Stock-based compensation

3 Months Ended

Jun. 30, 2026

Share-Based Payment Arrangement [Abstract]

Stock-based compensation expense

Stock-based compensation expense was classified in the consolidated statements of operations as follows:


	Three Months Ended June 30,
	2026		2025
Research and development	$	3,615	$	4,689
Selling, general and administrative	4,059		4,073
	$	7,674	$	8,762

The following table summarizes stock-based compensation expense by award type for the three months ended June 30, 2026 and 2025:


	Three Months Ended June 30,
	2026		2025
Stock options	$	3,460	$	4,137
Restricted and performance stock units	4,214		4,625
	$	7,674	$	8,762

2018 Omnibus Incentive Compensation Plan

On July 9, 2018, the Company’s board of directors adopted, and the Company’s stockholders approved the 2018 Omnibus Incentive Compensation Plan (the “2018 Plan”), which became effective immediately prior to the effectiveness of the registration statement filed in connection with the Company’s initial public offering. The 2018 Plan provides for the issuance of incentive stock options, non-qualified stock options, stock awards, stock units, stock appreciation rights and other stock-based awards. The number of shares of common stock initially reserved for issuance under the 2018 Plan is 3,617,968 shares. If any options or stock appreciation rights, including outstanding options and stock appreciation rights granted under the 2017 Plan (up to 2,520,247 shares), terminate, expire, or are canceled, forfeited, exchanged, or surrendered without having been exercised, or if any stock awards, stock units or other stock-based awards, including outstanding awards granted under the 2017 Plan, are forfeited, terminated, or otherwise not paid in full in shares of common stock, the shares of the Company’s common stock subject to such grants will be available for purposes of the 2018 Plan. The number of shares reserved for issuance under the 2018 Plan will increase automatically on the first day of each April equal to 4.0% of the total number of shares of common stock outstanding on the last trading day in the immediately preceding fiscal year, which includes for these purposes, the 14,058,153 shares issuable upon exercise of those pre-funded warrants as of March 31, 2026, as described in Note 9 to these condensed consolidated financial statements, or such lesser amount as determined by the Board. On April 1, 2026, the number of shares reserved for issuance under the 2018 Plan automatically increased by 3,871,003 shares pursuant to the terms of the 2018 Plan and based on total number of shares of common stock outstanding on March 31, 2026. As of June 30, 2026, 3,696,006 shares remained available for future grants under the 2018 Plan.

The 2018 Plan is administered by the board of directors or, at the discretion of the board of directors, by a committee of the board of directors. However, the board of directors shall administer and approve all grants made to non-employee directors. The exercise prices, vesting and other restrictions are determined at the discretion of the board of directors, except that the exercise price per share of incentive stock options may not be less than 100% of the fair market value of the common stock on the date of grant (or 110% of fair value in the case of an award granted to employees who hold more than 10% of the total combined voting power of all classes of stock at the time of grant) and the term of stock options may not be greater than five years for an incentive stock option granted to a 10% stockholder and greater than ten years for all other options granted. Stock options awarded under both plans expire ten years after the grant date, unless the board of directors sets a shorter term. Vesting periods for the plan is determined at the discretion of the board of directors. Incentive stock options granted to employees and non-statutory options granted to employees, officers, members of the board of directors, advisors, and consultants of the Company typically vest over four years. In 2021 the board of directors initiated the award of restricted stock units ("RSUs"), under the 2018 Plan in addition to stock option awards available as part of the Company's equity incentive for employees, officers, advisors and consultants of the Company. The RSUs typically vest over four approximately equal annual installments with the first such installment occurring on a designated vesting date that is approximately on the one-year anniversary of the date of grant and the subsequent installments occurring on the subsequent three annual anniversaries of the designated vesting date.

In 2024, the Company's board of directors approved the award of performance stock units ("PSUs"), under the 2018 Plan in addition to the aforementioned stock option awards and RSUs available as part of the Company’s equity incentive for employees, officers, advisors and consultants of the Company, subject to non-market performance and service conditions. The grant date fair value for the PSUs is determined based on the market price of the Company's common stock on the grant date and expense is recognized over the requisite service period if and when the achievement of such performance condition is determined to be probable by the Company. On June 30, 2026, the compensation committee of the board of directors agreed to extend the performance period with respect to the “Target” performance level set forth in the PSU Award Agreement to end on December 24, 2026. Accordingly, the PSUs will vest at 100% given the approval of the Company's first Biologics License Application ("BLA") for TUDRIQEV by the Food and Drug Administration ("FDA"). The timing of recognition of this stock-based compensation expense is subject to our judgment as to when the performance conditions are considered probable of being

achieved. The Company did not grant any PSUs under the 2018 Plan during the three months ended June 30, 2026 or 2025. The Company reassesses the probability of achieving the performance condition at each reporting period. As of June 30, 2026, the Company has not recognized any expense related to PSUs.

