Rituximab's Efficacy May Be Correlated with CD4 T Cell Counts Save

Rituximab (RTX) is highly effective at B cell depletion and this may be one of several hypothetical ways in which the drug works.  B cell numbers (measured as CD19+ B cells) plummet rapidly after the first infusion and stay down for 6-12 months.

Lavielle and colleagues from France, examined both CD19 and CD4 cell counts in their cohort (n=54) of rheumatoid arthritis (RA) patients who were treated with RTX between 2007-2014. CD4 and C19 cell subsets were assessed by flow cytometry.  Prior to each cycle (2 infusions) CD4+ T-cells were within the normal range. They noted that CD19 numbers went down and stayed down as expected. However, CD4+ T-cell depletion occurred with each cycles of RTX treatment, and the magnitude and duration was more variable in their RA patients.

Their analyses showed that RTX clinical responses were chronologically associated with CD4+ depletion. While B-cell numbers remained low, post-RTX CD4+ counts dropped for a temporary period and was followed by an almost complete recovery. CD4 T cell counts below 300/mm3 was seen in 8 of 54 patients. If the decrease in CD4+ T cells was greater than 3%, more responders were observed. Conversely, non-responders noted smaller decreases CD4+ T cells.

CD4+ T cell reduction induced by RTX are closely linked to changes in disease activity (moreso than B-cell depletion). Monitoring circulating CD4+ T-cells might be helpful to clinicians assessing disease activity while on RTX.