A Phase 2 interventional study of SPT-300 and Placebo in Major Depressive Disorder (MDD) and Major Depressive Disorder With Anxious Distress, sponsored by Seaport Therapeutics. Recruiting at 62 sites in 7 countries. Open to participants aged 18 Years to 65 Years. Per ClinicalTrials.gov, last updated 2026-11-10.
Sponsored by Seaport Therapeutics · Phase 2, Interventional, and Treatment
This is a randomized, parallel-group, double-blind, placebo-controlled, monotherapy study to evaluate the efficacy, safety, and tolerability of SPT-300 (GlyphAllo) in adults with major depressive disorder (MDD), with or without anxious distress.
3,041 studies on the registry are indexed under Depressive Disorder, Major; 588 are open to participants now.
This study's planned enrollment of 360 is above the median of 79 across 2,530 interventional studies indexed under Depressive Disorder, Major.
Browse Depressive Disorder, Major studies →Seaport Therapeutics is the lead sponsor of 2 studies on the registry; 2 are open to participants now.
Counted across the registry records on this site, refreshed daily.
Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
Exclusion Criteria:
History of, or current presentation consistent with:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Able to become pregnant: from the first period until menopause, unless permanently unable to through surgery (removal of the womb, or of both ovaries or both fallopian tubes).
Criteria for people of childbearing potential usually ask for a negative pregnancy test and for contraception during the study and for a time after it.
Ways of preventing pregnancy. “Highly effective” methods fail less than 1% of the time a year when used correctly — for example an IUD or an implant.
Criteria usually say which methods count and how long to keep using them after the last dose, sometimes for male participants too. Some studies accept a partner’s vasectomy if it was confirmed successful and that person is the participant’s only sexual partner.
Weight in kilograms divided by height in metres squared. Example: 70 kg and 1.75 m gives 70 ÷ (1.75 × 1.75) ≈ 22.9.
What counts as overweight or obesity differs between countries (some use lower cut-offs), so go by the range the study states.
Judged by the study doctor to matter for your health or for the study. It is a doctor’s decision, so ask the study team if you are unsure whether something counts.
Informed consent
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Childbearing potential
Able to become pregnant: from the first period until menopause, unless permanently unable to through surgery (removal of the womb, or of both ovaries or both fallopian tubes).
Criteria for people of childbearing potential usually ask for a negative pregnancy test and for contraception during the study and for a time after it.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Contraception
Ways of preventing pregnancy. “Highly effective” methods fail less than 1% of the time a year when used correctly — for example an IUD or an implant.
Criteria usually say which methods count and how long to keep using them after the last dose, sometimes for male participants too. Some studies accept a partner’s vasectomy if it was confirmed successful and that person is the participant’s only sexual partner.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
BMI (body mass index)
Weight in kilograms divided by height in metres squared. Example: 70 kg and 1.75 m gives 70 ÷ (1.75 × 1.75) ≈ 22.9.
What counts as overweight or obesity differs between countries (some use lower cut-offs), so go by the range the study states.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Clinically significant
Judged by the study doctor to matter for your health or for the study. It is a doctor’s decision, so ask the study team if you are unsure whether something counts.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Participants will receive SPT-300 capsules once daily for 42 days
Drug: SPT-300
Participants will receive matching placebo once daily for 42 days
Drug: Placebo
A prodrug of allopregnanolone, a small molecule drug
Also known as: LYT-300, GlyphAllo, Glyph Allopregnanolone
Placebo for SPT-300
Change From Baseline to Day 42 in Hamilton Depression Rating Scale-17 (HAM-D-17) Total Score
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.
Time frame: Baseline (Day 0) to Day 42
Change From Baseline to Day 42 in Clinical Global Impression - Severity (CGI-S)
The CGI-S is a clinician-administered rating scale to assess the severity of the participant's illness at the time of the assessment relative to the clinician's past experience with patients who have the same diagnosis. Scores range from 1 to 7, with higher scores indicating more severe illness.
Time frame: Baseline (Day 0) to Day 42
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Started Jun 2025 (actual). Primary completion is estimated for Mar 2027, 21 months after the start.
Of 96 industry-sponsored phase 2 interventional studies under Depressive Disorder, Major, half reached primary completion within 17 months of starting (the median), counting those still running; a quarter within 11 and three quarters within 23. This study's planned 21 months is above that.
Counting every sponsor, half of 195 studies reached it within 22 months; a quarter within 14 and three quarters within 37.
How these figures are worked out, and which studies are left out of them.
From the registry record's own update history. This site started tracking changes on Sep 25, 2026; for anything earlier, see the record history on ClinicalTrials.gov ↗
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