BLU-667, also known as Pralsetinib, is primarily used in the treatment of certain types of cancer. It is specifically effective in targeting cancers caused by RET gene alterations, which include non-small cell lung cancer (NSCLC), medullary thyroid cancer (MTC), and other thyroid cancers. The drug works by inhibiting the activity of the RET protein, which is crucial for the growth and survival of cancer cells with these mutations. This targeted approach helps to slow down or stop the progression of the disease, offering a more precise treatment option compared to traditional chemotherapy. Pralsetinib is particularly beneficial for patients who have developed resistance to other treatments or who have specific genetic mutations that make them suitable candidates for this therapy. Its use is typically guided by genetic testing to ensure it is prescribed to those who are most likely to benefit.