SPTX

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EX-99.1

Exhibit 99.1

Seaport Therapeutics Reports Second Quarter 2026 Financial Results and Highlights Recent Corporate and Clinical Progress

Enrollment in Phase 2b BUOY-1 trial of GlyphAlloTM in major depressive disorder (MDD) is on track with topline data expected in 1H 2027

Phase 1 driving simulation trial of GlyphAllo on track to report topline data in 2H 2026

Following positive data from completed Phase 1 proof-of-concept trial of GlyphAgoTM, Company plans to initiate Phase 2a trial in patients with generalized anxiety disorder (GAD) and sleep disturbance in 2H 2026, and Phase 2b trial in patients with GAD in 1H 2027

Glyph2BLSDTM, a novel non-hallucinogenic neuroplastogen, is on track to complete first-in-human-enabling studies by the end of 2027

Upsized IPO in May generated $260.0 million in gross proceeds; $427.3 million in cash, cash equivalents, and investments as of June 30, 2026, expected to fund operations into 2029

BOSTON, August 3, 2026 -- Seaport Therapeutics, Inc., (Nasdaq: SPTX) (“Seaport” or the “Company”), a clinical-stage therapeutics company that is inventing and developing novel neuropsychiatric medicines, today announced financial results for the second quarter of 2026 and highlighted recent corporate and clinical progress.

“The second quarter of 2026 was marked by two major milestones for Seaport – positive results from our Phase 1 proof-of-concept trial of GlyphAgo and the successful completion of our IPO,” said Daphne Zohar, Co-Founder and Chief Executive Officer at Seaport Therapeutics. “We believe the GlyphAgo Phase 1 data package significantly derisks future clinical development of this program, and we expect to initiate Phase 2 development of GlyphAgo in generalized anxiety disorder in the second half of this year.

"In parallel, we are executing on two clinical trials of our lead product candidate, GlyphAllo, including the Phase 2b BUOY-1 trial in patients with major depressive disorder, and the Phase 1 driving simulation trial in healthy volunteers. Both trials are on track, and we look forward to data from the driving simulation trial in the coming months, ahead of topline data from BUOY-1 in the first half of next year.

“With the data that continue to emerge from psychedelics in neuropsychiatry, including LSD, we are excited about the potential of Glyph2BLSD, which is designed to harness the pharmacology of a psychedelic without causing a ‘trip,’ and may therefore avoid limitations of psychedelics, including the need for supervised administration.

“With a strong balance sheet and cash runway through multiple important clinical data readouts for our two lead programs, we are well-positioned to advance our pipeline through key inflection points and develop novel treatments for the hundreds of million people living with depression and anxiety.”

Recent Business Updates and Anticipated Milestones

GlyphAllo (SPT-300 or Glyph Allopregnanolone) Program for Patients with Major Depressive Disorder (MDD)

• Enrollment on Track in Phase 2b BUOY-1 Trial in MDD. Seaport is actively enrolling patients in BUOY-1, a two-arm, global, randomized, double-blind, placebo-controlled, potentially registration-enabling Phase 2b trial investigating the safety and efficacy of GlyphAllo in patients with MDD with or without anxious distress. Topline data from the BUOY-1 trial are expected in the first half of 2027.

• Phase 1 Driving Simulation Trial in Healthy Volunteers is On Track - Topline data Expected in 2H 2026. This randomized, double-blind, placebo-controlled Phase 1 trial is designed to evaluate the potential impact of multiple dose levels of GlyphAllo on simulated driving performance in healthy volunteers. In this trial, GlyphAllo is dosed in the evening, and simulated driving performance is assessed the following morning, approximately nine hours following GlyphAllo administration, as is typical in driving simulation trials. Topline data from the driving simulation trial are expected in the second half of 2026, in advance of the expected topline readout of the BUOY-1 trial.

• Presented Overview of the GlyphAllo Development Program at the Main Session of the 2026 American Society of Clinical Psychopharmacology (ASCP) Annual Meeting. In May 2026, Seaport presented oral and poster presentations highlighting the key clinical data generated in the Phase 1 and Phase 2a clinical trials of GlyphAllo and the design of the ongoing Phase 2b BUOY-1 trial of GlyphAllo in patients with MDD with or without anxious distress.

