8.	Preferred Stock Warrant Liability

In September 2013, the Company issued a warrant to purchase 92,127 shares of Series A-2 convertible preferred stock in connection with the loan and security agreement (see Note 7). The warrant was immediately exercisable at an exercise price of $1.78 per share and had a contractual term of ten years from issuance. The fair value of the warrant at issuance was estimated to be $156 and was recorded as a debt discount and as a preferred stock warrant liability.

The Company remeasured the fair value of the liability for this preferred stock warrant at each reporting date from its grant date, with any adjustments being recorded as a component of other income (expense), net in the Company’s consolidated statement of operations and comprehensive loss. The Company recorded losses of $7, $1,418 and $8 for the years ended December 31, 2015, 2014 and 2013, respectively, to reflect the change in fair value of this preferred stock warrant.

The following assumptions and inputs were used in determining the fair value of the preferred stock warrant liability valued using the Black-Scholes option-pricing model:

	Year Ended December 31,
	2015			2014			2013
Risk-free interest rate		2.40	%		2.17	%		3.20	%
Expected term (in years)		8.2			8.7			9.7
Expected volatility		91.2	%		84.0	%		86.0	%
Expected dividend yield		0	%		0	%		0	%
Fair value of Series A-2 convertible preferred stock	$	17.26		$	17.18		$	2.07

The following table provides a rollforward of the fair value of the Company’s preferred stock warrant liability:

	Fair Value
Balance as of December 31, 2012	$	—
Issuance of Series A-2 preferred stock warrant		156
Loss on revaluation		8
Balance as of December 31, 2013		164
Loss on revaluation		1,418
Balance as of December 31, 2014	$	1,582
Loss on revaluation		7
Reclassification to stockholders’ equity		(1,589	)
Balance as of December 31, 2015	$	—

In connection with the automatic conversion of the Company’s convertible preferred stock, which occurred upon the listing of the Company’s common stock on the NASDAQ on June 26, 2015, the preferred stock warrant became a warrant to purchase common stock. The Company performed the final mark to market adjustment on the preferred stock warrant using the fair value of the underlying common shares of $18.00 per share on June 26, 2015 and recorded the change in fair value in other income (expense), net in the consolidated statement of operations and comprehensive loss. The preferred stock warrant liability was then reclassified to additional paid-in-capital as it became a warrant to purchase common stock.

On August 17, 2015, the common stock warrant was exercised in full at an exercise price of $1.78 per share of common stock. The Company received proceeds of $164 in connection with the exercise of the common stock warrant.