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

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What is this study about?

The trial looks at adults with advanced or metastatic soft tissue sarcoma, a rare cancer that starts in the body’s connective tissues and has spread beyond the original site. The study tests a combination of two medicines given through a vein (intravenous infusion): the experimental antibody bexmarilimab and the chemotherapy drug doxorubicin. Both are delivered as a liquid solution that is slowly injected into the bloodstream.

The purpose is to find the safest and most effective dose of the antibody when used together with the chemotherapy and to see whether the combination can keep the cancer from growing longer than chemotherapy alone. Participants will first receive a series of dose‑finding visits where the amount of the antibody is increased step by step while monitoring for side effects. After the appropriate dose is chosen, a larger group will be treated with the fixed dose of both medicines and will be followed for several months to see how long the disease stays stable or shrinks. Treatment cycles are repeated every few weeks, and regular scans are done to check tumor size.

The main outcome that will be measured is the time the disease does not get worse, called progression free survival, which is determined by comparing scans taken at different times using the standard criteria known as RECIST. Additional outcomes include how many participants experience tumor shrinkage and how long any response lasts. The study follows participants for up to a year after treatment to gather safety information and overall health status.

1 enrollment

you sign the informed consent form and receive a study identification number.

2 baseline evaluation

initial medical examinations, laboratory tests, and imaging scans are performed to confirm the disease status and eligibility for the study.

3 first treatment cycle

you receive an intravenous infusion of bexmarilimab and an intravenous infusion of doxorubicin. the exact dose, frequency, and duration are defined by the study protocol.

4 subsequent treatment cycles

you continue to receive the same infusions on a regular schedule as specified by the protocol. each cycle includes monitoring for side effects and laboratory assessments before the next infusion.

5 dose escalation (phase ib)

during the early part of the study, the amount of bexmarilimab may be increased stepwise to determine the maximum tolerated dose. safety and side‑effect data are collected after each dose level.

6 dose expansion (phase ii)

once the maximum tolerated dose is identified, additional participants receive that dose together with doxorubicin to evaluate the effectiveness of the combination.

7 regular monitoring

before each infusion you undergo blood tests and a clinical assessment. imaging scans are performed at predefined intervals to evaluate tumor response.

8 response assessment

study investigators compare the imaging results using standardized criteria to determine whether the disease is stable, shrinking, or progressing.

9 continuation or discontinuation

treatment continues until disease progression, unacceptable toxicity, or completion of the planned number of cycles as defined by the protocol.

10 follow‑up

after treatment stops you are followed for a period to monitor long‑term outcomes such as progression free survival and overall survival.

Who Can Join the Study?

You must be able to understand why the study is being done and sign a written informed consent form before any study procedures begin.
If you are a woman who could become pregnant and are sexually active with a man who is not sterilized, you need a negative pregnancy test within 14 days before starting treatment and you must use a highly effective form of birth control from the screening visit 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 or use an acceptable form of contraception from the screening visit until 4 months after the last dose; you also cannot donate or bank sperm during this period.
You must be reachable for treatment visits and follow‑up appointments.
You must be at least 18 years old at the time you sign the consent form.
For the dose‑escalation part of the study, you must have a diagnosis of metastatic soft tissue sarcoma confirmed by tissue testing, have had no more than three previous lines of cancer treatment, and must not have received the chemotherapy drug doxorubicin before (although it could be appropriate for your disease).
For the dose‑expansion and phase II parts of the study, you must have metastatic soft tissue sarcoma of one of the following subtypes: undifferentiated pleomorphic sarcoma (UPS), myxofibrosarcoma (MFS), dedifferentiated liposarcoma (DDLPS), myxoid liposarcoma (MLPS), or leiomyosarcoma (LMS), and you must not have received any treatment for advanced disease before joining the study.
Your cancer must include at least one tumor that can be measured on imaging scans, as defined by the RECIST v1.1 criteria (meaning the size of the tumor can be reliably tracked over time).
You need adequate blood‑forming (bone marrow), liver, and kidney function, which is shown by blood tests meeting these minimum levels: white blood cells (neutrophils) ≥ 1,000 per mm³, platelets ≥ 100 × 10⁹/L, hemoglobin ≥ 9.0 g/dL; albumin ≥ 2.5 g/dL, bilirubin ≤ 1.5 × the normal upper limit (up to 3 × if you have Gilbert’s syndrome), alkaline phosphatase ≤ 2.5 × normal, AST and ALT ≤ 2.5 × normal (or 5 × if you have liver metastases), and clotting tests (PT/INR or PTT) < 1.5 × normal (≤ 2.0 × if you take blood thinners); kidney function must show creatinine ≤ 1.5 × normal or a calculated clearance ≥ 40 mL/min.
Any side effects from previous cancer treatments must have resolved to a mild level (grade 1 or less) except for hair loss or other effects that are not considered a safety risk.
You must be willing to give blood samples for drug‑level testing (required only in phase Ib) and to provide a recent tissue sample of your tumor (either an archived sample taken within the past 24 months or a new biopsy taken before treatment starts) for research purposes.
Your overall health and ability to perform daily activities must be rated as ECOG performance status 0 or 1, meaning you are fully active or able to carry out light work but are up and about most of the time.
You must have a life expectancy of at least 12 weeks at the time of screening.

