Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Operating activities
Net loss	$ (185,421)	$ (28,322)
Reconciliation of net loss to net cash used in operating activities:
Non-cash portion of acquired in-process research and development	164,612
Stock-based compensation expense	2,390	1,085
Net gain on warrants inherited in acquisition of Quellis	(315)
Other non-cash items	15	42
Changes in assets and liabilities:
Prepaid expenses and other assets	(1,092)	121
Right-of-use asset-operating	(96)	125
Accounts payable	(2,947)	211
Accrued expenses	(1,011)	2,314
Net cash used in operating activities	(23,865)	(24,424)
Investing activities
Purchases of short-term investments		(42,777)
Sales and maturities of short-term investments	20,000	69,110
Cash acquired in acquisition of Quellis	6,466
Purchases of property and equipment	(21)	(23)
Net cash provided by investing activities	26,445	26,310
Financing activities
Proceeds from underwritten public offering, net of issuance costs		24,559
Proceeds from private offering of public equity, net of issuance costs	104,261
Proceeds from at-the-market offering, net of issuance costs		16,270
Proceeds from exercise of common stock options	6
Net cash provided by financing activities	104,267	40,829
Net increase in cash, cash equivalents and restricted cash	106,847	42,715
Cash, cash equivalents and restricted cash, beginning of period	25,051	10,376
Cash, cash equivalents and restricted cash, end of period	131,898	$ 53,091
Supplemental disclosure of cash flow information
Conversion of Series X Preferred Stock into common stock	168,920
Non-cash dividend on convertible preferred stock	24,437
Reclassification of warrant liability to additional paid-in capital	$ 3,468