Stockholders' Equity

12 Months Ended

Dec. 31, 2018

Stockholders' Equity Note [Abstract]

Preferred Stock

A summary of preferred stock and its terms as of December 31, 2017, is as follows:


Series	Shares Authorized	Shares Issued and Outstanding	Carrying Value		Liquidation Preference per Share					8% Dividend per Share			Conversion Price per Share
A	5,375,507	5,375,507	$	5,037		$	1.00	$	0.08		$	6.65
B	8,706,909	8,706,909	15,913			1.84		0.15			9.91
C	14,091,589	13,829,906	14,949			1.07		0.09			7.12
D	5,683,292	5,683,292	6,043			1.07		0.09			7.12
E	15,373,091	15,267,175	39,848			2.62		0.21			15.16
F	27,664,232	27,372,261	37,316			1.37		0.11			9.11
Total	76,894,620	76,235,050	$	119,106

In connection with the IPO in May 2018, the 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 December 31, 2018, no preferred stock had been issued.

The dividend per share on the convertible preferred stock was only payable when and if declared by the board of directors.

Preferred Stock Warrants and Common Stock Warrants

In connection with the execution of the amendment to the current credit facility completed in February 2017 (see Note 5), we issued 29,197 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 $0.13, for a total value of less than $0.1 million at the date of issuance and was fully expensed during the year ended December 31, 2017.

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 year ended December 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 December 31, 2017, the following preferred stock warrants issued under our original credit facility and subsequent amendments were outstanding and exercisable:


Issuance	Expiration	Series	Exercise Price				Warrants Outstanding at December 31, 2017			Initial Value			Fair Value at December 31, 2017
February 24, 2017	February 24, 2027	F		$	1.37	29,197		$	4		$	13
August 7, 2015	August 7, 2025	E		2.62		29,580		33			8
June 27, 2014	June 27, 2024	E		2.62		76,334		85			21
August 5, 2013	August 5, 2023	C		1.07		74,768		39			33
November 16, 2012	November 16, 2022	C		1.07		186,916		96			82
Total						396,795					$	157

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.

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, 2017	—	$	—
Preferred stock warrants converted to common stock warrants at IPO	100,558	$	9.38
Exercised	(93,963)	$	8.70
Outstanding at December 31, 2018	6,595	$	15.16	5.5