CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Operating activities
Net loss	$ (4,786,177)	$ (9,999,537)
Adjustments to reconcile net loss to net cash used in operating activities:
Impairment loss	0	485,000
Depreciation and amortization	252,480	330,968
Stock based compensation expense	1,406,131	920,799
Accretion of final fee premium	0	125,012
Amortization of discount on debt	0	68,223
Amortization of premiums on short-term investments	0	10,877
Deferred rent	(79,586)	(66,119)
Interest income accrued on short-term investments	0	151,583
Change in fair value of derivative financial instruments—warrants	129,689	(555,506)
Changes in operating assets and liabilities:
(Increase) decrease in accounts receivable and unbilled receivable	72,674	20,112
Decrease in prepaid expenses and other current assets	97,684	110,957
Increase (decrease) in accounts payable and accrued expenses	50,958	(360,577)
Net cash used in operating activities	(2,856,147)	(8,758,208)
Investing activities:
Capital expenditures, net	(5,100)	(11,452)
Maturities of short-term investments	0	14,000,000
Purchases of short-term investments	0	(8,804,604)
Net cash (used in) provided by investing activities	(5,100)	5,183,944
Financing activities:
Proceeds from exercise of warrants	1,449,167	0
Repayments of equipment line of credit	(156,526)	(156,526)
Net cash provided by (used in) financing activities	1,292,641	(156,526)
Effect of exchange rate changes on cash and cash equivalents	0	(844)
Net change in cash and equivalents	(1,568,606)	(3,731,634)
Cash and cash equivalents—Beginning of period	8,225,764	13,915,094
Cash and cash equivalents—End of period	6,657,158	10,183,460
Supplementary disclosure of cash flow activity:
Cash paid for interest	16,417	300,040
Supplemental disclosure of non-cash investing and financing activities:
Preferred stock dividends accrued	$ 6,060	$ 6,060