Oncogenetic-Driven Targeted Therapy for Relapsed/Refractory T-Cell Acute Lymphoblastic Leukemia : A French ALL-Target Observatory Report

Introduction T-cell acute lymphoblastic leukemia (T-ALL) is an orphan disease diagnosed mostly in adolescent and young adults. In adult population, 5-10% of T-ALL patients (pts) will be primary refractory and 30-40% will relapse. In relapse/refractory (R/R) patients, standard of care treatments, including nelarabine, yield response rate of about 20-40% and responses are of short duration. On behalf of the GRAALL (Group for Research on Adult Acute Lymphoblastic Leukemia), we launched the ALL-TARGET project combining a precision medicine platform dedicated to R/R T-ALL and T-cell lymphoblastic lymphoma (T-LL), and an observatory to evaluate therapeutic proposals based on mutational profile and intracellular signaling pathways alterations. Objectives and methods Leukemic samples from pts with R/R T-ALL/LL were shipped to the GRAALL T-ALL central laboratory in France (V. Asnafi, Hôpital Necker). Biological characterization comprised oncogenetic, phenotypic and in some cases functional analysis. Clinical data from R/R T-ALL/LL pts were collected in a real-life observatory (NCT05832125). Adults pts were eligible if an oncogenetic characterization was available at diagnosis or relapse, and if they received a salvage, either with conventional therapy or with a targeted therapeutic option (TTO). For example, TTOs included Tofacitinib and Venetoclax (Tofa/Ven) in case of IL7R (CD127) expression or IL7R-pathway alterations (IL7R ALT), 5-azacytidine and Venetoclax (Aza/Ven) in case of T-ALL/LL with epigenetic regulators alterations (DNMT3A, ASXL1, PHF6, TET2, PRC2, IDH1/2, SRSF2...) or Temsirolimus, Erwinase and Venetoclax (Tem/Erw/Ven) in case of PI3K signaling pathway alterations (PI3K ALT). The ALL-TARGET Observatory primary endpoint was overall response rate (ORR) including complete remission (CR), CR with incomplete hematological recovery and partial response. We report here the results of the first pts included, with a focus on those who received TTOs as salvage therapy. Results Eighty-nine were analyzed, including 80 T-ALL and 9 T-LL. Sex ratio was 3 and median age at diagnosis was 37.5y, and 51y at the time of the first TTO. Seventy-one pts were in relapse (79.7%) and 18 primary refractory (20.2%). Relapses occurred after a median first CR duration of 16.6 months (range: 2.5-92), with 62.8% in bone marrow, 30% in CNS and 30.3% in other extramedullary sites. Phenotype at diagnosis was available for 68 pts, including 36 Early T-cell Precursor (ETP or near-ETP) (