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Phase Ib/II Study of Bexmarilimab Plus Doxorubicin in Adults with Metastatic Soft Tissue Sarcoma

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

The study focuses on adults with metastatic soft tissue sarcoma, a rare type of cancer that has spread beyond its original location and cannot be cured with surgery. The treatment being tested combines two medicines given through a vein: bexmarilimab, an experimental drug that helps the immune system recognize cancer cells, and doxorubicin, a chemotherapy agent that kills rapidly growing cells.

The purpose of the study is to determine whether the combination of these two medicines is safe and works better than chemotherapy alone in slowing the disease. In the early part of the trial, different dose levels are tried to find the highest amount that can be given without causing unacceptable side effects, known as the “maximum tolerated dose.” Later, participants are randomly assigned to receive either the combination or the chemotherapy alone, and the time they live without the cancer getting worse, called “progression‑free survival,” is measured.

Participants would visit the clinic for regular intravenous infusions of the study drugs, followed by routine check‑ups that may include physical exams and imaging tests such as scans to see how the tumor is responding. The study lasts for several months, with visits scheduled to monitor health, record any side effects, and assess whether the cancer is stable, shrinking, or growing.

The research process

The trial runs in 7 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Enrollment and baseline assessments

    After providing consent, you will be entered into the study and assigned a study identification number.

    Initial assessments will include a review of medical history, physical examination, blood tests, and imaging studies to document the extent of soft‑tissue sarcoma.

  2. Step 2

    Randomization and assignment to treatment group

    The study team will randomly assign you to receive the combination of bexmarilimab and doxorubicin according to the phase ib dose‑escalation or phase ii expansion plan.

  3. Step 3

    Administration of study medications

    On each treatment day, bexmarilimab will be given as an intravenous infusion (solution for infusion).

    On the same day, doxorubicin will be given as an intravenous infusion.

    The exact dose, frequency, and number of cycles will follow the protocol schedule determined by the study investigators.

  4. Step 4

    Monitoring for safety and response

    After each infusion, you will undergo monitoring that may include vital‑sign checks, blood tests, and observation for any adverse effects.

    Periodic imaging (such as CT or MRI) will be performed to evaluate tumor response according to standard criteria (recist v1.1).

  5. Step 5

    Dose adjustment or escalation (phase ib only)

    If you are in the dose‑escalation portion, the study team may adjust the dose of bexmarilimab based on observed toxicities to determine the maximum tolerated dose and the recommended phase ii dose.

  6. Step 6

    Continuation of treatment cycles

    Treatment cycles will continue as prescribed until disease progression, unacceptable toxicity, or completion of the planned number of cycles as defined in the protocol.

  7. Step 7

    Post‑treatment follow‑up

    After the last treatment, you will have scheduled follow‑up visits to assess long‑term outcomes such as progression free survival (time from randomization to tumor growth or death) and overall survival.

    Follow‑up may include regular imaging and clinical evaluations according to the study schedule.

Who can join the trial?

