GH Research publishes Phase 2a PPD data for inhaled GH001
GH Research has published full results from its Phase 2a trial of inhaled mebufotenin (GH001) in postpartum depression (PPD), with the peer-reviewed paper appearing in The Journal of Clinical Psychiatry. The Dublin-headquartered, NASDAQ-listed company says the study met its primary endpoint and that all ten enrolled patients achieved remission within two hours of dosing.
The single-arm, open-label trial measured depression severity using the Montgomery–Åsberg Depression Rating Scale (MADRS). Participants recorded a mean reduction of 35.4 points from baseline to Day 8 (p<0.0001), and all ten women reached the remission threshold — a MADRS total score of ten or below — within two hours of receiving the inhaled treatment. Maternal functioning, assessed via the Barkin Index of Maternal Functioning, improved by a mean of 34.1 points, or 56%, at Day 8. No serious adverse events were reported, and breast milk analysis indicated that breastfeeding need only be paused briefly around the time of dosing.
Clinical significance
Kristina M. Deligiannidis, of the Feinstein Institutes for Medical Research at Northwell Health, described the findings as "the first published clinical trial of a psychedelic-based therapeutic specifically in postpartum depression," adding that "the rapid remission achieved by all patients within hours of a single-day inhaled treatment, sustained through Day 8 with a favourable safety profile and only brief interruption of breastfeeding, is encouraging for a population that needs additional rapid-acting therapeutic options."
The caveat is significant: ten participants in a single-arm, open-label design is a proof-of-concept signal, not confirmatory evidence. The company acknowledges this, and Deligiannidis explicitly called for "larger, randomised, placebo-controlled trials" to follow. Investors and clinicians should treat the data as hypothesis-generating rather than practice-changing at this stage.
Broader pipeline and conference presence
GH Research also announced that two oral presentations on GH001 in treatment-resistant depression (TRD) have been accepted at the 37th World Congress of Neuropsychopharmacology (CINP 2026), to be held in Glasgow from 26–29 June 2026. Both draw on the Phase 2b GH001-TRD-201 randomised controlled trial, which the company says met its primary endpoint with a MADRS reduction of 15.5 points versus placebo on Day 8. The presentations will cover antidepressant efficacy at six-month follow-up and the safety and tolerability profile from the open-label extension.
The PPD publication arrives in a competitive landscape for rapid-acting antidepressants. Sage Therapeutics and Biogen's brexanolone (Zulresso) was the first drug approved specifically for PPD, though its intravenous administration and 60-hour infusion requirement have limited uptake. A second Sage/Biogen asset, zuranolone, gained FDA approval in 2023 for both PPD and major depressive disorder in an oral formulation, representing the more commercially accessible comparator GH001 would need to displace or complement. The psychedelic-assisted therapy space more broadly — including psilocybin and MDMA-assisted programmes — continues to attract clinical and regulatory scrutiny, with the FDA's rejection of MDMA-assisted PTSD therapy in 2024 serving as a reminder that the regulatory path for psychedelic-derived drugs remains uncertain.
GH Research's next disclosed milestone is continued Phase 2b data readouts in TRD; the company has not yet announced a Phase 2b or Phase 3 start date for the PPD indication. Investors will be watching the Glasgow presentations for any updated signal on durability and whether the company intends to pursue a PPD-specific development pathway in parallel with its primary TRD programme.