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 C_max (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.     

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-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.     

Efficacy study of novel diamidine compounds in a Trypanosoma evansi goat model

Three diamidines (DB 75, DB 867 and DB 1192) were selected and their ability to cure T. evansi experimentally infected goats was investigated. A toxicity assessment and pharmacokinetic analysis of these compounds were additionally carried out. Goats demonstrated no signs of acute toxicity, when treated with four doses of 1 mg/kg/day (total dose 4 mg/kg). Complete curative efficacy of experimentally infected goats was seen in the positive control group treated with diminazene at 5 mg/kg and in the DB 75 and DB 867 groups treated at 2.5 mg/kg. Drug treatment was administered once every second day for a total of seven days. Complete cure was also seen in the group of goats treated with DB 75 at 1.25 mg/kg. DB 1192 was incapable of curing goats at either four-times 2.5 mg/kg or 1.25 mg/kg. Pharmacokinetic analysis clearly demonstrated that the treatment failures of DB 1192 were due to sub-therapeutic compound levels in goat plasma, whilst compound levels for DB 75 and DB 867 remained well within the therapeutic window. In conclusion, two diamidine compounds (DB 75 and DB 867) presented comparable efficacy at lower doses than the standard drug diminazene and could be considered as potential clinical candidates against T. evansi infection.     

Experimental treatment of Neospora caninum-infected mice with the arylimidamide DB750 and the thiazolide nitazoxanide

The cationic arylimidamide DB750 and the thiazolide nitazoxanide had been shown earlier to be effective against Neospora caninum tachyzoites in vitro with an IC₅₀ of 160 nM and 4.23 μM, respectively. In this study, we have investigated the effects of DB750 and nitazoxanide treatments of experimentally infected Balb/c mice, by applying the drugs either through the oral or the intraperitoneal route. In experiment 1, administration of DB750 (2 mg/kg/day) and nitazoxanide (150 mg/kg/day) started already 3 days prior to experimental infection of mice with 2 × 10⁶ tachyzoites. Following infection, the drugs were further administrated daily for a period of 2 weeks, either orally or intraperitoneally. Intraperitoneal injection of DB750 was well tolerated by the mice, but treatment with nitazoxanide resulted in death of all mice within 3 days. Upon intraperitoneal application of DB750, the cerebral parasite load was significantly reduced compared to all other groups, while oral application of DB750 and nitazoxanide were not as effective, and resulted in significant weight loss. In experiment 2, mice were infected with 2 × 10⁶ tachyzoites and at 2 weeks post-infection, DB750 (2 mg/kg/day) was applied by intraperitoneal injections for 14 days. In the DB750-treated group, only 2 out of 12 mice succumbed to infection, compared to 7 out of 12 mice in the placebo-group. DB750 treatment also resulted in significantly reduced cerebral parasite burden, and reduced numbers of viable tachyzoites. Our data suggest that DB750 exerted its activity also after crossing the blood–brain barrier, and that this class of compounds could be promising for the control of N. caninum-associated disease.     

New imidazolidinedione derivatives as antimalarial agents

A series of new N-alky- and N-alkoxy-imidazolidinediones was prepared and assessed for prophylactic and radical curative activities in mouse and Rhesus monkey models. New compounds are generally metabolically stable, weakly active in vitro against Plasmodium falciparum clones (D6 and W2) and in mice infected with Plasmodium berghei sporozoites. Representative compounds 8e and 9c showed good causal prophylactic activity in Rhesus monkeys dosed 30 mg/kg/day for 3 consecutive days by IM, delayed patency for 19-21 days and 54-86 days, respectively, as compared to the untreated control. By oral, 9c showed only marginal activity in causal prophylactic and radical curative tests at 50 mg/kg/day×3 and 30 mg/kg/day×7 plus chloroquine 10 mg/kg for 7 days, respectively.     

