LIBRETTO-531: This phase III trial is trying determine whether the targeted therapy (Selpercatinib) is safe and more effective than current standard targeted therapies (Cabozantinib or Vandetanib) in patients with advanced thyroid cancerA Multicenter, Randomized, Open-label, Phase 3 Trial Comparing Selpercatinib to Physicians Choice of Cabozantinib or Vandetanib in Patients With Progressive, Advanced, Kinase Inhibitor Naïve, RET-Mutant Medullary Thyroid Cancer

Inclusion

• At least 18 years of age (participants as young as 12 years of age will be allowed if permitted by local regulatory authorities).
• Histologically or cytologically confirmed, unresectable, locally advanced and/or metastatic MTC and no prior history of treatment with kinase inhibitors for advanced/metastatic disease.
• Radiographic progressive disease per Response Evaluation Criteria in Solid Tumors (RECIST) 1.1 at screening compared with a previous image taken within the prior 14 months as assessed by the BICR. Participants with measurable or non-measurable but evaluable disease are eligible; however, participants with non-measurable disease may not have disease limited to bone sites only.

• A defined/acceptable RET gene alteration identified in a tumor, germline deoxyribonucleic acid (DNA) or blood sample.

  • Tumor tissue in sufficient quantity to allow for retrospective central analysis of RET mutation status
• Eastern Cooperative Oncology Group performance status score of 0 to 2.
• Adequate hematologic, hepatic, and renal function and electrolytes.
• Men and women of childbearing potential must agree to use a highly effective contraceptive method during treatment with study drug and for 4 months following the last dose of study drug.
• Ability to swallow capsules.