Korro Bio, Inc. (Nasdaq: KRRO) announced that the European Medicines Agency (EMA) Committee has granted orphan drug designation for KRRO-110, the company's investigational RNA editing therapy for Alpha-1 Antitrypsin Deficiency (AATD). This regulatory milestone follows a similar designation from the U.S. Food and Drug Administration received in March 2025.
"The EMA orphan drug designation for KRRO-110 is a significant milestone for Korro and highlights an urgent need to bring innovative solutions to people with AATD seeking new, disease-modifying therapies," said Kemi Olugemo, MD, Chief Medical Officer at Korro. "Backed by encouraging preclinical data, KRRO-110 has best-in-class potential for the treatment of AATD. This designation represents an important step toward bringing KRRO-110 to European patients."
Novel RNA Editing Approach
KRRO-110 represents the first RNA editing oligonucleotide product candidate from Korro's proprietary RNA editing platform, Oligonucleotide Promoted Editing of RNA (OPERA®). The therapy is designed to co-opt an endogenous enzyme, Adenosine Deaminase Acting on RNA (ADAR), to edit the "A" variant on SERPINA1 RNA, repair an amino acid codon, and restore secretion of normal AAT protein.
This repair mechanism has the potential to clear protein aggregates from within liver cells to create a potentially clinically differentiated benefit for liver function and to preserve lung function by providing an adequate amount of normal AAT protein.
Clinical Development Progress
KRRO-110 is currently being evaluated in the Phase 1/2a REWRITE clinical study, a two-part single and multiple dose-escalating trial that will assess safety and tolerability in up to 64 participants, including healthy adults and clinically stable AATD patients with the PiZZ genotype. Secondary and exploratory endpoints include pharmacokinetic and pharmacodynamic parameters that will guide optimal dose selection for later stage studies.
Interim data from Part 1, which involves single ascending doses in healthy volunteers and individuals with AATD, is expected in the second half of 2025. Completion of the full study is anticipated in 2026.
Understanding Alpha-1 Antitrypsin Deficiency
AATD is a genetic disorder most commonly caused by a single missense mutation (G-to-A) in the SERPINA1 gene. Affected adults experience pulmonary emphysema and/or hepatic cirrhosis, as well as end organ manifestations. The EMA grants orphan designation status to medicines intended for the treatment, prevention or diagnosis of life-threatening or chronically debilitating diseases affecting fewer than 5 in 10,000 people in the European Union.
Regulatory Advantages
The orphan drug designation provides Korro with various development incentives, including protocol assistance, reduced regulatory fees, and market exclusivity once the medicine is approved. These benefits are designed to encourage development of treatments for rare diseases where commercial incentives may be limited.
Korro is a clinical-stage biopharmaceutical company focused on developing genetic medicines based on editing RNA for both rare and highly prevalent diseases. The company's approach of editing RNA instead of DNA aims to expand the reach of genetic medicines by delivering additional precision and tunability, which has the potential for increased specificity and improved long-term tolerability.
