EFFECTS OF ENHANCERS ON MACROMOLECULES FORMULATIONS ON MEMBRANE PENETRATION, CELL VIABILITY AND RESISTANCE USING EPIAIRWAY™ TISSUE MODEL.
Drug delivery by the nasal route provides many advantages and is an attractive alternative for drugs that cannot be delivered orally and hence typically administered by the parenteral route. Nasal delivery provides an attractive alternative not only because it overcomes the above-mentioned problems with oral delivery, but also due to its fast onset of action, its ease of use by the patient at home and during travel and the pain free nature of administration. The main drawback of nasal delivery is that the maximum dose that can be given is 100 mL per spray and the short duration (15 – 30 minutes) before the drug is cleared from the nasal cavity. One of the classes of drugs that are appropriately delivered nasally are proteins (e.g. Insulin, Growth Hormone, Interferons). Presently, these drugs are solely administered parenterally due to their fast degradation in GI and low permeation across epithelial membranes because of their large size. These drugs can be delivered nasally as they are very potent and hence sufficient dose could be administered through this route. Degradation of the polypeptide is of much less concern when administered by the nasal route than oral. In addition, the nasal epithelial membrane has much higher cut off in molecular weight for absorption than in GI thereby making it the best route for delivering macromolecules. The unabsorbed drug is cleared into GI and hence the toxicity of the unabsorbed drug is not a factor like in inhalation delivery. However, the low permeation across the epithelial membrane is a hurdle that needs to be overcome. One means of achieving this is using enhancers that increase the permeation of drugs across epithelial membranes. Here Nastech Pharmaceutical scientists present some of the studies that were performed to screen for enhancers that increase permeation of a 20 kDa protein with minimal toxicity (using MatTek’s EpiAirway human airway tissue equivalent). Study Results: The results indicate that several enhancers improve the permeation of protein across the membrane with minimal toxicity as seen both from the LDH and MTT assays. None of the enhancers showed toxicity as determined by MTT assay. However, the LDH assay showed significant toxicity for certain enhancers, especially for enhancer E-13. The reduction of resistance to about 5% of the initial for this enhancer was probably due to cell membrane lysis and hence was eliminated as an enhancer in further studies. A number of the enhancers increased the permeation of the drug greatly as compared to the control with negligible toxicity seen from both MTT and LDH assays. For example, one enhancer increased the permeation by 360 fold without any detectable toxicity. The increase in permeation correlates strongly with a decrease in resistance. As mentioned before, four of the enhancers did not show any difference from control in the MTT and LDH assays. This suggests that these enhancers act through the paracellular pathway, resulting in lowered resistance without changing cell viability or causing cell lysis. These enhancers were selected for further studies. Overall, the methodology presented here allowed Nastech Pharmaceutical scientists to quickly and efficiently screen potential enhancers for further studies.
Correlation, Cytotoxicity, Enhancers, EpiAirway, HPLC, Intranasal, LDH, MTT, MTT ET-50 tissue viability assay, MTT assay, Metabolic, Metabolism, Nasal, Nasal drug delivery, Permeation, Resistance, TEER, TER
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