Convertible Preferred Stock and Stockholders' Equity (Deficit) (Tables)

12 Months Ended

Dec. 31, 2013

Convertible Preferred Stock and Stockholders' Equity (Deficit)

Schedule of the authorized, issued and outstanding shares of convertible preferred stock by series

The authorized, issued and outstanding shares of convertible preferred stock by series immediately prior to October 4, 2013 (the date each convertible preferred outstanding share was converted to common stock as a result of the Company's IPO) is as follows:

	Shares Authorized		Shares Outstanding
Series A		14,609,186		14,609,186
Series B		12,080,000		12,050,000
Series B-1		1,500,000		1,500,000
Series C		29,000,000		16,808,504
Series C-1		11,171,000		—
		68,360,186		44,967,690

Summary of information about the Company's stock option activity

Information about the Company's stock option activity is as follows (in thousands, except share and per share data):

	Years Ended December 31,
	2013		2012		2011
Weighted-average grant date fair value per share of employee options granted	$	4.40	$	1.11	$	1.24
Cash received upon exercise of options	$	23	$	15	$	14

Schedule of allocation of stock-based compensation for all options and restricted stock awards

 The allocation of stock-based compensation for all options granted and restricted stock awards are as follows (in thousands):

	Years Ended December 31,
							Period from April 27, 2007 (inception) to December 31, 2013
	2013		2012		2011
Research and development	$	912	$	97	$	156	$	1,569
General and administrative		642		58		16		754
Total stock-based compensation expense	$	1,554	$	155	$	172	$	2,323

Schedule of common stock reserved for future issuance

	December 31,
	2013		2012
Conversion of convertible preferred stock		—		7,229,590
Stock warrants		36,074		36,074
Common stock options		1,726,991		1,432,369
Awards available under the 2013 Plan		1,003,526		154,448
Exchangeable shares		403,842		884,605
Employee stock purchase plan		729,000		—
		3,899,433		9,737,086

Employee stock option

Convertible Preferred Stock and Stockholders' Equity (Deficit)

Schedule of weighted-average assumptions used to determine the fair value of stock option grants

	Years Ended December 31,
	2013			2012			2011
Risk-free interest rate		1.6	%		1.0	%		1.1	%
Expected volatility		90	%		94	%		90	%
Expected term (in years)		5.9			6.1			6.1
Expected dividend yield		0.0	%		0.0	%		0.0	%

Non-employee stock option

Convertible Preferred Stock and Stockholders' Equity (Deficit)

Schedule of weighted-average assumptions used to determine the fair value of stock option grants

	Years Ended December 31,
	2013			2012			2011
Risk-free interest rate		2.1	%		1.2	%		1.1	%
Expected volatility		91	%		94	%		90	%
Expected term (in years)		7.3			7.5			6.1
Expected dividend yield		0.0	%		0.0	%		0.0	%

Combined plans

Convertible Preferred Stock and Stockholders' Equity (Deficit)

Summary of stock option activity under the Plan

	Options			Weighted Average Exercise Price Per Share		Weighted Average Remaining Contractual Term		Aggregate Intrinsic Value (in 000s)
Outstanding at December 31, 2012		1,432,369		$	1.43		9.14	$	51
Granted		355,780			5.60
Exercised		(35,853	)		0.65
Cancelled		(25,305	)		2.24
Outstanding at December 31, 2013		1,726,991		$	2.30		8.47	$	7,203
Options vested and expected to vest at December 31, 2013		1,555,091		$	1.92		8.37	$	6,935
Options exercisable at December 31, 2013		668,667		$	1.52		7.89	$	3,190

Summary of outstanding restricted stock awards under the plan

	Inside the Plan				Outside the Plan
	Number of Shares		Weighted-Average Price		Number of Shares		Weighted-Average Price
Balance at December 31, 2013 and December 31, 2012		434,884	$	0.468		564,904	$	0.007