Stockholders' Equity

9 Months Ended

Sep. 30, 2019

Stockholders' Equity Note [Abstract]

Preferred Stock

In connection with the IPO in May 2018, 76,235,050 shares of convertible preferred stock were converted into 12,111,710 shares of common stock, resulting in the reclassification of the related convertible preferred stock of $119.1 million to common stock and APIC. As of September 30, 2019, no preferred stock had been issued.

Preferred Stock Warrants and Common Stock Warrants

In connection with the borrowing completed in February 2018 (see Note 5), we issued 233,577 ten-year warrants to purchase Series F preferred shares of stock at an exercise price of $1.37 per share. Based on the Black-Scholes option pricing model, the value of each warrant was determined to be $0.44 for a total value of $0.1 million at the date of issuance and was fully expensed during the three months ended March 31, 2018.

The preferred stock warrants issued in connection with the execution of the original credit facility and its subsequent amendments required re-measurement of the value of the preferred stock warrants each period, with changes in fair value recognized within other expenses on the statements of operations and comprehensive loss. The fair value of the preferred stock warrants was determined using the Black-Scholes option pricing model.

As of May 7, 2018, the date of the closing of our IPO, the following preferred stock warrants issued under the original credit facility and subsequent amendments were outstanding and exercisable:


Issuance	Expiration	Series	Exercise Price				Warrants Outstanding at May 7, 2018			Initial Value			Fair Value at May 7, 2018
February 8, 2018	February 8, 2028	F		$	1.37	233,577		$	103		$	320
February 24, 2017	February 24, 2027	F		1.37		29,197		4			40
August 7, 2015	August 7, 2025	E		2.62		29,580		33			41
June 27, 2014	June 27, 2024	E		2.62		76,334		85			174
August 5, 2013	August 5, 2023	C		1.07		74,768		39			80
November 16, 2012	November 16, 2022	C		1.07		186,916		96			200
Total						630,372					$	855

In connection with the closing of the IPO in May 2018, the warrants to purchase shares of preferred stock automatically converted into warrants to purchase shares of common stock, resulting in the reclassification of the related convertible preferred stock warrant liability of $0.9 million to APIC. Upon the closing of the IPO, the warrants to purchase 630,372 shares of preferred stock at a weighted average exercise price of $1.46 per share became exercisable to purchase 100,558 shares of common stock at weighted average exercise price of $9.38 per share. During 2018, warrants for 93,963 shares were exercised through cashless exercises, resulting in the issuance of a net 76,762 shares of our common stock. During the nine months ended September 30, 2019, warrants for 6,595 shares were exercised through cashless exercises, resulting in the issuance of a net 5,102 shares of our common stock.

Warrants to purchase shares of our common stock are summarized below:


	Common Stock Warrants	Weighted Average Exercise Price		Weighted Average Remaining Contractual Life (years)
Outstanding at December 31, 2018	6,595	$	15.16	5.5
Exercised	(6,595)	$	15.16
Outstanding at September 30, 2019	—	$	—