Ixekizumab Outperforms Adalimumab in Head-to-Head Psoriatic Arthritis Trial

A head-to-head comparison of 2 popular biologic DMARDs for psoriatic arthritis has found ixekizumab (Taltz) provided significantly greater simultaneous joint and skin improvement compared to adalimumab (Humira) consistently from week 8 to week 52.

Final results of the 52-week SPIRIT-H2H trial, which also revealed ixekizumab performed at least as adalimumab in improvement of musculoskeletal and skin domains, were presented for the first time at the 2019 American College of Rheumatology annual meeting in Atlanta, GA.

The SPIRIT-H2H study was a multicenter, randomized, open-label, parallel-group phase 3b/4 study that utilized blinded outcome assessments to assess the efficacy and safety of ixekizumab versus adalimumab in biologic-naive patients with moderate to severe psoriatic arthritis. A total of 566 patients were included in the study and were randomized in a 1:1 ratio to receive either ixekizumab or adalimumab. At week 52 of the study, 87% of the ixekizumab group an 84% of the adalimumab had completed the study.

Investigators noted on-label dosing was used for both adalimumab and ixekizumab. Additionally, use of concomitant conventional DMARDs was also permitted during the study period.

The primary outcome measure of the study was simultaneous achievement of ACR50 and PASI100 response at week 52. Secondary outcome measures of the study included the demonstration of non-inferiority in ACR50 and superiority in PASI 100.

At week 52, analyses revealed 39% of patients in the ixekizumab group and 26% of the adalimumab group achieved the primary endpoint of simultaneous ACR50 and PASI100. Investigators noted 64% of patients receiving ixekizumab and 41% in the adalimumab group achieved PASI 100 when examined separately.

Results of the study also indicated ixekizumab performed as well as adalimumab in the other endpoints included in the study, such as ACR20, ACR 70, PASI90, and PASI75 among others. In regard to safety, treatment-emergent adverse events occurred in 73.9% of ixekizumab patients and 68.6% of adalimumab patients.

Additionally, 4.2% of patients receiving ixekizumab and 12.4% receiving adalimumab experienced serious treatment-emergent adverse events. No deaths occurred , but discontinuations due to adverse events occurred in 7.4% of the adalimumab group and 4.2% of the ixekizumab group.

For a better understanding of the clinical impact of this head-to-head study, Philip Mease, MD, director of rheumatology research at Swedish Rheumatology Research Group, sat down with us between sessions at ACR 2019 to offer his insights on the data.

MD Mag: What were the results of the SPIRIT-H2H study?

Mease: A bit of interesting new information about psoriatic arthritis treatment presented here at the ACR meeting. One is the 52-week data on the Taltz vs. Humira head to head trial in psoriatic arthritis. In that trial at the 24 week mark, there was superior effectiveness of towards in achieving a combined primary endpoint of PASI100 and ACR 50 response. A non-inferior improvement in ACR50 response.

So, the 2 are very similar in that more articulate measure and then a superior effect of Taltz in PASI100 response. This is partly to be expected based on what we know about interleukin 17 inhibition and psoriasis.

At the 52-week time point, these results were sustained—showing ongoing efficacy of both agents. So, we really aren't seeing a loss of effectiveness over time. There was a sub study within that in which they analyzed the effect of background methotrexate or not, and found that there was more impact if you didn't have background methotrexate with Humira. Taltz did a bit better in that regard.

So, what I think this does is it shores up our impression that interleukin 17 inhibitors not only, quite beneficially, affect the skin and psoriasis, but also beneficially affect the various musculoskeletal domains of PSA including arthritis, enthesitis, dactylitis, and so forth.