Alto Neuroscience Inc. (NYSE: ANRO) highlighted a Nature Medicine publication showing pramipexole significantly reduced anhedonia in patients with mood disorders compared to placebo in an independent study conducted by Lund University researchers.

The PRIME-PRAXOL trial included adults with elevated anhedonia symptoms diagnosed with major depressive disorder, dysthymia, or bipolar depression. Participants received either flexible-dose pramipexole or placebo added to ongoing treatment for nine weeks, followed by a six-month open-label extension.

The study met its primary endpoint, with pramipexole reducing anhedonia more than placebo on the Snaith-Hamilton Pleasure Scale (mean difference -4.04; p=0.006; Hedges' g=0.62). Significant improvements were also observed on independent measures of anhedonia and apathy, with benefits maintained through the six-month open-label period.

A post-hoc analysis found that patients with major depressive disorder, compared to those with dysthymia, showed greater improvement. The MDD subgroup demonstrated an effect size of Hedges' g=0.99 on the primary anhedonia measure.

Common adverse events in the pramipexole group included nausea in approximately 60% of participants, along with sleep disturbance, dizziness, fatigue, and anxiety, despite slow dose escalation.

Alto's experimental drug ALTO-207 combines pramipexole with ondansetron, an anti-nausea medication, designed to reduce tolerability issues that limit pramipexole use. The company is conducting a Phase 2b trial in treatment-resistant depression with results expected in the second half of 2027.

The findings were based on an independent study funded by Lund University investigators, according to the company's statement.