The antimalarial drug mefloquine binds to membrane phospholipids

The new antimalarial drug mefloquine bound with high affinity (Kd approximately 3 X 10-7 M) to membrane lipids of normal mouse erythrocytes and of erythrocytes infected either with chloroquine-susceptible or chloroquine-resistant Plasmodium berghei. Approximately 80 nmol of mefloquine was bound per mg of total lipid. Mefloquine also bound to purified phospholipids with high affinity (Kd approximately 3 X 10-7 M). Phosphatidylinositol and phosphatidylserine bound 300 to 400 nmol of mefloquine per mg. Phosphatidylcholine and phosphatidylethanolamine bound approximately 100 nmol of mefloquine per mg. Mefloquine did not bind to hemoglobin with high affinity, but it bound to free ferriprotoporphyrin IX with a Kd of approximately 3 X 10-7 M. In comparison with mefloquine, chloroquine did not bind effectively to purified phospholipids, although it is known to bind with high affinity to free ferriprotoporphyrin IX. Greater binding to phospholipids may account for the superiority of mefloquine in the treatment of chloroquine-resistant malaria.