#425 Felzartamab (anti-CD38) in patients with IgA Nephropathy—interim results from the IGNAZ study

Abstract Background and Aims Most patients with IgA nephropathy (IgAN) will progress to kidney failure within 10-15 years of diagnosis. Sustained proteinuria is the best predictor of adverse long-term kidney outcomes and is a surrogate marker for efficacy. CD38+ plasma cells are likely the main source of pathogenic Gd-IgA1, and the related autoantibodies in IgAN. Felzartamab (felza; HIB202) is a recombinant purified human immunoglobulin G1 (IgG1) monoclonal antibody (mAb) that binds to CD38 on plasma cells and is being studied across immune-mediated kidney diseases such as IgAN, Primary Membranous Nephropathy, Lupus Nephritis, and Antibody Mediated Rejection. The primary aims of the IGNAZ study were to assess: 1) efficacy of felza compared to placebo on urine protein:creatinine ratio (UPCR) and estimated glomerular filtration rate (eGFR) change from baseline, and 2) the relationship between exposure, safety, and efficacy in each of 3 dose groups vs. placebo. Interim results with 15 months of follow-up from this 24-month trial are presented. Method In Part 1, 48 IgAN subjects were randomized in a 1:1:1:1 ratio across a placebo and 3 active arms in this multicenter, double-blind placebo-controlled, phase IIa trial. The M1, M2, and M3 active arms received 2 doses in 15 days, 5 doses in 2 months, and 9 doses in 5 months, respectively. In Part 2, 6 Japanese subjects received the M3 regimen, open-label, and have been followed for 9 months. Key inclusion criteria included ages 18-80 years, biopsy confirmed diagnosis of IgAN within the past 8 years, proteinuria at screening ≥1.0 g/d, eGFR ≥30 ml/min/1.73 m2 (by CKD-EPI), and background stable and maximally tolerated renin angiotensin system inhibitors. Results 48 randomized subjects were enrolled at 28 sites in the US and in 14 different countries in Europe and in Asia, of which 46 completed the treatment phase. Mean (SD) baseline characteristics (Parts 1 and 2 combined): age 41.6 (12.3) yrs, UPCR 1.67 (1.0) g/g, eGFR 74.6 (30.3) ml/min/1.73 m2. 67% of subjects were male. Intention-to-treat with felza demonstrated rapid, clinically meaningful reductions in UPCR with the maximal treatment effect being observed in the M3 9-dose regimen. In Part 1, percentage change from baseline in UPCR was −14% for placebo and −25% for M3 9-dose arm at month 3, and +9% for placebo and −35% for M3 at month 6 (Fig. A). Reductions in proteinuria observed at month 6 persisted until Month 15, 10 months after the last dose: +6% and −38% mean UPCR change from baseline for placebo and the M3 9-dose arm, respectively (Fig. B). Relatively stable eGFR values were observed for the felza arms compared to loss of eGFR in the placebo arm. Rapid, durable reductions in IgA and Gd-IgA1 levels were seen across the dosing arms, with reductions lasting 10 months after the last dose (Fig. C). IgG recovery occurred faster off-treatment than IgA. Results in the Part 2 subjects were similar to the Part 1 M3 cohort through 9 months. There were no apparent dose-dependent adverse events and no exposure-safety relationship. Treatment-emergent adverse events (TEAEs) were generally of mild or moderate intensity or toxicity grade. The most common TEAE assessed as related by study investigator was infusion related reactions (IRR), most of which occurred on the first infusion. There was one treatment-related serious AE due to an IRR. Five subjects discontinued treatment due to IRRs or drug hypersensitivity; for four of the five subjects, the infusion rate was higher than protocol-specified or had an error in pre-medication. TEAE infections were comparable between placebo and felza arms: Placebo (33.3%), M1 (33.3%), M2 (36.4%), M3 (38.5%), Part 2 (50.0%); all were Grades 1 or 2, and non-serious. Conclusion This proof-of-concept study highlights the potential for disease modification in IgAN with the anti-CD38 mAb felza and supports continued research as a potential treatment for high-risk IgAN patients. Felza treatment resulted in clinically meaningful, prolonged UPCR reductions and eGFR stabilization sustained ≥10 months after dosing was completed. Felza was generally well tolerated with rapid recovery of IgG with durable reductions in IgA and pathogenic Gd-IgA1 levels.

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