There’s an interesting article on how hydroxychloroquine works in the case of other diseases here:
https://www.nature.com/articles/s41584-020-0372-x
Review Article
Published: 07 February 2020
Mechanisms of action of hydroxychloroquine and chloroquine: implications for rheumatology
Eva Schrezenmeier & Thomas Dörner
Nature Reviews Rheumatology volume 16, pages155–166(2020)Cite this article
I have a rather frail cousin about my age who took HCQ for eighteen years, 400mg QD, every day. Her only symptom was a reduction in her RA discomfort.