Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 66,579	$ 116,049
Short term investments	176,221	137,567
Prepaid expenses and other current assets	6,574	5,774
Accounts receivable	2,604	9,387
Total current assets	251,978	268,777
Property and equipment, net	13,580	13,897
Operating lease assets	8,386	9,041
Restricted investments	1,400	1,400
Long term investments	29,749	49,825
Other non-current assets	602
Total assets	305,695	342,940
Current liabilities:
Accounts payable	4,879	4,018
Accrued expenses and other current liabilities	13,153	14,226
Operating lease liabilities	5,250	5,115
Short term portion of note payable, net of discount	3,339	454
Deferred revenue - related party	21,242	22,602
Total current liabilities	47,863	46,415
Long term portion of note payable, net of discount	21,872	24,639
Operating lease liabilities, net of current portion	9,194	10,561
Deferred revenue, net of current portion - related party	82,284	85,572
Other long-term liabilities	777	1,003
Total liabilities	161,990	168,190
Commitments and contingencies (Note 10)
Stockholders’ deficit:
Preferred stock, $0.001 par value; 10,000,000 shares authorized at March 31, 2021 and December 31, 2020; no shares issued and outstanding at March 31, 2021 and December 31, 2020
Common stock, $0.001 par value; 200,000,000 shares authorized at March 31, 2021 and December 31, 2020; 91,588,264 and 91,459,239 shares issued and outstanding at March 31, 2021 and December 31, 2020, respectively	92	91
Additional paid-in capital	727,869	723,482
Accumulated other comprehensive (loss)	(15)	(47)
Accumulated deficit	(584,241)	(548,776)
Total stockholders’ equity	143,705	174,750
Total liabilities and stockholders’ equity	$ 305,695	$ 342,940