BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 6,316	$ 9,140
Marketable securities at fair value	0	13,862
Prepaid expenses and other current assets	497	358
Total current assets	6,813	23,360
Restricted cash	455	455
Property and equipment, net	24,636	11,916
Operating lease right-of-use assets	5,763
Other long-term assets	3	49
Total assets	37,670	35,780
Current liabilities:
Accounts payable	4,356	4,450
Accrued compensation	2,015	2,092
Build-to-suit obligation, current portion	4,554	2,326
Operating lease liabilities, current portion	1,140
Other accrued liabilities	4,154	2,414
Finance lease obligation, current portion	18
Finance lease obligation, current portion		5
Total current liabilities	16,237	11,287
Build-to-suit obligation, long-term portion, net of debt issuance costs and discount	6,095	4,478
Operating lease liabilities	5,931
Finance lease obligation, long-term portion	15
Finance lease obligation, long-term portion		18
Deferred rent		1,287
Total liabilities	28,278	17,070
Commitments and contingencies (note 10)
Stockholders’ equity:
Preferred stock, $0.0001 par value, 5,000,000 shares authorized; none issued and outstanding as of December 31, 2019 and 2018	0	0
Common stock, $0.0001 par value; 250,000,000 shares authorized as of December 31, 2019 and 2018, respectively; 23,503,214 and 11,973,039 shares issued and outstanding as of December 31, 2019 and 2018, respectively	2	1
Additional paid-in capital	308,211	279,946
Accumulated deficit	(298,821)	(261,232)
Accumulated other comprehensive loss	0	(5)
Total stockholders’ equity	9,392	18,710
Total liabilities and stockholders’ equity	$ 37,670	$ 35,780