Stage-specific pharmacodynamic chloroquine and pyronaridine action on artemisinin ring-stage resistant Kelch C580Y mutation Plasmodium falciparum correlates to hemozoin inhibition process

The antimalarial quinolines pyronaridine and chloroquine both inhibit hemozoin crystallization, predominately produced by Plasmodium falciparum intraerythrocytic trophozoite stage parasites. Pyronaridine extends activity to ring-stage chloroquine-sensitive parasites, in contrast to chloroquine. Here, we investigated chloroquine and pyronaridine hemozoin inhibition type correlated to stage-specific activity on chloroquine-resistant ring-stage artemisinin sensitive and resistant P. falciparum CamWT and CamWT-C580Y parasites. Pyronaridine (2.8 μM) is tenfold more potent at beta-hematin nucleation than chloroquine (40 μM). Both pyronaridine and chloroquine (0.2 and 0.7 μM, respectively) had similar sub-μM inhibition of beta-hematin extension. P. falciparum CamWT-C580Y parasites produce smaller width hemozoin crystals which extend less than isogenic CamWT hemozoin. Stage-specific pulse dose pyronaridine and chloroquine on CamWT-C580Y or CamWT isogenic parasites observed 3- to 4-fold higher pyronaridine IC₅₀s compared to 10- to 15-fold higher chloroquine on most CamWT-C580Y to CamWT stages. These findings collectively show that hemozoin nucleation inhibition widens stage-specific pyronaridine activity on P. falciparum drug-resistant parasites.