Selpercatinib is a highly selective RET kinase inhibitor used primarily in the treatment of cancers driven by RET gene alterations. It is effective in patients with non-small cell lung cancer (NSCLC) and thyroid cancers that have specific RET fusions or mutations. The drug shows strong activity against tumors regardless of prior treatment history, including those resistant to other therapies. It is particularly beneficial in metastatic or advanced cases where surgery is not feasible. Selpercatinib can cross the blood-brain barrier, making it effective against central nervous system metastases, which is a significant advantage over many other targeted therapies. In clinical use, it has demonstrated high response rates and durable responses, often with a manageable side effect profile. It is used in both adult and pediatric patients, especially those with RET-mutant medullary thyroid cancer or RET fusion-positive thyroid cancer. Its targeted mechanism allows for precision treatment, reducing damage to healthy cells and improving patient outcomes compared to conventional chemotherapy.