Efficacy of the Novel Diamidine Compound 2,5-Bis(4-Amidinophenyl)-Furan-Bis- O -Methlylamidoxime (Pafuramidine, DB289) against Trypanosoma brucei rhodesiense Infection in Vervet Monkeys after Oral Administration (cid:1)

Owing to the lack of oral drugs for human African trypanosomiasis, patients have to be hospitalized for 10 to 30 days to facilitate treatment with parenterally administered medicines. The efficacy of a novel orally administered prodrug, 2,5-bis(4-amidinophenyl)-furan-bis- O -methlylamidoxime (pafuramidine, DB289), was tested in the vervet monkey ( Chlorocebus [ Cercopithecus ] aethiops ) model of sleeping sickness. Five groups of three animals each were infected intravenously with 10 4 Trypanosoma brucei rhodesiense KETRI 2537 cells. On the seventh day postinfection (p.i.) in an early-stage infection, animals in groups 1, 2, and 3 were treated orally with pafuramidine at dose rates of 1, 3, or 10 mg/kg of body weight, respectively, for five consecutive days. The animals in groups 4 and 5 were treated with 10 mg/kg for 10 consecutive days starting on the 14th day p.i. (group 4) or on the 28th day p.i. (group 5), when these animals were in the late stage of the disease. In the groups treated in the early stage, 10 mg/kg of pafuramidine completely cured all three monkeys, whereas lower doses of 3 mg/kg and 1 mg/kg cured only one of three and zero of three monkeys, respectively. Treatment of late-stage infections resulted in cure rates of one of three (group 4) and zero of three (group 5) monkeys. These studies demonstrated that pafuramidine was orally active in monkeys with early-stage T. brucei rhodesiense infections at dose rates above 3 mg/kg for 5 days. It was also evident that the drug attained only minimal efficacy against late-stage infections, indicating the limited ability of the molecule to cross the blood-brain barrier. This study has shown that oral diamidines have potential for the treatment of early-stage sleeping sickness. (detection limit, 10 3 trypanosomes/ml of blood). Blood collected by inguinal venipuncture was used for parasitemia determinations using both the wet-film and HCT methods. For estimation of parasites in the CSF, some of the free-flowing CSF was collected into a capillary tube and immediately transferred into a hemocytometer chamber to count the number of trypanosomes and white cells. Negative CSF samples were then centrifuged and reexamined for trypanosomes. In cases where no parasites were detected in either blood or CSF by the above-described methods, Swiss white mice were used to test for the presence of trypanosomes (11). Samples of 0.2 ml of blood or CSF were inoculated intraperitoneally into two mice per sample.