Research: adverse events after natalizumab

#MSBlog #MSResearch What constitutes a rare adverse event? Two deaths out of 103 treated MSers?

Fragoso et al. Natalizumab adverse events are rare in patients with multiple sclerosis. Arq Neuropsiquiatr. 2013 71:137-141. 

Objective: To assess the prevalence and the profile of adverse events (AE) of natalizumab. 

Methods: Data collection from neurologists attending to MSers at specialized units in Brazil.

Results: Data from 103 MSers attending the infusion centres of 16 MS units in 9 Brazilian states were included in the study. The total number of infusions was 1,042. Seventy-nine MSers(76.7%) did not present any AE. Twenty-four MSers (23.3%) presented only mild AE. There were three major AE, including two deaths. These three occurrences, although not necessarily being drug-related, must be taken into consideration. The two female adult MSers who died in this study both presented with their complications after the first infusion. One died of a heart attack and the other  had severe lung infection, respiratory distress and septicemia.

Conclusion:  The profile of AEs for natalizumab shows that 97% of patients have none or only mild AE. However, still due to safety worries, the use of this medication should be restricted to MS units under the care of specialized neurologists.

“These results are in accordance with our own experience that natalizumab is generally well-tolerated with few adverse events. The commonest being infusion reactions, which occur in ~5% and are linked to the presence of anti-natalizumab antibodies. Worrying in this report are the 2 deaths that occurred after their first infusion; to the best of my knowledge these cases are very unusual. The fact that both died after their first infusion suggests that the deaths are unrelated to natalizumab. Is two deaths out of 103 MSers not enough to question the use of rare in the title of their paper? Rare to me is less than 1 in a 1,000; in comparison in 1 in 52 is common.”

CoI: multiple

About the author

Prof G

Professor of Neurology, Barts & The London. MS & Preventive Neurology thinker, blogger, runner, vegetable gardener, husband, father, cook and wine & food lover.


  • What about problems with the Thyroid gland?
    A collegue of mine who's been on Natalizumab for over 5 years recently experinced that and the doctors had told him it's not so uncommon. I've nevet heard or read about it before.
    All the best
    /Swedish Sara

    • Thyroid diseases are not a complication of natalizumab, unlike alemtuzumab. MSers appear to be at greater risk of developing thyroid diseases compared to the general population. This is not universally accepted by all. Because of the association, I check thyroid function annually in all my MSers who complain of fatigue; fatigue is a common symptom of thyroid dysfunction and it is a treatable condition. I am not sure if this is cost-effective and it is not evidence-based. I will need to audit this at a clinical level. The NHS won't like me wasting money on unnecessary blood tests; I need to generate the evidence to justify my clinical practice.

  • oh, I am reading all of your comments on natalizumab and PML before assessment for a trial for SPMS/natalizumab. 1 in 52 doesnt seem rare to me either 🙁 The benefits seem clear and maybe for SPMS too….I guess only I can decide whether to do it or not?

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