Figure 3. Double-Blind Part: MADRS Suicidality Item 10 Responses at Baseline and Day 8 GH001 (n=40) Placebo (n=41) 6 5 4 3 2 1 0 100 90 80 70 60 50 40 30 20 10 0 Baseline Day 8 Baseline Day 8 Percentage of Patients by MA

62.5 77.5 70.7 68.3 22.5 10.0 12.2 12.2 12.5 5.0 5.0 14.6 17.1 Figure 3. Double-Blind Part: MADRS Suicidality Item 10 Responses at Baseline and Day 8 GH001 (n=40) Placebo

(n=41) 6 5 4 3 2 1 0 100 90 80 70 60 50 40 30 20 10 0 Baseline Day 8 Baseline Day 8 Percentage of Patients by MADRS Suicidality Item Score 2.5 2.5 2.4 2.4 Higher scores indicate worse symptoms. Abbreviation:

MADRS = Montgomery- sberg Depression Rating Scale. In the 6-month OLE, the numbers of patients reporting suicidal ideation according to the C-SSRS at all timepoints assessed during the trial were lower than before the first GH001

treatment period; C-SSRS items endorsed during each active treatment period are shown in Figure 4 Figure 4. Proportion of Patients Reporting Suicidal Ideationa by C-SSRS Item in Each GH001 Treatment Period in the Double-Blind Part and

the OLE 8.2 10.2 16.0 6.2 2.5 10.0 4.3 1.4 7.7 7.7 100 90 80 70 60 50 40 30 20 10 0 Predose Day 8 Active TP1 Predose Day 8 Active TP2 5.0 5.0 Predose Day 8 Active TP3 Predose Day 8 Active TP4 Predose Day

8 Active TP5 Percentage of Patients Indicating Yes on C-SSRS Items 1-3 1.7 1.7 3.8 Suicidal ideation Q3 Suicidal ideation Q2 Suicidal ideation Q1 aPatients responding "yes" to C-SSRS items 1 (wish to be dead), 2 (non-specific active

suicidal thoughts), or 3 (active suicidal ideation with any methods); no patients responded "yes" post-dose to items 4 (active suicidal ideation with some intent) or 5 (active suicidal ideation with specific plan). Abbreviations: C-SSRS

= Columbia-Suicide Severity Rating Scale; Q = Question; TP = Treatment period. During the OLE, the proportions of patients reporting a score of zero on MADRS item 10 at all timepoints during GH001 treatment were greater than that at

baseline of the double-blind part (Figure 5) - The median (range) change from baseline to Month 6 in MADRS score for item 10 was 0.0 (-3 to 2; n=74) Figure 5. MADRS Suicidality Item 10 Responses at Baseline and by Month in the

OLE 6 5 4 3 2 1 0 66.7 73.2 88.3 83.6 89.3 89.5 76.1 17.3 11.3 6.7 13.1 5.4 8.8 12.7 13.6 12.7 7.0 1.2 1.2 1.4 1.4 5.0 1.6 1.6 5.4 1.4 2.8 1.8 100 90 80 70 60 50 40 30 20 10 0 Month 5 Month

6/ET Baseline Day 28/Month 1 Month 2 Month 3 Month 4 Percentage of Patients by MADRS Suicidality Item Score Higher scores indicate worse symptoms. Abbreviations: ET = End of treatment; MADRS = Montgomery- sberg Depression Rating