Who Cannot Join the Study?

Participation in another clinical trial (interventional or observational) until the safety visit of this study.
Having had major surgery or a serious injury within 14 days before the first dose, or expecting to need major surgery while on study treatment.
Need for systemic corticosteroids (at least 10 mg per day of prednisone or similar) or other immune‑suppressing drugs. (Topical, nasal, inhaled or eye steroids are allowed.)
Having active heart disease or a history of heart problems, including: recent blocked heart arteries, heart attacks, or worsening heart failure within the past six months; inflammation of the heart lining (pericarditis); a left‑ventricle pumping ability (ejection fraction) below 50%; serious irregular heartbeats (arrhythmias) that cause symptoms or need treatment; a prolonged QT interval on an ECG greater than 470 ms, or a family history of long QT syndrome.
Having chronic ulcers or serious liver disease that scores Child‑Pugh C (the most severe level).
Being pregnant, breastfeeding, or not willing to use highly effective birth control as required.
Having any serious medical condition or abnormal lab test that the doctor feels makes study participation unsafe.
Current infection with hepatitis B virus (HBV) or hepatitis C virus (HCV) (unless the infection is resolved as defined by specific tests).
Having an active primary immunodeficiency, or untreated HIV infection with a detectable viral load (treated HIV with undetectable viral load is allowed if certain drugs are avoided).
Having any other uncontrolled infection at the time of enrollment.
Receiving a live or weakened (attenuated) vaccine within 30 days before the first dose.
Having received any approved or investigational cancer therapy within 14 days before starting the study drug.
Having a history of uncontrolled seizures, central nervous system (CNS) disorders, or serious psychiatric illness that could affect safety or compliance.
Known substance abuse or any other severe, uncontrolled medical condition that the doctor thinks would make participation unsafe.
Being unable or unwilling to follow the study requirements.
Prior treatment with anthracycline chemotherapy (for example, doxorubicin) for localized or advanced disease.
Prior treatment with immune‑checkpoint inhibitors for localized or advanced disease.
For the dose‑expansion and phase II parts, having received any treatment for advanced disease before.
Having active, uncontrolled or symptomatic brain metastases (cancer spread to the brain) or leptomeningeal disease (cancer in the membranes covering the brain and spinal cord). Treated, stable brain metastases may be allowed under strict conditions.
Having bone sarcoma, locally aggressive sarcoma, gastrointestinal stromal tumor (GIST), or Kaposi sarcoma.
Having another cancer (or a cancer diagnosed within the past five years) except for certain low‑risk skin cancers (carcinoma in situ of the cervix, basal cell carcinoma, squamous cell carcinoma of the skin) that have been cured.
Known allergy or severe reaction to any study drug or its ingredients.

Where you can join this trial?

Verified and Recommended Sites

No sites found in this category

Verified Sites

Site Name	City	Country	Status
Hospital Clinico San Carlos	Madrid	Spain

Other Sites

Site Name	City	Country
Virgen del Rocío University Hospital	Sevilla	Spain
Hospital General Universitario De Valencia	Valencia	Spain
Hospital Universitario De Canarias	La Laguna	Spain
Hospital General Universitario Gregorio Maranon	Madrid	Spain
Hospital Universitario 12 De Octubre	Madrid	Spain
Hospital Universitario Virgen De La Victoria	Malaga	Spain
Hhnmwrug Vavp devpxohg	Barcelona	Spain
Hfxixoit Dy Lm Sbegv Ccte I Svcb Pyq	Barcelona	Spain
Ixgugdlg Ctmoow Ditkutthxfgwhfiyu	L'hospitalet De Llobregat	Spain
Frymyxtti Pluo Lu Ivmqehsgmbcmp Baegzicmm Dqa Hsnzrbnq Uizrujcaureye Lc Psz	Madrid	Spain

