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Novel chitosan derivatives as polymeric carriers for peptide and protein drug delivery
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SOME PHARMACEUTICALSTRATEGIESFOR T’HEFORMULATION OF SPARINGLYSOLUBLEDRUGS M RhBne-PoulencRonr, V&y-Alforhille Research Center, 13,QuaiJulesGucsde. 94400 Viny-sur-Seine, France
RELEVANCE OF THE PEPTIDE-BOND CARBONYL FOR AFFlNlTY .------FOR ‘ HESMALLPEPTIDECARRIER. II Iosef and Ronald G Schoenmakers. Department of Pharmaceutics, University of Utrecht. NL3508 TB Utrecht, the Netherlands.
Nowadays, short development timeline is being established as an additionnal criteria for the selection of new chemical entities (NCE) and this feature is kicking out NCE candidates with poor aqueous solubility because of their complex and lengbly developmentplan. Some of those sparingly soluble candidates being of real therapeutic interest. one should recognize the interest of an early availability, say at discovery stage, of pharmaceutical technologies which could overcome this negative pbysico-chemical properly. As an example, IBP 5823, an antisubtance P candidate with aqueous solubility as low as 20 ng/ml has been successfullyformulated as a solid solution in either polyvinyl~lidone (PVP) or polyethylenegiycol (PEG) for oral route of administration and as a solid solution in colloidal carriers made of either [email protected] acid) polymer (PLA) or poly@,L lactic acid)poly(ethylcneglycol) polymer (PLA-PEG) for intravenous route of administration. Those formulated systems can be manufactured and characterized using very small quantities of chemicals thus being adapted to early development stage when minute quantiti~ of chemicals are available. Tbe biodisposition of these formulated systems is dramatically intluenced by the constitutive polymer of the formulation and is dramatically tierent from Ihe reference biodisposition of the non formulated NCB candidate. The biodisposition of these formulated systems is “excipient driven” and not depending anymore on the solid state of the NCE candidate, thus permitting lo panially overcome its poor aqueous solubility. References : I- Verrecchia T., Spenlehauer G., Bazile D., Murry-Brelier A., Archimbaud Y.. Veillard M. Non-stealth (poly (lactic acid/albumin)) and stealth f.poly (lactic acid -polyethylene glycol)) nanopsrticles as injectable drug carriers. 1. Contr Rel. 1995; 36: 49.61. 2- Landry F.B., Bazile D., SperdebauerG., Veillard M. and Kreutcr I. Degradation of poly@,L-lactic acid) nanoparticles coated with albumin in model digestive fluids (IJSP XXII).Biomaterials 1996; 17: 715-723.
Purpose. To evaluate whether the carbonyl group in the peptidebond of substrates for the intestinal small-peptide carrier is necessary for affiiity for the carrier, resulting in interaction and subsequent transport. Methods. Enalapril, an estahlished substrate for the small-peptide carrier, was selected as lead compound and an analogue with the peptidebond carbonyl in a reduced form was synthesized de nova: this analogue, N(ethoxycarbonyl-3-phenylpropyl)-L~~yl[CH~~-L-pmline, was called enamipril. ‘Ihe transport of both compounds was tested in freshly excised rat intestinal tissue (ileum) in side-by-side diffusion chambers (Ussing chambers). Transport was performed in both directions (mucosal and serosal) at various concentrations. Moreover, the inhibition of m-->s transport was performed using cephalexin, a known substrate, and interaction with tbe carder was tested by studying the inhibition of amoxycillii transport by both enalapril and enamipril. Results. The enalapril-analogue enamipril shows m-->s transport linear with concentration, and in contrast with enalapril, its transport can not be inhibited by cephalexin, indicating that enamipril is not transported by the small-peptide carrier, hut only passively. Inhibition of amoxycillin transport is similar for both compounds, indicating that the carbonylgroup is not influencing binding to the carrier. In contrast, the s--pm transport of enamipril is not linear with concentration, and inhibition with verapamil suggests strongly additional transport by the P-glycoprotein, apart from passive transport. Conclusions. The carbonyl group in the peptide bond of substrates for the smallpeptide canier is essential for transport by this carrier, but not for interaction with this carrier.
