Patients with metastatic RET fusion–positive non–small cell lung cancer experienced encouraging responses with selpercatinib.
Patients with metastatic RET fusion–positive non–small cell lung cancer (NSCLC) experienced favorable response rates following treatment with selpercatinib (Retevmo), according to data from the phase 1/2 LIBRETTO-001 trial (NCT03157128) presented during the 2022 European Lung Cancer Congress.1
Following treatment, the 247 patients who had previously received platinum chemotherapy experienced a confirmed objective response rate (ORR) of 61.1% (95% CI, 54.7%-67.2%). Among the 69 treatment-naïve patients, the confirmed ORR was 84.1% (95% CI, 73.3%-91.8%). In addition, the 26 patients with measurable central nervous system (CNS) at baseline achieved an ORR of 84.6%. Among this group, 22 patients experienced complete or partial response as their confirmed best response to treatment.
At a 20.3-month median follow-up, patients in the treatment-naïve population were found to have an estimated duration of response (DOR) of 20.2 months (55.2% censoring rate). In the pretreated population, at a median follow-up time of 21.2 months, the median DOR was 28.6 months (60.9%).
Furthermore, the agent is anticipated to elicit a median progression-free survival (PFS) in the treatment-naïve and pretreated populations of 22.0 months (53.6% censoring rate; median follow-up of 21.9 months) and 24.9 months (55.9% censoring rate; median follow-up of 24.7 months), respectively. Patients with measurable CNS disease experienced a median intracranial PFS of 19.4 months; however, these median estimated are not yet mature.
With a median follow-up of 20.3 months in the treatment-naïve population, the median duration of response (DOR) was estimated to be 20.2 months (55.2% censoring rate). At a median follow-up of 21.2 months in the platinum-pretreated population, the median DOR was estimated to be 28.6 months (60.9%).
The estimated median progression-free survival (PFS) in the treatment-naïve and pretreated populations were 22.0 months (53.6% censoring rate; median follow-up of 21.9 months) and 24.9 months (55.9% censoring rate; median follow-up of 24.7 months), respectively. In those with measurable CNS disease, the median intracranial PFS with selpercatinib was 19.4 months. However, the median estimates remain immature.
“The LIBRETTO trial provides the largest set of clinical data for a RET inhibitor and these results continue to demonstrate evidence of meaningful clinical outcomes for patients with metastatic RET fusion–positive NSCLC treated with [selpercatinib], including those with difficult-to-treat brain metastases,” David Hyman, MD, chief medical officer of oncology at Eli Lilly and Company, stated in a press release.
In May 2020, the FDA granted an accelerated approval to selpercatinib for the treatment of patients with RET alteration–positive NSCLC, medullary thyroid cancer, and other thyroid cancers based on earlier data from LIBRETTO-001.2 The regulatory decision is contingent upon data from a confirmatory trial.
The multicenter phase 1/2 LIBRETTO-001 trial enrolled patients with a diagnosis of advanced or metastatic solid tumors harboring RET alterations.3 Patients needed to have an ECOG performance status ranging from 0 to 2, a QTc of ≤470 msec, and acceptable organ function. Notably, those with asymptomatic CNS metastases were allowed to participate.
A total of 355 patients were eligible for the efficacy analysis; of these patients, 247 patients were previously treated with at least 1 line of platinum chemotherapy and 69 were treatment naïve. Those who received prior treatment had received a median of 2 prior regimens (range, 1-15); 58% of these patients had received anti–PD-1/PD-L1 agents.
The primary end point of the trial was ORR per RECIST v1.1 criteria by independent review, and secondary end points included DOR, PFS, and safety.
The safety findings observed in the cohort proved to be consistent with what is known about selpercatinib. A total of 356 patients who had received at least 1 dose of the agent comprised the safety population. The adverse effects that were experienced by 25% or more of patients included dry mouth, diarrhea, hypertension, increased alanine/aspartate aminotransferase levels, peripheral edema, constipation, rash, headache, and fatigue.
Thirty four percent of patients needed to discontinue treatment with selpercatinib, with 10% doing so because of toxicity. Eleven of these cases were determined to be associated with the study agent.
“We are continuing to build on the robust body of evidence supporting [selpercatinib], including through an ongoing randomized phase 3 confirmatory study, with a planned readout in 2023,” Hyman added.
The phase 3 LIBRETTO-431 (NCT04194944), which is comparing the safety and efficacy of selpercatinib with standard treatment in patients with RET fusion–positive nonsquamous NSCLC that has spread to other parts of the body, is currently recruiting.4