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Pharmacology of DB844, an orally active aza analogue of pafuramidine, in a monkey model of second stage human African trypanosomiasis.

Thuita JK, Wang MZ, Kagira JM, Denton CL, Paine MF, Mdachi RE, Murilla GA, Ching S, Boykin DW, Tidwell RR, Hall JE, Brun R - PLoS Negl Trop Dis (2012)

Bottom Line: However, some animals relapsed during the 300 days of post treatment monitoring, resulting in a cure rate of 3/8 (37.5%) and 3/7 (42.9%) for the 5 mg/kg×10 days and the 6 mg/kg×14 days dose regimens respectively.These DB844 efficacy data were an improvement compared with pentamidine and pafuramidine both of which were previously shown to be non-curative in this model of CNS stage HAT.These data show that synthesis of novel diamidines with improved activity against CNS-stage HAT was possible.

View Article: PubMed Central - PubMed

Affiliation: Trypanosomiasis Research Centre, Kenya Agricultural Research Institute (TRC-KARI), Kikuyu, Kenya. thuitajk@yahoo.com

ABSTRACT
Novel drugs to treat human African trypanosomiasis (HAT) are still urgently needed despite the recent addition of nifurtimox-eflornithine combination therapy (NECT) to WHO Model Lists of Essential Medicines against second stage HAT, where parasites have invaded the central nervous system (CNS). The pharmacology of a potential orally available lead compound, N-methoxy-6-{5-[4-(N-methoxyamidino) phenyl]-furan-2-yl}-nicotinamidine (DB844), was evaluated in a vervet monkey model of second stage HAT, following promising results in mice. DB844 was administered orally to vervet monkeys, beginning 28 days post infection (DPI) with Trypanosoma brucei rhodesiense KETRI 2537. DB844 was absorbed and converted to the active metabolite 6-[5-(4-phenylamidinophenyl)-furanyl-2-yl]-nicotinamide (DB820), exhibiting plasma C(max) values of 430 and 190 nM for DB844 and DB820, respectively, after the 14th dose at 6 mg/kg qd. A 100-fold reduction in blood trypanosome counts was observed within 24 h of the third dose and, at the end of treatment evaluation performed four days post the last drug dose, trypanosomes were not detected in the blood or cerebrospinal fluid of any monkey. However, some animals relapsed during the 300 days of post treatment monitoring, resulting in a cure rate of 3/8 (37.5%) and 3/7 (42.9%) for the 5 mg/kg×10 days and the 6 mg/kg×14 days dose regimens respectively. These DB844 efficacy data were an improvement compared with pentamidine and pafuramidine both of which were previously shown to be non-curative in this model of CNS stage HAT. These data show that synthesis of novel diamidines with improved activity against CNS-stage HAT was possible.

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HPLC/UV chromatograms and concentration-time profiles of DB844/metabolites following incubation of DB844 with male vervet monkey liver microsomes.A: HPLC/UV chromatograms; B: Concentration-time profiles of DB844 and metabolites. Incubation mixtures (1 ml at pH7.4, in triplicate) contained 10 µM DB844 and 0.2 mg/ml monkey liver microsomes. Aliquots were taken at 0.2, 5, 15, 30, and 120 min and evaluated for concentrations of DB844 and six metabolites (M1A, M1B, M2A, M2B, M3, and DB820). Metabolites M4A and M4B were not quantified due to lack of synthetic standards.
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pntd-0001734-g002: HPLC/UV chromatograms and concentration-time profiles of DB844/metabolites following incubation of DB844 with male vervet monkey liver microsomes.A: HPLC/UV chromatograms; B: Concentration-time profiles of DB844 and metabolites. Incubation mixtures (1 ml at pH7.4, in triplicate) contained 10 µM DB844 and 0.2 mg/ml monkey liver microsomes. Aliquots were taken at 0.2, 5, 15, 30, and 120 min and evaluated for concentrations of DB844 and six metabolites (M1A, M1B, M2A, M2B, M3, and DB820). Metabolites M4A and M4B were not quantified due to lack of synthetic standards.

Mentions: DB844 was rapidly metabolized in vervet monkey liver microsomes (MLM) with a microsomal half-life of approximately 14 min to form at least seven metabolites over a 120 min incubation period (Figure 2). The first two metabolites to be detected, M1A and M1B, were likely formed through the oxidative O-demethylation of either the pyridyl or phenyl side of DB844 [13]. M1A and M1B gave rise to M2A and M2B respectively, through reductive N-dehydroxylation, or further O-demethylation to form the bis-amidoxime metabolite, M3. The O-demethylation of M2A and M2B resulted in M4A and M4B, respectively, which could also be generated by N-dehydroxylation of M3. At last, the N-dehydroxylation of M4A and M4B gave rise to the active metabolite DB820 (Figure 2). Metabolites M1A and M1B attained the highest concentrations during the initial 20 minutes of incubation after which M3 became the metabolite with the highest concentration in the drug/liver microsome mixture (Figure 2).


