RET and medullary thyroid gland carcinoma: In the registration studies (phase I–II trial, LIBRETTO-001 trial), at the dose of 160 mg twice daily, selpercatinib showed efficacy in MTC with a 1-year PFS of 82% in patients with RET mutant MTC who had previously been treated with vandetanib, cabozantinib, or both and of 92% in patients with RET-mutant MTC without previous treatment [12].