Merck Provides Update on KeyVibe and KEYFORM Clinical Development Programs Evaluating Investigational Vibostolimab and Favezelimab Fixed-Dose Combinations with Pembrolizumab

RAHWAY, N.J.--(BUSINESS WIRE)-- Merck (NYSE: MRK), known as MSD outside of the United States and Canada, today 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."

About KeyVibe-003 KeyVibe-003 is a randomized, double-blind Phase 3 trial (ClinicalTrials.gov, NCT04738487) evaluating the fixed-dose combination of vibostolimab and pembrolizumab (MK-7684A) versus pembrolizumab monotherapy, as a first-line treatment for patients with PD-L1 positive metastatic NSCLC. The primary endpoint is overall survival (OS) in participants with PD-L1 TPS ≥50%. Secondary endpoints include OS in participants with PD-L1 TPS ≥1% and TPS 1-49%, progression-free survival (PFS), overall response rate (ORR), duration of response (DOR), safety and quality of life. The trial enrolled 1,264 patients who were randomized (1:1) to receive:

• Vibostolimab/pembrolizumab fixed-dose combination (pembrolizumab 200 mg and vibostolimab 200 mg intravenously [IV] every three weeks [Q3W] for up to 35 administrations); or
• Pembrolizumab (200 mg IV Q3W for up to 35 administrations)

About KeyVibe-007 KeyVibe-007 is a randomized, double-blind Phase 3 trial (ClinicalTrials.gov, NCT05226598) evaluating the fixed-dose combination of vibostolimab and pembrolizumab with chemotherapy in treatment-naïve patients with metastatic NSCLC. The primary endpoint is OS in participants with PD-L1 TPS ≥1%. Secondary endpoints include OS in all participants, PFS, ORR and DOR in TPS ≥ 1% and all participants, safety and patient reported outcomes. The trial enrolled 739 patients who were randomized (1:1) to receive:

• Vibostolimab/pembrolizumab fixed-dose combination (pembrolizumab 200mg and vibostolimab 200 mg IV) plus platinum doublet chemotherapy (Q3W for 4 cycles​); then vibostolimab/pembrolizumab (200mg/200mg IV)​ for up to 31 cycles​ (plus pemetrexed 500mg/m2 Q3W maintenance for nonsquamous histology)​
• Pembrolizumab (200 mg IV) plus platinum doublet chemotherapy (Q3W for 4 cycles​); then pembrolizumab ​(200mg IV)​ for up to 31 cycles ​(plus pemetrexed 500mg/m2 Q3W maintenance for nonsquamous histology)

About KeyVibe-006 KeyVibe-006 is a randomized, open-label Phase 3 trial (ClincialTrials.gov, NCT05298423) evaluating the fixed-dose combination of vibostolimab and pembrolizumab with concurrent chemoradiotherapy followed by vibostolimab and pembrolizumab versus concurrent chemoradiotherapy followed by durvalumab in patients with stage III NSCLC. The primary endpoints are PFS and OS for all participants and for participants with TPS ≥ 1%. The secondary endpoints are ORR, DOR, safety and patient reported outcomes. The trial enrolled approximately 580 patients who were randomized (1:1) to receive:

• Vibostolimab/pembrolizumab (200mg/200mg IV)​ plus platinum doublet (1 cycle); then platinum doublet plus vibostolimab/pembrolizumab (2 cycles) plus thoracic radiotherapy; then vibostolimab/pembrolizumab (200mg/200mg IV Q3W for 17 cycles); or
• Platinum doublet (1 cycle); then platinum doublet (2 cycles) plus thoracic radiotherapy; then durvalumab​ (10 mg/kg Q2W ​for 26 cycles​)

About KEYFORM-008 KEYFORM-008 is a randomized, open-label Phase 3 trial (ClinicalTrials.gov, NCT05508867) evaluating the fixed-dose combination of favezelimab and pembrolizumab (MK-4280A) versus physician's choice chemotherapy for the treatment of patients with PD-1 relapsed or refractory classical Hodgkin lymphoma. The primary endpoint is PFS per Lugano Response Criteria as assessed by Blinded Independent Central Review (BICR). The secondary endpoints are OS, ORR, DOR and safety. The trial enrolled 169 patients who were randomized (1:1) to receive:

