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ALTO-300

Phase 2

Major Depressive Disorder | Small molecule | Psychiatry |Alto Neuroscience, Inc.|Last Updated: Jul 24, 2025

Success Probability

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Market & Valuation

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Trial Design

RandomizedDouble-BlindPLACEBO_CONTROLLED
Total Trials3
Total Enrollment560

FDA Designations

No designations recorded

Clinical trial landscape

ALTO-300 · 3 trials · 1 indication

Phase 2 3
NCT05922878Study of ALTO-300 in MDDMajor Depressive Disorder
RECRUITING321 Analytics
NCT05157945ALTO-300 in Depression (ALTO-300-004)Major Depressive Disorder
COMPLETED148 Analytics
NCT05118750ALTO-300 in DepressionMajor Depressive Disorder
COMPLETED91 Analytics
PHASE2RECRUITING
Study of ALTO-300 in MDD
Major Depressive DisorderUnlock trial analytics
PHASE2COMPLETED
ALTO-300 in Depression (ALTO-300-004)
Major Depressive DisorderUnlock trial analytics
PHASE2COMPLETED
ALTO-300 in Depression
Major Depressive DisorderUnlock trial analytics

Study Endpoints

Primary Endpoints

To assess efficacy of adjunctive ALTO-300 versus placebo on symptoms of MDD in a pre-defined subgroup of participants as measured by the change over time up to week 6 in the Montgomery-Åsberg Depression Rating Scale (MADRS).
Change over time for up to week 6

MADRS is a clinician-administered scale designed to measure depression severity and detects changes due to antidepressant treatment. The MADRS evaluates the following 10 items: apparent sadness, reported sadness, inner tension, reduced sleep, reduced appetite, concentration difficulties, lassitude, inability to feel, pessimistic thoughts, and suicidal thoughts. Each item is scored from 0 (item not present or normal) to 6 (severe or continuous presence of the symptoms), for a total possible score of 60. Higher scores represent a more severe condition.

To understand the relationship between baseline biology and change in the Montgomery-Asberg Depression Rating Scale (MADRS) with ALTO-300
Measured 6 times over 8 weeks

The Montgomery-Åsberg Depression Rating Scale (MADRS) measures the severity of depression where smaller scores indicate less depression and higher scores suggest more severe depression. Possible scores for this 10 item version range from 0 to 60. The change from baseline to the end of the study is the primary outcome.

To understand the relationship between baseline biology and change in the Clinical Global Impression scale - Severity (CGI-S) with ALTO-300
Measured 6 times over 8 weeks

The Clinical Global Impression scale - Severity (CGI-S) measures the severity of psychopathology in general where smaller scores indicate less illness and higher scores suggest more severe illness. Possible scores for this scale range from 1 to 7. The change from baseline to the end of the study is the primary outcome.

Number of Participants with Adverse Events (AEs) as a Measure of Safety and Tolerability of ALTO-300
From the signing of the ICF until the follow-up visit (up to 12 weeks)

An adverse event is any untoward medical event that occurs in a participant administered an investigational product, and it does not necessarily indicate only events with clear causal relationship with the relevant investigational product.

Number of Participants With Clinically Significant Vital Signs Abnormalities as a Measure of Safety and Tolerability of ALTO-300
From the signing of the ICF until the end-of-treatment visit (up to 11 weeks)]

Vital signs measured include blood pressure, heart rate, respiratory rate, temperature, and weight.

Number of Participants With Clinically Significant Laboratory Abnormalities as a Measure of Safety and Tolerability of ALTO-300
From the signing of the ICF until the end-of-treatment visit (up to 11 weeks)]

Blood samples for serum chemistry and hematology will be collected for clinical laboratory testing.

To understand the relationship between baseline biology and clinical outcome to ALTO-300 using the Montgomery-Åsberg Depression Rating Scale (MADRS)
Measured 6 times over 8 weeks

The Montgomery-Åsberg Depression Rating Scale (MADRS) measures the severity of depression where smaller scores indicate less depression and higher scores suggest more severe depression. Possible scores for this 10 item version range from 0 to 60. The change from baseline to the end of the study is the primary outcome.

