Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 61,536	$ 65,126
Investments	2,404	29,690
Prepaid expenses and other current assets	5,847	3,588
Accounts receivable	2,929	1,785
Total current assets	72,716	100,189
Property and equipment, net	16,305	19,495
Operating lease assets	10,257	11,356
Restricted investments	1,400	1,400
Total assets	100,678	132,440
Current liabilities:
Accounts payable	4,163	4,859
Accrued expenses and other current liabilities	10,604	10,884
Operating lease liabilities	4,788	4,456
Deferred revenue - related party	19,040	20,960
Deferred revenue	5,653	4,834
Total current liabilities	44,248	45,993
Note payable, net of discount	24,863	24,648
Operating lease liabilities, net of current portion	13,181	15,676
Deferred revenue, net of current portion - related party	80,383	89,111
Deferred revenue, net of current portion	2,826	4,834
Other long-term liabilities	752	502
Total liabilities	166,253	180,764
Commitments and contingencies (Note 11)
Stockholders’ deficit:
Preferred stock, $0.001 par value; 10,000,000 shares authorized at June 30, 2020 and December 31, 2019; no shares issued and outstanding at June 30, 2020 and December 31, 2019
Common stock, $0.001 par value; 200,000,000 shares authorized at June 30, 2020 and December 31, 2019; 75,131,834 and 70,143,252 shares issued and outstanding at June 30, 2020 and December 31, 2019, respectively	75	70
Additional paid-in capital	434,593	411,255
Accumulated other comprehensive income	1
Accumulated deficit	(500,244)	(459,649)
Total stockholders’ deficit	(65,575)	(48,324)
Total liabilities and stockholders’ deficit	$ 100,678	$ 132,440