Virulizin-2gamma, a novel immunotherapeutic agent, in treatment of human pancreatic cancer xenografts.

Virulizin-2gamma, a novel biological response modifier extracted from bovine bile, has shown in clinical studies a significant antitumor activity against pancreatic cancer. We report here the results of preclinical evaluation of Virulizin-2gamma in treatment of human pancreatic cancer xenograft in nude mice. In this in vivo study, 14 daily bolus intraperitoneal administrations of Virulizin-2gamma (0.2 ml/mouse/day) significantly inhibited the growth of BxPC-3 human pancreatic tumor xenografts, with T/C value of 60%. Virulizin-2gamma also potentiated the antitumor activity of gemcitabine (120 mg/kg x4, q3d) in this tumor model. The combination therapy resulted in T/C values of 26% compared to gemcitabine alone (T/C 33%). In addition, based on body weight observation, no signs of toxicity related to treatment with Virulizin-2gamma, either as a single agent or when combined with gemcitabine were found. Virulizin-2gamma was well tolerated by the mice. The data from in vitro studies revealed that Virulizin-2gamma did not have direct cytotoxicity against cultured tumor cell lines, indicating that the in vivo antitumor activity is likely due to its immunomodulating effects on host immune cells. These preclinical results supported the safety and efficacy observed in clinical studies and indicated that Virulizin-2gamma is a promising immunotherapeutic agent for treatment of pancreatic cancer and worthy of further clinical evaluation.

Disposition of radioactivity in fischer 344 rats after single and multiple inhalation exposure to [(14)C]Octamethylcyclotetrasiloxane ([(14)C]D(4)).

The retention, distribution, metabolism, and excretion of [(14)C]octamethylcyclotetrasiloxane (D(4)) were studied in Fischer 344 rats after single and multiple exposures to 7, 70, or 700 ppm [(14)C]D(4). Subset groups were established for body burden, distribution, and elimination. Retention of inhaled D(4) was relatively low (5-6% of inhaled D(4)). Radioactivity derived from [(14)C]D(4) inhalation was widely distributed to tissues of the rat. Maximum concentrations of radioactivity in plasma and tissues (except fat) occurred at the end of exposure and up to 3 h postexposure. Maximum concentrations of radioactivity in fat occurred as late as 24 h postexposure. Fat was a depot, elimination of radioactivity from this tissue was much slower than from plasma and other tissues. With minor exceptions, there were no consistent gender effects on the distribution of radioactivity and the concentrations of radioactivity were nearly proportional to exposure concentration over the exposure range. Excretion of radioactivity was via exhaled breath and urine, and, to a much lesser extent, feces. Urinary metabolites included dimethylsilanediol and methylsilanetriol plus five minor metabolites. Relative abundance of these metabolites was the same from every test group. Elimination was rapid during the first 24 h after exposure and was slower thereafter (measured up to 168 h postexposure). In singly-exposed female (but not male) rats, small dose-dependent shifts in elimination pathways were seen. After multiple exposures, the elimination pathways were dose- and gender-independent. These data define possible pathways for metabolism of D(4) and allow estimation of the persistence of D(4) and/or its metabolites in rats.

Pharmacokinetics and disposition of methyl t-butyl ether in Fischer-344 rats.

Methyl t-butyl ether (MTBE) is a commonly used octane booster in gasoline. This study examines the pharmacokinetics and disposition of MTBE in Fischer-344 rats after i.v., oral, dermal and inhalation routes of administration. Groups of male and female rats were given single i.v. (40 mg kg-1), oral (40 and 400 mg kg-1) and dermal (40 and 400 mg kg-1 in occluded chambers) doses of [14C]MTBE. For inhalation studies, rats were exposed nose-only for 6 h to low (400 ppm), high (8000 ppm) and repeated daily 6-h low (400 ppm x 15 days) chamber concentrations of [14C]MTBE. Blood, expired air, and excreta (urine and feces) were collected at selected times up to 7 days post-dose and quantified for 14C content. Plasma concentrations of MTBE and t-butyl alcohol (TBA) were quantified and mean values used for pharmacokinetic analysis. The mean total recoveries of 14C ranged from 91 to 105%. Methyl t-butyl ether was rapidly and completely absorbed after oral and inhalation exposures; dermal absorption was low. After all routes, MTBE was rapidly eliminated from blood (ti = 0.5 h) by exhalation and metabolism to TBA. At the high doses, metabolism was saturated and the proportion of renal 14C excretion decreased relative to the pulmonary route. At 48 h post-exposure, virtually all of the 14C was eliminated. The major metabolites recovered in urine were 2-methyl-1,2-propanediol and alpha-hydroxyisobutyric acid. There were no significant gender or route-dependent differences in the pharmacokinetics and disposition of MTBE.

Pharmacokinetics and disposition of the lipid-lowering drug acifran in normal subjects and in patients with renal failure.

