CONSOLIDATED STATEMENTS OF CASH FLOW - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Cash flows from operating activities:
Net loss	$ (70,511)	$ (59,780)	$ (50,878)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	3,068	3,929	4,858
Amortization and premium of marketable securities, net	(3,209)	(729)	(1,140)
(Gain) loss on sale or disposal of assets	(24)	(55)	11
Intangible asset impairment	3,500	18,000
Other asset impairment			1,800
Gain on fair value remeasurement of contingent consideration	(1,405)	(4,218)	(1,294)
Non-cash income tax benefit	(227)	(1,167)
Stock-based compensation expense	8,953	3,915	4,551
Changes in operating assets and liabilities:
Accounts and other receivables	1,574	(787)	2,274
Prepaid and other current assets	(1,871)	(334)	362
Other assets	(5)		(39)
Accounts payable and accrued expenses	3,653	1,638	(321)
Other liabilities	(4,405)	(816)	(6,599)
Net cash used in operating activities	(60,909)	(40,404)	(46,415)
Cash flows from investing activities:
Sales and maturities of marketable securities	174,947	123,600	113,173
Purchases of marketable securities	(389,881)	(220,321)	(95,382)
Acquisition of property and equipment	(1,249)	(1,552)	(731)
Proceeds from sale or disposal of assets	27	55	20
Net cash (used in) provided by investing activities	(216,156)	(98,218)	17,080
Cash flows from financing activities:
Net proceeds from stock issuances	269,893	170,792	16,248
Proceeds from issuance of stock from employee benefit plans	2,479	434	9
Issuance of term loan		2,962
Payment of term loan		(2,962)
Net cash provided by financing activities	272,372	171,226	16,257
Net (decrease) increase in cash and cash equivalents	(4,693)	32,604	(13,078)
Cash and cash equivalents at beginning of period	43,836	11,232	24,310
Cash and cash equivalents at end of period	39,143	43,836	11,232
Non-cash investing activities
Accrued construction in progress	$ 289	$ 221	$ 25