Scale; OLE = Open-label extension. No TEAEs of suicidal intent or suicidal behavior occurred throughout the 6-month duration of the trial A TEAE of suicidal ideation occurred in one patient; the event lasted 6 hours before resolving

spontaneously - This TEAE was not accompanied by any changes in C-SSRS score beyond the duration for which the thoughts occurred, and the patient did not report any further TEAEs of suicidal ideation during the trial Conclusions In

this double-blind, placebo-controlled trial with a 6-month OLE in patients with TRD who were not at acute risk of suicide at baseline, GH001 was not associated with treatment-emergent events of suicidal ideation with intent or suicidal

behavior, or with any increased suicidal ideation as measured by the C-SSRS immediately following treatment or over time for up to 6 months These results support that GH001 was generally well tolerated and was associated with significant

reductions in depressive symptoms without increasing risk of suicide Treatment-resistant depression (TRD) is a debilitating condition that has been defined as a failure to respond to 2 adequate treatments for major depressive

disorder (MDD)1 Rates of suicidal ideation in patients with TRD are higher than in patients with treatment-responsive MDD (15% vs 6% of patients, respectively)2 - TRD is also associated with higher rates of attempted suicide, all-cause

mortality, and deaths by suicide3 There is a significant unmet need for safe and effective therapies for TRD that do not exacerbate suicidal intent In a Phase 2b trial, GH001, a synthetic form of mebufotenin (5-MeO-DMT) for pulmonary

inhalation, was well tolerated and resulted in rapid and significant improvements in depressive symptoms in patients with TRD Objective We describe the safety effects of GH001 on suicidal ideation and behavior in patients with TRD

enrolled in the Phase 2b trial Methods This trial (NCT05800860) included a 7-day, randomized, double-blind part and a 6-month open-label extension (OLE; Figure 1) In the double-blind part, patients were randomized 1:1 to receive an

individualized dosing regimen (IDR) of up to three escalating doses of GH001 (6, 12, and 18 mg) or placebo IDR on a single day with a 1-hour interval between doses In the OLE, patients received up to five GH001 IDR re-treatments over 6

months as needed, depending on the patient's clinical response and tolerability of previous IDRs Trial eligibility criteria excluded patients with suicidal ideation with intent (with items 4 or 5 on the Columbia- Suicide Severity Rating

Scale [C-SSRS] endorsed) within the past year, during the screening period, or at baseline; those with suicidal behaviors or non-suicidal self-injury in the past year; and those with a clinical assessment of significant suicide

risk Suicidal behavior and suicidal ideation were assessed using the C-SSRS at screening; during each treatment period at pre-dose, discharge, Day 2, and Day 8; and at all OLE scheduled visits (Day 15 and monthly up to Month 6/end of

treatment) The C-SSRS "baseline/screening" version was used at screening, and the "since last visit" version was used at all subsequent visits Suicidal ideation was defined as "yes" responses to items 1-5 (with items 4 and 5 indicating

suicidal ideation with intent), and suicidal behavior was defined as "yes" responses to items 6-10 Montgomery- sberg Depression Rating Scale (MADRS) item 10 (suicidal thoughts) was used to provide further quantification of suicidal

ideation, which was indicated by scores 2 on a scale from 0-64 Treatment-emergent adverse events (TEAEs) were assessed at each visit Results were analyzed descriptively Figure 1. Clinical Trial Schematic For re-treatment (up to five

GH001 IDRsa), the patient must have met one of the following criteria: MADRS score >18 MADRS score >10 and 18 and MADRS score 10 not observed at Day 8 of the prior treatment or at any visit since MADRS score >10 and 18 and

MADRS score >18 observed since the most recent observation of MADRS score 10 N=81 Randomization 1:1 GH001 IDRa Placebo IDRa Primary Endpoint MADRS Double-Blind Part (Part 1)b Day 1 Day 8 During the OLE, patients attended

visits at Day 15, Month 1, 2, 3, 4, 5 & 6c; additional clinic visits could be scheduled if required for medical reasons MADRS assessment Month 6 BL 2H D2 Day 2 This trial was conducted under the supervision of qualified

healthcare professionals, providing psychological support per standard of care, but without any planned psychotherapeutic intervention before, during, or after dosing All patients directly transitioned from the double-blind part to the

