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ALTO-203 25 μg

Phase 2

Major Depressive Disorder | Small molecule | Psychiatry |Alto Neuroscience, Inc.|Last Updated: Apr 17, 2026

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Trial Design

RandomizedDouble-BlindPLACEBO_CONTROLLED
Total Trials1
Total Enrollment69

FDA Designations

No designations recorded

Clinical trial landscape

ALTO-203 25 μg · 1 trial · 2 indications

Phase 2 1
NCT06391593PD, PK, and Safety of ALTO-203 in Patients With MDDMajor Depressive Disorder
COMPLETED69 Analytics
PHASE2COMPLETED
PD, PK, and Safety of ALTO-203 in Patients With MDD
Major Depressive DisorderUnlock trial analytics

Study Endpoints

Primary Endpoints

Single Dose Period: To evaluate pharmacodynamic measures in patients with MDD after single doses of 25 μg ALTO-203, 75 μg ALTO-203, and placebo as measured by the alertness and mood components of the Bond-Lader Visual Analog Scale (BL-VAS).
Single-Dose Treatment Period - Pre-Dose, 1.5 hours, 3 hours, and 5 hours on Day 1 at Treatments 1, 2, and 3

The Bond-Lader Visual Analogue Scale (BL-VAS) is used to measure the effects of drugs on the participants' mood. It consists of 16 VAS measurements of different mood state. For each question, the participants will rate their feelings at the time of assessment by indicating the point on the 10 cm line which best represents their mood. Each item is scored by measuring the position relative to the left-hand end of the line. The combined domains of alertness and mood will be assessed for the primary endpoint.

Multi-Dose Period: To assess the incidence of Treatment-Emergent Adverse Events [Safety and Tolerability] during the multi-dose treatment period for ALTO-203 25 μg and ALTO-203 75 μg as compared to placebo.
Multi-Dose Treatment Period Day 1 to Day 35

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

Secondary Endpoints

Single Dose Period: To assess the incidence of Treatment-Emergent Adverse Events [Safety and Tolerability] during the single-dose treatment period for ALTO-203 25 μg and ALTO-203 75 μg as compared to placebo.
Single-Dose Treatment Period Day 1 to Day 21
Multi-Dose Period: To understand the pharmacokinetics (PK) of multi-doses of ALTO-203 in capsule formulation
Multi-Dose Treatment Period Day 1 to Day 35
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Study Design & Arms

AllocationRANDOMIZED
MaskingQUADRUPLE
ModelCROSSOVER
PurposeTREATMENT

Treatment Arms

ArmTypeDescription
ALTO-203 25 μgEXPERIMENTALDrug: ALTO-203 25 μg Single-Dose Treatment Period: Single Dose, ALTO-203 25 μg Multi-Dose Treatment Period: ALTO-203 25 μg, administered orally, once daily for 28 days
ALTO-203 75 μgEXPERIMENTALDrug: ALTO-203 75 μg Single-Dose Treatment Period: Single Dose, ALTO-203 75 μg Multi-Dose Treatment Period: ALTO-203 75 μg, administered orally, once daily for 28 days
PlaceboPLACEBO_COMPARATORDrug: Placebo Single-Dose Treatment Period: Single Dose, Placebo Multi-Dose Treatment Period: Placebo, administered orally, once daily for 28 days

Interventions

NameTypeDescription
ALTO-203 25 μgDRUGActive, ALTO-203 25 μg
ALTO-203 75 μgDRUGActive, ALTO-203 75 μg
PlaceboDRUGComparator, Placebo-to-match
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Eligibility Criteria

Age Range25 Years to 64 Years
SexALL
Healthy VolunteersNo
Study Sites15

Inclusion Criteria: * Have a diagnosis of moderate major depressive disorder (MDD) * Presence of anhedonia symptoms * Not taking antidepressant at Screening Visit 2 * Willing to comply with all study assessments and procedures Exclusion Criteria: * Evidence of unstable medical condition * Diagnos...

Countries:United States
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Frequently asked questions about ALTO-203 25 μg

What is ALTO-203 25 μg used for?

ALTO-203 25 μg 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 been studied in patients with MDD, including those with anhedonia, a symptom of depression characterized by reduced ability to experience pleasure.

Who makes ALTO-203 25 μg?

ALTO-203 25 μg is being developed by Alto Neuroscience, Inc., a biopharmaceutical company traded on the stock exchange under the ticker symbol ANRO. The company is focused on developing precision treatments for psychiatric conditions, including Major Depressive Disorder.

What phase is ALTO-203 25 μg in?

ALTO-203 25 μg is in Phase 2 clinical development. It is an investigational drug and has not been approved by regulatory authorities. One Phase 2 trial has been completed, and the drug remains under clinical investigation for Major Depressive Disorder.

What clinical trials is ALTO-203 25 μg in?

ALTO-203 25 μg has been studied in one completed Phase 2 clinical trial registered as NCT06391563, titled 'PD, PK, and Safety of ALTO-203 in Patients With MDD.' This randomized, double-blind, placebo-controlled trial enrolled 69 participants with Major Depressive Disorder and anhedonia in the United States.

Is ALTO-203 25 μg the same as ALTO-203?

ALTO-203 25 μg is a specific dose strength of the investigational drug ALTO-203. The 25 μg formulation is being studied for its pharmacokinetics, pharmacodynamics, and safety in patients with Major Depressive Disorder, as part of the broader ALTO-203 development program.