STATEMENTS OF CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS' EQUITY (DEFICIT) - USD ($)	Common stock	Additional Paid-in Capital	Cumulative Unrealized Loss on Investments	Cumulative Translation Adjustment	Accumulated Deficit	Total
Balance at Dec. 31, 2013	$ 2,220	$ 140,419,071			$ (89,872,238)	$ 50,549,053
Balance (in shares) at Dec. 31, 2013	22,199,256
Increase (Decrease) in Equity
Stock-based compensation expense		3,384,800				3,384,800
Cancellation of unvested restricted stock (in shares)	(9,193)
Exercise of stock options	$ 12	181,547				181,559
Exercise of stock options (in shares)	121,816
Conversion of warrants	$ 2	139,086				139,088
Conversion of warrants (in shares)	23,022
Issuance of convertible notes		15,183,803				15,183,803
Unrealized gain (loss) on investments			$ (8,117)			(8,117)
Cumulative translation adjustment				$ (69,031)		(69,031)
Net loss					(35,958,979)	(35,958,979)
Balance at Dec. 31, 2014	$ 2,234	159,308,307	(8,117)	(69,031)	(125,831,217)	33,402,176
Balance (in shares) at Dec. 31, 2014	22,334,901
Increase (Decrease) in Equity
Stock-based compensation expense		5,680,353				5,680,353
Issuance of restricted stock	$ 45	(45)
Issuance of restricted stock (in shares)	450,000
Sale of common stock	$ 144	2,583,745				2,583,889
Sale of common stock (in shares)	1,435,612
Exercise of stock options	$ 2	31,199				31,201
Exercise of stock options (in shares)	24,266
Conversion of convertible notes	$ 52	2,080,270				2,080,322
Conversion of convertible notes (in shares)	524,304
Unrealized gain (loss) on investments			7,146			7,146
Cumulative translation adjustment				(1,759)		(1,759)
Net loss					(49,724,054)	(49,724,054)
Balance at Dec. 31, 2015	$ 2,477	$ 169,683,829	$ (971)	$ (70,790)	$ (175,555,271)	$ (5,940,726)
Balance (in shares) at Dec. 31, 2015	24,769,083