bay-80-6946 and Leukemia--Myelogenous--Chronic--BCR-ABL-Positive

ABL tyrosine kinase inhibitor (TKI) therapy has improved the survival of patients with Philadelphia (Ph) chromosome-positive leukemia. However, ABL TKIs cannot eradicate leukemia stem cells. Therefore, new therapeutic approaches for Ph-positive leukemia are needed. Aberrant activation of phosphoinositide 3-kinase (PI3K) signaling is important for the initiation and maintenance of human cancers. Copanlisib (BAY80-6946) is a potent inhibitor of PI3Kα and PI3K-δ. Here we investigated the efficacy of combination therapy of copanlisib with an ABL TKI (imatinib, nilotinib, or ponatinib) using BCR-ABL-positive cells. Although the effects of the ABL TKI treatment were reduced in the presence of the feeder cell line, HS-5, copanlisib inhibited cell growth. Upon combining ABL TKI and copanlisib, cell growth was reduced. Ponatinib and copanlisib combined therapy reduced tumor volume and increased survival in mouse allograft models, respectively. These results indicate that the PI3Kα and -δ inhibitors overcame the chemoprotective effects of the feeder cells and enhanced ABL TKI cytotoxicity. Thus, co-treatment with ABL TKI and copanlisib may be a powerful strategy against ABL TKI-resistant cells, including those harboring the related T315I mutation.

Topics: Animals; Antineoplastic Combined Chemotherapy Protocols; Cell Line, Tumor; Cell Proliferation; Drug Resistance, Neoplasm; Drug Synergism; Female; Fusion Proteins, bcr-abl; Humans; Imatinib Mesylate; Imidazoles; K562 Cells; Leukemia, Myelogenous, Chronic, BCR-ABL Positive; Mice; Mice, Inbred BALB C; Mice, Nude; Mutation; Neoplasms, Experimental; Phosphoinositide-3 Kinase Inhibitors; Protein Kinase Inhibitors; Pyridazines; Pyrimidines; Quinazolines