1 Corporate Presentation GH Research PLC (NASDAQ: GHRS) GH Research May 2022 2022© GH Research PLC

Disclaimer Regarding Forward-Looking Statements This presentation has been prepared by GH Research PLC (“GH Research”) for informational purposes only and not for any other purpose. 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 these 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. 2 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. 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 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. 2022© GH Research PLC

Seeking Ultra-Rapid, Durable Remissions in Depression 3 2022© GH Research PLC

Pipeline 4 2022© GH Research PLC Stage of Development PROGRAMS INDICATION PRECLINICAL PHASE 1 PHASE 2a PHASE 2b PHASE 3 Next Stage GH0015-MeO-DMT for inhalation administration Treatment-Resistant Depression (TRD) Initiate Phase 2b trial in TRD (GH001-TRD-201) Bipolar II Disorder (BDII)* Initiate Phase 2a trial in BDII(GH001-BD-202) Postpartum Depression (PPD)* Initiate Phase 2a trial in PPD(GH001-PPD-203) GH002 / GH0035-MeO-DMT for injection / intranasal administration Psychiatric or Neurological Disorder Complete preclinical development Complete *In light of our completed Phase 1 clinical trials of GH001 in healthy volunteers and our completed Phase 1/2 trial in TRD, we recently submitted clinical trial applications to begin two Phase 2a trials in patients with BDII and a current major depressive episode and in patients with PPD, respectively. We believe that we can proceed to Phase 2a trials for these two indications based on existing preclinical and clinical data for GH001.

... Remission Rates in TRD < 15% Established Therapies are Slow-Acting ~33% no remission despite 4 treatment steps Adapted from Trivedi et al., Am J Psychiatry 2006 and Rush et al., Am J Psychiatry 2006 Average time to remission is ~6 weeks (STAR*D study, Remission Rate Over Time, Treatment Step 1 = Citalopram) The Problem for Patients with Depression (STAR*D study, Remission Rates Treatment Steps 1 to 4) 5 2 or more prior therapies = TRD 2022© GH Research PLC

Large and Open Depression Market in the EU and US 6 First Line MDD Second Line MDD Treatment-Resistant Depression (TRD) Patients cycle through ineffective therapies for TRD Diagnosed: ~48M Treated (pharmacotherapy ± psychotherapy): ~24M Non-response to first line: ~13M Non-response to two prior lines: ~9M Company estimates based on: https://www.nimh.nih.gov/health/statistics/major-depression.shtml; Wittchen et al., The size and burden of mental disorders and other disorders of the brain in Europe 2010, European Neuropsychopharmacology (2011); Rush et al., Acute and Longer-Term Outcomes in Depressed Outpatients Requiring One or Several Treatment Steps: A STAR*D Report, Am J Psychiatry 2006MDD, Major Depressive Disorder 2022© GH Research PLC

5-MeO-DMT (5-Methoxy-N,N-Dimethyltryptamine) Naturally-occurring psychoactive substance from tryptamine class Highly potent agonist on 5-HT1A and 5-HT2A receptors Psychoactive effects with ultra-rapid onset (within seconds) and short duration (5 to 30 min) High propensity to induce peak experiences (PE), which may be a surrogate marker for therapeutic effects GH001 (5-MeO-DMT administration via a proprietary inhalation approach) Intraday individualized dosing regimen for maximization of ultra-rapid remissions Single visit initial treatment, with no structured psychotherapy Potential for convenient and infrequent retreatment 5-MeO-DMT and GH001 7 2022© GH Research PLC 5-MeO-DMT Foundational IP

GH001 Single Dose: GH001 Individualized Dosing Regimen (IDR): More Chances for Remission MADRS score MADRS score MADRS score MADRS score Dose 1 Dose 1 Dose 2 Dose 3 Dose 2 Dose 1 No remission Remission Remission Remission Remission Hypothetical Patient 1 Hypothetical Patient 2 Hypothetical Patient 3 Hypothetical Patient 1 Hypothetical Patient 2 No remission No remission No remission Dose 1 GH001 – Individualized Dosing Regimen (IDR) Designed to Achieve Ultra-Rapid and Durable Remissions 8 2022© GH Research PLC MADRS score Dose 1

