Timothy D. Spitzer

Preclinical pharmacology of GW280430A (AV430A) in the rhesus monkey and in the cat: a comparison with mivacurium.

BackgroundNo replacement for succinylcholine is yet available. GW280430A (AV430A) is a representative of a new class of nondepolarizing neuromuscular blocking drugs called asymmetric mixed-onium chlorofumarates. It undergoes rapid degradation in plasma by chemical hydrolysis and inactivation by cysteine adduction, resulting in a very short duration of effect. The neuromuscular, cardiovascular, and autonomic pharmacology of GW280430A is compared herein with that of mivacurium. MethodsAdult male rhesus monkeys and adult male cats were anesthetized with nitrous oxide–oxygen–halothane and chloralose–pentobarbital, respectively. The neuromuscular blocking properties of GW280430A and mivacurium were compared at a stimulation rate of 0.15 Hz in the extensor digitorum of the foot (monkey) and the tibialis anterior (cat). Sympathetic responses were assayed in the cat in the nictitating membrane preparation, and vagal effects were evaluated in the cat via observation of bradycardic responses after stimulation of the cervical right vagus nerve. ResultsGW280430A and mivacurium were equipotent in the monkey (ED95 was 0.06 mg/kg in each case). GW280430A was half as potent as mivacurium in the cat. The total duration of action of GW280430A was less than half that of mivacurium in the monkey; recovery slopes were more than twice as rapid. The 25–75% recovery index of GW280430A did not vary significantly after various bolus doses or infusions, averaging 1.4–1.8 min in the monkey, significantly shorter than the same time interval (4.8–5.7 min) for mivacurium. Dose ratios for autonomic versus neuromuscular blocking properties in the cat were greater than 25 for both GW280430A and mivacurium. The ratio ED Hist:ED95 Neuromuscular Block in the monkey was significantly greater (approximately 53 vs. 13) for GW280430A, indicating approximately four times less relative prominence of the side effects of skin flushing and decrease of blood pressure, which are associated with release of histamine. ConclusionsThese experiments show a much shorter neuromuscular blocking effect and much-reduced side effects in the case of GW280430A vis-à-vis mivacurium. These results, together with the novel chemical degradation of GW280430A, suggest further evaluation in human subjects.

The confromational behaviour of the cardiac glycoside digoxin as indicated by NMR spectroscopy and molecular dynamics calculations

The 1H- and 13C-NMR spectra of digoxin in solution in Me2SO-d6 have been assigned completely. Measurement of the 3JC,H values has enabled estimation of the torsional angles involving the bonds linking the digitoxose residues, between the inner digitoxose and the genin unit, and for the unsaturated gamma-lactone ring. These values have been supplemented by 1H-1H NOE data. In general, there is good agreement between the conformations in solution (NMR data) and the solid state (X-ray data), and that derived from theoretical modelling which shows evidence of conformational flexibility. The major difference occurs for the torsion between the genin and the innermost digitoxose residue where molecular dynamics predict the presence of two conformations, one similar to that seen by NMR and the other similar to the X-ray structure.

Fungal Metabolites as Potent Protein Kinase Inhibitors: Identification of a Novel Metabolite and Novel Activities of Known Metabolites

Abstract: A novel undecylresorcinol dimer ( 1 ) was isolated from Coleophoma sp. andinhibited cFMS receptor tyrosine kinase (IC 50 of 0.4 µM), with greater than 10-foldselectivity versus nine other protein kinases. The known fungal metabolites balanoland altenusin inhibited cFMS kinase and pp60c-Src kinase, respectively, even more potently and selectively.Altenusin inhibited pp60c-Src with an IC 50 of 20 nM and a selectivity of at least 400-fold versus nine otherprotein kinases. Balanol inhibited cFMS receptor kinase with an IC 50 of 1 nM and selectivities of 14-75-foldversus pp60c-Src and VEGF receptor kinases and greater than 10,000-fold versus seven other kinases. Keywords: fungal metabolite, protein kinase inhibitor, cFMS receptor tyrosine kinase, pp60c-Src kinase, balanol, altenusin,alternariol. INTRODUCTION Natural products are a rich source for inhibitors of proteinkinases (ex, erbstatin, coumarins, staurosporines,lavendustin, etc, [1]). Although many of these compoundsare polyhydroxylated aromatics and not considered goodchemical templates for pharmaceutical development, there areindeed several natural products (or derivatives) that arecurrently in clinical trials (ex, flavopiridol, bryostatin-1,PKC412, UCN 01, [2]). In addition, natural products areoften used as tool compounds because of their potency orselectivity. For example, wortmannin is routinely used as apotent and selective inhibitor of phosphatidylinositol-3-kinase both

Frequency‐swept HMQC sequences for high‐throughput NMR analysis

We describe here new versions of the DEPT phase‐encoded HMQC experiment that offer robust performance and improved sensitivity. The new sequences rely on frequency‐swept proton and carbon pulses to minimize signal losses from miscalibrated pulses while providing ‘J compensation’ to optimize the signal strength over a range of heteronuclear coupling constants. By including both proton and carbon‐swept pulses, the new sequences also offer an additional signal gain of roughly 10% over well‐calibrated hard‐pulse experiments. The new sequences also demonstrate that one can construct a sequence that incorporates both 90° and 180° frequency‐swept pulses. Although individual pulses in the sequence cause severe phase roll, the phase roll can be eliminated by the proper choice of pulse lengths and sweep directions. Copyright