GH Research PLC (Nasdaq: GHRS) May 2026 Ultra-Rapid, Durable Remission in TRD with Minimal Clinic Burden 2026© GH Research PLC 1

Any statements contained herein that do not describe historical facts are forward-looking statements that are based on management’s expectations and are subject to certain factors, risks and uncertainties that may cause actual results, outcomes, timing and performance to differ materially from those expressed or implied by such statements. These factors, risks and uncertainties include, but are not limited to: the costs and uncertainties associated with GH Research’s research and development efforts; the inherent uncertainties associated with the conduct, timing and results of nonclinical and clinical studies of GH Research’s product candidates; GH Research’s expectations related to commencing trials in the US; GH Research’s ability to obtain, maintain, enforce and defend issued patents; the adequacy of GH Research’s capital resources, the availability of additional funding and GH Research’s cash runway; and other factors, risks and uncertainties described in GH Research’s filings with the U.S. Securities and Exchange Commission. Except as otherwise noted, these forward-looking statements speak only as of the date of this presentation, and GH Research undertakes no obligation to update or revise any of such statements to reflect events or circumstances occurring after this presentation. Because forward-looking statements are inherently subject to risks and uncertainties, some of which cannot be predicted or quantified and some of which are beyond GH Research’s control, you should not rely on these forward-looking statements as predictions of future events. The events and circumstances reflected in any such forward-looking statements may not be achieved or occur and actual results could differ materially from those projected in the forward-looking statements. GH Research cautions you not to place undue reliance on the forward-looking statements contained in this presentation. This presentation has been prepared by GH Research PLC (“GH Research”). Nothing contained in this presentation is, or should be construed as, a recommendation, promise or representation by the presenter or GH Research or any director, employee, agent, or adviser of GH Research. This presentation does not purport to be all-inclusive or to contain all of the information you may desire. This presentation does not constitute an offer to sell or the solicitation of an offer to buy securities, nor shall there be any sale of securities in any state or jurisdiction in which such offer, solicitation or sale would be unlawful prior to registration or qualification under the securities laws of any such state or jurisdiction. This presentation contains forward-looking statements, all of which are qualified in their entirety by this cautionary statement. Many of the forward-looking statements contained herein can be identified by the use of forward-looking words such as “may”, “anticipate”, “believe”, “could”, “expect”, “should”, “plan”, “intend”, “estimate”, “will”, “potential” and “ongoing”, among others, although not all forward-looking statements contain these identifying words. Disclaimer Regarding Forward-Looking Statements 2 2026© GH Research PLC

Product Candidate Indication Preclinical Phase 1 Phase 2a Phase 2b Phase 3 Current Status Milestone GH001 Mebufotenin for inhalation administration Treatment-resistant depression (TRD) Phase 2b RDBPC completed Phase 3 initiation in 2026 Postpartum depression (PPD) Phase 2a POC Completed Bipolar II Disordera (BDII) Phase 2a POC Completed GH002 Mebufotenin for i.v. administration Psychiatric disorder Phase 1 HV trial completed IND submission Pipeline 3 aBipolar II disorder with a current major depressive episode. Abbreviations: HV = Healthy volunteer; IND = Investigational New Drug; i.v. = Intravenous; PK = Pharmacokinetics; POC = Proof-of-concept; RDBPC = Randomized, double-blind, placebo-controlled. 2026© GH Research PLC Cash, cash equivalents and marketable securities were $267.3 million as of March 31, 2026 Completed In Planning

Phase 2b Trial Unprecedented Efficacy in TRD Positioning GH001 as potentially practice-changing GH001 Key Milestones Achieved and Next Steps Pivotal Phase 3 Program Designed in line with the FDA Guidelines and to replicate the Phase 2b data Global Phase 3 start in 2026 Abbreviations: TRD = Treatment Resistant Depression; IND = Investigational New Drug; FDA = Food and Drug Administration >> 4 2026© GH Research PLC