Phase 1 Trial in Healthy Volunteers GH001-HV-101 (Completed) 9 Clinicaltrials.gov ID NCT04640831 2022© GH Research PLC

GH001 Administration Day 1 Day 7 GH001 2 mg (n=4) GH001 6 mg (n=6) GH001 12 mg (n=4) GH001 18 mg (n=4) HV (n=18) Part A (Single Dose) Part B (IDR) Primary Endpoint: Safety until day 7 Peak Experience Scale (PE Scale)1 HV (n=4) Primary Endpoint: Safety until day 7 Peak Experience Scale (PE Scale)1 GH001 IDR6, 12, 18 mg to achieve PE (up to 3 doses, 3h interval) Key Assessments Safety PE Scale Cognitive function Safety Safety Cognitive function 1The PE Scale averages answers scored by the subject by marking a visual analogue scale between 0 and 100 for the following three questions: 1. How intense was the experience; 2. To what extent did you lose control; 3. How profound (i.e., deep and significant) was the experience? Design of Phase 1 Trial in Healthy Volunteers (GH001-HV-101) 10 2022© GH Research PLC PE, Peak ExperienceIDR, Individualized Dosing Regimen

Study Safety Group review No SAEs All ADRs mild, except two moderate (*) All ADRs resolved spontaneously Inhalation well-tolerated No noteworthy changes in vital parameters, except for temporary, non-clinically relevant increase in heart rate and blood pressure shortly after administration of GH001 No clinically significant changes in safety laboratory analyses, psychiatric safety assessments or measures of cognitive function ADRs Part A (Single Dose) Part B (IDR) ADRs 2 mg (N=4) 6 mg (N=6) 12 mg (N=4) 18 mg (N=4) IDR1 (N=4) MedDRA Preferred Term n n n n n Abnormal dreams 1 Anxiety 1 1 Clumsiness 1 Confusional state 1 Euphoric mood 1 Fatigue 1 1* Feeling hot 1 Flashback 1 Hallucination 1 Head discomfort 1 Headache 2 1 1 Heart rate increased 1* Hyperacusis 1 Insomnia 1 Mental fatigue 1 Nausea 2 1 1 2 Vision blurred 1 Part A (Single Dose) and Part B (IDR) – Safety 11 Adverse Drug Reaction, or ADR, an adverse event with a relationship code to the investigational product of definite, probable, or possible, or where code is missingIDR, Individualized Dosing Regimen 2022© GH Research PLC 16 mg (N=1); 6-12 mg (N=2); 6-12-18 mg (N=1)

Average fordose group PE Scale PEThreshold Part A – Peak Experience (PE) Dose-Effectsand Inter-Person Variability 12 PE, Peak Experience 2022© GH Research PLC

PEThreshold Part B – Peak Experience (PE)Effect of Intraday Individualized Dosing Regimen 13 PE, Peak Experience 2022© GH Research PLC

Phase 1/2 Trial in Treatment-Resistant Depression GH001-TRD-102 (Completed) 14 Clinicaltrials.gov ID NCT04698603 2022© GH Research PLC

Key Assessments MADRS 2-hrs PE Scale Safety MADRS 1-day Cognitive function Safety MADRS 7-day Cognitive function Safety GH001 Administration Day 1 Day 7 Design of Phase 1/2 Trial in TRD (GH001-TRD-102) 15 PE, Peak Experience; MADRS, Montgomery-Åsberg Depression Rating ScaleIDR, Individualized Dosing Regimen 1Defined as inadequate response to at least two adequate courses of pharmacological therapy or one adequate course of pharmacological therapy and at least one adequate course of evidence-based psychotherapy 2022© GH Research PLC Phase 1 (Single Dose) Phase 2 (IDR) GH001 12 mg (n=4) GH001 18 mg (n=4) TRD1 (n=8) Primary Endpoint: Safety until day 7 TRD1 (n=8) Primary Endpoint: MADRS remission day 7 (MADRS≤10) GH001 IDR6, 12, 18 mg to achieve PE (up to 3 doses, 3h interval)

