Inhibition of effector B cells by ibrutinib in systemic sclerosis

Area of Science:

• Immunology
• Rheumatology
• Pharmacology

Background:

• Systemic Sclerosis (SSc) is a severe connective tissue disease with high morbidity and mortality, often due to organ fibrosis and pulmonary hypertension.
• Current treatments for SSc offer only symptomatic relief and disease slowing, highlighting the need for novel therapeutic strategies targeting underlying pathology.
• B cell hyperactivity and autoantibody production are implicated in SSc pathogenesis, making them potential therapeutic targets.

Purpose of the Study:

• To investigate the therapeutic potential of ibrutinib, a Bruton's tyrosine kinase (BTK) inhibitor, in modulating B cell pathology in an in vitro model of Systemic Sclerosis.
• To assess ibrutinib's effects on cytokine production, autoantibody release, and NFκB activation in SSc patient-derived B cells.

Main Methods:

• Peripheral blood mononuclear cells (PBMCs) and sorted B cells from 24 SSc patients were stimulated to induce an innate immune response.
• Functional testing evaluated the impact of ibrutinib on cytokine production (IL-6, TNF-α, IL-10), autoantibody release, and NFκB activation via flow cytometry.
• In vitro model using CpG stimulation to mimic innate immune activation in B cells.

Main Results:

• Ibrutinib significantly reduced the production of pro-fibrotic cytokines IL-6 and TNF-α from effector B cells in SSc patients.
• Low-dose ibrutinib (0.1 μM) maintained the production of the immunoregulatory cytokine IL-10 while inhibiting hyperactivated, pro-fibrotic B cells.
• Ibrutinib treatment led to significantly reduced phosphorylation of NFκB, a key transcription factor in B cell innate immune responses.

Conclusions:

• Ibrutinib demonstrates potential as a novel therapeutic agent for Systemic Sclerosis by targeting aberrant B cell activity.
• The drug's ability to reduce pro-fibrotic cytokines and NFκB activation, while preserving IL-10, suggests a favorable immunomodulatory profile for SSc.
• These findings support the clinical investigation of ibrutinib for SSc patients to address the underlying immune dysregulation contributing to disease progression.