Embryotoxicity studies of norfloxacin in cynomolgus monkeys: I. Teratology studies and norfloxacin plasma concentration in pregnant and nonpregnant monkeys

Norfloxacin, a new orally active antibiotic, was investigated in cynomolgus monkeys for potential developmental toxicity. Fifty-seven monkeys were administered a control vehicle or norfloxacin by nasogastric gavage during the major period of organogenesis on gestational days (GD) 21 through 50 at doses of 0, 50, 100, 150, or 200/300 mg/kg/day. There was no evidence of teratogenicity at any dose level. Maternotoxicity and a significant increase in embryolethality occurred following doses of 200/300 mg/kg/day. The maternotoxicity was not expected based on range-finding studies in nonpregnant female monkeys, which showed no signs of toxicity in doses up to 500 mg/kg/day. Additional studies were conducted to determine if norfloxacin caused similar toxicity later in gestation. Forty-six pregnant monkeys were dosed with a control vehicle or 200 mg/kg/day norfloxacin for one of three 10-day periods on GD 36-45, 71-80, or 111-120. There were no maternotoxic, embryotoxic, or fetotoxic effects observed. Plasma concentrations of norfloxacin in five cynomolgus monkeys following 50 and 200 mg/kg oral doses were not dose-proportionate. However, at a given dose, administered in cross-over fashion, plasma concentrations of norfloxacin were higher in nonpregnant females (approximately 20-40%) than during pregnancy when the same subject was compared. At the no-observed-effect dose for maternal and embryotoxicity (50 mg/kg), peak plasma concentrations of norfloxacin in pregnant cynomolgus monkeys are approximately threefold higher than those observed in human volunteers receiving norfloxacin at the maximum recommended therapeutic dose of 400 mg (5.7 mg/kg based on 70 kg body weight) twice per day.     

Effectiveness of prostaglandin f 2 alpha in restoration of HMG-HCG induced ovulation in indomethacin-treated rhesus monkeys.

Six mature female rhesus monkeys were treated with HMG-HCG in control cycles at doses adjusted to induce ovulation while avoiding superovulation. Occurrence of ovulation was determined by observation of fresh ovulation points at laparotomy 48 to 120 hours following HCG. In subsequent cycles animals were treated with indomethacin (treatment days 4 through 10) together with the established dose of HMG-HCG. In 8 cycles indomethacin 5 mg/kg was given i.m. once daily; in 9 cycles 10 mg/kg i.m. was administered in 2 divided doses. Following this, PGF2alpha (3 mg t.i.d. s.c.) was administered for 3 days together with indomethacin 10 mg/kg and HMG-HCG, beginning on the day prior to HCG. Determinations of progesterone were performed by RIA on treatment days 4, 7, 10, and 11. Eleven of the 13 control cycles were ovulatory. With indomethacin 5 mg/kg/day, 5 of 8 cycles were ovulatory but ovulation was delayed in 2 instances. Of 9 cycles using indomethacin 10 mg/kg/day only 1 was ovulatory. When PGF2alpha was administered in susequent cycles along with indomethacin (10 mg/kg) and HMG-HCG, ovulation occurred in 13 of 19 cycles. These data suggest that local ovarian PGF2alpha may be essential in the mechanics of follicle rupture in gonadotropin-treated rhesus monkeys.     

In vitro and in vivo investigation of the efficacy of arylimidamide DB1831 and its mesylated salt form--DB1965--against Trypanosoma cruzi infection

Chagas disease is caused by infection with the intracellular protozoan parasite Trypanosoma cruzi. At present, nifurtimox and benznidazole, both compounds developed empirically over four decades ago, represent the chemotherapeutic arsenal for treating this highly neglected disease. However, both drugs present variable efficacy depending on the geographical area and the occurrence of natural resistance, and are poorly effective against the later chronic stage. As a part of a search for new therapeutic opportunities to treat chagasic patients, pre-clinical studies were performed to characterize the activity of a novel arylimidamide (AIA--DB1831 (hydrochloride salt) and DB1965 (mesylate salt)) against T. cruzi. These AIAs displayed a high trypanocidal effect in vitro against both relevant forms in mammalian hosts, exhibiting a high selectivity index and a very high efficacy (IC(50) value/48 h of 5-40 nM) against intracellular parasites. DB1965 shows high activity in vivo in acute experimental models (mouse) of T. cruzi, showing a similar effect to benznidazole (Bz) when compared under a scheme of 10 daily consecutive doses with 12.5 mg/kg. Although no parasitological cure was observed after treating with 20 daily consecutive doses, a combined dosage of DB1965 (5 mg/kg) with Bz (50 mg/kg) resulted in parasitaemia clearance and 100% animal survival. In summary, our present data confirmed that aryimidamides represent promising new chemical entities against T. cruzi in therapeutic schemes using the AIA alone or in combination with other drugs, like benznidazole.     

