Proleukin, also known by its generic name aldesleukin, is a form of immunotherapy medication used primarily in the treatment of kidney cancer (renal cell carcinoma) and metastatic melanoma. It is a synthetic version of interleukin-2 (IL-2), a protein that naturally occurs in the body and plays a crucial role in activating the immune system. By mimicking the action of IL-2, Proleukin enhances the body's ability to detect and destroy cancer cells. It is administered through intravenous infusion, and its use can be associated with significant side effects, which necessitates careful patient selection and monitoring. Despite its challenges, Proleukin has been a valuable option for patients with certain types of advanced cancers, offering a potential for durable responses in some cases.