CONDENSED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Operating activities
Net loss	$ (27,749)	$ (23,301)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	5,704	4,132
Depreciation and amortization	63	63
Amortization expense component of lease expense	344	316
Amortization of available-for-sale marketable securities, net	292	194
Realized gain on sale of available-for-sale marketable securities		(39)
Realized gain on sale of property and equipment		(70)
Changes in operating assets and liabilities:
Accounts receivable - related party	(2,496)
Inventory, net	677
Other receivables	17	(1,687)
Prepaid expenses	(2,594)	(942)
Accounts payable and accrued expenses	640	(2,001)
Operating lease liabilities	(423)	(386)
Net cash used in operating activities	(25,525)	(23,721)
Investing activities
Proceeds from maturities of available-for-sale marketable securities	44,000	27,655
Proceeds from redemptions of available-for-sale marketable securities, at par		2,100
Proceeds from sale of available-for-sale marketable securities	0	8,029
Purchases of available-for-sale marketable securities	(10,526)	(23,985)
Purchases of property and equipment	(43)
Proceeds from sale of property and equipment		70
Net cash provided by investing activities	33,431	13,869
Financing activities
Proceeds from the exercise of stock options	3	688
Net cash provided by financing activities	3	688
Net increase (decrease) in cash, cash equivalents and restricted cash	7,909	(9,164)
Cash, cash equivalents and restricted cash at beginning of period	13,861	32,091
Cash, cash equivalents and restricted cash at end of period	$ 21,770	$ 22,927