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NCT Number: NCT05217446

A Study of Encorafenib Plus Cetuximab Taken Together With Pembrolizumab Compared to Pembrolizumab Alone in People With Previously Untreated Metastatic Colorectal Cancer

The purpose of this study is to learn about the effects of three study medicines (encorafenib, cetuximab, and pembrolizumab) given together for the treatment of colorectal cancer that:

* is metastatic (spread to other parts of the body); * has the condition of genetic hypermutability (tendency to mutation) or impaired DNA mismatch repair (MMR) * has a certain type of abnormal gene called "BRAF" and; * has not received prior treatment.

All participants in this study will receive pembrolizumab at the study clinic as an intravenous (IV) infusion (given directly into a vein) at the study clinic.

In addition, half of the participants will take encorafenib by mouth at home every day and cetuximab by IV infusion at the study clinic.

The study team will monitor how each participant is doing with the study treatment during regular visits at the study clinic.

Active, Not Recruiting

This study is active but is not currently recruiting participants.

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Key information

Conditions

Metastatic Colorectal Cancer Colonic Diseases Colonic Neoplasms Colorectal Neoplasms Digestive System Diseases Digestive System Neoplasms Gastrointestinal Diseases Gastrointestinal Neoplasms Intestinal Diseases Intestinal Neoplasms Neoplasms Neoplasms by Site Rectal Diseases Rectal Neoplasms

Age range

16 year and older

Sex eligibility

All sexes

Study type

Interventional

Phase

Phase 2

Primary location

Austin Health, Heidelberg, Victoria, Australia

Loading trial locations.

Who can participate

Healthy volunteers accepted: No

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • Locally confirmed microsatellite instability-high/ deficient mismatch repair (MSI-H/dMMR) stage IV colorectal carcinoma
  • Locally confirmed BRAF V600E mutation in tumor tissue or blood
  • Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1
  • Have not received prior systemic regimens for metastatic disease.
  • Measurable disease per RECIST 1.1
  • Adequate organ function

Exclusion criteria

  • Colorectal adenocarcinoma that is RAS mutant or for which RAS mutation status is unknown
  • Known active central nervous system metastases and/or carcinomatous meningitis; leptomeningeal disease
  • Immunodeficiency or active autoimmune disease requiring systemic treatment in the past 2 years
  • Presence of acute or chronic pancreatitis
  • Clinically significant cardiovascular diseases (eg, thromboembolic or cerebrovascular accident events ≤ 12 wks prior)
  • Received a live or live-attenuated vaccine within 30 days of planned start of study medication
  • Previous treatment with any selective BRAF inhibitor (eg, encorafenib, dabrafenib, vemurafenib, XL281/BMS-908662) or any epidermal growth factor receptor (EGFR) inhibitor (eg, cetuximab, panitumumab).
  • Previous treatment with an immune checkpoint inhibitor (eg, anti-programmed cell death [PD-1], anti-PD-L1 or anti-PD-L2 agent); or with an agent directed to another stimulatory or co-inhibitory T-cell receptor (eg, CTLA-4, OX 40, CD137).

Treatment and study plan

Encorafenib

Drug

capsule

Other names: PF-07263896 LGX818 ONO-7702 W0090

Cetuximab

Biological

IV

Other names: Erbitux

Pembrolizumab

Biological

IV

Other names: Keytruda®, MK-3475

Primary outcomes

  1. Progression-free Survival (PFS)

    Time frame: Duration of study, approximately 45 months

    PFS per investigator, defined as the time from randomization until PD based on investigator assessment per Response Evaluation Criteria in Solid Tumors (RECIST) v1.1 or death due to any cause, whichever occurs first:

Secondary outcomes

  1. Incidence of adverse events

    Time frame: Duration of study, approximately 45 months

    Incidence and severity of AEs graded according to the NCI CTCAE v4.03: encorafenib and cetuximab + pembrolizumab (Arm A) vs pembrolizumab (Arm B)

  2. Overall Survival (OS)

    Time frame: Duration of study, approximately 45 months

    OS is defined as the time from the date of randomization to the date of death due to any cause: encorafenib and cetuximab + pembrolizumab (Arm A) vs pembrolizumab (Arm B)

  3. Objective Response (OR)

    Time frame: Duration of study, approximately 45 months

    OR is defined as a CR or PR per RECIST version 1.1 recorded from the date of randomization until date of first documentation of PD, death, or start of new anti-cancer therapy: encorafenib and cetuximab + pembrolizumab (Arm A) vs pembrolizumab (Arm B)

Sponsors and collaborators

Lead sponsor

Pfizer

Industry

Collaborators

  • Eli Lilly and Company
  • Merck KGaA, Darmstadt, Germany
  • Merck Sharp & Dohme LLC

Registry information

Official study title

A PHASE 2, RANDOMIZED, OPEN-LABEL STUDY OF ENCORAFENIB AND CETUXIMAB PLUS PEMBROLIZUMAB VERSUS PEMBROLIZUMAB ALONE IN PARTICIPANTS WITH PREVIOUSLY UNTREATED BRAF V600E-MUTANT, MSI H/DMMR METASTATIC COLORECTAL CANCER

Acronym: SEAMARK

Important dates

Study start
2022
Primary completion
2026
Study completion
2027
First posted
Feb 1, 2022
Registry last updated
Jul 31, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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