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ALTO-300

Phase 2

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

Success Probability
Approval Probability 71%
TA Base Rate26%
Adjusted LOA41%
ML RiskLOW_RISK
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Market & Valuation
rNPV $3.2B
Market Size $9.4B
Revenue Basis $1.6B
Competitors 6
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Trial Design
RandomizedDouble-BlindPLACEBO_CONTROLLEDBiomarker
Total Trials3
Total Enrollment560
FDA Designations
No designations recorded
Clinical Trials (3)
NCT IDTitlePhaseStatusEnrollmentVelocityDesignStartCompletionLast UpdatedSitesCountries
NCT05922878Study of ALTO-300 in MDDPHASE2 RECRUITING 321Jun 8, 2023Dec 1, 2026Jul 24, 202545 United States
NCT05157945ALTO-300 in Depression (ALTO-300-004)PHASE2 COMPLETED 148Feb 3, 2022May 5, 2023Apr 26, 20244 United States
NCT05118750ALTO-300 in DepressionPHASE2 COMPLETED 91Dec 13, 2021May 9, 2023Apr 30, 202411 United States
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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 — 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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Recent Changes (Last 90 Days)
LOWMay 26, 2026NCT05922878primaryCompletionDate: changed
LOWMay 24, 2026NCT05922878studyFirstPostDate: changed