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Study of rituximab for reducing pain in patients with fibromyalgia caused by autoantibodies

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What is this study about?

This study is looking at fibromyalgia, a condition that causes widespread pain throughout the body along with other symptoms like tiredness and sleep problems. The study will test whether a medicine called rituximab can help reduce pain in people who have fibromyalgia. Rituximab is a medicine that affects the immune system, which is the body’s defense system. In this study, participants will also receive other medicines to help manage symptoms during the study, including paracetamol for pain relief, methylprednisolone which is a medicine that reduces inflammation, and cetirizine dihydrochloride which is commonly used for allergies. The purpose of this study is to find out if rituximab treatment can reduce the average daily pain that people with fibromyalgia experience.

Participants in this study must have been diagnosed with fibromyalgia within the past two years and must have significant pain levels. They must also have specific antibodies in their blood that are associated with fibromyalgia. These antibodies are proteins made by the immune system that may be causing some of the pain symptoms. The study will measure how much pain decreases sixteen weeks after participants receive the rituximab treatment. Rituximab will be given through a tube inserted into a vein, which is called an infusion. The treatment period will last for one day, and participants will be followed for sixteen weeks after receiving the medicine.

During the study, researchers will measure pain levels using a scale where participants mark how much pain they feel. They will also use questionnaires to understand how fibromyalgia affects daily life and whether participants feel their condition has improved. The study will also look at changes in the antibodies in the blood to see if there is a connection between these antibodies and pain levels. The entire study is expected to run from early 2026 to early 2027.

1 Initial treatment preparation

Your pain treatment must remain stable without any changes in medication or dosage for 6 weeks before starting the trial.

If you are a woman of childbearing potential, you will need to have a negative pregnancy test before beginning the trial.

You will need to use effective contraceptive methods from the start of the trial and for one year after receiving the treatment.

2 Baseline assessment

At the beginning of the trial, your current pain level will be measured using a visual analog scale, which is a tool where you mark your pain intensity on a line from 0 to 100 millimeters.

You will complete questionnaires to assess your fibromyalgia symptoms, including the Fibromyalgia Impact Questionnaire, which measures how fibromyalgia affects your daily life.

3 Pre-medication before rituximab infusion

Before receiving the main treatment, you will be given medications to help prevent potential side effects.

You will take paracetamol 500 mg tablets by mouth. Paracetamol is a common pain reliever and fever reducer.

You will take methylprednisolone 16 mg tablets by mouth. Methylprednisolone is a medication that reduces inflammation and helps prevent allergic reactions.

You will take cetirizine 10 mg tablets by mouth. Cetirizine is an antihistamine that helps prevent allergic reactions.

4 Rituximab infusion treatment

You will receive rituximab through an intravenous infusion, which means the medication will be given directly into your vein over a period of time.

Rituximab is a medication that targets certain cells in your immune system called B cells, which may be involved in causing fibromyalgia pain.

5 Follow-up period and monitoring

After receiving rituximab, you will be monitored for 16 weeks.

During this period, your pain levels will be regularly assessed using the visual analog scale to measure any changes in your daily pain.

You will continue to complete questionnaires about your fibromyalgia symptoms and how you perceive any changes in your condition using the Patient Global Impression of Change questionnaire.

Blood samples may be taken to measure specific antibodies related to fibromyalgia.

6 Primary assessment at week 16

At week 16 after receiving rituximab, your average daily pain will be measured to determine if there has been a reduction compared to your baseline pain level.

Your overall fibromyalgia symptoms and any improvements will be assessed through the questionnaires you have been completing.

7 Extended follow-up period

You will continue to be followed after the 16-week assessment period.

If you are a woman of childbearing potential, you must continue using effective contraceptive methods until one year after receiving the rituximab treatment.

Who Can Join the Study?

  • You must provide written informed consent, which means you agree in writing to take part in the study after understanding what it involves.
  • You must have received at least three doses of a COVID-19 vaccine, or have measurable levels of anti-COVID-19 antibodies in your blood, which are proteins your body makes to fight the COVID-19 virus.
  • You must be between 18 and 65 years old.
  • You must have a diagnosis of fibromyalgia confirmed by a pain specialist or rheumatologist who is trained to diagnose this condition using specific medical criteria.
  • Your fibromyalgia must have been diagnosed no more than 2 years ago, and your symptoms must have started no more than 5 years ago.
  • Your pain level must be at least 50 millimeters on a scale of 0 to 100 when measured with a VAS, which is a visual scale used to rate pain intensity.
  • You must have tested positive for fibromyalgia-associated antibodies in a laboratory test, which are specific proteins in your blood linked to fibromyalgia.
  • Your pain treatment must have been stable for at least 6 weeks before screening, meaning you have not changed your pain medications or their doses during this time.
  • If you are a woman who can become pregnant, you must have a negative pregnancy test and use effective birth control methods throughout the study and for one year after.
  • You must be able and willing to follow all study procedures and requirements.

Who Cannot Join the Study?

  • The source data does not provide specific exclusion criteria for this clinical trial
  • This means there is no available information about which patients cannot participate in the study
  • Exclusion criteria are conditions or factors that would prevent someone from joining a clinical trial, but these details have not been included in the provided information

Where you can join this trial?

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Other Sites

Site Name City Country Status
Region Stockholm – SLSO Stockholm Sweden
Lund University Hospital Lund Sweden
Sufrpw Ufugnfdcadachkriyns Mhzll Malmo Sweden

Want to learn more about this study or check if you can participate? Contact us.

Trial status

Country Status Recruitment Start
Sweden Sweden
Not yet recruiting
01.02.2026

Trial locations

Investigated drugs:

Rituximab is a medication that works by targeting certain cells in the immune system. It is being tested in this trial to see if it can help reduce daily pain in people with fibromyalgia that may be caused by autoantibodies. The medication is given as a treatment to help control the immune system’s response in the body.

Investigated diseases:

Fibromyalgia – Fibromyalgia is a long-term condition characterized by widespread pain throughout the body. People with this condition experience persistent muscle and joint pain that can affect multiple areas at the same time. The pain is often accompanied by fatigue, sleep problems, and difficulty concentrating. The condition tends to be chronic, meaning it lasts for extended periods and may have periods where symptoms worsen or improve. People with fibromyalgia may also experience increased sensitivity to touch and pressure on their muscles. The condition affects how the brain and nervous system process pain signals, making normal sensations feel more painful than they would to others.

Trial ID:
2025-523465-21-00
Trial Phase:
Therapeutic confirmatory (Phase III)

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