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]
Other comprehensive income (loss)	4,566
Net income (loss)	(90,479)
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)
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)
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]
Other comprehensive income (loss)	(12,041)
Net income (loss)	$ 370,485
Ending balance (in shares) at Jun. 30, 2026	133,734		133,734
Ending balance at Jun. 30, 2026	$ 1,354,118		$ 1,337	7,716,958	(32,138)	(6,332,039)
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		133,734
Ending balance at Jun. 30, 2026	$ 1,354,118		$ 1,337	$ 7,716,958	$ (32,138)	$ (6,332,039)

ALNYLAM PHARMACEUTICALS, INC. 10-Q