As of March 31, 2024, we have two shareholder-approved equity incentive plans: the United Therapeutics Corporation Amended and Restated Equity Incentive Plan (the 1999 Plan) and the United Therapeutics Corporation Amended and Restated 2015 Stock Incentive Plan (the 2015 Plan). The 2015 Plan provides for the issuance of up to 12,500,000 shares of our

common stock pursuant to awards granted under the 2015 Plan. No further awards will be granted under the 1999 Plan. We also have one equity incentive plan, the United Therapeutics Corporation 2019 Inducement Stock Incentive Plan (the 2019 Inducement Plan), that has not been approved by our shareholders, as permitted by the Nasdaq Stock Market rules. The 2019 Inducement Plan was approved by our Board of Directors in February 2019 and provides for the issuance of up to 99,000 shares of our common stock under awards granted to newly-hired employees. Currently, we grant equity-based awards to employees and members of our Board of Directors in the form of stock options and restricted stock units (RSUs) under the 2015 Plan, and we may grant RSUs to newly-hired employees under the 2019 Inducement Plan. See the sections entitled Stock Options and RSUs below for additional information regarding these equity-based awards.

During the three months ended March 31, 2024 and 2023, we issued stock options and RSUs to certain executives with vesting conditions tied to the achievement of specified performance criteria through the end of 2026 and 2025, respectively. Throughout the performance period, we reassess the estimated performance and update the number of performance-based awards that we believe will ultimately vest. Estimating future performance requires the use of judgment. Upon the conclusion of the performance period, the performance level achieved and the ultimate number of stock options and RSUs that may vest are determined. Share-based compensation expense for these awards is recorded ratably over their vesting period, depending on the specific terms of the award and anticipated achievement of the specified performance criteria.

We previously issued awards under the United Therapeutics Corporation 2011 Share Tracking Awards Plan (the STAP). We refer to awards outstanding under the STAP as STAP awards. See the section entitled STAP Awards below for additional information regarding STAP awards. We discontinued the issuance of STAP awards in June 2015.

In 2012, our shareholders approved the United Therapeutics Corporation Employee Stock Purchase Plan (ESPP), which is structured to comply with Section 423 of the Internal Revenue Code. See the section entitled ESPP below for additional information regarding the ESPP.


	Three Months Ended March 31,
		2024		2023
Stock options		$	5.7	$	4.9
RSUs		15.5		12.2
STAP awards		3.9		(30.0)
ESPP		0.5		0.5
Total share-based compensation expense (benefit) before tax		$	25.6	$	(12.4)

We estimate the fair value of stock options using the Black-Scholes-Merton valuation model, which requires us to make certain assumptions that can materially impact the estimation of fair value and related compensation expense. The assumptions used to estimate fair value include the price of our common stock, the expected volatility of our common stock, the risk-free interest rate, the expected term of stock option awards, and the expected dividend yield.

During the three months ended March 31, 2024 and 2023, in addition to time-based stock options, we granted 0.5 million and 0.4 million performance-based stock options with a total grant date fair value of $50.2 million and $35.6 million, respectively, in each case calculated based on the assumed achievement of maximum performance of the relevant financial performance condition. During the three months ended March 31, 2024 and 2023, we recorded $4.8 million and $0.2 million, respectively, of share-based compensation expense related to performance-based stock options, calculated based on the assumed levels of performance achievement.


	Number of Options	Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (in Years)	Aggregate Intrinsic Value (in millions)
Outstanding as of January 1, 2024	6,213,853	$	136.60
Granted	534,277	235.78
Exercised	(327,267)	128.92
Forfeited	—	—
Outstanding as of March 31, 2024	6,420,863	$	145.24	4.0	$	545.9
Exercisable as of March 31, 2024	5,427,581	$	130.19	2.9	$	540.5
Unvested as of March 31, 2024	993,282	$	227.50	9.5	$	5.4

The weighted average fair value of a stock option granted during each of the three-month periods ended March 31, 2024 and March 31, 2023 was $97.18 and $85.52, respectively. These stock options have an aggregate grant date fair value of $51.9 million and $36.3 million, respectively. The total grant date fair value of stock options that vested during the three-month periods ended March 31, 2024 and March 31, 2023 was $0.9 million and $52.9 million, respectively.