The pharmacokinetics and metabolic fate of the antihyperlipidemic drug acifran were assessed after a single oral dose of the 14C-labeled drug to healthy male volunteers. Peak serum acifran and radioactivity concentrations were attained 1 to 2 hours after dosing, and the drug was eliminated with a half-life of 1.6 hours. Virtually all of the recovered dose was excreted in the urine. All of the serum and urinary radioactivity was caused by unconjugated acifran. In patients with moderate chronic renal failure, the binding of acifran to plasma proteins was decreased, and the plasma concentrations of total and unbound drug were greater than those of healthy subjects. Renal failure substantially reduced the plasma and renal clearance of total and particularly of unbound acifran, moderately reduced its volume of distribution, and increased its elimination half-life from 1.4 to 1.7 hours to 5.7 hours. The results show that acifran is very well absorbed, is rapidly eliminated, is excreted in the urine, and does not undergo any detectable biotransformation in healthy human subjects.

The metabolic disposition of acifran, a new antihyperlipidemic agent, in rats and dogs.

The metabolic disposition of the antihyperlipidemic agent acifran (AY-25, 712) was determined in rats and dogs. The synthesis of 14C-labelled acifran is described. Serum levels of 14C and acifran were measured in rats and dogs after p.o. and i.v. administration of 14C-acifran at a dose of 10 mg/kg. Over 80% of the 14C in serum was due to acifran. The drug was rapidly absorbed and the pharmacokinetics, unaffected by increasing the dose or by daily multiple doses, were characterized by a two-compartment open model. Food reduced the bioavailability of acifran by 27% in the dog. About 65% of the dose was absorbed in rats, and at least 88% in dogs. The elimination t 1/2 of acifran from serum was 1.5 h in the rat and 3 h in the dog. Acifran was partially bound to serum proteins, man greater than rat greater than dog; the drug was found to displace protein-bound warfarin in rat and dog, but not in human serum. Radioactivity did not tend to accumulate in tissues, except for the kidney, where the 14C concentration was five times higher than in the serum; elimination of 14C from all the tissues was similar to that from serum. Most of the absorbed dose was excreted in the urine. Acifran did not undergo enterohepatic circulation in the rat. Virtually all the urinary 14C in both species was due to the unchanged compound. In conclusion, the disposition of acifran was similar in rats and dogs. The drug was rapidly absorbed and eliminated, and underwent no detectable biotransformation. There was no tissue retention and excretion was mainly in the urine.

Disposition and biotransformation of 14C-etodolac in man.

Four human subjects were given a capsule containing 200 mg of 14C-etodolac. At the peak (two hours after dosing), most of the radioactivity in serum was due to etodolac; subsequently, metabolites gradually appeared. The elimination half-life of etodolac from serum averaged six hours. Etodolac was greater than 99% bound to human serum proteins. An average of 73% of the dose was excreted in the urine and 14% in faeces within seven days, with 61% appearing in the urine during the first 24 h. Microbial transformation of etodolac was employed to biosynthesize sufficient amounts of two urinary metabolites to facilitate structure elucidation. Five metabolites, representing 65% of the radioactivity in urine collected 0-24 h after dosing (61% of the dose was excreted in urine within 24 h), were isolated and characterized by t.l.c., g.c., h.p.l.c., n.m.r (1H and 13C) and m.s. Most of the identified urinary components were conjugates of etodolac and three hydroxylated metabolites (6-hydroxyetodolac, 7-hydroxyetodolac and 8-(1-hydroxyethyl)etodolac). Two metabolites were identified as glucuronyl ester conjugates of etodolac and 7-hydroxyetodolac; the former represented about 20% of the urinary radioactivity. False positive tests for bilirubin in urine of patients treated with etodolac were found to be due to the two phenolic metabolites.

Metabolic disposition and pharmacokinetics of the aldose reductase inhibitor tolrestat in rats, dogs, and monkeys.

The metabolic disposition and pharmacokinetics of the aldose reductase inhibitor tolrestat were studied in rats, dogs, and assamese and capuchin monkeys. In addition, the ocular penetration of tolrestat was examined in rabbits. The bioavailability of tolrestat was 81% in rats and 68% in dogs. In contrast to rats, a major proportion of the serum 14C in dogs and monkeys was due to unchanged drug. The terminal elimination half-life of tolrestat in serum was 3.5 hr in rats, 11 hr in dogs, and 9 hr in monkeys; in both dogs and monkeys, the total body clearance was 200 ml/kg X hr, and the volume of distribution was 3 liters/kg. In rats and dogs, serum tolrestat concentrations were similar after single and multiple po doses, and were linearly dose-related up to 25 mg/kg, but increased disproportionately at higher doses. Tolrestat was at least 98% bound to rat and dog serum proteins. Except for organs associated with absorption and elimination, tissue 14C levels were lower than in serum of rats and capuchin monkeys, and there was no tissue 14C accumulation. The 14C from topically applied 14C-tolrestat readily penetrated into the eyes of rabbits. Liver microsomal cytochrome P-450 was virtually unaltered in tolrestat-treated rats. Tolrestat (and/or its metabolites) underwent enterohepatic circulation in rats. Most of the 14C from 14C-tolrestat administered po and iv to rats and dogs was excreted in the feces. Based on 14C excretion, the absorption of tolrestat was 84% in rats and 82% in dogs.(ABSTRACT TRUNCATED AT 250 WORDS)

Distribution and excretion of furobufen in rats and dogs.

