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245 130 32 33 81 132 132 134 132 0 162 214 206 73 9 232 21 96 Lead In Vivo Development Candidate Webinar September 2, 2025
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Forward Looking Statements This presentation contains forward-looking statements and information within the meaning of The Private Securities Litigation Reform Act of 1995, including statements regarding the potential market for EDIT-401, if approved. The words ‘‘anticipate,’’ ‘‘believe,’’ ‘‘continue,’’ ‘‘could,’’ ‘‘estimate,’’ ‘‘expect,’’ ‘‘intend,’’ ‘‘may,’’ ‘‘plan,’’ ‘‘potential,’’ ‘‘predict,’’ ‘‘project,’’ ‘‘target,’’ ‘‘should,’’ ‘‘would,’’ and similar expressions are intended to identify forward-looking statements, although not all forward-looking statements contain these identifying words. Forward-looking statements in this presentation include statements regarding the initiation, timing, progress and results of the Company’s preclinical studies and its research and development programs, including the Company’s expectation to achieve human proof-of-concept data for EDIT- 401 by end of 2026 and identify and disclose an additional target cell type or tissue by the end of 2025; the potential of, and expectations for, EDIT-401; the timing or likelihood of regulatory filings and approvals, including submission of an IND or CTA for EDIT-401 by mid-2026; and the Company’s expectations regarding its cash runway. The Company may not actually achieve the plans, intentions, or expectations disclosed in these forward-looking statements, and you should not place undue reliance on these forward-looking statements. Actual results or events could differ materially from the plans, intentions and expectations disclosed in these forward- looking statements as a result of various important factors, including: uncertainties inherent in the initiation and completion of preclinical studies and clinical trials; availability and timing of results from preclinical studies and clinical trials; expectations for regulatory approvals to conduct trials; that the outcome of preclinical testing may not be indicative of the results of clinical trials and early clinical trials may not be predictive of the outcomes of later clinical trials; that preclinical data of one compound may not be comparable with clinical data for another compound; that the market opportunity for EDIT-401 may not be as significant as the Company expects; and uncertainties with respect to the availability of resources and financing sufficient to fund the Company’s foreseeable and unforeseeable operating expenses and capital expenditure requirements. These and other risks are described in greater detail under the caption “Risk Factors” included in the Company’s most recent Annual Report on Form 10-K, which is on file with the Securities and Exchange Commission, as updated by the Company’s subsequent filings with the Securities and Exchange Commission, and in other filings that the Company may make with the Securities and Exchange Commission in the future. Any forward- looking statements contained in this presentation represent the Company’s views only as of the date hereof and should not be relied upon as representing its views as of any subsequent date. Except as required by law, the Company explicitly disclaims any obligation to update any forward-looking statements. 2
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│Welcome and Strategic Overview │EDIT-401 Overview & Opportunity │Upregulation Strategy & EDIT-401 Preclinical Data │Anticipated Key Milestones & Closing Remarks │Q&A Gilmore O’Neill, MB, MMSc President and Chief Executive Officer SPEAKERS Agenda and Speakers Linda Burkly, P.h.D Chief Scientific Officer 3
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245 130 32 33 81 132 132 134 132 0 162 214 206 73 9 232 21 96 Differentiated Science Strategic Execution Best-in-Class In Vivo Editing Pipeline “Plug ‘n play” in vivo editing enables rapid development of new therapies by simply reprogramming guide RNAs Differentiated upregulation -only strategy unlocks novel therapeutic mechanisms not addressable by traditional gene disruption or correction Solved for delivery using proprietary, targeted LNPs (tLNPs) that allow targeting of multiple tissues Driven management team with a proven track record of drug development and commercialization and focus on execution Strong cash position with operational runway into Q2 2027 4
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245 130 32 33 81 132 132 134 132 0 162 214 206 73 9 232 21 96 EDIT-401: Robust preclinical efficacy data with a ~90% mean reduction of LDL-C1 Potential one-time treatment designed for lifelong benefit Compelling preclinical data supporting rapid progression to human proof-of-concept data by end of 2026 Attractive business model with expected typical biopharma margins 1 Sizeable market potential with favorable health care system economics1 A Potential Best-In-Class, In Vivo Gene Editing Medicine to Transform the Hyperlipidemia Treatment Paradigm LDL-C, low-density lipoprotein cholesterol 1. Editas Medicine. Data on file. 5
