Stock-Based Compensation (Tables)

3 Months Ended

Mar. 31, 2020

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Stock-Based Compensation Expense on All Employee and Non-Employee Awards

The Company recognized stock-based compensation expense on all employee and non-employee awards as follows:

	For the three months ended March 31,
(in thousands)	2020		2019
Research and development	$	530	$	433
General and administrative		1,410		1,023
Stock-based compensation expense	$	1,940	$	1,456

Fair Value of Stock Options Assumptions Using Black-Scholes Option Valuation Model

For the three months ended March 31, 2020 and 2019, the fair value of stock options was estimated on the date of grant using a Black-Scholes option valuation model with the following assumptions:

	For the three months ended March 31,
	2020		2019
Risk-free interest rate		0.50 - 1.68%		2.28 - 2.53%
Expected life in years		6 - 6.25		6 - 6.25
Expected volatility		71.11 - 73.01%		78.87 - 85.00%
Expected dividend yield		0%		0%

Stock Option Activity under Stock Option Plan

Stock option activity under the Company’s stock option plan for the three months ended March 31, 2020 is as follows:

(in thousands, except share and per share data)	Number of Shares			Weighted- Average Exercise Price		Weighted- Average Contractual Term (Years)		Aggregate Intrinsic Value
Outstanding, December 31, 2019		5,842,879		$	3.21
Granted		896,000			4.17
Exercised		(2,333	)		1.87
Cancelled		(59,667	)		4.67
Outstanding, March 31, 2020		6,676,879		$	3.95		8.15	$	864
Options exercisable, March 31, 2020		3,024,728		$	4.05		6.83	$	509
Options exercisable, December 31, 2019		2,765,357		$	4.39		6.70	$	3,603
Options available for future grant		1,066,275

Summary of Unvested Restricted Stock

A summary of the status of unvested restricted stock for the three months ended March 31, 2020 is as follows:

	Number of Shares		Weighted-Average Grant Date Fair Value
Non-vested, December 31, 2019		939,636	$	2.93
Granted		555,900		4.21
Vested		—		—
Cancelled		—		—
Non-vested, March 31, 2020		1,495,536	$	3.41