A Phase 3 Randomized, Open-label Study to Evaluate the Efficacy and Safety of Petosemtamab Plus Pembrolizumab vs Pembrolizumab in First-line Treatment of Recurrent or Metastatic PD-L1+ Head and Neck Squamous Cell Carcinoma

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Investigational drug late phase More information Active drug More information Moderate burden on patient More information

Trial Details

Sponsor: Merus N.V. (industry)

Phase: 3

Start date: Sept. 25, 2024

Planned enrollment: 500

Trial ID: NCT06525220
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More trial details at ClinicalTrials.gov More info

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Investigational Drug AI Analysis

chevron Show for: Petosemtamab (MCLA-158)

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Goal: To determine whether adding petosemtamab to pembrolizumab improves outcomes versus pembrolizumab alone as first-line therapy in patients with recurrent or metastatic PD-L1–positive head and neck squamous cell carcinoma (HNSCC).

Patients: Adults with histologically confirmed recurrent or metastatic HNSCC of the oropharynx, oral cavity, hypopharynx, or larynx that is not amenable to curative local therapy, PD-L1 CPS ≥1, ECOG 0–1, measurable disease by RECIST v1.1, and adequate organ function. No prior systemic therapy in the incurable recurrent/metastatic setting is allowed; prior multimodal therapy for locally advanced disease is permitted if progression occurred ≥6 months after last platinum dose. Prior anti–PD-(L)1 or anti-EGFR therapy is excluded, with a narrow exception for cetuximab given with radiotherapy if progression was >1 year after the last dose. Key exclusions include active/symptomatic CNS disease, uncontrolled comorbidities, significant cardiac disease, active autoimmune disease requiring immunosuppression, and nasopharyngeal or sinonasal primaries.

Design: Phase 3, randomized, open-label, parallel-group trial enrolling approximately 500 participants. Patients are randomized to petosemtamab plus pembrolizumab or pembrolizumab monotherapy as first-line treatment. Stratification factors are not listed here but responses will be assessed centrally by BICR using RECIST v1.1 for key efficacy endpoints.

Treatments: Experimental arm: petosemtamab plus pembrolizumab. Petosemtamab (MCLA-158) is a human IgG1 bispecific antibody targeting EGFR and LGR5. It blocks EGFR ligand binding and promotes EGFR internalization and degradation selectively in LGR5-positive tumor cells, with enhanced Fc-mediated effector function (ADCC/ADCP). Early-phase data in first-line PD-L1–positive r/m HNSCC combined with pembrolizumab have shown promising activity, with interim reports describing ORR around 63% and manageable toxicity, including infusion-related reactions mainly on first infusion. Monotherapy petosemtamab in pretreated r/m HNSCC demonstrated ORR around 36–40% in interim datasets, supporting further evaluation. Control arm: pembrolizumab monotherapy, standard first-line immunotherapy for PD-L1–positive r/m HNSCC.

Outcomes: Co-primary endpoints are overall survival and objective response rate by BICR per RECIST v1.1. Key secondary endpoints include progression-free survival, duration of response, clinical benefit rate, and corresponding investigator-assessed RECIST endpoints; safety and tolerability (TEAEs, serious TEAEs, dose modifications, and discontinuations); health-related quality of life; pharmacokinetics; and anti-drug antibody incidence. Time frames range up to approximately 2 years for efficacy and QoL, up to 3 years for overall survival, and up to 30 days post last dose for safety and immunogenicity.

Burden on patient: Moderate. Requirements include baseline and on-treatment imaging per RECIST, a mandatory recent tumor biopsy if adequate archival tissue is not available, regular clinic visits for intravenous infusions in both arms, and safety labs. The experimental arm may involve additional pharmacokinetic sampling during the first six cycles and monitoring for infusion-related reactions, particularly at the first dose, which can lengthen infusion visits. Overall visit frequency and imaging are similar to standard-of-care pembrolizumab-based management in this setting, but added PK draws and infusion observation increase time on site, leading to a moderate, not high, burden.

Last updated: Oct 2025

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