OBJECTIVES: Membranous nephropathy (MN) is an important cause of kidney disease in adults. Idiopathic IMN is of unknown aetiology. Most patients are given a trial of therapy with renin-angiotensin system (RAS) blockade. If partial or complete remission is not achieved within 6 months’ immunomodulatory therapy is initiated. Emerging evidence suggests benefit from rituximab to treat IMN, but it is expensive.

METHODS: Prospective data were collected through an established national registry with linkage to routine data sources on mortality and hospital utilization. Costs including drug costs, hospital admissions, and dialysis were estimated according to remission status. An independent academic organisation analysed the data with multidisciplinary project support.

RESULTS:

• A total of 180 patients with IMN were included in the analysis (median age 59, 67% male). At baseline the median eGFR was 49.2mls/min and 74.5% of patients were positive for anti-phospholipase A2 receptor antibodies (marker of disease activity). 46 % of patients had achieved a complete or partial remission at 12 months and 41% at 24 months
• Multi-regression analysis showed a reduction in the rate of decline of eGFR after rituximab therapy.
• 4% of the cohort required RRT during follow up and 6% died.
• Patients without partial or complete remission incurred higher total costs than those with partial or complete remission.

CONCLUSIONS: This is the largest study cohort to date of patients treated with rituximab. The cohort was significantly different from those in published trials of rituximab in IMN (Gemritux, Ri-Cyclo and MENTOR) with worse baseline kidney function and nearly 80% having had prior immunosuppression. (i.e. this cohort had more refractory, advanced disease than those in published studies). Despite this, a beneficial effect of rituximab was demonstrated.