• Favezelimab/pembrolizumab (800 mg/200 mg IV on day 1, then Q3W for up to 35 infusions); or
• Physician's choice of either bendamustine (between 90-120 mg/m2 IV on day 1 and day 2 of either a 3- or 4-week cycle for up to 6 cycles); or gemcitabine (between 800-1,200 mg/m2 IV on day 1 and day 8 of a Q3W cycle for up to 6 cycles)

About vibostolimab Vibostolimab (MK-7684) is an investigational humanized anti-TIGIT antibody discovered and developed by Merck. Vibostolimab restores antitumor activity by blocking the TIGIT receptor from binding to its ligands (CD112 and CD155), thereby activating T lymphocytes that help destroy tumor cells.

About favezelimab Favezelimab (MK-4280) is an investigational anti-lymphocyte activation gene-3 (LAG-3) antibody. LAG-3 is a cell surface immunomodulatory receptor expressed on various immune cells that down-regulates T cell proliferation and activation. Favezelimab aims to restore T cell effector function by preventing LAG-3 from binding to its primary ligand, major histocompatibility complex (MHC) class II molecules.

About KEYTRUDA® (pembrolizumab) injection, 100 mg KEYTRUDA is an anti-programmed death receptor-1 (PD-1) therapy that works by increasing the ability of the body’s immune system to help detect and fight tumor cells. KEYTRUDA is a humanized monoclonal antibody that blocks the interaction between PD-1 and its ligands, PD- L1 and PD-L2, thereby activating T lymphocytes which may affect both tumor cells and healthy cells.

Merck has the industry’s largest immuno-oncology clinical research program. There are currently more than 1,600 trials studying KEYTRUDA across a wide variety of cancers and treatment settings. The KEYTRUDA clinical program seeks to understand the role of KEYTRUDA across cancers and the factors that may predict a patient's likelihood of benefitting from treatment with KEYTRUDA, including exploring several different biomarkers.

Selected KEYTRUDA® (pembrolizumab) Indications in the U.S. Non-Small Cell Lung Cancer KEYTRUDA, in combination with pemetrexed and platinum chemotherapy, is indicated for the first-line treatment of patients with metastatic nonsquamous non-small cell lung cancer (NSCLC), with no EGFR or ALK genomic tumor aberrations.

KEYTRUDA, in combination with carboplatin and either paclitaxel or paclitaxel protein-bound, is indicated for the first-line treatment of patients with metastatic squamous NSCLC.

KEYTRUDA, as a single agent, is indicated for the first-line treatment of patients with NSCLC expressing PD-L1 [Tumor Proportion Score (TPS) ≥1%] as determined by an FDA-approved test, with no EGFR or ALK genomic tumor aberrations, and is:

• Stage III where patients are not candidates for surgical resection or definitive chemoradiation, or
• metastatic.

KEYTRUDA, as a single agent, is indicated for the treatment of patients with metastatic NSCLC whose tumors express PD-L1 (TPS ≥1%) as determined by an FDA-approved test, with disease progression on or after platinum-containing chemotherapy. Patients with EGFR or ALK genomic tumor aberrations should have disease progression on FDA-approved therapy for these aberrations prior to receiving KEYTRUDA.

KEYTRUDA is indicated for the treatment of patients with resectable (tumors ≥4 cm or node positive) NSCLC in combination with platinum-containing chemotherapy as neoadjuvant treatment, and then continued as a single agent as adjuvant treatment after surgery.

KEYTRUDA, as a single agent, is indicated as adjuvant treatment following resection and platinum-based chemotherapy for adult patients with Stage IB (T2a ≥4 cm), II, or IIIA NSCLC.

Classical Hodgkin Lymphoma KEYTRUDA is indicated for the treatment of adult patients with relapsed or refractory classical Hodgkin lymphoma (cHL).

KEYTRUDA is indicated for the treatment of pediatric patients with refractory cHL, or cHL that has relapsed after 2 or more lines of therapy.

See additional selected KEYTRUDA indications in the U.S. after the Selected Important Safety Information.