Effectiveness of prostagland in F2α in restoration of HMG-HCG induced ovulation in indomethacin-treated rhesus monkeys

Six mature female rhesus monkeys were treated with HMG-HCG in control cycles at doses adjusted to induce ovulation while avoiding superovulation. Occurrence of ovulation was determined by observation of fresh ovulation points at laparotomy 48 to 120 hours following HCG. In subsequent cycles animals were treated with indomethacin (treatment days 4 through 10) together with the established dose of HMG-HCG. In 8 cycles indomethacin 5 mg/kg was given i.m. once daily; in 9 cycles 10 mg/kg i.m. was administered in 2 divided doses. Following this, PGF₂α (3 mg t.i.d. s.c.) was administered for 3 days together with indomethacin 10 mg/kg and HMG-HCG, beginning on the day prior to HCG. Determinations of progesterone were performed by RIA on treatment days 4, 7, 10, and 11. Eleven of the 13 control cycles were ovulatory. With indomethacin 5 mg/kg/day, 5 of 8 cycles were ovulatory but ovulation was delayed in 2 instances. Of 9 cycles using indomethacin 10 mg/kg/day only 1 was ovulatory. When PGF₂α was administered in subsequent cycles along with indomethacin (10 mg/kg) and HMG-HCG, ovulation occurred in 13 of 19 cycles. These data suggest that local ovarian PGF₂α may be essential in the mechanics of follicle rupture in gonadotropin-treated rhesus monkeys.     

Effectiveness of prostaglandin F2α in restoration of HMG-HCG induced ovulation in indomethacin-treated rhesus monkeys

Six mature female rhesus monkeys were treated with HMG-HCG in control cycles at doses adjusted to induce ovulation while avoiding superovulation. Occurrence of ovulation was determined by observation of fresh ovulation points at laparotomy 48 to 120 hours following HCG. In subsequent cycles animals were treated with indomethacin (treatment days 4 through 10) together with the established dose of HMG_HCG. In 8 cycles indomethacin 5 mg/kg was given i.m. once daily; in 9 cycles 10 mg/kg i.m. was administered in 2 divided doses. Following this, PGF_2^α (3 mg t.i.d. s.c.) was administered for 3 days together with indomethacin 10 mg/kg and HMG-HCG, beginning on the day prior to HCG. Determinations of progesterone were performed by RIA on treatment days 4, 7, 10, and 11. Eleven of the 13 control cycles were ovulatory. With indomethacin 5 mg/kg/day, 5 of 8 cycles were ovulatory but ovulation was delayed in 2 instances. Of 9 cycles using indomethacin 10 mg/kg/day only 1 was ovulatory. When PGF_2^α was administered in subsequent cycles along with indomethacin (10 mg/kg) and HMG-HCG, ovulation occurred in 13 of 19 cycles. These data suggest that local ovarian PGF_2^α may be essential in the mechanics of follicle rupture in gonadotropin-treated rhesus monkeys.     

