A Proof-of-Concept Study of Rituximab for the Treatment of Autoantibody-Mediated Fibromyalgia
- Trial ID
- 2025-523465-21-00
- Sponsor
- Region Stockholm – SLSO
Trial statistics
Diseases & Conditions
Objectives
The primary objective of this study is to evaluate the efficacy of rituximab in reducing average daily pain, as measured by the visual analogue scale, at week 16 following administration in patients with fibromyalgia. The secondary objectives include:
- Assessment of improvements in clinical symptoms and patient perception of the disease.
- Evaluation of changes in the concentration of anti-fibromyalgia antibodies.
Participants
The sponsor did not provide information regarding the total number of participants. The study population consists of male and female patients aged 18 to 65 years diagnosed with fibromyalgia. Eligible individuals must meet specific diagnostic criteria established by a pain specialist or rheumatologist and demonstrate positive results for fibromyalgia-associated antibodies. Inclusion requires a disease duration of no more than 2 years since diagnosis and no more than 5 years since symptom onset. Participants must present with a visual analogue scale pain score of 50 mm or greater. Furthermore, individuals must have maintained stable pain medication dosages for 6 weeks prior to screening and possess measurable anti-COVID-19 antibodies or have received at least three vaccine doses. Women of childbearing potential are required to utilize effective contraception and provide a negative pregnancy test.
Plans and Procedures
This clinical trial is designed to investigate the efficacy of rituximab administered via intravenous infusion for the treatment of fibromyalgia. The primary objective is to evaluate the mean reduction in pain as measured by the visual analogue scale 16 weeks after treatment. Secondary outcomes include improvements in symptoms assessed via the Fibromyalgia Impact Questionnaire and the Patient Global Impression of Change, alongside an objective reduction in satellite glia cell binding human IgG. The study methodology involves a proof of concept approach. Participants must meet specific inclusion criteria, including a diagnosis of fibromyalgia by a specialist, a disease duration of no more than 2 years since diagnosis, and the presence of autoantibodies associated with the condition. Stable pain management for 6 weeks prior to screening is required. The total duration of participant involvement extends through a 16-week assessment period following the administration of the test product. Participants may be required to use contraceptive methods for one year following the conclusion of the study. Early termination may occur if protocol compliance or safety requirements are not maintained.
Treatment
Rituximab is the investigational medicinal product administered via intravenous infusion at a dosage of 1000 mg.
Background therapy includes the following auxiliary medications:
- Paracetamol administered as 500 mg film-coated tablets via the oral route.
- Methylprednisolone administered as 16 mg tablets via the oral route.
- Cetirizine dihydrochloride administered as 10 mg film-coated tablets via the oral route.
Efficacy
The primary efficacy endpoint is the mean reduction in pain as measured by the Visual Analogue Scale (VAS) at week 16 following treatment with rituximab. Secondary efficacy parameters evaluated at week 16 include improvements in patient-perceived fibromyalgia symptoms using the Fibromyalgia Impact Questionnaire (FIQ) and the Patient Global Impression of Change (PGIC). Additionally, the study will assess the objective reduction in the percentage of satellite glia cell binding human IgG, which is identified as a mediator of pain.
Inclusion and Exclusion Criteria
Inclusion Criteria
- The study participant must have provided written informed consent.
- Age 18–65 years
- Patients with a diagnosis of fibromyalgia (FM) who meet the diagnostic criteria for FM and have been diagnosed by a treating pain specialist or rheumatologist trained in the use of these criteria (AAPT core diagnostic criteria 1990 and revised criteria from 2016).
- FM disease duration since diagnosis no more than 2 years, and since symptom onset no more than 5 years.
- FM disease burden with VAS pain ≥ 50 mm (0-100mm)
- The patient has tested positive for FM-associated antibodies (Camilla Svensson’s laboratory, Biomedicum, Karolinska Institutet) (2,3), according to current reference intervals.
- Pain treatment must have been stable without any change in medication or dosage during the 6 weeks prior to screening. For permitted substances, please see section 7.9.
- Women of childbearing potential must have a negative pregnancy test and use effective contraceptive methods throughout the entire study participation period, from baseline and for one year thereafter.
- The study participants must be able and willing to comply with all study procedures.
- The study participants must have been vaccinated with at least three doses of a COVID-19 vaccine or have measurable titers of anti-COVID-19 antibodies.
Exclusion Criteria
- Diagnosis of another autoimmune disease, exclusive stable, substituted hypothyreosis.
- Ongoing or recently discontinued (within the last 6 months) immunosuppressive treatment.
- Known immunodeficiency.
- Neuropsychiatric diagnosis.
- Use of opioids or benzodiazepine
- Active malignancy within the past 5 years.
- Ongoing or planned pregnancy or breastfeeding.
- Severe infection within the past 3 months.
- Any ongoing acute or chronic systemic infection, including HIV, latent tuberculosis, hepatitis B or C, or any other infection considered clinically significant by the study physician and not treated with appropriate antimicrobial therapy.
- Severe heart failure (New York Heart Association Class IV) or severe uncontrolled heart disease.
- Hypersensitivity to the active substance, murine proteins, or any other substance in the investigational medicinal product
- Participation in any other clinical trial of an investigational drug, or exposure to any investigational product or procedure within 6 months prior to screening.
- Any medical condition that, in the judgment of the study physician, may interfere with the patient’s participation in the study, pose additional risk to the patient, or complicate the assessment of the patient.
- BMI > 35.
- Vaccination less than 4 weeks prior to inclusion.
- Previous use of rituximab for any indication.
- Any other disease, medical condition, or planned procedure that, in the opinion of the study physician, constitutes a contraindication for participation.
Trial Status by Country
| Country | Status | Start of Recruitment | Planned Patients |
|---|---|---|---|
 Sweden | Not Yet Recruiting | 01 Feb 2026 | 15 |
Sites & Investigators
Investigational Products
Details about the medicinal products being studied in this clinical trial.
| Product Name | Role in Trial | Formulation | Administration | Max Daily Dose | Treatment Duration | EU MP Number |
|---|---|---|---|---|---|---|
Paracetamol ABECE 500 mg filmdragerade tabletter | Other | FILMDRAGERADE TABLETTER | ORAL | 4 | 1 | PRD11758240 |
Medrol 16 mg tabletter | Other | TABLETTER | ORAL | 24 | 1 | PRD11825208 |
Cetirizin ABECE 10 mg filmdragerade tabletter | Other | FILMDRAGERADE TABLETTER | ORAL | 10 | 1 | PRD4780221 |
RITUXIMAB | Test | PHF00230MIG | INTRAVENIOUS INFUSION | 1000 | 1 | SCP24437857 |