AVROBIO, Inc. reported new safety data from the first lentiviral gene therapy clinical trials for Fabry disease and Gaucher disease, as well as new high-resolution cellular data providing insights into the mechanisms of action of its gene therapies. The data are being presented at the virtual 28th Annual Congress of the European Society of Gene & Cell Therapy (ESGCT), Oct. 19-22, 2021. Fabry disease clinical trial safety data reinforce predictable and generally consistent safety profile New safety data from the first eight adult patients dosed in the Phase 2 FAB-GT trial and the five adult patients dosed in the investigator-sponsored Phase 1 trial show no adverse events (AEs) or serious adverse events (SAEs) related to drug product AVR-RD-01. The AEs and SAEs experienced by trial participants to date in the two trials have been generally consistent with myeloablative conditioning, protocol-mandated drugs, underlying disease or pre-existing conditions. Of all safety events reported to date, 4% were classified as SAEs (n=11), consisting of nausea, vomiting, dehydration, fever, febrile neutropenia and mucosal inflammation, all of which resolved without clinical sequelae. These safety data are from patients in the FAB-GT study with a mean post-gene therapy follow up of 16 months (range: 2-38 months) and the Phase 1 study with a mean post-gene therapy follow-up of 39 months (range: 29-54 months). Safety data from the ninth patient recently dosed in the FAB-GT study are still being analyzed, but preliminary data are consistent with the overall safety profile. With AVROBIOs Bu90-Target Concentration Intervention (TCI) conditioning regimen, patients receive four daily doses of the conditioning agent busulfan, each adjusted to target a cumulative area under the curve of 90 mg x hr/L. This targeted dosing is intended to maximize busulfans ability to make space in the bone marrow for the genetically modified stem cells to engraft, while minimizing the risk of out-of-range toxicity. AVROBIO is also working with clinicians to develop comprehensive care guidelines designed to help gene therapy care teams further proactively mitigate or prevent potential side effects. Six of the 14 Fabry disease patients in the trials have been treated using AVROBIOs proprietary plato® gene therapy platform, which includes a optimized lentiviral vector, proprietary tag technologies, proprietary analytical techniques and Bu90-TCI. The platforms closed, automated manufacturing platform is designed to bring gene therapy to patients worldwide. The safety data cut-off date for the Phase 1 trial was July 26, 2021, and for the FAB-GT trial was Aug. 20, 2021. Gaucher disease type 1 clinical data at 12+ months show no unexpected safety events:- New safety data from the first patient dosed in the Phase 1/2 Guard1 trial of AVR-RD-02 show no SAEs and no AEs to date related to drug product more than 14 months post-treatment. Reported AEs for this patient, who was treated with investigational AVR-RD-02 incorporating key elements of AVROBIOs proprietary plato® gene therapy platform, have been consistent with myeloablative conditioning, protocol-mandated drugs, underlying disease and pre existing conditions. The safety data cut-off date was Aug. 31, 2021.