Pharmacokinetics of BAY 59-7939--an oral, direct Factor Xa inhibitor--in rats and dogs.

The pharmacokinetics of BAY 59-7939 - a novel, oral, direct Factor Xa inhibitor - were investigated in rats and dogs in support of preclinical safety studies and clinical development. BAY 59-7939 was rapidly absorbed after oral dosing, with an absolute bioavailability of 57-66% in rats, and 60-86% in dogs. Plasma pharmacokinetics of BAY 59-7939 were linear across the investigated dose range (1-10 mg kg(-1) in rats, 0.3-3 mg kg(-1) in dogs). Plasma clearance was low: 0.4 l kg(-1) h(-1) in rats and 0.3 l kg(-1) h(-1) in dogs; volume of distribution (V(ss)) was moderate: 0.3 l kg(-1) in rats, and 0.4 l kg(-1) in dogs. The elimination half-life after oral administration was short in both species (0.9-2.3 h). Whole-body autoradiography showed moderate tissue affinity. No retention or small volume enrichments of BAY 59-7939-related radioactivity were observed. The plasma-protein binding of BAY 59-7939 was high, species dependent and fully reversible. BAY 59-7939 was rapidly excreted in rats and dogs, and was not irreversibly retained. A dual mode of excretion (biliary/faecal and renal) was observed. In summary, BAY 59-7939 had a favourable, predictable pharmacokinetic profile, with high oral bioavailability and a dual route of excretion.

In vitro and in vivo studies of the novel antithrombotic agent BAY 59-7939--an oral, direct Factor Xa inhibitor.

BAY 59-7939 is an oral, direct Factor Xa (FXa) inhibitor in development for the prevention and treatment of arterial and venous thrombosis. BAY 59-7939 competitively inhibits human FXa (K(i) 0.4 nm) with > 10 000-fold greater selectivity than for other serine proteases; it also inhibited prothrombinase activity (IC(50) 2.1 nm). BAY 59-7939 inhibited endogenous FXa more potently in human and rabbit plasma (IC(50) 21 nm) than rat plasma (IC(50) 290 nm). It demonstrated anticoagulant effects in human plasma, doubling prothrombin time (PT) and activated partial thromboplastin time at 0.23 and 0.69 microm, respectively. In vivo, BAY 59-7939 reduced venous thrombosis (fibrin-rich, platelet-poor thrombi) dose dependently (ED(50) 0.1 mg kg(-1) i.v.) in a rat venous stasis model. BAY 59-7939 reduced arterial (fibrin- and platelet-rich) thrombus formation in an arteriovenous (AV) shunt in rats (ED(50) 5.0 mg kg(-1) p.o.) and rabbits (ED(50) 0.6 mg kg(-1) p.o.). Slight inhibition of FXa (32% at ED(50)) reduced thrombus formation in the venous model; to affect arterial thrombosis in the rat and rabbit, stronger inhibition of FXa (74%, 92% at ED(50)) was required. Calculated plasma levels in rabbits at the ED(50) were 14-fold lower than in the rat AV shunt model, correlating with the 14-fold lower IC(50) of FXa inhibition in rabbit compared with rat plasma; this may suggest a correlation between FXa inhibition and antithrombotic activity. Bleeding times in rats and rabbits were not significantly affected at antithrombotic doses (3 mg kg(-1) p.o., AV shunt). Based on these results, BAY 59-7939 was selected for clinical development.

Inhibition of human hepatitis B virus (HBV) by a novel non-nucleosidic compound in a transgenic mouse model.

BAY 41-4109 is a member of a class of heteroaryl-pyrimidines that was recently identified as potent inhibitors of human hepatitis B virus (HBV) replication. We have investigated the antiviral activity of BAY 41-4109 (methyl (R)-4-(2-chloro-4-fluorophenyl)-2-(3,5-difluoro-2-pyridinyl)-6-methyl-1,4-dihydro-pyrimidine-5-carboxylate) in HBV-transgenic mice (Tg [HBV1.3 fsX(-)3'5']). Bay 41-4109 was administered per os using different schedules (b.i.d. or t.i.d. for up to 28 days) and dosages ranging from 3 to 30 mg/kg. The compound reduced viral DNA in the liver and in the plasma dose-dependently with efficacy comparable to 3TC. In contrast to 3TC-treated mice, we found a reduction of cytoplasmic hepatitis B virus core antigen (HBcAg) in liver sections of BAY 41-4109-treated mice, which indicated a different mode of action. Pharmacokinetic studies in mice have shown rapid absorption, a bioavailability of 30% and dose-proportional plasma concentrations. We conclude that BAY 41-4109 is a new anti-HBV drug candidate.

