Pharmacology of DB844, an Orally Active aza Analogue of Pafuramidine, in a Monkey Model of Second Stage Human African Trypanosomiasis

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-y​l]-nicotinamide(DB820), exhibiting plasma Cmax 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.This investigation received financial support from the Bill and Melinda Gates Foundation through the Consortium for Parasitic Drug Development

Safety, pharmacokinetic, and efficacy studies of oral DB868 in a first stage vervet monkey model of human African trypanosomiasis

There are no oral drugs for human African trypanosomiasis (HAT, sleeping sickness). A successful oral drug would have the potential to reduce or eliminate the need for patient hospitalization, thus reducing healthcare costs of HAT. The development of oral medications is a key objective of the Consortium for Parasitic Drug Development (CPDD). In this study, we investigated the safety, pharmacokinetics, and efficacy of a new orally administered CPDD diamidine prodrug, 2,5-bis[5-(N-methoxyamidino)-2-pyridyl]furan (DB868; CPD-007-10), in the vervet monkey model of first stage HAT. DB868 was well tolerated at a dose up to 30 mg/kg/day for 10 days, a cumulative dose of 300 mg/kg. Mean plasma levels of biomarkers indicative of liver injury (alanine aminotransferase, aspartate aminotransferase) were not significantly altered by drug administration. In addition, no kidney-mediated alterations in creatinine and urea concentrations were detected. Pharmacokinetic analysis of plasma confirmed that DB868 was orally available and was converted to the active compound DB829 in both uninfected and infected monkeys. Treatment of infected monkeys with DB868 began 7 days post-infection. In the infected monkeys, DB829 attained a median Cmax (dosing regimen) that was 12-fold (3 mg/kg/day for 7 days), 15-fold (10 mg/kg/day for 7 days), and 31-fold (20 mg/kg/day for 5 days) greater than the IC50 (14 nmol/L) against T. b. rhodesiense STIB900. DB868 cured all infected monkeys, even at the lowest dose tested. In conclusion, oral DB868 cured monkeys with first stage HAT at a cumulative dose 14-fold lower than the maximum tolerated dose and should be considered a lead preclinical candidate in efforts to develop a safe, short course (5-7 days), oral regimen for first stage HAT

Spatial–Temporal Variations in Parasitological Prevalence and Host-Related Risk Factors of Camel Trypanosomiasis and Its Vectors in North Eastern Kenya: A Repeated Cross-Sectional Study

Camel trypanosomiasis (Surra) is endemic in the Horn of Africa. Understanding the spatiotemporal variations in Surra prevalence, vector dynamics, and host-related risk factors is important in developing effective control strategies. A repeated cross-sectional study was conducted to determine the Surra parasitological prevalence, livestock reservoirs, vector density/diversity, and host-related risk factors in Kenya. Random samples of 847, 1079, and 824 camels were screened at the start of the dry season, peak dry season, and during the rainy season, respectively. Blood samples were examined using the dark ground/phase contrast buffy-coat technique, and Trypanosoma species were identified based on their movement and morphology in wet and stained thin smears. Reservoir status for Trypanosoma evansi was assessed in 406 cattle and 372 goats. A rainy and dry seasons entomological surveys were conducted to determine the Surra vector abundance/diversity and spatiotemporal density changes. Surra prevalence was 7.1%, 3.4%, and 4.1% at the start of the dry season, peak dry season, and rainy season, respectively. Camel co-infections by Trypanozoon (T. evansi or Trypanosoma brucei brucei) and Trypanosoma vivax were recorded. Spatial variations in Surra prevalence were recorded at the beginning of dry (X7,N=8462=110.9, p≤0.001), peak dry (X7,N=10792=42.2, p≤0.001), and rainy (X7,N=8242=29.1, p≤0.001) seasons. The screened cattle and goats tested negative for Trypanozoon (T. evansi or T. b. brucei), while two cattle tested positive for Trypanosoma congolense. Biting fly catches were composed of a single species from Tabanus, Atylotus, Philoliche, Chrysops, and Stomoxys genera. The total catches for Philoliche, Chrysops, and Stomoxys were higher in the rainy than dry season consistent with the prevalence results. Surra remains an important camel disease in the region with its prevalence varying in space and time. Camel co-infections by Trypanozoon (T. evansi or T. b. brucei) and T. vivax necessitate proper diagnosis of suspected cases and targeted therapy

Parasitaemia pattern in monkeys infected with <i>T.b. rhodesiense</i> KETRI 2537 and subsequently treated with DB844.

<p>Symbols and error bars represent means and SEs, respectively, of 7 animals; monkeys were treated with DB844 at 6 mg/kg×14 days, from 28–41 days post infection; Log parasitaemia values were determined by microscopic examination of wet smears of blood using the matching method of Herbert and Lumsden, 1976 <a href="http://www.plosntds.org/article/info:doi/10.1371/journal.pntd.0001734#pntd.0001734-Ndungu1" target="_blank">[23]</a>.</p

Plasma concentration-time profiles following oral administration of the last (14^th) daily dose of DB844.

<p>Symbols and error bars represent geometric means and SEs, respectively, for DB844 (△) and DB820 (○). The monkeys (n = 7) were treated with DB844 at 6 mg/kg×14 days, from 28–41 days post infection. The insert graph shows the extended profile up to 28 days post the last daily dose of DB844.</p

Haematologic effects of <i>T. b. rhodesiense</i> KETRI2537 infection and treatment with DB844 in vervet monkeys.

<p>Key: RBC = red blood cells; WBC = White blood cells; g/dl = grams/decilitre; fl = femtolitres; p-values<0.05 indicate values that were significantly different from pre-infection baseline (day 0) values (Repeated measures Anova with Fishers PLSD post hoc test); Monkey were treated with DB844 at 6 mg/kg×14 days, from 28–41 days post infection.</p

Changes in red cell distribution width in monkeys following infection and subsequent treatment with DB844.

<p>Symbols and error bars represent means and SEs, respectively, of seven monkeys that were treated with DB844 at 6 mg/kg×14 days, from 28–41 days post infection.</p

Transient infection and DB844 induced changes in clinical chemistry indicators of liver and kidney function.

<p>Symbols represent mean ± SE (n = 7) of aspartate aminotransferase (AST, ▪), alanine aminotransferase (ALT, □), total bilirubin (•), direct bilirubin (0), blood urea nitrogen (BUN, ▴) and albumin (◊); monkeys were treated with DB844 at 6 mg/kg×14 days, from 28–41 days post infection.</p

Chemical structure of DB844 and DB820.

<p>Chemical structure of DB844 and DB820.</p