Condensed Statements of Cash Flows - USD ($)	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014
Operating activities
Net loss	$ (6,761,911)	$ (6,502,524)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	756,138	488,520
Non-cash interest	30,348	48,170
Deferred rent expense	(6,374)	10,059
Change in operating assets and liabilities:
Prepaid expenses and other assets	214,845	(107,133)
Accounts payable and accrued expenses	227,700	994,701
Net cash used in operating activities	(5,539,254)	(5,068,207)
Financing activities
Payment on bank line of credit		(3,000,000)
Costs paid in connection with loan origination		(82,685)
Proceeds from issuance of common stock, net	1,266,533
Net cash provided by (used in) financing activities	1,266,533	(3,082,685)
Net decrease in cash and cash equivalents	(4,272,721)	(8,150,892)
Cash and cash equivalents at beginning of period	14,155,809	24,196,691
Cash and cash equivalents at end of period	9,883,088	16,045,799
Supplemental disclosure of cash flow information
Interest paid	$ 104,500	$ 58,790