Complement Gene Variant Effect on Relapse of Complement-Mediated Thrombotic Microangiopathy after Eculizumab Cessation.

Eculizumab is effective for complement-mediated thrombotic microangiopathy (CM-TMA), also known as atypical hemolytic uremic syndrome. Although lifelong therapy had been suggested, discontinuation does not universally lead to relapse. Comprehensive data evaluating risk factors for recurrence following discontinuation is limited. Our aim was to systematically review available literature assessing the role of complement genetic variants in this setting. Reports on CM-TMA and eculizumab withdrawal published before January 1st, 2021 were included. Key reasons for patient exclusion were no follow-up after drug withdrawal and patients lacking complement genetic testing. Two-hundred and eighty patients from 40 publications were included. Median age was 28 years-old and 25 patients had a known history of renal transplant. Complement genetic variants were identified in 60%, most commonly in CFH (n=59) and MCP/CD46 (n=38). Of patients with a complement gene variant, 51.3% had ≥1 likely pathogenic/pathogenic variant, while the remaining had variants of uncertain significance. Overall relapse rate after therapy discontinuation was 29.6%. Relapse rate was highest among patients with CFH variants and MCP/CD46 variants in canonical splice regions. Variants of uncertain significance (p<0.001) and likely pathogenic/pathogenic variants (p<0.001) were associated with increased relapse. Presence of a renal allograft (p=0.009); decreasing age (p=0.029); and detection of variants in CFH (p<0.001), MCP/CD46 (p<0.001) or C3 (p<0.001) were all independently associated with relapse after eculizumab discontinuation. Eculizumab discontinuation is appropriate in specific patients with CM-TMA. Caution should be exerted when attempting such a strategy in patients with high risk of recurrence, including a subgroup of patients with MCP/CD46 variants.