RESUMO
Studies of the humoral effects of the Prosorba column were conducted in conjunction with the Phase 3 trial of Prosorba versus sham therapy for rheumatoid arthritis (RA). When perfused with normal human plasma in vitro, Prosorba bound predominantly IgG with a maximal capacity of approximately 462 g of Ig per Prosorba column, equal to about 1.5% of circulating IgG. Prosorba treatment did not alter the concentrations of albumin, IgG, IgM, and IgA in 3 RA patients, except for a small dilutional effect. Kinetic studies demonstrated that Prosorba removed IgG > IgM, IgA, and IgM rheumatoid factor (RF) during the initial moments of apheresis and almost exclusively IgM RF after 15 min. No net protein removal occurred at > or = 60 min. Mean values of circulating immune complexes (CICs) were not significantly decreased by 12 weekly treatments. Complement was activated by the apheresis system upstream of the Prosorba column without changing C3 or C4 levels. We conclude that the Prosorba mechanism of action in RA is not bulk removal of Ig, but might involve modification of the CIC repertoire and could include, but not be limited to, effects related to complement activation.
