Hydroxychloroquine

Hydroxychloroquine is a 4-aminoquinoline derivative. Hydroxychloroquine is a weakly basic molecule that can accumulate in lysosomes and endosomes, raising their internal pH and thereby inhibiting the activity of enzymes that depend on an acidic environment. This reduces the efficiency of antigen peptide processing and MHC class II presentation, leading to weaker T cell activation. It can also inhibit Toll-like receptors (TLR7 and TLR9), reducing the release of interferons and multiple pro-inflammatory cytokines, thereby lowering chronic inflammatory responses. Hydroxychloroquine is also thought to interfere with heme detoxification-related processes within the food vacuole of Plasmodium parasites, including effects on heme polymerization/crystallization, leading to the accumulation of toxic heme and ultimately killing the malaria parasites hiding inside red blood cells.