Halofantrine is a drug used to treat malaria. It belongs to the phenanthrene class of compounds that includes quinine and lumefantrine. It appears to inhibit polymerisation of heme molecules (by the parasite enzyme "heme polymerase"), resulting in the parasite being poisoned by its own waste. Halofantrine has been shown to preferentially block open and inactivated HERG channels leading to some degree of cardiotoxicity.   From: DrugBank