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1 1 March 2025 Corporate Presentation November 2025
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2 2 Forward-Looking Statement and Disclaimers Forward-Looking Statements Certain statements in this presentation may constitute “forward-looking statements” within the meaning of the Private Securities Litigation Reform Act of 1995, as amended. Forward-looking statements include, but are not limited to, express or implied statements regarding expectations, hopes, beliefs, intentions or strategies of Korro Bio, Inc. (Korro) regarding the future including, without limitation, express or implied statements regarding: the reasons a single-dose administration of KRRO-110 did not reach protective protein levels in AATD patients; the market opportunity for KRRO-121; the timing of the regulatory filing for KRRO-121; the potential of Korro’s GalNAC- conjugated programs targeting the liver, including KRRO-121 and GalNAc delivery for AATD patients; Korro’s ability to activate a biological pathway with RNA editing; timing of nominating a development candidate for Korro’s GalNAc-conjugated program for AATD; the costs of Korro’s workforce reduction, and the benefits thereof; Korro’s collaboration agreement with Novo Nordisk; and Korro’s cash runway and uses thereof; among others. In addition, any statements that refer to projections, forecasts, or other characterizations of future events or circumstances, including any underlying assumptions, are forward-looking statements. The words “anticipate,” “believe,” “continue,” “could,” “estimate,” “expect,” “intend,” “may,” “might,” “plan,” “possible,” “potential,” “predict,” “project,” “should,” “strive,” “would,” “aim,” “target,” “commit,” and similar expressions may identify forward-looking statements, but the absence of these words does not mean that statement is not forward looking. Forward-looking statements are based on current expectations and assumptions that, while considered reasonable are inherently uncertain. New risks and uncertainties may emerge from time to time, and it is not possible to predict all risks and uncertainties. Factors that may cause actual results to differ materially from current expectations include, but are not limited to, various factors beyond management’s control including risks inherent in biopharmaceutical development; risks associated with pre-clinical studies and conducting clinical trials; risks associated with validating in clinical trials observations from pre-clinical studies; risks associated with collaborating with third parties; other risks associated with protecting intellectual property; as well as risks associated with general economic conditionsand other risks and uncertainties indicated from time to time in Korro’s filings with the SEC, including Item 1A. “Risk Factors” in Korro’s most recent Quarterly Report on Form 10-K or Form 10-Q filed with the SEC, as such may be amended or sup plemented by its other filings with the SEC. Nothing in this presentation should be regarded as a representation by any person that the forward-looking statements set forth herein will be achieved or that any of the contemplated results of such forward-looking statements will be achieved. You should not place undue reliance on forward-looking statements in this presentation, which speak only as of the date they are made and are qualified in their entirety by reference to the cautionary statements herein. Except as required by law , Korro does not undertake or accept any duty to release publicly any updates or revisions to any forward-looking statements to reflect any change in their expectations or in the events, conditions or circumstances on which any such statement is based. This presentation does not purport to summarize all of the conditions, risks and other attributes of an investment in Korro. Industry and Market Data Certain information contained in this presentation relates to or is based on studies, publications, surveys and Korro’s own internal estimates and research. In this presentation, Korro relies on, and refers to, publicly available information and statistics regarding market participants in the sector in which Korro competes and other industry data. Any comparison of Korro to any other entity assumes the reliability of the information available to Korro. Korro obtained this information and statistics from third-party sources, including reports by market research firms and company filings. In addition, all of the market data included in this presentation involve a number of assumptions and limitations, and there can be no guarantee as to the accuracy or reliability of such assumptions. Finally, while Korro believes its internal research is reliable, such research has not been verified by any independent source and Korro has not independently verified the information. Trademarks This presentation may contain trademarks, service marks, trade names and copyrights of Korro or other third parties, which are the property of their respective ow ners. Solely for convenience, some of the trademarks, service marks, trade names and copyrights referred to in this presentation may be listed without the TM, SM © or ® symbols, but Korro will assert, to the fullest extent under applicable law, the rights of the applicable owners, if any, to its trademarks, service marks, trade names and copyrights.
