reportable Segment        
Segment Reporting [Line Items]        
Total selling, general and administrative expense 55,539 44,669 170,418 137,938
Clinical research and outside services | Single Reportable Segment        
Segment Reporting [Line Items]        
Total research and development expense 239,525 170,756 683,008 438,791
Compensation and related | Single Reportable Segment        
Segment Reporting [Line Items]        
Total research and development expense 121,722 146,089 371,410 388,726
Occupancy and all other costs | Single Reportable Segment        
Segment Reporting [Line Items]        
Total research and development expense $ 47,291 $ 41,969 $ 132,120 $ 120,040
v3.26.3
INCOME TAXES (Details) - USD ($)
$ in Thousands
 3 Months Ended 9 Months Ended
Sep. 30, 2026
Sep. 30, 2025
Sep. 30, 2026
Sep. 30, 2025
Income Tax Disclosure [Abstract]        
Benefit from (provision for) income taxes $ 1,871,525 $ 12,115 $ 1,842,551 $ (34,687)
Valuation allowance, deferred tax asset, increase (decrease), amount $ 1,950,000