Arrowhead has three plans that provide for equity-based compensation. Under the 2004 Equity Incentive Plan and the 2013 Incentive Plan, as of March 31, 2021, 468,993 and 6,593,291 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, 2021, there were options granted and outstanding to purchase 468,993 and 2,229,852 shares of Common Stock under the 2004 Equity Incentive Plan and the 2013 Incentive Plan, respectively, and there were 3,177,950 restricted stock units granted and outstanding under the 2013 Incentive Plan. Also, as of March 31, 2021, there were 1,080,741 shares reserved for options and 676,200 shares reserved for restricted stock units issued as inducement grants to new employees outside of equity compensation plans. On March 18, 2021, the Company’s stockholders approved the Arrowhead Pharmaceuticals, Inc. 2021 Incentive Plan (“2021 Incentive Plan”), which authorizes 8,000,000 shares (subject to certain adjustments) to be awarded for grants of stock options, stock appreciation rights, restricted and unrestricted stock and stock units, performance awards, cash awards and other awards convertible into or otherwise based on shares of Arrowhead’s Common Stock. The maximum number of shares authorized under the 2021 Incentive Plan will be (i) reduced by any shares subject to awards made under the 2013 Incentive Plan after January 1, 2021, and (ii) increased by any shares subject to outstanding awards under the 2013 Incentive Plan as of January 1, 2021 that, after January 1, 2021, are canceled, expired, forfeited or otherwise not issued under such awards (other than as a result of being tendered or withheld to pay the exercise price or withholding taxes in connection with any such awards) or settled in cash. As of March 31, 2021, there had been no adjustments to the 8,000,000 authorized shares under the 2021 Incentive Plan, and 0 shares of Arrowhead’s Common Stock had been granted under the 2021 Incentive Plan.

	Number of Options Outstanding			Weighted- Average Exercise Price Per Share		Weighted- Average Remaining Contractual Term	Aggregate Intrinsic Value
Balance at September 30, 2020		4,539,403		$	16.67
Granted		168,000		65.41
Cancelled		(108,149	)	28.85
Exercised		(819,668	)	9.44
Balance at March 31, 2021		3,779,586		$	20.06	6.1 years	$	175,292,764
Exercisable at March 31, 2021		2,426,786		$	10.64	4.8 years	$	135,141,412

Stock-based compensation expense related to stock options for the three months ended March 31, 2021 and 2020 was $3.3 million and $2.5 million, respectively. Stock-based compensation expense related to stock options for the six months ended March 31, 2021 and 2020 was $6.4 million and $4.1 million, 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, 2021 and 2020 was $1.4 million and $18.0 million, respectively. The grant date fair value of the options granted by the Company for the six months ended March 31, 2021 and 2020 was $8.1 million and $26.6 million, respectively.

The intrinsic value of the options exercised during the three months ended March 31, 2021 and 2020 was $20.9 million and $8.6 million, respectively. The intrinsic value of the options exercised during the six months ended March 31, 2021 and 2020 was $52.8 million and $30.2 million, respectively.

As of March 31, 2021, the pre-tax compensation expense for all outstanding unvested stock options in the amount of $35.7 million will be recognized in the Company’s results of operations over a weighted average period of 2.9 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,
	2021		2020
Dividend yield		-		-
Risk-free interest rate	0.4 – 0.6%		0.5-1.8%
Volatility	86.6 – 90.4%		90.5 – 91.8%
Expected life (in years)		6.25		6.25
Weighted average grant date fair value per share of options granted	$	48.62	$	40.70

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 Company’s equity-based compensation plans. During the three months ended March 31, 2021, the Company issued 1,324,750 RSUs under the 2013 Incentive Plan and 0 RSUs as inducement awards. During the six months ended March 31, 2021, the Company issued 1,326,950 RSUs under the 2013 Incentive Plan and 116,000 RSUs as inducement awards. At vesting, each outstanding RSU will be exchanged for one share of the Company’s Common Stock. 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, 2020		3,524,025		$	44.11
Granted		1,442,950			75.54
Vested		(823,575	)		30.11
Forfeited		(289,250	)		39.14
Unvested at March 31, 2021		3,854,150		$	59.24

During the three months ended March 31, 2021 and 2020, the Company recorded $12.1 million and $10.4 million of expense related to RSUs, respectively. During the six months ended March 31, 2021 and 2020, the Company recorded $17.1 million and $13.3 million 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. The grant date fair value of the RSUs granted by the Company for the three months ended March 31, 2021 and 2020 was $101.6 million and $122.0 million, respectively. The grant date fair value of the RSUs granted by the Company for the six months ended March 31, 2021 and 2020 was $109.0 million and $136.0 million, respectively.

As of March 31, 2021, the pre-tax compensation expense for all unvested RSUs in the amount of $131.4 million 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 March 31, 2021, have the potential of generating an additional $76.4 million of pre-tax compensation expense if we deem them probable of vesting in a future reporting period.