CHK1 (Checkpoint kinase 1)

Class

Small molecule kinase inhibitor

Pathway

DNA damage response / cell cycle checkpoint signaling

Checkpoint kinase 1 (CHK1) is a serine/threonine kinase that acts as a central enforcer of the DNA damage response, the cellular surveillance system that detects damaged or incompletely replicated DNA and halts cell cycle progression until repair is complete. CHK1 is activated downstream of the ATR kinase whenever replication forks stall or DNA breaks occur, and it enforces arrest at the S-phase and G2/M checkpoints, giving cells time to repair damage before dividing. Cancer cells frequently rely heavily on this checkpoint because oncogene-driven proliferation causes chronic replication stress, and many tumors have lost the parallel G1 checkpoint through mutation of the tumor suppressor p53. Inhibiting CHK1 removes this remaining safeguard, forcing genomically damaged cells to enter mitosis prematurely, which leads to catastrophic chromosome missegregation and cell death. This rationale underlies interest in CHK1 inhibition as a strategy to sensitize tumors to DNA-damaging chemotherapy or radiation, and potentially as a standalone approach in cancers with intrinsically high replication stress. The mechanism broadly matters across oncology wherever tumor genomic instability or checkpoint dependency can be exploited therapeutically.