Note 9 - Stock Options and Stock-based Employee Compensation

3 Months Ended

Mar. 31, 2021

Notes to Financial Statements

Share-based Payment Arrangement [Text Block]

Note

9

 - Stock Options and Stock-Based Employee Compensation

We recognize in our condensed consolidated financial statements all stock-based awards to employees and non-employee directors based on their fair value on the date of grant, calculated using the Black-Scholes option-pricing model. Compensation expense related to stock-based awards is recognized ratably over the vesting period, which for employees is typically

three

years. We recognize restricted stock unit awards to employees and non-employee directors based on their fair value on the date of grant. Compensation expense related to restricted stock unit awards is recognized ratably over the vesting period, which typically has been between approximately

six

to

18

months.

A summary of activity under our long-term incentive plans is presented below:

(in thousands, except for weighted-average data)
Stock Options	Shares			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term (In Yrs)
Outstanding at January 1, 2021		1,903		$	15.57
Granted		1,339			5.46
Forfeited or expired		(2	)		11.85
Outstanding at March 31, 2021		3,240		$	11.39		8.6
Vested and exercisable at March 31, 2021		1,353		$	17.19		7.5
Vested and expected to vest at March 31, 2021		3,020		$	11.50		8.5

The table below summarizes the total stock-based compensation expense included in the interim unaudited condensed consolidated statements of operations for the periods presented:

	Three Months Ended March 31,
(in thousands)	2021		2020
Research and development	$	939	$	714
General and administrative		1,504		975
Total	$	2,443	$	1,689

The fair value of each option award is estimated on the date of grant using the Black-Scholes option-pricing formula that uses assumptions noted in the following table. Expected volatilities are based upon the historical volatility of our common stock and other factors. We also use historical data and other factors to estimate option exercises, employee terminations and forfeiture rates. The risk-free interest rates are based upon the U.S. Treasury yield curve in effect at the time of the grant.

	Three Months Ended
	March 31, 2021
Weighted average expected volatility		105%
Weighted average expected term (in years)		6.6
Weighted average risk-free interest rate		0.48%
Expected dividends		-