OLE Open-Label Extension (OLE; Part 2) aA second or third dose was administered if the previous dose was well tolerated according to the trial physician's judgment (based on vital signs and adverse events) and if the patient did not

achieve an intense psychoactive effect (peak experience; defined as a mean score of 75 on the Peak Experience Scale) following the previous dose. bEfficacy assessments were carried out by independent blinded raters in the double-blind

part. cPatients also attended assessment visits on Day 2 (telephone call) and Day 8 (in-person) after each re-treatment. Abbreviations: BL = Baseline; D = Day; H = Hour; IDR = Individualized dosing regimen; MADRS = Montgomery- sberg

Depression Rating Scale. TH71 Background Results Suicidal Ideation and Behavior in Patients with Treatment-Resistant Depression Treated with GH001 Sanjay J. Mathew1,*, Bernhard T. Baune2-4, Narc s Cardoner5, Wies aw J. Cuba a6, Kelly

Doolin7, Rosa Maria Due as Herrero8, David Gregory7, Lubo Jan 9, John R. Kelly10,11, Rachael MacIssac7, Shane J. McInerney12,13, Alexander Nawka14, Tom P len ek15, V ctor P rez Sola16-19, Andreas Reif20,21, Claire Sweeney7, Madhukar

H. Trivedi22, Velichka Valcheva7, Eduard Vieta19,23, Michael E. Thase24,25 *Presenting author: Sanjay J. Mathew, Department of Psychiatry and Behavioral Sciences, Texas A&M University Naresh K. Vashisht College of Medicine, Bryan,

TX, USA 1Department of Psychiatry and Behavioral Sciences, Texas A&M University Naresh K. Vashisht College of Medicine, Bryan, TX, USA; 2Department of Psychiatry, University of M nster, M nster, Germany; 3Department of Psychiatry,

University of Melbourne, Melbourne, VIC, Australia; 4The Florey Institute of Neuroscience and Mental Health, Parkville, VIC, Australia; 5Hospital Santa Creu i Sant Pau, Mental Health Research Group, Institut de Recerca Sant Pau,

Universitat Aut noma de Barcelona, CIBERSAM, Barcelona, Spain; 6Department of Psychiatry, Faculty of Medicine, Medical University of Gda sk, Gda sk, Poland; 7GH Research, Dublin, Ireland; 8Parc Sanitari Sant Joan de Deu Hospital de Dia de

Numancia, Barcelona, Spain; 9A-Shine SRO, Pilsen, Czechia; 10Psychedelic Research Group: Trinity College Dublin and Tallaght University Hospital, Dublin, Ireland; 11Department of Psychiatry, Tallaght University Hospital, Dublin, Ireland;

12Department of Psychiatry, University Hospital Galway, Galway, Ireland; 13Department of Psychiatry, University of Galway, Galway, Ireland; 14Institut Neuropsychiatrick P e, Praha, Czechia; 15Psyon s.r.o., Prague, Czechia; 16Mental

Health Institute, Hospital del Mar, Barcelona, Spain; 17Neurosciences Research Group, Hospital del Mar Research Institute (IMIM), Barcelona, Spain; 18Department of Psychiatry and Department of Experimental and Health Sciences, Pompeu

Fabra University, Barcelona, Spain; 19Centro de Investigaci n Biom dica en Red de Salud Mental (CIBERSAM), Instituto de Salud Carlos III, Madrid, Spain; 20Department of Psychiatry, Psychosomatic Medicine and Psychotherapy, University

Hospital Frankfurt - Goethe University, Frankfurt am Main, Germany; 21Fraunhofer Institute for Translational Medicine and Pharmacology ITMP, Theodor-Stern-Kai 7, 60596, Frankfurt am Main, Germany; 22Center for Depression Research and

Clinical Care, Peter O'Donnell Jr. Brain Institute and the Department of Psychiatry, University of Texas Southwestern Medical Center, Dallas, TX, USA; 23Hospital Clinic de Barcelona, Institute of Neuroscience, University of Barcelona,

