Most RA patients who switch from intravenous to subcutaneous tocilizumab are able to maintain disease control but efficacy is reduced in heavier patients, results of a phase III study shows.
Patients who weighed below 70 kg maintained remission after switching, while the remission rate fell from 72.7% (8/11) to 27.3% (3/11) in patients above that weight.
In patients with a BMI above 25 kg/m2 remission rates fell from 66.7% (14/21) to 42.9% (9/21), reported the authors in Arthritis Care and Research.
Serum trough concentrations of tocilizumab (Actemra) showed that among patients weighing 70 kg or more, the percentage who maintained serum concentrations of 1 mcg/mL or higher after switching from the intravenous to the subcutaneous formulation decreased from 90.9% at 6 months to 45.5% at 9 months.
This suggested “that the efficacy of a fixed-dose regimen of subcutaneous tocilizumab may be reduced in rheumatoid arthritis patients with high body weights,” they said.
“Weekly administration of subcutaneous tocilizumab may be beneficial for restoring a sufficient serum concentration of tocilizumab in patients with high body weights who have inadequate responses to biweekly subcutaneous tocilizumab,” they concluded.
The study randomised 322 RA patients to 6 months of intravenous tocilizumab, 8 mg/kg every 4 weeks (plus a dummy subcutaneous dose every 2 weeks) or a fixed dose of 162 mg subcutaneously every 2 weeks (plus a dummy intravenous dose every 4 weeks). The additional 3 months were open-label.