Absolute Lymphocyte Count Assesses Infection Risk in Tofacitinib-Treated RA

The researchers analyzed the relationship of absolute lymphocyte counts and lymphocyte subset counts in the RA population.

In patients with rheumatoid arthritis (RA) being treated with tofacitinib, absolute lymphocyte count (ALC) monitoring can adequately assess infection risk, according to a study published in Arthritis & Rheumatology.

The study included data on ALC from participants in phase 3 (12 to 24 months) and phase 1, 2, and 3 long-term extension studies of tofacitinib. Researchers included data on lymphocyte subset counts (LSCs) from phase 2 studies (1.5 to 6 months), an ORAL Sequel vaccine substudy (22 months), and an ORAL Sequel lymphocyte substudy (50 months) of tofacitinib.

The researchers evaluated the reversibility of ALC/LSC changes and analyzed the relationship of ALC and LSC in the RA population.

The results indicated that participants treated with tofacitinib had an initial increase in ALC at 1 month compared with baseline. At 12 months, participants showed median decreases in ALC from baseline of -190 cells/mm3 with twice-daily tofacitinib 5 mg plus methotrexate, and -310 cells/mm3 with twice-daily tofacitinib 10 mg plus methotrexate.

Gradually, the ALCs declined to a steady state of -400 cells/mm3 after approximately 48 months, for a median decrease of approximately 24%.

Over long-term treatment, participants had decreases in CD4+ and CD8+ T-cell counts. After stopping treatment, the researchers found that ALC and LSC changes were reversible, and that 93% of participants with follow-up data achieved ALC ≥500 cells/mm3 after a median of 3 to 6 weeks after discontinuing treatment.

Participants with ALC <500 cells/mm3 had an increased risk for serious infections.

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The researchers did not find any significant associations between serious infection rates and CD4+ T-cell, CD8+ T-cell, B cell, or natural killer cell counts.

“From a clinical perspective, evaluation of ALC at baseline and monitoring every 3 months during treatment is recommended,” the researchers wrote. “Initiation of tofacitinib is not recommended in patients with ALC <500 cells/mm3, and those developing this during treatment should discontinue tofacitinib therapy.”

This study was sponsored by Pfizer, Inc. Please see original article for a full list of author disclosures.

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van Vollenhoven R, Lee EB, Strengholt S, et al. Evaluation of the short-, mid-, and long-term effects of tofacitinib on lymphocytes in patients with rheumatoid arthritis [published online November 14, 2018]. Arthritis Rheumatol. doi:10.1002/art.40780