Adherence to etanercept therapy in rheumatoid arthritis patients during 3 years of follow-up.

OBJECTIVES: To determine the percentage non-adherence to etanercept in patients with rheumatoid arthritis during three years of follow-up. METHODS: During study visits in this prospective cohort study, blood samples were taken to determine serum etanercept concentrations using ELISA and patients were asked if they had missed an etanercept dose, at which date and for what reason. Non-adherence was defined as serum etanercept concentration <0.1 µg/mL and no valid reason to miss the prescribed etanercept dose. RESULTS: In total, 292 consecutive patients treated with etanercept were included. Most patients had a valid reason to miss their etanercept dose (25/37). In total 12 out of 292 patients (4.1%, 95% confidence interval 2.2-7.2) were non-adherent during the 3 year period. In a small percentage of patients (3.4%, 95% confidence interval 0.8-10.4) who failed to respond to etanercept therapy, according to their rheumatologist, this was associated with inadequate exposure to etanercept and thus non-adherence. CONCLUSION: In this study, adherence to etanercept therapy was measured using serum etanercept concentration. In most patients an absent etanercept concentration was due to a medical reason. Furthermore, the majority of patients were adherent to etanercept therapy and had adequate drug exposure. In total, only 12 out of 292 patients (4.1%) were non-adherent during 3 years of follow-up. These findings highlight that only a small minority of patients are non-adherent to etanercept treatment, especially compared to adherence rates of other drugs. However, physicians should be aware that in patients failing to respond to treatment, non-adherence is a possible cause.

Lower etanercept levels are associated with high disease activity in ankylosing spondylitis patients at 24 weeks of follow-up.

BACKGROUND: Previous data have shown that etanercept levels are associated with clinical response in rheumatoid arthritis. However, for ankylosing spondylitis (AS), data regarding this topic are inconclusive. OBJECTIVES: To investigate the relationship between etanercept levels and clinical response in patients with AS. METHODS: Observational prospective cohort study of 162 patients with AS =treated with etanercept, monitored during 24 weeks of treatment. Etanercept trough levels were determined, retrospectively, using an ELISA. Disease activity was measured using AS Disease Activity Score (ASDAS), including C-reactive protein (CRP) and Bath AS Disease Activity index (BASDAI). Active disease was defined as ASDAS≥2.1. Since etanercept is a drug administered at home there might have been some variation in trough level sampling. RESULTS: At 24 weeks etanercept levels were significantly higher in patients with ASDAS<2.1, (3.8 mg/L; IQR 2.5-5.2) compared with patients with ASDAS≥2.1 (2.3 mg/L; IQR 1.2-3.4; p≤0.001). Generalised estimating equation analysis demonstrated a statistically significant association between etanercept levels and ASDAS, BASDAI, CRP and erythrocyte sedimentation rate (all p<0.001). When patients were categorised into quartiles according to etanercept levels, the lowest quartile (etanercept<1.80 mg/L) comprised 35% of all patients with ASDAS≥2.1 while the highest quartile comprised only 14%. CONCLUSIONS: Disease activity and inflammation are associated with etanercept levels in patients with AS at 24 weeks of treatment. Measuring etanercept levels might help in identifying overtreatment and undertreatment and optimise etanercept therapy in AS.

Personalised treatment using serum drug levels of adalimumab in patients with rheumatoid arthritis: an evaluation of costs and effects.

OBJECTIVE: To evaluate the cost-effectiveness of personalised treatment for rheumatoid arthritis (RA) using clinical response and serum adalimumab levels. METHODS: A personalised treatment algorithm defined, based on clinical (European League Against Rheumatism) response and drug levels at 6 months, whether adalimumab treatment should be continued in a specific dose or discontinued and/or switched to a next biological. Outcomes were simulated using a patient level Markov model, with 3 months cycles, based on a cohort of 272 adalimumab-treated patients with RA for 3 years and data of patients from the Utrecht Rheumatoid Arthritis Cohort. Costs, clinical effectiveness and quality adjusted life years (QALYs) were compared with outcomes as observed in usual care and incremental cost-effectiveness ratios were calculated. Analyses were performed probabilistically. RESULTS: Clinical effectiveness was higher for the cohort simulated to receive personalised care compared with usual care; the average difference in QALYs was 3.84 (95 percentile range -8.39 to 16.20). Costs were saved on drugs: €2 314 354. Testing costs amounted to €10 872. Mean total savings were €2 561 648 (95 percentile range -3 252 529 to -1 898 087), resulting in an incremental cost-effectiveness ratio of €666 500 or €646 266 saved per QALY gained from a societal or healthcare perspective, respectively. In 72% of simulations personalised care saved costs and resulted in more QALYs, in 28% it was cost saving with lower QALYs. Scenario analyses showed cost saving along with QALYs gain or limited loss. CONCLUSIONS: Tailoring biological treatment to individual patients with RA starting adalimumab using drug levels and short-term outcome is cost-effective. Results underscore the potential merit of personalised biological treatment in RA.

Venous and arterial thromboembolic events in adalimumab-treated patients with antiadalimumab antibodies: a case series and cohort study.

OBJECTIVE: We observed 3 patients who developed severe venous and arterial thromboembolic events during treatment with adalimumab, 2 of whom had rheumatoid arthritis (RA) and 1 of whom had psoriatic arthritis. Antiadalimumab antibodies were detected in all 3 patients. We undertook this study to determine whether the development of antiadalimumab antibodies was associated with thromboembolic events during adalimumab treatment. METHODS: A retrospective search (with blinding with regard to antiadalimumab antibody status) for thromboembolic events was performed in a prospective cohort of 272 consecutively included adalimumab-treated RA patients. Incidence rates were calculated and hazard ratios (HRs) were estimated using Cox regression. None of the index patients were part of the cohort. RESULTS: Antiadalimumab antibodies were detected in 76 of 272 patients (28%). Eight thromboembolic events were found, 4 of which had occurred in patients with antiadalimumab antibodies. The incidence rate was 26.9/1,000 person-years for patients with antiadalimumab antibodies and 8.4/1,000 person-years for patients without those antibodies (HR 3.8 [95% confidence interval 0.9-15.3], P = 0.064). After adjustment for duration of followup, age, body mass index, erythrocyte sedimentation rate, and prior thromboembolic events, the HR was 7.6 (95% confidence interval 1.3-45.1) (P = 0.025). CONCLUSION: These findings suggest that the occurrence of venous and arterial thromboembolic events during adalimumab treatment is higher in patients with antiadalimumab antibodies than in those without antiadalimumab antibodies. Patient numbers were relatively small; therefore, validation in other cohorts is mandatory.