Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Current assets:
Cash and cash equivalents	$ 31,119	$ 24,064
Short-term investments	225,326	270,357
Accounts receivable, net	7,534	8,881
Inventories, net	12,498	9,299
Prepaid and other current assets	13,090	14,822
Total current assets	289,567	327,423
Property, plant and equipment, net	14,572	14,710
Goodwill	1,189	1,189
Intangible assets, net	586	724
Contract assets	9,182	12,962
Other assets	17,754	18,413
Total assets	332,850	375,421
Current liabilities:
Accounts payable	7,130	5,105
Accrued expense and other current liabilities	32,564	35,651
Contract liabilities	5,656	6,348
Total current liabilities	45,350	47,104
Long-term tax liabilities	445	443
Other long-term liabilities	27,401	28,611
Total liabilities	73,196	76,158
Commitments and contingencies
Stockholders’ equity:
Preferred stock	0	0
Common stock	20	20
Additional paid-in capital	836,229	825,988
Accumulated other comprehensive loss	(1,141)	(412)
Accumulated deficit	(575,454)	(526,333)
Total stockholders’ equity	259,654	299,263
Total liabilities and stockholders’ equity	$ 332,850	$ 375,421