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SPT-300

Phase 2

Major Depressive Disorder (MDD) | Small molecule | Psychiatry |Seaport Therapeutics, Inc.|Last Updated: Aug 17, 2026

Target and mechanism

Molecular targetallopregnanolone
Target classHormone
ModalitySmall molecule

Success Probability

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Market & Valuation

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Trial Design

RandomizedDouble-BlindPLACEBO_CONTROLLEDDMC
Total Trials2
Total Enrollment720

FDA Designations

No designations recorded

Clinical trial landscape

SPT-300 · 2 trials · 2 indications

Phase 2 2
NCT07161700An Open-Label Extension Study to Evaluate the Safety and Tolerability of SPT-300 (GlyphAllo) in Participants With Major Depressive Disorder, With or Without Anxious Distress (BUOY-1 OLE Study)Major Depressive Disorder (MDD)
ENROLLING BY_INVITATION360 Analytics
NCT07065240A Study to Evaluate the Efficacy and Safety of SPT-300 (GlyphAllo) in Participants With Major Depressive Disorder, With or Without Anxious Distress (BUOY-1 Study)Major Depressive Disorder (MDD)
RECRUITING360 Analytics
PHASE2ENROLLING BY_INVITATION
An Open-Label Extension Study to Evaluate the Safety and Tolerability of SPT-300 (GlyphAllo) in Participants With Major Depressive Disorder, With or Without Anxious Distress (BUOY-1 OLE Study)
Major Depressive Disorder (MDD)Unlock trial analytics
PHASE2RECRUITING
A Study to Evaluate the Efficacy and Safety of SPT-300 (GlyphAllo) in Participants With Major Depressive Disorder, With or Without Anxious Distress (BUOY-1 Study)
Major Depressive Disorder (MDD)Unlock trial analytics

Study Endpoints

Primary Endpoints

Safety and tolerability assessments based on Treatment-emergent Adverse Events (TEAEs), Serious Adverse Events (SAEs) and validated clinical scales and procedures
Up to Day 49

Adverse events (AEs) are monitored from Day 1 to 49. A TEAE is as any AE with an onset after first dose of study treatment up to Day 49. Clinically significant abnormalities in clinical laboratory evaluations, ECGs, vital signs, physical examinations and Columbia Suicide Severity Rating Scale (C-SSRS) will be reported as TEAEs.

Change From Baseline to Day 42 in Hamilton Depression Rating Scale-17 (HAM-D-17) Total Score
Baseline (Day 0) to Day 42

HAM-D-17 is a 17-item, clinician-administered rating scale to assess the severity of symptoms in participants diagnosed with depression. The HAM-D-17 comprises individual ratings related to the following symptoms: depressed mood (sadness, hopeless, helpless, worthless), feelings of guilt, suicide, insomnia (early, middle, late), work and activities, retardation (slowness of thought and speech; impaired ability to concentrate; decreased motor activity), agitation, anxiety (psychic and somatic), somatic symptoms (gastrointestinal and general), genital symptoms, hypochondriasis, loss of weight, and insight. HAM-D Total Scores range from 0 to 52, with higher scores indicating more severe depression.

Secondary Endpoints

Change From Baseline to Day 42 in Clinical Global Impression - Severity (CGI-S)
Baseline (Day 0) to Day 42
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Study Design & Arms

AllocationNA
MaskingNONE
ModelSINGLE_GROUP
PurposeTREATMENT

Treatment Arms

ArmTypeDescription
SPT-300EXPERIMENTALParticipants will receive SPT-300 capsules once daily for 42 days
PlaceboPLACEBO_COMPARATORParticipants will receive matching placebo once daily for 42 days

Interventions

NameTypeDescription
SPT-300DRUGA prodrug of allopregnanolone, a small molecule drug
PlaceboDRUGPlacebo for SPT-300
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Eligibility Criteria

Age Range18 Years to 66 Years
SexALL
Healthy VolunteersNo
Study Sites40

Inclusion Criteria: * Participant who completed treatment in Study SPT-300-2024-203 (i.e., participant who competed Visit 8 \[Day 42\] of Study SPT-300-2024-203 \[BUOY-1 Study\]). * Women of childbearing potential (WOCP) must not plan to become pregnant during the course of the study or be currentl...

Countries:United StatesBulgariaCzechiaGermanyHungaryPolandSlovakia
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Recent Changes (Last 90 Days)

LOWAug 17, 2026NCT07065240lastUpdatePostDate: changed
LOWAug 17, 2026NCT07161700lastUpdatePostDate: changed
LOWAug 17, 2026NCT07065240lastUpdatePostDate: changed
LOWAug 17, 2026NCT07161700lastUpdatePostDate: changed
LOWJul 13, 2026NCT07065240lastUpdatePostDate: changed
LOWJul 13, 2026NCT07161700lastUpdatePostDate: changed
LOWJul 13, 2026NCT07065240lastUpdatePostDate: changed
LOWJul 13, 2026NCT07161700lastUpdatePostDate: changed

Frequently asked questions about SPT-300

What is SPT-300 used for in Major Depressive Disorder?

SPT-300 is an investigational small molecule being developed for the treatment of Major Depressive Disorder (MDD), including MDD with anxious distress. It is currently in Phase 2 clinical development and has not been approved by the FDA.

What does SPT-300 target?

SPT-300 targets allopregnanolone, a hormone that modulates brain activity. By acting on this target, SPT-300 is being studied for its potential to address symptoms of Major Depressive Disorder, including those with anxious distress.

Who makes SPT-300?

SPT-300 is being developed by Seaport Therapeutics, Inc., a biopharmaceutical company. The company is conducting clinical trials to evaluate the drug's efficacy and safety in patients with Major Depressive Disorder.

What phase is SPT-300 in?

SPT-300 is currently in Phase 2 clinical development. It is an investigational drug, meaning it has not yet received regulatory approval and is still being studied in clinical trials for Major Depressive Disorder.

What clinical trials is SPT-300 in?

SPT-300 is being evaluated in two Phase 2 trials: NCT07065240, a placebo-controlled study in participants with Major Depressive Disorder with or without anxious distress, and NCT07161700, an open-label extension study assessing long-term safety and tolerability.

Is SPT-300 the same as GlyphAllo?

Yes, SPT-300 is also known as GlyphAllo. Both names refer to the same investigational drug being developed by Seaport Therapeutics for the treatment of Major Depressive Disorder.