Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 85,126	$ 64,418
Marketable securities	71,390	159,455
Accounts receivable, net of allowance for credit losses of $43 and $43, respectively	441	441
Other receivables	6,294	9,558
Prepaid expenses and other current assets	11,789	10,148
Total current assets	175,040	244,020
Property and equipment, net	12,547	11,607
Facility and equipment under lease	3,068	3,806
Other assets	3,598	4,000
Total assets	194,253	263,433
Current liabilities:
Accounts payable and other accrued liabilities	49,684	54,284
Accrued payroll and benefits	5,874	7,686
Total current liabilities	55,558	61,970
Other long-term liabilities	8,098	11,070
Total liabilities	63,656	73,040
Commitments and contingencies (Note 8)
Stockholders’ equity:
Preferred stock, $0.001 par value; 5,000,000 shares authorized; no shares issued and outstanding	0	0
Common stock, $0.001 par value; 300,000,000 shares authorized; 117,823,973 and 113,299,612 issued and outstanding at June 30, 2020 and December 31, 2019, respectively	118	113
Additional paid-in capital	930,817	918,205
Accumulated other comprehensive loss	(3,254)	(3,498)
Accumulated deficit	(797,084)	(724,427)
Total stockholders’ equity	130,597	190,393
Total liabilities and stockholders’ equity	$ 194,253	$ 263,433