Tocilizumab concentrations tied to clinical improvement in RA patients

A personalized approach in the dosing of subcutaneous tocilizumab (TCZ) injections according to body weight appears to be effective in improving outcomes of clinical disease activity in patients with rheumatoid arthritis (RA), suggests a study.

“In the first 24 weeks of treatment with subcutaneous TCZ injections, TCZ concentrations were associated with clinical improvement, while body weight and body mass index (BMI) were inversely associated with TCZ concentrations,” the researchers said.

An analysis was conducted on datasets from the Israeli branch of the multinational TOZURA study, which evaluated a weekly subcutaneous TCZ treatment regimen in a real-life clinical setting, to determine whether serum TCZ trough concentrations administered as a fixed-dose subcutaneous injection for the treatment of RA correlated with disease activity responses.

The associations between TCZ levels and study outcomes were assessed using generalized estimating equations (GEE). Associations between patient characteristics and TCZ levels were evaluated using linear models and GEE.

TCZ concentrations significantly correlated with the change in the Clinical Disease Activity Index (CDAI) score. The multivariable binary GEE model revealed that each 10-µg/ml increase in TCZ concentration correlated with being in a state of CDAI remission or low disease activity (odds ratio [OR], 1.41) vs a moderate/high disease activity state.

Moreover, an OR of 1.52 was associated with being in a state of Health Assessment Questionnaire–Disability Index remission.

Univariate linear models showed an inverse association between BMI and improvement in the CDAI score, as well as between BMI score and lower TCZ concentrations. Of note, patients weighing >100 kg showed lower TCZ concentrations.