A new study has found gastrointestinal adverse effects to be more common with selpercatinib for medullary thyroid cancer (MTC) than previously thought. The study, published in the Journal of Clinical Endocrinology & Metabolism, noted that the effects were generally self-limiting but required dose adjustments.

“During [the LIBRETTO-001 clinical trial], as an international site, we observed an increasing number of patients reporting abdominal and gastrointestinal adverse effects,” the authors explained.

“Here, in a retrospective audit of patients currently on selpercatinib, we describe small bowel edema as a new feature of gastrointestinal adverse effects associated with this drug, and detail histopathology and a radiological scoring system to further characterize this finding.”

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Selpercatinib is a US Food and Drug Administration (FDA)-approved selective RET inhibitor employed in the treatment of RET-mutated MTC. Early trials of the drug have resulted in significant tumor reductions with few adverse effects; therefore, its use has increased, as has the need to characterize the adverse effects patients experience, with the aim of optimizing the clinical use of this agent.

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The research team included all 22 patients enrolled in the LIBRETTO-001 trial in Sydney, Australia in the study. The patients had 3 monthly computed tomography scans and reviews to determine the adverse effects associated with selpercatinib.

Ten of the patients developed gastrointestinal symptoms a median of 41 days after the first dose. These included changes in bowel habits, abdominal swelling and discomfort, anorexia, and nausea. Eight patients needed dose adjustments due to the symptoms, and such modifications typically resolved them.

The authors recommend future studies with larger patient samples to determine the risk factors for gastrointestinal adverse effects in patients being treated with selpercatinib.


Tsang V, Gill A, Gild M, et al. Selpercatinib treatment of RET mutated thyroid cancers is associated with gastrointestinal adverse effects. J Clin Endocrinol Metab. Published online June 1, 2022. doi.10.1210/clinem/dgac337