#2187 Rare disease, novel approach: C3GN and Iptacopan case report

Abstract Background and Aims C3 glomerulonephritis (C3GN) is a rare disease characterised on biopsy by proliferative lesions of predominant C3 deposition on immunofluorescence, particularly deposits within the mesangium and capillary walls. Dysregulation of the alternative complement pathway is thought to be the underlying mechanism 1. There are no approved treatments for C3G and prognosis is poor, with 50% progression to kidney failure over 10 years and similar rates of transplant loss due to disease recurrence. Iptacopan (a selective Factor B complement inhibitor) is proposed to suppress key enzymes involved in the alternative pathway cascade 2. It is being studied in clinical trials of C3G 3. We sought to describe our experience in diagnosing and managing a 25-year-old with C3GN who presents with nephrotic syndrome, hypertension, and a reduction in his estimated glomerular filtration rate (eGFR) with a novel small molecule therapeutic. Method This report charts the clinical course of one male patient over 11 months from presentation with C3GN, to the introduction of immunosuppression and of Iptacopan, and the assessment of his response to the foregoing. The patient consented to the publication of his case. Results A 25-year-old male with a background of autism spectrum disorder was referred to his regional nephrology service due to reduction in his eGFR and proteinuria. His creatinine was 158 µmol/L with an eGFR was 51.8 ml/ml/1.73 m2 (CKD-EPI equation); urinary protein creatinine ratio (uPCR) 500 mg/mmol; urinary albumin creatinine ratio (uACR) 400.2 mg/mmol. Serum album 32g/L. His C3 0.22 (normal range 0.82–1.85 g/L); C4 0.27 (normal 0.15–0.53 g/L). A renal biopsy was performed which demonstrated diffuse MPGN dominant C3 staining; cholesterol crystals; and moderate to severe chronic tubulointerstitial damage. 1 mg/kg oral prednisolone with mycophenolate mofetil (MMF) titrated up to a dose of 1g twice a day was initiated. As he was established on the therapy his eGFR rose back to 57.9 ml/min over approximately 8 weeks from a nadir of 33.8 ml/min. Following initial weaning of his prednisolone dose, his eGFR dropped back down to 29.7 ml/min with a creatinine of 250 µmol/L. With involvement and clinical support from the National Renal Complement Therapeutics Centre an application was made to Novartis for the compassionate use of Iptacopan which was commenced early August 2023 (he would not have been eligible for recruitment into any current clinical trials). His latest eGFR is 47.5 ml/ml/1.73 m2 with a uACR of 9.1 mg/mmol and normal C3 and C5b-9 levels after 5 months of Iptacopan. His prednisolone dose is 10 mg. MMF continues at 2g total dose. Conclusion Iptacopan has so far resulted in the normalisation of serum C3 levels, reduction of uACR and stabilisation of serum creatinine as we have reduced the prednisolone dose.