Selpercatinib is primarily used in the treatment of certain types of cancers that are driven by specific genetic alterations. It is particularly effective in treating non-small cell lung cancer (NSCLC), medullary thyroid cancer (MTC), and other thyroid cancers that have RET gene mutations or fusions. The drug works by selectively inhibiting the RET kinase, which is crucial for the growth and survival of cancer cells with these genetic changes. In clinical settings, selpercatinib has shown significant efficacy in shrinking tumors and improving progression-free survival in patients with RET-altered cancers. It is often prescribed when other treatments have failed or are not suitable, offering a targeted therapy option with a favorable safety profile. Additionally, its ability to penetrate the central nervous system makes it useful in treating cancers that have metastasized to the brain. Overall, selpercatinib represents a significant advancement in precision medicine, providing hope for patients with RET-driven cancers by offering a more tailored and effective treatment approach.