Selection of a Respiratory Syncytial Virus Fusion Inhibitor Clinical Candidate. 2. Discovery of a Morpholinopropylaminobenzimidazole Derivative (TMC353121)

A preceding paper (Bonfanti et al. <i>J. Med Chem.</i> <b>2007</b>, <i>50</i>, 4572−4584) reported the optimization of the pharmacokinetic profile of substituted benzimidazoles by reducing their tissue retention. However, the modifications that were necessary to achieve this goal also led to a significant drop in anti-RSV activity. This paper describes a molecular modeling study followed by a lead optimization program that led to the recovery of the initial potent antiviral activity and the selection of TMC353121 as a clinical candidate.