Merck (NYSE: MRK), known as MSD outside of the United States and Canada, announced the discontinuation of the clinical development programs for vibostolimab, an anti-TIGIT antibody, and favezelimab, an anti-LAG-3 antibody. Vibostolimab is being evaluated as an investigational fixed-dose combination with pembrolizumab (KEYTRUDA^® ) in the KeyVibe program. Favezelimab is being evaluated as an investigational fixed-dose combination with pembrolizumab in the KEYFORM program.

Merck is discontinuing the Phase 3 KeyVibe-003 and KeyVibe-007 trials, which are evaluating the fixed-dose combination of vibostolimab and pembrolizumab in certain patients with non-small cell lung cancer (NSCLC), based on the recommendation of an independent Data Monitoring Committee (DMC). In a pre-planned analysis, both trials met the pre-specified futility criteria for the primary endpoint of overall survival. In these studies, the safety profile of vibostolimab/pembrolizumab was consistent with that observed for vibostolimab and pembrolizumab in previously reported studies, with no new safety signals identified. As expected with dual checkpoint inhibitor therapy, more immune-related adverse events were observed with the fixed-dose combination than with pembrolizumab. Considering the totality of data from the Phase 3 KeyVibe studies, including the efficacy outcomes from KeyVibe-003 and KeyVibe-007, the company has decided to discontinue the Phase 3 KeyVibe-006 trial and other vibostolimab studies.

Separately, Merck has decided to end the favezelimab clinical development program, and will stop enrollment in the Phase 3 KEYFORM-008 trial evaluating the fixed-dose combination of favezelimab and pembrolizumab in patients with relapsed or refractory classical Hodgkin lymphoma (cHL) whose disease has progressed following prior anti-PD-1 therapy. Patients currently in this trial may continue on therapy until study completion. KEYFORM-008 is the only Phase 3 study in the KEYFORM clinical development program for which results are not available. The company has made this decision after a thorough evaluation of data from the favezelimab clinical program and will prioritize the development of other candidates in its comprehensive and diversified oncology pipeline. This decision is not based on any concerns about the safety of this fixed-dose combination.

Merck is informing study investigators for these clinical trials and advises patients to speak to their study team and physician regarding next steps and treatment options. Data analyses for the Phase 3 trials are ongoing, and the results will be shared with the scientific community.

"Following a careful analysis of the data, the decision has been made to discontinue development of these candidates to prioritize other ongoing programs. We are grateful to all the patients, caregivers and investigators for their many contributions that made these studies possible," said Dr. Marjorie Green, senior vice president and head of oncology, global clinical development, Merck Research Laboratories. "We continue to pursue the most promising science with a focus on agents with the greatest potential to improve outcomes for more patients with cancer."