Stock incentive plan (Tables)

12 Months Ended

Dec. 31, 2019

Schedule of available shares for grant under the Company’s stock option plan

The number of shares available for grant under the Company’s stock option plan were as follows (in thousands):


Available for grant as of January 1, 2018		2,419
Plan amendment		3,899
Grants		(2,515)
Forfeitures and cancellations		14
Available for grant as of December 31, 2018		3,817
Plan amendment		1,341
Grants		(2,955)
Forfeitures and cancellations		878
Available for grant as of December 31, 2019		3,081

Allocation of stock-based compensation expenses

Non‑cash stock‑based compensation expense recognized in the accompanying statements of operations relating to both stock options and restricted stock awards for the years ended December 31, 2019 and 2018 are as follows (in thousands):


	Year ended
	December 31,
	2019		2018
Research and development	$	2,442	$	866
General and administrative		6,594		2,452
Total stock‑based compensation expense	$	9,036	$	3,318

Schedule of restricted stock unit activity

The table below summarizes activity related to restricted stock units (in thousands, except per share amounts):


		Weighted‑
		average
		grant date
		fair value
	Shares	per share
Unvested as of December 31, 2018	-	$	-
Issued	1,183	$	3.63
Vested	(26)		3.63
Forfeited and canceled	(125)		3.63
Unvested as of December 31, 2019	1,032	$	3.63

Schedule of assumptions used to determine the fair value of the stock options granted


	Year ended December 31,
	2019	2018

Expected volatility	71%-75%	75%
Expected dividends	None	None
Expected option life	5.00 - 6.08 Years	6.08 Years
Risk-free rate	1.38 – 2.72%	2.81 – 3.06%

Summary of stock option activity

The table below summarizes activity related to stock options (in thousands, except per share amounts):


				Weighted‑
		Weighted‑		average
		average		remaining	Aggregate
		exercise		contractual	intrinsic
Options	Shares	price		term	value
Outstanding, January 1, 2018	1,498	$	2.48	8.93	$	4,146
Granted	2,515		10.40
Exercised	(40)		2.57
Forfeited and canceled	(14)		4.79
Outstanding, December 31, 2018	3,959	$	7.46	8.79	$	35,984
Granted	1,772		12.19
Exercised	(181)		2.07
Forfeited and canceled	(752)		11.70
Outstanding, December 31, 2019	4,798	$	8.75	8.29	$	1,159
Vested and expected to vest at December 31, 2019	4,798	$	8.75	8.29	$	1,159
Exercisable at December 31, 2019	2,139	$	5.64	7.87	$	928