• Initiated a Phase 1/2 clinical trial to enroll healthy volunteers and patients with Urea Cycle Disorders of any mutational background 
• Administered a single dose of 2mg/kg to the first cohort of healthy volunteers
• Expected to start dosing in UCD patients in the first half of 2027 with an interim readout expected in the second half of 2027

Korro Bio, Inc. (Korro) (Nasdaq: KRRO), a clinical-stage biopharmaceutical company leveraging its oligonucleotide promoted editing of RNA (OPERA^®) platform to develop a new class of genetic medicines for rare and highly prevalent diseases, announced today that the first cohort of participants has been dosed in its Phase 1/2 clinical trial for KRRO-121, the Company’s GalNAc-conjugated RNA-editing oligonucleotide (REO) in development for the potential treatment of hyperammonemia in patients with urea cycle disorders (UCDs) and patients with hepatic encephalopathy (HE).

“UCD patients and their families live with a constant, low-grade fear that a stomach bug, a skipped dose of a nitrogen scavenger or just the wrong meal could trigger a hyperammonemic crisis. In multiple preclinical studies with different mutations, KRRO-121 has demonstrated the ability to blunt ammonia excursions,” said Ram Aiyar, PhD, Chief Executive Officer and President of Korro. “Dosing the first cohort in ANCHOR is a step towards gaining evidence on safety first and then activity. Providing the potential for peace of mind for patients with a UCD, irrespective of their mutational background, is something we hope to demonstrate through this trial. I would like to thank all the stakeholders involved in making this possible and working with us to provide options for patients living with UCD.”

This trial is currently enrolling healthy volunteers in Australia and is part of a global Phase 1/2 clinical trial program entitled ANCHOR (AssessmeNt of Control of Hyperammonemia through Oligonucleotide-based RNA editing). ANCHOR consists of two components:

1. Part 1: Comprises a Phase 1 single ascending dose (SAD) study to be followed by a multiple ascending dose (MAD) study of KRRO-121 and placebo in healthy volunteers to evaluate safety, tolerability and pharmacokinetics (PK) in up to 50 participants; and
    
2. Part 2: Comprises a Phase 2 multiple dose study of KRRO-121 in up to 15 participants with UCD across all UCD genotypes to assess safety, tolerability, PK and clinical activity subject to regulatory approval

The SAD part of Korro’s Phase 1 clinical trial will enroll up to 30 healthy volunteers in up to five cohorts, with the MAD portion enrolling up to 20 subjects across two cohorts. Both the SAD and the MAD portions will be placebo controlled (www.clinicaltrials.gov (NCT07773246)).