The antiviral effects of RSV fusion inhibitor, MDT ‐637, on clinical isolates, vs its achievable concentrations in the human respiratory tract and comparison to ribavirin

BackgroundRespiratory syncytial virus (RSV) viral load and disease severity associate, and the timing of viral load and disease run in parallel. An antiviral must be broadly effective against the natural spectrum of RSV genotypes and must attain concentrations capable of inhibiting viral replication within the human respiratory tract. ObjectivesWe evaluated a novel RSV fusion inhibitor, MDT‐637, and compared it with ribavirin for therapeutic effect in vitro to identify relative therapeutic doses achievable in humans. MethodMDT‐637 and ribavirin were co‐incubated with RSV in HEp‐2 cells. Quantitative PCR assessed viral concentrations; 50% inhibitory concentrations (IC50) were compared to achievable human MDT‐637 and ribavirin peak and trough concentrations. Results and conclusionsThe IC50 for MDT‐637 and ribavirin (against RSV‐A Long) was 1.42 and 16 973 ng/mL, respectively. The ratio of achievable peak respiratory secretion concentration to IC50 was 6041‐fold for MDT‐637 and 25‐fold for aerosolized ribavirin. The ratio of trough concentration to IC50 was 1481‐fold for MDT‐637 and 3.29‐fold for aerosolized ribavirin. Maximal peak and trough levels of oral or intravenous ribavirin were significantly lower than their IC50s. We also measured MDT‐637 IC50s in 3 lab strains and 4 clinical strains. The IC50s ranged from 0.36 to 3.4 ng/mL. Achievable human MDT‐637 concentrations in respiratory secretions exceed the IC50s by factors from hundreds to th...
Source: Influenza and Other Respiratory Viruses - Category: Virology Authors: Tags: ORIGINAL ARTICLE Source Type: research