JJP Biologics Doses the First Patients in Phase 1b Clinical Trial of Nebaprubart in Rheumatoid Arthritis (RA)

• Expansion of nebaprubart (JJP-1212) into RA follows positive interim data from its ongoing Phase 1b trial in linear IgA dermatosis (LAD), marking the second indication for the Company’s lead asset and expanding clinical validation of the IgA/CD89 pathway
  
  

Warsaw, Poland – October 19, 2026 – JJP Biologics, ("JJPBio" or the "Company") a clinical-stage, immune-focused biotechnology company advancing first-in-class therapies for immune-mediated diseases and cancer, today announces that the first patients have been dosed in its Phase 1b trial of nebaprubart, an investigational potential first-in-class anti-CD89 antagonist, for the treatment of seropositive rheumatoid arthritis.

Rheumatoid arthritis is a chronic autoimmune disorder affecting approximately 18 million people worldwide, characterized by persistent joint inflammation, pain, and stiffness that can lead to severe and irreversible structural damage and functional impairment if untreated. Biological disease-modifying antirheumatic drugs are widely used, but a substantial proportion of patients do not respond adequately, lose response over time or experience treatment-limiting side effects.

A growing body of evidence indicates that IgA autoantibodies contribute directly to RA pathogenesis and correlate with a more severe phenotype and poorer clinical outcomes via activation of the CD89 receptor on effector cells¹. However, current biologic therapies primarily target downstream inflammatory cytokines or IgG-driven pathways, leaving the IgA/CD89 axis largely unaddressed despite its important mechanistic role in pathology and disease progression.

Nebaprubart is an investigational monoclonal antibody designed to selectively block CD89 – the primary receptor on myeloid cells that is activated during binding to IgA. The Phase 1b open-label trial will evaluate the safety and tolerability of nebaprubart, as well as pharmacokinetic and immunogenicity profiles in patients with rheumatoid arthritis, while exploring potential impact on disease activity and patient-reported outcomes.

Paweł Szczepański, Chief Executive Officer of JJP Biologics, said: “Dosing the first rheumatoid arthritis patients with nebaprubart marks significant progress as we expand the clinical evaluation of our first-in-class anti-CD89 antagonist therapy into a second immune-driven indication. Despite significant advances in treatments, many patients with rheumatoid arthritis continue to experience inadequate disease control, highlighting the need for new therapeutic approaches.”

By preventing pathogenic IgA signaling through CD89, nebaprubart is intended to inhibit immune complex-driven activation of neutrophils and other myeloid effector cells that drive synovial inflammation, cartilage degradation, and progressive articular destruction in rheumatoid arthritis. At the same time, it preserves the physiological functions of IgA that are important for mucosal homeostasis, protection and immunity. Unlike approaches based on immune-cell depletion or immunoglobulin depletion, CD89 antagonism is fully reversible and does not reduce circulating IgA levels.

Sohail Ahmed, Chief Medical Officer of JJP Biologics, added: “The IgA/CD89 pathway is a highly differentiated and scientifically compelling target with the potential to deliver meaningful benefits for the substantial proportion of patients with rheumatoid arthritis who remain inadequately served by existing therapies.”

Dr. Robert Rupiński, MD, Consultant at Rheuma Medicus Specialist Center for Rheumatology and Osteoporosis, stated: “Approximately 30 to 40% of patients with rheumatoid arthritis fail to achieve an adequate response to therapy, while many others lose response over time or experience side effects that limit long-term treatment. There remains a clear need for new therapeutic approaches with the potential to achieve disease remission with sustained suppression of the underlying inflammatory process, so it is encouraging to see a novel modality being investigated.”

Further details of the Phase 1b trial can be found on the EU Clinical Trials Information System (CTIS) under EU Trial Number 2023-508661-33-00.

The first patient dosing in RA follows positive interim Phase 1b data in patients diagnosed with LAD, a rare autoantibody-mediated skin disease, which were announced in June 2026.

¹ van Delft MAM, Cegiel A, van Egmond M, and Boon L. Biomarker understanding first lessons from drug development for IgA-driven autoimmune and fibrotic diseases. Cambridge Prisms: Precision Medicine. 2025. 10.1017/pcm.2025.10005.

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About JJP Biologics (JJPBio)

JJP Biologics is a clinical-stage biotechnology company that leverages its in-depth understanding of immune pathway science in autoimmune diseases and cancer. Starting from deep mechanistic insights, JJPBio engineers antibodies that are built-to-order, designed to restore immune balance and deliver better disease control for patients with significant unmet need, because we believe that we can do better for patients.

JJPBio is the first company to generate clinical validation of the IgA/CD89 axis, establishing first-mover advantage in a disease area with broad implications across multiple autoimmune conditions, including IgA nephropathy, rheumatoid arthritis, and lupus. Our immuno-oncology program targets the CD270/HVEM checkpoint pathway in cancer.

Backed by the long-term, socially responsible capital of the Starak family and the operational infrastructure of the Polpharma Group, JJPBio operates with the scientific freedom and financial stability to pursue mechanisms others simply cannot.

JJP Biologics: We restore. We don't deplete. We work smarter.

About nebaprubart (JJP-1212)

Nebaprubart is a first-in-class IgG4-κ CD89 antagonist that is being developed to treat a wide range of autoimmune, inflammatory, and fibrotic diseases where IgA antibodies are known to have significant pathogenic involvement (e.g., rheumatoid arthritis, systemic lupus erythematosus, idiopathic pulmonary fibrosis, dermatitis herpetiformis, inflammatory bowel disease, IgA nephropathy, and IgA vasculitis). Nebaprubart was designated an Orphan Medicinal Product in October 2022 by the European Commission for the treatment of Linear IgA Disease. An open-label Phase 1b trial with nebaprubart for this indication is ongoing.