Observational Study to Compare Biological Drug Concentration Quantification Techniques and Immunogenicity in Patients with Immune-Mediated Diseases.

Measuring biological drugs' trough concentrations and the concentrations of anti-drug antibodies is a valuable practice for treatment optimization. ELISA techniques are the gold standard for biological drug concentration quantification, but new techniques such as chemiluminescence immunoassays present some advantages. The aim of this unicentric prospective observational study is to compare the infliximab, adalimumab, vedolizumab and ustekinumab trough levels and anti-adalimumab and anti-infliximab antibodies concentrations obtained when using a chemiluminescent instrument (i-TRACK®, Theradiag, Croissy-Beaubourg, France) and an ELISA instrument (TRITURUS®, Griffols, Barcelona, Spain). Linear regression, Pearson or Spearman tests, Bland-Altman plots and the Cohen kappa test were applied for every sample. The correlation was excellent for both assays in the measurement of all drug concentrations. In general, values were lower when measured using i-TRACK than when using TRITURUS, especially when the values were high. Both techniques proved valuable in clinical practice for monitoring adalimumab and infliximab drug concentration. However, the results were modest for ustekinumab and vedolizumab, so caution is recommended and further research is needed. The limited number of anti-drug antibody-positive samples precluded a comparison between the techniques.

Real-world use of ustekinumab therapeutic drug monitoring in moderate to severe psoriasis.

Introduction: There is growing evidence that therapeutic drug monitoring of biologic therapy is beneficial in psoriatic patients. With respect to ustekinumab, the available evidence has not shown any relationship yet. The objective of this study is to identify correlations among ustekinumab trough concentrations, anti-ustekinumab antibodies and clinical response in moderate-to-severe plaque psoriasis patients, in a real-world setting. Methods: Observational prospective follow-up study in psoriatic patients treated with ustekinumab. Patients were classified in optimal (PASI ≤ 3) and suboptimal responders (PASI > 3). Mann-Whitney U test and Spearman's rank correlation coefficient were used. Receiver-operator characteristic curve analysis was performed to identify ustekinumab concentration cut-off to achieve optimal response. A p-value < 0.05 was considered statistically significant. Results: A total of 59 patients were included. Forty-eight patients (81.4%) corresponded to optimal responders and 11 (18.6%) to suboptimal responders. There was significant difference to ustekinumab concentrations: 0.7 µg/mL (range <0.1-1.8) vs. 0.4 µg/mL (range <0.1-0.8) respectively (p = 0.007). Positive correlation between ustekinumab concentration and psoriasis area and severity index (PASI) value was detected (p = 0.009). A cut-off value of 0.6 µg/mL ustekinumab concentration was found to achieve clinical response. Anti-ustekinumab antibodies were detected in 2 (3.4%) samples, both suboptimal responders. Conclusion: A positive correlation exits between ustekinumab concentration and clinical response (optimal response PASI values ≤ 3) in blood draws performed before drug administration. The measurement of anti-ustekinumab antibodies could be considered in treatment failure.

Biologic Therapy for Moderate to Severe Psoriasis. Real-World Follow-up of Patients Who Initiated Biologic Therapy at Least 10 Years Ago.

INTRODUCTION: The aim of this study was to evaluate response and drug survival of biologic therapy in patients with moderate to severe plaque-type psoriasis who initiated biologic therapy at least 10 years ago, in a real-world setting. METHODS: This was an observational retrospective follow-up study that included patients with moderate to severe plaque-type psoriasis who initiated biologic therapy between October 2006 and December 2009. Efficacy was expressed as the percentage of patients achieving a 50, 75 and 90% reduction from baseline in the Psoriasis Area and Severity Index (PASI 50, PASI 75, PASI 90, respectively) every 3 months during the first year of therapy and then every 12 months up to the end of follow-up or withdrawal from the study. RESULTS: A total of 56 patients were included in the study, representing 140 treatment lines (median 2, range 1-8); of these patients, 53 were still receiving biologic therapy at the end of the study. The mean duration of biologic therapy was 140.4 (range 47.6-175.4) months. Etanercept was used in 98.2% of patients, followed by efalizumab (42.9%), adalimumab (41.1%), ustekinumab (33.9%) and infliximab (16.1%). Treatment lines were switched in 62.1% of treatments: 24.3% due to secondary failure, 20.7% due to primary failure and 3.6% due to side effects. No patient treated with anti-interleukins had to discontinue treatment due to side effects. Ustekinumab had the highest drug survival. CONCLUSIONS: This study in the real-world-setting shows maintenance of long-term efficacy and safety of biologic therapy in patients with moderate to severe plaque psoriasis in daily practice who initiated biologic therapy 10 years ago.