Material Agreement (Form 8-K)

On July 13, 2026, Alto Neuroscience, Inc. (the "Company") entered into an underwriting agreement (the "Underwriting Agreement") with BofA Securities, Inc., as representative of the several underwriters set forth therein (collectively, the "Underwriters"), to issue and sell 3,776,436 shares of common stock of the Company, par value $0.0001 per share ("Common Stock"), in an underwritten registered direct offering (the "Offering") pursuant to an effective shelf registration statement on Form S-3 (File No. 333-284667) (the "Registration Statement") and a related prospectus and prospectus supplement, in each case filed with the Securities and Exchange Commission (the "SEC"). The offering price is $26.48 per share of Common Stock. The Company estimates that the net proceeds from the Offering will be approximately $93.9 million, after deducting underwriting discounts and commissions and estimated offering expenses. In addition, the Underwriters have agreed to reimburse the Company for certain expenses in connection with the Offering. The closing of the Offering is expected to occur on July 14, 2026, subject to customary closing conditions.

The Company currently intends to use the net proceeds from the Offering, together with its current cash and cash equivalents, to accelerate and expand the clinical development of ALTO-207, including to conduct an additional planned Phase 3 trial of ALTO-207 as monotherapy for the treatment of treatment-resistant depression, and for general working capital purposes.

BofA Securities, Inc., Stifel, Nicolaus & Company, Incorporated, William Blair & Company, L.L.C., and Robert W. Baird & Co. Incorporated are acting as the joint book-running managers for the Offering. JonesTrading Institutional Services LLC and H.C. Wainwright & CO., LLC are acting as co-managers for the Offering.

The Underwriting Agreement contains customary representations, warranties, covenants and agreements by the Company, indemnification obligations of the Company and the Underwriters, including for liabilities under the Securities Act of 1933, as amended, other obligations of the parties and termination provisions. The representations, warranties and covenants contained in the Underwriting Agreement were made only for purposes of such agreement and as of specific dates, were solely for the benefit of the parties to such agreement and may be subject to limitations agreed upon by the contracting parties.

A copy of the Underwriting Agreement is filed as Exhibit 1.1 to this Current Report on Form 8-K and is incorporated herein by reference. The foregoing description of the Underwriting Agreement is qualified in its entirety by reference to such exhibit. A copy of the opinion of Cooley LLP as to the legality of the issuance and sale of the Common Stock in the Offering and related consent is filed as Exhibit 5.1 to this Current Report on Form 8-K.