CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021
Cash flows from operating activities:
Net loss	$ (32,049)	$ (20,765)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	80	84
Non-cash lease expense	529	407
Stock-based compensation expense	3,684	2,374
Non-cash imputed interest expense related to the sale of future royalties	6	3
Net amortization of premiums and discounts on marketable securities	575	634
Gain on forgiveness of PPP Loan	0	(890)
Changes in operating assets and liabilities:
Accounts receivable	829	664
Prepaid expenses and other assets	(536)	(366)
Accounts payable and accrued and other liabilities	(1,671)	(557)
Operating lease liability	(394)	(1,426)
Total adjustments	3,102	927
Net cash used in operating activities	(28,947)	(19,838)
Cash flows from investing activities:
Purchase of investments	(35,774)	(54,947)
Sales and maturities of investments	61,395	22,105
Purchase of property and equipment	(364)	0
Net cash provided by (used in) investing activities	25,257	(32,842)
Cash flows from financing activities:
Proceeds from issuance of common stock under the Company's share-based compensation plan	149	195
Payment of liability of future royalties, net of imputed interest	(2,556)	(2,099)
Net cash provided by (used in) financing activities	(2,407)	(1,904)
Net decrease in cash and cash equivalents and restricted cash	(6,097)	(54,584)
Cash and cash equivalents and restricted cash, beginning of period	40,740	130,426
Cash and cash equivalents and restricted cash, end of period	34,643	75,842
Supplemental cash flow data:
Cash paid for interest	2,091	2,305
Decrease in right-of-use assets and operating lease liabilities resulting from lease modification	$ (191)	$ 0