TTK (Mps1), PLK1

Class

Small molecule dual mitotic kinase inhibitor

Pathway

Mitotic spindle assembly checkpoint

TTK (also called Mps1) and PLK1 are enzymes called kinases that orchestrate mitosis, the process by which a cell duplicates its chromosomes and divides them equally into two daughter cells. Both are core components of the spindle assembly checkpoint, a surveillance system that delays cell division until every chromosome is correctly attached to the microtubule spindle that will pull it apart. TTK generates the checkpoint signal at unattached chromosome-attachment sites; PLK1 has broader duties, including organizing the spindle poles and triggering the biochemical events that allow division to proceed once attachments are satisfied. Cancer cells frequently carry chromosomal abnormalities and rely heavily on this checkpoint machinery to avoid dying from further division errors. A molecule that inhibits both TTK and PLK1 at once removes the checkpoint's restraining signal while also disrupting the physical machinery of spindle formation, pushing genomically unstable cells into a botched division that is frequently lethal to the cell. This dual mechanism is intended to be more disruptive to error-prone tumor cells than to normal cells with intact, accurate division machinery, though both kinases are also active in healthy dividing tissue. The approach broadly matters in cancers characterized by high chromosomal instability, where forcing mitotic errors can selectively eliminate malignant cells.