BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 18,890	$ 30,373
Short-term investments	106,077	26,954
Accounts receivable, net	15,472	15,973
Inventories	6,616	1,638
Prepaid and other current assets	7,412	14,045
Total current assets	154,467	88,983
Property and equipment, net	2,184	2,676
Operating lease right-of-use asset	9,703	17,895
Other assets	974	824
Total assets	167,328	110,378
Current liabilities:
Accounts payable	3,795	3,707
Accrued compensation	10,690	9,592
Accrued research and development	10,384	4,889
Other accrued liabilities	12,691	11,014
Lease liabilities, current portion	9,892	8,621
Deferred revenue	2,596	3,018
Other long-term liabilities, current portion	13,506
Total current liabilities	63,554	40,841
Long-term portion of lease liabilities	759	10,651
Loans payable, net of discount	19,914	19,815
Other long-term liabilities	52,727	5,045
Commitments
Stockholders' equity:
Preferred stock, $0.001 par value; 10,000,000 shares authorized; none issued and outstanding as of December 31, 2021 and 2020
Common stock, $0.001 par value; 400,000,000 shares authorized; 171,602,226 and 169,316,782 shares issued and outstanding as of December 31, 2021 and 2020, respectively	172	169
Additional paid-in capital	1,354,190	1,339,833
Accumulated other comprehensive income (loss)	(102)	(4)
Accumulated deficit	(1,323,886)	(1,305,972)
Total stockholders' equity	30,374	34,026
Total liabilities and stockholders' equity	$ 167,328	$ 110,378