Lenvatinib mesylate is primarily used in the treatment of certain types of cancer. It is an oral multi-kinase inhibitor that targets vascular endothelial growth factor receptors (VEGFR), fibroblast growth factor receptors (FGFR), and other kinases involved in tumor growth and angiogenesis.

One of its key applications is in the treatment of differentiated thyroid cancer (DTC) that is refractory to radioactive iodine. It helps to slow down the progression of the disease by inhibiting the blood supply to tumors, thereby restricting their growth.

Additionally, lenvatinib mesylate is used in combination with other drugs, such as pembrolizumab, for the treatment of advanced renal cell carcinoma (RCC). This combination therapy has shown efficacy in improving progression-free survival in patients with this type of kidney cancer.

It is also approved for the treatment of unresectable hepatocellular carcinoma (HCC), where it offers an alternative to other systemic therapies. By targeting multiple pathways involved in tumor proliferation and angiogenesis, it provides a therapeutic option for patients who may not respond to other treatments.

Overall, lenvatinib mesylate plays a crucial role in managing advanced or refractory cancers, offering hope for improved outcomes in patients with limited treatment options.