Alto Neuroscience has strengthened its intellectual property position around its lead depression candidate ALTO-207 with the issuance of a new US method-of-treatment patent covering the use of the therapy in patients with depression.

The newly issued patent, US Patent Number 12,521,374, covers methods of treating depression using ALTO-207, a fixed-dose combination of pramipexole and ondansetron. The claims focus on the use of ondansetron to mitigate side effects associated with pramipexole, enabling patients to reach higher dose levels required to achieve antidepressant effects.

According to the company, the new patent adds to an existing portfolio of issued patents and pending applications in the US and other jurisdictions, with protection for ALTO-207 expected to extend into the mid-2040s. Alto said the expanded intellectual property estate supports the long-term development and potential commercialisation of the programme in treatment resistant depression.

ALTO-207 is being developed as a differentiated approach to addressing limitations seen with pramipexole when used alone. Pramipexole, a dopamine D3-preferring D3/D2 agonist approved for Parkinson’s disease, has demonstrated antidepressant effects, but its use at higher doses has historically been constrained by dose-limiting adverse events such as nausea. Ondansetron, a selective 5-HT3 receptor antagonist commonly used as an antiemetic, is included in the fixed-dose combination to reduce these side effects and support more rapid titration.

Amit Etkin, founder and ceo of Alto Neuroscience, said the patent issuance was an important milestone for the programme: “This patent issuance meaningfully strengthens the foundation of our ALTO-207 franchise. Robust and durable intellectual property is critical as we advance precision-based treatments for depression, and this milestone reflects both the novelty of ALTO-207 and our commitment to building long-term value for patients, clinicians, and shareholders.”

He added: “We believe the breadth and duration of our issued and pending claims position ALTO-207 as a potentially enduring asset in the treatment landscape for depression.”

Alto said the latest patent aligns with its broader strategy of building a portfolio of precision-driven neuropsychiatric assets supported by robust intellectual property protection. The company is focused on developing targeted therapies designed to address specific biological drivers of neuropsychiatric disorders, including depression.

ALTO-207 has already generated clinical data in a randomized, placebo-controlled Phase 2a study involving 32 patients with depression. In that trial, the programme met both primary and secondary endpoints, demonstrating statistically significant improvements on the Montgomery–Åsberg Depression Rating Scale compared with placebo. Patients receiving ALTO-207 reached a mean dose of 4.1 mg per day.

The company said ALTO-207 was well tolerated during the maintenance period of the study, with an adverse event rate comparable to placebo. Alto believes these data support continued development of the programme in treatment resistant depression, an area with significant unmet clinical need.

With the issuance of the new US patent, Alto said it is well positioned to continue advancing ALTO-207 through clinical development while maintaining long-term protection for the programme as it moves toward later-stage trials.