medwireNews: Findings from the SPIRIT-H2H trial, presented at the EULAR 2019 congress in Madrid, Spain, have demonstrated superior efficacy of ixekizumab versus adalimumab among patients with psoriatic arthritis (PsA).
“This is the first head-to-head trial between two biologic medications in the treatment of PsA,” lead investigator Philip Mease (University of Washington, Seattle, USA) told medwireNews.
The 52-week open-label phase IV trial included 566 biologic-naïve patients with an inadequate response to one or more conventional DMARDs who were randomly assigned to receive the interleukin-17A inhibitor ixekizumab or the tumor necrosis factor (TNF) inhibitor adalimumab for 1 year. Both drugs were given subcutaneously at doses according to the labels based on the presence or absence of moderate-to-severe plaque psoriasis.
The study authors found that a significantly greater proportion of patients given ixekizumab versus placebo achieved the primary endpoint of both an ACR50 and a PASI100 response at week 24, with rates of 36% versus 28%.
For the key secondary endpoints, ACR50 responses were achieved by 51% of participants given ixekizumab and 47% of those in the adalimumab group, meeting noninferiority criteria, while PASI100 response rates were significantly higher for patients given ixekizumab, at 60% versus 47% in the adalimumab group.
Mease explained that all participants of the SPIRIT-H2H trial were required to have plaque psoriasis covering at least 3% of their body surface area (BSA) at the time of study entry, which he said is “a little bit different to other PsA studies because that minimal amount of skin psoriasis is not required typically in most PsA studies.”
He acknowledged that the primary endpoint and skin response results might be expected “because ixekizumab is known to do so much better in the skin.” However, he pointed out that a significantly higher proportion of patients given ixekizumab versus adalimumab achieved remission according to a Disease Activity for Psoriatic Arthritis (DAPSA) score of 4 points or less (27 vs 18%), which he described as an “intriguing” finding because DAPSA is “considered a joint-centric outcome measure, with “no skin, nail, enthesitis, [or] dactylitis item.”
Mease said that the safety profile of ixekizumab in the SPIRIT-H2H trial “was as expected from previous data on the drug.” In all, 3.5% of participants in the ixekizumab group and 8.5% of those given adalimumab experienced serious adverse events (AEs), while 2.5% and 4.6%, respectively, discontinued treatment due to AEs.
Injection site reactions were reported in 9.5% of ixekizumab-treated patients and 3.2% of those in the adalimumab group. He noted that the new citrate-free form of adalimumab was used in the trial, which is associated with a lower incidence of injection site reactions than the original formulation.
Taken together, the SPIRIT-H2H results “give some support for if a clinician were to want to use [ixekizumab] earlier in the treatment paradigm,” concluded Mease.
However, he conceded that in reality, there is likely to be “a push towards use of TNF inhibitors first,” partly due to economic reasons.
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