Neither hydroxychloroquine (HQC) nor chloroquine (CQ) interact with the active site of ACE2, which is the region of the receptor where the substrate enters. However, HQC has been shown to interact with the amino acids ASP350, ASP382, ALA348, PHE40, and PHE390 in the nearby allosteric region of the receptor. This causes a conformational change in the enzyme and prevents SARS-CoV-2 S protein from interacting with ACE2. These results cautiously suggest that HQC may be best used preventatively because of its ability to allosterically change the shape of the active site and inability to prevent competitive viruses from interacting with it.