Eli Lilly and Company (Lilly) has announced that Retevmo (selpercatinib) met the primary endpoint of the Phase 3 LIBRETTO-531 study in advanced or metastatic rearranged during transfection (RET)-mutant medullary thyroid cancer (MTC).

Retevmo (formerly known as LOXO-292) is a highly selective and potent RET kinase inhibitor with CNS activity.

The trial compared Retevmo against physician’s choice of the multikinase inhibitors (MKIs) vandetanib or cabozantinib as an initial treatment. It recruited 291 patients who were randomised 2:1 to get either Retevmo or cabozantinib or vandetanib.

According to a pre-specified interim efficacy analysis undertaken by an independent data monitoring committee (IDMC), the investigational candidate showed a clinically meaningful and statistically significant improvement in progression-free survival (PFS). This was the primary endpoint of the late-stage study.

The key secondary endpoints consisted of overall survival (OS), duration of response (DoR), overall response rate (ORR), and treatment failure-free survival (TFFS).

The rate of adverse events on Retevmo were generally similar with its previously reported development programme including LIBRETTO-001, LIBRETTO-121, and LIBRETTO-321.

Loxo@Lilly chief medical officer David Hyman said: “These data from the LIBRETTO-531 trial confirm the importance of selectivity in targeting RET-driven cancers and suggest Retevmo should be considered the preferred first-line treatment for people with advanced RET-mutant medullary thyroid cancer.

“Taken together with the recent positive Retevmo Phase 3 LIBRETTO-431 announcement in lung cancer, these results underscore the importance of timely and broad-based genomic testing to ensure patients who could potentially benefit receive targeted therapies. We look forward to sharing detailed data with the oncology community.”

The findings of the LIBRETTO-531 trial build on the results of the LIBRETTO-001 clinical trial of patients with RET-driven malignancies treated with RET inhibitors, said Lilly.

Earlier this month, Retevmo met the primary endpoint of the Phase 3 LIBRETTO-431 study in adults with newly diagnosed advanced or metastatic RET fusion-positive non-small cell lung cancer (NSCLC).

The drug has approval in the US for the treatment of locally advanced or metastatic solid tumours with a RET gene fusion following prior systemic treatment.