IDIBAPS, CIBERSAM, Barcelona, Catalonia, Spain; 24Department of Psychiatry, University of Pennsylvania, Philadelphia, PA, USA; 25Corporal Michael J. Crescenz Veterans A airs Medical Center, Philadelphia, PA, USA References McIntyre RS,

et al. World Psychiatry. 2023;22:394-412. Mrazek DA, et al. Psychiatr Serv. 2014;65:977-87. Kern DM, et al. Brain Behav. 2023;13:e3171. Montgomery SA, Asberg M. Br J Psychiatry. 1979;134:382-9. Acknowledgments This trial was

sponsored by GH Research. The sponsor would like to thank the participants in the trial. The sponsor would also like to thank the investigators who conducted this trial. Under guidance of the authors, medical writing and editorial

support was provided by Jane A. Phillips, PhD, of OPEN Health, and funded by GH Research. Disclosures SJMa: Consultant Autobahn, Boehringer-Ingelheim, Clexio Biosciences, Engrail Therapeutics, EMA Wellness, Engrail Therapeutics, Motif

Neurotech, Neumora, Newleos, Relmada Therapeutics, Signant Health, Supernus, and Xenon Pharmaceuticals. Research support Abbott, Boehringer Ingelheim, and Engrail Therapeutics. BTB: Consultant - National Health and Medical Research

Council (Australia). Honoraria - Angelini, AstraZeneca, Biogen, BMS, Boehringer Ingelheim, Johnson & Johnson, LivaNova, Lundbeck, Medscape, Otsuka, P zer, Roche, Servier, Sumitomo Pharma, Sunovion, Teva, and Wyeth. Advisory boards -

Biogen, Boehringer Ingelheim, Janssen-Cilag, LivaNova, Lundbeck, Medscape, Novartis, Otsuka, and Teva. Research grants from private industries or nonpro t funds - AstraZeneca, BMBF (Germany), BMG (Germany), DFG (Germany), ERA PerMed, Fay

Fuller Foundation, Horizon Europe (European Union), James & Diana Ramsay Foundation (Adelaide), Johnson & Johnson, Lundbeck, La Marat de TV3, National Health and Medical Research Council (Australia), Sano -Synth labo, and

Wellcome Trust (UK). NC: Grants - Spanish Ministry of Health, Spanish Ministry of Science and Innovation (CIBERSAM), Strategic Plan for Health Research and Innovation (PERIS) 2016-2020, Recercaixa, and La Marat de TV3. Honoraria -

Adamed, Elsevier, Exeltis, Janssen, Lundbeck, P zer, and Servier. Advisory boards - Angelini, Esteve, Janssen, Lundbeck, Novartis, P zer, and Viatris. Lectures/meetings - Janssen, Lundbeck, and P zer. WJC: Grants - Acadia, Angelini,

Beckley Psytech, GH Research, HMNC Brain Health, Intra-Cellular Therapies, Janssen, MSD, Neumora, Novartis, Otsuka, and Recognify Life Sciences. Honoraria - Angelini, GH Research, Janssen, and Novartis. Advisory boards - Douglas

Pharmaceuticals, GH Research, Janssen, MSD, and Novartis. KD, DG, RM, CS, and VV are employees and shareholders of GH Research. RMDH: Principal investigator - Beckley Psytech and GH Research. Subinvestigator - Compass. LJ: Principal

investigator - GH Research. JRK: Principal investigator - Compass, GH Research, and Transcend Therapeutics. Consultant - Clerkenwell Health. Grant funding - Health Research Board (ILP-POR-2022-030, DIFA-2023-005, KTA-2024-002). SJMc:

Principal investigator - GH Research and Transcend Therapeutics. Honoraria - Janssen and Lundbeck. AN: Principal investigator - GH Research. TP: Principal investigator - Compass, GH Research, MAPS, and Ketabon. Shares - Psychedelick

klinika s.r.o., Spole nost pro podporu neurov dn ho v zkumu s.r.o., and AVI-X Aviation Experts s.r.o. Founder - PSYRES (Psychedelic Research Foundation). Consultant - CB21 Pharma and GH Research. VPS: Consultant, honoraria, or grants -

