Korro Bio Initiates Phase 1/2 Clinical Trial for KRRO-121

CAMBRIDGE, Mass., Oct. 05, 2026 /CourierPR/ -- Korro Bio, Inc., a clinical-stage biopharmaceutical company, has initiated a Phase 1/2 clinical trial for its GalNAc-conjugated RNA-editing oligonucleotide, KRRO-121. The trial, part of a global program called ANCHOR (AssessmeNt of Control of Hyperammonemia through Oligonucleotide-based RNA editing), is aimed at evaluating the safety, tolerability, pharmacokinetics (PK), and clinical activity of KRRO-121 in both healthy volunteers and patients with urea cycle disorders (UCDs) and hepatic encephalopathy (HE).

The first cohort of the trial, which began enrolling healthy volunteers in Australia, has already received a single dose of 2 mg/kg of KRRO-121. This initial phase is designed to assess safety and tolerability in healthy participants. The trial is expected to start dosing UCD patients in the first half of 2027, with an interim readout anticipated in the second half of the same year.

ANCHOR consists of two parts. The first part, which started in September 2026, involves a Phase 1 single ascending dose (SAD) study followed by a multiple ascending dose (MAD) study of KRRO-121 and placebo in healthy volunteers. This portion of the trial is expected to enroll up to 50 participants and will be placebo-controlled (www.clinicaltrials.gov (NCT07773246)).

The second part of the ANCHOR program will evaluate KRRO-121 in patients with UCDs. This Phase 2 multiple dose study is anticipated to enroll up to 15 participants with UCDs across all genotypes, with dosing expected to start in the first half of 2027. The primary goals of this part of the trial are to assess safety, tolerability, PK, and clinical activity.

KRRO-121 is designed to generate a stabilized, de novo glutamine synthetase (GS) protein, a critical enzyme involved in ammonia clearance. This synthetic rescue approach aims to augment ammonia clearance in hyperammonemia-driven diseases such as UCDs and HE. Preclinical data support the potential for KRRO-121 to be a pan-UCD treatment that may control ammonia levels, potentially enabling diet liberalization, reducing dependence on nitrogen scavengers, and lowering the risk of hyperammonemic crises.

Korro Bio, leveraging its oligonucleotide promoted editing of RNA (OPERA®) platform, is advancing KRRO-121 as a potential first-in-class, disease-modifying therapy for both UCDs and HE. The company’s CEO, Ram Aiyar, PhD, expressed hope that the trial would provide evidence on the safety and activity of KRRO-121, potentially offering a new treatment option for patients with UCDs, irrespective of their mutational background.

The trial is expected to provide valuable insights into the potential of KRRO-121 to address the challenges faced by UCD patients, who often live with the constant fear of hyperammonemic crises. The results from this trial could mark a significant step forward in the treatment of these rare and highly prevalent diseases.