Arrowhead has two plans that provide for equity-based compensation. Under the 2004 Equity Incentive Plan and 2013 Incentive Plan, as of March 31, 2019, 1,440,218 and 5,654,798 shares, respectively, of Arrowhead’s Common Stock are reserved for the grant of stock options, stock appreciation rights, restricted stock awards and performance unit/share awards to employees, consultants and others. No further grants may be made under the 2004 Equity Incentive Plan. As of March 31, 2019, there were options granted and outstanding to purchase 1,440,218 and 3,270,048 shares of Common Stock under the 2004 Equity Incentive Plan and the 2013 Incentive Plan, respectively, and there were 2,049,333 restricted stock units granted and outstanding under the 2013 Incentive Plan. Also, as of March 31, 2019, there were 776,834 shares reserved for options and 2,000 shares reserved for restricted stock units issued as inducement grants to new employees outside of equity compensation plans. During the three months ended March 31, 2019, 517,500 options and 1,398,429 restricted stock units were granted under the 2013 Incentive Plan, and 148,000 options and 2,000 restricted stock units were granted as inducement awards to new employees outside of equity incentive plans. During the six months ended March 31, 2019, 517,500 options and 1,401,888 restricted stock units were granted under the 2013 Incentive Plan, and 195,000 options and 2,000 restricted stock units were granted as inducement awards to new employees outside of equity incentive plans.

	Number of Options Outstanding			Weighted- Average Exercise Price Per Share		Weighted- Average Remaining Contractual Term	Aggregate Intrinsic Value
Balance At September 30, 2018		5,524,399		$	6.14
Granted		712,500		13.26
Cancelled		(47,557	)	7.01
Exercised		(702,242	)	5.23
Balance At March 31, 2019		5,487,100		$	7.17	6.0 years	$	61,552,640
Exercisable At March 31, 2019		4,052,157		$	6.26	5.0 years	$	49,183,457

Stock-based compensation expense related to stock options for the three months ended March 31, 2019 and 2018 was $1,017,065 and $858,005, respectively. Stock-based compensation expense related to stock options for the six months ended March 31, 2019 and 2018 was $1,807,500 and $1,758,664, respectively. For non-qualified stock options, the expense creates a timing difference, resulting in a deferred tax asset, which is fully reserved by a valuation allowance.

The grant date fair value of the options granted by the Company for the three months ended March 31, 2019 and 2018 was $7,580,360 and $1,944,007, respectively. The grant date fair value of the options granted by the Company for the six months ended March 31, 2019 and 2018 was $8,137,249 and $2,292,906, respectively

The intrinsic value of the options exercised during the three months ended March 31, 2019 and 2018 was $6,806,594 and $350,674, respectively. The intrinsic value of the options exercised during the six months ended March 31, 2019 and 2018 was $8,122,294 and $350,674, respectively.

As of March 31, 2019, the pre-tax compensation expense for all outstanding unvested stock options in the amount of approximately $11,164,000 will be recognized in the Company’s results of operations over a weighted average period of 3.4 years.

The fair value of each stock option award is estimated on the date of grant using the Black-Scholes option pricing model. The Black-Scholes option valuation model was developed for use in estimating the fair value of traded options, which do not have vesting restrictions and are fully transferable. The determination of the fair value of each stock option is affected by the Company’s stock price on the date of grant, as well as assumptions regarding a number of highly complex and subjective variables. Because the Company’s employee stock options have characteristics significantly different from those of traded options, and because changes in the subjective input assumptions can materially affect the fair value estimate, in management’s opinion, the existing models do not necessarily provide a reliable single measure of the fair value of its employee stock options.

	Six Months Ended March 31,
	2019	2018
Dividend yield	—	—
Risk-free interest rate	2.3 – 3.1%	2.1 – 2.7%
Volatility	115%	110%
Expected life (in years)	6.25	6.25
Weighted average grant date fair value per share of options granted	$11.42	$3.47

Volatility is estimated based on volatility average of the Company’s Common Stock price.

Restricted stock units (RSUs), including time-based and performance-based awards, were granted under the Company’s 2013 Incentive Plan and as inducement grants granted outside of the Plan. During the three months ended March 31, 2019, the Company issued 1,398,429 RSUs under the 2013 Incentive Plan and 2,000 RSUs as inducement awards to new employees outside of equity incentive plans. During the six months ended March 31, 2019, the Company issued 1,401,888 RSUs under the 2013 Incentive Plan and 2,000 RSUs as inducement awards to new employees outside of equity incentive plans. At vesting, each outstanding RSU will be exchanged for one share of the Company’s Common Stock. RSU recipients may elect to net share settle upon vesting, in which case the Company pays the employee’s income taxes due upon vesting and withholds a number of shares of Common Stock of equal value. RSU awards generally vest subject to the satisfaction of service requirements or the satisfaction of both service requirements and achievement of certain performance targets.

	Number of RSUs			Weighted- Average Grant Date Fair Value
Unvested at September 30, 2018		2,968,500		$	2.99
Granted		1,403,888			12.43
Vested		(2,197,305	)		2.78
Forfeited		(123,750	)		8.98
Unvested at March 31, 2019		2,051,333		$	9.32

During the three months ended March 31, 2019 and 2018, the Company recorded $1,584,283 and $598,808 of expense related to RSUs, respectively. During the six months ended March 31, 2019 and 2018, the Company recorded $3,511,381 and $1,790,690 of expense related to RSUs, respectively. Such expense is included in stock-based compensation expense in the Company’s Consolidated Statement of Operations and Comprehensive Loss. For RSUs, the expense creates a timing difference, resulting in a deferred tax asset, which is fully reserved by a valuation allowance.

For RSUs, the grant date fair value of the award is based on the Company’s closing stock price at the grant date, with consideration given to the probability of achieving performance conditions for performance-based awards.

As of March 31, 2019, the pre-tax compensation expense for all unvested RSUs in the amount of approximately $9,551,860 will be recognized in the Company’s results of operations over a weighted average period of 3.3 years.