Statements of Cash Flows - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss	$ (8,397,063)	$ (5,091,121)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation	868,415	858,096
Amortization of debt discount - non-cash interest expense	3,869	5,196
Net amortization of premium on debt securities available for sale	9,822	79,775
Depreciation	11,406	9,660
Change in assets and liabilities:
Prepaid expenses and other current assets	(647,931)	(42,001)
Accounts payable	617,926	419,481
Accrued expenses	(421,037)	(425,929)
Net cash used in operating activities	(7,954,593)	(4,186,843)
CASH FLOWS FROM INVESTING ACTIVITIES:
Acquisitions of property and equipment	(139,006)	(11,592)
Purchases of marketable securities	(4,009,513)	(3,151,867)
Sales of marketable securities	8,950,000	4,055,000
Net cash provided by investing activities	4,801,481	891,541
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from issuance of common stock, net of issuance costs	4,093,316	10,583,091
Net cash provided by financing activities	4,093,316	10,583,091
NET CHANGE IN CASH AND CASH EQUIVALENTS	940,204	7,287,789
CASH AND CASH EQUIVALENTS, BEGINNING OF PERIOD	20,023,337	12,015,061
CASH AND CASH EQUIVALENTS, END OF PERIOD	20,963,541	19,302,850
Cash paid during the period for:
Interest	$ 22,682	$ 20,162