We use share-based compensation programs to provide long-term performance incentives for our employees. These incentives consist primarily of stock options and restricted stock units (RSU). In December 2008, we adopted the MEI Pharma, Inc. 2008 Stock Omnibus Equity Compensation Plan (Omnibus Plan), as amended and restated from time to time, under which 1,850,739 shares of common stock are currently authorized for issuance. The Omnibus Plan provides for the grant of options and/or other stock-based or stock-denominated awards to our non-employee directors, officers, and employees. As of December 31, 2023, there were 439,101 shares available for future grant under the Omnibus Plan.

In May 2021, we adopted the 2021 Inducement Plan (Inducement Plan), under which 217,000 shares of common stock are authorized for issuance. The Inducement Plan is intended to assist us in attracting and retaining selected individuals to serve as employees who are expected to contribute to our success, by providing an inducement for such individuals to enter into employment with us, and to achieve long-term objectives that will benefit our stockholders. As of December 31, 2023, there were 116,734 shares available for future grant under the Inducement Plan.

Total share-based compensation expense for all stock awards consisted of the following for the periods presented (in thousands):


	For the Three Months Ended December 31,				For the Six Months Ended December 31,
	2023		2022		2023		2022
Research and development	$	129	$	201	$	60	$	850
General and administrative		721		612		1,153		1,522
Total share-based compensation	$	850	$	813	$	1,213	$	2,372

Stock options granted to employees vest 25% one year from the date of grant and ratably each month thereafter for a period of 36 months and expire ten years from the date of grant. Stock options granted to directors vest ratably each month for a period of 12 months from the date of grant and expire ten years from the date of grant. Of the total options outstanding of 1,397,748 as of December 31, 2023, 1,297,482 were granted under the Omnibus Plan and 100,266 were granted under the Inducement Plan.

A summary of our stock option activity and related data follows:


	Number of Options			Weighted-Average Exercise Price		Weighted-Average Remaining Contractual Term (in years)		Aggregate Intrinsic Value
Outstanding at June 30, 2023		1,284,907		$	38.32
Granted		260,437		$	6.90
Forfeited		(147,596	)	$	38.32
Outstanding at December 31, 2023		1,397,748		$	32.47		7.5	$	—
Vested and expected to vest at December 31, 2023		812,884		$	47.01		6.2	$	—

As of December 31, 2023, the aggregate intrinsic value of outstanding options was calculated as the difference between the exercise price of the underlying options and the closing price of our common stock of $5.80 on that date.

Unrecognized compensation expense related to non-vested stock options totaled $2.3 million as of December 31, 2023. Such compensation expense is expected to be recognized over a weighted-average period of 1.57 years. As of December 31, 2023, we expect all options to vest.

The weighted-average assumptions used in the Black-Scholes option pricing model to determine the fair value of option grants were as follows:


	For the Six Months Ended December 31,
	2023			2022
Risk-free interest rate		4.5	%		2.9	%
Expected life (years)		5.7			6.0
Volatility		90.0	%		84.1	%
Dividend yield		—	%		—	%
Weighted-average grant date fair value	$	5.18		$	7.80