An Effective Therapeutic Range for Adalimumab?

A study from the Netherlands has found a range of minimum serum levels of adalimumab that are associated with a good clinical response in rheumatoid arthritis. As in other studies, adding methotrexate helps.

Pouw MF, Krieckaert CL, Nurmohamed MT, et al., Key findings towards optimising adalimumab treatment: the concentration-effect curve.Ann Rheum Dis. (2013) Dec 10. doi: 10.1136/annrheumdis-2013-204172. [Epub ahead of print]

There is no single dose of adalimumab (Humira) proven effective for most rheumatoid arthritis (RA) patients, but a new study from the Netherlands does find a range of minimum serum levels linked to a good clinical response in RA.

The observational cohort study enrolled 221 RA patients, who were treated with 40 mg adalimumab (ADA) subcutaneously every other week, either alone or in combination with methotrexate (MTX) or prednisone, and followed for a median of 28 weeks.

Serum samples were collected just before the next injection, with patients sorted by serum concentration levels and treatment response judged by their disease activity score in 28 joints (DAS28). Mean baseline DAS28 of the cohort was 5.3, which is considered high disease activity according to American College of Rheumatology standards.

After 28 weeks, minimum ADA serum levels (trough levels) of 5-8 Î¼g/mL were shown to be sufficient to produce a good clinical response, defined by the European League Against Rheumatism (EULAR) as a decrease of more than 1.2 points in an RA patient’s DAS28 from 3.2.

ADA serum levels above 8 Î¼g/mL were not associated with added benefits.

Patients on ADA monotherapy had a median ADA trough level of 4.1 Î¼g/mL compared with those concomitantly taking MTX, whose median serum level was 7.4 Î¼g/mL.

The researchers conclude that even a low dose of concomitant MTX dose helps optimize ADA treatment -- a finding in line with recent clinical trials that show combined therapy is more effective than monotherapy.