Embargoed: Sunday, May 31st 7am CST / 8am EST
Six years after being brought to market as the first targeted therapy for patients with rare genetic tumor mutations, Eli Lilly’s Retevmo (selpercatinib) is solidifying its legacy New study shows ‘dramatic’ results, demonstrating the importance of RET fusion biomarker testing.
Retevmo has some broad indications in its name and has long targeted tumors with changes in the rearranged during transfection (RET) gene. However, the early-stage RET fusion-positive non-small cell lung cancer (NSCLC) patient population has yet to realize the major benefits of this push until the arrival of Lilly’s Phase 3 Libretto-432.
Presented during the plenary session of the 2026 American Society of Clinical Oncology (ASCO) Annual Meeting in Chicago, Libretto-432 showed that Retevmo could reduce the risk of disease recurrence or death by a whopping 83% compared to a placebo. The study, the first of its kind to compare selective RET kinase inhibitors as adjuvant therapy in a patient population, included 151 patients who received treatment or placebo for up to three years after radiation therapy or surgery, with or without chemotherapy, Dr. Lilly noted in a May 31 press release.
At 24 months in the primary analysis population of patients with stage 2-3A disease, event-free survival for Retevmo-treated patients was 92%, compared with 61% for those in the placebo group.
Across the broad study population of stage 1B-3A patients, event-free survival was 94% in the treatment arm and 70% in the placebo arm, Lilly reported.
Meanwhile, the company said that while overall survival results were “trending in favor of” Retevmo, they were immature at the time of analysis.
Although RET fusions are rare compared to other commonly known cancer mutations such as EGFR and ALK, the results help establish RET fusions as important biomarkers to test across all disease stages, the company said. RET fusions are found in 1% to 2% of NSCLC patients, the study authors noted.
“Unlike EGFR and ALK, until now these patients have not had a way to treat disease if it occurs in the early stages,” Jacob Van Naarden, president of Lilly’s oncology division and head of corporate business development, explained in a recent interview with Fierce, noting that Libretto-432 “qualifies RET and selpercatinib in the same context.”
Two years after Retevmo made its market debut as a treatment. more advanced Lung cancer and thyroid cancer with RET mutations, this drug has taken away a much broader label covering all Locally advanced or metastatic solid tumors driven by biomarkers. Since then, the therapy has become a mainstream standard of care for a specific group of patients whose genomic alterations make them “very sensitive” to the treatment, Van Naarden said.
For Lilly and Van Naarden, the “dramatic efficacy” seen throughout the Retevmo study reasserts the need for RET genomic testing in the initial treatment process. While this testing is not necessarily straightforward, the executive suggests that the range of tests performed for the EGFR and ALK biomarkers, for example, should become commonplace in RET.
“There’s an underlying lineage of biology here,” Van Naarden explained. “For lung cancer physicians and patients who are embracing EGFR- and ALK-directed therapy for early diagnosis, RET is also now “firmly in the mix,” he emphasized.
Lilly plans to use the study results as the basis for a label expansion proposal with global drug regulators “in the coming months,” Van Naarden confirmed.
“This is in many ways the final chapter in the development program for this drug,” the executive added, “but it’s certainly an exciting program.”
Given the rare nature of the biomarker, Retevmo is not a significant sales driver for Lilly’s oncology portfolio, which had sales of $364 million in 2024 and $456 million last year. The company has put virtually all of its RET chips into the drug after exiting the next-generation RET inhibitor aimed at overcoming acquired resistance to Retevmo in 2024. Retevmo and its defunct successor both joined Lilly, which acquired Loxo Oncology in 2019 for $8 billion.
