Based on this premise, we initiated a screening to identify possible SMIs of this PPI [12], during which we discovered that methylene blue (MeBlu), a tricyclic small-molecule dye, which is approved for the treatment of acquired methemoglobinemia and some other clinical uses [19,20,21,22], inhibits the SARS-CoV-2–hACE2 PPI and the entry of SARS-CoV-2 spike-bearing pseudoviruses into ACE2-expressing cells [23]. This evidence concerns the gene ACE2 and methemoglobinemia.