Rituximab joint protective benefits capped

By Lynda Williams, Senior medwireNews Reporter

Study findings may help guide rituximab dosing regimens for patients with rheumatoid arthritis.

As reported in Rheumatology, the researchers found that the likelihood for radiographic evidence of progressive RA structural damage to the hands and feet at 1 year was not significantly predicted by serum rituximab levels after 4, 12, or 16 weeks of treatment.

Nor was there a significant correlation between rituximab serum level at these time points and the change in Sharp-van der Heijde (SHS) score for joint space narrowing and erosion, nor a reduced risk for progression with further treatment after 6 months.

"The data show that low rituximab levels are not related to progression of structural damage, suggesting that treatment with higher dosages than 2 × 1000 mg rituximab is unlikely to be more effective in protecting against progressive joint destruction," say Paul Tak (Academic Medical Center, Amsterdam, the Netherlands) and co-workers.

The study included 62 patients with active RA who were attending one of three hospitals. All patients were given rituximab 1000 mg infusions on days 1 and 15 with retreatment after 6 months depending on hospital protocol. Serum rituximab levels were measured at regular intervals over treatment.

Joint progression was defined as a SHS score increase of at least 1, 3, or 5 points; 60%, 53%, and 37% of patients met these criteria, respectively.

Using a SHS increase of 3 points or more to define progression, analysis showed no significant difference in rituximab levels between 29 patients with and 27 patients without progression at week 4 (12 vs 128 µg/mL) or week 12 (6 vs 8 µg/mL).

"Taken together, our data do not support the use of dosages higher than 2 × 1000 mg rituximab in order to more effectively inhibit progression of joint destruction," the researchers conclude.

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