This clinical trial is focused on studying a treatment for Hemophilia B, a genetic disorder that affects the blood’s ability to clot properly. The study will use a treatment called REGV131-LNP1265, which is a new type of therapy involving a method known as CRISPR/Cas9. This method is designed to help the body produce a protein called clotting factor IX, which is essential for blood clotting. The treatment is given as a solution through an intravenous (IV) infusion, meaning it is delivered directly into the bloodstream.

The purpose of the study is to evaluate the safety and effectiveness of REGV131-LNP1265 in helping the body make clotting factor IX in adults with Hemophilia B. The study is divided into two parts. In the first part, participants will receive a single dose of the treatment to assess its safety and how well it helps the body produce clotting factor IX. In the second part, participants will receive the recommended dose to further evaluate its effectiveness in reducing bleeding events over time.

Participants in the study will be monitored for any side effects and changes in their ability to produce clotting factor IX. The study will also track the rate of bleeding events and the need for additional clotting factor treatments. The trial is expected to last several years, allowing researchers to gather comprehensive data on the long-term effects and benefits of the treatment. This study aims to provide valuable insights into a potential new therapy for managing Hemophilia B.