Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 138,717	$ 160,754
Marketable securities	447,325	380,560
Collaboration receivable – related party	4,842	4,886
Tenant improvement and other receivables	779	3,428
Prepaid expenses and other current assets	13,018	10,264
Total current assets	604,681	559,892
Marketable securities	129,899	32,250
Property and equipment, net	24,771	25,337
Other non-current assets	1,249	1,615
Total assets	760,600	619,094
Current liabilities:
Accounts payable	23,409	17,106
Accrued expenses	29,641	32,002
Deferred revenue – related party	37,069	35,913
Deferred rent	3,529	3,412
Total current liabilities	93,648	88,433
Deferred revenue, net of current portion – related party	141,957	154,297
Deferred rent, net of current portion	16,003	17,773
Total liabilities	251,608	260,503
Stockholders’ equity:
Preferred stock, $0.001 par value; 25,000,000 shares authorized; no shares issued or outstanding at June 30, 2017 and December 31, 2016	0	0
Common stock, $0.001 par value; 125,000,000 shares authorized; 48,346,297 and 42,220,444 shares issued and outstanding at June 30, 2017 and December 31, 2016, respectively	48	42
Additional paid-in capital	1,142,233	842,013
Accumulated other comprehensive loss	(650)	(313)
Accumulated deficit	(632,639)	(483,151)
Total stockholders’ equity	508,992	358,591
Total liabilities and stockholders’ equity	$ 760,600	$ 619,094