In patients with moderate to severe psoriasis treated with ustekinumab, higher concentrations of the drug may help identify optimal responders. This is according to a study in the British Journal of Dermatology. The researchers also found that the presence of psoriatic arthritis may help identify patients with greater disease severity.

The study included 49 patients with moderate to severe psoriasis who had received either 45 mg (<100 kg body weight) or 90 mg (≥100 kg body weight) ustekinumab at week 0, week 4, and every 12 weeks for 16 weeks or longer. At 4 weeks and on injection, the researchers evaluated serum concentrations of ustekinumab as well as anti-ustekinumab antibodies. The Psoriasis Area and Severity Index (PASI) was used to assess disease severity at serum sampling. Based on the PASI scores, patients were defined as having either excellent (PASI ≤1), optimal (PASI ≤2), or suboptimal (PASI >2) response.

The study’s investigators found a negative correlation between ustekinumab concentrations and absolute PASI score up to 5.9 μg/mL (P =-.357, P =.032). Optimal responders had higher concentrations of ustekinumab compared with suboptimal responders (4.0 μg/mL vs 2.8 μg/mL, respectively; P =.036). A ustekinumab concentration of 3.6 μg/mL was determined to be the best concentration threshold indicating optimal response (area under the curve = 0.71, sensitivity = 86%, specificity = 63%). Anti-ustekinumab antibodies were found in only 1 patient. An independent predictor of higher PASI scores in this cohort included psoriatic arthritis (P =.003) and the presence of higher ustekinumab concentrations (P =.048).

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Limitations of the study include the small sample size of the cohort as well as the cross-sectional design.

“To conclude,” the researchers wrote, “monitoring 4-week post-injection ustekinumab concentrations could aid in the management of [patients with] psoriasis by timely identifying patients who are underexposed and could benefit from increased dosing or dosing frequency.”

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Reference

Van den Berghe N, De Keyser E, Soenen R, et al. Clinical response correlates with 4-week post injection ustekinumab concentrations in moderate-to-severe psoriasis patients [published online April 20, 2019]. Br J Dermatol. doi:10.1111/bjd.18016.