Statements of Cash Flows (Unaudited) - USD ($)	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Cash flows from operating activities
Net loss	$ (10,393,534)	$ (7,279,781)
Adjustments to reconcile net loss to net cash used in operating activities
Amortization of debt discount on notes payable	767,883	925,634
Amortization of investment premiums	49,282	85,011
Amortization of financing costs	519,960
Amortization of non-cash clinical trial costs	399,587
Change in fair value of debt conversion feature liability	(848,374)	(508,597)
Stock-based compensation	743,497	1,114,799
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	53,827	(16,098)
Accounts payable	57,153	402,448
Accrued expenses	1,168,957	(675,380)
Net cash used in operating activities	(7,481,762)	(5,951,964)
Cash flows from investing activities
Purchases of investments	(10,426,060)	(10,246,479)
Proceeds from sales and maturities of investments	11,700,000	11,388,000
Net cash provided by investing activities	1,273,940	1,141,521
Cash flows from financing activities
Proceeds from issuances of common stock, net of underwriting discounts and commissions	6,582,278	9,918,750
Public offering and financing costs	(62,045)	(609,250)
Repayment of convertible notes payable		(94,861)
Value of shares withheld related to employee tax withholding	(13,871)	(23,759)
Proceeds from stock issuance under employee stock purchase plan	19,609	10,943
Net cash provided by financing activities	6,525,971	9,201,823
Net increase in cash and cash equivalents	318,149	4,391,380
Cash and cash equivalents beginning of period	3,075,502	768,550
Cash and cash equivalents end of period	3,393,651	5,159,930
Supplemental disclosure of cash flow information:
Cash paid during the period for interest		205,139
Supplemental disclosure of non-cash investing and financing transactions
Shares issued to cover future clinical trial costs	1,800,000
Unpaid deferred public offering and other financing costs	$ 147,804	381,991
Shares issued in lieu of loan payment to related party		$ 1,200,000