In vitro study on the effect of the new chemotherapeutic agents CGP 6140 and CGP 20376 on the microfilariae of Onchocerca volvulus.

The effect of two new filaricidal compounds, CGP 6140 and CGP 20376, on the microfilariae of O. volvulus was tested in vitro. Culture medium consisted of a 1:1 mixture of IMDM/NCTC 135 supplemented with 20% heat-inactivated foetal calf serum and gentamycin. For pulse experiments the microfilariae were exposed to the drugs for one or three hours in medium without serum and then replaced to serum supplemented medium. In the continuous cultures the microfilariae were exposed to the drugs fur up to 72 hours without a change of medium. The effect of the drugs was assessed by their ability to reduce the larval motility. A reduction of motility of 98-100% after 24 hours of exposure occurred at levels of 1 micron/ml CGP 20376 or 10 mu mg/ml CGP 6140. After exposure for one hour CGP 20376 immobilized 100% of the microfilariae irreversibly at a drug level of 1 microgram/ml. Whereas no significant immobilization was seen with CGP 6140 after one hour. After exposure for three hours CGP 6140 immobilized up to 100% of the microfilariae at drug levels of 10 and 5 micrograms/ml.