Inotuzumab Ozogamicin (InO) is an antibody-calicheamicin conjugate with striking efficacy in B-cell acute lymphoblastic leukemia (B-ALL). However, there is wide inter-patient variability in treatment response, and the genetic basis of this variation remains largely unknown. Using a genome-wide CRISPR screen, we discovered the loss of DNTT as a primary driver of InO resistance. Mechanistically, DNTT downregulation attenuated InO-induced DNA damage response, cell cycle arrest, and mitochondrial apoptotic priming, ultimately leading to leukemia resistance to InO. Ex vivo leukemia InO sensitivity was highly associated with DNTT expression in ALL blasts, with substantial intra-leukemia heterogeneity as revealed by scRNA sequencing. In B-ALL patients enrolled in the COG trial AALL1621, we observed consistent DNTT downregulation in residual blasts post-InO treatment. The selection of DNTT-low blasts by InO therapy was also recapitulated in vivo using patient-derived xenograft models. Collectively, our data indicate that DNTT is a key regulator of calicheamicin response in leukemia and thus a potential biomarker for individualizing InO therapy in B-ALL.
Copyright © 2024 American Society of Hematology.