Merck halts lung cancer trial due to safety concerns

USA—Merck & Co has announced that it is discontinuing a pivotal Phase 3 trial evaluating a treatment for extensive-stage small cell lung cancer (ES-SCLC), following a concerning rate of adverse events among participants.

The decision to halt the KeyVibe-008 trial, which had enrolled 460 patients, was based on an independent Data Monitoring Committee (DMC) recommendation.

The trial aimed to assess the efficacy of a fixed-dose combination of vibostolimab—an investigational anti-TIGIT antibody—and pembrolizumab (KEYTRUDA), Merck’s well-known anti-PD-1 therapy.

Keytruda is already a major player in the cancer treatment arena, often used in combination with chemotherapy for the first-line treatment of ES-SCLC.

In this trial, it was compared to atezolizumab, another checkpoint inhibitor, used alongside chemotherapy.

At a pre-planned interim analysis, the data revealed that the combination of vibostolimab and pembrolizumab did not meet the primary endpoint of overall survival (OS) as hoped.

Specifically, the data met the pre-specified futility criteria, indicating that the treatment was unlikely to provide a benefit over the current standard of care.

Furthermore, the analysis showed that patients receiving the vibostolimab and pembrolizumab combination experienced a higher rate of adverse events (AEs) and immune-related adverse events compared to those in the control group.

In response to these findings, Merck has informed study investigators of the trial’s termination and advised patients to discontinue treatment with the fixed-dose combination.

Instead, the company has recommended that patients be offered alternative treatment options, specifically atezolizumab, which remains a viable option for managing ES-SCLC.

Dr Marjorie Green, Senior Vice President and Head of Oncology Global Clinical Development at Merck Research Laboratories, commented on the challenging nature of treating small-cell lung cancer.

She highlighted the disease’s dismal prognosis, noting a five-year survival rate of just seven percent and a lack of significant advancements in treatment options.

This development is a significant setback for both investors and experts who had high expectations for new immunotherapies, particularly those targeting the TIGIT receptor, which is present in immune cells.

The discontinuation follows a similar announcement in May 2024 when Merck also ended a late-stage trial for the same combination therapy in melanoma patients due to insufficient efficacy data. 

According to MarketWatch, in premarket trading, Merck’s stock was down by 0.3%. Despite this decline, the stock has risen by 3% year-to-date, contrasting with the S&P 500’s 9% gain over the same period.