The project includes various fields of research in order to investigate not only the route of degradation of potential new peptide drugs in the hostile gastrointestinal (GI) tract environment, but also to study the role of peptide transport systems (P-gp and CYP3A4) on the absorption of peptides and peptidomimetics. These investigations are performed in order to obtain the necessary information for the development of novel drug delivery system for peptide and peptidomimetic drugs.
The stability of peptide drug in GI will be first simulated in vitro using a range of purified enzymes (pancreatic and/or gastric) to determine the enzymes involved in luminal hydrolysis, and then the study will be conducted in vivo using adult male Sprague-Dawley rats. This is in order to achieve new and more precise knowledge about the role of the peptide transporters (first branch of the study) as well as the roles of P-gp and CYP3A4 (second branch of the study).
Calcitonin, Human Growth Hormone, Erytropoeitin, Cyclosporin and Vaccines are the peptide of protein substrates to be investigated in the present study. Initially, the work entails studying the formulation aspects of the delivery system. The studies will be performed with surrogate measures in vitro, which could lead to animal studies. Promising formulations could possibly then be tested in humans. The formulation strategies include SEDDS, liposomes, dendrimers, PLGA microspheres and cyclodextrins (see below).

In vitro formulation studies

Self-emulsifyng drug delivery systems (SEDDS)
Peptide drugs will be incorporated into formulations with satisfactory self- emulsifying rate to determine their effect on the stability of the SEDDS. Various physical parameters will be measured in order to fully characterize the resulting emulsion.
Liposome delivery system
Liposomes will be prepared using the Reverse Phase Evaporation method. Peptide drugs will be incorporated into the polar phase of the liposomes. Physical characteristics of the liposomes as well as the chemical stabilities of the lipids and entrapped drugs will also be investigated.
Dendrimers
Each peptide drug will be reacted with starbust (PAMAM) dendrimers. Critical physical variables for the delivery activity will be investigated using sedimentation and gel electrophoresis methods.
Poly (lactic/glycolic acid) microspheres
Microparticles will be formulated using the Water-in-Oil emulsion/solvent technique from blends of poly-DL-lactide-co-glycolide and Pluronics. In vitro characterization will be conducted.
Cyclodextrin

EXECUTIVE SUMMARY

Project Title:
DESIGN AND DEVELOPMENT OF NOVEL DELIVERY SYSTEMS FOR BIOPHARMACEUTICALS

 

In order to determine the amount of drug incorporated into the cyclodextrins, different techniques such as DSC (differential scanning calorimetry), SEM (scanning electron microscopy), NMR, and UV will be used.

In vivo evaluation

Male, Spraque-Dawley rats will be used to determine the bioavailability of peptide drugs administered as specialized drug delivery systems. In addition, a technique to elucidate the lymphatic absorption of the drug, through the cannulation of the thoracic duct of an anaesthetized rat, will be performed.

Period of the project : 3 Years (2001 - 2004)

Achievements

Progress/Achievements for year one

New Process :

1- A method to evaluate the percentage of drug entrapped within the liposome aqueous phase had to be first developed. This was achieved by the use of ultracentrifugation technique and lipid solubiliser
2- Liposomal formulations is a promising technique for encapsulating and protecting a peptide-like drug.

Discovery :

1- It was found that the variations had a significant influence on the equilibrium concentration of the drug within the vesicles.
2- The sizes of the vesicles were shown to be different and therefore could indicate that the drug release performance would be consequently affected.
3- There was no significant difference in the bioavailabilities of the drug given through the simple drug solution and the physical mixture.
4- It was found that the liposomal formulation resulted in a significant increase in the bioavailability
5- Preparation parameters and liposomal matrix composition were found to influence the drug entrapment efficiency and hence the performance of the formulation.
6- One of the characteristics of the formulation, that is particle siza, was found to be affected by aging conditions.
7- In-vivo studies performed on rats suggest that the liposomal formulation gave better oral bioavailability of the drug than the drug solution alone or a physical mixture of the drug and a lipid.