Structure based design of POL-theta inhibitors - acute myeloid leukemia (AML) is the most frequently diagnosed form of acute leukemia in adults, and standard of care treatment involving chemotherapy…

Structure based design of POL-theta inhibitors - acute myeloid leukemia (AML) is the most frequently diagnosed form of acute leukemia in adults, and standard of care treatment involving chemotherapy and/or stem cell transplantation only cures 30-40% of patients. Recent studies show that amls with FLT3 receptor activating internal tandem duplication (ITD) mutations (FLT3(ITD)- positive amls) become defective in the BRCA1/2 pathway of homologous recombination (HR) following treatment with tyrosine kinase inhibitors (TKI). Brca-deficiency confers strong sensitivity to DNA damage and/or DNA repair inhibition, and thus presents a promising new therapeutic strategy for AML. We discovered that brca-deficient leukemia cells are hyper-dependent on the DNA repair enzyme DNA polymerase theta (POL), which is dispensable for normal cells and mice. POL is involved in translesion synthesis and the microhomology-mediated end-joining (mmej) double-strand break (DSB) repair pathway. Our leading small- molecule POL inhibitor (poli) kills AML patient cells CO-treated with the TKI quizartinib which causes brca-deficiency, whereas quizartinib and poli as single agents shows significantly less killing. These data demonstrate the poli + TKI combination as a promising therapeutic strategy for FLT3(ITD)-positive AML. Poli also shows preferential killing of other brca-deficient leukemias (all, CML) in vitro and in vivo, especially in combination with TKI. In summary, our data discover POL as a novel drug target in leukemia, and demonstrate poli + TKI as a promising therapeutic strategy, especially in aggressive FLT3(ITD)-positive AML. In phase i, recombination therapeutics, LLC (RTX), a start-up precision oncology company, plans to increase the potency of our leading poli as a novel treatment for FLT3(IDT)-positive AML using x-RAY crystallography and structure based optimization/design by developing the following aims: 1. To solve the CO-crystal structure of POL-DNA- poli ternary complexes; 2. To optimize poli using structure based optimization/design. In phase II, RTX aims to achieve the following goals: 1. Further develop our leading poli drug candidate by achieving more favorable adme and pharmacokinetic parameters; 2. Characterize optimized poli in combination with TKI in FLT3(IDT)-positive AML animal models in vivo.