#145 Subgroup and secondary endpoint evaluation of a phase 2 randomized placebo-controlled trial of ravulizumab in IgA nephropathy

Abstract Background and Aims The pathogenesis of IgA nephropathy (IgAN) involves immune complex deposition and activation of the complement system, causing formation of the terminal pathway components C5a and C5b-9, leading to inflammation and glomerular damage. Elevated levels of activated C3 in plasma are associated with proteinuria and renal function decline in patients with IgAN [1]; mesangial C3 deposition is also associated with progression of disease [2]. Ravulizumab is a humanized monoclonal antibody that immediately and completely inhibits complement component C5. Primary endpoint (week 26) data from the phase 2 randomized controlled trial (RCT) (NCT04564339) were previously reported and demonstrated a 30% and 33% treatment effect of ravulizumab compared to placebo on 24-hour urine protein and 24-hour urine protein-to-creatinine ratio (UPCR) reduction, respectively [3]. This analysis reports prespecified subgroup and secondary endpoints as well as post hoc exploration of treatment response by baseline serum C3 and C4 quartiles through week 26. Method The SANCTUARY RCT evaluated ravulizumab (IV; weight-based dosing Q8W) vs placebo in adults with primary IgA nephropathy. Randomized patients (2:1) were stratified by mean proteinuria (1–2 vs >2 g/day). Patients (18–75 years) with biopsy-confirmed IgA nephropathy, proteinuria ≥1g/day, estimated glomerular filtration rate (eGFR) ≥30 mL/min/1.73 m2, and on stable maximally tolerated renin angiotensin inhibition were enrolled. The primary endpoint was proteinuria reduction at week 26 based on 24-hour urine collection. Secondary endpoints at week 26 included the proportion of patients with >50% reduction in proteinuria (absolute urine protein) and the percentage with <1g/day proteinuria. The percentage change in proteinuria (absolute urine protein) among subgroups of sex, race, duration of disease, baseline proteinuria and eGFR, and baseline serum C3 and C4 levels were also evaluated, as were safety data. Results 66 patients entered the 26-week initial evaluation period (n = 43, ravulizumab arm; n = 23, placebo arm); 71.2% were White and 21.2% were Asian. Overall, 41.5% and 18.2% of ravulizumab- and placebo-treated patients, respectively, achieved >50% proteinuria reduction (Fig. 1). Proteinuria reduction to <1g/day was achieved in 26.8% and 18.2% in the ravulizumab and placebo arms, respectively. Subgroup analysis indicated a treatment effect across subgroups of sex, race, disease duration, and baseline proteinuria and eGFR (Fig. 2). With ravulizumab, there were reductions of 41.9% and 41.0% in proteinuria for those with the lowest quartile of baseline serum C3 and C4, respectively. Similarly, reductions of 40.4% and 40.8% were observed in those with baseline serum C3 and C4 levels above the lowest quartile. In the ravulizumab arm, two patients had low serum C3 at baseline and there were no patients with low serum C4 at baseline; there was no change in mean serum C3 and C4 levels over time. Treatment with ravulizumab was well-tolerated. Conclusion In this phase 2 trial of ravulizumab in IgAN, proteinuria was significantly reduced with ravulizumab vs placebo through week 26. A reduction in proteinuria was also observed across subgroups of patients. As is typical in IgAN, serum C3 and C4 levels at baseline were normal, and there was no difference in proteinuria reduction by baseline serum C3 and C4 levels with ravulizumab through 6 months.