Glasdegib and inotuzumab ozogamicin in B-cell acute lymphoblastic leukemia: Assessing drug responses in a stromal co-culture model

Sonic Hedgehog (SHH) signaling is implicated in B-cell acute lymphoblastic leukemia (B-ALL) and represents a potential therapeutic target. This proof-of-concept study evaluated glasdegib, alone and combined with inotuzumab ozogamicin, in primary B-ALL cells using a stromal co-culture model. Peripheral blood or bone marrow samples from seven patients were co-cultured with HS-5 stromal cells and treated for four days. Viability relative to vehicle controls was assessed using an adenosine triphosphate (ATP)-based luminescence assay after mechanical separation from stromal cells. Expression of four SHH pathway genes was examined by quantitative polymerase chain reaction (qPCR) in four patient samples following treatment with 20 μM glasdegib, with or without 10 ng/mL inotuzumab ozogamicin. Co-culture showed descriptively more stable viability measurements than monoculture, although the between-condition difference in changes in dispersion was not statistically significant (p = 0.154). Glasdegib reduced B-ALL cell viability in a dose-dependent manner by day 4, while HS-5 stromal cells showed negligible sensitivity. Adding inotuzumab ozogamicin did not clearly enhance the response to glasdegib at the tested concentration. Gene expression changes were heterogeneous and inconclusive, with downregulation of selected genes observed in some samples. These preliminary findings support further investigation of glasdegib in B-ALL. Larger studies are needed to determine the value of combination treatment and clarify treatment-associated transcriptional effects.