Support for lymphocyte count monitoring to assess infection risk in tofacitinib-treated RA patients
medwireNews: Absolute lymphocyte counts (ALCs) can provide guidance on serious infection risk among patients with rheumatoid arthritis (RA) who are undergoing tofacitinib treatment, say researchers.
In a post-hoc analysis of data from phase III trials and phase I–III long-term extension studies including a total of 7061 RA patients, Lisy Wang (Pfizer Inc, Groton, Connecticut, USA) and colleagues demonstrated that patients given the Janus kinase inhibitor experienced an initial increase in ALC during the first month of treatment, followed by a gradual decline to a steady state by the 48-month follow-up.
Specifically, median ALCs increased by approximately 100 cells/mm3 during the first month of treatment for patients taking tofacitinib 5 mg or 10 mg twice daily plus methotrexate in the ORAL Standard trial, and by approximately 250 cells/mm3 among methotrexate-naïve patients treated with the same doses of tofacitinib in the ORAL Start trial.
And in the total population of tofacitinib-treated patients from the clinical trials and long-term extension studies, median ALC decreased by around 24% from baseline to the 2-year follow-up, stabilising at a decrease of approximately 400 cells/mm3, report the researchers in Arthritis & Rheumatology.
Wang and colleagues found that patients with lower ALCs had a higher risk of serious infection, with incidence rates of 7.1 per 100 patient–years for those in the lowest ALC category (<500 cells/mm3), and 2.4 per 100 patient–years for those in the highest ALC category (≥2000 cells/mm3).
Similarly, the researchers report that herpes zoster “generally showed an increasing risk with lower ALC values”, at incidence rates of 4.2 versus 2.9 per 100 patient–years for patients in the lowest and highest ALC categories, respectively.
These results suggest that “[f]rom a clinical perspective, evaluation of ALC at baseline and monitoring every 3 months during treatment, is recommended”, say Wang and team, adding that “[i]nitiation of tofacitinib is not recommended in patients with ALC <500 cells/mm3, and those developing this during treatment should discontinue tofacitinib therapy.”
The study authors also point out that ALCs “correlated well” with CD4+ and CD8+ T-cell counts, and they observed “no strong correlation” between CD4+ and CD8+ T-cell counts and serious infection risk, indicating that “ALC monitoring alone appears to be adequate to assess infection risk in tofacitinib-treated patients with RA.”
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