Preferred Stock Warrants

12 Months Ended

Dec. 31, 2018

Equity [Abstract]

Preferred Stock Warrants

8. Preferred Stock Warrants

The Company accounted for its warrants to purchase shares of redeemable convertible preferred stock as liabilities as they were exercisable for a redeemable instrument. The Company continued to adjust the liability for changes in fair value of these warrants until they were exercised or converted to common stock warrants.

The following table summarizes the outstanding redeemable convertible preferred stock warrants and the corresponding exercise price as of December 31, 2017:

	Number of Shares Outstanding as of
	December 31, 2017		Exercise Price		Expiration Date
Series AA warrants		1,506	$	13.28	March 7, 2018
2009 Series B warrants		25,884	$	9.659	December 22, 2019
2014 Series B warrants		104,856	$	0.12	May 14, 2021
Convertible debt Series C-1 warrants		304,397	$	0.12	January 17, 2024
Term loan Series C-1 warrants		49,713	$	9.659	October 18, 2027
		486,356

In August 2018, as part of the Series D Financing, the Company issued warrants to purchase 368,582 shares of Series C-1 redeemable convertible preferred stock (the “2018 Series C-1 warrants”) at an exercise price of $0.12 per share.

In connection with the IPO in October 2018, all outstanding redeemable convertible preferred stock warrants were either exercised or converted to common stock warrants. During 2018, stockholders exercised the outstanding 2014 Series B warrants, convertible debt Series C-1 warrants and the 2018 Series C-1 warrants to purchase an aggregate of 764,034 shares of the Company’s redeemable convertible preferred stock and common stock, at a weighted-average exercise price of $0.12 per share. The outstanding 2009 Series B warrants and Term loan Series C-1 warrants were automatically converted into an aggregate of 75,597 common stock warrants, to which the liability was reclassified to stockholders’ equity.