16 criteria

  • You must be able to understand the study purpose and sign a written consent form before any study procedures begin.
  • You must be 18 years of age or older at the time you sign the consent form.
  • You must be able to travel to the study site for treatment and follow‑up visits.
  • If you are a woman who could become pregnant and are sexually active with a male partner who is not sterilized, you must have a negative pregnancy test within 14 days before starting treatment and agree to use a highly effective birth‑control method from screening until 7 months after the last dose. You also cannot donate eggs or breast‑feed during this time.
  • If you are a man who is sexually active with a woman who could become pregnant, you must be surgically sterile (e.g., vasectomy) or use an acceptable form of contraception from screening until 4 months after the last dose, and you may not donate or bank sperm during this period.
  • You must have a diagnosis of soft tissue sarcoma (a type of cancer that starts in the body's connective tissues) that has spread (called metastatic) and cannot be cured with standard treatment.
  • For the early‑phase part of the study (phase Ib dose escalation), your cancer must be confirmed by tissue analysis (histology) and you must have received no more than three previous lines of cancer therapy. You must not have received the chemotherapy drug doxorubicin before, although it may be recommended for your disease.
  • For the later‑phase parts of the study (phase Ib dose expansion and phase II), your metastatic soft tissue sarcoma must be one of the following types: undifferentiated pleomorphic sarcoma (UPS), myxofibrosarcoma (MFS), dedifferentiated liposarcoma (DDLPS), myxoid liposarcoma (MLPS), or leiomyosarcoma (LMS). You must not have received any treatment for advanced disease before entering the study.
  • Your cancer must be measurable according to RECIST v.1.1 criteria (a standard way doctors measure tumor size on scans).
  • Your blood tests must show adequate function of the bone marrow, liver, and kidneys:
    • Bone marrow: white blood cell count (absolute neutrophil count) at least 1,000 per microliter, platelet count at least 100 × 10⁹/L, and hemoglobin (the protein that carries oxygen) at least 9.0 g/dL.
    • Liver: albumin ≥ 2.5 g/dL, bilirubin ≤ 1.5 times the normal limit (up to 3 times if you have Gilbert’s syndrome), alkaline phosphatase ≤ 2.5 times normal, and AST/ALT enzymes ≤ 2.5 times normal (or ≤ 5 times if you have liver metastases). Blood clotting tests (PT/INR or PTT) must be less than 1.5 times normal (or ≤ 2.0 if you are on preventive blood thinners).
    • Kidneys: creatinine ≤ 1.5 times the normal limit, or a calculated creatinine clearance of at least 40 mL/min.
    • Any side effects from previous cancer treatments must have resolved to mild (grade 1) or less, except for hair loss or other effects that the doctor decides are not a safety risk.
    • You must be willing and able to provide blood samples for drug‑level testing (required for phase Ib) and to allow use of existing tumor tissue blocks or a fresh biopsy taken before treatment for research purposes.
    • Your overall health status must be rated as 0 or 1 on the ECOG performance status scale (0 = fully active, 1 = restricted in physically strenuous activity but able to do light work).
    • You must have a life expectancy of at least 12 weeks at the time of screening.

Who cannot join the trial?

27 criteria

  • Being in another clinical trial (either interventional or observational) until the study’s safety visit.
  • Having had a major surgery or a serious injury within the 14 days before the first dose, or expecting to need major surgery while on the study treatment.
  • Needing a systemic corticosteroid (meaning a steroid taken by mouth or injection at a dose of 10 mg or more of prednisone‑equivalent each day) or any other medication that suppresses the immune system. (Steroid creams, nasal sprays, inhalers, or eye drops are allowed.)
  • Having active heart disease or a past history of heart problems, including:
    • Recent heart attacks, ongoing chest pain (angina), or worsening heart failure (New York Heart Association NYHA Class II‑IV) within the past six months.
    • Inflammation of the heart lining (pericarditis).
    • Heart’s pumping ability (left ventricular LVEF) below 50% as measured by a special scan or ultrasound.
    • Significant irregular heart rhythms that cause symptoms or need treatment, such as certain types of ventricular tachycardia or uncontrolled atrial fibrillation.
    • Abnormally long heart‑beat interval on an ECG (QT interval corrected by Fridericia’s formula, QTcF, longer than 470 ms).
    • Family history of a condition that causes a long QT interval or unexplained sudden death before age 40.
    • Having chronic ulcers or serious liver disease that scores a Child‑Pugh classification of C or higher.
    • Being pregnant, breastfeeding, or not willing to use a highly effective form of birth control as required by the study.
    • Having any serious medical problem or abnormal lab test result that the doctor believes makes participation unsafe.
    • Current infection with hepatitis B (HBV) or hepatitis C (HCV) viruses. (Past or resolved infections may be allowed after specific testing.)
    • Having an active primary immune deficiency, or HIV infection with a detectable amount of virus in the blood. (HIV patients with an undetectable viral load on stable therapy may be allowed if their medication does not include certain enzyme‑affecting drugs called CYP3A4 inhibitors or inducers.)
    • Having any other uncontrolled infection at the time of enrollment.
    • Receiving a live or weakened (attenuated) vaccine within 30 days before the first study dose.
    • Having received any approved or experimental cancer therapy within 14 days before starting the study drug.
    • Having a history of uncontrolled seizures, brain disorders, or serious psychiatric problems that could affect safety or the ability to follow the study schedule.
    • Having a known substance‑abuse problem or any other severe, uncontrolled medical condition that the doctor thinks would make participation unsafe.
    • Being unable or unwilling to follow the study requirements, as judged by the investigator.
    • Having previously been treated with anthracycline chemotherapy (a class of drugs that includes doxorubicin) for either localized or advanced disease.
    • Having previously received immune‑checkpoint inhibitor therapy (a type of cancer immunotherapy) for either localized or advanced disease.
    • For the dose‑expansion and phase II parts of the trial: having received any prior treatment for advanced disease.
    • Having active, uncontrolled, or symptomatic cancer spread to the brain or spinal fluid (known as CNS metastases or leptomeningeal disease). (Patients whose brain lesions were treated curatively, are stable for at least 60 days, and are not on steroids or anticonvulsants may be allowed.)
    • Being diagnosed with bone sarcoma, locally aggressive sarcoma, gastrointestinal stromal tumor (GIST), or Kaposi sarcoma.
    • Having another cancer (a concurrent malignancy) or a cancer diagnosed within the past five years, except for certain low‑risk skin cancers (cervical carcinoma in situ, basal cell carcinoma, or squamous cell carcinoma of the skin) that have been treated with curative intent.
    • Having a known allergy or severe reaction to any investigational drug or any of its ingredients.
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Investigated drugs

