In a study of patients with psoriasis who had previously failed treatment with interleukin-17 receptor A inhibitor therapy, “all patients with quantifiable levels of brodalumab after 12 weeks of therapy experienced PASI reductions” and subquantifiable brodalumab levels were associated with a lack of response after 12 weeks, they wrote in JAMA Dermatology.
Lead study author Christian Enevold, PhD, a researcher at the Institute for Inflammation Research at Copenhagen University Hospital, and colleagues monitored patients with plaque psoriasis who had not improved with previous IL-17A inhibitor therapy, to evaluate whether trough levels and antidrug antibodies were associated with clinical response in this group of patients.
The 20 consecutive adult patients were treated at two academic hospital dermatology clinics between 2018 and 2020 and ranged in age from 19 to 66 years; 13 were male. At baseline, their weight ranged from 59 to 182 kg (median, 103 kg), their body mass index (BMI) ranged from 20 to 50 (median, 32), and their Psoriasis Area and Severity Index (PASI) scores ranged from 7 to 26 (median, 13). All had failed treatment with at least one IL-17A inhibitor, and 90% had failed treatment with at least one tumor necrosis factor–alpha or IL-12/-23 inhibitor.
Patients stopped taking systemic psoriasis therapies for 4 weeks before entering the study, then received subcutaneous injections of 210 mg of the IL-17A inhibitor brodalumab (Siliq) at weeks 0, 1, 2, and every 2 weeks thereafter. Patients whose PASI scores did not improve at least 75% from baseline (PASI 75) after 12 weeks of brodalumab discontinued treatment and left the study, while those who maintained PASI 75 were monitored for up to 52 weeks.
The researchers used assays to compare decreases in PASI score with brodalumab levels as well as with antibrodalumab antibodies at 12 weeks, and determined the following:
- Participants with quantifiable brodalumab levels (≥ 0.05 mcg/mL) showed a greater drop in PASI scores (median, 93%; range, 61%-100%) than those without quantifiable brodalumab levels (median, −3; range, −49% to 94%) (P = .006).
- Four of 5 patients (80%) who did not achieve a PASI 75, compared with 3 of 14 PASI 75 responders (21%), had drug levels too low to be measured (< 0.05 mcg/mL).
- The eight patients who did not have obesity (BMI < 30) had PASI reductions of at least 77%, and seven of the eight patients (88%) had quantifiable brodalumab levels.
- Six of the 12 patients with obesity (BMI ≥ 30) had brodalumab levels too low to be measured. Of those, four had increased PASI after 12 weeks of treatment. For all patients with obesity with quantifiable brodalumab levels, PASI scores dropped by at least 61% after 12 weeks.
- Five of the 12 (42%) patients with obesity versus 7 of the 8 (88%) patients without obesity had quantifiable brodalumab levels.
- None of the seven patients (35%) with subquantifiable drug levels after 12 weeks remained PASI responders.
- No antibrodalumab antibodies were detected in any serum samples.