A Randomized, Parallel-Group, Double-Blind, Placebo-Controlled, Monotherapy Study of the Efficacy, Safety, and Tolerability of SPT-300 in Adults with Major Depressive Disorder (MDD), with or without Anxious Distress

Overview

Sponsor-declared trial summary

Key facts

Sponsor

Seaport Therapeutics Inc.

Participant type

Patients

Age range

18-64 years, 65+ years

Gender

Male and Female

Therapeutic area

Psychiatry and Psychology [F] - Mental Disorders [F03]

Trial duration

11 Sep 2025 → ongoing

Decision date (initial)

2025-08-07

Transition trial

No

Low-intervention

No

Rare-disease indication

No

Vulnerable population

Yes

Funding sources

Seaport Therapeutics

Trial design

CTIS Part I — objectives, methods, condition coding

Main objective

Scope: Therapy, Efficacy, Others, Safety

To characterize the effects of SPT-300 as a monotherapy on depressive symptoms in participants with MDD, with or without anxious distress

Secondary objectives 1

1. To characterize the effects of SPT-300 on overall illness severity in participants with MDD, with or without anxious distress

Conditions and MedDRA coding

Major Depressive Disorder (MDD), with or without Anxious Distress

Eligibility criteria

Principal inclusion / exclusion criteria as submitted by sponsor

Inclusion criteria 3

1. Participant is a male or female between 18 and 65 years of age, inclusive willing and able and have capacity to provide written informed consent.
2. Participants must have a primary diagnosis of MDD. Participants with a diagnosis of comorbid generalized anxiety disorder, social anxiety disorder, or panic disorder (with or without agoraphobia) may be included if not the focus of treatment over the past 6 months prior to Screening and the Investigator considers MDD to be the primary diagnosis at Screening and Baseline.
3. Eligible participants must have a current depressive episode of at least 4 weeks, but no greater than 18 months in duration prior to Screening.

Exclusion criteria 9

1. History of, or current presentation consistent with: a. any depressive episode with psychotic or catatonic features b. any bipolar manic, hypomanic or mixed episode, and substance-induced (eg, antidepressant-induced) manic, hypomanic/mixed episode c. bipolar disorder, including history of bipolar depression, or current presentation consistent with bipolar depression d. schizophrenia, schizoaffective, or other psychotic disorder e. obsessive-compulsive disorder f. any persistent neurocognitive disorder
2. Psychiatric hospitalization within current depressive episode. Participants with MDD that requires hospitalization are not eligible for the study.
3. Evidence or history of clinically significant disease which can affect the patients’ participation.
4. Previous history of intolerance or significant adverse effects, including drug allergy to allopregnanolone or any components of the SPT-300/placebo formulation.
5. Participant has a history of drug or alcohol use disorder.
6. Participants with a positive test for cannabinoids.
7. Clinically significant risk of suicide or harm to self or others.
8. History of treatment-resistant depression defined as 2 or more failed treatments of adequate dose and duration in the current depressive episode.
9. Borderline or antisocial personality disorder or other disorder of sufficient severity that judged by the Investigator could interfere with participation in this study.

Endpoints

Primary and secondary outcome measures (English text)

Primary endpoints 1

1. Change from Baseline to Visit 6 (Study Day 42) in Hamilton Depression Rating Scale-17 (HAM-D-17) total score

Secondary endpoints 1

1. Change from Baseline to Visit 6 (Study Day 42) in Clinician Global Impression-Severity (CGI-S)

Investigational products

Investigational medicinal products (IMPs), comparators, placebo, auxiliary

Test 1

Placebo 1

Sponsors and contacts

Sponsor organisations, regulatory contacts, third parties

Seaport Therapeutics Inc.

Sponsor organisation

Seaport Therapeutics Inc.

Address

101 Seaport Boulevard Floor 12

City

Boston

Postcode

02210-2149

Country

United States

Scientific contact point

Organisation

Seaport Therapeutics Inc.

Contact name

Clinical trial information desk

Public contact point

Organisation

Seaport Therapeutics Inc.

Contact name

Clinical trial information desk

Third parties 15

Locations

7 EU/EEA countries · 32 investigational sites

By country

Investigational sites

Country notifications

Trial-start, recruitment-start, end and early-termination notifications submitted per Member State

Results and documents

Annex IV summary of results, Annex V layperson summary, and all documents registered in CTIS for this trial

Documents 170 files

Public protocol annexes, IB summaries, regulatory submissions and post-authorisation documents registered in CTIS.

Application history

12 submissions — initial application plus substantial / non-substantial modifications