To probe experimentally the cause of any CYP-mediated metabolic liability in the promising benzofuran, this compound was screened with a PolyCYPs enzyme panel kit (provided by Hypha Discovery) that identified one main monohydroxylated metabolite. This matched the monohydroxylated metabolite observed in human liver S9 incubations in the presence of NADPH cofactor-generating system; human liver S9 incubations performed in the presence of UDP-GA cofactor resulted in samples containing a directly-conjugated glucuronide metabolite, the structure of which was not determined. (Supplementary Information -Biology). Following a scaleup reaction with one of the PolyCYP enzymes, it was possible to identify the main hydroxylated metabolite (997, Figure ) resulting from oxidation on the unsaturated core at the 7-position (Supplementary Information -Chemistry). This metabolite was found to be inactive when evaluated vs. MRSA. The metabolic liability identified for the benzofuran may not be responsible for the intrinsic clearance data obtained, since compounds with such a motif displayed similar intrinsic clearance to analogous compounds with a fully aromatic core (e.g., 865 vs 1018). Several compounds displayed low microsomal intrinsic clearance (e.g., HLM CLint < 3 ug/min/mg protein for 837, 838 and 974) in tandem with good solubility, but these compounds were not potent. The fully aromatic (imidazopyridine 1018) vs partially aromatic (diarylimidazole 865) cores performed approximately equivalently. The introduction of the nitrogen linker between rings did not have the expected impact on compound solubility (e.g., 859 vs 982, 982 and 983).