Development and In Vitro Evaluation of Long Circulating Liposomes for Targeted Delivery of Gemcitabine and Irinotecan in Pancreatic Ductal Adenocarcinoma.

The classically used nontargeted chemotherapeutic approach to pancreatic cancer has a dual drawback of suboptimal drug delivery at the target site and the systemic side effects produced by the unfettered exposure of the drug to healthy tissue. This study has the objective of developing novel poly(2-ethyl-2-oxazoline) (PETOX)-based long circulating liposomes loaded with gemcitabine and irinotecan for the treatment of pancreatic ductal adenocarcinoma, with a juxtaposition to PEGylated and uncoated liposomes. A PETOX-cholesteryl chloroformate lipopolymer conjugate (PETOX-ChC) with a carbonate linkage was prepared and characterized by 1H NMR, FTIR, and DSC. Liposomes were prepared using the thin film hydration technique followed by freeze-thaw and membrane extrusion methods. Liposome characterization includes particle size determination, zeta potential determination using a zetameter, and structural elucidation using 31P NMR and cryo-TEM. The PETOXylated liposomes showed a particle size of 180.1 ± 2.2 nm and a zeta potential of - 33.63 ± 1.23 mV. The liposomal combination therapy of gemcitabine and irinotecan was found to have an IC50 value 39 times lower in comparison to the drug combination in solution, while the PEGylated and PETOXylated liposomes showed IC50 values 1.6 times lower and 2 times lower than that of uncoated liposomes, respectively, against Mia PaCa II pancreatic cancer cell line. The PEGylated and PETOXylated liposomes showed 4.1 and 5.4 times slower macrophagial uptake in vitro in comparison to the uncoated liposomes respectively. The PEGylated liposomes showed 11% higher in vitro macrophagial uptake in comparison to PETOXylated liposomes.

Relative blood-brain barrier permeabilities of the cholecystokinin receptor antagonists devazepide and A-65186 in rats.

The blood-brain barrier permeabilities of the type-A cholecystokinin receptor antagonists devazepide and A-65186 (Nalpha-3-quinolinoyl-D-Glu-N,N-dipentylamide) have been compared with those of the reference compounds iodoantipyrine, which readily penetrates the blood-brain barrier, and mannitol, which does not. Anaesthetized rats received a bolus injection into the left carotid artery of [14C]iodoantipyrine (0.25 microCi) combined with [3H]mannitol, [3H]devazepide or [3H]A-65186 (1 microCi each). Rats were decapitated 12s after injection and the brains were removed. Four samples of left cerebrum (ca 100 mg each) were solubilized overnight and 14C and 3H activity were measured. The brain-uptake index for each test compound was determined as [(3H/l4C for sample)]/[(3H/14C for injectate)] x 100, with a value of 100 representing blood-brain barrier permeability equal to that for iodoantipyrine. The brain-uptake index (mean+/-s.e.m.) was 1.6+/-0.3 for [3H]mannitol (n=5), 90.6+/-4.1 for [3H]devazepide (n=7, P<0.001 compared with mannitol) and 3.5+/-0.7 for [3H]A-65186 (n=4, P > 0.05 compared with mannitol, P < 0.001 compared with devazepide). Thus, devazepide readily penetrated the blood-brain barrier whereas A-65186 did not. It is concluded that devazepide and A-65186 are likely to be useful pharmacological tools for determining whether cholecystokinin is acting peripherally or at brain sites beyond the blood-brain barrier to produce satiety or any other function mediated by the type A cholecystokinin receptor.

Solvent effects on coupling yields during rapid solid-phase synthesis of CGRP(8-37) employing in situ neutralization.

The success of solid-phase peptide synthesis is often dependent upon solvation of the resin and the growing resin-bound peptide chain. We investigated the relationship between solvent properties and solvation of the resin and peptide-resin in order to obtain satisfactory coupling yields for the rapid solid-phase peptide synthesis, using butyloxycarbonyl-(Boc)-amino acid derivatives, of human-alpha-calcitonin gene-related peptide(8-37) (CGRP(8-37)). Solvation of (p-methylbenzhydrylamine)copoly(styrene-1% divinylbenzene (DVB) (resin) and resin covalently bound to the fully protected amino acid sequence of CGRP(8-37) (peptide-resin) was correlated to solvent Hildebrand solubility (delta) and hydrogen-bonding (delta(h)) parameters. Contour solvation plots of delta(h) vs. delta revealed maximum solvation regions of resin and peptide-resin. Maximum resin solvation occurred with N-methylpyrrolidinone (NMP), NMP : dimethylsulfoxide (DMSO) (8 : 2) and DMSO. Inefficient solvation of the peptide-resin occurred with these solvents and resulted in poor syntheses with average coupling yields of 78.1, 88.9 and 91.8%, respectively. Superior peptide-resin solvation was obtained using dimethylacetamide (DMA) and dimethylformamide (DMF), resulting in significantly higher average coupling yields of 98.0 and 99.5%, respectively. Thus, the region of maximum peptide-resin solvation shifts to solvents with higher delta(h) values. DMF provided the most effective peptide-resin solvation and was the only solvent from which CGRP(8-37) was obtained as a single major product in the crude cleaved material.