Complete depletion of B lymphocyte subcells after rituximab therapy was not a good predictor of success in patients with rheumatoid arthritis compared with those who had a lower frequency of plasmablasts, according to study results.
Researchers evaluated 52 patients with active rheumatoid arthritis (RA) who were administered 100 mg prednisolone followed by two 1,000-mg infusions of rituximab. Disease Activity Score 28 values were determined at baseline and at 2 and 24 weeks after therapy for European League Against Rheumatism (EULAR) response. Researchers also used high-sensitivity flow cytometry to measure B cell subsets at baseline and 2 weeks. B cell depletion was met when CD19 values were less than 0.0001 x 109 cells/liter.
Patients had the following EULAR response at 6 months: 19 were rated good, 23 were moderate and 10 had no response to therapy. Researchers also discovered that B lymphocyte depletion in peripheral blood did not predict successful rituximab therapy, and EULAR responders and nonresponders had incomplete depletion at approximately the same frequency.
Compared with healthy age-matched controls, nonresponders had elevated baseline CD95 positive pre-switch memory B cells (52.6% [37.9%-62.6%] vs. 37.9% [26.5%-49.3%], P≤0.23), while responders had fewer plasmablasts (0.6% [0.3%-1.3%] vs. 1.3% [0.5%-2.8%], P≤.03). Using univariate logistic regression, researchers determined that only a low frequency of plasmablasts accurately predicted EULAR responsiveness (OR=2.22; 95% CI, 1.04-4.74).
“The baseline enumeration of B lymphocyte subsets is still of limited clinical value for the prediction of response to anti-CD20 therapy,” the researchers said. “Even in this small cohort, the frequency of plasmablast seems to be the best predictor for response to a B cell-depleting therapy. Still, prospective studies have to confirm this finding.”