Korro Bio Begins Human Testing of RNA-Editing Therapy for Urea Cycle Disorders
Key Points
- Korro Bio dosed the first healthy-volunteer cohort in ANCHOR, its Phase 1/2 trial of KRRO-121.
- Participants in the first cohort received a single 2 mg/kg dose.
- The Phase 1 portion will evaluate safety, tolerability and pharmacokinetics in up to 50 healthy volunteers.
- A planned Phase 2 portion will enroll up to 15 patients with urea cycle disorders across all genotypes, subject to regulatory approval.
- Korro expects patient dosing to begin in the first half of 2027, with an interim readout in the second half of 2027.
Korro Bio (NASDAQ: KRRO) has begun human testing of KRRO-121, an investigational RNA-editing therapy intended to treat hyperammonemia in patients with urea cycle disorders, or UCDs, and hepatic encephalopathy. The first dosing milestone starts the process of assessing safety before the company evaluates potential activity in UCD patients.
ANCHOR Trial Starts With Healthy Volunteers in Australia
The first cohort received a single 2 mg/kg dose of KRRO-121. The trial is currently enrolling healthy volunteers in Australia as part of Korro’s global ANCHOR clinical program.
KRRO-121 is a GalNAc-conjugated RNA-editing oligonucleotide. Korro said preclinical studies involving different mutations showed that the candidate could blunt increases in ammonia levels. Whether those findings translate into benefits for patients remains to be established.
Phase 1 Will Evaluate Single and Multiple Doses
ANCHOR’s Phase 1 portion will assess safety, tolerability and pharmacokinetics—how the body processes the treatment—in up to 50 healthy volunteers.
The single-ascending-dose study will enroll up to 30 participants across as many as five cohorts. A subsequent multiple-ascending-dose study will enroll up to 20 participants across two cohorts. Both portions will be placebo controlled.
UCD Patient Dosing Expected in First Half of 2027
The planned Phase 2 portion will evaluate multiple doses of KRRO-121 in up to 15 UCD patients, subject to regulatory approval. It is designed to include patients across all UCD genotypes and assess safety, tolerability, pharmacokinetics and clinical activity.
Korro expects to begin dosing UCD patients in the first half of 2027 and report interim results in the second half of that year. Although KRRO-121 is also being developed for hepatic encephalopathy, the announced patient portion of ANCHOR focuses on UCDs.
Investor Takeaway: First Dosing Opens the Clinical Evidence Stage
For KRRO investors, first-cohort dosing marks progress from preclinical research into human testing. The next milestones are safety findings, advancement into repeat dosing and the planned start of treatment in UCD patients.
The announcement reports dosing, not clinical results. KRRO-121’s ability to control ammonia levels in patients—and the potential to work across different UCD mutations—must still be demonstrated.
