Warrants

In connection with the IPO, the Company's outstanding warrants to purchase 156,550 shares of redeemable convertible preferred stock were automatically converted into warrants to purchase an aggregate of 160,657 shares of common stock, resulting in reclassification of the related redeemable convertible preferred stock warrant liability of $1.2 million in additional paid-in-capital. In addition, warrants to purchase Series 6 Preferred Stock were converted to warrants to purchase common stock at a conversion ratio of 1:1.06.

Warrants issued and outstanding at December 31, 2018 are as follows(in thousands, except share and per share data):

Date

Number of
Shares
Underlying
Warrants

Price per
Share

Fair Value

Warrants to purchase

Issuance

Expiration

Common stock

3/1/2017

3/1/2027

[a]

1,388

5.94

[b]

Common stock

7/19/2013

7/22/2023

[a]

32,983

9.10

122

[b]

Common stock

11/26/2014

11/26/2024

[a]

6,680

16.47

[b]

Common stock

10/20/2015

10/20/2025

[a]

41,650

16.47

396

[c]

Common stock

11/9/2015

11/9/2025

[a]

25,709

16.47

244

[c]

Common stock

12/22/2016

12/22/2026

[a]

9,712

10.03

[c]

Total outstanding common stock warrants

118,122


[a]	Common stock warrants will remain outstanding until exercised by the holder.


[b]	Fair value at the date of issuance.


[c]	Fair value at the date of conversion from redeemable convertible preferred stock to common stock warrants in conjunction with the IPO on October 16, 2018.

Warrants issued and outstanding at December 31, 2017 are as follows (in thousands, except share and per share data):



	Series	Date			Number of Shares Underlying Warrants	Price per Share		Fair Value
Warrants to purchase	Series	Issuance	Expiration		Number of Shares Underlying Warrants	Price per Share		Fair Value
Common stock		7/19/2013	7/22/2023	[a]	101,010	$	3.96	$	244	[b]
Common stock		11/26/2014	11/26/2024	[a]	21,928	$	3.42	$	47	[b]
Common stock		3/1/2017	3/1/2027	[a]	1,388	$	5.94	$	5	[b]
Total common stock warrants					124,326

Redeemable convertible preferred stock	Series 5	7/1/2012	7/25/2019	[d]	54,917	$	9.10	$	255	[c]
Redeemable convertible preferred stock	Series 5	7/19/2013	7/22/2023	[e]	21,989	$	9.10	$	122	[c]
Redeemable convertible preferred stock	Series 6	11/26/2014	11/26/2024	[e]	6,310	$	16.47	$	49	[c]
Redeemable convertible preferred stock	Series 6	10/20/2015	10/20/2025	[e]	39,339	$	16.47	$	396	[c]
Redeemable convertible preferred stock	Series 6	11/9/2015	11/9/2025	[e]	24,283	$	16.47	$	244	[c]
Redeemable convertible preferred stock	Series 7	12/22/2016	12/22/2026	[e]	9,712	$	10.03	$	45	[c]
Total redeemable convertible preferred stock warrants					156,550
Total outstanding common and redeemable convertible preferred stock warrants					280,876


[a]	Common stock warrants will remain outstanding until exercised by the holder.


[b]	Fair value at the date of issuance.


[c]	Fair value as of December 31, 2017.


[d]	These warrants will be net exercised immediately upon the closing of the Company’s IPO, or upon a corporate transaction as defined in the Note and Warrant Purchase Agreement dated July 25, 2012.


[e]	Convertible preferred stock warrants will remain outstanding until exercised by the holder and will convert to common stock warrants upon an IPO. The warrants will be exercisable for 10 years from the date of issuance.

In connection with previously issued debt, the Company issued 101,010 warrants to purchase common shares of the Company at an exercise price of $3.96 per share in July 2013. Additionally, the Company issued warrants to purchase an additional 21,928 shares of common stock at an exercise price of $3.42 per share in November 2014. The Company determined that its warrants to purchase shares of common stock meet the requirements for equity classification.

In conjunction with debt issued in July 2012, the Company issued warrants which became exercisable for an aggregate of 54,917 shares of Series 5 preferred stock of the Company at an exercise price of $9.10 per share.

In conjunction with debt issued in 2013 and 2014, the Company issued 32,983 warrants to purchase Series 5 redeemable convertible preferred stock of the Company at an exercise price of $9.10 per share. Subsequently, the Company issued additional warrants to purchase 6,310 shares of Series 6 redeemable convertible preferred stock at an exercise price of $16.47 per share.

In conjunction with the debt agreement with SVB and Oxford, or Term Loan agreement (refer to Note 7), the Company issued warrants to purchase 39,339 shares of Series 6 redeemable convertible preferred stock at an exercise price of $16.47 per share in October 2015 and additional 24,283 shares of Series 6 redeemable convertible preferred stock at an exercise price of $16.47 per share in November 2015.

In conjunction with the Term Loan agreement and its modification (refer to Note 7), the Company issued additional warrants for the purchase of 9,712 shares of Series 7 redeemable convertible preferred stock at an exercise price of $10.03 per share in December 2016.

In March 2017, the Company issued a warrant to purchase 1,388 shares of common stock at an exercise price of $5.94 to a consultant. The Company determined that such warrant meets the requirements for equity classification.

In October 2017, the Company extinguished its debt with SVB and Oxford. All related debt discounts were written off upon repayment of the loan.

The Company estimates the fair value of warrants using the Black-Scholes option valuation model. The fair value is estimated using certain assumptions. Refer to Note 11. Stock-Based Incentive Compensation Plans, for further discussions on how the Company determines these input assumptions. Each of these inputs is subjective and its determination generally requires significant judgment. The fair value of warrants to purchase preferred stock were recorded at the date of issuance as a discount to debt and amortized to interest expense over the term of the note. The changes in the fair value of the redeemable convertible preferred stock warrants are recorded in other income and expense. Weighted-average assumptions used in computation of the fair value of the redeemable convertible preferred stock warrants are summarized in the table below:



	Year Ended December 31,
	2018		2017
Remaining contractual term (in years)	4.9		5.3
Expected volatility	53.89	%	59.06	%
Risk-free interest rate	2.62	%	2.16	%
Dividend yield	—	%	—	%