Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 71,435	$ 190,514
Accounts receivable		500
Short-term investments and related maturity receivables	90,573	10,493
Prepaid expenses and other current assets	3,170	3,689
Total current assets	165,178	205,196
Property and equipment, net	9,225	5,125
Operating lease right-of-use assets	23,560
Restricted cash	227	227
Collaboration contract asset	1,687	1,958
Other assets		526
Total assets	199,877	213,032
Current liabilities:
Accounts payable	5,410	4,205
Accrued expenses	9,834	10,926
CIRM award liability, current portion	2,106	2,106
Deferred revenue, current portion	5,049	7,588
Operating lease liabilities, current portion	1,572
Long-term debt, current portion	5,447	2,438
Total current liabilities	29,418	27,263
Deferred rent		3,401
Accrued expenses	718	549
Deferred revenue, net of current portion	5,244	7,500
CIRM award liability, net of current portion	1,404	1,404
Operating lease liabilities, net of current portion	26,098
Long-term debt, net of current portion	9,469	12,446
Commitments and contingencies
Stockholders’ equity:
Preferred stock, $0.001 par value; authorized shares—5,000,000 at June 30, 2019 and December 31, 2018; 2,819,549 Class A Convertible Preferred shares issued and outstanding at June 30, 2019 and December 31, 2018	3	3
Common stock, $0.001 par value; authorized shares—150,000,000 at June 30, 2019 and December 31, 2018; issued and outstanding—65,309,891 at June 30, 2019 and 64,693,681 at December 31, 2018	65	65
Additional paid-in capital	455,999	445,799
Accumulated other comprehensive gain (loss)	93	(2)
Accumulated deficit	(328,634)	(285,396)
Total stockholders’ equity	127,526	160,469
Total liabilities and stockholders’ equity	$ 199,877	$ 213,032