Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 54,857	$ 65,126
Investments	20,237	29,690
Prepaid expenses and other current assets	3,385	3,588
Accounts receivable	2,084	1,785
Total current assets	80,563	100,189
Property and equipment, net	17,836	19,495
Operating lease assets	10,820	11,356
Restricted investments	1,400	1,400
Total assets	110,619	132,440
Current liabilities:
Accounts payable	5,521	4,859
Accrued expenses and other current liabilities	9,141	10,884
Operating lease liabilities	4,623	4,456
Deferred revenue - related party	19,974	20,960
Deferred revenue	4,855	4,834
Total current liabilities	44,114	45,993
Note payable, net of discount	24,754	24,648
Operating lease liabilities, net of current portion	14,444	15,676
Deferred revenue, net of current portion - related party	84,635	89,111
Deferred revenue, net of current portion	3,641	4,834
Other long-term liabilities	680	502
Total liabilities	172,268	180,764
Commitments and contingencies (Note 11)
Stockholders’ deficit:
Preferred stock, $0.001 par value; 10,000,000 shares authorized at March 31, 2020 and December 31, 2019; no shares issued and outstanding at March 31, 2020 and December 31, 2019.
Common stock, $0.001 par value; 200,000,000 shares authorized at March 31, 2020 and December 31, 2019; 71,671,067 and 70,143,252 shares issued and outstanding at March 31, 2020 and December 31, 2019, respectively	72	70
Additional paid-in capital	417,819	411,255
Accumulated other comprehensive income (loss)	(10)
Accumulated deficit	(479,530)	(459,649)
Total stockholders’ deficit	(61,649)	(48,324)
Total liabilities and stockholders’ deficit	$ 110,619	$ 132,440