UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d)

of the Securities Exchange Act of 1934

Date of Report (Date of earliest event reported): October 19, 2025

ALTO NEUROSCIENCE, INC.

(Exact Name of Registrant as Specified in its Charter)

Registrant’s telephone number, including area code: (650) 200-0412

N/A

(Former name or former address, if changed since last report.)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

Securities registered pursuant to Section 12(b) of the Act:

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter).

Emerging growth company x

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ¨

Private Placement of Common Stock and Warrants

On October 19, 2025, Alto Neuroscience, Inc. (the “Company”) entered into a Securities Purchase Agreement (the “Purchase Agreement”) with certain institutional and other accredited investors (the “Purchasers”), pursuant to which the Company agreed to sell and issue to the Purchasers in a private placement transaction (the “Private Placement”) (i) 3,832,263 shares (the “Shares”) of the Company’s common stock, par value $0.0001 (“Common Stock”), and (ii) with respect to certain Purchasers, pre-funded warrants to purchase 4,622,251 shares of Common Stock (the “Pre-Funded Warrants”) in lieu of Shares. The purchase price per share of Common Stock is $5.914 per share (the “Purchase Price”) and the purchase price for the Pre-Funded Warrants is the Purchase Price minus $0.0001 per Pre-Funded Warrant. The Company anticipates receiving gross proceeds of approximately $50.0 million from the Private Placement, before deducting offering expenses payable by the Company.

The Pre-Funded Warrants have a per share exercise price of $0.0001, subject to proportional adjustments in the event of stock splits or combinations or similar events. The Pre-Funded Warrants will not expire until exercised in full. The Pre-Funded Warrants may not be exercised if the aggregate number of shares of Common Stock beneficially owned by the holder thereof immediately following such exercise would exceed a specified beneficial ownership limitation; provided, however, that a holder may increase or decrease the beneficial ownership limitation by giving 61 days’ notice to the Company, but not to any percentage in excess of 19.9%.

Under the terms of the Purchase Agreement, the Company has agreed to prepare and file, within 45 days after the Closing (the “Filing Deadline”), one or more registration statements with the Securities and Exchange Commission (the “SEC”) to register for resale the Common Stock issued under the Purchase Agreement and the shares of Common Stock issuable upon exercise of the Pre-Funded Warrants (the “Warrant Shares”) issued pursuant to the Purchase Agreement (together, the “Registrable Securities”), and to cause the applicable registration statements to become effective within a specified period after the Filing Deadline (the “Effectiveness Deadline”).

The Purchase Agreement contains customary representations, warranties and covenants that were made solely for the benefit of the parties to the Purchase Agreement. Such representations, warranties and covenants (i) are intended as a way of allocating risk between the parties to the Purchase Agreement and not as statements of fact, and (ii) may apply standards of materiality in a way that is different from what may be viewed as material by stockholders of, or other investors in, the Company. Accordingly, the Purchase Agreement is included with this filing only to provide investors with information regarding the terms of transaction and not to provide investors with any other factual information regarding the Company.

The Company has granted the Purchasers customary indemnification rights in connection with the registration statement. The Purchasers have also granted the Company customary indemnification rights in connection with the registration statement.

The foregoing is only a summary of the terms of the Purchase Agreement, the Registration Rights Agreement and the Pre-Funded Warrants issued under the Purchase Agreement, does not purport to be complete and is qualified in its entirety by reference to the full text of (i) the form of the Purchase Agreement, a copy of which is attached to this Current Report on Form 8-K as Exhibit 10.1, (ii) the form of the Registration Rights Agreement, a copy of which is attached to this Current Report on Form 8-K at Exhibit 10.2, and (iii) the form of Pre-Funded Warrant issued under the Purchase Agreement, a copy of which is attached to this Current Report on Form 8-K as Exhibit 4.1.

As previously disclosed, on February 3, 2025, the Company entered into a Sales Agreement (the “Sales Agreement”) with Leerink Partners LLC (the “Agent”), pursuant to which the Company from time to time may offer and sell shares of its common stock through or to the Agent having an aggregate offering price of up to $75 million. On October 20, 2025, the Company delivered written notice to the Agent to terminate the Sales Agreement, effective October 30, 2025 in accordance with the terms of the Sales Agreement. The Company had not sold any shares of common stock under the Sales Agreement prior to termination.

The description of the Sales Agreement contained in this Current Report on Form 8-K does not purport to be complete and is qualified in its entirety by reference to the copy of the Sales Agreement filed as Exhibit 10.1 to the Company’s Current Report on Form 8-K filed on February 3, 2025.

The disclosure regarding the securities to be sold and issued under the Purchase Agreement as set forth under Item 1.01 of this report is incorporated by reference under this Item 3.02.

The securities described above under Item 1.01 have not been registered under the Securities Act of 1933, as amended (the “Securities Act”). Based in part upon the representations of the Purchasers in the Purchase Agreement, the Company relied on the exemption afforded by Regulation D under the Securities Act, and corresponding provisions of state securities or “blue sky” laws. Each of the Purchasers has represented that it is an “accredited investor” as defined in Regulation D of the Securities Act and that it is acquiring the securities for investment only and not with a view towards, or for resale in connection with, the public sale or distribution thereof, and appropriate legends will be affixed to the securities. The sale of the securities did not involve a public offering and was made without general solicitation or general advertising.

Neither this Current Report on Form 8-K nor any exhibit attached hereto is an offer to sell or the solicitation of an offer to buy any securities of the Company.

On October 20, 2025, the Company issued a press release entitled “Alto Neuroscience Announces $50 Million Private Placement Financing.” The full text of the press release is attached as Exhibit 99.1 to this Current Report on Form 8-K and is incorporated herein by reference. The Company concurrently issued a press release entitled “Alto Neuroscience Announces Plans to Accelerate Development of ALTO-207 in Treatment Resistant Depression Following Successful Outcome from Recent FDA Meeting.” The full text of the press release is attached as Exhibit 99.2 to this Current Report on Form 8-K and is incorporated herein by reference.

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.