AB-Biotics, AstraZeneca, Bristol Myers Squibb, CIBERSAM, FIS-ISCiii, Janssen Cilag, Lundbeck, Medtronic, Otsuka, and Servier. AR: Honoraria for lectures and/or advisory boards - AbbVie, Boehringer Ingelheim, Cyclerion, Compass, GH

Research, Janssen, LivaNova, Medice, MSD, Newron, Sage/Biogen, and Shire/Takeda. Research grants - Medice and Janssen. MHT: Consultant - Acadia, Alkermes, Alto Neuroscience, Axsome, BasePoint Health Management, Biogen, Cerebral, Circular

Genomics, Compass, Daiichi Sankyo, GH Research, GreenLight VitalSign6, Heading Health, Janssen, Legion Health, Merck, Mind Medicine, Myriad Neuroscience, Naki Health, Neurocrine Biosciences, Noema Pharma, Orexo, Otsuka America, Otsuka

Europe, Otsuka Pharmaceutical Development & Commercialization, Praxis Precision Medicines, PureTech LYT, Relmada Therapeutics, Sage, Seaport Therapeutics, Signant Health, Sparian Biosciences, Titan Pharmaceuticals, Takeda, and WebMD.

Grant/research funding - American Foundation for Suicide Prevention, NCATS, NIDA, NIMH, Patient-Centered Outcomes Research Institute (PCORI), Blue Cross Blue Shield of Texas, SAMHSA, and the DoD. Editorial compensation - Elsevier and

Oxford University Press. EV: Grants - AB-Biotics, AbbVie, Almirall, AstraZeneca, Boehringer Ingelheim, Bristol Myers Squibb, Celon, Cephalon, Dainippon Sumitomo Pharma, Elan, Ferrer, GH Research, GlaxoSmithKline, Janssen, Lilly, Lundbeck,

Orion, Otsuka, P zer, Sano Aventis, Servier, Sunovion, and Takeda. Honoraria - Abbott, AbbVie, Angelini, AstraZeneca, Bristol Myers Squibb, Cambridge University Press, Elsevier, Farmindustria, Ferrer, Galenica, GlaxoSmithKline, Janssen,

Johnson & Johnson, Lilly, Lundbeck, Oxford University Press, Otsuka, P zer, Sano Aventis, and Viatris. Advisory boards - AbbVie, Angelini, AstraZeneca, Biogen, Biohaven, Bristol Myers Squibb, Celon, Compass, Ferrer, GH Research,

Gedeon Richter, HMNC, Idorsia, Janssen, Johnson & Johnson, Jazz, Lilly, Lundbeck, Merck Sharp & Dohme, Novartis, Organon, Otsuka, P zer, Roche, Sage, Sano Aventis, Servier, Shire, Sunovion, Takeda, and Teva. MET: Consultant -

Axsome, Clexio Biosciences, Gerson Lehrman Group, GH Research, Janssen, Johnson & Johnson, Lundbeck, Luye Pharma, Merck, Otsuka, P zer, Sage, Seelos Therapeutics, Sunovion, and Takeda. Grant support - Acadia, Alkermes, Axsome,

Intra-Cellular Therapies, Janssen, Myriad, National Institute of Mental Health, Otsuka, Patient-Centered Outcomes Research Institute (PCORI), and Takeda. Royalties - American Psychiatric Press, Inc., Guilford Publications, Herald House,

Wolters Kluwer, and W. W. Norton & Company. Spouse's employment - Dr. Diane Sloan is a Senior Vice President of OPEN Health, which does business with many companies. Presented at the 64th Annual Meeting of the American College of

