Arrowhead has two plans that provide for equity-based compensation. Under the 2004 Equity Incentive Plan and 2013 Incentive Plan, as of September 30, 2020, 673,262 and 5,598,345 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 September 30, 2020, there were options granted and outstanding to purchase 673,262 and 2,611,625 shares of Common Stock under the 2004 Equity Incentive Plan and the 2013 Incentive Plan, respectively, and there were 2,588,000 restricted stock units granted and outstanding under the 2013 Incentive Plan. Also, as of September 30, 2020, there were 1,254,516 shares reserved for options and 936,025 shares reserved for restricted stock units issued as inducement grants to new employees outside of equity compensation plans.

	Number of Options Outstanding			Weighted- Average Exercise Price Per Share		Weighted- Average Remaining Contractual Term	Aggregate Intrinsic Value
Balance At September 30, 2019		4,773,670		$	8.16
Granted		951,500		48.19
Cancelled		(74,639	)	22.38
Exercised		(1,111,128	)	6.72
Balance At September 30, 2020		4,539,403		$	16.67	6.2 years	$	129,100,277
Exercisable At September 30, 2020		2,924,744		$	8.30	4.8 years	$	102,698,309

Stock-based compensation expense related to stock options for the years ended September 30, 2020, 2019, and 2018 was $9,719,116, $3,955,216, and $3,265,348, 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 years ended September 30, 2020, 2019, and 2018 was $34,582,743, $12,137,250, and $4,141,318, respectively.

The intrinsic value of the options exercised during the years ended September 30, 2020, 2019 and 2018 was $44,082,294, $24,561,189, and $5,805,317, respectively.

As of September 30, 2020, the pre-tax compensation expense for all outstanding unvested stock options in the amount of $36,355,846 will be recognized in the Company’s results of operations over a weighted average period of 3.1 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.

	Years ended September 30,
	2020		2019			2018
Dividend yield		-		-			-
Risk-free interest rate	0.4 – 1.8%		1.50-3.11%			2.05-2.99%
Volatility	90-92%			115	%		110	%
Expected life (in years)		6.25		6.25			6.25
Weighted average grant date fair value per share of options granted	$	36.35	$	13.80		$	5.04

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 inducements grants granted outside of the Plan. During the year ended September 30, 2020, the Company issued 1,754,071 RSUs under the 2013 Incentive Plan and 933,025 RSUs as inducement awards. 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, 2019		2,062,833		$	9.43
Granted		2,687,096			55.59
Vested		(1,158,904	)		9.71
Forfeited		(67,000	)		31.78
Unvested at September 30, 2020		3,524,025		$	44.11

During the years ended September 30, 2020, 2019, and 2018, the Company recorded $33,663,871, $8,438,107 and $5,189,259 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 Income (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 September 30, 2020, the pre-tax compensation expense for all unvested RSUs in the amount of $88,548,649 will be recognized in the Company’s results of operations over a weighted average period of 3.1 years. Unvested RSUs that we have deemed not probable of vesting as of September 30, 2020, have the potential of generating an additional $38.0 million of pre-tax compensation expense if we deem them probable of vesting in a future reporting period.