Fruquintinib is primarily used in the treatment of metastatic colorectal cancer. It works as a selective inhibitor of vascular endothelial growth factor receptors (VEGFR), which play a crucial role in tumor angiogenesis. By blocking these receptors, it helps to cut off the blood supply to the tumor, thereby inhibiting its growth and spread. This makes it a valuable option for patients who have not responded well to other forms of chemotherapy or targeted therapy. It is often administered orally, providing a convenient treatment option for patients. Clinical trials have shown that it can improve progression-free survival, making it a significant addition to the arsenal of cancer treatments.