Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 91,028	$ 43,695
Restricted cash, current	2,788	0
Investment securities, available for sale	0	49,304
Accounts receivable, interest and other receivables	303	909
Prepaid expenses and other current assets	884	1,387
Assets held for sale	16,851	0
Total current assets	111,854	95,295
Operating lease right-of-use assets	1,042	0
Property and equipment, net	2,529	20,878
Restricted cash, noncurrent	0	4,973
Other assets	825	355
Total assets	116,250	121,501
Current liabilities:
Accounts payable	2,643	3,774
Accrued expenses and other current liabilities	9,770	8,589
Warrant derivative liability	52,184	0
Private placement option liability	12,094	0
Current portion of long-term debt	11,000	0
Current portion of lease liabilities	454	40
Current portion of deferred revenue	0	2,983
Current portion of deferred rent		418
Liabilities held for sale	6,273	0
Total current liabilities	94,418	15,804
Long-term liabilities:
Long-term debt, net of deferred issuance costs	25,717	35,832
Long-term lease liabilities	864	91
Deferred rent		1,296
Total liabilities	120,999	53,023
Commitments and contingencies
Series 1 redeemable convertible preferred stock, $0.01 par value, 1,517,500 shares authorized and 538,000 shares issued and outstanding at December 31, 2019	21,468	0
Stockholders’ (deficit) equity:
Common stock, $0.01 par value; 40,000,000 shares authorized at December 31, 2019 and December 31, 2018, respectively; 5,076,593 shares issued and 5,008,846 shares outstanding at December 31, 2019; 4,424,205 shares issued and 4,356,459 shares outstanding at December 31, 2018	507	442
Treasury stock: 67,746 shares held at December 31, 2019 and December 31, 2018	(5,056)	(5,056)
Additional paid-in capital	511,684	493,784
Accumulated other comprehensive loss	(327)	(144)
Accumulated deficit	(533,025)	(420,548)
Total stockholders’ (deficit) equity	(26,217)	68,478
Total liabilities, preferred stock and stockholders' (deficit) equity	$ 116,250	$ 121,501