Alto Neuroscience, Inc. (NYSE: ANRO) shares fell first thing Tuesday. The company, a clinical-stage biopharmaceutical company focused on precision medicines for neuropsychiatric disorders, today announced the initiation of a Phase 2b randomized, placebo-controlled trial of ALTO-207 in treatment-resistant depression (TRD), a program designed to replicate the strongly positive PAX-D study results and support a streamlined path to registration. TRD is estimated to affect up to seven million adults in the United States, representing patients who do not respond adequately to current antidepressant therapies.
“We are excited to be initiating this Phase 2b trial, which builds on one of the strongest efficacy signals observed in treatment-resistant depression,” said CEO Amit Etkin. “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.”
The Phase 2b trial design is informed by the PAX-D study, a randomized, placebo-controlled trial published in The Lancet Psychiatry (July 2025), which demonstrated a Cohen’s d effect size of 0.87 for pramipexole augmentation in TRD — substantially exceeding the effect sizes observed with currently approved therapies. ALTO-207, a fixed-dose combination of pramipexole and ondansetron, with a novel, modified-release formulation, is designed to mitigate pramipexole-associated nausea, thus enabling improved tolerability, more rapid titration, and higher dosing.
ANRO gave back $1.65, or 6.1%, to $25.60.
