Asset Purchase and License Agreements	6 Months Ended
Jun. 30, 2026
Business Combination, Asset Acquisition, Transaction between Entities under Common Control, and Joint Venture Formation [Abstract]
Asset Purchase and License Agreements	Asset Purchase and License Agreements From time to time, the Company enters into asset purchase and license agreements with third parties. For a detailed description of the significant agreements with certain financial commitments to which the Company is a party, see Note 10 to the consolidated financial statements included in the Company’s Annual Report. As of June 30, 2026, the Company was a party to the following significant agreement pursuant to which payments were made during the three and six months ended June 30, 2026 and 2025: Chase Asset Purchase Agreement On May 31, 2025 (the “Chase Closing Date”), the Company entered into an Asset Purchase Agreement (“Chase Agreement”) with Chase Therapeutics Corporation (“Chase”) pursuant to which the Company acquired all patent, know-how and other rights to ALTO-207, ALTO-208, and certain related assets (the “Acquired Compounds”). On the Chase Closing Date, the Company made an initial payment of $1.8 million in cash and reimbursed Chase $1.2 million to offset certain expenses incurred by the Seller in connection with the Chase Agreement, which are recorded in research and development expenses in the consolidated statements of operations and comprehensive loss. The Company is obligated to pay Chase up to an aggregate of $71.5 million after the Chase Closing Date (the “Chase Milestone Payments”) upon the achievement of certain clinical, regulatory, and sales milestones related to the Acquired Compounds (the “Chase Milestone Events”). Of the potential Milestone Payments, $41.0 million in aggregate are tied to commercial success of the product candidates. Other than with respect to the first Chase Milestone Event, Chase may elect to receive the Chase Milestone Payments for each Chase Milestone Event either as cash or as restricted shares of the Company’s common stock, subject to an overall limitation of a maximum of 5,387,353 shares of common stock that may be issued pursuant to the Chase Agreement (representing 19.9% of the outstanding shares of the common stock as of the Chase Closing Date). The number of shares of common stock issuable for a Chase Milestone Payment paid in restricted shares of common stock will be determined by dividing the Chase Milestone Payment by the applicable Company Stock Price (as defined below), rounded down to the nearest share. The Company Stock Price is defined as the five-day volume-weighted average price per share of common stock as reported by Bloomberg and calculated during regular trading hours over the five consecutive trading day period ending on: (a) with respect to a Chase Milestone Payment pursuant to Chase’s election to receive a Chase Milestone Payment as common stock, the first trading day immediately following an Achievement Notice (as defined in the Chase Agreement); and (b) with respect a Deadline Milestone Payment (as defined below), the first trading day immediately following the applicable anniversary of the Closing Date. In May 2026, the Company achieved the first Chase Milestone Event, related to the initiation of its Phase 2b clinical trial evaluating ALTO-207 resulting in a cash payment of $2.0 million, which was recorded in research and development expenses during the three and six months ended June 30, 2026. Except for this $2.0 million milestone payment, no additional milestones or royalties were paid or accrued during the three and six months ended June 30, 2026 related to this agreement. The Company must use commercially reasonable efforts to develop, seek Regulatory Approval (as defined in the Chase Agreement) for, and commercialize products containing or comprising the Acquired Compounds in the United States. If the Company fails to achieve certain Chase Milestone Events by an agreed date, the Company must either pre-pay a portion of the relevant Chase Milestone Payment associated with that Chase Milestone Event, (a “Deadline Milestone Payment”), which pre-payment obligation may be paid in restricted shares of Common Stock, or transfer the related Acquired Compound back to Chase, in the Company’s sole discretion.

From time to time, the Company enters into asset purchase and license agreements with third parties. For a detailed description of the significant agreements with certain financial commitments to which the Company is a party, see Note 10 to the consolidated financial statements included in the Company’s Annual Report. As of June 30, 2026, the Company was a party to the following significant agreement pursuant to which payments were made during the three and six months ended June 30, 2026 and 2025:

On May 31, 2025 (the “Chase Closing Date”), the Company entered into an Asset Purchase Agreement (“Chase Agreement”) with Chase Therapeutics Corporation (“Chase”) pursuant to which the Company acquired all patent, know-how and other rights to ALTO-207, ALTO-208, and certain related assets (the “Acquired Compounds”).

On the Chase Closing Date, the Company made an initial payment of $1.8 million in cash and reimbursed Chase $1.2 million to offset certain expenses incurred by the Seller in connection with the Chase Agreement, which are recorded in research and development expenses in the consolidated statements of operations and comprehensive loss. The Company is obligated to pay Chase up to an aggregate of $71.5 million after the Chase Closing Date (the “Chase Milestone Payments”) upon the achievement of certain clinical, regulatory, and sales milestones related to the Acquired Compounds (the “Chase Milestone Events”). Of the potential Milestone Payments, $41.0 million in aggregate are tied to commercial success of the product candidates. Other than with respect to the first Chase Milestone Event, Chase may elect to receive the Chase Milestone Payments for each Chase Milestone Event either as cash or as restricted shares of the Company’s common stock, subject to an overall limitation of a maximum of 5,387,353 shares of common stock that may be issued pursuant to the Chase Agreement (representing 19.9% of the outstanding shares of the common stock as of the Chase Closing Date).

The number of shares of common stock issuable for a Chase Milestone Payment paid in restricted shares of common stock will be determined by dividing the Chase Milestone Payment by the applicable Company Stock Price (as defined below), rounded down to the nearest share. The Company Stock Price is defined as the five-day volume-weighted average price per share of common stock as reported by Bloomberg and calculated during regular trading hours over the five consecutive trading day period ending on: (a) with respect to a Chase Milestone Payment pursuant to Chase’s election to receive a Chase Milestone Payment as common stock, the first trading day immediately following an Achievement Notice (as defined in the Chase Agreement); and (b) with respect a Deadline Milestone Payment (as defined below), the first trading day immediately following the applicable anniversary of the Closing Date.

In May 2026, the Company achieved the first Chase Milestone Event, related to the initiation of its Phase 2b clinical trial evaluating ALTO-207 resulting in a cash payment of $2.0 million, which was recorded in research and development expenses during the three and six months ended June 30, 2026. Except for this $2.0 million milestone payment, no additional milestones or royalties were paid or accrued during the three and six months ended June 30, 2026 related to this agreement.

The Company must use commercially reasonable efforts to develop, seek Regulatory Approval (as defined in the Chase Agreement) for, and commercialize products containing or comprising the Acquired Compounds in the United States. If the Company fails to achieve certain Chase Milestone Events by an agreed date, the Company must either pre-pay a portion of the relevant Chase Milestone Payment associated with that Chase Milestone Event, (a “Deadline Milestone Payment”), which pre-payment obligation may be paid in restricted shares of Common Stock, or transfer the related Acquired Compound back to Chase, in the Company’s sole discretion.