5 Retreatment of up to five GH001 IDRs if patients met retreatment criteriaa Open-Label Extension (OLE) n=81 Randomization 1:1 GH001 IDR Placebo IDR BL 2h Day 1 Primary endpoint ΔMADRS Day 8 During the OLE, patients attended visits at Day 15, Month 1, 2, 3, 4, 5 & 6b Additional clinic visits could be scheduled if required for medical reasons MADRS assessment Month 6 D2 Day 2 Double-Blind Partc 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 GH001-TRD-201: A Randomized, Double-Blind, Placebo-Controlled, Phase 2b Trial with an Open-Label Extension aRetreatment criteria: MADRS score >18, or MADRS score >10 and ≤18 and MADRS score ≤10 not observed at Day 8 of the prior treatment or at any visit since, or MADRS score >10 and ≤18 and MADRS score >18 observed since the most recent observation of MADRS score ≤10. bPatients also attended assessment visits on Day 2 (phone call) and Day 8 after each retreatment. cEfficacy assessments were carried out by independent blinded raters in the double-blind part. Abbreviations: BL = Baseline; D = Day; h = Hour; IDR = Individualized dosing regimen; MADRS = Montgomery–Åsberg Depression Rating Scale. ClinicalTrials.gov. https://clinicaltrials.gov/study/NCT05800860, Accessed March 13, 2025. 2026© GH Research PLC

Primary Endpoint: GH001 Led to Mean MADRS Reduction from Baseline of -15.5 on Day 8a vs Placebo (P<0.0001) aFDA Guidance notes that efficacy with rapid-acting antidepressants generally should be demonstrated within 1 week, supporting a primary efficacy endpoint within this timeframe. Abbreviations: BL = Baseline; FDA = Food and Drug Administration; H = Hours; LS = Least squares; MADRS = Montgomery-Åsberg Depression Rating Scale; SE = Standard error. FDA Guidance: Major Depressive Disorder: Developing Drugs for Treatment. https://www.fda.gov/media/113988/download. Accessed on 26 June 2025. LS mean difference vs placebo: −15.5 (P<0.0001) Effect size: Cohen’s d = −2.0 LS Mean (±SE) Change from Baseline in MADRS Total Score BL 2H Day 2 Day 8 GH001 (n=40) Placebo (n=41) 2026© GH Research PLC 6

GH001 vs Placebo Spravato Mono Spravato +AD Spravato Mono Spravato + AD vs Placebo + AD from TRANSFORM-2a Spravato monotherapy (84mg) vs Placebo from TRD4005b Spravato +AD Not reported Key Secondary Endpoint MADRS Total Score Change from Baseline: GH001 and Spravato at Day 2 and Primary Endpoint (Difference from Comparator Arm) 7 Note: To-date, no head-to-head comparisons of any other products to any of our product candidates in any clinical trial have been completed; results have been obtained from different trials with different designs, endpoints and patient populations; results may not be comparable. aSpravato + AD data from TRANSFORM-2, Popova et al., 2019; bSpravato monotherapy data for 84mg dose from TRD4005 trial, Janik et al., 2025; Spravato 56mg MADRS total score change from baseline difference of LS means from PBO was -5.1 at Day 28 and -3.8 at Day 2 Abbreviations: AD = Antidepressant; BL = Baseline; D = Day; LS = Least Squares; MADRS = Montgomery-Åsberg Depression Rating Scale; Mono = Monotherapy. 2026© GH Research PLC

Remission Rates with GH001 Remission Rates with Spravato monotherapy (84mg) from TRD4005b Note: To-date, no head-to-head comparisons of any other products to any of our product candidates in any clinical trial have been completed; results have been obtained from different trials with different designs, endpoints and patient populations; results may not be comparable. aRemission defined as MADRS total score ≤10 for both GH001 and Spravato. bSource: Spravato monotherapy data for 84mg dose from TRD4005 trial, Janik et al. 2025; Spravato 56mg participants in the TRD4005 trial achieved remission rates of 13.1% at Day 2, 7.1% at Day 8 and 14.6% at Day 28 (MADRS ≤10) Abbreviations: MADRS = Montgomery-Åsberg Depression Rating Scale Secondary Endpoints: Remissionsa GH001 Day 2 and Day 8 and Spravato Monotherapy (84 mg) Day 2, Day 8 and Day 28 GH001 Placebo Spravato Placebo 8 2026© GH Research PLC

9 73% Remission Rate at 6 Months in OLE Completers aIncludes 63 patients who completed the 6-month OLE per protocol (18 patients terminated early are excluded). bApproximately 6 months post-study start (median 168 days from Day 1 of double-blind part). cRemission defined as MADRS total score ≤10. Abbreviations: MADRS = Montgomery-Åsberg Depression Rating Scale; OLE = Open-label extension. Double-blind n=40 patients who received GH001 OLE n=63 OLE completersa Day 8 Month 6b Percentage of Patients in Remissionc Patients who completed the OLE received a mean of four treatments, with 63.5% (40/63) requiring one to four treatments during the 6 months 2026© GH Research PLC

