CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Cash flows from operating activities:
Net loss	$ (89,756)	$ (78,280)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	646	761
Non-cash lease cost	471	585
Share-based compensation	9,430	4,888
Unrealized foreign currency transaction (gain) loss	13	(330)
Accretion of premium (discount) on marketable securities	251	(32)
Change in fair value of derivative liabilities	(204)
Non-cash interest expense associated with the sale of future royalties	1,940
Changes in operating assets and liabilities:
Other receivables	3,050	2,430
Prepaid expenses and other current assets	(2,808)	(1,240)
Tax incentive receivables	782	(254)
Other assets	(319)	(1,890)
Accounts payable	(53)	(2,975)
Accrued expenses and other current liabilities	2,109	(9,130)
Deferred revenue, current and non-current	10,643
Other long-term liabilities	(39)	(72)
Operating lease liabilities	(503)	(333)
Net cash used in operating activities	(64,347)	(85,872)
Cash flows from investing activities:
Purchases of marketable securities	(43,915)	(45,723)
Proceeds from maturities of marketable securities	51,548	56,350
Write-offs (purchases) of property and equipment	39	(157)
Net cash provided by investing activities	7,672	10,470
Cash flows from financing activities:
Proceeds from Issuance of Common Stock	7,831	13,166
Proceeds from sale of future royalties, net	49,750
Transaction costs from sale of future royalties	(2,210)
Royalty payments	(60)
Payment of offering costs	(248)	(953)
Proceeds from stock option exercises	1,450	2,189
Net cash provided by financing activities	84,050	130,881
Net increase (decrease) in cash and cash equivalents	27,375	55,479
Cash and cash equivalents at beginning of period	85,209	29,730
Cash and cash equivalents at end of period	112,584	85,209
Supplemental disclosure of non-cash activities:
Right-of-use assets and lease obligations recorded upon commencement or amendment of lease agreements	0	2,626
Rights Offering
Cash flows from financing activities:
Proceeds from Issuance of Common Stock		9,416
Underwritten Public Offering Member
Cash flows from financing activities:
Proceeds from Issuance of Common Stock		56,078
Pfizer Purchase Agreement [Member]
Cash flows from financing activities:
Proceeds from Issuance of Common Stock	$ 27,537
Series C Preferred Stock [Member] | Rights Offering
Cash flows from financing activities:
Proceeds from issuance of Preferred Shares		20,583
Series D Preferred Stock [Member] | Underwritten Public Offering Member
Cash flows from financing activities:
Proceeds from issuance of Preferred Shares		$ 30,402