Trial status

Country	Status	Recruitment Start
Spain	Not yet recruiting	01.07.2026

Trial locations

Investigated drugs:

Bexmarilimab is an investigational medicine that belongs to a class of drugs called monoclonal antibodies. It is given through an IV infusion. In this study, researchers are testing it to see how safe it is and how well it works when combined with chemotherapy in people whose soft‑tissue sarcoma has spread. The trial will find the highest dose that can be tolerated and the dose to use in later studies.

Doxorubicin is a well‑known chemotherapy drug that is also given by IV infusion. It is part of standard treatment for many cancers, including soft‑tissue sarcoma. In this trial, doxorubicin is used together with bexmarilimab to see if the combination works better than doxorubicin alone, and it also serves as the comparison treatment for measuring any added benefit.

Soft tissue sarcoma (advanced/metastatic) – Soft tissue sarcoma is a cancer that starts in the connective tissues such as muscle, fat, nerves, or blood vessels. In the advanced or metastatic stage the tumor has spread from its original location to other parts of the body, often the lungs, liver, or bones. The disease progresses as new tumor nodules appear and existing ones enlarge, sometimes causing pain or swelling. Growth can be variable, with some tumors expanding quickly while others grow more slowly. The spread of cancer cells to distant sites marks the transition from localized to metastatic disease.

Undifferentiated pleomorphic sarcoma (UPS) – UPS is a type of soft tissue sarcoma that lacks a specific line of cell differentiation and appears as a pleomorphic (irregular) tumor. It typically arises in the deep soft tissues of the limbs or trunk and can enlarge over time. As it progresses, the tumor may invade surrounding structures and eventually spread to distant organs. The disease often presents as a painless lump that becomes noticeable as it grows. Metastatic spread follows similar patterns to other soft tissue sarcomas, commonly affecting the lungs.

Myxofibrosarcoma (MFS) – Myxofibrosarcoma is a soft tissue sarcoma characterized by a gelatinous (myxoid) matrix and spindle-shaped cells. It usually develops in the extremities of older adults and can form multiple nodules. The tumor gradually enlarges and may infiltrate nearby tissues, making complete removal difficult. Over time, it can spread to regional lymph nodes and distant sites such as the lungs. Recurrence and metastatic spread are common features of its progression.

Dedifferentiated liposarcoma (DDLPS) – DDLPS originates from fat cells that have transformed into a more aggressive, less differentiated form. It often occurs in the retroperitoneum or deep soft tissues of the limbs. The tumor can grow large without symptoms, then invade surrounding organs as it advances. As the disease progresses, parts of the tumor may become more aggressive and spread to distant locations, especially the lungs. The combination of a well‑differentiated component and a high‑grade component drives its worsening behavior.

Myxoid liposarcoma (MLPS) – Myxoid liposarcoma is a soft tissue cancer that contains a characteristic myxoid (mucoid) background and fat‑like cells. It commonly arises in the thigh or other large muscles and can expand slowly at first. Over time, the tumor may become larger, cause discomfort, and infiltrate nearby structures. Advanced disease is marked by spread to the lungs, bone, or other soft tissues. The myxoid matrix can facilitate tumor cells moving through the bloodstream, leading to metastasis.

Leiomyosarcoma (LMS) – Leiomyosarcoma is a malignant tumor arising from smooth muscle cells, often found in the uterus, abdomen, or blood vessel walls. It typically presents as a deep, firm mass that gradually increases in size. As it progresses, the cancer can invade surrounding tissues and spread through the bloodstream to distant organs, especially the lungs and liver. The disease may remain localized for a period before becoming metastatic. Growth and spread are driven by the tumor’s ability to penetrate blood vessels and establish new growth sites.

Trial ID:

2025-525144-18-00

Protocol code:

MEDOPP0799

NCT ID:

NCT07460986

Trial Phase:

Human Pharmacology (Phase I) – Other

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

What is this study about?

Who Can Join the Study?

Who Cannot Join the Study?