The following is a summary of “Non-trough adalimumab and certolizumab drug levels associated with a therapeutic EULAR response in adherent patients with rheumatoid arthritis,” published in the June 2023 issue of Rheumatology by Hum, et al.
For a study, researchers sought to establish the relationship between serum drug levels (SDLs) of adalimumab/certolizumab (TNF-α inhibitors) and treatment response in patients with rheumatoid arthritis (RA). Specifically, the study aimed to define SDL cut-offs associated with a good response in fully adherent patients.
A total of 475 patients with RA were included in the study, with 192 receiving certolizumab and 283 receiving adalimumab. Patients’ 28-joint Disease Activity Score (DAS) and self-reported treatment adherence were assessed at baseline, 3 months, 6 months, and 12 months. SDLs were measured at each time point. The analysis focused on fully adherent patients as a subgroup. Follow-up data at 3 months, 6 months, and 12 months were analyzed separately.
The results showed that fully adherent patients who were classified as good responders had significantly higher median SDLs of adalimumab/certolizumab compared to non-/moderate responders (P = 0.04 and P = 0.0005, respectively). Receiver operating characteristics (ROC) curve analysis was performed to determine SDL cut-offs associated with good response. For adalimumab, the 3-month non-trough SDLs discriminated good response from non-/moderate response with an area under the curve (AUC) of 0.63 (95% CI 0.52, 0.75). The cut-off of 7.5 mg/L had a specificity of 39.1% and sensitivity of 80.9% for predicting a good response. For certolizumab, the 3-month non-trough SDLs discriminated good response from non-/moderate response with an AUC of 0.65 (95% CI 0.51, 0.78). The cut-off of 26.0 mg/L had a specificity of 43.9% and sensitivity of 77.8% for predicting a good response.
In conclusion, the study suggested that higher SDLs of adalimumab/certolizumab were observed in fully adherent patients who achieved a good treatment response in RA. The finding implied that interventions aimed at improving SDLs, such as promoting treatment adherence, could potentially enhance treatment response. The identified SDL cut-offs of 7.5 mg/L for adalimumab and 26.0 mg/L for certolizumab at 3 months may have practical utility in clinical practice for assessing treatment response.