While a peptidomimetic furin substrate, decanoyl-RVKR-chloromethylketone, has been shown to inhibit cleavage of MERS S-protein and block infection in multiple cell lines including normal human bronchial epithelial cells (NHBE), the in vivo potency of this approach is less certain (Gierer et al., 2014; Millet and Whittaker, 2014; Matsuyama et al., 2018). This evidence concerns the gene PROS1 and infection.