Condensed Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Current assets
Cash and cash equivalents	$ 75,338	$ 16,862
Other current assets	565	698
Total current assets	75,903	17,560
Property and equipment, net	2,245	1,883
Operating lease right-of-use asset	851	946
Restricted cash	435	435
Intangible assets	152	164
Other assets	25	18
Total assets	79,611	21,006
Current liabilities
Accounts payable	698	630
Accrued liabilities	710	495
Contract liabilities	7,286	7,765
Current portion of long-term debt	699	431
Current portion of operating lease liability	680	676
Current portion of finance lease obligations	28	31
Total current liabilities	10,101	10,028
Long-term debt, net of current portion	886	1,151
Operating lease liability, net of current portion	624	774
Finance lease obligations, net of current portion	39	44
Total liabilities	11,650	11,997
Commitments and contingencies (Note 8)
Shareholders' equity
Preferred stock, par value $0.001; 25,000 shares authorized; 0 and 0 shares issued and outstanding	0	0
Common stock, par value $0.001; 210,000 shares authorized; 157,952 and 152,926 shares issued and outstanding at March 31, 2021 and December 31, 2020, respectively	158	153
Additional paid-in capital	660,267	601,224
Subscriptions receivable	0	(6,135)
Accumulated deficit	(592,464)	(586,233)
Total shareholders' equity	67,961	9,009
Total liabilities and shareholders' equity	79,611	21,006
Reconciliation of cash, cash equivalents, and restricted cash balances
Cash and cash equivalents	75,338	16,862
Restricted cash	435	435
Cash, cash equivalents, and restricted cash	$ 75,773	$ 17,297