medwireNews: Findings from the phase 3b COSMOS trial indicate that guselkumab, a selective monoclonal antibody targeting the interleukin-23 p19 subunit, may improve outcomes for patients with active psoriatic arthritis (PsA) and an inadequate response to tumor necrosis factor (TNF) inhibitors.
Speaking at the EULAR 2021 Virtual Congress, Laura Coates (University of Oxford, UK) said that two prior phase 3 studies – DISCOVER-1 and DISCOVER-2 – showed significantly better joint and skin responses at week 24 among PsA patients treated with guselkumab versus placebo. She noted that guselkumab showed consistent efficacy in a subgroup of TNF inhibitor-experienced patients from DISCOVER-1, a population of PsA patients with “significant unmet needs.”
The COSMOS study focused on such patients, and included 285 individuals with active PsA and an inadequate response or intolerance to one or two TNF inhibitors. Participants were randomly assigned to receive subcutaneous guselkumab 100 mg once every 8 weeks (following 100 mg loading doses at weeks 0 and 4) or placebo.
Coates reported that baseline data showed “significant disease activity across domains” in the guselkumab and placebo groups. The majority (88–89%) of participants had received one prior TNF inhibitor, and this treatment was predominantly discontinued due to an inadequate response (82–84%).
At week 24, ACR20 response rates were significantly higher among participants treated with guselkumab versus placebo, at 44.4% versus 19.8%. Coates noted that this benefit was consistent when participants were categorized into subgroups according to baseline patient and disease characteristics.
Placebo-treated participants were switched to guselkumab at week 24, and ACR20 response rates at week 48 were comparable among patients treated with guselkumab for the duration of the study and those who switched from placebo, at 57.7% and 54.9%, respectively.
Guselkumab also significantly improved a range of secondary endpoints relative to placebo at week 24 – including HAQ-DI, ACR50 response rates, and resolution of enthesitis and dactylitis – with further improvements seen at the 48-week follow-up.
“The results of the COSMOS study through 1 year suggested durable and broad impact of targeting the p19 subunit of interleukin-23 in active psoriatic arthritis patients who have previously had an inadequate response to one or two [TNF] inhibitors,” said Coates.
She added that guselkumab was “well tolerated and demonstrated a favorable benefit:risk profile,” which “was consistent with the established safety profile in psoriasis and psoriatic arthritis guselkumab studies.”
There were no reports of opportunistic infections, active tuberculosis, anaphylactic/serum sickness-like reaction, confirmed inflammatory bowel disease, or death during the COSMOS study.
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