Haematopoietic gene therapy of non-conditioned patients with Fanconi anaemia-A: results from open-label phase 1/2 (FANCOLEN-1) and long-term clinical trials

Allogeneic haematopoietic stem-cell transplantation is the standard treatment for bone marrow failure (BMF) in patients with Fanconi anaemia, but transplantation-associated complications such as an increased incidence of subsequent cancer are frequent. The aim of this study was to evaluate the safety and efficacy of the infusion of autologous gene-corrected haematopoietic stem cells as an alternative therapy for these patients. This was an open-label, investigator-initiated phase 1/2 clinical trial (FANCOLEN-1) and long-term follow-up trial (up to 7 years post-treatment) in Spain. Mobilised peripheral blood (PB) CD34+ cells from nine patients with Fanconi anaemia-A in the early stages of BMF were transduced with a therapeutic FANCA-encoding lentiviral vector and re-infused without any cytotoxic conditioning treatment. The primary efficacy endpoint of FANCOLEN-1 was the engraftment of transduced cells, as defined by the detection of at least 0·1 therapeutic vector copies per nucleated cell of patient bone marrow (BM) or PB at the second year post-infusion, without this percentage having declined substantially over the previous year. The safety coprimary endpoint was adverse events during the 3 years after infusion. The completed open-label phase 1/2 and the ongoing long-term clinical trials are registered with ClinicalTrials.gov, NCT03157804; EudraCT, 2011–006100–12; and NCT04437771, respectively. There were eight evaluable treated patients with Fanconi anaemia-A. Patients were recruited between Jan 7, 2016 and April 3, 2019. The primary endpoint was met in five of the eight evaluable patients (62·50%). The median number of therapeutic vector copies per nucleated cell of patient BM and PB at the second year post-infusion was 0·18 (IQR 0·01–0·20) and 0·06 (0·01–0·19), respectively. No genotoxic events related to the gene therapy were observed. Most treatment-emergent adverse events (TEAEs) were non-serious and assessed as not related to therapeutic FANCA-encoding lentiviral vector. Nine serious adverse events (grade 3–4) were reported in six patients, one was considered related to medicinal product infusion, and all resolved without sequelae. Cytopenias and viral infections (common childhood illnesses) were the most frequently reported TEAEs. These results show for the first time that haematopoietic gene therapy without genotoxic conditioning enables sustained engraftment and reversal of BMF progression in patients with Fanconi anaemia. European Commission,