Patients with medullary thyroid carcinoma (MTC) treated with selpercatinib continue to show very durable responses in the phase1/2 LIBRETTO-001 clinical trial, according to an update published in the Annals of Oncology. This is the case whether or not they have received previous treatment with cabozantinib and vandetanib.

These findings, which are based on additional patients and a longer follow-up period, suggest that the first-line use of selpercatinib can be highly effective in MTC.

The investigators also reported an unchanged safety profile in spite of longer treatment durations. 

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The findings were presented at the European Society for Medical Oncology Congress.

Read more about experimental therapies for MTC

LIBRETTO-001 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 with a RET gene alteration, including MTC.

Following an updated analysis of the data after an additional follow-up period of 15 months in patients with RET-mutant MTC, investigators reported an overall survival rate of 81% in treatment-naïve patients and an overall survival rate of 73.5% in those who were pretreated with cabozantinib and vandetanib.

They said that despite a median follow-up time of around 2 years, the duration of response and progression-free survival data “are still immature” and response is ongoing in most patients. 

At 2 years, 81.1% of treatment-naïve patients remained progression-free, the researchers reported. This ratio was 64.4% for patients pretreated with cabozantinib and vandetanib. 

In the safety population of 319 patients who received at least 1 dose of selpercatinib, the most common severe treatment-emergent adverse events were hypertension, increased AST/ALT levels, hyponatremia, lymphopenia, and diarrhea. A total of 23 patients discontinued treatment due to treatment-emergent adverse events. This included 13 patients who quit due to treatment-related adverse events.

The trial is ongoing and is expected to be completed on September 1, 2024.


Kroiss M, Sherman EJ, Wirth LJ, et al. 1656P Durable efficacy of selpercatinib in patients with medullary thyroid cancer (MTC): update of the LIBRETTO-001 trial. Ann Oncol. 2022;33, Supp.7;S1299-S1300. doi:10.1016/j.annonc.2022.07.1736

A study of selpercatinib (LOXO-292) in participants with advanced solid tumors, RET fusion-positive solid tumors, and medullary thyroid cancer (LIBRETTO-001). US National Library of Medicine. August 8, 2022. Accessed September 28, 2022