Provided herein is technology relating to antimicrobial compounds and particularly, but not exclusively, to analogs of rifalazil having increased inhibition of RNA polymerase and decreased induction of human cy-tochrome P450. The compounds have an increased affinity for a bacterial RNA polymerase (e.g., a MTB RNA polymerase) and a decreased affinity for a human pregnane X receptor. Thus, in some embodiments, the steric clash of A or R with residues in the binding pocket of the human pregnane X receptor reduces an affinity of the compound for the human pregnane X receptor. Consequently, in some embodiments the steric clash thus reduces the induction (e.g., an activity) of a cytochrome P450 and/or other related proteins.