Genetic Association Reveals Protection against Recurrence of Clostridium difficile Infection with Bezlotoxumab Treatment

Abstract

Bezlotoxumab is a human monoclonal antibody against Clostridium difficile toxin B, indicated to prevent recurrence of C. difficile infection (rCDI) in high-risk adults receiving antibacterial treatment for CDI. An exploratory genome-wide association study investigated whether human genetic variation influences bezlotoxumab response. DNA from 704 participants who achieved initial clinical cure in the phase 3 MODIFY I/II trials was genotyped. Single nucleotide polymorphisms (SNPs) and human leukocyte antigen (HLA) imputation were performed using IMPUTE2 and HIBAG, respectively. A joint test of genotype and genotype-by-treatment interaction in a logistic regression model was used to screen genetic variants associated with response to bezlotoxumab. The SNP rs2516513 and the HLA alleles HLA-DRB1*07:01 and HLA-DQA1*02:01, located in the extended major histocompatibility complex on chromosome 6, were associated with the reduction of rCDI in bezlotoxumab-treated participants. Carriage of a minor allele (homozygous or heterozygous) at any of the identified loci was related to a larger difference in the proportion of participants experiencing rCDI versus placebo; the effect was most prominent in the subgroup at high baseline risk for rCDI. Genotypes associated with an improved bezlotoxumab response showed no association with rCDI in the placebo cohort. These data suggest that a host-driven, immunological mechanism may impact bezlotoxumab response. Trial registration numbers are as follows: NCT01241552 (MODIFY I) and NCT01513239 (MODIFY II).IMPORTANCEClostridium difficile infection is associated with significant clinical morbidity and mortality; antibacterial treatments are effective, but recurrence of C. difficile infection is common. In this genome-wide association study, we explored whether host genetic variability affected treatment responses to bezlotoxumab, a human monoclonal antibody that binds C. difficile toxin B and is indicated for the prevention of recurrent C. difficile infection. Using data from the MODIFY I/II phase 3 clinical trials, we identified three genetic variants associated with reduced rates of C. difficile infection recurrence in bezlotoxumab-treated participants. The effects were most pronounced in participants at high risk of C. difficile infection recurrence. All three variants are located in the extended major histocompatibility complex on chromosome 6, suggesting the involvement of a host-driven immunological mechanism in the prevention of C. difficile infection recurrence.

Keywords: Clostridium difficile; antibacterials; bezlotoxumab; genomics.

Copyright © 2020 Shen et al.

Figures

FIG 1

Manhattan plot (A) and QQ plot (B) showing the significance of SNP rs2516513 associated with drug-induced reduction on rCDI in the GWAS analysis (placebo arm versus bezlotoxumab and bezlotoxumab + actoxumab arms). λGC is 1.06 in the QQ plot. Open triangles represent the assayed SNPs; solid symbols represent the imputed SNPs. The dotted line is the genome-wide significance P value threshold of 5 × 10−08. GWAS, genome-wide association study; rCDI, recurrent Clostridium difficile infection; SNP, single nucleotide polymorphism.

FIG 2

Regional association plot of 500 kb on each side of the rs2516513 SNP before (A) and after (B) conditioning. SNP, single nucleotide polymorphism.

FIG 3

Proportion of participants with rCDI stratified by genotype and risk category. (A) rs2516513 genotype. (B) HLA-DRB1*07:01 genotype. The high-risk subgroup included participants with one or more of the following factors: prior episode of CDI in the past 6 months, severe CDI at baseline (per Zar score [37]), age of ≥65 years, CDI due to a hypervirulent strain (027, 078, or 244 ribotypes), immunocompromised, or receiving concomitant systemic antibiotics. Participants at low risk of rCDI were those with none of the above risk factors. P values were calculated from two-sided Fisher’s exact tests. BEZ, bezlotoxumab; CDI, Clostridium difficile infection; HLA, human leukocyte antigen; PBO, placebo; rCDI, recurrent Clostridium difficile infection.

FIG 4

CDI recurrence stratified by genotypes and rCDI risk categories: rs2516513 genotype (A) and HLA-DRB1*07:01 genotype (B). The high-risk subgroup included participants with one or more of the following factors: prior episode of CDI in the past 6 months, severe CDI at baseline (per Zar score [37]), age of ≥65 years, CDI due to a hypervirulent strain (027, 078, or 244 ribotypes), immunocompromised, or receiving concomitant systemic antibiotics. Participants at low risk of rCDI were those with none of the above risk factors. BEZ, bezlotoxumab; CDI, Clostridium difficile infection; CI, confidence interval; PBO, placebo; rCDI, recurrent Clostridium difficile infection.