LAUSR

Blocking BAFF-R early in ALL promotes killing of leukemic cells. However, if given at later disease stages, efficacy is limited due to TGFβ. Combining VAY736 and a TGFβR1 inhibitor improved treatment efficacy in advanced and drug-resistant ALL. Drug-resistant acute lymphoblastic leukemia (ALL) patients do not respond to standard chemotherapy, and an urgent need exists to develop new treatment strategies. Our study exploited the presence of B-cell activating factor receptor (BAFF-R) on the surface of drug-resistant B-ALL cells as a therapeutic target. We used anti–BAFF-R (VAY736), optimized for natural killer (NK) cell–mediated antibody-dependent cellular cytotoxicity (ADCC), to kill drug-resistant ALL cells. VAY736 antibody and NK cell treatments significantly decreased ALL disease burden and provided survival benefit in vivo. However, if the disease was advanced, the ADCC efficacy of NK cells was inhibited by microenvironmental transforming growth factor-beta (TGFβ). Inhibiting TGFβ signaling in NK cells using the TGFβ receptor 1 (R1) inhibitor (EW-7197) significantly enhanced VAY736-induced NK cell–mediated ALL killing. Our results highlight the potential of using a combination of VAY736 antibody with EW-7197 to treat advance-stage, drug-resistant B-ALL patients.