Toxicity of pure alkaloid of Tylophora asthamatica in male rat

Administration of pure alkaloid of T. asthamatica, suspended in peanut oil and given in single doses (12-100 mg/kg) by gavage, to male rats caused inactivity, respiratory distress, salivation, nasal discharge and diarrhoea. The oral LD50 value of the alkaloid was 35.32 mg/kg. In short term toxicity study daily doses of the alkaloid (1.25, 2.5, 5 and 10 mg/kg) were given to male rats for 15 days. Smaller doses of the alkaloid (1.25 and 2.5 mg/kg/day) produced no signs of poisoning or death in animals; while 5 mg/kg/day produced signs of poisoning and death of two animals, 10 mg/kg/day caused death of all the animals within 7 days. Activities of glutamic oxaloacetic transaminase, glutamic pyruvic transaminase and alkaline phosphatase were significant and associated with morphological changes in liver. The alkaloid also caused marked changes in the morphology of seminiferous tubules and spermatogenic activity of experimental animals. Since the alkaloid is effective in microgram quantities, the non toxic effects observed after daily doses of 1.25 mg/kg in male rats assume great therapeutic significance.     

Fexinidazole--a new oral nitroimidazole drug candidate entering clinical development for the treatment of sleeping sickness

Background

Human African trypanosomiasis (HAT), also known as sleeping sickness, is a fatal parasitic disease caused by trypanosomes. Current treatment options for HAT are scarce, toxic, no longer effective, or very difficult to administer, in particular for the advanced, fatal stage of the disease (stage 2, chronic HAT). New safe, effective and easy-to-use treatments are urgently needed. Here it is shown that fexinidazole, a 2-substituted 5-nitroimidazole rediscovered by the Drugs for Neglected Diseases initiative (DNDi) after extensive compound mining efforts of more than 700 new and existing nitroheterocycles, could be a short-course, safe and effective oral treatment curing both acute and chronic HAT and that could be implemented at the primary health care level. To complete the preclinical development and meet the regulatory requirements before initiating human trials, the anti-parasitic properties and the pharmacokinetic, metabolic and toxicological profile of fexinidazole have been assessed.

Methods and Findings

Standard in vitro and in vivo anti-parasitic activity assays were conducted to assess drug efficacy in experimental models for HAT. In parallel, a full range of preclinical pharmacology and safety studies, as required by international regulatory guidelines before initiating human studies, have been conducted. Fexinidazole is moderately active in vitro against African trypanosomes (IC₅₀ against laboratory strains and recent clinical isolates ranged between 0.16 and 0.93 µg/mL) and oral administration of fexinidazole at doses of 100 mg/kg/day for 4 days or 200 mg/kg/day for 5 days cured mice with acute and chronic infection respectively, the latter being a model for the advanced and fatal stage of the disease when parasites have disseminated into the brain. In laboratory animals, fexinidazole is well absorbed after oral administration and readily distributes throughout the body, including the brain. The absolute bioavailability of oral fexinidazole was 41% in mice, 30% in rats, and 10% in dogs. Furthermore, fexinidazole is rapidly metabolised in vivo to at least two biologically active metabolites (a sulfoxide and a sulfone derivative) that likely account for a significant portion of the therapeutic effect. Key pharmacokinetic parameter after oral absorption in mice for fexinidazole and its sulfoxide and sulfone metabolites are a C_max of 500, 14171 and 13651 ng/mL respectively, and an AUC_0–24 of 424, 45031 and 96286 h.ng/mL respectively. Essentially similar PK profiles were observed in rats and dogs. Toxicology studies (including safety pharmacology and 4-weeks repeated-dose toxicokinetics in rat and dog) have shown that fexinidazole is well tolerated. The No Observed Adverse Event Levels in the 4-weeks repeated dose toxicity studies in rats and dogs was 200 mg/kg/day in both species, with no issues of concern identified for doses up to 800 mg/kg/day. While fexinidazole, like many nitroheterocycles, is mutagenic in the Ames test due to bacterial specific metabolism, it is not genotoxic to mammalian cells in vitro or in vivo as assessed in an in vitro micronucleus test on human lymphocytes, an in vivo mouse bone marrow micronucleus test, and an ex vivo unscheduled DNA synthesis test in rats.

Conclusions

The results of the preclinical pharmacological and safety studies indicate that fexinidazole is a safe and effective oral drug candidate with no untoward effects that would preclude evaluation in man. The drug has entered first-in-human phase I studies in September 2009. Fexinidazole is the first new clinical drug candidate with the potential for treating advanced-stage sleeping sickness in thirty years.     