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3 3 1 Cash, cash equivalents and m arketab le securities of $102.5 million as of September 30th, 2025 Encouraged by Evidence of RNA Editing in AATD Patients ▪ KRRO-110 study – REWRITE Phase 1/2a ‒ Produced functional M-AAT in AATD patients ‒ Tolerable safety profile consistent with LNP infusion-related class effects ‒ KRRO-110 did not reach projected levels of functional protein following a single administration ‒ Pharmacokinetic differences in plasma were observed between healthy volunteers and AATD patients ‒ Will evaluate the totality of the clinical data to evaluate the next steps, if any, for multiple doses ▪ Strategic decision to pivot to GalNAc-conjugated delivery for AATD patients ‒ Significant progress seen with GalNAc-conjugated constructs for AATD ‒ Development candidate anticipated in H1 ‘26 ▪ Nominated KRRO-121 with a potential to treat patients with hyperammonemia ‒ A large market opportunity in “pan”-urea cycle disorders (UCD) and hepatic encephalopathy (HE) ‒ GalNAc conjugated construct designed to activate a biological pathway, expanding from protein correction ‒ Regulatory filing expected in H2 ‘26 ▪ Cash runway into H2 ’27
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4 4 Developing Transformative Genetic Medicines for Rare and Highly Prevalent Diseases Editing RNA Without modifying DNA Activating Biological Pathways Learning from genetics Modular Platform Delivering drug to multiple cell types
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5 5 Target RNA Adenosine Inosine ADARADAR Oligo-RNA duplex recruits adenosine deaminase acting on RNA (ADAR) ADAR catalyzes deamination: ‘A’ to ‘I’ edit mRNA translated to protein with ‘I’ read as ‘G’ Resultant therapeutic protein DNA with disease- causing mutation Non-viral intracellular delivery of Korro oligo designed to edit a specific adenosine on the target RNA 1 2 3 4 5 Harnessing an endogenous enzyme, ADAR, expressed in all human cells for a highly specific edit RNA Editing: Transiently Affecting anA-to-I Edit on RNA Using anOligonucleotide
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6 6 DNA Pre-mRNA mRNA Protein Edit a single A-to-I Modifying gene expression Current Focus Edit a single A-to-I • Repair a G->A mutation to correct the protein • Generate a de novo protein with preferred properties (can alter 12 amino acid sequences) TRANSCRIPTION PROCESSING TRANSLATION RNA Editing Enables Potential for High Impact in Broad Range of Disease Areas Human genetics guiding the possibilities
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7 7 Expertise in ADAR biology driving potency and translation Leveraging known Delivery driving derisked access to indications Expertise in Chemistry driving potency and drug designs Expertise in Machine Learning driving efficiency and Target ID OPERA: Our Approach for RNA Editing to GenerateProduct Candidates
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8 CONCEPT PROGRAM / INDICATION DELIVERY DISCOVERY PRECLINICAL DEVELOPMENT PHASE 1 PHASE 2 PHASE 3 Repairing a pathogenic variant KRRO-110 AATD LNP (IV) De novo protein to inhibit degradation KRRO-121 Hyperammonemia GalNAc (SC) Repairing a pathogenic variant AATD GalNAc (SC) De novo protein to overcome LoF and GoF 1 Amyotrophic lateral sclerosis Undisclosed De novo protein to modulate currents Subsets of pain Undisclosed Undisclosed Cardiometabolic Undisclosed AAT Phase 1/2a - Interim data disclosed Reg filing 2H ‘26 TDP43 Pipeline with Multiple Potential High-Value Targets Up to 2 Targets2 1De Novo protein variant to prevent toxic gain of function (GoF) with TDP43 aggregation, and still continue downstream signaling by overcoming toxic Loss-of-function (LOF) 2 Collaboration entered 12-month pause in Nov. 2025 Nav1.7 AAT DC in 1H ‘26
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9 9 KRRO-110 Alpha-1 Antitrypsin Deficiency (AATD)
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10 Note: AAT protein is encod ed b y the gene SERPINA1. The E342K mutation (G to A) in SERPINA1 (Z allele) is the m ost frequent m utation and causes severe lung and liver d isease *Z-AAT not as active as M-AAT **Source: Alpha-1 Foundation. Numbers reflected here are carrier of ZZ genotyp es Minimal inhibition of lung neutrophil elastase Reduced levels of Z-AAT secreted Mutated AAT polymerizes and aggregates in liver cells ZZ Genotype (fibrotic liver and decreased lung function) Normal levels of M-AAT secreted Inhibits neutrophil elastase in the lung M-AAT MM Genotype (normal liver and lung) Z-AAT* ~100K PiZZ adult patients in U.S.** AATD Most Commonly Caused by aSingle Missense (G-to-A) Mutation in SERPINA1 Gene in the Liver
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11 KRRO-110: CHORD Encapsulated inanLNP with Human* Exposure SERPINA1 mRNA Hepatocyte CHORD KRRO-110 PiZZ Liver M-AAT Z-AAT IV DELIVERY ADAR Note: Editing is a function of number of transcripts in each cell. Editing refers to data from preclinical models *LNP contained in KRRO-110 has been dosed in multiple clinical trials A Secreted Z-AAT Polymers In liver LNP Licensed from Genevant Depending on editing levels some Z-aggregates in liverEdited mRNA X 100 Edited + Mutant mRNA % editing =
