CONDENSED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($)	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Cash flows from operating activities:
Net loss	$ (12,643,112)	$ (17,524,550)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	102,434	88,490
Stock-based compensation expense	1,325,817	1,384,893
Fair value adjustment on warrant liability	184,272	1,871,294
Amortization of loan cost and discount	67,150	0
Net foreign exchange gain	0	(47)
Loss on retirement of fixed assets	387	0
Non-cash litigation settlement due in common stock	700,000	0
Changes in assets and liabilities:
Receivables	3,592,636	(3,133,834)
Interest receivable	28,130	28,373
Prepaid expenses and other current assets	(861,255)	2,323,729
Accounts payable	(2,172,100)	(2,025,513)
Accrued expenses and other current liabilities	(3,415,368)	4,360,417
Net cash used in operating activities	(13,091,009)	(12,626,748)
Cash flows from investing activities:
Purchase of short-term investments	0	(15,000,000)
Proceeds from the sale of short-term investments	35,035,420	23,520,087
Purchases of equipment and furnishings	(238,107)	(59,701)
Net cash provided by investing activities	34,797,313	8,460,386
Cash flows from financing activities:
Proceeds from term loan, net of costs	24,012,078	0
Net proceeds from exercise of stock options	183,000	0
Net cash provided by financing activities	24,195,078	0
Net increase (decrease) in cash and cash equivalents	45,901,382	(4,166,362)
Cash and cash equivalents at beginning of period	22,261,372	32,218,905
Cash and cash equivalents at end of period	68,162,754	28,052,543
Supplemental disclosure of cash flow information:
Cash paid during the period for interest	145,139	0
Cash paid for income taxes	0	800
Supplemental disclosure of non-cash investing activities:
Warrants issued in connection with term loan	633,749	0
Equipment and furnishings purchased on credit	$ 73,474	$ 7,221