ET3

**ET3** is an investigational autologous hematopoietic stem-cell gene therapy for hemophilia A developed by Expression Therapeutics. The therapeutic product consists of a patient's CD34+ hematopoietic stem and progenitor cells transduced ex vivo with the self-inactivating lentiviral vector CD68-ET3-LV, which encodes ET3, a bioengineered high-expression F8 transgene. Following myeloablative conditioning and intravenous reinfusion, engrafted cells produce functional coagulation factor VIII under a myeloid-directed CD68 promoter, aiming to provide durable correction of factor VIII deficiency and bleeding protection. A completed Phase 1 study in severe hemophilia A reported stable factor VIII expression and reduced bleeding. ([pmc.ncbi.nlm.nih.gov](https://pmc.ncbi.nlm.nih.gov/articles/PMC6196756/))