23. Related Party Transactions

atai Formation

In connection with the formation of the Company in 2018, the Company entered into a series of transactions with its shareholders Apeiron Investment Group Ltd. (“Apeiron”), the family office of Christian Angermayer, Co-Founder and Chairman of the Company, among other shareholders, contributed their investments in COMPASS, Innoplexus and Juvenescence Ltd. to the Company in exchange for the Company's common stock of equivalent value. Apeiron is the family office of the Company’s co-founder who owns 15.2% and 20.1% of the outstanding common stock in the Company as of December 31, 2025 and 2024, respectively.

Amended and Restated Consulting Agreement with Mr. Angermayer

In connection with the Redomiciliation Transaction, the Company and Mr. Angermayer entered into an Amended and Restated Consultancy Agreement pursuant to which Mr. Angermayer will continue to provide services to the Company on business and financing matters until January 5, 2028. Mr. Angermayer’s prior consulting agreement with the Company was substantially similar and provided for consideration in the form of options.

In June 2025, the Company granted to Mr. Angermayer in further consideration of his continued service as a consultant and other valuable consideration (i) an option to purchase 337,686 shares of common stock of the Company that will vest with respect to 131,698 shares subject to the option based on the Company’s standard four year vesting schedule and with respect to 205,988 shares subject to the option based on the Company achieving certain asset value goals by December 31, 2026 and continued service with the Company through such date, and (ii) an option to purchase 292,500 shares that will vest based on Company achieving certain asset value goals by December 31, 2026 and continued service with the Company through such date.

For the years ended December 31, 2025 and 2024, the Company recognized $0.9 million and $0.4 million, respectively, of stock-based compensation included in General and administrative expense in its consolidated statements of operations related to Mr. Angermayer’s consulting agreement.

For the years ended December 31, 2025 and 2024, the Company recorded $0.1 million and $0.3 million, respectively, of stock-based compensation included in General and administrative expense in its consolidated statements of operations related to Mr. Angermayer's service as Chairman of the board.

Apeiron's Purchase of Common Stock

As mentioned in Note 15, Stockholders’ Equity, the Company entered into the February Underwriting Agreement in connection with the issuance and sale by the Company in a public offering of its common stock. Apeiron participated in the public offering, purchasing 10,835,718 common stock at a price per share of $2.10. Additionally, in August 2025, the Company sold common shares to certain investors pursuant to the July 2025 Subscription Agreements. Apeiron participated in this offering, purchasing 8,675,799 common shares at a price of $2.19 per share.

Conversion of Convertible Promissory Notes

In September 2025, Apeiron, the related party note holder described in Note 14, Debt, exercised the conversion feature of the New Convertible Notes and converted all of its New Convertible Notes into 2,367,200 common stock.

Beckley Psytech Promissory Note

As mentioned in Note 7, Notes Receivable, the Company issued a Promissory Note to Beckley Psytech in the principal amount of $10.0 million, with net proceeds to be used for the achievement of specified product development milestones. The Promissory Note was settled pursuant to the completion of the Beckley Psytech Acquisition as Beckley Psytech became a wholly owned subsidiary and the Promissory Note became an intercompany transaction that is eliminated in consolidation as of the Acquisition Date.

Amandala Neuro Limited Notes Receivable

As noted above in Note 7, Notes Receivable, upon the acquisition and consolidation of Beckley Psytech in November 2025, the Company recognized $1.5 million of notes receivable from Amandala, in which the Company owns approximately 33.7%.

Consulting Agreement with Mr. Feilding Mellen

Subsequent to the acquisition of Beckley Psytech, the Company appointed Cosmo Feilding Mellen as a Director of the Company and entered into a consulting agreement with him. Pursuant to the consulting agreement with Mr. Feilding Mellen, the Company issued 10,000 stock options that fully vest as of December 31, 2025. For the years ended December 31, 2025, the Company recognized an immaterial amount of stock-based compensation included in General and administrative expense in its consolidated statements of operations related to Mr. Feilding Mellen’s consulting agreement. For the years ended December 31, 2025, the Company recognized $0.1 million of stock-based compensation included in General and administrative expense in its consolidated statements of operations related to Mr. Feilding Mellen’s

service as a board Director. The consulting agreement expired on December 31, 2025 and Mr. Feilding Mellen resigned from the Company’s board effective January 6, 2026.