Neither baseline Th17-associated cytokines nor C-reactive protein levels were predictive of response to ustekinumab in patients with psoriatic arthritis, despite significant reductions following treatment, according to Stefan Siebert, PhD, of the University of Glasgow (Scotland) and associates.
In a study published in Arthritis & Rheumatology, the authors retrospectively analyzed serum samples collected from 927 patients with psoriatic arthritis who participated in the phase 3 PSUMMIT trials. Patients received ustekinumab (Stelara) or placebo, and samples were collected at baseline, 4 weeks, and 24 weeks.
At baseline, interleukin-17A, -17F, and -23 levels were associated with skin disease scores, but neither these nor C-reactive protein (CRP) were associated with joint disease scores. While IL-17A, IL-17F, and CRP were reduced in patients who responded to ustekinumab, baseline levels of IL-17A, IL-17F, IL-23, and CRP were not associated with ustekinumab response in either skin or joints.
In patients who achieved a 75% reduction in their Psoriasis Area and Severity Index scores or a 20% reduction in their American College of Rheumatology response score after 24 weeks, CRP levels were significantly lower than in patients who did not achieve these scores (51%-58% vs. 32%-33%; P less than .05). However, IL-17A and IL-17F levels were not significantly different in these patients.
“While the biomarkers studied in the PSUMMIT program did not translate into therapeutic utility, it is important that relevant biomarker studies associated with phase 3 clinical trial programs are published in order to increase our understanding of this complex disease and further dissect the role of the IL-23/IL-17 pathway,” the investigators concluded.
The study was funded by Janssen; four coauthors reported being employed with Janssen.
SOURCE: Siebert S et al. Arthritis Rheumatol. 2019 May 9. doi: 10.1002/art.40921.