CONDENSED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($)	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Cash flows from operating activities:
Net loss	$ (11,044,104)	$ (12,643,112)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	173,524	102,434
Stock-based compensation expense	931,525	1,325,817
Fair value adjustment on warrant liabilities	32,119	184,272
Amortization of loan cost and discount	715,786	67,150
Loss on retirement of fixed assets	0	387
Non-cash litigation settlement due in common stock	0	700,000
Changes in assets and liabilities:
Receivables	81,574	3,592,636
Interest receivable	0	28,130
Prepaid expenses and other current assets	789,203	(861,255)
Accounts payable	121,126	(2,172,100)
Accrued expenses and other current liabilities	(39,707)	(3,415,368)
Net cash used in operating activities	(8,238,954)	(13,091,009)
Cash flows from investing activities:
Proceeds from the sale of short-term investments	0	35,035,420
Purchases of equipment and furnishings	(103,051)	(238,107)
Net cash (used) provided by investing activities	(103,051)	34,797,313
Cash flows from financing activities:
Proceeds from term loan, net of costs	0	24,012,078
Payment of principal on term loan	(614,165)	0
Net proceeds from exercise of stock options	0	183,000
Net cash (used) provided by financing activities	(614,165)	24,195,078
Net increase (decrease) in cash and cash equivalents	(8,956,170)	45,901,382
Cash and cash equivalents at beginning of period	56,959,485	22,261,372
Cash and cash equivalents at end of period	48,003,315	68,162,754
Supplemental disclosure of cash flow information:
Cash paid during the period for interest	609,944	145,139
Supplemental disclosure of non-cash investing activities:
Preferred stock conversion	7,400	0
Warrants issued in connection with term loan	0	633,749
Equipment and furnishings purchased on credit	$ 14,710	$ 73,474