Neuropsychopharmacology (ACNP) | Paradise Island, Bahamas | January 12-15, 2026 GH001 (n=40) Placebo (n=41) Eighty-one patients were randomized (GH001 IDR, 40 and placebo IDR, 41) in the double-blind part, and all transitioned directly

into the OLE Rates of historic and current suicidal ideation were balanced across treatment groups (Table 1) Table 1. Baseline Demographics and Clinical Characteristics Patient Demographics Age, years, mean (SD) 41.6 (11.4) 43.9

(10.9) Sex, female, n (%) 24 (60.0) 22 (53.7) Race, White, n (%) 40 (100) 41 (100) Actively employed, n (%) 33 (82.5) 29 (70.7) Disease Characteristics HAM-D-17 total score, mean (SD) 24.9 (2.6) 24.6 (2.3) MADRS total score,

mean (SD) 29.0 (5.4) 28.2 (4.6) CGI-S, mean (SD) 4.8 (0.7) 5.0 (0.6) Suicidality Non-suicidal self-injurious behavior Lifetime, n (%) 1 (2.5) 0 Past 12 months, n (%) 0 0 Baseline, n (%) 0 0 Suicidal ideation without

intenta Lifetime, n (%) 15 (37.5) 23 (56.1) Past 12 months, n (%) 10 (25.0) 18 (43.9) Baseline, n (%) 7 (17.5) 9 (22.0) Suicidal ideation with intenta Past 12 months, n (%) 0 0 Baseline, n (%) 0 0 Suicidal behaviora Past

12 months, n (%) 0 0 Baseline, n (%) 0 0 aSuicidal ideation without intent was defined as any "yes" answer to C-SSRS items 1-3; suicidal ideation with intent was defined as any "yes" answer to C-SSRS items 4-5; suicidal behavior was

defined as any "yes" answer to C-SSRS items 6-10; patients were counted for each category item to which they answered "yes" and therefore may be counted in more than one item. Abbreviations: CGI-S = Clinical Global Impression-Severity;

C-SSRS = Columbia-Suicide Severity Rating Scale; HAM-D-17 = Hamilton Rating Scale for Depression; MADRS = Montgomery- sberg Depression Rating Scale; SD = Standard deviation. In the GH001 group, suicidal ideation was reported by seven

patients at baseline and four at Day 8 (Figure 2) No GH001-treated patients developed new-onset suicidal ideation between baseline and Day 8 In the placebo group, five patients reported suicidal ideation both at baseline and at Day 8,

two reported suicidal ideation at baseline but not Day 8, and two patients without baseline suicidal ideation reported it at Day 8 No suicidal behaviors were reported in GH001- or placebo-treated patients at baseline or on any scheduled

C-SSRS assessments in the double-blind part 82.5 17.5 90.0 7.5 82.9 82.9 2.5 2.4 2.4 14.6 14.6 Percentage of Patients Indicating Yes Versus No on C-SSRS Items 1-3 Baseline Day 8 Baseline Day 8 Figure 2. Double-Blind Part:

Proportion of Patients with and without Suicidal Ideationa at Baseline and Day 8 by C-SSRS Item GH001 (n=40) Placebo (n=41) 0 20 40 50 60 70 90 30 10 80 100 Suicidal ideation Q3 Suicidal ideation Q2 Suicidal ideation Q1 No

suicidal ideation aPatients responding "yes" to C-SSRS items 1 (wish to be dead), 2 (non-specific active suicidal thoughts), or 3 (active suicidal ideation with any methods); no patients responded "yes" post-dose to items 4 (active

suicidal ideation with some intent) or 5 (active suicidal ideation with specific plan). Abbreviations: C-SSRS = Columbia-Suicide Severity Rating Scale; Q = Question. Baseline MADRS item 10 (suicidal thoughts) scores were similar between

the two treatment groups, and patients who received GH001 did not report worsening of symptoms on Day 8 of the double-blind part as per MADRS item 10 (Figure 3) - The median (range) change from baseline to Day 8 in MADRS score for item

10 was 0.0 (-2 to 1) for patients who received GH001 and 0.0 (-1 to 2) for patients who received placebo