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88
NOVEL CHITOSAN DERIVATIVES AS POLYMERIC CARRIE&S FOR PEPTIDE AND PROTEIN DRUG DELIVERY w M.Thanou A.F. KobC J.C. Verhoef Department of Pharmaceu&al Technology, Leiden/Amsterdam Center for Drug Research. Leiden University, P.O. Box 9502. 2300 RA Leiden. The Netherlands
Inverse toroidal vesicles: the precursors of tubular structures in sorbiten monosterrate organogels m G Gregoriadisand A T Florence,Centrefor Drug Delivery Research, School of Pharmacy. University of London, London, UK
decrease the resistance
only marginal. These. experiments wer,e at the neutral pH value of 7.2, at which chltosan Itself 1s meffective. At the end of the experiment the monolayers were checked for viability. using the trypan blue exclusion techm ue. In all performed
cases exclusion of the stam from the monolayers suggest? 3 that the monolayers were still viable. In conclusion, the catlomc chltosan derivatives can be potential absorption enhancers of peptide and protqn, drugs. All of the aforementio?ed pal mers show he,+ roperties than chitosan at physlologlca Y pH values. and tr IS especte s”lublh? tPlat they will prove to be valuable tools as therapeutic drug carriers.
We have previously reported the gelation of a number of organic solvents e.g. he-, isopropyl my&a@ by the non-ioruc smfactant, sorbitan monostearate [Murdan el al, 19961. The thermoreversihle organic gels (prepared by dissolving/dispersing the gelator in the solvent at 6O”C, followed by cooling the sol) are opaque semi-solids and their micmstructures consist of a 3dimensional network of tubular aggregates. We report here the formation of these tubules from toroidal vesicular precursors, observed using hot-stage light microscopy as a sol was cooled to the gel state. On cooling the suspension, toroidal vesicular structures were seen to form in the organic solvent. We believe these toroids are analogous to other well-known vesicles, liposomcs and niosomes, except for their tomidal (rather than spherical) shape and their inverted nature. Cooling the sol causes a decrease in the soluhility of the surfactant in the oil, with consequent reduction in solvent-gclator afiinities. As a result, the surfactant molecules self-assemble to shield the solvophobic head groups and inverted toroidal vesicles are formed. As in liposomes and niosomcs, the. surfactants arc thought to be arranged in hilayers, each toroid consisting of several bilayers. The toroidal vesicles are rather short-lived structures and only exist at the sol to gel transition temperature (44-41’C). Upon further cooling, the toroids are converted into tubules. It is unclear at present how such a transition occurs: the toroids may contract and elongate into tubules on cooling, or they may split into rod-shaped cylindrical tubules. The newly-formed tubules then join with one another, contact points are established and a 3-dimensional tubular network which acts as the gel skeleton is produced as the sol gels. S Murdan. G Gregoriadis and A T Florence, Non-ionic surfactant based organogels mcorporaling mosomes, S T P Pharma Sciences, 1996,6,44-48
SOME PHARMACEUTICALSTRATEGIESFOR T’HEFORMULATION OF SPARINGLYSOLUBLEDRUGS M RhBne-PoulencRonr, V&y-Alforhille Research Center, 13,QuaiJulesGucsde. 94400 Viny-sur-Seine, France
RELEVANCE OF THE PEPTIDE-BOND CARBONYL FOR AFFlNlTY .------FOR ‘ HESMALLPEPTIDECARRIER. II Iosef and Ronald G Schoenmakers. Department of Pharmaceutics, University of Utrecht. NL3508 TB Utrecht, the Netherlands.
Nowadays, short development timeline is being established as an additionnal criteria for the selection of new chemical entities (NCE) and this feature is kicking out NCE candidates with poor aqueous solubility because of their complex and lengbly developmentplan. Some of those sparingly soluble candidates being of real therapeutic interest. one should recognize the interest of an early availability, say at discovery stage, of pharmaceutical technologies which could overcome this negative pbysico-chemical properly. As an example, IBP 5823, an antisubtance P candidate with aqueous solubility as low as 20 ng/ml has been successfullyformulated as a solid solution in either polyvinyl~lidone (PVP) or polyethylenegiycol (PEG) for oral route of administration and as a solid solution in colloidal carriers made of either [email protected] acid) polymer (PLA) or poly@,L lactic acid)poly(ethylcneglycol) polymer (PLA-PEG) for intravenous route of administration. Those formulated systems can be manufactured and characterized using very small quantities of chemicals thus being adapted to early development stage when minute quantiti~ of chemicals are available. Tbe biodisposition of these formulated systems is dramatically intluenced by the constitutive polymer of the formulation and is dramatically tierent from Ihe reference biodisposition of the non formulated NCB candidate. The biodisposition of these formulated systems is “excipient driven” and not depending anymore on the solid state of the NCE candidate, thus permitting lo panially overcome its poor aqueous solubility. References : I- Verrecchia T., Spenlehauer G., Bazile D., Murry-Brelier A., Archimbaud Y.. Veillard M. Non-stealth (poly (lactic acid/albumin)) and stealth f.poly (lactic acid -polyethylene glycol)) nanopsrticles as injectable drug carriers. 1. Contr Rel. 1995; 36: 49.61. 2- Landry F.B., Bazile D., SperdebauerG., Veillard M. and Kreutcr I. Degradation of poly@,L-lactic acid) nanoparticles coated with albumin in model digestive fluids (IJSP XXII).Biomaterials 1996; 17: 715-723.
