Chloroquine passively diffuses through cell membranes and into lysosomes, where it becomes protonated and cannot leave. It increases endosomal pH. Chloroquine prevents glycosylation of ACE2, the receptor that SARS-CoV-2 targets for cell entry.
drugbankChloroquine is an aminoquinolone derivative first developed in the 1940s for the treatment of malaria. It was the drug of choice to treat malaria until the development of newer antimalarials such as pyrimethamine, artemisinin, and mefloquine. Chloroquine was granted FDA Approval on 31 October 1949.
https://www.drugbank.ca/drugs/DB00608
So essentially sounds like it prevents the ACE receptor from being able to interact with the virus.