Plasma trough levels of adalimumab and infliximab in terms of clinical efficacy during the treatment of psoriasis

We examined the relation between adalimumab and infliximab plasma trough levels, anti‐adalimumab and anti‐infliximab antibody formation. We analyzed plasma from 32 adalimumab‐treated and 20 infliximab‐treated psoriasis patients for evaluating trough levels of each drug. The presence of anti‐adalimumab and anti‐infliximab antibodies was analyzed and the severity of psoriasis was evaluated. At week 28, 25 out of 32 and at week 48, 21 out of 30 adalimumab‐treated patients maintained as more than PASI 75. At week 28, 12 out of 20 and at week 48, nine out of 18 infliximab‐treated patients were evaluated as more than PASI 75. In patients treated with 40 mg adalimumab every other week, the mean trough level was 7.62 μg/mL (range, 0.05–10.6) at week 48. In patients treated with 80 mg adalimumab every other week, the mean trough level was 8.61 μg/mL (range, 0.08–13.5) at week 48. Mean trough level of infliximab‐treated cases (4.1–5.2 mg/kg; mean, 4.6) was 4.64 μg/mL (range, 0.03–16.9) at week 48. Anti‐adalimumab antibody was detected in five out of 32 cases and anti‐infliximab antibody was detected in six out of 20 cases, respectively, at weeks 24 and 48. The optimal cut‐off values of adalimumab and infliximab concentration for more than PASI 75 were more than 7.84 μg/mL and more than 0.92 μg/mL, respectively. The trough levels of adalimumab and infliximab in psoriasis patients were positively associated with clinical response and were significantly lower in cases having anti‐adalimumab or anti‐infliximab antibodies.