  • Bexmarilimab

    is an experimental medicine that is given through an IV infusion. In this study it is being tested to find the safest and most effective dose when it is used together with a standard chemotherapy drug. The goal is to see if adding bexmarilimab can help slow down the growth of metastatic soft‑tissue sarcoma and improve how long patients live without the disease getting worse.

  • Doxorubicin

    is a chemotherapy drug that is also given by IV infusion. It is a well‑known treatment for many cancers, including soft‑tissue sarcoma. In this trial, doxorubicin is used as the backbone therapy that all participants receive, and it is also the drug that the new combination (with bexmarilimab) is compared against to determine if the addition of bexmarilimab provides extra benefit.

What is already known about the treatment

  • Bexmarilimab

    This investigational medicine is given as an intravenous infusion in a solution for infusion. It is currently being studied in early‑phase clinical trials and has orphan‑drug status for rare soft‑tissue sarcoma. It is intended to help the immune system attack cancer by blocking a protein that tells immune cells to stand down. Bexmarilimab belongs to the class of monoclonal antibodies known as immune‑checkpoint inhibitors.

  • Doxorubicin

    Doxorubicin is administered by intravenous infusion, usually as a short injection into a vein. It is an established chemotherapy drug that is approved for many types of cancer, including soft‑tissue sarcoma. It works by slipping between DNA strands and stopping cancer cells from copying their genetic material, which leads to cell death. Doxorubicin is classified as an anthracycline antibiotic chemotherapy agent.

Investigated diseases

  • Soft tissue sarcoma

    Soft tissue sarcoma is a cancer that starts in the muscles, fat, nerves, or blood vessels of the body. When it becomes advanced or metastatic, the tumor keeps growing and can spread to other parts of the body, forming new tumor sites. This spread often leads to a gradual increase in tumor size and number, affecting organ function over time.

  • Undifferentiated pleomorphic sarcoma

    Undifferentiated pleomorphic sarcoma is a type of soft tissue sarcoma that arises from connective tissue without a clear cell of origin. It typically appears as a fast‑growing lump and can invade nearby tissues. As the disease progresses, cancer cells may travel through the bloodstream to distant sites, creating additional tumors.

  • Myxofibrosarcoma

    Myxofibrosarcoma is a soft tissue sarcoma that develops in the fibro‑connective tissue and contains a gelatinous (myxoid) component. It often presents as a painless swelling that slowly enlarges. Over time, the tumor can infiltrate surrounding structures and spread to other organs, increasing the total number of lesions.

  • Dedifferentiated liposarcoma

    Dedifferentiated liposarcoma begins as a fatty tissue tumor that later transforms into a more aggressive, non‑fatty cancer. The tumor may initially feel firm and grow slowly, but the dedifferentiated portion tends to enlarge more rapidly. With progression, cancer cells can detach and establish new growths in distant locations.

  • Myxoid liposarcoma

    Myxoid liposarcoma is a cancer of fatty tissue that contains a soft, jelly‑like matrix. It usually forms a slow‑growing mass that can become larger and more diffuse over months. As it advances, tumor cells may travel through blood vessels, leading to additional tumors in other parts of the body.

  • Leiomyosarcoma

    Leiomyosarcoma is a cancer that originates from smooth muscle cells found in organs such as the uterus, gastrointestinal tract, or blood vessel walls. The tumor can expand locally, invading nearby tissues, and may later spread through the bloodstream to distant sites. This metastatic spread results in multiple tumor nodules that increase in size and number over time.

Trial detailsLast updated 7 Oct 2026
Age18+ yearsPhasePhase ITrial ID2025-525144-18-00Protocol codeMEDOPP0799Estimated enrolment278 patientsSponsorMedica Scientia Innovation Research S.L.

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