	Three Months Ended March 31,
		2024		2023
Cost of sales		$	—	$	—
Research and development		0.1		0.1
Selling, general, and administrative		5.6		4.8
Share-based compensation expense before taxes		5.7		4.9
Related income tax benefit		(0.2)		(0.2)
Share-based compensation expense, net of taxes		$	5.5	$	4.7

As of March 31, 2024, unrecognized compensation cost related to stock options was $75.9 million. Unvested outstanding stock options as of March 31, 2024 had a weighted average remaining vesting period of 2.6 years.

Each RSU entitles the recipient to one share of our common stock upon vesting. We measure the fair value of RSUs using the stock price on the date of grant. Share-based compensation expense for RSUs is recorded ratably over their vesting period.

During the three months ended March 31, 2024 and 2023, in addition to time-based RSUs, we granted 0.2 million and 0.2 million performance-based RSUs with a total grant date fair value of $47.5 million and $32.2 million, respectively, calculated based on the assumed achievement of maximum performance of the relevant financial and non-financial performance conditions. During the three months ended March 31, 2024 and 2023, we recorded $2.1 million and $0.2 million, respectively, of share-based compensation expense related to performance-based RSUs, calculated based on the assumed levels of performance achievement.


	Number of RSUs	Weighted Average Grant Date Fair Value
Unvested as of January 1, 2024	964,759	$	210.35
Granted	391,725	235.18
Vested	(139,219)	186.49
Forfeited	(4,882)	208.45
Unvested as of March 31, 2024	1,212,383	$	221.12


	Three Months Ended March 31,
		2024		2023
Cost of sales		$	0.9	$	1.0
Research and development		5.6		4.7
Selling, general, and administrative		9.0		6.5
Share-based compensation expense before taxes		15.5		12.2
Related income tax benefit		(3.3)		(2.9)
Share-based compensation expense, net of taxes		$	12.2	$	9.3

As of March 31, 2024, unrecognized compensation cost related to the grant of RSUs was $204.7 million. Unvested outstanding RSUs as of March 31, 2024 had a weighted average remaining vesting period of 2.9 years.

STAP awards convey the right to receive in cash an amount equal to the appreciation of our common stock, which is measured as the increase in the closing price of our common stock between the dates of grant and exercise. STAP awards expire on the tenth anniversary of the grant date, and in most cases, they vest in equal increments on each anniversary of the grant date over a four-year period. We discontinued the issuance of STAP awards in June 2015.

The aggregate liability balance associated with outstanding STAP awards was $29.2 million and $35.4 million as of March 31, 2024 and December 31, 2023, respectively, all of which was classified as a current liability in our consolidated balance sheets.

Estimating the fair value of STAP awards requires the use of certain inputs that can materially impact the determination of fair value and the amount of compensation expense we recognize. Inputs used in estimating fair value include the price of our common stock, the expected volatility of the price of our common stock, the risk-free interest rate, the expected term of STAP awards, and the expected dividend yield. The fair value of the STAP awards is measured at the end of each financial reporting period because the awards are settled in cash.

The closing price of our common stock was $229.72 and $223.96 on March 31, 2024 and March 31, 2023, respectively. The closing price of our common stock was $219.89 on December 31, 2023.


	Number of Awards	Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (in Years)	Aggregate Intrinsic Value (in millions)
Outstanding as of January 1, 2024	443,058	$	149.21
Granted	—	—
Exercised	(75,764)	103.15
Forfeited	—	—
Outstanding as of March 31, 2024	367,294	$	158.71	0.9	$	26.1
Exercisable as of March 31, 2024	367,294	$	158.71	0.9	$	26.1
Unvested as of March 31, 2024	—	$	—	—	$	—


	Three Months Ended March 31,
		2024		2023
Cost of sales		$	0.2	$	(1.4)
Research and development		0.5		(3.7)
Selling, general, and administrative		3.2		(24.9)
Share-based compensation expense (benefit) before taxes		3.9		(30.0)
Related income tax (benefit) expense		(0.8)		5.2
Share-based compensation expense (benefit), net of taxes		$	3.1	$	(24.8)

The ESPP provides eligible employees with the right to purchase shares of our common stock at a discount through elective accumulated payroll deductions at the end of each offering period. Eligible employees may contribute up to 15 percent of their base salary, subject to certain annual limitations as defined in the ESPP. The purchase price of the shares is equal to the lower of 85 percent of the closing price of our common stock on either the first or last trading day of a given offering period. In addition, the ESPP provides that no eligible employee may purchase more than 4,000 shares during any offering period. The ESPP expires in June 2032 and limits the aggregate number of shares that can be issued under the ESPP to 3.0 million.