Condensed Consolidated Balance Sheets (Unaudited) - USD ($)	Mar. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 9,015,779	$ 21,373,273
Short-term investments	11,036,102
Receivables	158,280	148,527
Prepaid expenses and other current assets	845,950	913,162
Current assets held for sale (Note 5)	402,045	81,182
Total current assets	21,458,156	22,516,144
Equipment and furnishings, net	33,450	44,326
Other assets	15,179	40,642
Non-current assets held for sale		324,853
Total assets	21,506,785	22,925,965
Current liabilities:
Accounts payable	1,308,810	1,234,762
Accrued expenses and other current liabilities	942,025	726,191
Current liabilities for sale (Note 5)	109,137	602,713
Total liabilities	2,359,972	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 March 31, 2019 and December 31, 2018	33,637	33,637
Additional paid-in capital	477,403,249	477,192,747
Accumulated deficit	(458,290,073)	(456,864,085)
Total stockholders' equity	19,146,813	20,362,299
Total liabilities and stockholders' equity	21,506,785	22,925,965
Series A Junior Participating Preferred Stock [Member]
Stockholders' equity:
Preferred stock, value