Two different doses of the humanized monoclonal antibody ixekizumab improved signs and symptoms of active psoriatic arthritis in a phase III manufacturer-sponsored trial of patients who had not taken a biologic drug before.

The agent selectively binds and neutralizes interleukin (IL)-17A, which promotes joint inflammation and damage via several mechanisms. So the study findings support the view that IL-17A is a key cytokine in the pathogenesis of psoriatic arthritis and an appropriate therapeutic target, said Philip J. Mease, MD , of the department of rheumatology at Swedish Medical Center and the University of Washington, Seattle, and his associates.

They are performing the ongoing, 3-year, randomized, double-blind trial ( SPIRIT-P1 ) comparing responses with an 80-mg dose of ixekizumab every 2 weeks (103 patients), an 80-mg dose every 4 weeks (107 patients), a 40-mg dose of adalimumab (Humira) every 2 weeks (101 patients, active control group), and matching placebo (106 patients, placebo-control group). Each of the two ixekizumab arms received a starting dose of 160 mg given as two injections at week 0. This report presented the findings after the initial 24-week, double-blind treatment period of the trial.

The study participants are adults with active psoriatic arthritis who had never been treated with biologic agents and who continued taking their usual doses of conventional disease-modifying antirheumatic drugs, oral corticosteroids, opiates, and/or nonsteroidal anti-inflammatory drugs/Cox-2 inhibitors during the study. The mean patient age was 49.5 years. Of the 382 who completed this portion of the study, 57 showed an inadequate response and required rescue medication, including 10 on the lower dose of ixekizumab, 11 on the higher dose of ixekizumab, 9 taking adalimumab, and 27 taking placebo.

The primary efficacy endpoint, ACR20 response at week 24, was met by 62.1% of the higher-dose ixekizumab group, 57.9% of the lower-dose ixekizumab group, and 57.4% of the adalimumab group, all of which were significantly greater than the 30.2% rate in the placebo group. Both doses of the study drug as well as the active control drug also improved secondary endpoints: reducing mean levels of disease activity as measured by the 28-joint Disease Activity Score using on C-reactive protein, improving patient-reported physical function on the Health Assessment Questionnaire–Disability Index, and improving disease-related physical health as measured by the SF-36, the investigators said (Ann Rheum Dis. 2016 Aug 23. doi: 10.1136/annrheumdis-2016-209709 ).

In addition, the progression of structural joint damage, as assessed on radiographs of bone erosions and joint-space narrowing in the hands and feet, was significantly less with the three active treatments than with placebo. Among patients with the most extensive disease, a significantly greater percentage achieved Psoriasis Area and Severity Index 75 level of improvement with the three active treatments than with placebo. And among patients with nail involvement, mean improvements in Nail Psoriasis Severity Index scores were significantly higher with the three active treatments than with placebo.

Adverse effects included grade 1 and 2 neutropenia, herpes zoster involving the eyelid, gastroenteritis, esophageal candidiasis, and depression-related symptoms. All infections resolved with treatment, and none required discontinuation of the study drug.

This study was funded and sponsored by Eli Lilly, maker of ixekizumab. Dr. Mease reported receiving grants, personal fees, and other support from Eli Lilly, AbbVie, Amgen, Bristol Myers Squibb, Celgene, Crescendo, Genentech, Janssen, Pfizer, UCB Pharma, Merck, Novartis, and Corrona. His associates reported ties to numerous industry sources.


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