Significant accounting policies (Tables)

12 Months Ended

Dec. 31, 2018

Significant accounting policies

Schedule of outstanding potentially dilutive securities that have been excluded in the calculation of diluted net loss per share

	Year Ended December 31,
	2018	2017	2016
Series A redeemable convertible preferred stock	—	—	4,884,869
Series B redeemable convertible preferred stock	—	—	1,873,561
Series C redeemable convertible preferred stock	—	—	2,677,649
Series D redeemable convertible preferred stock	—	—	3,864,421
Unvested restricted common stock	361,468	177,192	376,248
Outstanding stock options	2,476,911	2,249,843	1,119,671
Outstanding preferred warrants	—	—	326,374
Outstanding common stock warrants	76,041	86,090	—
Total	2,914,420	2,513,125	15,122,793

Schedule of cash and cash equivalents

are carried at fair value based on quoted prices for identical assets. Cash and cash equivalents consists of the following (in thousands):

	Year Ended December 31,
	2018		2017
Cash and Cash Equivalents
Cash	$	1,821	$	1,500
Money Market funds invested in U.S. Treasury obligations		42,608		78,182
Total cash and cash equivalents	$	44,429	$	79,682

Schedule of estimated useful lives

Laboratory and manufacturing equipment	Five years
Computers and software	Three years
Office furniture and equipment	Seven years
Leasehold improvements	Shorter of the useful life of the asset or the remaining term of the lease

Schedule of fair value measurements

Fair value measurements as of December 31, 2018 are as follows (in thousands):

			Quoted		Significant
			prices		other		Significant
			in active		observable		unobservable
			markets		inputs		inputs
Description	Total		(Level 1)		(Level 2)		(Level 3)
Financial Assets
Cash Equivalents	$	42,608	$	42,608		—	$	—
Note receivable		150		—		—		150
Total	$	42,758	$	42,608		—	$	150

Fair value measurements as of December 31, 2017 are as follows (in thousands):

			Quoted		Significant
			prices		other		Significant
			in active		observable		unobservable
			markets		inputs		inputs
Description	Total		(Level 1)		(Level 2)		(Level 3)
Financial Assets
Cash Equivalents	$	78,182	$	78,182		—		—
Total	$	78,182	$	78,182		—		—

Schedule of changes in preferred stock warrant liability measured at fair value

The changes in preferred stock warrant liability measured at fair value for which the Company has used Level 3 inputs to determine fair value are as follows (in thousands):

	Warrant
	liability
Balance at December 31, 2015	$	5,547
Issuance of warrants related to debt facility		128
Issuance of warrants related to a vendor		2,078
Changes in fair value of warrants		307
Warrant exercises		(5,258)
Balance at December 31, 2016		2,802
Issuance of warrants related to debt facility		119
Changes in fair value of warrants		90
Warrant exercises		(2,188)
Conversion to warrants to purchase common stock in connection with IPO		(823)
Balance at December 31, 2017	$	—

Schedule of assumptions were utilized to determine the fair value of each warrant to purchase preferred stock

Value of

Value of

Value of

Value of

Value of

underlying

underlying

underlying

underlying

underlying

Probability

Series D

Series C

Series B

Series A‑3

Series A‑2

of an initial

preferred

preferred

preferred

preferred

preferred

public

Balance sheet date

stock

stock

stock

stock

stock

Volatility

offering

December 7, 2017

$

4.67

$

4.67

N/A

$

4.67

$

4.67

46

%

100

%

Schedule of net revenue by product and service line

Net revenue by product and service line are as follows (in thousands):

	Year ended December 31,
	2018		2017		2016
Product revenue	$	23,365	$	14,124	$	10,601
Service and other revenue		12,117		7,676		5,012
Collaboration and license revenue		2,150		1,074		1,972
Total revenue	$	37,632	$	22,874	$	17,585

Schedule of total revenue by geography and as a percentage of total revenue

	Year ended December 31,
	2018				2017				2016
North America	$	22,706	60	%	$	13,864	61	%	$	13,018	74	%
EMEA		11,742	31	%		6,922	30	%		3,416	19	%
Asia Pacific		3,184	8	%		2,088	9	%		1,151	7	%
Total	$	37,632	100	%	$	22,874	100	%	$	17,585	100	%

Summary of fair value assumptions of stock options granted to employees and directors for their services on the Company's Board of Directors

	Year Ended December 31,
	2018		2017		2016
Risk-free interest rate	2.6% - 3.0	%	1.8% - 2.1	%	1.2% - 1.3	%
Expected dividend yield	None		None		None
Expected term (in years)	5.9		6.0		6.0
Expected volatility	32.4% - 36.8	%	46.0% - 52.0	%	44.9% - 49.0	%