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Petosemtamab

Phase 3

Head and Neck Squamous Cell Carcinoma | Small molecule | Oncology |Merus N.V.|Last Updated: Aug 31, 2026

Success Probability

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Trial Design

RandomizedACTIVE_CONTROLLEDDMC
Total Trials2
Total Enrollment1,321

FDA Designations

BREAKTHROUGH_THERAPYFAST_TRACK

Clinical trial landscape

Petosemtamab · 2 trials · 1 indication

Phase 3 2
NCT06525220A Phase 3 Study to Evaluate Petosemtamab Plus Pembrolizumab vs Pembrolizumab in First-line Treatment of Head and Neck Cancer (LiGeR - HN1)Head and Neck Squamous Cell Carcinoma
RECRUITING700 Analytics
NCT06496178A Phase 3 Study to Evaluate Petosemtamab Compared With Investigator's Choice Monotherapy in Previously Treated Head and Neck Squamous Cell Carcinoma Patients (LiGeR-HN2)Head and Neck Squamous Cell Carcinoma
ACTIVE NOT_RECRUITING621 Analytics
PHASE3RECRUITING
A Phase 3 Study to Evaluate Petosemtamab Plus Pembrolizumab vs Pembrolizumab in First-line Treatment of Head and Neck Cancer (LiGeR - HN1)
Head and Neck Squamous Cell CarcinomaUnlock trial analytics
PHASE3ACTIVE NOT_RECRUITING
A Phase 3 Study to Evaluate Petosemtamab Compared With Investigator's Choice Monotherapy in Previously Treated Head and Neck Squamous Cell Carcinoma Patients (LiGeR-HN2)
Head and Neck Squamous Cell CarcinomaUnlock trial analytics

Study Endpoints

Primary Endpoints

Overall Survival (OS)
Up to approximately 3 years
Objective Response Rate (ORR) per Response Evaluation Criteria in Solid Tumors (RECIST) v1.1 as assessed by blinded independent central review (BICR)
Up to approximately 2 years

Secondary Endpoints

Progression Free Survival (PFS) per RECIST v1.1 as assessed by BICR
Up to approximately 2 years
Duration of Response (DOR) per RECIST v1.1 as assessed by BICR
Up to approximately 2 years
Clinical benefit rate per RECIST v1.1 as assessed by BICR
Up to approximately 2 years
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Study Design & Arms

AllocationRANDOMIZED
MaskingNONE
ModelPARALLEL
PurposeTREATMENT

Treatment Arms

ArmTypeDescription
Petosemtamab + PembrolizumabEXPERIMENTALCombination Therapy
PembrolizumabACTIVE_COMPARATORMonotherapy
MCLA-158EXPERIMENTAL -
Investigator's ChoiceACTIVE_COMPARATOR -

Interventions

NameTypeDescription
PetosemtamabDRUGMCLA-158
PembrolizumabDRUGHumanized Antibody
Investigator's ChoiceDRUGCetuximab
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Eligibility Criteria

Age Range18 Years to N/A
SexALL
Healthy VolunteersNo
Study Sites205

Inclusion Criteria: 1. Signed ICF before initiation of any study procedures 2. Age ≥ 18 years at signing of ICF 3. Histologically confirmed HNSCC with evidence of metastatic or locally recurrent disease not amenable to local therapy with curative intent. 4. The eligible HNSCC primary tumor location...

Countries:United StatesArgentinaAustraliaBelgiumBrazilCanadaChileCroatiaCzechiaFranceGermanyGreeceHungaryIsraelItalyJapanLithuaniaMalaysiaMexicoNetherlandsPolandPortugalSouth KoreaSpainTaiwanThailandTurkey (Türkiye)United KingdomSwitzerland
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Recent Changes (Last 90 Days)

MEDIUMAug 31, 2026NCT06496178Status: RECRUITING → ACTIVE_NOT_RECRUITING
MEDIUMAug 31, 2026NCT06496178Status: RECRUITING → ACTIVE_NOT_RECRUITING
LOWJul 17, 2026NCT06496178lastUpdatePostDate: changed
LOWJul 17, 2026NCT06496178lastUpdatePostDate: changed
LOWJul 17, 2026NCT06496178lastUpdatePostDate: changed

Frequently asked questions about Petosemtamab

What is Petosemtamab used for in Head and Neck Squamous Cell Carcinoma?

Petosemtamab is an investigational antibody being studied for the treatment of Head and Neck Squamous Cell Carcinoma. It is currently in Phase 3 clinical trials for this indication, including as a monotherapy in previously treated patients and in combination with pembrolizumab as a first-line treatment.

What does Petosemtamab target?

Petosemtamab is a monoclonal antibody, indicated by its -mab suffix. It is being developed by Merus N.V. for oncology applications, specifically targeting Head and Neck Squamous Cell Carcinoma. The specific molecular target has not been disclosed in the available clinical trial information.

Who makes Petosemtamab?

Petosemtamab is being developed by Merus N.V., a biopharmaceutical company listed on the NASDAQ under the ticker symbol MRUS. The company is conducting Phase 3 clinical trials for this drug in Head and Neck Squamous Cell Carcinoma.

What phase is Petosemtamab in?

Petosemtamab is in Phase 3 clinical development. It is an investigational drug and has not been approved by the FDA. It has received Breakthrough Therapy and Fast Track designations from the FDA for its development in Head and Neck Squamous Cell Carcinoma.

What clinical trials is Petosemtamab in?

Petosemtamab is being evaluated in two Phase 3 trials. NCT06496178 compares petosemtamab to investigator's choice monotherapy in previously treated Head and Neck Squamous Cell Carcinoma patients. NCT06525220 evaluates petosemtamab plus pembrolizumab versus pembrolizumab alone as first-line treatment. Both trials are active, with a combined enrollment of about 1,300 patients.

Is Petosemtamab the same as pembrolizumab?

No, Petosemtamab is not the same as pembrolizumab. Petosemtamab is an investigational antibody being developed by Merus N.V., while pembrolizumab is a separate, approved immunotherapy. In one Phase 3 trial, petosemtamab is being studied in combination with pembrolizumab, but they are distinct drugs.