Defactinib is a focal adhesion kinase (FAK) inhibitor used primarily in cancer research and therapy. It targets tumor microenvironment signaling, helping to disrupt cancer cell survival, migration, and resistance to treatment. It has been investigated in clinical trials for solid tumors, including ovarian, pancreatic, and non-small cell lung cancer, often in combination with other anticancer agents such as immunotherapies or chemotherapy. By inhibiting FAK, defactinib may enhance immune cell infiltration into tumors and improve response to immune checkpoint inhibitors. It is also being explored for its potential to reduce cancer-associated fibroblast activity, which can support tumor growth and limit drug delivery.