Jose-Luis López-Lorenzo, MD, University Hospital Jimenez Diaz, Madrid, Spain, provides an update on a Phase I clinical trial (NCT04105166) evaluating the safety of RP-L301, an investigational lentiviral gene therapy, in patients with pyruvate kinase deficiency (PKD). Dr López-Lorenzo outlines the study design, which involves the collection of peripheral blood hematopoietic stem cells (HSCs) which are transduced with a lentiviral vector carrying a functional copy of the deficient PKLR gene. Patients then receive a busulfan-containing conditioning regimen and then intravenous infusion of the RP-L301 HSC product. In the first two patients treated, hemoglobin levels were restored to normal levels, both report improved quality of life and no serious adverse events have been attributed to RP-L301. This interview took place at the European Society of Gene & Cell Therapy (ESGCT) Virtual Congress 2021.