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The gametocytocidal action of a new enamine analogue of primaquine, elubaquine (compound CDRI 80/53, bulaquine), has been evaluated against Plasmodium cynomolgi B in rhesus monkeys. Colony bred Anopheles stephensi mosquitoes were fed on gametocyte carrying rhesus monkeys prior to and at varying intervals after oral administration of a single dose of elubaquine at doses ranging between 0.63 and 5.00 mg/kg. Complete loss of oocyst development and mosquito infectivity was observed within 24 h after administering a single 1.25 mg/kg dose, while higher dose of 3.75 mg/kg inhibited oocyst development within 5 h, indicating gametocytocidal action of the compound. Elubaquine did not show any action against developing oocysts in the vector.

The spectrum of antimalarial activity of the new macrolide antibiotic azithromycin was evaluated against blood- and sporozoite-induced infections with a chloroquine-resistant strain of Plasmodium yoelii nigeriensis (N-67) in Swiss mice and with simian parasite Plasmodium cynomolgi B in rhesus monkeys. Against experimental rodent malaria, a 70 mg/kg/day dose showed curative blood-schizontocidal activity in a four-dose regimen administered orally from day 0 to day 3 or from day 2 to day 5 to mice harboring established infection. The curative response was also obtained with a 40 mg/kg/day dose administered in an extended seven-dose (days 0-6) regimen. Azithromycin was also effective in the causal prophylactic test, since a 50 mg/kg dose from day -1 to day +2 protected mice against P. y. nigeriensis (N-67) sporozoite challenge. In comparison, erythromycin did not show either of the above activities up to a 405 mg/kg/day dose in identical regimens. Comparison of the ED(90) values showed that azithromycin was 31-fold more effective than erythromycin as a blood schizontocide. In the simian model, trophozoite-induced infections of P. cynomolgi B were cured with 25 mg/kg/day azithromycin administered for 7 days. In the causal prophylactic test, the prepatent period was significantly extended in monkeys challenged with P. cynomolgi B sporozoites, presumably because of the growth inhibition of preerythrocytic schizonts in hepatocytes. Azithromycin did not exhibit any hypnozoitocidal (dormant exoerythrocytic stages) activity at 25 mg/kg/day in a seven-dose regimen., (Copyright 2000 Academic Press.)

The water-soluble artemisinin analogue sodium beta-artelinate, a fast-acting blood schizontocide, was evaluated for gametocytocidal action against simian malaria Plasmodium cynomolgi B, and a single dose of the compound has been found to be an effective gametocytocide by both oral and intravenous routes. The compound was able to sterilize the circulating gametocytes in rhesus monkey, resulting in loss of mosquito infectivity and oocyst development in the Anopheles stephensi. However, no sporontocidal action has been observed with this compound.