Alto Neuroscience has begun a Phase 2b, randomized, placebo‑controlled study of its fixed‑dose combination drug ALTO‑207 in patients with treatment‑resistant depression (TRD). The trial will enroll 178 adults who have failed two to five prior antidepressant regimens and will run for eight weeks, with the primary endpoint being change from baseline in the Montgomery‑Åsberg Depression Rating Scale (MADRS).
The study design mirrors the PAX‑D trial that first demonstrated a large effect size for pramipexole augmentation in TRD. It incorporates a modified‑release formulation of pramipexole with ondansetron to mitigate nausea and allow higher dosing, targeting a daily dose of 3.2 mg pramipexole and 15 mg ondansetron. Management described the Phase 2b as “like a registrational trial,” positioning the program to potentially skip a full Phase 3 and pursue a 505(b)(2) approval pathway.
ALTO‑207 is the cornerstone of Alto’s pipeline; its success will validate the company’s precision psychiatry platform and drive future revenue. The drug was acquired from Chase Therapeutics in June 2025, and a method‑of‑treatment patent was issued in January 2026, protecting the formulation through the mid‑2040s. Alto also has other programs—ALTO‑100, ALTO‑101, and ALTO‑300—at various development stages.
Treatment‑resistant depression affects roughly 7 million adults in the United States, and current therapies often have limited efficacy and tolerability. ALTO‑207 aims to improve efficacy while reducing nausea, potentially capturing a sizable unmet market and offering a differentiated treatment option.
Alto reported $177 million in cash as of December 31, 2025, providing a runway through 2028 to fund the trial and subsequent studies. The company’s precision psychiatry platform underpins multiple programs, reinforcing its strategic focus on data‑driven therapeutics.
"We are excited to be initiating this Phase 2b trial, which builds on one of the strongest efficacy signals observed in treatment‑resistant depression. ALTO‑207 is uniquely designed to build on the robust efficacy demonstrated with pramipexole while addressing the significant tolerability drawbacks that limit its use in clinical practice today. This study is designed like a registrational trial, and we believe it positions us to advance ALTO‑207 efficiently," said Amit Etkin, M.D., Ph.D., founder and chief executive officer of Alto Neuroscience.
"The successful outcome of our recent FDA meeting for ALTO‑207 was a critical step forward, and the financing we announced provides us with the resources to expedite its path toward pivotal studies and potential future approval. We believe we are well‑positioned to advance ALTO‑207 for the many patients who are not adequately served by current therapies," added Etkin.
Topline data from the Phase 2b trial are expected in the second half of 2027. A positive read could accelerate regulatory approval and unlock revenue streams, while a negative result would represent a significant setback for the company’s pipeline.
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