Patients with medullary thyroid carcinoma (MTC) who have a mutation in the RET proto-oncogene remained stable or improved on all domains of health-related quality of life during treatment with selpercatinib, according to interim results from the ongoing phase 1/2 LIBRETTO-001 clinical trial published in The Oncologist.

MTC can either develop sporadically or be inherited. All patients with hereditary MTC have a mutation in the RET proto-oncogene, which encodes for a receptor tyrosine kinase. The standard of care for recurrent or metastatic MTC that is unresectable includes kinase inhibitors that are active against different kinases like RET. Selpercatinib is a highly selective RET inhibitor.

The LIBRETTO-001 trial is an open-label, first-in-human study that aims to evaluate the safety, tolerability, pharmacokinetics, and preliminary antitumor activity of oral selpercatinib in patients with advanced solid tumors, including MTC.

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The primary outcome measures include the incidence rate and category of dose-limiting toxicities during the first 28-day cycle of selpercatinib treatment. Secondary outcome measures include the number of participants with treatment-related adverse events and an abnormal laboratory or physical exam result, overall response rate and the duration of response, change in tumor size from baseline, overall survival, and percentage of participants with any serious adverse events.

The trial aims to recruit 989 participants aged 12 or more years and is still open for recruitment at 83 locations across the world. Its estimated completion date is November 21, 2023.

According to the interim results in 226 participants, 43.5% of patients had clinically meaningful improvement in diarrhea, a comorbidity that patients frequently experience that significantly impairs their daily living. More precisely, 80.4% of patients reported having diarrhea at baseline but this percentage ranged between 33.3% and 48.3% after cycle 2 of treatment.

“Future analyses will be conducted as the data mature,” the researchers wrote.


Wirth LJ, Robinson B, Boni V, et al. Patient-reported outcomes with selpercatinib treatment among patients with RET-mutant medullary thyroid cancer in the phase 1/2 LIBRETTO-001 trial. Oncologist. Published online September 13, 2021. doi:10.1002/onco.13977