Julie A. Straub

Calpain inhibitor AK295 protects neurons from focal brain ischemia. Effects of postocclusion intra-arterial administration.

This research was performed to determine whether a selective inhibitor of the calcium-dependent protease, calpain, could reduce ischemia-associated brain damage when peripherally administered after a vascular occlusion. Methods A variation of the rat middle cerebral artery occlusion model was used. A range of doses of AK295 (a novel calpain inhibitor synthesized for this purpose) was continuously infused through the internal carotid artery, beginning 1.25 hours from the initiation of the occlusion. Rats were killed at 21 hours, and the infarct volume was quantified. Results Postocdusion (1.25-hour) infusion of the calpain inhibitor AK295 elicited a dose-dependent neuroprotective effect after focal ischemia. The highest dose tested (3 mg/kg per hour) afforded the maximum effect, illustrated by a 32% reduction in infarct volume 21 hours after the ischemia (vehicle, 81.7±4.7 mm3; AK295, 54.9±6.9 mm3; P<.007). Conclusions These data provide the first evidence that a peripherally administered calpain inhibitor can protect against ischemic brain damage. They offer further support for an important role of calpain proteolysis in the brain degeneration associated with cerebral ischemic events and suggest that selective calpain inhibitors provide a rational, novel, and viable means of treating such neurodegenerative problems.

Postischemic administration of AK275, a calpain inhibitor, provides substantial protection against focal ischemic brain damage

Experiments were conducted to determine whether a potent, reversible calpain inhibitor could reduce the cortical ischemic brain damage associated with focal ischemia in the rat. AK275 (Z-Leu–Abu–CONH–CH2CH3), the active isomer of the diastereomeric mixture, CX275, was employed in conjunction with a novel method of perfusing drug directly onto the infarcted cortical surface. This protocol reduced or eliminated numerous, nonspecific pharmacokinetic, hemodynamic, and other potentially confounding variables that might complicate interpretation of any drug effect. Focal ischemia was induced using a variation of the middle cerebral artery occlusion method. These studies demonstrated a reliable and robust neuroprotective effect of AK275 over the concentration range of 10 to 200 μM (perfused supracortically at 4 μl/h for 21 h). Moreover, a 75% reduction in infarct volume was observed when initiation of drug treatment was delayed for 3 h postocclusion. Our data further support an important role of calpain in ischemia-induced neuropathology and suggest that calpain inhibitors may provide a unique and potentially powerful means of treating stroke and other ischemic brain incidents.

Calpain as a novel target for treating acute neurodegenerative disorders

Calpains are cytosolic, neutral proteases that normally exist in an inactive or quiescent state. They require higher than normal levels of calcium for activation which, once accomplished, lead to irreversible proteolysis of numerous cytoskeletal, membrane-associated and regulatory proteins. Because of these characteristics, calpain is gaining attention as a potentially important pathogenic variable in ischemic neuronal death. This manuscript explores this hypothesis by briefly reviewing current support for the role played by calpain in ischemic neurodegeneration, and then discussing a series of recently published studies which: 1. offer further evidence for the hypothesis, and 2. provide direct support for the idea that selective inhibition of calpain can greatly limit the neuronal damage that would normally occur following both global as well as focal brain ischemia. Thus, the data reviewed in this manuscript support the ideas that unregulated activation and proteolysis of intraneuronal calpain plays a significant role in the brain damage that occurs following an ischemic event and that delivering selective and membrane permeant calpain inhibitors to ischemic tissue may provide a powerfully effective therapeutic means of limiting neuronal damage.

Intravenous Hydrophobic Drug Delivery: A Porous Particle Formulation of Paclitaxel (AI-850)

No HeadingPurpose.To develop a rapidly dissolving porous particle formulation of paclitaxel without Cremophor EL that is appropriate for quick intravenous administration.Methods.A rapidly dissolving porous particle formulation of paclitaxel (AI-850) was created using spray drying. AI-850 was compared to Taxol following intravenous administration in a rat pharmacokinetic study, a rat tissue distribution study, and a human xenograft mammary tumor (MDA-MB-435) model in nude mice.Results.The volume of distribution and clearance for paclitaxel following intravenous bolus administration of AI-850 were 7-fold and 4-fold greater, respectively, than following intravenous bolus administration of Taxol. There were no significant differences between AI-850 and Taxol in tissue concentrations and tissue area under the curve (AUC) for the tissues examined. Nude mice implanted with mammary tumors showed improved tolerance of AI-850, enabling higher administrable does of paclitaxel, which resulted in improved efficacy as compared to Taxol administered at its maximum tolerated dose (MTD).Conclusions.The pharmacokinetic data indicate that paclitaxel in AI-850 has more rapid partitioning from the bloodstream into the tissue compartments than paclitaxel in Taxol. AI-850, administered as an intravenous injection, has been shown to have improved tolerance in rats and mice and improved efficacy in a tumor model in mice when compared to Taxol.

Effect of powder processing on performance of fenofibrate formulations

In this study, the effect of the order in which powder blending and jet-milling were performed for the production of the bulk powders on the performance of 200-mg dose orally disintegrating tablets (ODTs) of fenofibrate was evaluated. Bulk powders composed of fenofibrate, mannitol, copovidone S630, and docusate sodium in a 10:10:2:1.2 ratio were prepared by the following three processes: process A: fenofibrate+excipients-->blending; process B: fenofibrate-->jet-milling-->blending with excipients; process C: fenofibrate+excipients-->blending-->jet-milling. The bulk powders were granulated followed by blending and tableting. The materials were tested for Differential Scanning Calorimetry (DSC), drug particle sizing post-reconstitution, dissolution, optical micrography, Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS) and disintegration of the ODTs. It was found that the crystallinity of fenofibrate was not impacted by the blending and jet-milling processes. Process A produced materials having poorer fenofibrate reconstitution as compared to processes involving jet-milling. It was discovered that milling a blend of fenofibrate/excipient (process C) was advantageous over milling the raw drug alone (process B). Process C yielded bulk powder that showed rapid dissolution and ODTs which exhibited rapid disintegration.

High-performance liquid Chromatographic reversed-phase and normal-phase separation of diastereomeric α-ketoamide calpain inhibitors

Abstract α-Ketoamide calpain inhibitors contain a stereochemically labile chiral center adjacent to the keto moiety, which when epimerized results in diastereomers. High-temperature C 4 reversed-phase HPLC methods were developed for analysis of general purity of α-ketoamide calpain inhibitors and resulted in the separation of diastereomers of the positively charged inhibitor. AK295. Normal-phase methods that employed a Nucleosil Chiral-2 column were developed for separation of diastereomers of uncharged α-ketoamides. These methods used conditions in which the keto moiety of the inhibitors was minimally affected by the mobile phase.