ACELYRIN, INC. Announces Magnitude of Clinical Responses with Izokibep in Psoriatic Arthritis Continues to Improve with Longer Duration of Therapy

April 11, 2023
  • At 46 weeks, izokibep demonstrated higher levels of response across psoriatic arthritis disease manifestations
  • Long-term data build on statistically significant improvements demonstrated at 16 weeks across key measures of joint pain, skin psoriasis and enthesitis resolution
  • With longer duration of therapy, izokibep remained generally well-tolerated and safety data at week 46 were consistent with that previously observed for izokibep in psoriatic arthritis

LOS ANGELES, April 11, 2023 /PRNewswire/ -- ACELYRIN, INC., a late-stage clinical biopharma company focused on accelerating the development and delivery of transformative medicines in immunology, today announced long-term 46-week data from a global Phase 2 trial of izokibep in psoriatic arthritis (PsA). Izokibep is a small protein therapeutic designed to inhibit interleukin-17A (IL-17A) with 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 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," noted Philip J. Mease, MD, Director of Rheumatology Research at the Swedish Medical Center in Seattle, WA, Clinical Professor at the University of Washington School of Medicine and investigator in the izokibep PsA program. 

The randomized double-blind, placebo-controlled, Phase 2 clinical trial evaluated the safety and efficacy of izokibep dosed 80 mg every two weeks (Q2W) or 40 mg Q2W, versus placebo Q2W, in adult patients with active PsA. The global study assessed various endpoints including the American College of Rheumatology (ACR) response, the Psoriasis Area and Severity Index (PASI) score and the Leeds Enthesitis Index (LEI). At Week 16, the placebo cohort transitioned to 80 mg izokibep Q2W and the trial treatment period continued for up to 46 weeks.

Response Endpoint

Izokibep 80 mg Q2W,

as observed at 46 weeks

Izokibep 40 mg Q2W,

as observed at 46 weeks

Izokibep Pbo to 80 mg Q2W,

as observed at 46 weeks


79 %

50 %

73 %


50 %

33 %

64 %


71 %

50 %

67 %

Enthesitis Resolution

89 %

83 %

80 %

ACR50 response is defined as a 50% improvement in tender and swollen joints, along with improvement in three of these five parameters: (a) patient global assessment of disease activity; (b) physician global assessment of disease activity; (c) patient pain scale; (d) disability/functional questionnaire and (e) decreased concentration of C-reactive protein correlated to inflammation. ACR70 response is defined as a 70% improvement in features noted above for ACR50 response, and is considered by some clinicians to be an indicator of significant control of disease activity. PASI100 response is defined as 100% improvement in skin response, or complete resolution of psoriasis skin lesions. Enthesitis resolution is defined as no active entheseal sites on the Leeds Enthesitis Index (LEI).

"We hypothesized that the high potency and small molecular size of izokibep has the potential to impact clinical response," said Shao-Lee Lin, MD, PhD, founder and CEO, ACELYRIN. "It has been heartwarming to see the encouraging results in both the hidradenitis suppurativa data recently presented at AAD as well as independently within the PsA dataset, not only at 16 weeks, but now with increased rates of response in PsA with continued long-term dosing out to 46 weeks."

Through week 46 of this Phase 2 trial, izokibep was generally well-tolerated – in line with previous trials of izokibep. The most common adverse event (AE) was injection site reactions. Injection site reactions were localized reactions, with the majority graded mild-to-moderate in severity, 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, we observed one serious adverse event (vulvar cancer) which was determined to be potentially drug-related.

The full 46-week data from this trial will be presented at a future scientific meeting.

As a result of the Phase 2 data at 16 weeks, ACELYRIN accelerated into 2022 the initiation of a Phase 2b/3 trial in PsA – which is currently ongoing – evaluating a range of doses, including significantly higher doses than the Phase 2 trial that could potentially result in better ACR, PASI and enthesitis resolution responses.

About Izokibep
Izokibep is a small protein therapeutic designed to inhibit interleukin-17A (IL-17A) with high potency and the potential for robust tissue penetration due to its small molecular size, about one-tenth the size of a monoclonal antibody. Izokibep has been administered across numerous clinical trials for multiple immunological indications including hidradenitis suppurativa (HS), psoriatic arthritis (PsA), axial spondyloarthritis (AxSpA) and uveitis to more than 400 participants, including at doses up to 160 mg, and in some for up to three years.

ACELYRIN, INC. is a Los Angeles area-based late-stage clinical biopharmaceutical company – with additional operations in the San Francisco Bay area – focused on providing patients life-changing new treatment options by identifying, acquiring, and accelerating development and commercialization of promising drug candidates. For more information, please visit

Forward Looking Statements
Some statements in this press release are, or may be considered,  forward-looking statements, including statements regarding ACELYRIN's progress, business plans and clinical trials, presentation of our data at future meetings, as well as the potential future benefits of our product candidates. While ACELYRIN, INC. considers any projections to be based on reasonable assumptions, these forward-looking statements are subject to risks and uncertainties that may cause actual results to differ materially from those anticipated in such forward-looking statements.