Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 81,709	$ 70,502
Marketable securities	370,188	514,800
Accounts receivable, net	7,106	5,076
Collaboration receivable – related party	1,838	2,462
Collaboration receivable – other	869	670
Royalty receivable – related party	2,600	2,234
Inventory	5,849	869
Prepaid expenses and other current assets	19,985	17,167
Total current assets	490,144	613,780
Marketable securities	88,579	220,119
Operating lease assets	95,833
Property and equipment, net	24,060	24,320
Other non-current assets	0	238
Total assets	698,616	858,457
Current liabilities:
Accounts payable	21,511	17,880
Accrued expenses	46,750	42,147
Deferred revenue – related party	16,873	32,710
Operating lease liabilities	7,298
Deferred rent	0	766
Total current liabilities	92,432	93,503
Deferred revenue, net of current portion – related party	49,797	59,809
Operating lease liabilities, net of current portion	108,096
Deferred rent, net of current portion	0	17,608
Total liabilities	250,325	170,920
Stockholders’ equity:
Preferred stock, $0.001 par value; 25,000,000 shares authorized; no shares issued or outstanding at September 30, 2019 and December 31, 2018	0	0
Common stock, $0.001 par value; 125,000,000 shares authorized; 58,877,691 and 58,218,653 shares issued and outstanding at September 30, 2019 and December 31, 2018, respectively	59	58
Additional paid-in capital	1,861,523	1,794,283
Accumulated other comprehensive income (loss)	464	(2,171)
Accumulated deficit	(1,413,755)	(1,104,633)
Total stockholders’ equity	448,291	687,537
Total liabilities and stockholders’ equity	$ 698,616	$ 858,457