Condensed Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021
OPERATING ACTIVITIES:
Net loss	$ (68,079)	$ (78,425)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	7,164	8,328
Issuance of options in-lieu of bonus	441
Amortization of insurance premium	2,806	3,163
Amortization of operating lease right-of-use assets	328	308
Amortization of leasehold improvements	1	1
Change in operating lease liability	(327)	(299)
Change in fair value of warrant liability	4,321
Changes in operating assets and liabilities:
Financed insurance premium	(3,105)	(4,434)
Prepaid expenses	(262)	(1,107)
Accounts payable	(2,488)	8,530
Accrued expenses and other current liabilities	(3,000)	149
Net cash used in operating activities	(62,200)	(63,786)
INVESTING ACTIVITIES:
Purchase of available-for-sale securities	(36,911)	(109,119)
Proceeds from sale of available-for-sale securities		5,539
Proceeds from maturities of available-for-sale securities	56,986	104,206
Net cash provided by investing activities	20,075	626
FINANCING ACTIVITIES:
Proceeds from June Offering issuance of shares and pre-funded warrants	27,811
Proceeds from February Offering, net of cash issuance costs of $165		74,420
Proceeds from financed insurance premium	3,105	4,434
Repayments of short-term borrowings	(2,340)	(3,534)
Exercise of stock options for common stock under Equity Incentive Plan	49	512
Exercise of Warrants		69
Net cash provided by financing activities	28,625	75,901
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	(13,500)	12,741
Cash and cash equivalents at beginning of period	53,888	57,466
Cash and cash equivalents at end of period	40,388	70,207
SUPPLEMENTAL DISCLOSURE OF CASH FLOW INFORMATION:
Initial measurement of warrant liability	21,835
Conversion of warrant liability to equity for warrant exercises	1,417
Unrealized gain (loss) on marketable securities	130	$ (142)
Offering costs still in accrued expense	$ 8