Positive Phase II Results for GenSci's Firsekibart in Pediatric Rare Disease Published

Shanghai, China - March 17, 2026 - Changchun GeneScience Pharmaceutical Co., Ltd. ("GenSci")  recently announced the publication of positive Phase II clinical results for firsekibart, China's first approved IL-1β monoclonal antibody, in the journal Rheumatology and Therapy. The paper, titled "Efficacy and Safety of Firsekibart in Treatment of Active Systemic Juvenile Idiopathic Arthritis: A Randomized Phase 2 Study " , evaluated the therapy in children with systemic juvenile idiopathic arthritis (sJIA), a rare disease.

The multicenter trial, conducted across leading pediatric rheumatology centers in China, delivered compelling results:

Rapid and Robust Disease Control

In the firsekibart 3.0 mg/kg dose group, the proportion of participants achieving a modifed JIA ACR Pedi 30 response was highest at 94.1% at day 28. This means that within less than one month, over nine out of ten children experienced rapid and potent suppression of their inflammatory "storm".This response rate not only exceeded the other two dose groups in the study but also numerically exceeded the 82.4% response rate observed in the tocilizumab control arm.

Deep Remission Matters

The 3.0 mg/kg group also achieved a 47.1% ACR Pedi 90 response rate, representing an 11.8% absolute improvement over the control group's 35.3%. For children with rheumatic diseases, achieving such profound disease control is critical. It offers the best chance to prevent ongoing inflammation from causing irreversible joint damage and potential lifelong disability.

Reducing Reliance on Steroids

By the end of study, 75.0% of patients in the firsekibart 3.0 mg/kg group successfully discontinued or reduced their corticosteroid use, exceeding the 62.5% rate in the control group.Long-term steroid use, while suppressing inflammation, comes with a heavy cost for growing children—including stunted growth, osteoporosis, and metabolic disorders. The 75% steroid-sparing success rate means that three out of four children could avoid these debilitating side effects.

Unprecedented Safety Profile

Firsekibart demonstrated an exceptional safety record, achieving a rare "four-zero" outcome:

Zero grade ≥3 treatment-emergent adverse events (TEAEs)

Zero serious adverse events (SAEs)

Zero cases of macrophage activation syndrome (MAS) events

Zero deaths reported

Science Behind the Promise 

Firsekibart 's differentiated profile is built on its molecular design:

Potent neutralization: Exhibits 5× higher neutralizing activity against IL-1β compared to similar therapies, effectively blocking the inflammatory pathway

Extended half-life: Lower isoelectric point gives the molecule a negative charge in vivo, slowing clearance and supporting a convenient once-every-four-week dosing schedule

Fully human design: 100% human sequence eliminates immunogenicity risks associated with animal-derived components

IgG4 subtype: Built-in "effector-silent" properties minimize off-target effects while precisely locking onto the target

A Phase III trial for Firsekibart in sJIA is now underway. Beyond sJIA, the therapy is being actively developed for multiple additional indications, including connective tissue disease-associated interstitial lung disease (CTD-ILD) and endometriosis (EM), which have already received clinical trial approval.