Phase 1 (Single Dose) and Phase 2 (IDR) – Safety 16 Adverse Drug Reaction, or ADR, an adverse event with a relationship code to the investigational product of definite, probable, or possible, or where code is missingIDR, Individualized Dosing Regimen; C-SSRS, Columbia-Suicide Severity Rating Scale 2022© GH Research PLC Study Safety Group review No SAEs All ADRs mild, except three moderate* All ADRs resolved spontaneously Inhalation well-tolerated No noteworthy changes in vital parameters, except for temporary, non-clinically relevant increase in heart rate and blood pressure shortly after administration of GH001 No clinically significant changes in safety laboratory analyses, psychiatric safety assessments or measures of cognitive function No safety signal relating to suicidal ideation or suicidal behavior, based on C-SSRS and MADRS subscore item “suicidal thoughts” ADRs Phase 1 (Single Dose) Phase 2 (IDR) ADRs 12 mg (N=4) 18 mg (N=4) IDR1 (N=8) MedDRA Preferred Term n n n Abdominal discomfort 1 Anxiety 2 Depressive symptom 1* Dizziness 1 Feeling abnormal 1 1 Flashback 1 1 2 Headache 2 1 3 Muscle discomfort 1 Muscle spasms 1 Nausea 2* Paresthesia 1 Sensory disturbance 3 16-12 mg (N=6); 6-12-18 mg (N=2)

MADRS Remission / Response / Improvement Rate Day 7 Phase 1 (Single Dose) – Efficacy (MADRS) 17 PE, Peak Experience; MADRS, Montgomery–Åsberg Depression Rating ScaleMADRS remission = MADRS of ≤10; MADRS response = Reduction of ≥50% from baseline in MADRS. 2022© GH Research PLC 2 of 4 (50%) in the 12 mg group and1 of 4 (25%) in the 18 mg group had a MADRS remission at day 7 2 of 8 patients had a PE and both had a MADRS remission at day 7

Phase 2 (IDR) – Efficacy (MADRS) 18 2022© GH Research PLC MADRS Remission / Response / Improvement Rate Day 7 Primary endpoint met: 7 of 8 patients (87.5%) had a MADRS remission at day 7, p<0.0001 7 of 8 patients had a PE and 6 of those had a MADRS remission at day 7 PE, Peak Experience; MADRS, Montgomery–Åsberg Depression Rating ScaleMADRS remission = MADRS of ≤10; MADRS response = Reduction of ≥50% from baseline in MADRS.

Phase 2 (IDR) – Efficacy (MADRS Change from Baseline) 2022© GH Research PLC Baseline1 2 hours Day 1 Day 7 GH001 19 p=0.0018 p<0.0001 p<0.0001 Primary endpoint met: 7 of 8 patients (87.5%) had a MADRS remission at day 7, p<0.0001 7 of 7 remissions from day 1 and5 of 7 remissions from 2 hours 1Baseline mean MADRS=32

MADRS and PE – Observed Improved Outcome in Phase 2 (IDR) vs Phase 1 (Single Dose) Phase 2 (IDR) Phase 1 (Single Dose) 12 mg Phase 1 (Single Dose) 18 mg MADRS Remission Rate Day 7 87.5% (7 of 8) 50% (2 of 4) 25% (1 of 4) Mean MADRS Change Day 7 -24.4 (-76%) -21.0 (-65%) -12.8 (-41%) Rate of PE 87.5% (7 of 8) 50% (2 of 4) 0% (0 of 4) Mean PE Score 90.4 (at final dose) 58.2 59.1 2022© GH Research PLC 20 PE, Peak Experience; MADRS, Montgomery-Åsberg Depression Rating ScaleIDR, Individualized Dosing Regimen

GH001 Administration Day 7 GH001 6 mg (n=8+2 placebo) GH001 12 mg (n=8+2 placebo) GH001 18 mg (n=8+2 placebo) HV (n=30) Single-Dose Part IDR Part HV (n=16) GH001 IDR6, 12, 18 mg to achieve PE (up to 3 doses, 1h interval, n=8) Key Assessments Safety Pharmacokinetics PE Scale Cognitive function Safety Cognitive function Safety 22 Day 30 GH001 IDR6, 12, 18 mg to achieve PE (up to 3 doses, 2h interval, n=8) Primary Endpoint: Pharmacokinetic profile of 5-MeO-DMT and bufotenine 2022© GH Research PLC Design of Phase 1 Clinical Pharmacology Trial in Healthy Volunteers (GH001-HV-103) PE, Peak ExperienceIDR, Individualized Dosing Regimen

