SPT-300 · program

GlyphAllo (SPT-300) for Major depressive disorder

Phase 2RecruitingSeaport Therapeutics, Inc. (SPTX)

SPT-300 (GlyphAllo) for MDD, with or without anxious distress. After positive Phase 1 PK/PD and a Phase 2a proof-of-concept (Trier Social Stress Test), advanced to the Phase 2b BUOY-1 study (NCT07065240, n=360); first patient dosed 17 Jul 2025.

Data current as of

Development timeline

Phase 2Jun 2025 – Jul 2025
  1. First patient dosed in Phase 2b BUOY-1 (GlyphAllo/SPT-300) in MDD with/without anxious distress.↗
  2. Phase 2b BUOY-1 study (NCT07065240) initiated.

Clinical trials in Major depressive disorder

NCT07161700Phase 2Recruitingn=360

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)

Started Sept 2025· Primary completion May 2027· 📍 31 sites across 6 countries (United States, Poland, Czechia, Germany)

NCT07065240BUOY-1Phase 2Recruitingn=360

Monotherapy Study of SPT-300 in Adults With Major Depressive Disorder, With or Without Anxious Distress (BUOY-1)

Started Jun 2025· Primary completion Mar 2027· 📍 59 sites across 7 countries (United States, Poland, Czechia, Germany)

Formulations

FormulationRouteRegimenPharmacokinetics
SPT-300 oral (GlyphAllo)Glyph triglyceride-mimetic prodrug (intestinal lymphatic transport, bypasses first-pass hepatic metabolism)
Oral once-daily prodrug of allopregnanolone. Phase 1 single/multiple ascending doses 70-1000 mg; Phase 2a single 375 mg dose; Phase 2b BUOY-1 dosed once-daily over a six-week treatment period. Approximately nine-fold greater allopregnanolone exposure than previously reported for oral allopregnanolone.
OralOnce daily—

Mechanism of action (compound-wide)

Oral prodrug releasing allopregnanolone, an endogenous neuroactive steroid and positive allosteric modulator of GABA-A receptors; the Glyph triglyceride-mimetic enables lymphatic absorption and bypasses first-pass hepatic metabolism.

TargetActionAffinity
GABA-A receptorprimaryPAM—ⓘ

← Full SPT-300 compound page (identity, identifiers, all indications)

Sources

  1. BUOY-1 (NCT07065240) — ClinicalTrials.gov
  2. clinicaltrials.gov — clinicaltrials.gov
  3. Seaport Therapeutics Announces First Patient Dosed in Phase 2b BUOY-1 Study of GlyphAllo (SPT-300) in MDD — Seaport Therapeutics