CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 78,823	$ 70,154
Marketable securities		21,980
Restricted cash	2,947	10,847
Accounts receivable	7,500
Prepaid expenses and other current assets	7,977	16,295
Total current assets	97,247	119,276
Restricted cash	410	958
Property and equipment, net	11,445	28,426
Intangible assets, net	5,581	6,541
Goodwill	51,154	51,967
Other non-current assets	7,120	810
Total assets	172,957	207,978
Current liabilities:
Accounts payable	2,910	9,301
Accrued expenses	14,867	19,550
Accrued interest	5,078	5,078
Deferred revenue	1,678	10,010
Other current liabilities	1,262	1,600
Total current liabilities	25,795	45,539
Deferred revenue	2,500	2,500
Convertible notes payable	320,611	319,187
Other non-current liabilities	10,068	8,687
Total liabilities	358,974	375,913
Commitments and contingencies
Stockholders' deficit:
Preferred stock, $0.01 par value, 2,000,000 shares authorized; no shares issued and outstanding at December 31, 2019 and 2018	0	0
Common stock, $0.01 par value, 600,000,000 shares authorized at December 31, 2019 and 2018 ; and 32,399,352 shares issued and 32,352,416 shares outstanding at December 31, 2019 and 19,245,302 shares issued and 19,222,410 shares outstanding at December 31, 2018	324	192
Additional paid-in capital	1,260,551	1,144,621
Accumulated deficit	(1,431,801)	(1,299,107)
Treasury stock, 46,936 shares, cost basis at December 31, 2019 and 22,892 shares, cost basis at December 31, 2018	(2,583)	(2,450)
Accumulated other comprehensive loss	(12,508)	(11,191)
Total stockholders' deficit	(186,017)	(167,935)
Total liabilities and stockholders' deficit	$ 172,957	$ 207,978