Acute and sub-acute toxicity of an insect pheromone, N-heneicosane and combination with insect growth regulator, diflubenzuron, for establishing no observed adverse effect level (NOAEL)

Aedes aegypti mosquito is one of the most notorious vectors of dangerous diseases like dengue hemorrhagic fever and chikangunya. One method of control of the vectors is by the use of semiochemicals or pheromones. The pheromone n-heneicosane (C21) has been proved to be effective in attracting the female Aedes aegypti to lay eggs in the treated water and the growth of the larva is controlled by insect growth regulator diflubenzuron (DB). This study was planned to assess the safety of C21 alone and the combination with DB. Acute toxicity tests were carried out using two doses, viz., 1600 and 3200 mg/kg and two routes of exposure oral and intra-peritoneal. Dermal toxicity test was carried out in both male and female rats at the dose of 3200 mg/kg. Primary skin irritation test was carried out in rabbits. Sub-acute (90 days) dermal toxicity studies in male and female rats at the dose of 1 and 2 mg/kg via the per-cutaneous route were also studied. Sub-acute (90 days) toxicity test through the oral route was carried out, at doses 125, 250 and 500 mg/kg in male and female rats. The calculated LD50 by ip route and dermal route was more than 5 g/kg in mouse and rats of both the sexes. In the primary skin irritation test no significant changes were noted. In the sub-acute toxicity studies even 500 mg/kg dose was not able to produce toxic response in rats when they were dosed daily for 90 days. The established no observed adverse effect level (NOAEL) was more than 500 mg/kg.     

The effect of indomethacin on HMG-HCG induced ovulation in the rhesus monkey

The investigation was designed to study the influence of indomethacin on gonadotropin induced ovulation in the rhesus monkey. Six mature female monkeys were treated with HMG-HCG for at least 2 control ovulatory cycles at dosage levels adjusted to induce ovulation while avoiding superovulation. Ovulation was confirmed by observation of the ovaries for fresh ovulation points at laparotomy. Following establishment of an appropriate dosage schedule, treatment was begun with indomethacin (5 mg/kg/day) starting 5 days prior to HCG and continuing to the time of laparotomy. In a second treatment cycle, indomethacin was administered at a dose of 5 mg/kg b.i.d. together with the established dose of HMG-HCG. Ovarian inspection was carried out as in the control cycles. Venous blood was obtained on treatment days 4, 7, 10 and 11 for determination of serum estrone, estradiol and progesterone. Indomethacin administration resulted in ovulation inhibition at a dose of 10 mg/kg/day when ovulation inducing doses of gonadotropins were administered. Peripheral blood steroid levels suggest that follicle maturation and estrogen production are unimpaired by indomethacin. These findings indicate that the ovarian synthesis of prostaglandin may be essential in the process of ovulation.     

The effect of indomethacin of HMG-HCG induced ovulation in the phesus monkey.

The investigation was designed to study the influence of indomethacin on gonadotropin induced ovulation in the rhesus monkey. Six mature female monkeys were treated with HMG-HCG for at least 2 control ovulatory cycles at dosage levels adjusted to induced ovulation while avoiding superovulation. Ovulation was confirmed by observation of the ovaries for fresh ovulation points at laparotomy. Following establishment of an appropriate dosage schedule, treatment was begun with indomethacin (5 mg/kg/day) starting 5 days prior to HCG and continuing to the time of laparotomy. In a second treatment cycle, indomethacin was administered at a dose of 5 mg/kg b.i.d. together with the established dose of HMG-HCG. Ovarian inspection was carried out as in the control cycles. Venous blood was obtained on treatment days 4, 7, 10 and 11 for determination of serum estrone, estradiol and progesterone. Indomethacin administration resulted in ovulation inhibition at a dose of 10 mg/kg/day when ovulation inducing doses of gonadotropins were administered. Peripheral blood steroid levels suggest that follicle maturation and estrogen production was unimparied by indomethacin. These findings indicate that the ovarian synthesis of prostaglandin may be essential in the process of ovulation.     