Employee Stock Purchase Plan

On July 9, 2018, the Company’s board of directors adopted and the Company’s stockholders approved the Employee Stock Purchase Plan (the “ESPP”), which became effective immediately prior to the effectiveness of the registration statement that was filed in connection with the Company’s IPO. The total shares of common stock initially reserved for issuance under the ESPP is 348,612 shares. In addition, as of the first trading day of each fiscal year during the term of the ESPP (excluding any extensions), an additional number of shares of the Company’s common stock equal to 1% of the total number of shares outstanding on the last trading day in the immediately preceding fiscal year, which includes for these purposes, the 14,058,153 shares issuable upon exercise of those pre-funded warrants described in Note 9 to these condensed consolidated financial statements, or 697,224 shares, whichever is less (or such lesser amount as determined by the Company’s board of directors) will be added to the number of shares authorized under the ESPP. In accordance with the terms of the ESPP, on April 1, 2026, the number of shares reserved for issuance under the ESPP automatically increased by 697,224, for a total of 4,799,623 shares reserved for the ESPP. If the total number of shares of common stock to be purchased pursuant to outstanding purchase rights on any particular date exceed the number of shares then available for issuance under the ESPP, then the plan administrator will allocate the available shares pro-rata and refund any excess payroll deductions or other contributions to participants. The Company’s ESPP is not currently active.

Out-of-Plan Inducement Grants

From time to time, the Company grants equity awards to newly hired employees and executives as a material inducement to enter into employment with the Company. The grants constitute "employment inducement grants" in accordance with Rule 5635(c)(4) of the Nasdaq Listing Rules and have been issued outside of the 2018 Plan and each of the other stock incentive plans described above. The inducement grants typically include nonqualified stock options to purchase shares of the Company's common stock, as well as restricted stock unit grants representing shares of the Company's common stock. These stock option and restricted stock unit inducement grants have terms and conditions consistent with those set forth under the 2018 Plan and vest under the same respective vesting schedules as stock option and restricted stock unit awards granted under the 2018 Plan. The inducement grants are included in the stock option and RSU award tables below. The Company did not grant any out-of-plan inducement grants during the three months ended June 30, 2026. During the three months ended June 30, 2025, the Company granted 156,895 nonqualified stock options to purchase shares of the Company's common stock, and 240,960 restricted stock units under employment inducement grants.

Stock option valuation

The fair value of stock option grants is estimated using the Black-Scholes option-pricing model, which requires inputs based on certain subjective assumptions including the expected stock price volatility, the expected term of the option, the risk-free interest rate determined by reference to the U.S Treasury yield curve in effect at the time of grant of the award for a period that approximates the expected term of the option, and our expected dividend yield. The expected term of stock options granted to non-employees is equal to the contractual term of the option award. Expected dividend yield is based on the fact that the Company has never paid cash dividends and does not expect to pay any cash dividends in the foreseeable future. For options with service-based vesting conditions, the expected term of the Company’s stock options has been determined utilizing the “simplified” method for awards that qualify as “plain-vanilla” options.

Forfeitures are accounted for as they occur.

The following table presents, on a weighted-average basis, the assumptions that the Company used to determine the grant-date fair value of stock options granted to employees and directors:


	Three Months Ended June 30,
	2026		2025
Risk-free interest rate	4.06	%	3.97	%
Expected term (in years)	6.0		6.0
Expected volatility	106.7	%	76.3	%
Expected dividend yield	0	%	0	%

Stock options

The following table summarizes the Company’s stock option activity:


	Number of Shares	Weighted Average Exercise Price		Weighted Average Contractual Term (Years)	Aggregate Intrinsic Value
Outstanding as of March 31, 2026	11,785,458	$	14.12	5.63	$	4,323
Granted	2,167,083	7.63
Exercised	(118,075)	8.49
Cancelled	(1,341,594)	14.53
Outstanding as of June 30, 2026	12,492,872	13.00		5.71	25,470
Options exercisable as of June 30, 2026	8,594,036	14.99		4.23	14,195
Options vested and expected to vest as of June 30, 2026	12,492,872	$	13.00	5.71	$	25,470

As of June 30, 2026, there was $23.4 million of unrecognized compensation cost related to unvested common stock options, which is expected to be recognized over a weighted average period of 2.7 years.

The weighted average grant-date fair value of stock options granted during the three months ended June 30, 2026 and 2025 was $6.33 and $5.80, respectively. The aggregate intrinsic value of stock options exercised during the three months ended June 30, 2026 was $0.2 million and the aggregate intrinsic value of stock options exercised during the three months ended June 30, 2025 was immaterial.

Restricted and performance stock units

A summary of the changes in the Company’s RSUs and PSUs during the three months ended June 30, 2026 is as follows:


	Number of Restricted Shares	Weighted Average Grant Date Fair Value
Outstanding as of March 31, 2026	5,508,882	$	9.69
Granted	2,510,630	7.65
Vested	(1,144,368)	10.47
Cancelled	(2,049,553)	8.79
Outstanding as of June 30, 2026	4,825,591	$	8.82

During the three months ended June 30, 2026 and 2025, the weighted average grant date fair value of awards granted is $19.2 million and $20.1 million, respectively. In addition, the total fair value of shares vested during the three months ended June 30, 2026 and 2025 is $12.0 million and $11.7 million, respectively. As of June 30, 2026, there was $34.1 million of unrecognized compensation cost related to unvested restricted stock units, which is expected to be recognized over a weighted average period of 2.7 years. In addition, unrecognized compensation costs related to performance based awards tied to the achievement of a company milestone account for approximately $3.2 million.