The caspase-8 inhibitor emricasan combines with the SMAC mimetic birinapant to induce necroptosis and treat acute myeloid leukemia

Gabriela Brumatti, Chunyan Ma, Najoua Lalaoui, Nhu Y. Nguyen, Mario Navarro, Maria C Tanzer, Jennifer Richmond, Margherita Ghisi, Jessica M. Salmon, Natasha Silke, Giovanna Pomilio, Stefan P Glaser, Elisha de Valle, Raffi Gugasyan, Mark A. Gurthridge, Stephen M Condon, Ricky W Johnstone, Richard Lock, Guy S Salvesen, Andrew WeiDavid L. Vaux, Paul G Ekert, John Silke

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Resistance to chemotherapy is a major problem in cancer treatment, and it is frequently associated with failure of tumor cells to undergo apoptosis. Birinapant, a clinical SMAC mimetic, had been designed to mimic the interaction between inhibitor of apoptosis proteins (IAPs) and SMAC/Diablo, thereby relieving IAP-mediated caspase inhibition and promoting apoptosis of cancer cells. We show that acute myeloid leukemia (AML) cells are sensitive to birinapant-induced death and that the clinical caspase inhibitor emricasan/IDN-6556 augments, rather than prevents, killing by birinapant. Deletion of caspase-8 sensitized AML to birinapant, whereas combined loss of caspase-8 and the necroptosis effector MLKL (mixed lineage kinase domain-like) prevented birinapant/IDN-6556-induced death, showing that inhibition of caspase-8 sensitizes AML cells to birinapant-induced necroptosis. However, loss of MLKL alone did not prevent a caspase-dependent birinapant/IDN-6556-induced death, implying that AML will be less likely to acquire resistance to this drug combination. A therapeutic breakthrough in AML has eluded researchers for decades. Demonstrated antileukemic efficacy and safety of the birinapant/emricasan combination in vivo suggest that induction of necroptosis warrants clinical investigation as a therapeutic opportunity in AML.

Original languageEnglish
Article number339ra69
JournalScience Translational Medicine
Issue number339
Publication statusPublished - 18 May 2016

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