Fair Value Measurements (Tables)

9 Months Ended

Sep. 30, 2016

Fair Value Measurements

Assets and liabilities measured at fair value on a recurring basis

Assets and liabilities measured at fair value on a recurring basis as of September 30, 2016 and December 31, 2015 are as follows:

			Quoted Prices		Significant
			in Active		Other		Significant
			Markets for		Observable		Unobservable
			Identical Assets		Inputs		Inputs
Assets	Total		(Level 1)		(Level 2)		(Level 3)
September 30, 2016	(in thousands)
Money market funds included in cash and cash equivalents	$	63,008	$	63,008	$	—	$	—
Marketable securities:
U.S. Treasury notes		112,486		112,486		—		—
U.S. Government agency securities		15,160		—		15,160		—
Equity securities		2,416		2,416		—		—
Total marketable securities	$	130,062	$	114,902	$	15,160	$	—
Warrants to purchase equity securities		1,559		—		1,559		—
Total	$	194,629	$	177,910	$	16,719	$	—
December 31, 2015
Money market funds included in cash and cash equivalents	$	29,601	$	29,601	$	—	$	—
Marketable securities:
U.S. Treasury notes		157,981		157,981		—		—
U.S. Government agency securities		35,055		—		35,055		—
Total marketable securities		193,036		157,981		35,055		—
Total	$	222,637	$	187,582	$	35,055	$	—

Assumptions

The assumptions utilized to value the warrants to purchase equity securities on the acquisition date, September 2, 2016, and as of September 30, 2016 are as follows:

	As of September 2,		As of September 30,
	2016		2016
Risk-free interest rate	1.2	%	1.1	%
Expected dividend yield	—	%	—	%
Expected term (in years)	5.0		4.9
Expected volatility	92.3	%	92.3	%