LONDON (FRONTLINE MEDICAL NEWS) – A single, intravenous infusion of 1,000 mg of rituximab to people with arthralgia and a high risk for developing rheumatoid arthritis cut the subsequent rate of rheumatoid arthritis development roughly in half during more than 18 months of follow-up in a proof-of-concept, placebo-controlled study that randomized 81 people.

“This is the first study to evaluate the effects of a biopharmaceutical in subjects at risk of developing RA [rheumatoid arthritis],” Dr. Daniëlle M. Gerlag said at the European Congress of Rheumatology. “These results strongly support the rationale for future clinical trials aimed at prevention of RA by a targeted intervention,” added Dr. Gerlag, a rheumatologist at the Academic Medical Center in Amsterdam.

Additional studies are needed to confirm this effect and to examine whether the period of protection against RA development can be extended by administration of additional rituximab (Rituxan) doses. In the current study, the protective effect from the single dose administered appeared to wane over time, she noted.

The idea behind this strategy is that a window of opportunity exists in people at high risk for developing RA to prevent the disease by blocking production of the autoantibodies that trigger the development of a subclinical synovitis that eventually leads to RA. Rituximab is a cytolytic antibody directed against the CD20 antigen on B cells that already has regulatory approval for treating moderately to severely active RA as well as certain other diseases.

Dr. Gerlag and her associates recently published an analysis that detailed their rationale for hypothesizing that prophylactic treatment with rituximab might prove effective at delaying or preventing the development of RA in susceptible people ( Rheumatology [Oxford]. 2016 April;55[4]:607-14 ).

The Prevention of RA by Rituximab ( PRAIRI ) study ran at three Dutch centers. The investigators enrolled people with arthralgia who had never been diagnosed with arthritis, had never used a disease-modifying antirheumatic drug, and had at least one of these two risk factors: a serum level of IgM rheumatoid factor of more than 12.5 IU/mL and a serum level of anticitrullinated peptide antibodies of more than 25 IU/mL. Enrolled participants also needed to have at least one of the following: a serum level of C-reactive protein greater than 3 mg/L, an erythrocyte sedimentation rate of greater than 28 mm/hr, and evidence of subclinical synovitis identified by either ultrasound or MRI.

The researchers found these participants largely through screening sessions run at health fairs and by publicizing the study during television appearances, Dr. Gerlag said. About three-quarters of the participants were first-degree relatives of patients already diagnosed with RA, but this was not a criterion for enrollment. The participants averaged about 53 years old, and nearly two-thirds were women.

Among the 81 people who underwent treatment, 41 received a single, 1,000-mg infusion of rituximab, and 40 received a placebo infusion. The researchers then followed the participants with scheduled, periodic examinations during a median of 29 months.

During follow-up, 16 of the 40 people in the placebo group (40%) developed RA after a median of 12 months, and 14 of the 41 in the treated arm (34%) developed RA after a median of 17 months.

The researchers performed two different statistical analyses on these outcomes. They used a Kaplan-Meier survival analysis to determine the time until 25% of people in each arm developed RA. Among the placebo patients, this occurred after 12 months, while in the intervention arm, it did not occur until 24 months, a statistically significant doubling of the time to this outcome with rituximab treatment, Dr. Gerlag reported .

The second analysis calculated a Cox proportional hazard ratio based on the time to development of rheumatoid arthritis among those in each of the treatment groups. This determined a 55% reduced hazard ratio after 12 months among people treated with rituximab, compared with the placebo-treated controls, and a 53% reduced hazard after 18 months, both statistically significant differences.

A safety analysis showed that some people treated with rituximab had mild infusion-related symptoms, but no participants had serious infections. Serious adverse events occurred in 11 people in the rituximab group and in 3 in the placebo arm, but none of these serious adverse events was judged to be related to treatment by the study’s data safety monitoring board, said Dr. Gerlag, who is also on the staff of GlaxoSmithKline in Cambridge, England.

The PRAIRI study received no commercial funding. Dr. Gerlag is also a shareholder in GlaxoSmithKline, but the company played no role in the study.

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