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245 130 32 33 81 132 132 134 132 0 162 214 206 73 9 232 21 96 Large Opportunity Across At-Risk Hyperlipidemia Patient Populations ASCVD is the leading cause of death worldwide1 National US expenditures expected to reach over $300 billion by 20352 ~75% of patients with established cardiovascular disease do not achieve LDL-C goals3, 5 Lower LDL-C is well correlated to reduced risk of cardiovascular events1 Standard of care requires multiple therapies and life-long administration1 70 million US patients with hyperlipidemia4 ASCVD HeFH 15M ASCVD not at goal 10M 1.2M ASCVD, atherosclerotic cardiovascular disease; LDL-C, low-density lipoprotein cholesterol; HeFH, heterozygous familial hypercholesterolemia 1. Arnett DK et al. Circulation 2019; 140 (11): e596–e646; 2. Khera R et al. J Am Heart Assoc. 2020;9:e017793; 3. Gu J et al. Am J Prev Cardiol 2022; 10: 100336; 4. Editas Medicine. Data on file. 5. Klimchak AC et al. Am J Prev Cardiol 2020;1:100010 Unmet need across multiple at-risk segments of patients with hyperlipidemia 6
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245 130 32 33 81 132 132 134 132 0 162 214 206 73 9 232 21 96 Statins PCSK9i EDIT-401 Baseline Transformative LDL-C Lowering Potential with EDIT-401 % Reduction Intensively reducing LDL-C long-term provides maximal benefit4,5 KOLs confirm ~90% mean LDL-C reduction would be transformative for the management of hyperlipidemia1 Current Treatments Provide Insufficient Reduction of LDL-C Time Current standard of care has a mean LDL-C reductions of 40- 60%2,3,5,6,7 ~90% mean LDL-C reduction in non- human primates1 LDL-C, low-density lipoprotein cholesterol; KOL, key opinion leader 1. Editas Medicine. Data on file. 2. Arca M et al. J Am Heart Assoc. 2023;12 3. Goldenberg et al. Vascular Health and Risk Management 2009:5 369–376. 4. Cohen et al. N Engl J Med 2006; 354:1264-72 5. Gaba et al. Circulation. 2023; 147(16):1192-1203. 5. Nawrocki JW et al. Arterioscler Thromb Vasc Biology 1995;15:678-682. 6. Robinson JG et al. N Engl J Med 2015; 372:1489- 1499. 7. Koskinas KC et al. J Am Coll Cardiol 2019;74:2452–62. EDIT-401 Uniquely Positioned 7
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245 130 32 33 81 132 132 134 132 0 162 214 206 73 9 232 21 96 Editas’ Differentiated In Vivo Gene Editing Upregulation Strategy Diseases that can be addressed by protein reduction similar to ASO and siRNA Therapeutic strategy Gene Editing approach Non gene Editing modality Patient population All patients (mutation agnostic) Functional upregulation* Knockdown Gene correction siRNA, antisense oligos, monoclonal antibody, and small molecule (pill) Subset of patients (single mutation) Other Approaches Therapeutic potential All patients (mutation agnostic) First/best-in class opportunities for loss of function diseases; cannot be addressed via knockdown Correction limited to subset of all patients with given disease *editing of regulatory region, e.g., 5’ or 3’ region to upregulate a wild type allele or functional homolog to address loss of function or deleterious mutations or or 8
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245 130 32 33 81 132 132 134 132 0 162 214 206 73 9 232 21 96 Therapeutic Strategy for EDIT-401 De-Risked by Human Genetics LDL-C, low-density lipoprotein cholesterol; LDLR, low-density lipoprotein receptor; 3’ UTR, three prime untranslated region 1. Bjornsson et al. Circ Genom Precis Med 2021;14:e003029 No Adverse Impacts on Health1 LDL-C: ➢ 13-72 mg/dL in plasma LDLR: ➢ 1.5–2.5-fold higher surface LDLR Safety: ➢ No adverse events n = 101,857 Icelandic non-carriers Mean plasma LDL-C (mmol/l) ∆ICE carriers 7 Icelandic family members identified as carriers of partial LDLR 3’ UTR deletion1 Plasma LDL-C levels1 3’ UTR deletion carriers 9
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Robust LDL-C Reduction Driven by at Least 6 -Fold Mean Increase in LDLR Protein Upregulation LDLR, low-density lipoprotein receptor; PCSK9, proprotein convertase subtilisin/kexin type 9. References: 1. Editas Medicine. Data on file. 2. https://biocytogen.com/gene-humanized-models/b-hpcsk9-mice. Accessed Aug 29, 2025. 3. Rashid et al. PNAS 2005;102(15): 5374 –5379. 10 Deletion of regulatory elements increases the stability of the LDLR mRNA resulting in increased production of LDLR protein EDIT-401 increased LDLR protein by at least 6-fold mean in preclinical studies1 EDIT-401 Targeting PCSK9 prevents LDLR degradation, resulting in limited increase in LDLR protein2,3 EDIT-401 Therapeutic Strategy for LDLR Upregulation PCSK9
