RET and thyroid gland carcinoma: However, in May 2020 the FDA approved selpercatinib, a selective small-molecule RET inhibitor for adult NSCLC patients with metastatic RET fusions, as well as patients ≥12 years old with RET-mutated MTC or fusion-positive thyroid cancer who require systemic therapy (and are refractory to radioactive iodine, if indicated).