Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 207,326	$ 65,126
Short term investments	90,588	29,690
Prepaid expenses and other current assets	6,703	3,588
Accounts receivable	3,393	1,785
Total current assets	308,010	100,189
Property and equipment, net	14,729	19,495
Operating lease assets	9,664	11,356
Restricted investments	1,400	1,400
Long term investments	22,398
Total assets	356,201	132,440
Current liabilities:
Accounts payable	6,201	4,859
Accrued expenses and other current liabilities	11,318	10,884
Operating lease liabilities	4,950	4,456
Deferred revenue - related party	16,517	20,960
Deferred revenue	6,784	4,834
Total current liabilities	45,770	45,993
Note payable, net of discount	24,977	24,648
Operating lease liabilities, net of current portion	11,894	15,676
Deferred revenue, net of current portion - related party	82,826	89,111
Deferred revenue, net of current portion	1,695	4,834
Other long-term liabilities	987	502
Total liabilities	168,149	180,764
Commitments and contingencies (Note 11)
Stockholders’ deficit:
Preferred stock, $0.001 par value; 10,000,000 shares authorized at September 30, 2020 and December 31, 2019; no shares issued and outstanding at September 30, 2020 and December 31, 2019
Common stock, $0.001 par value; 200,000,000 shares authorized at September 30, 2020 and December 31, 2019; 91,214,536 and 70,143,252 shares issued and outstanding at September 30, 2020 and December 31, 2019, respectively	91	70
Additional paid-in capital	718,483	411,255
Accumulated other comprehensive income	2
Accumulated deficit	(530,524)	(459,649)
Total stockholders’ equity (deficit)	188,052	(48,324)
Total liabilities and stockholders’ equity (deficit)	$ 356,201	$ 132,440