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Study of petosemtamab alone or with drug combination for patients with advanced colorectal cancer and other solid tumors

Verified siteRegistered drugNo placebo
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What is this trial about?

A plain-language summary of the goals, design and what participants do

This study focuses on treating patients with metastatic colorectal cancer and other advanced solid tumors. The main treatment being investigated is petosemtamab (also known as MCLA-158), which can be given either alone or combined with other medications. The additional medications that may be used in combination include pembrolizumab (KEYTRUDA), oxaliplatin, irinotecan, fluorouracil, and calcium folinate.

The purpose of this research is to evaluate how well patients respond to the treatment and to understand the safety of petosemtamab when used alone or in combination with other medications. The study is designed in two parts: the first part determines the right dose of the medication, while the second part tests the treatment in larger groups of patients.

During the study, participants will receive their assigned treatment through intravenous administration (delivery of medication directly into a vein). The medications will be given according to a specific schedule determined by the study protocol. Throughout the treatment period, patients will be monitored for their response to the therapy and any side effects that may occur.

The research process

The trial runs in 4 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Initial treatment preparation

    The treatment involves receiving multiple medications through intravenous administration (delivery directly into a vein)

    A healthcare provider will assess your general health condition and confirm your ECOG performance status (a measure of your ability to perform daily activities) is at level 0 or 1

  2. Step 2

    Treatment administration

    You will receive a combination of medications through intravenous infusion:

    - Petosemtamab (MCLA-158)

    - Pembrolizumab (Keytruda)

    - Calcium folinate

    - Irinotecan

    - Fluorouracil

    - Oxaliplatin

  3. Step 3

    Monitoring period

    Regular assessments will track your response to treatment

    Healthcare providers will monitor for any side effects or adverse reactions

    Your tumor response will be evaluated to determine if the treatment is effective

  4. Step 4

    Ongoing evaluation

    Regular checks of your overall health status

    Assessment of how long the treatment keeps working (Duration of Response)

    Monitoring of how long you remain without disease progression (Progression-Free Survival)

    The study continues until November 2027

Who can join the trial?

7 criteria

  • Patient must sign an informed consent form before any study procedures begin
  • Must be at least 18 years old when signing the consent form
  • For first-line head and neck cancer patients: Must be eligible for pembrolizumab (an immunotherapy drug) treatment and have tumors that express PD-L1 (a specific protein) with a CPS score of 1 or higher
  • For second/third-line head and neck cancer patients: Must have either: - Had cancer progression after receiving immunotherapy (anti-PD-(L)1 therapy), or - Been unable to tolerate immunotherapy, and - Had cancer progression after receiving platinum-based chemotherapy
  • For colorectal cancer patients: - Must have confirmed diagnosis of colon or rectal cancer that has spread (metastatic) or cannot be surgically removed - Must have normal RAS/RAF genes (not mutated) - Must not have received previous anti-EGFR therapy (a type of targeted treatment)
  • Must have good physical function status (ECOG score of 0 or 1, meaning able to perform daily activities with minimal assistance)
  • Must have adequate heart and organ function

Who cannot join the trial?

12 criteria

  • Prior treatment with EGFR (a protein involved in cell growth) targeting therapy in the last 4 weeks before starting the study
  • Active or untreated brain metastases (cancer that has spread to the brain)
  • History of another cancer within the past 3 years, except for successfully treated non-melanoma skin cancer or cervical cancer in situ (early-stage cancer)
  • Severe heart conditions, including: - Heart attack within past 6 months - Unstable angina (chest pain) - Heart failure requiring treatment
  • Active, uncontrolled infections requiring treatment
  • Known positive test for HIV, hepatitis B, or hepatitis C
  • Major surgery within 4 weeks before starting the study
  • Pregnant or breastfeeding women
  • Any condition that, in the opinion of the study doctor, would make participation unsafe
  • Unable to swallow oral medications
  • Severe kidney or liver problems
  • Current participation in other clinical trials
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Investigated drugs

Petosemtamab (also known as MCLA-158) is a medication being studied for treating advanced solid tumors. It is an experimental treatment that works by targeting specific proteins on cancer cells. This medication is being tested both as a standalone treatment and in combination with other therapies to determine how well it works against various types of solid tumors.

What is already known about the treatment

Petosemtamab - A novel investigational bispecific antibody administered through intravenous infusion, currently undergoing Phase 1/2 clinical trials for the treatment of metastatic colorectal cancer and advanced solid tumors. This medication works by targeting specific molecular pathways involved in cancer cell growth and survival, representing a targeted therapeutic approach in oncology. As a bispecific antibody, it is designed to engage two different molecular targets simultaneously, potentially offering enhanced therapeutic efficacy compared to traditional single-target antibodies, while its safety profile and optimal dosing are still being evaluated in clinical studies.

Investigated diseases

  • Metastatic Colorectal Cancer

    A condition where cancer that begins in the colon or rectum spreads to other parts of the body. The disease starts in the inner lining of the colon or rectum and can grow through several layers. Cancer cells can break away from the original tumor and travel through blood or lymph vessels to form new tumors in other organs. Common areas where colorectal cancer spreads include the liver, lungs, and peritoneum.

  • Malignant Solid Tumor

    A type of cancer that forms a mass of tissue without liquid or cysts. These abnormal cell growths can develop in various body tissues and organs. Solid tumors can increase in size and may spread to nearby tissues. The cells in these tumors multiply uncontrollably and can develop their own blood vessel network to support their growth. Unlike liquid cancers, these tumors form distinct masses that can often be felt or seen on imaging tests.

Trial detailsLast updated 7 Oct 2026
Age18+ yearsPhasePhase I/IITrial ID2024-513627-16-01Protocol codeMCLA-158-CL01Estimated enrolment590 patientsSponsorMerus B.V.

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