A Study of Selpercatinib (LY3527723) in Participants With RET-Mutant Medullary Thyroid Cancer

For people ages 12 years and up

• At least 18 years of age (participants as young as 12 years of age will be allowed if permitted by local regulatory authorities).
• Histologically confirmed, unresectable, locally advanced and/or metastatic MTC and no prior history of treatment with kinase inhibitors for advanced/metastatic disease.
• Radiographic progressive, measurable 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 central review.
• 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 6 months following the last dose of study drug.
• Ability to swallow capsules.

Exclusion Criteria:

• An additional validated oncogenic driver in MTC if known that could cause resistance to selpercatinib treatment. Examples include, but are not limited to RAS gene mutations and ALK gene fusions.
• Symptomatic central nervous system (CNS) metastases, leptomeningeal carcinomatosis, or untreated spinal cord compression.
• Clinically significant active cardiovascular disease or history of myocardial infarction within 6 months, history of Torsades de pointes, or prolongation of the QTcF >470 milliseconds on more than one electrocardiogram (ECG) during screening. Participants who are intended to receive vandetanib if randomized to the control arm ineligible if QTcF is >450 milliseconds.
• Active uncontrolled systemic bacterial, viral, or fungal infection or serious ongoing uncontrolled intercurrent illness.
• Active hemorrhage or at significant risk for hemorrhage.
• Other malignancy unless nonmelanoma skin cancer, carcinoma in situ of the cervix or malignancy diagnosed ≥2 years previously and not currently active. Participants with multiple endocrine neoplasia type 2 (MEN2) associated pheochromocytoma may be eligible.