PureTech Founded Entity Seaport Therapeutics Announces First Patient Dosed in Phase 2b BUOY-1 Study of GlyphAllo™ (SPT-300) in Major Depressive Disorder (MDD), With or Without Anxious Distress

Associated Press

17-07-2025

BOSTON--(BUSINESS WIRE)--Jul 17, 2025--
PureTech Health plc (Nasdaq: PRTC, LSE: PRTC) ('PureTech'), a clinical-stage biotherapeutics company, noted that its Founded Entity, Seaport Therapeutics, ('Seaport') a clinical-stage biopharmaceutical company that is advancing novel neuropsychiatric medicines with a proven strategy and team, today announced that the first patient has been dosed in the Phase 2b BUOY-1 study of GlyphAllo™ SPT-300 or Glyph Allopregnanolone) in major depressive disorder (MDD) with or without anxious distress.
GlyphAllo is a novel, 'Glyphed' oral prodrug of allopregnanolone, an endogenous molecule that has been shown to dampen stress. Allopregnanolone has been clinically validated in third-party trials as a rapidly acting antidepressant with anxiolytic effects, but its scope of clinical use was previously constrained by limitations that the Glyph™ platform is specifically designed to solve. GlyphAllo has the potential to be a first-in-class treatment for patients with MDD, including those with or without anxious distress.
The full text of the announcement from Seaport is as follows:
Seaport Therapeutics Announces First Patient Dosed in Phase 2b BUOY-1 Study of GlyphAllo™(SPT-300) in Major Depressive Disorder (MDD), With or Without Anxious Distress
BUOY-1 builds on successful Phase 1 and Phase 2a data with GlyphAllo – a novel oral prodrug of allopregnanolone and a potential first-in-class treatment for MDD
Allopregnanolone has demonstrated rapid antidepressant and anxiolytic activity in clinical settings, but its clinical scope was previously constrained by limitations that Glyph™ is specifically designed to solve
Boston, MA – July 17, 2025 – Seaport Therapeutics ('Seaport' or the 'Company'), a clinical-stage biopharmaceutical company that is advancing novel neuropsychiatric medicines with a proven strategy and team, today announced that the first patient has been dosed in the Phase 2b BUOY-1 study of GlyphAllo™ (SPT-300 or Glyph Allopregnanolone) in major depressive disorder (MDD) with or without anxious distress. GlyphAllo is a novel, 'Glyphed' oral prodrug of allopregnanolone, an endogenous molecule that has been shown to dampen stress. Allopregnanolone has been clinically validated in third-party trials as a rapidly acting antidepressant with anxiolytic effects, but its scope of clinical use was previously constrained by limitations that the Glyph™ platform is specifically designed to solve. GlyphAllo has the potential to be a first-in-class treatment for patients with MDD, including those with or without anxious distress.
'The initiation of BUOY-1 marks a significant milestone for Seaport's pipeline, bringing us closer to a potential new treatment for major depression, which impacts around 280 million people globally – nearly 60 percent of whom also experience anxious distress,' said Daphne Zohar, Co-Founder and Chief Executive Officer at Seaport Therapeutics. 'This is an important step on our journey to deliver new treatments for patients living with depression, anxiety, and other neuropsychiatric conditions.'
BUOY-1 is a global, randomized, double-blind, placebo-controlled study that will evaluate the efficacy, safety, and tolerability of GlyphAllo in adults with MDD, with or without anxious distress, a subtype of depression characterized by significant anxiety. The study is expected to enroll up to approximately 360 patients, randomized 1:1 to receive either GlyphAllo or placebo once-daily over a six-week treatment period. The primary endpoint of the study is the change from baseline at six weeks in the Hamilton Depression Rating Scale-17 (HAM-D-17), a gold-standard depression severity rating scale. Following the initial treatment period, eligible patients may enter an open-label extension phase, during which all participants will receive GlyphAllo for up to an additional six weeks.
'CNS clinical trials are inherently complex, and we are applying our team's extensive expertise to implement a high-quality study,' said Antony Loebel, M.D., Chief Medical Officer, President of Clinical Development at Seaport Therapeutics. 'We are confident that our rigorous clinical trial execution, including an emphasis on the quality of patient enrollment, will build on a proven mechanism and established clinical efficacy, to increase our likelihood of success in developing an effective treatment for patients with depression.'
The BUOY-1 study builds on a foundation of positive clinical data from Phase 1 and Phase 2a studies of GlyphAllo in healthy volunteers. In Phase 1, GlyphAllo demonstrated approximately nine times greater allopregnanolone exposure than that previously reported following oral dosing of allopregnanolone and reached similar exposures to the efficacious doses of IV-infused allopregnanolone. The two key measures used to determine allopregnanolone-associated brain activity, EEG beta frequency power and reduction in saccadic eye velocity, confirmed that GlyphAllo engaged with its target in a dose-dependent manner. The overall safety data, pharmacokinetics, and pharmacodynamic findings, along with non-clinical studies, support six-week dosing of GlyphAllo in BUOY-1.
In a Phase 2a proof-of-concept study in healthy volunteers using the Trier Social Stress Test (TSST), a validated clinical model of anxiety, GlyphAllo significantly reduced the stress hormone salivary cortisol at all post-TSST timepoints compared to placebo, meeting the primary endpoint with a p-value of 0.0001 and demonstrating that GlyphAllo regulates hypothalamic-pituitary-adrenal axis reactivity to acute stress. GlyphAllo was generally well-tolerated, with adverse events that were mostly mild and transient.
For more information, visit www.puretechhealth.com or connect with us on X (formerly Twitter) @puretechh.
Rosellini, A., et al (2018). Anxious distress in depressed outpatients: Prevalence, comorbidity, and incremental validity.
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PUB: 07/17/2025 07:05 AM/DISC: 07/17/2025 07:05 AM
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