The Company accounts for its warrants to purchase shares of redeemable convertible preferred stock as liabilities as they are exercisable for a redeemable instrument. The Company will continue to adjust the liability for changes in fair value of these warrants until the exercise of warrants or the consummation of the Company’s IPO, at which time the liability will be reclassified to stockholders’ equity.

The following table summarizes the outstanding redeemable convertible preferred stock warrants and the corresponding exercise price as of September 30, 2018 and December 31, 2017:

	Number of Shares Outstanding
	September 30,		December 31,
	2018		2017		Exercise Price		Expiration Date
Series AA warrants		—		1,506	$	13.28	March 7, 2018
2009 Series B warrants		25,884		25,884		9.659	December 22, 2019
2014 Series B warrants		104,856		104,856		0.12	May 14, 2021
Convertible debt Series C-1 warrants		304,397		304,397		0.12	January 17, 2024
Term loan Series C-1 warrants		49,713		49,713		9.659	October 18, 2027
2018 Series C-1 warrants		223,634		—		0.12	August 25, 2025
		708,484		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. Of those 2018 Series C-1 warrants, 144,948 were exercised in August and September 2018.

In connection with the IPO in October 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 632,887 shares of the Company’s redeemable convertible preferred stock, at a weighted-average exercise price of $0.12 per share, and all such shares were automatically converted into an aggregate of 632,888 shares of common stock upon the closing of the IPO on October 22, 2018.