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12 12 A Phase 1/2a, Two Part, Single- and Multiple-Dose Escalation Study US IND opened, US Fast Track Designation and Orphan Drug Designation in US and EU granted to KRRO-110 for the treatment of patients with AATD 36 Healthy Volunteers (HV) 2:1 - Active: Placebo 8-12 PiZZ AATD Patients Open Label Part 1 = SAD Part 2 = MAD Primary endpoints: Safety and tolerability Secondary endpoints: Total-AAT, M-AAT, and functional anti- protease activity Up to 16 PiZZ AATD Patients (4 per cohort) Open Label Primary endpoints: Safety and tolerability Secondary endpoints: PK, Total-AAT, M-AAT, and functional anti-protease activity Adaptive design: Dose and dosing frequencies
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13 13 Part 1: Single-Dose Escalation Design Up to 1.2 mg / kg in HV 0.04 mg/kg 0.8 Completed dosing 0.2 1.2 0.1 0.8 mg/kg HEALTHY VOLUNTEERS (completed) 0.6 mg/kg 6 HVs / cohort (2:1 randomization) 0.4 Up to 4 patients per cohort (open-label) In progress Cohort 1 Cohort 2 Cohort 3 Cohort 4 Cohort 5 Cohort 6 AATD PATIENTS (ongoing, open label)
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14 14 Observations from the KRRO-110 REWRITE in SAD Key Questions Observation in REWRITE Does RNA-editing work in Humans? M-AAT protein observed in circulation in 3/3 patients evaluable. Production of M-AAT can only be made with repair of the Z -AAT protein. Was it specific and functional? Function was shown to increase from baseline with M -AAT production. No bystander effects observed with LC/MS. Was it durable? Functional M-AAT protein lasted up to four weeks for the first patient evaluable with LC/MS, consistent with durability of editing and endogenous M -AAT protein half-life. Was total AAT detected above 11µM with a single administration? A single administration was not sufficient Multi-dose with sustained exposure to KRRO -110 is likely needed. Was KRRO-110 generally safe across populations? No DLTs were identified, no treatment emergent SAEs Mild-moderate IRRs were detected in 6 individuals at the 0.6 (2 in AATD), 0.8 (2 in AATD) and 1.2 mg/kg (2 in HV) doses. Was there consistency in the Pharmacokinetics (PK) across populations? At higher doses, there were plasma PK differences in the components of KRRO -110 between healthy volunteers and AATD patients. Evaluating the totality of the SAD data to consider next steps for KRRO-110
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15 15 Strategic Decision to Pivot to GalNAc for Liver indications for AATD and beyond Alpha1 GalNAc KRRO-121 Indication AATD Hyperammonemia (pan-UCD & HE) Rare Disease Yes Yes (pan-UCD) - No (HE) Therapeutic approach Mutation correction of a defective gene Protein stabilization of an existing protein Delivery GalNAc GalNAc Target editing efficiency Expected High Expected Low Market Opportunity (US) $3B $2B+ PoC in the Clinic Level of M-AAT in plasma Levels of Ammonia in plasma Next-Wave Programs Offer High Probability of Success Learning from KRRO-110 ▪ What did we learn from REWRITE? ‒ RNA editing works in humans ‒ Consistent/constant repair of the protein is essential ‒ High levels of editing seems to be important ▪ Significant progress made with AATD-GalNAc ‒ Our GalNAc tool constructs more potent than KRRO-110 ‒ Pivot aligns with the opportunity cost
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16 16 KRRO-121 Treating Hyperammonemia
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17 17 Plasma Ammonia Significantly Impacts Pathology Across Multiple Diseases Novel approach to reduction of ammonia could have a profound impact Ammonia Diet & metabolism Normal Clearance Diminished Clearance Normal excretion through kidneys ! Hyperammonemia Source: 3rd party primary market research study and analysis (April 2025); KOL interviews ▪ High ammonia leads to: ‒ Neurological impairment, potentially permanent ‒ Frequent hospitalization ‒ Highly restricted diet ‒ Elevated infection risk ‒ Additional non-neurological complications ▪ Can be caused by cirrhosis or urea cycledysfunction ▪ Clinical studies have shown benefit of loweringammonia in multiple indications
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18 18 KRRO-121: A First Step Away from Correcting an AberrantProtein ▪ GalNAc-conjugated construct to activate an existing biological pathway ‒ Designed to stabilize an intracellular protein involved in ammonia clearance ‒ Creating a protein variant learning from genetics ▪ Intended to treat patients with hyperammonemia ‒ UCD patients irrespective of their enzyme deficiencies in the urea cycle ‒ Patients with hepatic encephalopathy and high plasma ammonia ‒ Large unmet medical need and market opportunity in both populations ▪ Anticipate a regulatory filing in H2 ‘26
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19 19 Positioned for Value Creation in 2026 and Beyond Review next steps for REWRITE post completion of both SAD cohorts with AATD patients Cash runway into H2 20271 enabling multiple milestones above 1 Cash, cash equivalents and m arketab le securities of $102.5 million as of September 30, 2025 Nominated KRRO-121 for patients with hyperammonemia with reg. filing anticipated in H2 ‘26 Progressing a GalNAc-conjugated construct for AATD with DC expected in H1 ‘26
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20 20 Edit the message. Rewrite the future.