Nipocalimab, a monoclonal antibody targeting immunoglobulin G (IgG), has shown promising results in a Phase II trial for primary Sjögren's syndrome. The study, presented at the American College of Rheumatology's annual meeting, indicates that nipocalimab could offer a novel approach to treating this autoimmune disease.
Targeting IgG in Sjögren's Syndrome
Sjögren's syndrome is characterized by excessive IgG release and anti-IgG autoantibodies, leading to manifestations in multiple organ systems. Nipocalimab works by binding to FcRn, a neonatal receptor protein, preventing the recycling of IgG antibodies and reducing their levels in circulation. This mechanism aims to interrupt the underlying disease process.
Phase II Trial Results
The Phase II trial involved 163 patients who were randomized to receive either high-dose nipocalimab (15 mg/kg), low-dose nipocalimab (5 mg/kg), or placebo every two weeks for 24 weeks. The primary outcome measure was the change in clinical ESSDAI (EULAR Sjögren's Syndrome Disease Activity Index) score, modified to exclude the IgG component, making the assessment more stringent.
Results showed that the high-dose nipocalimab group experienced a significant reduction in clinical ESSDAI scores compared to placebo (-6.40 points vs. -3.74 points, P = 0.002). The drug also had a notable impact on IgG levels, with average titers dropping by 50% by week 2 and an additional 10% by week 8 in the high-dose group. These levels rebounded by week 30.
Additional Outcome Measures
In addition to the primary outcome, several secondary endpoints also favored the 15-mg/kg dose of nipocalimab:
- Physician's Global Assessment (PhGA): -14.50 points (P < 0.001)
- ESSDAI (with IgG included): -1.79 points (P = 0.012)
- STAR responder rate: +23.7 percentage points (P = 0.017)
- CRESS responder rate: +30.3 percentage points (P = 0.001)
Notably, the lower dose of nipocalimab did not demonstrate statistically significant superiority over placebo in any of the efficacy evaluations.
Safety Profile
Adverse events were more common in the nipocalimab groups (approximately 80%) compared to placebo (63%), with infections being the primary difference. Infections were observed in 60% of the low-dose and 52% of the high-dose groups, versus 43% of the placebo group. There were also more cases of latent virus activation (presumably herpes zoster) in the nipocalimab groups. Infusion and hypersensitivity reactions were also more frequent with the active agent.
Future Directions
Janssen, the developer of nipocalimab, is planning a longer Phase III study to further assess the drug's efficacy and safety in Sjögren's syndrome. The company also sees potential applications for nipocalimab in other autoimmune diseases, including lupus, rheumatoid arthritis, and several rare conditions.
Iscalimab Shows Promise as well
Iscalimab, an anti-CD40 antibody from Novartis, has also shown promise in treating Sjögren's disease. A Phase 2b trial revealed improvements in clinician-reported disease activity and patient-reported dryness and fatigue. The trial included two cohorts: one with moderate to severe systemic activity and high symptom burden, and another with high symptom burden but lower systemic involvement. While the 150 mg and 600 mg doses showed significant results in the first cohort, symptom improvement was observed across all three dosage groups. In the second cohort, there was an overall trend toward symptom relief, particularly for dryness and fatigue, though these changes were also nonsignificant.
Competition in the FcRn Target Space
Nipocalimab is not the only drug targeting FcRn. Efgartigimod (Vyvgart), a synthetic antibody fragment, is already approved for myasthenia gravis and has completed a Phase II trial in Sjögren's syndrome, with plans for a Phase III study. Dazodalibep, which targets the CD40 ligand, has also shown encouraging results in improving patient-reported symptoms.
