Korro Bio, Inc. has achieved a significant milestone with the European Medicines Agency (EMA) granting Orphan Drug Designation for KRRO-110, their promising investigational medicine designed to treat Alpha-1 Antitrypsin Deficiency (AATD). This follows a similar designation received from the U.S. Food and Drug Administration (FDA) in March 2025, underscoring the critical need for novel therapeutic approaches for this rare genetic disorder. AATD, which affects fewer than 5 in 10,000 people in the European Union, is characterized by a specific genetic mutation that leads to severe lung and liver damage.

KRRO-110 is unique in its approach, utilizing Korro's proprietary Oligonucleotide Promoted Editing of RNA (OPERA®) platform. Instead of directly altering DNA, KRRO-110 works by co-opting an endogenous enzyme, Adenosine Deaminase Acting on RNA (ADAR), to precisely edit the mutated RNA. This targeted RNA editing aims to correct the genetic defect at the RNA level, effectively restoring the production of normal alpha-1 antitrypsin protein. By doing so, KRRO-110 has the potential to clear harmful protein aggregates from liver cells, thereby improving liver function, and simultaneously provide sufficient normal protein to protect lung function – offering a potentially transformative, disease-modifying benefit for patients.

The EMA's orphan drug designation is not merely a recognition of unmet medical need; it also provides Korro with a suite of valuable development incentives. These include protocol assistance during clinical development, reduced regulatory fees, and, significantly, 10 years of market exclusivity once the medicine is approved. This support is designed to encourage the development of drugs for rare conditions that might otherwise lack commercial viability.

Currently, KRRO-110 is being evaluated in the Phase 1/2a REWRITE clinical study, a two-part study assessing its safety and tolerability in both healthy adults and AATD patients with the PiZZ genotype. An interim readout of data from Part 1 is anticipated in the second half of 2025, which will provide crucial insights into the drug's performance. The successful progression and potential approval of KRRO-110 could mark a significant advancement in the treatment of AATD, offering hope for patients desperately seeking more effective, disease-modifying therapies beyond existing symptomatic management.