Alemtuzumab is an effective disease modifying treatment (DMT) for people with relapsing multiple sclerosis (pwRMS). Its mechanism of action includes profound lymphocyte depletion.Objective
To analyse the pattern of lymphocyte depletion and associated infections after alemtuzumab administration in a cohort of pwRMS treated at our centre.Methods
pwRMS treated with alemtuzumab were identified on our clinical record system (Cerner Millennium). Baseline blood results, total lymphocyte counts (TLC) and infections post-treatment were studied.Results
84 pwMS on alemtuzumab were followed up for a mean of 8.7 months. One month after the first treatment cycle, TLC was 13% of baseline (from 2.2 to 0.28 × 109/l). TLC recovered to >0.6 by month 3 and to >1 by month 9, however remained below baseline in all pwRMS. After the 2nd treatment cycle, TLC reconstitution was more rapid, to >1×109/l within six months. 19 (23%) pwRMS had infections within four months of treatment cycles. Infections affected the respiratory tract in 7 (8%) pwRMS, and the urinary tract in 9 (11%). All but one infection occurred with TLC <0.6.Conclusion
Infections are common in pwRMS treated with alemtuzumab. To reduce their incidence prophylactic antibiotics should be considered in pwRMS with TLC of <0.6×109/l.