Share-based Compensation

3 Months Ended

Sep. 30, 2019

Note 11. Share-based Compensation

We use equity-based compensation programs to provide long-term performance incentives for our employees. These incentives consist primarily of stock options and RSUs.

Our 2008 Stock Omnibus Equity Compensation Plan (the “2008 Plan”) provides for the grant of options and/or other share-based or share-denominated awards to our

non-employee

directors, officers, employees and advisors. The 2008 Plan was initially adopted in 2008 and was amended and restated in 2011, 2013, 2014, 2015, 2016 and 2018. There are 19,089,794 shares of common stock authorized for issuance under the 2008 Plan. As of September 30, 2019, there were 6,979,777 shares available for future grant under the 2008 Plan.

Total share-based compensation expense for all stock awards consists of the following, (in thousands):


	Three Months Ended September 30,
	2019		2018
Research and development	$	781	$	630
General and administrative		1,332		1,307

Total share-based compensation	$	2,113	$	1,937

Stock Options

Stock option activity for the three months ended September 30, 2019 was as follows:


	Number of Options			Weighted- Average Exercise Price		Weighted-Average Remaining Contractual Term (in years)		Aggregate Intrinsic Value
Outstanding at June 30, 2019		8,356,961		$	3.20
Granted		3,083,333			2.50
Exercised		(46,667	)		1.54
Forfeited / Cancelled		(49,186	)		1.81
Expired		(527,080	)		6.89

Outstanding at September 30, 2019		10,817,361			2.83		8.5	$	501,818

Vested and exercisable at September 30, 2019		4,114,253			2.52		7.3	$	428,455

The fair value of each stock option granted during the three months ended September 30, 2019 is estimated on the grant date under the fair value method using a Black-Scholes valuation model. Stock options granted to employees during the three months ended September 30, 2019 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 during the three months ended September 30, 2019 vest ratably each month for a period of 12 or 36 months from the date of grant and expire ten years from the date of grant. The estimated fair values of the stock options, including the effect of estimated forfeitures, are expensed over the service period.

The following weighted-average assumptions were used to determine the fair value of options granted during the period:


	Three Months Ended September 30,
	2019			2018
Risk-free interest rate		1.8	%		2.8	%
Expected life (years)		6.0			6.0
Expected volatility		73.6	%		86.0	%
Dividend yield		0.0	%		0.0	%
Weighted-average grant date fair value	$	1.63		$	3.11

As of September 30, 2019, there was $8.5 million of unrecognized compensation expense related to the unvested portion of stock options. Such compensation expense is expected to be recognized over a weighted-average period of 1.8 years.

Restricted Stock Units

In June 2016, we granted 364,726 RSUs to employees. Each RSU represented the contingent right to receive one share of our common stock. The RSUs vested in August 2018, and we released 332,193 RSU shares. We issued 245,782 shares of common stock to RSU holders; 86,411 shares were surrendered to us by RSU holders as payment for the employee portion of the required withholding of associated payroll taxes.