Condensed Consolidated Balance Sheets - USD ($)	Sep. 30, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 4,802,806	$ 3,210,749
Restricted cash	5,000,000	0
Marketable investment securities	12,077,016	18,257,321
Accrued interest income	29,892	23,067
Litigation insurance recovery	0	3,319,927
Prepaid and other current assets	728,482	408,227
Total current assets	22,638,196	25,219,291
Property and equipment, net of accumulated depreciation of $1,120,256 and $1,121,080, respectively	23,442	75,070
Other assets	23,753	30,753
Total assets	22,685,391	25,325,114
Current liabilities:
Accounts payable	239,922	598,070
Litigation settlement payable	0	4,250,000
Accrued expenses	488,632	1,497,056
Debt - current portion	2,341,054	0
Total current liabilities	3,069,608	6,345,126
Debt - non-current portion	7,853,844	0
Total liabilities	10,923,452	6,345,126
Commitments and contingencies (notes 5 and 10)
Stockholders' equity:
Preferred stock, par value $0.0001 per share, 10,000,000 shares authorized; zero issued and outstanding	0	0
Common stock, par value $0.0001 per share, 100,000,000 shares authorized; 21,340,017 and 21,270,249 issued and 21,334,307 and 21,264,539 outstanding	2,134	2,127
Additional paid-in capital	146,638,736	145,423,012
Treasury stock at cost, 5,710 shares	(40,712)	(40,712)
Accumulated other comprehensive loss	(3,853)	(4,616)
Accumulated deficit	(134,834,366)	(126,399,823)
Total stockholders' equity	11,761,939	18,979,988
Total liabilities and stockholders' equity	$ 22,685,391	$ 25,325,114