Stock-Based Compensation (Tables)

3 Months Ended

Mar. 31, 2015

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Our stock-based compensation expense for the three months ended March 31 was as follows:


	Three months ended March 31,
	2015			2014
Research and development expense	$	583,669		$	186,293
General and administrative expense		725,225			334,813

Total stock-based compensation	$	1,308,894		$	521,106

Effect on basic and diluted net loss per share	$	(0.02	)	$	(0.01	)

Stock Option Activity

A summary of our stock option activity for the three months ended March 31, 2015 is as follows:


	Number of options			Weighted-average exercise price ($) per share
Outstanding options at December 31, 2014		302,729			18.18
Granted		—			—
Exercised		—			—
Cancelled		(26,500	)		13.18

Outstanding options at March 31, 2015		276,229			18.66

Summary of Changes in Restricted Stock Unit Activity

A summary of changes in our restricted stock units for the three months ended March 31, 2015 is as follows:


	Number of RSUs			Weighted Average Grant Date Fair Value ($)
Outstanding at December 31, 2014		3,374,940			1.55
Granted(1)		7,290,768			1.11
Vested and exercised		(634,090	)		1.21
Cancelled		(47,100	)		1.51

Outstanding at March 31, 2015		9,984,518			1.25

(1)

349,518 of these restricted stock units vest and convert into shares of our common stock after one year from the date of grant. 2,586,750 of these restricted stock units will vest and convert into shares of our common stock over a three year period from the date of grant; one-third of the award will vest on each grant date anniversary following the grant. 4,354,500 of these restricted stock units are performance based and vest on achievement of predefined milestones.