Condensed Consolidated Balance Sheets - USD ($)	Sep. 30, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 8,491,265	$ 21,373,273
Short-term investments	10,023,850
Receivables	4,789	148,527
Prepaid expenses and other current assets	1,410,277	913,162
Current assets held for sale		81,182
Total current assets	19,930,181	22,516,144
Equipment and furnishings, net	23,071	44,326
Other assets	10,119	40,642
Non-current assets held for sale		324,853
Total assets	19,963,371	22,925,965
Current liabilities:
Accounts payable	2,194,276	1,234,762
Accrued expenses and other current liabilities	936,105	726,191
Current liabilities of discontinued operations	1,272	602,713
Total liabilities	3,131,653	2,563,666
Commitments and contingencies
Stockholders' equity:
Preferred Stock, value
Common stock, $0.001 par value, 41,666,667 shares authorized; 33,637,501 shares issued and outstanding at September 30, 2019 and December 31, 2018	33,637	33,637
Additional paid-in capital	477,834,188	477,192,747
Accumulated deficit	(461,036,107)	(456,864,085)
Total stockholders' equity	16,831,718	20,362,299
Total liabilities and stockholders' equity	19,963,371	22,925,965
Series A Junior Participating Preferred Stock [Member]
Stockholders' equity:
Preferred Stock, value