Initial Remitters n=40 Initial Non-Remitters n=23 Percentage of Patients in Remissionc 10 Remission Rate at 6 Monthsa in OLE Completersb a‘6 Months’ or ‘Month 6’ (end of trial) was at approximately 6 months post-study start (median 168 days from Day 1 of double-blind part). bIncludes 63 patients who completed the 6-month OLE per protocol (18 patients terminated early are excluded). cRemission defined as a MADRS total score ≤10. Abbreviations: MADRS = Montgomery-Åsberg Depression Rating Scale; OLE = Open-label extension. 2026© GH Research PLC Patients in remission on Day 8 after their first active treatment had a 90% remission rate at 6 Months. 43.5% of the patients not in remission on Day 8 after first active treatment were in remission at 6 Months.

GH001 Treatment visits in 6 months 4 visitsa 23 visitsc,d 73.0% remission at 6 monthsb 83% Fewer Treatment Visits with GH001 than with Spravato® Note: To-date, no head-to-head comparisons of any other products to any of our product candidates have been completed in any clinical trial; results have been obtained from different trials with different designs, endpoints, and patient populations; results may not be comparable. aFour GH001 visits deduced from the mean total number of treatments received by patients who completed the OLE and were in remission at 6-months of the GH001-TRD-201 trial. b‘6 months’ (end of trial) was at approximately 6 months post-study start (median 168 days from Day 1 of double-blind part). cSPRAVATO® Assumes 23 treatment visits, as per standard initiation protocol of eight and four sessions in Months 1 and 2, respectively, and ICER assumed maintenance treatment frequency of 2.86 treatments per month for Months 3-6.1,2,3 dRemission defined as MADRS ≤10; Spravato® 32-Week remission rates from ESCAPE-TRD trial were 49.1% remission at 32 weeks (55.0% with LOCF method)4. Abbreviations: ICER = Institute for Clinical and Economic Review; LOCF = Last observation carried forward; MADRS = Montgomery-Åsberg Depression Rating Scale; OLE = Open-label extension; TRD = Treatment-resistant depression. 1. Johnson & Johnson Spravato Access, Coding and Reimbursement Guide. 2. ICER Spravato® Final Evidence Report. 3. Janssenscience.com, Dosage and Administration of Spravato, Duration of Therapy. 4. Reif et al. New Engl J Med 2023. Four visitsa 73% remission at 6 monthsb,d 2026© GH Research PLC SPRAVATO® Based on ICER estimate 11

Median Duration of the Psychoactive Experience of 11 minutes (Double-Blind & OLE treatments) Note: To-date, no head-to-head comparisons of any other products to any of our product candidates have been completed in any clinical trial; results have been obtained from different trials with different designs, endpoints, and patient populations; results may not be comparable. aAssumption of BPL-003 duration of ~90min psychoactive phase from Phase 1 SDI results as reported in Rucker et al., 2024. bVLS-01 duration of 90-120 minutes psychoactive experience from Phase 1b results, mean SIRS scores graph, (atai Life Sciences Corporate Presentation, October 2025). cCOMP360 duration of ~6h from Compass Pathways website, which states “The psilocybin experience typically lasts 6 to 8 hours”. Abbreviations: h = Hours; min = Minutes; OLE = Open-label extension; SDI = Subjective drug intensity; SIRS = Subjective Intensity Rating Scale; TRD = Treatment-resistant depression. 12 2026© GH Research PLC GH001 2h 3h 4h 5h 6h BPL-003a VLS-01b COMP360c 11 min median 1h Duration of Psychoactive Experience (approximate average) 45-90min 90-120min 6-8 hours 7h 8h

Abbreviations: OLE = Open-label extension; SAE = Serious adverse event; TEAE = Treatment-emergent adverse event. Safety in Double-Blind and Open-Label Extension 2026© GH Research PLC All patients completed the double-blind part and automatically transitioned to the OLE No TEAEs of suicidal intent or suicidal behavior occurred Across the double-blind and OLE, patients were deemed discharge ready by 1 hour from dose administration at 99% of treatment visits (>250 GH001 treatments in 81 patients) There were no treatment-related SAEs during the 6-month duration of the trial. 13

