out to 46 weeks, according to an announcement reporting some of the long-term data by the drug’s developer, Acelyrin.
Izokibep is an antibody mimetic designed to inhibit IL-17A that the company says has “high potency and the potential for robust tissue penetration due to its small molecular size, about one-tenth the size of a monoclonal antibody.”
“Patients want both rapid and meaningful improvement of their symptoms, as well as lasting – and ideally improving – resolution of disease over time. Building on the 16-week data for izokibep reported at EULAR and ACR [American College of Rheumatology] last year, the 46-week data now show not only continued but marked improvements over time in key areas of psoriatic arthritis including joint pain, skin psoriasis, and enthesitis,” Philip J. Mease, MD, director of rheumatology research at the Swedish Medical Center and clinical professor at the University of Washington, both in Seattle, and an investigator in the izokibep PsA program, said in the announcement.
The phase 2 trial tested two doses of izokibep – 40 mg and 80 mg – given by subcutaneous injection every 2 weeks – against placebo in 135 adult patients with active PsA. For inclusion in the trial, patients had to have at least three swollen and at least three tender joints and an inadequate response to prior therapy including NSAIDs, conventional synthetic disease-modifying antirheumatic drugs, or tumor necrosis factor inhibitors. At week 16, the placebo group transitioned to 80 mg izokibep every 2 weeks and the trial treatment period continued for up to 46 weeks.
The trial’s primary endpoint of a 50% or higher level of improvement in ACR response criteria (ACR 50) was achieved by 48% of those on the 40 mg dose at week 16 and by 50% at week 46. For the 80-mg group, this rate rose from 52% to 79%. In the group that went from placebo to 80 mg, the ACR 50 rose from 13% with placebo to 73% with izokibep at week 46.
Resolution of enthesitis, measured by the Leeds Enthesitis Index, among those on the 40 mg dose, was achieved by 63% at week 16 and 83% at week 46, and among those on the 80 mg dose, 88% at week 16 and 89% at week 46. Those on placebo who switched to 80 mg of izokibep at week 16 had an 80% rate of enthesitis resolution at week 46.
Total resolution of skin involvement – 100% clearance of psoriasis based on the Psoriasis Area Severity Index (PASI) – was observed at 46 weeks in 50% of those on 40 mg, 71% of those on 80 mg, and 67% of those on 80 mg after week 16.
In its announcement, Acelyrin did not report withdrawal rates from the study after 16 weeks and through 46 weeks, although the statement said that izokibep “was generally well tolerated through 46 weeks, which is in line with previous trials of izokibep.” The most common adverse event was localized injection site reactions, with the majority graded mild to moderate in severity. They were generally the size of a quarter to half-dollar, and typically presented within the first few injections, after which they declined in incidence. In the trial, a case of vulvar cancer was determined to be potentially drug related, the company said.
Acelyrin is currently conducting a phase 2b/3 trial in PsA evaluating a range of doses, including significantly higher doses than in the phase 2 trial, that the company said “could potentially result in better ACR, PASI, and enthesitis resolution responses.”
The drug has been tested at doses up to 160 mg, in some cases for up to 3 years, in more than 400 patients with psoriasis, spondyloarthritis, noninfective uveitis, and hidradenitis suppurativa.
The full 46-week data from this trial will be presented at a future scientific meeting, according to the company.