CONDENSED STATEMENTS OF CASH FLOWS (Unaudited) (USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Cash flows from operating activities:
Net income (loss)	$ (17,524,550)	$ 4,664,518
Adjustments to reconcile net income (loss) to net cash used in operating activities:
Depreciation and amortization	88,490	32,659
Stock-based compensation expense	1,384,893	1,750,222
Fair value adjustment on warrant liability	1,871,294	(14,702,904)
Net foreign exchange gain (loss)	(47)	177
Changes in assets and liabilities:
Receivables	(3,133,834)	85,760
Interest receivable	28,373	(19,311)
Prepaid expenses and other current assets	2,323,729	621,839
Accounts payable	(2,025,513)	410,109
Accrued expenses and other current liabilities	4,360,417	244,378
Net cash used in operating activities	(12,626,748)	(6,912,553)
Cash flows from investing activities:
Purchase of short-term investments	(15,000,000)	(23,500,000)
Proceeds from the sale of short-term investments	23,520,087	0
Purchases of equipment and furnishings	(59,701)	(6,623)
Net cash provided by (used in) investing activities	8,460,386	(23,506,623)
Cash flows from financing activities:
Net proceeds from public offering	0	80,535,401
Proceeds from issuance of restricted stock to employee	0	100
Net proceeds from exercise of warrants and stock options	0	428,891
Net cash provided by financing activities	0	80,964,392
Net increase (decrease) in cash and cash equivalents	(4,166,362)	50,545,216
Cash and cash equivalents at beginning of period	32,218,905	11,483,112
Cash and cash equivalents at end of period	28,052,543	62,028,328
Supplemental disclosure of cash flow information:
Equipment and furnishings purchased on credit	7,221	7,542
Cashless warrant exercises	0	133
Cash paid for income taxes	$ 800	$ 3,151