To understand the relationship between baseline biology and clinical outcome to ALTO-300 using the Clinical Global Impression scale - Severity (CGI-S)
Measured 6 times over 8 weeks

The Clinical Global Impression scale - Severity (CGI-S) measures the severity of psychopathology in general where smaller scores indicate less illness and higher scores suggest more severe illness. Possible scores for this scale range from 1 to 7. The change from baseline to the end of the study is the primary outcome.

To evaluate the safety of ALTO-300
From the signing of the ICF until the follow-up visit (up to 12 weeks)

Incidence, severity, and relatedness of TEAEs,SAEs, discontinuation due to TEAEs, and deaths

Secondary Endpoints

To assess efficacy of adjunctive ALTO-300 versus placebo on symptoms of MDD in all randomized participants as measured by the change over time up to week 6 in the Montgomery-Åsberg Depression Rating Scale (MADRS)
Change over time for up to week 6
To assess efficacy of adjunctive ALTO-300 versus placebo for MDD as measured by the change over time up to week 6 in response (>50% improvement from baseline) rates based on the MADRS
Change over time for up to week 6
To evaluate the safety of ALTO-300 during both the OL and DB periods of the study as measured by the assessment of the incidence, severity, and relatedness of Adverse Events.
Assessed from Day 1 to Week 14
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Study Design & Arms

AllocationRANDOMIZED
MaskingQUADRUPLE
ModelPARALLEL
PurposeTREATMENT

Treatment Arms

ArmTypeDescription
ALTO-300EXPERIMENTALParticipants will receive ALTO-300 capsule once daily in the evening, from Day 1 to Day 42 in double blind (DB) treatment period. Eligible participants who will enter the open-label (OL) treatment period will receive ALTO-300 capsule once daily in the evening from OL baseline until the end of OL period/early termination visit (Up to 8 weeks).
PlaceboPLACEBO_COMPARATORParticipants will receive matching placebo capsule once daily in the evening, from Day 1 to Day 42 in double blind (DB) treatment period.

Interventions

NameTypeDescription
ALTO-300DRUGALTO-300 capsule QD
PlaceboDRUGPlacebo capsule QD
ALTO-300 PO TabletDRUGOne tablet daily
ALTO-300 oral (PO) tabletDRUGOne tablet daily
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Eligibility Criteria

Age Range18 Years to 70 Years
SexALL
Healthy VolunteersNo
Study Sites45

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 ...

Countries:United States
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Frequently asked questions about ALTO-300

What is ALTO-300 used for?

ALTO-300 is an investigational small molecule being developed for the treatment of Major Depressive Disorder (MDD). It is currently in Phase 2 clinical development and has not been approved by the FDA. The drug is being studied in adult patients aged 18 years and older in the United States.

Who makes ALTO-300?

ALTO-300 is being developed by Alto Neuroscience, Inc., a biopharmaceutical company traded on the stock exchange under the ticker symbol ANRO. The company is conducting clinical trials to evaluate the drug's safety and efficacy in patients with Major Depressive Disorder.

What phase is ALTO-300 in?

ALTO-300 is currently in Phase 2 clinical development. It is an investigational drug and has not received FDA approval. The drug is being studied in multiple Phase 2 trials for Major Depressive Disorder, with one trial currently recruiting participants and two trials already completed.

What clinical trials is ALTO-300 in?

ALTO-300 has been studied in three clinical trials for Major Depressive Disorder. Two trials, NCT05118750 and NCT05157945, have been completed, while one trial, NCT05922878, is currently recruiting. All trials are Phase 2, randomized, double-blind, and placebo-controlled, with a total enrollment of 560 participants.

Is ALTO-300 FDA approved?

No, ALTO-300 is not FDA approved. It is an investigational drug currently in Phase 2 clinical development for Major Depressive Disorder. The drug has not yet completed the clinical trials necessary to establish its safety and efficacy for regulatory approval.

How does ALTO-300 work?

ALTO-300 is a small molecule being developed for Major Depressive Disorder. Its specific molecular target has not been disclosed in the available information, so its mechanism of action is not fully described. The drug is being evaluated in clinical trials to determine its effectiveness in treating depression.