CCD052, a novel small-molecule agent targeting Clostridioides difficile

Clostridioides difficile infection (CDI) remains a significant global public health challenge. CCD052, a novel bile acid analog containing an aminonitrothiazole moiety, was assessed for antibacterial activity in vitro and in vivo.

Its inhibitory effect on pyruvate:ferredoxin oxidoreductase (PFOR) was determined. Minimum inhibitory concentrations (MICs) were tested against ATCC-BAA-1870, CD630, and 115 clinical isolates. Minimum bactericidal concentrations, time-kill kinetics, post-antibiotic effects (PAEs), spore germination and sporulation, and related gene expression were determined using representative strains. Using a mouse model, the effects of CCD052 and vancomycin were compared for diarrhea, histological damage, fecal spore shedding, gut microbiota, and fecal bile acid metabolites.

CCD052 notably inhibited PFOR. All strains were highly susceptible (MIC range 0.03-0.25 mg/L). CCD052 exhibited rapid, thorough bactericidal effect within 2 hours, with PAE >20 hours at 32 × MIC. CCD052 inhibited spore germination when ≥0.06 mg/L, and may inhibit sporulation by significantly downregulating sigH, spoOA, spoIIR, and spoIIID (p < 0.05). In CCD052-treated mice, no death, no diarrhea, and no significant weight loss or colon inflammation were observed; fecal spore shedding was reduced even after medication withdrawal; Muribaculaceae, associated with reduction of C. difficile colonization, was abundant in the gut; chenodeoxycholic acid and ursodeoxycholic acid increased, while deoxycholic acid decreased, facilitating inhibition of spore germination.

CCD052 is a promising anti-C. difficile candidate with potent bactericidal activity and inhibitory effects on spore germination and sporulation. Its ability to protect mice from mortality, preserve gut microbiota, and balance bile acid metabolism supports further preclinical development.