BTM-3566 activation of the mitochondrial protease OMA1 increases sensitivity to venetoclax and azacitidine in acute myelogenous leukemia.

Background: BTM-3566 is a member of the chemical class, 1-thiazol-2-yl-N-3-methyl-1H-pyrozole-5-carboxylic acids, which are potent, single agent anti-tumor agents in both B-cell lymphomas and select solid tumor malignancies. Therapeutic response is associated with activation of the mitochondrial metalloprotease OMA1. Drug induced activation of OMA1 leads to changes in mitochondria including alterations in cristae structure, morphology, and reduced expression of BH3 proteins such as MCL1. The therapeutic outcome is Bax-dependent apoptosis in B-cell lymphomas and regression or growth inhibition in solid tumors. We hypothesized that reductions in BH3 protein content and changes in mitochondrial cristae structure and function prime tumor cells for apoptosis. This may allow the use of BTM-3566 more broadly in conjunction with standard chemotherapy or targeted agents such as BH3 mimetics. Because venetoclax (a BH3 mimetic) and azacitidine are established standard-of-care (SOC) therapies for AML patients ineligible for intensive chemotherapy, we tested whether BTM-3566 enhances their activity. To test this hypothesis, BTM-3566 was evaluated in acute myelogenous leukemia (AML) cell lines to determine if synergy occurred in combination with venetoclax, azacytidine, or the ternary combination. Methods: The activity of BTM-3566, venetoclax, and/or azacitidine was determined in AML cell lines (HL-60, Kasumi-1 and KG-1) using Cell-Titre Glo (CTG) which serves as a surrogate for cell numbers. Apoptosis was measured using Caspase 3/7 Glo. Drug activity interactions were quantified using Synergyfinder + software. Results: BTM-3566 was active in all three AML cell lines (IC 50 range 300-600 nM). BTM-3566 acted synergistically with venetoclax to inhibit cell growth in all cell lines, while synergy with azacitidine was observed only in HL-60 cells. The ternary combination of BTM-3566, venetoclax, and azacitidine resulted in increased cell killing with an apparent increase in the potency of venetoclax. Caspase 3/7 assays confirmed that BTM-3566 and venetoclax each induced a time-dependent increase in apoptosis in HL-60 and Kasumi-1, but not KG-1 cells. Binary drug treatment of venetoclax and BTM-3566 led to increased Caspase 3/7 activation and a BTM-3566 dose dependent increase in the activity of venetoclax in HL-60 and Kasumi-1 cells. Conclusions: BTM-3566 targets a pathway important for mitochondrial integrity and control of apoptosis leading to reduced tumor cell growth and survival. Rational combinations of BTM-3566 with AML SOC agents demonstrate synergistic activity. Together, the findings support further evaluation of BTM-3566 to potentially broaden the utility of BH3-directed therapies in AML and potentially other difficult to treat malignancies. BTM-3566 is currently being evaluated in Phase I trials for DLBCL and select solid tumors.