Stock-based compensation expense is classified in the condensed consolidated statements of operations and comprehensive loss as follows:


	Three Months Ended September 30,				Nine Months Ended September 30,
	2023		2022		2023		2022
	(In thousands)				(In thousands)
Research and development	$	2,959	$	2,690	$	8,859	$	8,025
General and administrative		4,356		3,835		10,659		10,496
Total	$	7,315	$	6,525	$	19,518	$	18,521

The weighted-average grant date fair value of options, estimated as of the grant date using the Black Scholes option pricing model was $11.67 per option for the 2,625,427 options granted during the nine months ended September 30, 2023. The following assumptions were used to estimate the fair value of the options granted during the nine months ended September 30, 2023.


Volatility	68.3	%
Risk-free interest rate	3.6	%
Expected holding period (in years)	6.2
Dividend yield	-

In April 2020, Mark Throsby, Ph.D. resigned as the Executive Vice President and Chief Scientific Officer of the Company effective July 31, 2020. In connection with his departure, Mr. Throsby entered into a Settlement Agreement with the Company, pursuant to which Mr. Throsby received a severance payment equal to 8 months of his annual salary and amortized bonus aggregating approximately $0.3 million. Further, subject to Mr. Throsby’s continued compliance with the terms and conditions of the Settlement Agreement, Mr. Throsby’s unvested equity awards continued to vest until October 31, 2020 as if Mr. Throsby had continued in full time service with the Company through such date. The post-termination exercise period of Mr. Throsby's options was extended to March 31, 2021. The Company incrementally recognized $0.1 million in respect of the severance payment and a net reversal of $0.4 million of stock-based compensation expense in respect of share-based payments in research and development expense in the consolidated statement of operations in the prior year.

In March 2021, the Company and Mr. Throsby amended the Settlement Agreement and a Consulting Agreement, extending the post-termination expiration period of his outstanding options to extend to October 31, 2021, three months following his performance of certain consulting services through July 31, 2021. As a result, additional compensation cost of $0.2 million was recognized for the quarter ended March 31, 2021. In July 2021, the Company and Mr. Throsby entered into the 2nd Amendment to the Consulting Agreement, extending Mr. Throsby’s consulting services period to February 28, 2022, extending the post-termination period of his outstanding options to May 2022. As the modification occurred in Mr. Throsby’s post-employment period, the options cease to be within the scope of ASC 718 and are recharacterized as an issuance of a standalone derivative instrument. The Company recognized a $0.4 million net gain associated with the derivative instrument included as other income in the statement of operations for the three months ended March 31, 2022. The Company did not recognize any further gains or expenses during the three months ended September 30, 2023 and the Company does not expect to incur any further expenses as Mr. Throsby's option to exercise expired in May 2022.