Purpose. To evaluate whether the carbonyl group in the peptidebond of substrates for the intestinal small-peptide carrier is necessary for affiiity for the carrier, resulting in interaction and subsequent transport. Methods. Enalapril, an estahlished substrate for the small-peptide carrier, was selected as lead compound and an analogue with the peptidebond carbonyl in a reduced form was synthesized de nova: this analogue, N(ethoxycarbonyl-3-phenylpropyl)-L~~yl[CH~~-L-pmline, was called enamipril. ‘Ihe transport of both compounds was tested in freshly excised rat intestinal tissue (ileum) in side-by-side diffusion chambers (Ussing chambers). Transport was performed in both directions (mucosal and serosal) at various concentrations. Moreover, the inhibition of m-->s transport was performed using cephalexin, a known substrate, and interaction with tbe carder was tested by studying the inhibition of amoxycillii transport by both enalapril and enamipril. Results. The enalapril-analogue enamipril shows m-->s transport linear with concentration, and in contrast with enalapril, its transport can not be inhibited by cephalexin, indicating that enamipril is not transported by the small-peptide carrier, hut only passively. Inhibition of amoxycillin transport is similar for both compounds, indicating that the carbonylgroup is not influencing binding to the carrier. In contrast, the s--pm transport of enamipril is not linear with concentration, and inhibition with verapamil suggests strongly additional transport by the P-glycoprotein, apart from passive transport. Conclusions. The carbonyl group in the peptide bond of substrates for the smallpeptide canier is essential for transport by this carrier, but not for interaction with this carrier.
86
88
NOVEL CHITOSAN DERIVATIVES AS POLYMERIC CARRIE&S FOR PEPTIDE AND PROTEIN DRUG DELIVERY w M.Thanou A.F. KobC J.C. Verhoef Department of Pharmaceu&al Technology, Leiden/Amsterdam Center for Drug Research. Leiden University, P.O. Box 9502. 2300 RA Leiden. The Netherlands
Inverse toroidal vesicles: the precursors of tubular structures in sorbiten monosterrate organogels m G Gregoriadisand A T Florence,Centrefor Drug Delivery Research, School of Pharmacy. University of London, London, UK
decrease the resistance
only marginal. These. experiments wer,e at the neutral pH value of 7.2, at which chltosan Itself 1s meffective. At the end of the experiment the monolayers were checked for viability. using the trypan blue exclusion techm ue. In all performed
cases exclusion of the stam from the monolayers suggest? 3 that the monolayers were still viable. In conclusion, the catlomc chltosan derivatives can be potential absorption enhancers of peptide and protqn, drugs. All of the aforementio?ed pal mers show he,+ roperties than chitosan at physlologlca Y pH values. and tr IS especte s”lublh? tPlat they will prove to be valuable tools as therapeutic drug carriers.
We have previously reported the gelation of a number of organic solvents e.g. he-, isopropyl my&a@ by the non-ioruc smfactant, sorbitan monostearate [Murdan el al, 19961. The thermoreversihle organic gels (prepared by dissolving/dispersing the gelator in the solvent at 6O”C, followed by cooling the sol) are opaque semi-solids and their micmstructures consist of a 3dimensional network of tubular aggregates. We report here the formation of these tubules from toroidal vesicular precursors, observed using hot-stage light microscopy as a sol was cooled to the gel state. On cooling the suspension, toroidal vesicular structures were seen to form in the organic solvent. We believe these toroids are analogous to other well-known vesicles, liposomcs and niosomes, except for their tomidal (rather than spherical) shape and their inverted nature. Cooling the sol causes a decrease in the soluhility of the surfactant in the oil, with consequent reduction in solvent-gclator afiinities. As a result, the surfactant molecules self-assemble to shield the solvophobic head groups and inverted toroidal vesicles are formed. As in liposomes and niosomcs, the. surfactants arc thought to be arranged in hilayers, each toroid consisting of several bilayers. The toroidal vesicles are rather short-lived structures and only exist at the sol to gel transition temperature (44-41’C). Upon further cooling, the toroids are converted into tubules. It is unclear at present how such a transition occurs: the toroids may contract and elongate into tubules on cooling, or they may split into rod-shaped cylindrical tubules. The newly-formed tubules then join with one another, contact points are established and a 3-dimensional tubular network which acts as the gel skeleton is produced as the sol gels. S Murdan. G Gregoriadis and A T Florence, Non-ionic surfactant based organogels mcorporaling mosomes, S T P Pharma Sciences, 1996,6,44-48