Groups of male rats and dogs were given single doses of 50 mg of 14C-furobufen per kg orally or intravenously. In rats, tissue radioactivity levels were generally lower than that of serum. Radioactivity accumulated in and was retained by white adipose tissue. The radioactivity in fat was due to a conjugate of dibenzofuranacetic acid, the major metabolite of furobufen. Approximately one-half of the dose was excreted each in the urine and feces of rats after oral and intravenous administration of 14C-furobufen. A similar excretion pattern was observed in dogs after an oral dose.

The metabolic disposition of etodolac in rats, dogs, and man.

The metabolic disposition of etodolac (etodolic acid) was studied after oral and intravenous administration of the 14C-labeled or unlabeled drug to rats and dogs, and after oral administration of the drug to man. In all species, peak serum drug levels were attained within 2 hr after dosing. In rats and dogs, virtually all of the oral dose was absorbed; etodolac represented 95% of the serum radioactivity in rats and 75% in dogs. Serum levels in all species were generally dose-related. The elimination portion of the serum drug concentration/time curves was characterized by several peaks, which in rats were shown to be due to enterohepatic circulation. Tissue distribution studies in rats showed that radioactivity localized primarily in blood vessels, connective tissue, and highly vascularized organs (liver, heart, lung, and kidney) and that the rate of elimination of radioactivity from tissues was similar to that found in the serum. The apparent elimination half-life of etodolac averaged 17 hr in rats, 10 hr in dogs, and 7 hr in man. Etodolac was extensively bound to serum proteins. Liver microsomal cytochrome P-450 levels were unaltered in rats given etodolac daily for 1 week. The primary route of excretion in rats and dogs was via the bile into the feces. Preliminary biotransformation studies in dogs showed the presence of the glucuronide conjugate of etodolac in bile, but not in the urine. Glucuronide conjugates were not seen in the rat. Four hydroxylated metabolites in rat bile were tentatively identified. It was concluded that, in rats and dogs, etodolac is well absorbed, is subject to extensive enterohepatic circulation, undergoes partial biotransformation, and is excreted primarily into the feces.U

Studies on the disposition of diosgenin in rats, dogs, monkeys and man.

Rats, dogs and squirrel monkeys were given a single oral dose of [4-(14)C]diosgenin. Virtually all of the radioactivity was excreted in the feces. All of the absorbed radioactivity was eliminated via the bile. The percent of dose absorbed decreased with increasing dose. The amount of radioactivity in livers of rats given [4-(14)C]diosgenin was less than that after [4-(14)C]cholesterol, but more than after [4-(14)C]beta-sitosterol. Absorbed radioactivity in rats distributed into tissues, most notably the liver, adrenals, and walls of the gastrointestinal tract. No serum diosgenin was detected after a single large dose to rats and dogs. After multiple doses (100 mg/kg/day for 4 weeks) of diosgenin to dogs, up to 15 micrograms/ml of unchanged diosgenin was found in serum. Serum from human subjects receiving 3 g/day of diosgenin for 4 weeks contained less than 1 microgram/ml of unchanged drug. After a single dose of [14C]diosgenin, several metabolites were detected in the bile of rats and dogs; the pattern of metabolites was dissimilar in the two species. No diosgenin or 7-hydroxydiosgenin was found. One of the major biliary metabolites was diosgenin monohydroxylated in the F ring, but the location of the hydroxyl group was different in the two species. Although rat caecal contents were capable of reducing diosgenin to smilagenin in vitro, no smilagenin was present in the feces of rats given chow supplemented with diosgenin. It was concluded that diosgenin is poorly absorbed in the species tested, and that the amount which is absorbed undergoes extensive biotransformation.

Clofibrate and clofibric acid: comparison of the metabolic disposition in rats and dogs.

In rats, equimolar oral doses of [14C]clofibrate and [14c]clofibric acid produced essentially the same profiles of blood levels, tissue distribution and excretion of radioactivity. Both compounds were completely absorbed, and all radioactivity found in the serum was due to clofibric acid (CPIB). Tissues contained readily detectable radioactivity levels, but the concentration was generally lower than in serum. A large proportion of CPIB in liver, heart, kidney, fat and muscle was associated with intracellular space. In rat urine, CPIB was present both free and conjugated with glucuronic acid. Approximately 97% of the serum CPIB was not conjugated. Identical decreases in serum lipids and hepatic cholesterol synthesis were observed in rats treated for 1 week with either compound. In dogs, the serum contained 40% more radioactivity after [14C]clofibric acid than after an equimolar oral dose of [14C]clofibrate; approximately 88% of the serum radioactivity was due to CPIB. Some biliary excretion was detected. The extent of binding to serum protein varied with concentration of CPIB and with the species; the affinity was in the order man greater than dog greater than rat. The results demonstrate that clofibric acid and clofibrate are metabolically and pharmacologically equivalent in rats, but not in dogs. The data are in accordance with the view that the pharmacological activity of clofibrate is due to clofibric acid.