S81694 + paclitaxel

S81694 is an investigational small molecule inhibitor that targets the MPS1 kinase (Monopolar spindle 1 kinase), an enzyme involved in cell division. By blocking MPS1 kinase, S81694 disrupts proper chromosome segregation during mitosis, leading to cancer cell death. Paclitaxel is a well-established chemotherapy drug classified as a taxane; it works by stabilizing microtubules and preventing their disassembly, thereby inhibiting cell division and promoting apoptosis in cancer cells. The combination of S81694 with paclitaxel was investigated for the treatment of metastatic breast cancer (including triple-negative subtypes) in patients who had exhausted standard therapies. Clinical development was discontinued after early-phase studies due to limited therapeutic window and emerging alternative treatments[1][4][7].