Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Current assets:
Cash and cash equivalents	$ 130,552	$ 232,694
Investments	216,041	156,046
Prepaid expenses and other current assets	7,255	3,319
Total current assets	353,848	392,059
Property and equipment, net	24,354	22,299
Goodwill	30,815	30,815
Restricted cash	1,343	1,343
Deposits	455	455
Operating lease right-of-use assets	1,390	1,569
Finance lease right-of-use asset	47,945	48,480
Total assets	460,150	497,020
Current liabilities:
Accounts payable and accrued expenses	20,031	19,615
Operating lease liabilities, current	838	863
Finance lease liability, current	1,701	1,689
Total current liabilities	22,570	22,167
Operating lease liabilities, non-current	719	905
Finance lease liability, non-current	19,176	19,144
Other liabilities	65	80
Total liabilities	42,530	42,296
Commitments and contingencies (Note 10)
Stockholders' equity:
Common stock, $0.01 par value, 120,000,000 shares authorized; 64,522,057 and 64,505,889 shares issued and outstanding at March 31, 2022 and December 31, 2021, respectively	645	645
Additional paid-in capital	952,498	946,152
Accumulated other comprehensive loss	(629)	(161)
Accumulated deficit	(534,894)	(491,912)
Total stockholders' equity	417,620	454,724
Total liabilities and stockholders' equity	460,150	497,020
Series A Convertible Preferred Shares [Member]
Stockholders' equity:
Preferred stock	0	0
Series B Convertible Preferred Shares [Member]
Stockholders' equity:
Preferred stock	$ 0	$ 0