Izokibep Falls Short of Primary Endpoint for Hidradenitis Suppurativa Patients

Press Release

In new phase 2b/3 trial data, investigational IL-17A inhibitor izokibep did not meet its primary endpoint for patients with the chronic skin disease.

  • Acelyrin's investigational IL-17A inhibitor, izokibep, was not able to meet its primary endpoint in a phase 2b/3 study for hidradenitis suppurativa, with 39% of individiuals on once-weekly 160-mg izokibep having a 75% reduction in HiSCR75 score at the 16 week mark, compared to 29% on placebo.
  • Even on a twice-weekly dosing schedule, the investigational treatment failed to significantly differentiate itself from the placebo arm, with only 34% of participants achieving HiSCR75 at Week 16.
  • Despite these results, Acelyrin remains optimistic about izokibep's potential, citing consistent early response rates and seeks to continue the phase 3 research while acknowledging an unexpected increase in the placebo response and high discontinuation rates.

Acelyrin's investigational IL-17A inhibitor—known as izokibep—did not meet its primary endpoint in a phase 2b/3 trial for chronic skin condition hidradenitis suppurativa (HS), according to recent findings.1

The study investigators found that 39% of those treated with 160-mg izokibep once-per-week showed a 75% or more diminished HS clinical response (HiSCR75) score by 16 weeks, compared to 29% in the placebo arm of the study, with no statistically significant treatment effect.

“Although the overall study did not meet statistical significance, izokibep appears to be demonstrating consistent early and high orders of response for patients suffering from hidradenitis suppurativa without safety or tolerability limitation,” said Shao-Lee Lin, MD, PhD, CEO and founder of Acelyrin.

The twice-per-week dose of the investigational drug showed similar results to the once weekly dose, with only 34% of those in the treatment arm reaching HiSCR75 at the 16 week mark.

The new findings emerged from part B of the double-blinded Phase 2b/3 research study involving 175 participants with diagnosed moderate-to-severe HS.

The investigatyors’ primary endpoint was HiSCR75 calculated through the non-responder imputation (NRI) method, and it was negatively impacted by higher-than-normal discontinuation rates early on in the research and an unexpected increase in placebo response.

The safety characteristics of the drug remained in line with prior investigations within the anti-IL-17A class. Notably, the team found no instances of candida infections in the group given the high dose of 160mg once-per-week.

Additionally, the investigators observed 2 discontinuations which were shown to be attributable to injection site reactions, accounting for 3.5% of the total cases.

Despite the less impressive results, Acelyrin's CEO, Shao-Lee Lin, noted the consistent and early positive results observed with the investigational drug, particularly in achieving HiSCR100.

“The consistent and early achievement of HiSCR100, along with our prior izokibep experience in Psoriatic Arthritis, continues to demonstrate the potential of izokibep for resolution of disease, especially in difficult to treat tissues,” Lin said in a statement. “These results further support our ongoing evaluations of 160 mg QW dosing in HS, as well as for additional indications, including uveitis and PsA, the largest potential indication for izokibep.”

The company is continuing its phase 3 izokibep study for HS and completed an IPO in May of 2023, raising about $540 million.


  1. Acelyrin Inc. Announces Top-Line Results from Placebo-Controlled Clinical Trial of Izokibep for Moderate-to-Severe Hidradenitis Suppurativa. Biospace. September 11, 2023. Accessed September 12, 2023. https://www.biospace.com/article/releases/acelyrin-inc-announces-top-line-results-from-placebo-controlled-clinical-trial-of-izokibep-for-moderate-to-severe-hidradenitis-suppurativa/
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