Selected Important Safety Information for KEYTRUDA Severe and Fatal Immune-Mediated Adverse Reactions KEYTRUDA is a monoclonal antibody that belongs to a class of drugs that bind to either the programmed death receptor-1 (PD-1) or the programmed death ligand 1 (PD-L1), blocking the PD-1/PD-L1 pathway, thereby removing inhibition of the immune response, potentially breaking peripheral tolerance and inducing immune-mediated adverse reactions. Immune-mediated adverse reactions, which may be severe or fatal, can occur in any organ system or tissue, can affect more than one body system simultaneously, and can occur at any time after starting treatment or after discontinuation of treatment. Important immune-mediated adverse reactions listed here may not include all possible severe and fatal immune-mediated adverse reactions.

Monitor patients closely for symptoms and signs that may be clinical manifestations of underlying immune-mediated adverse reactions. Early identification and management are essential to ensure safe use of anti–PD-1/PD-L1 treatments. Evaluate liver enzymes, creatinine, and thyroid function at baseline and periodically during treatment. For patients with TNBC treated with KEYTRUDA in the neoadjuvant setting, monitor blood cortisol at baseline, prior to surgery, and as clinically indicated. In cases of suspected immune-mediated adverse reactions, initiate appropriate workup to exclude alternative etiologies, including infection. Institute medical management promptly, including specialty consultation as appropriate.

Withhold or permanently discontinue KEYTRUDA depending on severity of the immune-mediated adverse reaction. In general, if KEYTRUDA requires interruption or discontinuation, administer systemic corticosteroid therapy (1 to 2 mg/kg/day prednisone or equivalent) until improvement to Grade 1 or less. Upon improvement to Grade 1 or less, initiate corticosteroid taper and continue to taper over at least 1 month. Consider administration of other systemic immunosuppressants in patients whose adverse reactions are not controlled with corticosteroid therapy.

Immune-Mediated Pneumonitis KEYTRUDA can cause immune-mediated pneumonitis. The incidence is higher in patients who have received prior thoracic radiation. Immune-mediated pneumonitis occurred in 3.4% (94/2799) of patients receiving KEYTRUDA, including fatal (0.1%), Grade 4 (0.3%), Grade 3 (0.9%), and Grade 2 (1.3%) reactions. Systemic corticosteroids were required in 67% (63/94) of patients. Pneumonitis led to permanent discontinuation of KEYTRUDA in 1.3% (36) and withholding in 0.9% (26) of patients. All patients who were withheld reinitiated KEYTRUDA after symptom improvement; of these, 23% had recurrence. Pneumonitis resolved in 59% of the 94 patients.

Pneumonitis occurred in 8% (31/389) of adult patients with cHL receiving KEYTRUDA as a single agent, including Grades 3-4 in 2.3% of patients. Patients received high-dose corticosteroids for a median duration of 10 days (range: 2 days to 53 months). Pneumonitis rates were similar in patients with and without prior thoracic radiation. Pneumonitis led to discontinuation of KEYTRUDA in 5.4% (21) of patients. Of the patients who developed pneumonitis, 42% interrupted KEYTRUDA, 68% discontinued KEYTRUDA, and 77% had resolution.

Pneumonitis occurred in 7% (41/580) of adult patients with resected NSCLC who received KEYTRUDA as a single agent for adjuvant treatment of NSCLC, including fatal (0.2%), Grade 4 (0.3%), and Grade 3 (1%) adverse reactions. Patients received high-dose corticosteroids for a median duration of 10 days (range: 1 day to 2.3 months). Pneumonitis led to discontinuation of KEYTRUDA in 26 (4.5%) of patients. Of the patients who developed pneumonitis, 54% interrupted KEYTRUDA, 63% discontinued KEYTRUDA, and 71% had resolution.

Immune-Mediated Colitis KEYTRUDA can cause immune-mediated colitis, which may present with diarrhea. Cytomegalovirus infection/reactivation has been reported in patients with corticosteroid-refractory immune-mediated colitis. In cases of corticosteroid-refractory colitis, consider repeating infectious workup to exclude alternative etiologies. Immune-mediated colitis occurred in 1.7% (48/2799) of patients receiving KEYTRUDA, including Grade 4 (

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