MADRS reduction in the Placebo group following first active treatmenta after entering the OLE, was comparable to the results observed in the GH001 group in the DB part, showing reproducibility of effects. OLE data shows GH001 leads to a consistent and rapid reduction in MADRS after each GH001 treatment, as in the DB part Double-blind GH001 active group (n=40) OLE Placebo group (n=41) first GH001 active treatment Mean (±SE) MADRS Total Score BL 2 hours Day 2 Day 8 BL 2 hours Day 2 Day 8 Reproducibility of MADRS Reduction Demonstrated in Phase 2b Trial aAn active treatment refers to treatment with GH001. Abbreviations: BL = Baseline; DB = Double-blind; MADRS = Montgomery-Åsberg Depression Rating Scale; OLE = Open-label extension; PBO = Placebo; SE = Standard error; SEM = Standard error of mean. All patients enrolled in the DB part of the trial directly transitioned into the OLE at the end of the DB period. Once a patient completed the Day 8 visit of the DB part, if re-treatment criteria were met, a GH001 treatment could be administered. All patients allocated placebo in the DB part received at least one treatment with GH001 in the OLE. 14 2026© GH Research PLC

Potential Value-Add for GH001 in TRD Best in Therapeutic Category (TRD) Efficacy: Pbo-adj MADRS Δ of -15.5 with GH001 vs -6.8 with Spravato monotherapya vs ~-4 with oral ADb Length of PsE: Median of 11 mins with GH001 vs ~1.5 hours with Spravatoc No additional psychotherapy/therapist visits with GH001; 83% fewer treatment visits with GH001 than with Spravatod Best in Class (Psychedelics) Efficacy: Pbo-adj MADRS Δ of -15.5 with GH001 vs -3.6 with COMP360 (Phase 3 data)e Length of PsE: Median of 11 mins with GH001 vs 6-8 hours for COMP360g vs 45-90 mins for BPL-003f No additional psychotherapy/therapists visits with GH001 Best in Molecule (Mebufotenin; 5-MeO-DMT) Efficacy: Day 8 remission rate of 57.5% with GH001 vs 26% with BPL-003 8 mg doseh Length of PsE: Median of 11 mins with GH001 vs 45-90 mins for BPL-003f No additional psychotherapy/therapists visits with GH001 Note: To-date, no head-to-head comparisons of any other products to any of our product candidates have been completed in any clinical trial; results have been obtained from different trials with different designs, endpoints, and patient populations; results may not be comparable. While Spravato has been approved by the FDA, GH001 has not been approved by the FDA or any other regulatory authority. aSpravato® monotherapy data for 84mg dose from TRD4005 trial, presented at ECNP 2024. bAuvelity, data at Week 6 GEMINI trial, Iosifescu et al., 2022. cDissociative effects/perceptual disturbances, Popova et al., Am J Psychiatry 2019. dAssumes 23 treatment visits, as per standard initiation protocol of 8 & 4 sessions in Months 1 and 2, respectively, and ICER assumed maintenance treatment frequency of 2.86 treatments per month for Months 3-6. See slide 11. eCompass Pathways press release June 23, 2025. fBPL-003 duration assumption from Phase 1 SDI results as reported in Rucker et al., 2024. gCOMP360 duration assumption from Compass Pathways website, which states “The psilocybin experience typically lasts 6 to 8 hours”. hAtai Corporate Deck, July 2025. Abbreviations: ICER = Institute for Clinical and Economic Review; MADRS = Montgomery-Åsberg Depression Rating Scale; PsE = Psychoactive effect; SDI = Subjective drug intensity; TRD = Treatment-resistant depression; AD = antidepressant; Pbo-adj = placebo-adjusted. 15 2026© GH Research PLC

Three-Layer Protection Strategy 16 LAYER 1: REGULATORY EXCLUSIVITY FDA: 5 years (+2.5 years paragraph IV stay) EMA: 10 years (+1 year for new indication) LAYER 2: PATENTS Granted patents and patent applications relating to mebufotenin, including: Novel uses in various disorders (including inhaled, nasal, buccal, sublingual, i.v., i.m., s.c. routes) Novel aerosol compositions of matter Novel manufacturing methods and novel salt forms Novel device-related aspects LAYER 3: TECHNICALComplex bioequivalence for systemically-acting inhalation/intranasal products with high intra- and inter-subject variability Abbreviations: EMA = European Medicines Agency; FDA = Food and Drug Administration; i.v. = Intravenous; i.m. = Intramuscular; s.c. = Subcutaneous. 2026© GH Research PLC

Phase 2b Trial Unprecedented Efficacy in TRD Positioning GH001 as potentially practice-changing GH001 Key Milestones Achieved and Next Steps Pivotal Phase 3 Program Designed in line with the FDA Guidelines and to replicate the Phase 2b data Global Phase 3 start in 2026 17 >> Abbreviations: TRD = Treatment Resistant Depression; IND = Investigational New Drug; FDA = Food and Drug Administration 2026© GH Research PLC