CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 130,272	$ 88,915
Prepaid expenses and other current assets	4,405	4,843
Total current assets	134,677	93,758
Property and equipment, net	30,885	31,410
Restricted cash, net of current portion	4,170	4,170
Operating right-of-use assets	21,767	22,003
Total assets	191,499	151,341
Current liabilities:
Accounts payable	2,162	2,018
Accrued expenses	6,805	8,870
Deferred revenue	4,345	5,281
Operating lease liabilities	2,230	1,482
Total current liabilities	15,542	17,651
Long-term liabilities:
Deferred revenue, net of current portion	46,008	57,416
Note payable, net of discount	25,095	24,960
Operating lease liabilities, net of current portion	35,931	36,540
Other long-term liabilities	207	207
Total liabilities	122,783	136,774
Commitments and contingencies (Note 8)
Stockholders’ equity:
Common stock, $0.0001 par value; 150,000,000 shares authorized as of March 31, 2021 and December 31, 2020; 21,996,886 and 18,787,579 shares issued and outstanding as of March 31, 2021 and December 31, 2020, respectively	2	2
Additional paid-in capital	367,112	302,655
Accumulated deficit	(298,398)	(288,090)
Total stockholders’ equity	68,716	14,567
Total liabilities and stockholders’ equity	$ 191,499	$ 151,341