FDA Approves Selpercatinib for RET Fusion–Positive Thyroid Cancer
Posted: Monday, May 11, 2020
On May 8, the U.S. Food and Drug Administration (FDA) approved the use of the RET kinase inhibitor selpercatinib (Retevmo) to treat patients 12 years or older with metastatic advanced medullary thyroid cancer who require systemic therapy. This approval applies to patients who have thyroid tumors that have a mutation or fusion in the RET gene and who have stopped responding to radioactive iodine therapy or may not be eligible for radioactive iodine therapy.
The FDA approval is based on the results of the LIBRETTO-001 phase I/II trial. During the clinical trial, patients received a 160-mg oral dose of selpercatinib twice daily until disease progression or unacceptable toxicity. The study enrolled 143 adult and pediatric (aged 12 or older) patients with advanced or metastatic RET-mutant medullary thyroid cancer who had or had not been previously treated with cabozantinib, vandentanib, or both agents. In 55 patients previously treated with cabozantinib and/or vandentanib, the overall response rate was 69%, with 76% of patients showing a treatment response that lasted for at least 6 months. Of the 88 patients naive to therapy, the overall response rate was 73%, with 61% of patients showing a treatment response that lasted for at least 6 months.
The study also enrolled 19 patients with RET fusion–positive thyroid cancer who were refractory to radioactive iodine and had received another prior systemic treatment. Eight patients with RET fusion–positive thyroid cancer who were refractory to radioactive iodine and had not received any additional therapy also participated. Following the same procedure, there was an overall response rate of 79% in 19 patients who received prior treatment; for 87% of responders, the duration of response was at least 6 months. All patients had a 100% overall response rate; for 75% of responders, the response lasted at least 6 months.