Effect of chronic D-fenfluramine administration on rat hypothalamic serotonin levels and release

D-fenfluramine, an anorectic agent in rats and man, was administered daily at doses 1.25, 2.5, 5 or 10 mg/kg/day for 10 days, and sacrificed 6 days later. Hypothalamic serotonin (5-HT) levels were unchanged in rats receiving 1.25-5 mg/kg/day of d-fenfluramine but reduced by 22% (p less than 0.01) at the highest drug dose (10 mg/kg/day); hypothalamic 5-hydroxyindole acetic acid (5-HIAA) levels were reduced by 15% (p less than 0.05) or 28% (p less than 0.01) in rats receiving 5 or 10 mg/kg/day of the drug, respectively. Hypothalamic slices prepared from rats which were previously treated with any of the drug doses spontaneously released endogenous 5-HT at rates that did not differ from those of vehicle-treated rats. 5-HT released with electrical field-stimulation was unaffected by prior d-fenfluramine treatment at doses of 1.25-5 mg/kg/day, and was reduced by 20% (p less than 0.05) from slices prepared from rats which received 10 mg/kg/day. 5-HIAA efflux was also attenuated by the highest drug dose. These data indicate that chronic administration to rats of customary anorectic doses of d-fenfluramine (i.e. 0.06-1.25 mg/kg) fail to cause long-lasting reductions in brain 5-HT release.     

Differential recovery of intestine, bone marrow, and thymus of rats with solid tumors following 5-fluorouracil administration.

Time relationships for recovery of several host organs from toxic effects of 5-fluorouracil were determined in ACI rats bearing Morris hepatoma 3924A. A single injection of 150 mg/kg body weight 5-fluorouracil (the LD10) resulted in loss of 90% of the tibial bone marrow, 60% of the intestinal mucosa, and 90% of the thymus as measured by total DNA content of the organs. Organ DNA contents following 150 mg/kg of the drug were minimal on day 3 for intestine and on day 5 for marrow and thymus. A return to pretreatment or higher levels of DNA was observed by day 4 for intestine, day 11 for tibial marrow, and day 19 for thymus. Incorporation of 3H-deoxyuridine into host organ DNA after 150 mg/kg 5-fluorouracil was inhibited 36 hrs for intestine, 3 days for thymus, and 5 days for tibial bone marrow. Inhibition of 3H-deoxyuridine incorporation into DNA was similar for 50, 100, and 150 mg/kg doses both in tumor and in host organs, but recovery of 3H-deoxyuridine incorporation and DNA content of host organs began later with the higher doses of 5-fluorouracil. Maximal incorporation of 3H-deoxyuridine into DNA was observed on day 4 for intestine, day 8 for marrow, and day 9 for thymus after treatment with 150 mg/kg 5-fluorouracil. Animal lethality following the second of two 150 mg/kg injections of 5-fluorouracil was related to the extent of recovery of intestinal mucosa and bone marrow at the time of the second injection. Survival decreased to 0% for normal rats when the interval between injections was 3-4 days, improved at 5 days and was 100% when the interval was 10-11 days.     

Experimental chemotherapy of schistosomiasis mansoni. XIII. Activity of praziquantel, an isoquinoline-pyrazino derivative, on mice, hamsters and Cebus monkeys.

In mice experimentally infected with Schistosoma mansoni, praziquantel (2-cyclohexylcarbonyl-1,3,4,6,7,11b-hexahydro-2H-pyrazino[2,1-a]isoquinoline-4-one), administered orally at the levels of 100 and 50 mg/kg, for 5 consecutive days, produces oogram changes in all animals and a pronounced hepatic shift of schistosomes (97.1 and 89.1, respectively). At lowest levels (12.5 and 6.3 mg/kg), alterations in the oogram could still be detected, although hepatic shift of schistosomes was no more evident. After a single intramuscular injection, the results obtained paralleled those observed with a single-dose oral treatment. The hepatic shift was only moderate at 200 and 100 mg/kg and the percentages of worms retained in the liver, after perfusion, were particularly low. When nasal route in a 1-day regimen was used, the results obtained were slightly less evident as compared with those observed by oral route (5-day schedule). Considering the percentage of oogram changes, the degree of hepatic shift of schistosomes and the percentage of worms fixed in the liver, the antischistosomal activity of praziquantel was greater in hamsters than in mice. Actually, a daily dose as low as 12.5 mg/kg, administered for 5 consecutive days, was sufficient to shift 60.4% of the worms towards the liver and to produce alterations of the oogram in 60% of the animals. In Cebus monkeys orally treated with 10 and 20 mg/kg of praziquantel, given 3 times within a single day (total doses of 30 and 60 mg/kg, respectively), a remarkable reduction in worm burden was observed. A single oral or intramuscular dose of 100 mg/kg was found to be curative. One Cebus doses with 100 mg/kg, by nasal spray, was found to harbor only female worms at autopsy performed 69 days after treatment.     

