Annual report pursuant to Section 13 and 15(d)

Stock-Based Payments (Tables)

Stock-Based Payments (Tables)

12 Months Ended

Dec. 31, 2020

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

A summary of the status of stock options as of December 31, 2020 and December 31, 2019 and changes during the year ended December 31, 2020 is presented below:

								Aggregate
				Weighted		Remaining		Intrinsic
				Average		Contractual		Value
	Shares			Exercise Price		Life (in years)		(in thousands)
Outstanding at December 31, 2019		4,618,421		$	9.16	7.5		$	2,525
Granted		1,195,050			7.87
Exercised		(170,723	)		6.30
Cancelled		(174,143	)		11.12
Outstanding at December 31, 2020		5,468,605		$	8.90		7.2	$	13,124
Exercisable at December 31, 2020		3,311,783		$	9.37		6.4	$	7,043

Summary of Status of Restricted Stock Units

A summary of the status of restricted stock units as of December 31, 2019 and December 31, 2020 and changes during the year ended December 31, 2020 is presented below:

				Weighted
				Average Grant
	Shares			Date Fair Value
Outstanding at December 31, 2019		1,116,358		$	6.75
Granted		859,500			8.15
Vested		(109,362	)		6.85
Forfeited		(132,113	)		7.26
Outstanding at December 31, 2020		1,734,383		$	7.40

Schedule of Weighted-Average Assumptions used in Black-Scholes Option-Pricing Model

The fair value of each stock option granted was estimated on the date of grant using the Black-Scholes option-pricing model based on the following weighted-average assumptions:

	Year Ended December 31,
	2020			2019			2018
Weighted-average risk-free interest rate		1.28	%		2.42	%		2.56	%
Expected dividend yield		—	%		—	%		—	%
Expected option term (in years)		5.99			6.00			6.04
Volatility		78.27	%		91.35	%		90.26	%

Summary of Stock-based Compensation Expense for Stock Options and Restricted Stock Units

The following table summarizes the stock-based compensation expense for stock options, restricted stock units and restricted common stock granted to employees and non-employees and from the 2016 ESPP recorded in the Company’s statements of operations:

	Year Ended December 31,
	2020		2019		2018
Research and development	$	4,732	$	3,472	$	2,412
General and administrative		6,207		6,367		4,198
Total stock-based compensation expense	$	10,939	$	9,839	$	6,610