The oral efficacy of vardenafil hydrochloride for inducing penile erection in a conscious rabbit model.

PURPOSE: Inhibiting cyclic guanosine monophosphate metabolism may induce penile erection during concomitant nitric oxide production. Vardenafil hydrochloride is a new, highly selective, potent cyclic guanosine monophosphate phosphodiesterase 5 inhibitor. We determined the oral effectiveness of vardenafil in a simple and quantitative conscious rabbit model. MATERIALS AND METHODS: Vardenafil was given orally to conscious rabbits. Erection was assessed in a time dependent manner by measuring the length of the uncovered penile mucosa. Erection was evaluated in the absence and presence of intravenous sodium nitroprusside, a nitric oxide donor. RESULTS: Vardenafil induced dose dependent penile erection in conscious rabbits after the oral administration of 1 to 30 mg./kg. The efficacy of vardenafil was potentiated and effective doses were significantly reduced by the simultaneous administration of sodium nitroprusside. CONCLUSIONS: The effect of vardenafil on penile erection after oral administration was clearly demonstrated in the conscious rabbit model. The time course and early onset of activity indicate that it may be useful for treating erectile dysfunction. Potentiation of the effect by the nitric oxide donor sodium nitroprusside implies that it would have enhanced activity during sexual arousal, when nitric oxide is produced endogenously. The clinical development of this product for erectile dysfunction is proceeding.

Kinetic and analytic investigations on the formation of N-nitroso-N-methyl-N-cyclohexylamine from bromhexine and nitrite.

Bromhexine (N-methyl-N-cyclohexyl-(2-amino-3,5-dibromobenzyl)-ammoniumhydr ochloride) forms N-nitroso-N-methyl-N-cyclohexylamine (NMCA) under the conditions of the WHO Nitrosation Assay Procedure (NAP-test). The formation kinetics of this compound was investigated. The formation of NMCA depends on the square of the nitrite concentration. The reaction has a narrow pH-optimum at pH 3. The reaction is quick: After 1 h about 70% of the maximum amount of NMCA is formed. To study this reaction kinetics sensitive assays with a detection limit up to 0.5 ng/ml NMCA were developed. The stability of the components of the system, especially that of NMCA and nitrite, were further studied. The latter is rather instable under conditions found in an acidic stomach.

Nitrosation of bromhexine and aminophenazone in gastric juice after high nitrate loading in the diet. An ex-vivo/in-vitro study in humans.

In an ex-vivo study, nitrosation of bromhexine (N-methyl-N-cyclohexyl-(2-amino-3,5-dibromobenzyl)-ammonium hydrochloride) in human gastric fluid under conditions of high dietary nitrate intake was investigated. 26 healthy volunteers received 200 mg of nitrate in a vegetable during a standard breakfast. Nitrite values in saliva were significantly increased 2 to 3 h after nitrate intake. In contrast, nitrite levels in gastric fluid sampled 3 h after nitrate intake remained in the low concentration range of less than or equal to 1.7 micrograms/No2-/ml. Incubation of gastric fluid samples at 37 degrees C with the recommended maximum single oral dose of bromhexine (16 mg/100 ml) or an equimolar concentration of aminophenazone revealed in 4/26 cases formation of N-nitrosomethylcyclohexylamine from bromhexine at barely detectable levels. In contrast, aminophenazone generated N-nitrosodimethylamine at a very high rate, resulting in yields of greater than 50% in several samples. In view of the average daily background exposure to preformed nitrosamines in foods (0.5-1 microgram/capita), according to these results the possible contribution of in-vivo nitrosation of bromhexine corresponds at best to 10% in addition to the daily background exposure and therefore can be regarded as negligible.

In-vitro and in-vivo formation of N-nitrosomethylcyclohexylamine from bromhexin and sodium nitrite, and DNA methylation in rats.

After oral administration of a commercial bromhexin (N-methyl-N-cyclohexyl(2-amino-3,5-dibrombenzyl)ammonium chloride) solution (1-90 mg/kg) together with sodium nitrite (1-90 mg/kg) to female Wistar rats, ring-hydroxylated metabolites of N-nitrosomethyl-cyclohexylamine (NMCA) were excreted in urine as glucuronide/sulfate conjugates. When [14C-methyl]-bromhexin (30 mg/kg) was given intragastrically together with sodium nitrite (30 mg/kg), alkylated DNA adducts were detected in liver and oesophagus. Gastric juice of 75 healthy human volunteers (fasted, then ingesting up to 200 mg nitrate) was incubated in vitro with bromhexin (16 mg/100 ml). In only one sample, 50 ng NMCA/100 ml were formed.