A study published this week has gone some way to answering a question on EULAR’s research agenda – is the measurement of drug and/or antibody levels useful in clinical practice?

Writing in Arthritis & Rheumatology the team of researchers led by Professor Anne Barton from the Arthritis Research UK Centre for Genetics and Genomics said the ability to predict non-response at an early stage of biologic treatment could have potential major health economic implications as well as help to optimise patient care.

One explanation of poor efficacy to anti-TNF therapies is immunogenicity leading to the development of anti-drug antibodies (ADAb) and low drug levels, they said.

However the clinical utility of pharmacological monitoring in practice continues to be debated.

Their study of 331 RA patients selected from the Biologics in Rheumatoid Arthritis Genetics and Genomics Study Syndicate (BRAGGSS) found that at 3 months ADAb formation and low adalimumab levels were significant predictors of a lack of EULAR response at 12 months.

Patients who were ADAb-positive received lower median methotrexate doses (15 vs. 20mg/wk, p=0.01) and had longer disease duration (14.0 vs. 7 years, p=0.03), results showed. 

Etanercept drug levels, tested in non-trough serum samples, had a wider variation over 12 months of treatment and were less useful as a predictor of future treatment response, the researchers said.

BMI and adherence appear to be significant predictors of drug levels in both adalimumab and etanercept treated patients.

“Our study demonstrates for the first-time that adalimumab drug levels and ADAb status, ascertained from non-trough serum samples, are useful in the early prediction of EULAR response at 12 months,” the researchers concluded.

Consideration of these factors alongside BMI and adherence may help with deciding the best treatment strategy in patients in whom adalimumab does not appear effective, they said.