CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Cash flows from operating activities:
Net loss	$ (16,109)	$ (9,927)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	36	43
Non-cash lease expense	239	202
Stock-based compensation expense	1,718	1,099
Non-cash imputed interest expense related to the sale of future royalties	(18)	(20)
Net amortization of premiums and discounts on marketable securities	380	195
Changes in operating assets and liabilities:
Accounts receivable	1,164	860
Prepaid expenses and other assets	(158)	(2,049)
Accounts payable and accrued and other liabilities	(3,890)	(2,301)
Operating lease liability	(177)	(1,281)
Total adjustments	(706)	(3,252)
Net cash used in operating activities	(16,815)	(13,179)
Cash flows from investing activities:
Purchase of investments	(24,972)	(9,071)
Sales and maturities of investments	21,900	5,000
Purchase of property and equipment	(11)	0
Net cash provided by (used in) investing activities	(3,083)	(4,071)
Cash flows from financing activities:
Proceeds from issuance of common stock under the Company's share-based compensation plan	0	79
Payment of liability of future royalties, net of imputed interest	(1,648)	(1,408)
Net cash provided by (used in) financing activities	(1,648)	(1,329)
Net decrease in cash and cash equivalents and restricted cash	(21,546)	(18,579)
Cash and cash equivalents and restricted cash, beginning of period	40,740	130,426
Cash and cash equivalents and restricted cash, end of period	19,194	111,847
Supplemental cash flow data:
Issuance costs in accrued expenses and accounts payable	172	281
Cash paid for interest	1,074	1,193
Decrease in right-of-use assets and operating lease liabilities resulting from lease modification	$ (1,098)	$ 0