Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Cash flows from operating activities:
Net loss	$ (45,436)	$ (29,908)	$ (32,141)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	158	144	125
Non-cash lease expense	828	605	956
Stock-based compensation expense	5,279	2,698	2,658
Amortization of debt issuance costs	0	0	8
Non-cash imputed interest expense related to the sale of future royalties	36	45	287
Amortization of premiums and (discounts) on marketable securities	1,402	33	(64)
Gain on forgiveness of PPP loan	(890)	0	0
Loss on extinguishment of debt	0	0	3,495
Loss on disposal of fixed assets	0	24	29
Changes in operating assets and liabilities:
Accounts receivable	(181)	201	(380)
Prepaid expenses and other assets	(2,049)	(153)	(237)
Accounts payable and accrued and other liabilities	4,965	1,000	60
Operating lease liability	(1,731)	(428)	(1,001)
Total adjustments	7,817	4,169	5,936
Net cash used in operating activities	(37,619)	(25,739)	(26,205)
Cash flows from investing activities:
Purchases of investments	(93,125)	(53,449)	(11,465)
Sales and maturities of investments	45,230	5,078	7,050
Purchases of property and equipment	0	(677)	(41)
Net cash used in investing activities	(47,895)	(49,048)	(4,456)
Cash flows from financing activities:
Proceeds from PPP Loan	0	891	0
Proceeds from issuance of common stock	0	159,447	0
Proceeds of registered direct offering	0	17,500	0
Payments of stock issuance costs		(1,535)	0
Proceeds from royalty interest purchase agreement with Oberland Capital Management	0	0	65,000
Payment of transaction costs on royalty interest purchase agreement	0	0	(584)
Proceeds from issuance of common stock under the Company’s stock-based compensation plans	300	785	68
Payment of liability of future royalties, net of imputed interest	(4,472)	(4,287)	(2,226)
Payment on termination of credit agreement with HealthCare Royalty Partners, III, L.P.	0	0	(37,162)
Payments made on Curis Royalty’s debt	0	0	(1,825)
Net cash provided by financing activities	(4,172)	188,814	23,271
Net (decrease) increase in cash and cash equivalents and restricted cash	(89,686)	114,027	(7,390)
Cash and cash equivalents and restricted cash, beginning of period	130,426	16,399	23,789
Cash and cash equivalents and restricted cash, end of period	40,740	130,426	16,399
Supplemental cash flow data:
Issuance costs in accounts payable	0	416	0
Non-cash commitment shares issued to Aspire Capital	0	900	0
Cash paid for interest	4,437	5,050	4,716
Right-of-use assets obtained in exchange for lease liabilities	0	7,169	0
Aspire Capital Fund, LLC
Cash flows from financing activities:
Proceeds from issuance of common stock	0	8,099	0
Demand Sales Agreement
Cash flows from financing activities:
Proceeds from issuance of common stock	0	8,176	0
Payments of stock issuance costs	$ 0	$ (262)	$ 0