Statements of Cash Flows - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Operating activities
Net loss	$ (12,121,463)	$ (13,247,681)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	1,504,356	1,102,087
Non-cash interest	55,883	59,982
Deferred rent expense	(12,313)	5,483
Change in operating assets and liabilities:
Prepaid expenses and other assets	98,185	(287,503)
Accounts payable and accrued expenses	(20,486)	866,560
Net cash used in operating activities	(10,495,838)	(11,501,072)
Financing activities
Proceeds from bank line of credit		4,500,000
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	5,031,184	42,875
Net cash provided by financing activities	5,031,184	1,460,190
Net increase (decrease) in cash and cash equivalents	(5,464,654)	(10,040,882)
Cash and cash equivalents at beginning of period	14,155,809	24,196,691
Cash and cash equivalents at end of period	8,691,155	14,155,809
Supplemental disclosure of cash flow information
Cash paid for interest	230,313	$ 58,790
Non-cash financing activities
Deferred financing costs paid in prior year	$ 137,812