After crushing loss last year, Acelyrin rebounds with psoriatic arthritis victory

Acelyrin’s lead asset, izokibep, outperformed placebo as a treatment for psoriatic arthritis in a phase 2b/3 trial, rebounding from a previous clinical loss that crunched the company’s value. 

The biotech says izokibep notched a statistically significant improvement in the skin condition compared to placebo at week 16, according to Monday’s announcement. The primary endpoint was ARC50, encompassing patients who recorded a 50% improvement in symptoms. Acelyrin also said that 160 mg of izokibep given weekly or every other week “showed improved magnitude of responses” on additional symptom endpoints tracking 70% and 100% improvement, and minimal disease activity compared to 80 mg given every other week. 

Less than 3% of patients discontinued the study with Acelyrin saying the drug has a favorable safety profile. CEO Shao-Lee Lin, M.D., Ph.D., said in a release that the data validate the profile of the 160 mg dose and give the company “conviction” in its efficacy and safety profile. 

“We have observed from the phase 2 46-week data that there is no safety limitation to long-term treatment with izokibep and that longer duration of therapy demonstrated the potential for even further improvements over time,” said Philip Mease, M.D., in a release, director of rheumatology research at the Swedish Medical Center in Seattle and an investigator for the trial. 

Acelyrin’s shares rose just under 7% to $7.99 shortly after the markets opened Monday morning. The results were a much-needed win after izokibep failed in a phase 2b/3 test for patients with hidradenitis suppurativa (HS). That September disclosure sent the company’s share price nosediving, and it has yet to recover. 

Two months later, in late November 2023, Acelyrin said its contract research organization, Fortrea, had slipped up on the dosing schedule in the psoriatic arthritis trial, prompting a full look at the izokibep program, including the hidradenitis suppurativa study. The company vowed to not use Fortrea for any future trials. 

Acelyrin did have a glimmer of hope to share on the HS trial Monday, reporting 32-week follow-up data from the phase 2b portion that indicated continued izokibep use “was associated with further clinical improvements over time.” Acelyrin says the majority of treated patients achieved at least a 75% reduction in symptoms, though it’s unclear how that compares to placebo over the same period. 

Izokibep is Acelyrin’s main clinical bet, with four mid- to late-stage programs across immunology. The therapy helped propel the company to a $540 million IPO in 2023, one of just a handful of biotechs that made it onto the public market last year. As of the end of September 2023, Acelyrin had nearly $790 million in available cash.