SEISMIC: a multistakeholder summit addressing access issues in diagnosis and treatment of C3G nephropathy and IC-MPGN.

C3 glomerulopathy (C3G)-primary immune complex membranoproliferative glomerulonephritis (IC-MPGN) is an ultrarare disease spectrum associated with a significant health burden and for which there is a huge unmet need for safe and effective treatment. The underlying pathophysiology is dysregulation and overactivation of the alternative complement pathway. Two new therapeutic agents, iptacoplan and pegcetacoplan, that target proximal steps in the cascade, have demonstrated to be effective and have been approved for use in patients with C3G alone and with C3G/IC-MPGN, respectively. A key challenge to the nephrology community is how to incorporate these disease-modifying drugs into clinical practice in a timely and equitable manner. This report summarizes the deliberations and recommendations that emerged from the Addressing Access Issues in Diagnosis and Treatment of C3G Nephropathy and IC-MPGN (SEISMIC) summit in July 2025. The meeting assembled a broad panel of experts and patients and addressed the following 3 aims: (i) define issues in proper and timely diagnosis of this complex disease spectrum, (ii) assess management strategies in light of the availability of this new class of therapeutic agents, and (iii) identify barriers to access to care and treatment with these new therapeutic agents and design strategies to surmount them.