Wikipedia says: "Hydroxychloroquine was approved for medical use in the United States in 1955.[1] It is on the World Health Organization's List of Essential Medicines, the safest and most effective medicines needed in a health system.[5] The wholesale cost in the developing world is about US$4.65 per month as of 2015, when used for rheumatoid arthritis or lupus.[6] In the United States the wholesale cost of a month of treatment is about US$25 as of 2020
That's old enough that there is no patent on the drug and I am sure many public domain synthesis paths: somebody might have a newer, better, cheaper way to make it which is patented, but there is no legal barrier to making it.
> The core list presents a list of minimum medicine needs for a basic health-care system, listing the most efficacious, safe and cost–effective medicines for priority conditions. Priority conditions are selected on the basis of current and estimated future public health relevance, and potential for safe and cost-effective treatment.
WHO is saying "this medication is the safest medication available to treat malaria". It's definitely not saying "this medication is safe".
For chloroquine they say "* For use only for the treatment of P.vivax infection", so they're not even saying "this is the safest med for malaria", they're saying "for this one type of malaria this is the safest med".
That's old enough that there is no patent on the drug and I am sure many public domain synthesis paths: somebody might have a newer, better, cheaper way to make it which is patented, but there is no legal barrier to making it.