The Kv1.3 channel is a recognized target for pharmaceutical development to treat autoimmune diseases and organ rejection. ShK-186, a specific peptide inhibitor of Kv1.3, has shown promise in animal models of multiple sclerosis and rheumatoid arthritis. Here, we describe the pharmacokinetic-pharmacodynamic relationship for ShK-186 in rats and monkeys. The pharmacokinetic profile of ShK-186 was evaluated with a validated high-performance liquid chromatography-tandem mass spectrometry method to measure the peptide's concentration in plasma. These results were compared with single-photon emission computed tomography/computed tomography data collected with an 111 In-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid-conjugate of ShK-186 to assess whole-blood pharmacokinetic parameters as well as the peptide's absorption, distribution, and excretion. Analysis of these data support a model wherein ShK-186 is absorbed slowly from the injection site, resulting in blood concentrations above the Kv1.3 channelblocking IC 50 value for up to 7 days in monkeys. Pharmacodynamic studies on human peripheral blood mononuclear cells showed that brief exposure to ShK-186 resulted in sustained suppression of cytokine responses and may contribute to prolonged drug effects. In delayed-type hypersensitivity, chronic relapsing-remitting experimental autoimmune encephalomyelitis, and pristane-induced arthritis rat models, a single dose of ShK-186 every 2 to 5 days was as effective as daily administration. ShK-186's slow distribution from the injection site and its long residence time on the Kv1.3 channel contribute to the prolonged therapeutic effect of ShK-186 in animal models of autoimmune disease.

1. Linezolid (ZYVOX), the first of a new class of antibiotics, the oxazolidinones, is approved for treatment of Gram-positive bacterial infections. 2. The aim was to determine the absorption, distribution, metabolism and excretion (ADME) of linezolid in mouse, rat and dog in support of preclinical safety studies and clinical development. 3. Conventional replicate study designs were employed in animal experiments, and biofluids were assayed by HPLC or HPLC-MS. 4. Linezolid was rapidly absorbed after p.o. dosing with an p.o. bioavailability of > 95% in rat and dog, and > 70% in mouse. Twenty-eight-day i.v./p.o. toxicokinetic studies in rat (20-200mg kg(-1) day(-1)) and dog (10-80 mg kg(-1) day(-1)) revealed neither a meaningful increase in clearance nor accumulation upon multiple dosing. 5. Linezolid had limited protein binding (<35%) and was very well distributed to most extravascular sites, with a volume of distribution at steady-state (V(ss)) approximately equal to total body water. 6. Linezolid circulated mainly as parent drug and was excreted mainly as parent drug and two inactive carboxylic acids, PNU-142586 and PNU-142300. Minor secondary metabolites were also characterized. In all species, the clearance rate was determined by metabolism. 7. Radioactivity recovery was essentially complete within 24-48 h. Renal excretion of parent drug and metabolites was a major elimination route. Parent drug underwent renal tubular reabsorption, significantly slowing parent drug excretion and allowing a slow metabolic process to become rate-limiting in overall clearance. 8. It is concluded that ADME data were relatively consistent across species and supported the rat and dog as the principal non-clinical safety species.

A new and promising group of antibacterial agents, collectively known as the oxazolidinones and exemplified by linezolid (PNU-100766, marketed as Zyvox), have recently emerged as important new therapeutic agents for the treatment of infections caused by Gram-positive bacteria. Because of their significance, extensive synthetic investigations into the structure-activity relationships of the oxazolidinones have been conducted at Pharmacia. One facet of this research effort has focused on the identification of bioisosteric replacements for the usual oxazolidinone A-ring. In this paper we describe studies leading to the identification of antibacterial agents incorporating a novel isoxazoline A-ring surrogate. In a gratifying result, the initial isoxazoline analogue prepared was found to exhibit in vitro antibacterial activity approaching that of the corresponding oxazolidinone progenitor. The synthesis and antibacterial activity profile of a preliminary series of isoxazoline analogues incorporating either a C-C or N-C linkage between their B- and C-rings will be presented. Many of the analogues exhibited interesting levels of antibacterial activity. The piperazine derivative 54 displayed especially promising in vitro activity and in vivo efficacy comparable to the activity and efficacy of linezolid.

The kinetics of nornicotine and anabasine nitrosation, studied in aqueous solution, obeyed equations typical for the nitrosation of aliphatic secondary amines, with third-order stoichiometric rate constants of 1.15 (nornicotine) and 0.86 (anabasine) M-2 sec-1. The similarity of the two rate constants suggested that the nitrosonornicotine occurring in tobacco arises from nicotine rather than nornicotine, because tobacco contains anabasine but apparently does not contain nitrosoanabasine. The high rate constants suggested that in vivo nitrosation of these secondary amines may constitute a hazard to tobacco smokers and chewers, in addition to that presented by preformed nitrosonornicotine.

The in vivo production of nitrosoureas from food constituents and nitrite might contribute to the etiology of gastric cancer. Food extracts were treated with nitrite at pH 1 and left a pH 0 to effect denitrosation. The resulting alkylureas (which may have arisen from intermediate alkylnitrosoureas) were purified by cation-exchange, paper, and high-pressure liquid chromatography. Identity of most alkylurea samples was confirmed by high-resolution mass spectrometry. A smoked, dried bonito fish product from Japan yielded an average of 340 µ (25 mg) of methylurea (MU)/kg of fish; an intermediate product wasshown to be methylnitrosourea. We obtained n-propylurea, 3-butenylurea, and [ (4?)-hydroxybutyl] urea from dungeness crab and (mainly) 3-butenylurea from Alaskan king crab and slipper lobster tail. Fried

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Three once-daily oral doses of 0.2 mg/kg [(14)C]dirlotapide were administered to beagle dogs to study the absorption, distribution, metabolism, and excretion of dirlotapide. Mean (14)C recovered at 2.5 and 4.5 h after the last dose was 90%. Mean (14)C in urine, bile, and feces was <1%, 1.7%, and 56% of the dose, respectively. In tissues, 26% of the (14)C dose was present in the gastrointestinal tract, 6.0% in liver, and <1% each in kidney, gall bladder, heart, and brain. To further characterize drug disposition, a single 2.5-mg/kg oral dose of [(14)C]dirlotapide was administered to beagle dogs. More than 84% of the dose had been eliminated by 72 h in feces, with 21% of the dose present in feces as parent dirlotapide. Less than 1% of the dose was excreted in urine. In bile collected during the first 24-h postdose from three dogs, 32% and 11% of the (14)C dose was present in samples from male and female dogs, respectively. Based upon metabolite profiling of plasma, excreta, and bile samples, dirlotapide was extensively metabolized to more than 20 metabolites. Biliary/fecal excretion and the potential for enterohepatic recycling of metabolites are suggested.

cm-1). Distillation gave 5 g (19%) of a thick yellow oil, bp 132-138°(0.25 mm). The ir spectrum displayed significant peaks at 3050 (shoulder), 3000, 2940, 1700, 1650, 1610, 1370, and 1240 cm-1. The nmr spectrum indicated the presence of the imino ester and some impurity (ca. 15%) that could not be removed by repeated distillation. The good chemical analysis indicates that the impurity is an isomer of the imino ester (but it is not the ketenimine). The nmr displayed peaks ( ™) , at 7.0 (broad multiplet, 5 H) for the phenyl protons, 6.72 (singlet, 1 H)