CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Cash flows from operating activities:
Net loss	$ (13,484)	$ (16,723)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	81	118
Stock-based compensation	1,026	1,252
Change in fair value of common stock warrant liability	(600)	768
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(478)	(228)
Accounts payable, accrued research and development, accrued expenses and other liabilities	(5,388)	1,333
Net cash used in operating activities	(18,843)	(13,480)
Cash flows from financing activities:
Proceeds received from exercise of warrants	0	3,057
Payment of expenses related to the ATM sale agreement	0	(177)
Net cash provided by financing activities	0	57,576
Net change in cash, cash equivalents and restricted cash	(18,843)	44,096
Cash, cash equivalents and restricted cash at beginning of period	47,960	10,277
Cash, cash equivalents and restricted cash at end of period	29,117	54,373
Public Offering
Cash flows from financing activities:
Net proceeds from sale of stock	0	26,494
Direct Offering
Cash flows from financing activities:
Net proceeds from sale of stock	$ 0	$ 28,202