GlyphAgo (SPT-320 or Glyph Agomelatine) Program for Patients with Generalized Anxiety Disorder (GAD)

• Positive Proof-of-Concept Topline Results from Completed Phase 1 Trial in Healthy Volunteers

• In April 2026, Seaport reported positive topline results from the head-to-head crossover and single-ascending dose (SAD) portions of the trial. In the head-to-head crossover portion of the trial, GlyphAgo demonstrated a statistically signi

EX-99.1

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EX-99.1

Exhibit 99.1

Seaport Therapeutics Reports First Quarter 2026 Financial Results and Highlights Recent Corporate and Clinical Progress

New data from Phase 1 trial of GlyphAgoTM build upon previously reported topline data and further demonstrate GlyphAgoTM can achieve therapeutic exposures of agomelatine at doses projected to avoid liver enzyme elevations and reduce or eliminate the need for liver function testing

Enrollment in Phase 2b BUOY-1 trial of GlyphAlloTM is on track with topline data expected in 1H 2027; Seaport dosed first participant in Phase 1 driving simulation trial of GlyphAlloTM, with data expected in 2H 2026

Dr. Sharon Mates, Co-Founder, Chair, and CEO of Intra-Cellular Therapies until its acquisition by Johnson & Johnson for $14.6 billion, was appointed to Board of Directors

Upsized IPO generated $260.0 million in gross proceeds; in addition to $212.6 million on hand as of March 31, 2026, total cash, cash equivalents, and investments expected to fund operations into 2029

BOSTON, June 8, 2026 -- Seaport Therapeutics, Inc., (Nasdaq: SPTX) (“Seaport” or the “Company”), a clinical-stage therapeutics company that is inventing and developing novel neuropsychiatric medicines, today announced financial results for the first quarter of 2026 and highlighted recent corporate and clinical progress.

“The first quarter of 2026 was filled with meaningful progress for Seaport, and we significantly advanced the clinical development of our lead GlyphAlloTM and GlyphAgoTM programs,” said Daphne Zohar, Co-Founder and Chief Executive Officer at Seaport Therapeutics. “We previously reported data from the single-ascending dose and crossover portions of the Phase 1 proof-of-concept trial of GlyphAgoTM, which we believe substantially derisk future clinical development of the program. Today, we announced new multiple-ascending dose data from this trial, which further reinforce the ability of GlyphAgoTM to achieve therapeutic exposures of agomelatine at doses projected to avoid liver enzyme elevations. We continue to progress our potentially registration-enabling Phase 2b BUOY-1 trial of GlyphAlloTM and anticipate topline data from that trial in the first half of next year. With a pipeline of novel programs based on clinically validated mechanisms, an experienced team with a track record of success in neuropsychiatry, and a strong balance sheet bolstered by our recent IPO, we look forward to executing on our mission to transform the treatment of neuropsychiatric disorders and improve patients’ lives.”

Recent Business Updates and Anticipated Milestones

GlyphAlloTM (SPT-300 or Glyph Allopregnanolone) Program for Patients with Major Depressive Disorder (MDD)

• Enrollment on Track in Phase 2b BUOY-1 Trial in MDD. Seaport is actively enrolling patients in BUOY-1, a two-arm, global, randomized, double-blind, placebo-controlled, potentially registration-enabling Phase 2b trial investigating the safety and efficacy of GlyphAlloTM in patients with MDD with or without anxious distress. Topline data from the BUOY-1 trial are expected in the first half of 2027. Given the strength in enrollment and to maximize the likelihood that the BUOY-1 trial could be used to support registration, the Company plans to enroll the full prespecified target sample size of approximately 360 patients and no longer intends to perform a sample size re-estimation (SSRE).

• Dosed First Participant in Phase 1 Driving Simulation Trial. This randomized, double-blind, placebo-controlled Phase 1 trial is designed to evaluate the potential impact of multiple dose levels of GlyphAlloTMon simulated driving performance in healthy volunteers. GlyphAlloTMwill be dosed in the evening, and simulated driving performance will be assessed the following morning, approximately nine hours following GlyphAlloTMadministration, as is typical in driving simulation trials. Topline data from the driving simulation trial are expected in the second half of 2026, in advance of the expected topline readout of the BUOY-1 trial.

• Phase 1 and Phase 2a and Preclinical Data Published in Science Translational Medicine. This publication details the design, optimization, preclinical evaluation, and Phase 1 and 2a clinical development of GlyphAlloTM in healthy volunteers. In Phase 1 and 2a trials, GlyphAlloTM was generally well-tolerated following single- and multiple-ascending oral doses ranging from 70–1000 mg, provided dose-dependent, therapeutically relevant plasma exposures of allopregnanolone, demonstrated pharmacodynamic effects in the brain, and potently blunted the acute physiological stress response on a validated clinical model of anxiety.

GlyphAgoTM (SPT-320 or Glyph Agomelatine) Program for Patients with Generalized Anxiety Disorder (GAD)

• New Data Reported from Multiple-Ascending Dose (MAD) Portion of Phase 1 Proof-of-Concept Trial in Healthy Volunteers

• New data demonstrate that seven-day dosing of GlyphAgoTM achi