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Gastrointestinal mucoadhesive patch system


1. Introduction The technology, which improves the bioavailability (BA) of poorly absorbable drugs from the gastrointestinal (GI) tract, has been recognized as an important strategic tool to optimize oral drug therapy and to improve the patient compliance. Protein/peptide drugs are the representative low BA drugs. To elucidate the pharmacological activity of protein/peptide drugs, two barriers, ie. hydrolysis in the GI tract and low membrane permeability, must be conquered. Oral administration destroys all physiological activity of the protein/peptide drugs and explains why typical oral BA of protein/peptide drugs are usually less than 1-2 %. To improve the oral BA of protein/peptide drugs, some technologies such as absorption enhancers and enzyme inhibitors and enteric coated formulations, have been challenged. However, no technology has been launched yet. Recent studies have indicated that the dilution and spreading of absorption enhancer in GI tract reduce the enhancing effect of the absorption promoter. Professor Kanji Takada (Kyoto Pharmaceutical University, Department of Pharmacokinetics) has invented an novel DDS technology to improve the BA of protein/peptide drugs. This technology is based on the patch formulation, which creates a closed space on the target site of GI mucosa by adhering to the mucosal membrane.
2. Concept of GI-MAPS The concept of GI-MAPS is (1) to protect drug from the hydrolysis by the digestive enzymes and (2) to obtain high concentration gradient of drug and absorption enhancer between the intestinal mucosal surface by adhering to the target site of the intestine and enterocytes.
3. Function of GI-MAPS After oral administration of gelatin capsule containing GI-MAPS, drugs in the formulation are protected from the gastric juice in the stomach by enteric film on the adhesive layer (adhesion site-controlling layer) and protection layer.

When GI-MAPSis transferred to the small intestine, the adhesion site-controlling layer of GI-MAPSTM is dissolved at the target site of the small intestine, and GI-MAPS adhere to the intestinal mucosal membrane

As the result of adhesion, the drug carrying layer of GI-MAPS existing between protecting layer and adhesive layer forms a closed space. Drugs in the closed space are protected from the attack of the digestive enzymes in the intestinal lumen.

Dissolution of drug in the drug carrying layer forms the high concentration gradient of drug between the GI-MAPS and the enterocytes, and consequently formulated drug can be efficiently absorbed.

In addition, when an absorption enhancer is formulated with a drug in the drug carrying layer, the concentration of absorption enhancer as well as drug in this closed space reaches to high level. Under this condition, optimal absorption enhancing effect can be obtained.
4. Proof of the concept of GI-MAPS Abdominal incision was performed in dogs whose duodenum GI-MAPS containing desmopressin was adhered with an adhesive polymer. After application, blood samples were obtained and plasma drug concentrations were measured by a LC/MS method. By comparing to the iv data, the BA of desmopressin from GI-MAPS was 46%, though the BA from co-administration with absorption enhancer was 10 %.G-CSF (125 microgram) loaded GI-MAPS was orally administered to beagle dogs. Total white blood cell (WBC) count in the systemic circulation after administration significantly increased. In contrast, WBC after oral administration of G-CSF solution did not significantly change from the pre-dose level. The pharmacological availability of G-CSF from GI-MAPS was 23% as compared to the intravenous administration of the same dose of G-CSF.
5. Adhering of GI-MAPS to the intestinal mucosa At 1, 2, 3, 4, 5 and 6 hr after administration of GI-MAPS into the rat duodenum, the rats were sacrificed. The whole small intestine from pyloric sphincter to the ileo-cecal junction of each rat was divided into five portions (#l-#5) and the remaining GI-MAPS in the GI tract was visually detected. GI-MAPS adhered to section #2 and retained there for approximately 2 hr.
6. Human study of GI-MAPS containing caffeine as a model drug
To study the GI transit characteristics of GI-MAPS, 50 mg of caffeine was formulated in GI-MAPS and was administered to human volunteers. After ingestion, saliva samples were collected consecutively for 12 hr and salivary caffeine excretion rates were measured by a HPLC assay method. As a control, enteric capsule containing 50 mg of caffeine was used. High salivary caffeine excretion rates were observed for 8 hours.
7. Large scale production
Professor Takada has codeveloped a GI-MAPS producing machine with Toray Engineering Co. Ltd., in 2008. With this machine, micron size GI-MAPS can be produced under GMP condition.
8. Examples
BBioavailability (BA) of peptide/protein drugs
Peptide/protein BA in ratss BA in dogs
erythropoietin (EPO) 12.1 % -
interferon (IFN) alfa 7.8 % (compared to sc injection) -
salmon calcitonin 6.2 % -
desmopressin - 46 %*

** device method: GI-MAPS mimetic device was fixed onto the jejunum mucosa

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