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Two-Drug Synergy Investigated For Treatment Of Drug-Resistant Chronic Myeloid Leukemia

An interdisciplinary team of researchers has dissected a case of in drug-resistant to understand the mechanism by which two drugs, danusertib and bosutinib, work together to overcome resistance in the gatekeeper mutation-specific disease. The team includes a researcher at and colleagues at the of the Austrian Academy of Sciences in Austria and the . The goal is to address an unmet medical need because this mutation confers resistance to all currently approved kinase inhibitors for .

The study appeared in the Sept. 30 online version of Nature Chemical Biology.

“Treatment of chronic myeloid leukemia rapidly improved after the introduction of the first BCR-ABL inhibitor, Gleevec (imatinib),” said study co-author Uwe Rix, Ph.D., an assistant member of the Moffitt’s Drug Discovery Department and Experimental Therapeutics Program. “However, it soon became apparent that a broad spectrum of possible resistance mechanisms necessitated second- and third-generation BCR-ABL inhibitors. Although these are mostly very successful, none of the currently approved options has been effective in patients with chronic myeloid leukemia who harbor the BCR-ABL gatekeeper mutation.”

The researchers investigated the molecular mechanisms and logic underlying the synergistic interaction between danusertib and bosutinib, which is specific for BCR-ABL gatekeeper mutation-transformed cells. They applied a novel systems pharmacology approach involving a combination of different proteomics and gene expression profiling methods.

“We found previously unappreciated features of both agents,” Rix said. “The synergy did not correlate with direct inhibition of BCR-ABL. Instead, our observations converged on the downstream MAPK signaling cascade as the predominantly affected pathway in the synergistic inhibition of BCR-ABL.”

The researchers said the combination of both compounds impaired the activity of c-MYC, a gene regulator that codes a transcription factor playing a well-established but a not well understood role in a broad spectrum of human cancers.

“In the context of chronic myeloid leukemia, c-MYC is required for BCR-ABL-mediated transformation,” Rix explained. “What is intriguing is that chronic myeloid leukemia cells with the BCR-ABL gatekeeper mutation seem to be more dependent on the MAPK/c-MYC signaling axis than BCR-ABL wild-type cells. Thus, challenging c-MYC with drugs appears promising in these resistant cells, but steps have only recently been made.”

The researchers concluded that they have unraveled the action and impact of a “new synergistic drug interaction between danusertib and bosutinib in a clinically relevant, highly drug-resistant disease setting” by revealing a “non-obvious synergistic mechanism elicited by several off targets of the two small molecules.”

“We believe this strategy of gaining a functional understanding of drug synergy may serve as a model for further mode-of-action studies,” they concluded.

Source

H. Lee Moffitt Cancer Center & Research Institute