Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Current assets:
Cash and cash equivalents	$ 46,562	$ 22,221
Short-term debt securities	86,155	66,594
Accounts receivable, net	2,287	2,576
Inventories	1,910	2,612
Prepaid expenses and other current assets	10,442	9,361
Total current assets	147,356	103,364
Long-term debt securities		17,262
Property and equipment, net	545	613
Operating lease right-of-use assets	521	653
Other assets	4,907	4,510
Total assets	153,329	126,402
Current liabilities:
Accounts payable	9,218	7,765
Accrued liabilities	14,255	13,699
Current portion of operating lease liabilities	590	628
Current portion of long-term debt, net	12,549	7,809
Total current liabilities	36,612	29,901
Long-term debt, net	19,446	23,986
Operating lease liabilities	4	116
Total liabilities	56,062	54,003
Stockholders’ equity:
Common stock	41	35
Additional paid-in capital	460,808	412,930
Accumulated other comprehensive loss	(522)	(149)
Accumulated deficit	(363,060)	(340,417)
Total stockholders’ equity	97,267	72,399
Total liabilities and stockholders’ equity	$ 153,329	$ 126,402