Discovery of potent, orally active KIF18A inhibitors targeting CIN-high cancer cells.

Abstract

e15046 Background: KIF18A is a kinesin assisting chromosome congression and alignment during mitosis. It is nonessential in normal, euploid cell division but essential for a subset of aneuploid cancer cells with high chromosomal instability (CIN-high). KIF18A knockdown in these cells leads to mitotic arrest, cytostasis and cell death. As a result, KIF18A is an attractive anticancer target. Methods: Volastra drug discovery efforts identified and validated KIF18A as a promising target using genetic knockdown and pharmacological inhibition with a tool compound. High-throughput screening identified an ATP-noncompetitive hit that was optimized for potency, selectivity, and pharmacokinetic properties. Breadth of efficacy studies against a panel of cancer cell lines were used to formulate responder hypotheses and aid in patient selection. Mechanistic profiling and cell fate determination upon KIF18A inhibition was used to identify target engagement and clinical response biomarkers. Results: Our lead candidates bind to KIF18A with sub-nM potency and exhibit long (̃2 days) drug-target residence time. They are ATP and microtubule uncompetitive. They are highly selective for KIF18A and have no known off-target effects on related kinesins and in an in vitro safety screen. They are orally bioavailable in preclinical species, well tolerated and demonstrate tumor regression in mouse xenograft models. In contrast to many agents that disrupt the mitotic machinery, KIF18A inhibition does not impact growth of proliferating normal cells. Breadth of efficacy studies performed on a large panel of human cancer cell lines reveal sensitivity to KIF18A inhibitors across multiple tumor types including high-grade serous ovarian, as well as subtypes of breast and lung cancer. Conclusions: Volastra’s research efforts have culminated in the discovery of orally active, highly potent, selective, and efficacious KIF18A inhibitors as development candidates.