Pharmacology of DB844, an orally active aza analogue of pafuramidine, in a monkey model of second stage human African trypanosomiasis.

Thuita JK, Wang MZ, Kagira JM, Denton CL, Paine MF, Mdachi RE, Murilla GA, Ching S, Boykin DW, Tidwell RR, Hall JE, Brun R - PLoS Negl Trop Dis (2012)

HPLC/UV chromatograms and concentration-time profiles of DB844/metabolites following incubation of DB844 with male vervet monkey liver microsomes.A: HPLC/UV chromatograms; B: Concentration-time profiles of DB844 and metabolites. Incubation mixtures (1 ml at pH7.4, in triplicate) contained 10 µM DB844 and 0.2 mg/ml monkey liver microsomes. Aliquots were taken at 0.2, 5, 15, 30, and 120 min and evaluated for concentrations of DB844 and six metabolites (M1A, M1B, M2A, M2B, M3, and DB820). Metabolites M4A and M4B were not quantified due to lack of synthetic standards.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3404106&req=5

pntd-0001734-g002: HPLC/UV chromatograms and concentration-time profiles of DB844/metabolites following incubation of DB844 with male vervet monkey liver microsomes.A: HPLC/UV chromatograms; B: Concentration-time profiles of DB844 and metabolites. Incubation mixtures (1 ml at pH7.4, in triplicate) contained 10 µM DB844 and 0.2 mg/ml monkey liver microsomes. Aliquots were taken at 0.2, 5, 15, 30, and 120 min and evaluated for concentrations of DB844 and six metabolites (M1A, M1B, M2A, M2B, M3, and DB820). Metabolites M4A and M4B were not quantified due to lack of synthetic standards.
Mentions: DB844 was rapidly metabolized in vervet monkey liver microsomes (MLM) with a microsomal half-life of approximately 14 min to form at least seven metabolites over a 120 min incubation period (Figure 2). The first two metabolites to be detected, M1A and M1B, were likely formed through the oxidative O-demethylation of either the pyridyl or phenyl side of DB844 [13]. M1A and M1B gave rise to M2A and M2B respectively, through reductive N-dehydroxylation, or further O-demethylation to form the bis-amidoxime metabolite, M3. The O-demethylation of M2A and M2B resulted in M4A and M4B, respectively, which could also be generated by N-dehydroxylation of M3. At last, the N-dehydroxylation of M4A and M4B gave rise to the active metabolite DB820 (Figure 2). Metabolites M1A and M1B attained the highest concentrations during the initial 20 minutes of incubation after which M3 became the metabolite with the highest concentration in the drug/liver microsome mixture (Figure 2).

Bottom Line: However, some animals relapsed during the 300 days of post treatment monitoring, resulting in a cure rate of 3/8 (37.5%) and 3/7 (42.9%) for the 5 mg/kg×10 days and the 6 mg/kg×14 days dose regimens respectively.These DB844 efficacy data were an improvement compared with pentamidine and pafuramidine both of which were previously shown to be non-curative in this model of CNS stage HAT.These data show that synthesis of novel diamidines with improved activity against CNS-stage HAT was possible.

View Article: PubMed Central - PubMed

Affiliation: Trypanosomiasis Research Centre, Kenya Agricultural Research Institute (TRC-KARI), Kikuyu, Kenya. thuitajk@yahoo.com

ABSTRACT
Novel drugs to treat human African trypanosomiasis (HAT) are still urgently needed despite the recent addition of nifurtimox-eflornithine combination therapy (NECT) to WHO Model Lists of Essential Medicines against second stage HAT, where parasites have invaded the central nervous system (CNS). The pharmacology of a potential orally available lead compound, N-methoxy-6-{5-[4-(N-methoxyamidino) phenyl]-furan-2-yl}-nicotinamidine (DB844), was evaluated in a vervet monkey model of second stage HAT, following promising results in mice. DB844 was administered orally to vervet monkeys, beginning 28 days post infection (DPI) with Trypanosoma brucei rhodesiense KETRI 2537. DB844 was absorbed and converted to the active metabolite 6-[5-(4-phenylamidinophenyl)-furanyl-2-yl]-nicotinamide (DB820), exhibiting plasma C(max) values of 430 and 190 nM for DB844 and DB820, respectively, after the 14th dose at 6 mg/kg qd. A 100-fold reduction in blood trypanosome counts was observed within 24 h of the third dose and, at the end of treatment evaluation performed four days post the last drug dose, trypanosomes were not detected in the blood or cerebrospinal fluid of any monkey. However, some animals relapsed during the 300 days of post treatment monitoring, resulting in a cure rate of 3/8 (37.5%) and 3/7 (42.9%) for the 5 mg/kg×10 days and the 6 mg/kg×14 days dose regimens respectively. These DB844 efficacy data were an improvement compared with pentamidine and pafuramidine both of which were previously shown to be non-curative in this model of CNS stage HAT. These data show that synthesis of novel diamidines with improved activity against CNS-stage HAT was possible.

Show MeSH
Related in: MedlinePlus