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Integration of multiple unique components has enabled EDIT-401 to achieve ~90% mean LDL-C reduction in preclinical studies LNP, lipid nanoparticle; AE, adverse event; Cas9, CRISPR-associated protein 9; CRISPR, clustered regularly interspaced short palindromic repeats; GalNAc, N-acetylgalactosamine; gRNA, guide RNA; LDL-C, low-density lipoprotein cholesterol; LDLR, low-density lipoprotein receptor; c; mRNA, messenger RNA; RNA, ribonucleic acid; 3′ UTR, three prime untranslated region. GalNAc-Targeted LNP for Liver Delivery • GalNAc targeting moiety enabling delivery if lacking sufficient LDLR • GalNAc-LNP leveraged through strategic partnership with Genevant Gene Target Informed by Human Genetics • Excision of LDLR 3′ UTR segment with Cas9 and dual gRNAs • De-risked strategy – models naturally occurring gain-of-function deletion to lower LDL-C with no AEs LNP Delivery Strategy • Encapsulation of mRNA and gRNAs in a single LNP for transient expression of drug product • Clinically validated LNP components through strategic partnership with Genevant EDIT-401 Combines Editas’ CRISPR and LNP Expertise 11
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LDL-C, low-density lipoprotein cholesterol; LDLR, low-density lipoprotein receptor 1. Editas Medicine. Data on file. Non-human Primates1 EDIT-401 Achieved ~90% Mean LDL-C Reduction in NHPs ✓ No adverse clinical observations noted ✓ Single dose ✓ At least 6-fold mean increase in LDLR protein upregulation ✓ Transient increases in liver enzymes resolved within 1 week Pre-dose LDL-C was averaged across 2 timepoints to account for variability in measurements 12 Pre-dose 24 h 48 h D6 D8 D15 D22 D29 -100 -90 -80 -70 -60 -50 -40 -30 -20 -10 0 10 20 LDL-C (mean % reduction from baseline) Vehicle 2 mg/kg 3 mg/kg 4 mg/kg 1.5 mg/kg ✓ ~90% mean LDL-C reduction at each dose level
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245 130 32 33 81 132 132 134 132 0 162 214 206 73 9 232 21 96 LDL-C, low-density lipoprotein cholesterol; LDLR, low-density lipoprotein receptor 1. Editas Medicine. Data on file. Wild-type Mice on High-Fat Diet1 EDIT-401 Achieved ~90% Mean LDL-C Reduction in Mice with High Baseline LDL-C Mice on a high fat diet had 3 -fold elevated baseline LDL -C compared to mice on a regular fat diet ✓ ~90% mean LDL-C reduction ✓ Single dose ✓ Greater than 10-fold LDLR protein upregulation 0 2 4 6 8 10 12 0 50 100 150 200 250 300 Weeks Post-Dose LDL-C mg/dL Vehicle Edited 13
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245 130 32 33 81 132 132 134 132 0 162 214 206 73 9 232 21 96 Mice Heterozygous for LDLR Loss -of-Function1 EDIT-401 Achieved ~90% Mean LDL-C Reduction in Mice Heterozygous for LDLR Loss -of-Function ✓ ~90% mean LDL-C reduction ✓ Single dose ✓ Greater than 10-fold LDLR protein upregulation 0 1 0 20 40 60 80 100 Weeks Post-Dose LDL-C mg/dL Vehicle Edited Mice heterozygous for LDLR loss -of-function had 2-fold increase in baseline LDL -C LDL-C, low-density lipoprotein cholesterol; LDLR, low-density lipoprotein receptor 1. Editas Medicine. Data on file. 14
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245 130 32 33 81 132 132 134 132 0 162 214 206 73 9 232 21 96 Potential to Deliver Meaningful Benefits Across the Hyperlipidemia Population EDIT-401 achieved ~90% mean LDL-C reduction Non-Human Primates Elevated Baseline LDL-C Heterozygous LDLR Loss of Function LDL-C, low-density lipoprotein cholesterol; LDLR, low-density lipoprotein receptor 1. Editas Medicine. Data on file. 15
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245 130 32 33 81 132 132 134 132 0 162 214 206 73 9 232 21 96 EDIT-401: Editas’ Lead Development Candidate 16 Robust preclinical efficacy data with a ~90% mean reduction of LDL-C1 LDL-C, low-density lipoprotein cholesterol 1. Editas Medicine. Data on file. Potential one-time treatment designed for lifelong benefit Sizeable market potential with favorable health care system economics1 Attractive business model with expected typical biopharma margins1 Preclinical data supports rapid progression to human proof-of-concept data by end of 2026 A potential best-in-class, in vivo gene editing medicine to transform the hyperlipidemia treatment paradigm
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245 130 32 33 81 132 132 134 132 0 162 214 206 73 9 232 21 96 Select Lead In Vivo Candidate in September 2025 Establish One Additional Target Tissue • Disclose further target cell type or tissue by end of 2025 Present In Vivo Preclinical Editing Data Achieve In Vivo Human Proof of Concept Data for EDIT-401 by end of 2026 Expand the Range of Diseases Addressable by In Vivo Gene Upregulation • In vivo proof of concept data in one further cell type/tissue by 2027 2025 2026-2027 Key Anticipated Milestones & Strategic Priorities Selection of EDIT-401 reaffirms our strategic vision to be a leader in in vivo programmable gene editing with a potential best-in-class medicine that could meaningfully impact patients and the healthcare system Submit IND / CTA for EDIT-401 by mid- 2026 17
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18 Questions & Discussion Gilmore O’Neill, MB, MMSc President and Chief Executive Officer Amy Parison Chief Financial Officer Linda Burkly, PhD Chief Scientific Officer