Definium Therapeutics, Inc. ("Definium" or the "Company"), a late-stage clinical biopharmaceutical company developing a new generation of therapeutics intended to address underlying causes of psychiatric and neurological disorders, today announced the issuance of inducement grants to three newly hired non-executive employees consisting of options to purchase an aggregate of 56,650 common shares of the Company (the "Options") with effective grant dates of September 14, 2026. The Options have an exercise price equal to the closing price of Definium’s common shares on the date of the grants, and will vest over a four-year period with 25% vesting on the first anniversary of the date of the grant and the remaining 75% vesting in substantially equal monthly increments over the three-year period thereafter, subject to each employee’s continued employment.

The Options were granted as a material inducement to each employee’s employment and were approved by Definium's Compensation Committee on September 11, 2026, in accordance with Rule 5635(c)(4) of The NASDAQ Stock Market LLC. The Options were granted pursuant to Definium’s 2026 Inducement Plan.

About Definium Therapeutics

The mission of Definium Therapeutics is to forge a new era of psychiatry by applying scientific rigor to psychedelics, with the goal of developing accessible treatments that unlock healing at scale. Guided by a recognition that patients deserve more than better, Definium is relentlessly advancing a new generation of therapeutics intended to address underlying causes of psychiatric and neurological disorders. By turning evidence into impact, Definium aims to change the trajectory of today’s mental health care crisis and enable a healthier future. Headquartered in New York, Definium Therapeutics trades on Nasdaq under the symbol DFTX.

For more information, visit https://definiumtx.com/ and follow Definium Therapeutics on Instagram, LinkedIn and X.

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Investors:

Gitanjali Jain

VP, Head of Investor Relations

ir@definiumtx.com

Media:

media@definiumtx.com