Condensed Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021
OPERATING ACTIVITIES:
Net loss	$ (48,978)	$ (50,007)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	4,308	5,683
Issuance of options in-lieu of bonus	441
Amortization of insurance premium	2,024	2,046
Amortization of operating lease right-of-use assets	217	204
Amortization of leasehold improvements	1
Change in operating lease liability	(216)	(198)
Change in fair value of warrant liability	4,357
Changes in operating assets and liabilities:
Financed insurance premium	(3,105)	(4,434)
Prepaid expenses	(524)	(1,482)
Accounts payable	(770)	2,670
Accrued expenses and other current liabilities	(565)	(2,603)
Net cash used in operating activities	(42,810)	(48,121)
INVESTING ACTIVITIES:
Purchase of available-for-sale securities	(14,987)	(94,546)
Proceeds from sale of available-for-sale securities		500
Proceeds from maturities of available-for-sale securities	30,041	86,154
Net cash provided by/(used in) investing activities	15,054	(7,892)
FINANCING ACTIVITIES:
Proceeds from June Offering issuance of shares and pre-funded warrants	27,899
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	(1,408)	(2,350)
Exercise of stock options for common stock under Equity Incentive Plan		408
Exercise of Warrants		69
Net cash (used in)/provided by financing activities	29,596	76,981
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	1,840	20,968
Cash and cash equivalents at beginning of period	53,888	57,466
Cash and cash equivalents at end of period	55,728	78,434
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	113	(73)
Offering costs still in accrued expense	$ 96	$ 38