Predicting response to low-dose rituximab for rheumatoid arthritis

Prospective Validation of a Pharmacological Biomarker for Low-Dose Rituximab in Rheumatoid Arthritis

We will test whether a blood-based pharmacological model can predict which adults with rheumatoid arthritis will respond to a lower rituximab dose (1000 mg once per cycle).

Quick facts

• Study type: Observational
• Enrollment: 30 (estimated)
• Ages: 18 Years and up
• Sex: All
• Sponsor: University Hospital, Tours (other)
• Drugs / interventions: rituximab, Methotrexate
• Locations: 1 site (Tours)
• Trial ID: NCT06933134 on ClinicalTrials.gov

What this trial studies

This is a prospective observational validation of a PK-PD based prediction model applied to patients receiving low-dose rituximab (1000 mg once per cycle). The model uses clinical and laboratory inputs including body surface area, serum IgG, residual rituximab concentration, and CD4+ T-cell count to predict clinical response. The primary outcome is the correlation and coefficient of determination between observed DAS28-CRP six months after a second low-dose cycle and the DAS28 predicted by the model. Participants are adults with rheumatoid arthritis who are switching from standard-dose rituximab to the low-dose regimen as part of routine care.

Who should consider this trial

Good fit: Adults (≥18) with RA meeting ACR/EULAR 2010 criteria who have had a good clinical response on standard-dose rituximab and are candidates to switch to the 1000 mg once per cycle regimen, with stable csDMARD and low-dose corticosteroid use when applicable.

Not a fit: Patients on other targeted DMARDs, with associated inflammatory rheumatisms (like Sjögren's), fibromyalgia, active hematologic lymphoid disease, or who oppose data processing are not expected to benefit from this predictive approach.

Why it matters

Potential benefit: If successful, the model could help clinicians personalize rituximab dosing so some patients safely receive lower doses, reducing infection risk and treatment costs.

How similar studies have performed: Previous clinical work has shown 1000 mg once per cycle can be non-inferior for maintenance and earlier PK-PD modeling at standard doses produced reliable predictions, but prospective validation of this model for the low-dose regimen is novel.

Eligibility criteria

Inclusion Criteria:

. Age ≥ 18 years

* Diagnosis of rheumatoid arthritis meeting ACR/EULAR 2010 criteria.
* Candidates for a Low Dose regimen: on standard dose rituximab and with a good clinical response according to the referring rheumatologist. No maximum duration of use of standard-dose rituximab has been defined.
* In the case of co-prescription of csDMARDs (Methotrexate, Leflunomide, Salazopyrine, Plaquenil), the dose must have been stable for 3 months.
* If corticosteroids are co-prescribed, the dose should be ≤ 10 mg/d and stable for 3 months.

Exclusion Criteria:

* Other associated targeted disease-modifying therapy
* Sjögren's syndrome or other associated inflammatory rheumatism
* Fibromyalgia or other pathology having an impact on the assessment of disease activity
* Any active haematological disease affecting lymphocytes (chronic lymphocytic leukaemia, Hodgkin's and non-Hodgkin's lymphomas, lymphoplasmacytic lymphoma, T lymphoma).
* Opposition to data processing
* No inclusion of persons covered by articles L. 1121-5 to L. 1121-8 and L. 1122-1-2 of the Public Health Code (e.g. minors, protected adults, etc.).

Where this trial is running

Tours

• University hospital — Tours, France (RECRUITING)

Study contacts

• Study coordinator: Simon BRUNET

Conditions: Rheumatoid Arthritis, pharmacological biomarker, rituximab, retreatment, low dose