Antiplatelet activity of the long-acting thromboxane receptor antagonist BMS 180,291 in monkeys.

The effects of the novel TxA2/prostaglandin endoperoxide (TP) receptor antagonist BMS 180,291 on platelet reactivity was determined ex vivo in conscious African green monkeys. Platelet aggregation responses to U-46,619 were decreased 50% and 100% at 23 to 24 hrs after BMS 180,291 oral doses of 1 and 3 mg/kg, respectively. In addition to inhibiting aggregation, a 3 mg/kg oral dose of BMS 180,291 also produced an 11 +/- 3-fold shift to the right in the U-46,619 concentration-response relationship for platelet shape change at 24 hrs after dosing. When the 3 mg/kg oral dose was continued for 11 days, the shift in this concentration-response relationship increased to 26 +/- 10- and 93 +/- 30-fold at 24 hrs after the 8th and 11th doses, respectively. This progressive inhibition corresponds to 93 +/- 3 and 99 +/- 1% blockade of platelet TP-receptors responsible for shape change, respectively. Comparable levels of TP-receptor blockade have been previously correlated with antithrombotic and antiischemic activities of TP-receptor antagonists in vivo. Platelet reactivity to U-46,619 had completely recovered on the 7th day after the final dose of BMS 180,291, indicating effective elimination from the circulation over this interval. In separate experiments, a 3-mg/kg i.v. dose of BMS 180,291 produced only marginal and transient hemodynamic effects in anesthetized African green monkeys. Overall, these data demonstrate that BMS 180,291 given orally once a day produces a sustained and therapeutically-relevant level of TP-receptor antagonism.     

Effects of aromatic cationic molecules on bovine viral diarrhea virus and embryonic development

Bovine viral diarrhea virus (BVDV) has been shown to replicate in embryo culture systems and remain associated with bovine embryos developing in vitro. In this study, novel antiviral agents were evaluated for capability to inhibit replication of BVDV without affecting embryonic development. Serial concentrations of 2-[5(6)-{2-imidazolinyl}-2-benzimidazolyl]-5-(4-aminophenyl)furan (DB456) or 2-(4-[2-imidazolinyl]phenyl)-5-(4-methoxyphenyl)furan (DB606) were prepared in IVC medium. Then, bovine uterine tubal epithelial cells (UTC) were placed in IVC media with varying concentrations of DB456 or DB606. Within 1h, a genotype I or II strain of BVDV was added to the cultures. Cultures were maintained for 7 days. Infectious virus was quantitated in IVC media collected on days 3 and 7 and in UTC lysates harvested on day 7. The effective antiviral concentrations of DB606 were much lower than effective antiviral concentrations of DB456. In subsequent experiments, IVF presumptive zygotes were cultured in IVC medium with or without DB456 or DB606 at multiple concentrations for 7 days to evaluate effect of the compound on conceptus development. On day 7, stage of embryonic development was observed, and blastocysts were harvested and stained using Hoechst 33342 to enumerate embryonic cells. While DB456 inhibited blastocyst development, DB606 at 20 times the effective antiviral concentration did not hinder blastocyst development or reduce the mean number of cells per blastocyst. These preliminary results indicated that bovine embryo cultures might be safely supplemented with effective concentrations of an antiviral agent.