Most patients with resistant rheumatoid arthritis who failed to respond to an initial cycle of rituximab (Rituxan) showed clinical improvement following a second treatment cycle, a British study found.
Six months after cycle 2, significant improvements were seen on disease activity scores compared with scores either at baseline or immediately before retreatment (P<0.001 for both), according to Edward M. Vital, MBChB, of the University of Leeds, and colleagues.
In addition, almost three-quarters of patients had moderate or good responses, according to the criteria of the European League Against Rheumatism (EULAR), the researchers reported in the May issue of Arthritis & Rheumatism.
Rituximab is a chimeric monoclonal antibody against the CD20 protein, which is found primarily on the surface of B cells.
In rheumatoid arthritis, this B-cell depleting agent is generally reserved for patients who do not respond to conventional disease-modifying medications such as methotrexate or to antitumor necrosis factor (TNF) drugs.
"Consequently, patients who do not exhibit an adequate response to rituximab have frequently exhausted all other available therapy options, and treatment of these patients is challenging," Vital and colleagues explained.
Initial studies of rituximab suggested that the drug completely depleted B cells, and that a lack of response might reflect B-cell–independent mechanisms in some patients.
However, the development of more sensitive methods of measuring circulating B cells has demonstrated otherwise.
Highly sensitive flow cytometry has shown that almost all patients who do not show a clinical response have incomplete B-cell depletion, especially in the synovium.
To see if an additional cycle of treatment could enhance depletion and lead to clinical response, the investigators treated 25 nonresponders with two infusions (each 1 gram) of rituximab, at least six months after the first pair of infusions but before B-cell repopulation had occurred.
To be classified as a EULAR responder (either moderate or good), patients must have a significant change in their disease activity scores and low current disease activity.
http://www.medpagetoday.com/Rheumatology/Arthritis/20049This is somewhat interesting. I wonder if these people were taken off the medicine and put on something else inbetween time? If so then it could even be that a combination therapy takes place that helps? Just wondering?