Safety Review No SAEs All ADRs mild All ADRs resolved spontaneously Inhalation well-tolerated No noteworthy changes in vital parameters, except for temporary, non-clinically relevant increase in heart rate and blood pressure shortly after administration of GH001 No clinically relevant changes in ECG, safety laboratory analyses, peak flow, cognitive function, psychiatric safety assessments, including the C-SSRS Further Results Pharmacokinetic analyses and psychoactive effect assessments (PE Scale) support that an interval down to 1 hour between individual doses of the IDR is feasible for future clinical trials Single Dose and IDR – Safety and Further Results 23 Adverse Drug Reaction, or ADR, an adverse event with a relationship code to the investigational product of definite, probable, or possible, or where code is missingIDR, Individualized Dosing Regimen; C-SSRS, Columbia-Suicide Severity Rating Scale; PE, Peak Experience 2022© GH Research PLC ADRs Single-dose IDR 6 mg (N=8) 12 mg (N=8) 18 mg (N=8) Placebo (N=6) 1h interval (N=8)2 2h interval (N=8)3 MedDRA Preferred Term n n n n n n Abnormal dreams 1 Chest discomfort 1 Crying 2 2 Dizziness 1 Dry mouth 1 Dyskinesia 1 Fatigue 1 2 1 Headache 3 1 1 1 Hypoesthesia oral 1 Paresthesia oral 1 Retching 1 Somnolence 1 Tachycardia 2 Tension 1 Tremor 1 26 mg (N=1), 6-12 mg (N=3); 6-12-18 mg (N=4)36-12 mg (N=3); 6-12-18 mg (N=5)

LAYER 1: REGULATORY EXCLUSIVITY FDA: 5 years (+2.5 years paragraph IV stay) EMA: 10 years (+1 year for new indication) LAYER 3: TECHNICALComplex bioequivalence for systemically-acting inhalation/intranasal products with high intra- and inter-subject variability LAYER 2: PATENTS Several patent applications filed: Novel aerosol compositions of matter of 5-MeO-DMT Novel manufacturing methods and novel salt forms of 5-MeO-DMT Novel uses of 5-MeO-DMT in various disorders (including inhaled, intranasal, i.v., i.m., s.c., and other routes) Three-Layer Protection Strategy 24 2022© GH Research PLC

Board of Directors & Management 25 Florian Schönharting Michael Forer MSc Chairman of the Board, Co-founder BA, LLB Board Member 2022© GH Research PLC Dermot Hanley Duncan Moore BSC, MBA Board Member MPhil, PhD Board Member Theis Terwey PD Dr. med. CEO, Co-founder Julie Ryan ACA, MAcc, BComm VP, Finance Magnus Halle BSc Managing Director, Ireland, Co-founder

Scientific Advisors 26 Michael Thase M.D. Professor of Psychiatry, Perelman School of Medicine University of Pennsylvania Madhukar Trivedi M.D. Professor of Psychiatry, UT Southwestern Medical Center Mark Zimmerman M.D. Professor of Psychiatry and Human Behavior, Brown University Eduard Vieta Prof. Dr. Head, Psychiatry Unit, Hospital Clínic de Barcelona Michael Bauer Prof. Dr. rer. nat. Dr. med. Chair, Department of Psychiatry and Psychotherapy, Technische Universität Dresden Malek Bajbouj Prof. Dr. med. Head, Center for Affective Neuroscience, Charité, Berlin Johannes Ramaekers Prof. Dr. Professor, Faculty of Psychology and Neuroscience of Maastricht University 2022© GH Research PLC

Anticipated Milestones and Financial Overview GH001 Submit clinical trial applications for multi-center, randomized, controlled Phase 2b trial in TRD in 3Q 2022 Initiate Phase 2a trials in BDII and in PPD in 3Q 2022 Submit U.S. IND for GH001 in TRD not later than 1Q 2023 GH002 and GH003 Complete preclinical development and initiate Phase 1 trial in healthy volunteers Financial Overview Cash was $270.8 million as of March 31, 2022 We believe existing cash will be sufficient to fund operating expenses and capital expenditure requirements into 2025 27 2022© GH Research PLC

Seeking

Ultra-Rapid, Durable Remissions

in Depression