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Evaluating ALTO-300 for treating major depressive disorder

A Randomized, Double-Blind, Placebo-Controlled Study of ALTO-300 With an Open-Label Extension in Adults With Major Depressive Disorder

PHASE2 · Alto Neuroscience · NCT05922878

This study is testing if adding ALTO-300 to standard antidepressants can help people with moderate to severe depression feel better compared to a placebo.

Quick facts

PhasePHASE2
Study typeInterventional
Enrollment321 (estimated)
Ages18 Years to 70 Years
SexAll
SponsorAlto Neuroscience (industry)
Locations45 sites (Phoenix, Arizona and 44 other locations)
Trial IDNCT05922878 on ClinicalTrials.gov

What this trial studies

This study aims to assess the efficacy of ALTO-300 compared to a placebo when used alongside a standard antidepressant in patients diagnosed with moderate to severe major depressive disorder (MDD). Participants must have been on a stable dose of an SSRI, SNRI, or bupropion for at least six weeks prior to enrollment. The study will analyze how patient characteristics influence the treatment outcomes. The trial is designed to provide insights into the potential benefits of ALTO-300 in enhancing depression treatment.

Who should consider this trial

Good fit: Ideal candidates are adults diagnosed with moderate to severe major depressive disorder who are currently stable on a single antidepressant.

Not a fit: Patients with unstable medical conditions, bipolar disorder, or those using sleep medications may not benefit from this study.

Why it matters

Potential benefit: If successful, this treatment could offer a new adjunctive option for patients struggling with major depressive disorder.

How similar studies have performed: While this approach is being explored, similar studies have shown promise in evaluating adjunctive treatments for depression.

Eligibility criteria

Show full inclusion / exclusion criteria 
Inclusion Criteria:

* Have a diagnosis of moderate to severe major depressive disorder (MDD)
* At Visit 1, currently taking a single SSRI, SNRI, or bupropion for at least 6 weeks with no dose modifications in the past 2 weeks by Visit 2
* Willing to comply with all study assessments and procedures
* Must not be pregnant or breastfeeding at time of enrollment or throughout study

Exclusion Criteria:

* Evidence of unstable medical condition
* Nightly use of sleep medication
* Diagnosed bipolar disorder, psychotic disorder, or dementia
* Current moderate or severe substance use disorder
* Has a history of hypersensitivity or allergic reaction to ALTO-300 or any of its components/excipients
* Concurrent or recent participation in another clinical trial for mental illness involving an investigational product or device

Where this trial is running

Phoenix, Arizona and 44 other locations

Study contacts

How to participate

  1. Review the eligibility criteria above with your treating physician.
  2. Visit the official trial page on ClinicalTrials.gov for the most current contact information and recruitment status.
  3. Contact the listed study coordinator or principal investigator to request pre-screening. Pre-screening is free and never obligates you to enroll.

View on ClinicalTrials.gov →

Conditions: Major Depressive Disorder

Last reviewed 2026-05-15 by the Find a Trial editorial team. Information on this page is for educational purposes and is not medical advice. Always consult qualified healthcare professionals about clinical trial participation.