Summary of Significant Accounting Policies (Tables)

3 Months Ended

Mar. 31, 2016

Summary of Assets and Liabilities Measured at Fair Value on Recurring Basis

The following table presents information about the Company’s assets as of March 31, 2016 and December 31, 2015 that are measured at fair value on a recurring basis and indicate the level of the fair value hierarchy utilized to determine such fair values (note there were no liabilities measured at fair value on a recurring basis in either of the periods presented):

	Fair Value Measurements as of March 31, 2016 Using:
	Level 1		Level 2		Level 3		Not Subject to Leveling ⁽¹⁾		Total
Assets:
Cash Equivalents	$	—	$	1,753	$	—	$	27,796	$	29,549
Investments:
Commercial Paper	$	—	$	56,020	$	—	$	—	$	56,020
Corporate Bonds		—		26,972		—		—		26,972
Government Securities		—		15,044		—		—		15,044
Treasury Bonds		—		12,014		—		—		12,014
	$	—	$	111,803	$	—	$	27,796	$	139,599
⁽¹⁾ Certain cash equivalents and investments that are valued using the net asset value per share (or its equivalent) practical expedient have not been classified in the fair value hierarchy.

	Fair Value Measurements as of December 31, 2015 Using:
	Level 1		Level 2		Level 3		Not Subject to Leveling ⁽¹⁾		Total
Assets:
Cash Equivalents	$	—	$	11,952	$	—	$	11,173	$	23,125
Repurchase Agreements		—		20,000		—		—		20,000
Investments:
Commercial Paper	$	—	$	64,820	$	—	$	—	$	64,820
Corporate Bonds		—		46,490		—		—		46,490
Government Securities		—		15,819		—		—		15,819
Treasury Bonds		—		4,020		—		—		4,020
	$	—	$	163,101	$	—	$	11,173	$	174,274
⁽¹⁾ Certain cash equivalents and investments that are valued using the net asset value per share (or its equivalent) practical expedient have not been classified in the fair value hierarchy.

Summary of Potential Common Shares Excluded from Calculation of Diluted Net Loss per Share

The following potential common shares, presented based on amounts outstanding at each period end, were excluded from the calculation of diluted net loss per share attributable to common stockholders for the periods indicated because including them would have had an anti-dilutive effect:

	Three Months Ended March 31,
	2016		2015
Stock options to purchase common stock		5,882,186		3,989,246
Unvested restricted common stock		—		26,875
Warrants for the purchase of convertible preferred stock		—		92,127
Warrants for the purchase of common stock		—		738,635
Convertible preferred stock (as converted to common stock)		—		22,866,987
		5,882,186		27,713,870