Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Operating activities
Net loss	$ (177,550)	$ (17,460)
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	1,380	710
(Gain) loss on warrants inherited in acquisiton of Quellis	(700)
Other non-cash items	10	23
Changes in assets and liabilities:
Prepaid expenses and other current assets	999	1,079
Right-of-use asset-operating	(85)	134
Accounts payable	(2,900)	(26)
Accrued expenses	(1,882)	1,085
Net cash used in operating activities	(16,116)	(14,455)
Investing activities
Purchases of short-term investments		(42,777)
Sales and maturities of short-term investments	20,000	67,110
Cash acquired in acquisition of Quellis	6,466
Purchases of property and equipment	(21)	(23)
Net cash provided by (used in) investing activities	26,445	24,310
Financing activities
Proceeds from public offerings, 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		7,330
Net cash provided by financing activities	104,261	31,889
Net increase in cash, cash equivalents and restricted cash	114,590	41,744
Cash, cash equivalents and restricted cash, beginning of period	25,051	10,376
Cash, cash equivalents and restricted cash, end of period	139,641	$ 52,120
Supplemental disclosure of cash flow information
Conversion of Series X Preferred Stock into common stock	165,549
Non-cash dividend on convertible preferred stock	24,437
Reclassification of warrant liability to additional paid-in capital	$ 3,468