Table 1.

Clinically tested antibody-mediated therapeutic agents for CDI.

Agent	Manufacturer	Type of antibody	Mode of action	State of development	Indication
SYSTEMIC APPLICATION ROUTE
Actoxumab	Merck Sharp & Dohme Ltd (Europe), Inc.	Antitoxin A (CDA1, MK-3415) human monoclonal IgG antibody	Prevents binding to a cognate receptor	Terminated after phase III trial	None
Bezlotoxumab	Merck Sharp & Dohme Ltd (Europe), Inc.	Antitoxin B (CDB1, MDX-1388, MK-6072) human monoclonal IgG antibody	Prevents binding to a cognate receptor	FDA and EMA approved	rCDI
IVIG	Various	Human IgG	Neutralization of TcdA/TcdB	Market (for other indications)	rCDI/CDI/severe CDI
ORAL APPLICATION ROUTE
IgAbulin	ImmunoAG Vienna/Baxter	Human IgA	Neutralization of TcdA/TcdB	Market (for other indications)	CDI
Oral hyperimmune bovine immunoglobulin concentrate (BIC)	Beth Israel Deaconess Medical Center	Polyclonal antibody-enriched colostral immune whey protein concentrate	Neutralization of TcdA/TcdB	Clinical phase I	CDI
MucoMilk	MucoVax BV	Polyclonal antibody-enriched milk immune whey protein concentrate	Neutralization of TcdA/TcdB, Binding of vegetative bacterial cells	Clinical development	rCDI
Cediff	Novatreat Ltd.	Polyclonal antibody-enriched colostral immune whey protein concentrate	Binding of toxigenic vegetative bacterial cells	Interrupted in clinical phase II	rCDI
IMM-529	Immuron Ltd.	Immune colostrum concentrate	Neutralization of TcdB, Binding of vegetative bacterial cells and endospores	Clinical phase I/II	CDI/rCDI

IVIG, intravenous immunoglobulin; TcdA, C. difficile toxin A; TcdB, C. difficile toxin B; CDI, C. difficile disease; rCDI, recurrent CDI.