BAY1217389

BAY 1217389 is a potent, and selective inhibitor of the monopolar spindle 1 (MPS1) kinase with an IC₅₀ value less than 10 nM. IC50 & Target: IC50: <10 nM (MPS1)^[1] In Vitro: BAY 1217389 inhibits Mps1 kinase activity with IC₅₀ value below 10 nM while showing an excellent selectivity profile. In cellular mechanistic assays BAY 1217389 abrogates nocodazole-induced SAC activity and induces premature exit from mitosis resulting in multinuclearity and tumor cell death. BAY 1217389 efficiently inhibits tumor cell proliferation in vitro^[1]. In Vivo: BAY 1217389 achieves moderate efficacy in monotherapy in tumor xenograft studies. However, in line with its unique mode of action, when combines with paclitaxel, low doses of Mps1 inhibitor reduces paclitaxel-induced mitotic arrest in line with weakening of SAC activity. As a result, combination therapy strongly improves efficacy over paclitaxel or Mps1 inhibitor monotreatment at the respective MTDs in a broad range of xenograft models including those showing acquired or intrinsic paclitaxel-resistance. BAY 1217389 shows good tolerability without adding toxicity to paclitaxel monotherapy^[1].