 Certolizumab pegol is a recombinant antigen-binding fragment antibody that is attached to a 40kDa polyethylene glycol.The addition of polyethylene glycol, or PEGylation, increases bioavailability, drug stability, and plasma half-life.It was found to have efficacy over placebo medications for 10 weeks in the treatment of moderate to severe Crohn's disease in one large trial.