Intended for healthcare professionals

Rapid response to:

Analysis And Comment Drugs

Lessons for clinical trials from natalizumab in multiple sclerosis

BMJ 2006; 332 doi: (Published 16 February 2006) Cite this as: BMJ 2006;332:416

Rapid Response:

Erratum / apology

I am indebted to Gavin Giovannoni for pointing out a major error in
the calculations I made for my rapid response dated 17/02/06.

For some reason, I have read the annualised reduction in relapse
rates from the AFFIRM and SENTINEL trials as a %rate per patient year,
rather than absolute rate per patient.

Consequently I have underestimated the treatment benefit by a factor
of 100, and the NNT should indeed be around 2, rather than 200. Which
makes Natalizumab highly effective, and the cost issue wholly different at
around $47000 per relapse prevented.

Once other cost-utilities (quality of life, prevention of progression
to disability, costs of disability) are taken into account I imagine
Natalizumab may well be approaching the £30K per QUALY NICE uses as it's
benchmark for approval.

I will try to remember to refrain from commenting on NNTs in future
without a chance to peruse the raw data first (somewhat chastened, I am
typing this with both March 2nd NEJM articles (1,2) at my elbow. There are
a lot of potential NNTs, for multiple secondary outcomes, and all rather
low - in the order of 2-3 at worst).

Once more, my apologies.

(1) Polman CH, O’Connor PW, Havrdova E, et al. A randomized, placebo-
controlled trial of natalizumab for relapsing multiple sclerosis. N Engl J
Med 2006;354:899-910.

(2) Rudick R, Stuart WH, Calabresi PA, et al. Natalizumab plus
interferon beta-1a for relapsing multiple sclerosis. N Engl J Med

Competing interests:
None declared

Competing interests: No competing interests

14 March 2006
Matthew L Grove
Consultant Rheumatologist