Stockholders' Equity

12 Months Ended

Dec. 31, 2023

Equity [Abstract]

Stockholders' Equity

12.Stockholders’ Equity

Share Repurchases

In December 2023, the Board authorized and approved a stock repurchase of up to $25.0 million of the Company's common stock concurrent with the issuance of $600.0 million aggregate principal amount of its 2023 Notes. See Note 14, “Convertible Senior Notes,” for more information on the issuance. The Company used $14.4 million of the proceeds from the issuance of the 2023 Notes to repurchase 92,090 shares at a price of $156.22, including transaction costs, to offset the impact of dilution from the issuance of 2023 Notes and equity compensation programs as well as to reduce its outstanding share count. The Company has elected to retire the shares repurchased to date. Retired shares become part of the pool of authorized but unissued shares. The purchase price of the retired shares in excess of par value, including transaction costs, is recorded as a decrease to additional paid-in capital in the Company's consolidated balance sheets as of December 31, 2023.

Stock Option and Incentive Plans

At the Company’s 2018 Annual Meeting of Stockholders held on May 16, 2018, the Company’s shareholders approved the 2018 Stock Option and Incentive Plan (the “2018 Plan”). Under the 2018 Plan the number of shares of the Company’s common stock that are reserved and available for issuance shall be 2,778,000 plus the number of shares of common stock available for issuance under the Company’s Amended and Restated 2012 Stock Option and Incentive Plan (the “2012 Plan”). The shares of common stock underlying any awards under the 2018 Plan and 2012 Plan that are forfeited, canceled or otherwise terminated (other than by exercise) shall be added back to the shares of stock available for issuance under the 2018 Plan. At December 31, 2023, 1,671,408 shares were available for future grants under the 2018 Plan.

Stock Issued for Earnout Payment

In May 2023, the Company issued 42,621 shares of its common stock to former securityholders of Avitide to satisfy the contingent consideration obligation established under the Agreement and Plan of Merger and Reorganization (the “Avitide Agreement”) which the Company entered into as part of the Avitide Acquisition. See Note 4, “Acquisitions” above for additional information on the Avitide Acquisition and the contingent consideration. The shares represent 50% of the earnout consideration earned in the First Earnout Year (as defined in the Avitide Agreement).

Stock-Based Compensation

The Company recorded stock-based compensation expense of $25.6 million, $27.3 million and $27.5 million for the years ended December 31, 2023, 2022 and 2021, respectively, for share-based awards granted under the Plans. The following table presents stock-based compensation expense in the Company’s consolidated statements of comprehensive income:

	For the Years Ended December 31,
	2023		2022		2021
	(Amounts in thousands)
Cost of product revenue	$	1,933	$	2,525	$	2,021
Research and development		2,855		2,622		2,856
Selling, general and administrative		20,787		22,169		22,623
Total stock-based compensation	$	25,575	$	27,316	$	27,500

Stock Options

The Company uses the Black-Scholes option pricing model to calculate the fair value of stock option awards on the grant date, and measures stock-based compensation costs of stock options at the grant date based on the estimated fair value of the award. The Company recognizes expense on awards with service-based vesting over the employee’s requisite service period on a straight-line basis. The Company recognizes stock-based compensation expense for options that are ultimately expected to vest, and accordingly, such compensation expense has been adjusted for estimated forfeitures.

The fair value of stock option awards granted during the years ended December 31, 2023, 2022 and 2021 were calculated using the following estimated assumptions:

	For the Years Ended December 31,
	2023	2022	2021
Expected term (in years)	5.14-6.5	5.5-6.5	5.5-6.5
Expected volatility (range)	44.78-46.58%	41.44-43.96%	44.57-45.27%
Risk-free interest rate	3.56-4.71%	1.86-4.07%	0.77-1.07%
Expected dividend yield	0%	0%	0%

Information regarding option activity for the year ended December 31, 2023, under the Plans is summarized below:

	Shares			Weighted average exercise price		Weighted- Average Remaining Contractual Term (in Years)		Aggregate Intrinsic Value (in Thousands)
Options outstanding at December 31, 2022		609,965		$	71.74
Granted		90,305		$	168.22
Exercised		(40,211	)	$	26.76
Forfeited/expired/cancelled		(10,929	)	$	189.46
Options outstanding at December 31, 2023		649,130		$	85.97
Options exercisable at December 31, 2023		364,443		$	65.53
Vested and expected to vest at December 31, 2023(1)		635,834		$	85.49		5.59	$	61,888

(1)Represents the number of vested options as of December 31, 2023 plus the number of unvested options expected to vest as of December 31, 2023, based on the unvested outstanding options at December 31, 2023 adjusted for estimated forfeiture rates of 8% for awards granted to non-executive level employees and 3% for awards granted to executive level employees.

The aggregate intrinsic value in the table above represents the total pre-tax intrinsic value (the difference between the closing price of the common stock on December 29, 2023, the last business day of 2023, of $179.80 per share and the exercise price of each in-the-money option) that would have been received by the option holders had all option holders exercised their options on

December 31, 2023. The aggregate intrinsic value of stock options exercised during the years ended December 31, 2023, 2022 and 2021 was $5.8 million, $14.1 million and $20.3 million, respectively.

The weighted average grant date fair value of options granted during the years ended December 31, 2023, 2022 and 2021 was $84.37, $87.40 and $88.01, respectively. The total fair value of stock options that vested during the years ended December 31, 2023, 2022 and 2021 was $4.7 million, $3.1 million and $3.0 million, respectively.

Stock Units

The fair value of stock units is calculated using the closing price of the Company’s common stock on the date of grant. The Company recognizes expense on awards with service-based vesting over the employee's requisite service period on a straight-line basis. The Company recognizes expense on performance-based awards over the vesting period based on the probability that the performance metrics will be achieved. Information regarding stock unit activity, which includes activity for restricted stock units and performance stock units, for the year ended December 31, 2023 under the Plans is summarized below:

	Shares			Weighted Average Grant Date Fair Value
Unvested at December 31, 2022		531,034		$	142.57
Awarded		212,338		$	170.03
Vested		(195,672	)	$	124.58
Forfeited/cancelled		(73,380	)	$	177.81
Unvested at December 31, 2023		474,320		$	155.59
Vested and expected to vest at December 31, 2023(1)		413,249		$	152.74

(1)Represents the number of vested stock units as of December 31, 2023, plus the number of unvested stock units expected to vest as of December 31, 2023, based on the unvested outstanding stock units at December 31, 2023 adjusted for estimated forfeiture rates of 8% for awards granted to non-executive level employees and 3% for awards granted to executive level employees.

The aggregate intrinsic value of stock units vested during the years ended December 31, 2023, 2022 and 2021 was $35.7 million, $43.9 million and $46.5 million, respectively. The total fair value of stock units that vested during the years ended December 31, 2023, 2022 and 2021 was $26.2 million, $22.7 million and $13.9 million, respectively.

As of December 31, 2023, there was $63.8 million of total unrecognized compensation cost related to unvested share-based awards. This cost is expected to be recognized over a weighted average remaining requisite service period of 2.84 years. The Company expects 2,185,873 unvested options and stock units to vest over the next five years.