CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($)	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Operating activities
Net loss	$ (18,045,348)	$ (20,464,796)
Adjustments to reconcile net loss to net cash used in operating activities:
Loss on disposal of assets	28,097	0
Impairment loss	485,000	0
Depreciation and amortization	645,962	489,708
Stock based compensation expense	1,696,184	4,113,021
Loss on extinguishment of debt	1,655,825	0
Accretion of final fee premium	293,614	181,318
Amortization of discount on debt	113,780	52,641
Net realized loss on short-term investments	6,400	0
Amortization of premiums on short-term investments	9,230	27,481
Deferred rent	(136,776)	(66,689)
Interest income accrued on short-term investments	(90,330)	(75,300)
Change in fair value of derivative financial instruments—warrants	(484,078)	(586,626)
Changes in operating assets and liabilities:
Decrease in other assets	0	2,761
Increase in accounts receivable	(56,985)	(59,801)
Decrease (increase) in prepaid expenses	243,571	(88,678)
Increase in accounts payable and accrued expenses	280,520	1,481,532
Net cash used in operating activities	(13,355,334)	(14,993,428)
Investing activities:
Capital expenditures, net	(20,738)	(670,867)
Proceeds from Sale and Maturity of Available-for-sale Securities	16,431,837	0
Payments for (Proceeds from) Short-term Investments	(8,804,604)	(27,951,611)
Proceeds from Sale of Available-for-sale Securities	16,434,553	0
Net cash provided by (used in) investing activities	24,041,048	(28,622,478)
Financing activities:
Proceeds from sales of common stock, net of expenses	106,791	0
Proceeds from exercise of options	0	232,144
Borrowings under equipment line of credit	0	792,251
Payment upon debt extinguishment	(1,613,067)	0
Repayments of long-term debt	(15,000,000)	(2,320,083)
Repayments of equipment line of credit	(313,052)	0
Net cash used in financing activities	(16,819,328)	(1,295,688)
Effect of exchange rate changes on cash and cash equivalents	2,411	(2,473)
Net change in cash and equivalents	(6,131,203)	(44,914,067)
Cash and cash equivalents—Beginning of period	13,915,094
Cash and cash equivalents—End of period	7,783,891	22,578,980
Supplementary disclosure of cash flow activity:
Cash paid for taxes	800	4,560
Cash paid for interest	629,952	536,727
Supplemental disclosure of non-cash investing and financing activities:
Preferred stock dividends accrued	12,120	12,120
Leasehold improvements paid for by lessor	$ 0	$ 1,860,000