Publication informationAdvanced Drug Delivery Reviews, (Part B): 277-319 Publisher ElsevierItem record/more information http://hdl.handle.net/10197/7800Publisher's statement þÿ T h i s i s t h e a u t h o r s v e r s i o n o f a w o r k t h a t w a s a c c e p t e d f o r p u b l i c a t i o n i n A d v a n c e d D r u g Delivery Reviews. Changes resulting from the publishing process, such as peer review,

A major challenge in oral drug delivery is the development of novel dosage forms to promote absorption of poorly permeable Class III drugs across the intestinal epithelium.To date, no absorption promoter has been approved in a formulation specifically designed for oral delivery of Class III molecules. Promoters that are designated safe for human consumption have been licensed for use in a recently approved buccal insulin spray delivery system and also for many years as part of an ampicillin rectal suppository.Unlike buccal and rectal delivery, oral formulations containing absorption promoters have the additional technical hurdle whereby the promoter and payload must be coreleased in high concentrations at the small intestinal epithelium in order to generate significant but rapidly reversible increases in permeability. The most advanced promoter in the clinic is the medium chain fatty acid (MCFA), sodium caprate (C 10 ) , a compound already approved as a direct food additive. We discuss how it has evolved to a matrix tablet format suitable for administration to humans under the headings of mechanism of action at the cellular and tissue level and in vitro and in vivo efficacy and safety studies.In specific clinical examples, we review how C 10 -based formulations are being tested for oral delivery of bisphosphonates using Gastro Intestinal Permeation Enhancement Technology, GIPET® (Merrion Pharmaceuticals, Ireland) and in a related solid dose format for anti-sense oligonucleotides (ISIS Pharmaceuticals, USA).Keywords: Oral drug delivery, Sodium caprate (C 10 ), absorption promoter, drug delivery platforms, clinical trials, oral formulation, drug delivery systems.3 TJs form a barrier to the uncontrolled absorption of noxious luminal antigens (gate function), and maintain epithelial polarity (fence function) [8,9]. In general, the TJ consists of a restrictive pathway (shunt) with a sharp molecular size cut off, and a second unrestrictive pathway (small pore) that permits paracellular permeation of molecules of radii <4.0 Å [10,11]. Depending on the intestinal region, TJ pore sizes range from 6-22Å, sufficient to permit mannitol (6.7 Å) and EDTA (10.8 Å) to permeate to an extent, whereas the passage of inulin (30-40 Å) and fluorescent-dextran 4kDa (FD-4, 26 Å) is essentially impeded [12][13][14][15][16].A number of approaches have been used to promote oral delivery of Class III drugs ( Alternatively, the use of nanoparticles comprising biocompatible polymers (e.g. chitosan,polylactide-co-glycolide, starch and glucans) can protect cargoes from GI proteases, increase GI retention and promote absorption across gut associated lymphoid tissue (GALT) and to a lesser extent, enterocytes [45][46][47]. Most data on nanoparticle absorption from rodent models suggest that M cells in the follicle-associated epithelium of Peyer's patches (PP) are the favored site of uptake for particles of diameter 500nm-1000nm [45].Given the paucity of M cells in the GI tract of adults, the relevance of PP uptake remains controversial ...

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Salcaprozate sodium (SNAC) and sodium caprate (C10) are two of the most advanced intestinal permeation enhancers (PEs) that have been tested in clinical trials for oral delivery of macromolecules. Their effects on intestinal epithelia were studied for over 30 years, yet there is still debate over their mechanisms of action. C10 acts via openings of epithelial tight junctions and/or membrane perturbation, while for decades SNAC was thought to increase passive transcellular permeation across small intestinal epithelia based on increased lipophilicity arising from non-covalent macromolecule complexation. More recently, an additional mechanism for SNAC associated with a pH-elevating, monomer-inducing, and pepsin-inhibiting effect in the stomach for oral delivery of semaglutide was advocated. Comparing the two surfactants, we found equivocal evidence for discrete mechanisms at the level of epithelial interactions in the small intestine, especially at the high doses used in vivo. Evidence that one agent is more efficacious compared to the other is not convincing, with tablets containing these PEs inducing single-digit highly variable increases in oral bioavailability of payloads in human trials, although this may be adequate for potent macromolecules. Regarding safety, SNAC has generally regarded as safe (GRAS) status and is Food and Drug Administration (FDA)-approved as a medical food (Eligen®-Vitamin B12, Emisphere, Roseland, NJ, USA), whereas C10 has a long history of use in man, and has food additive status. Evidence for co-absorption of microorganisms in the presence of either SNAC or C10 has not emerged from clinical trials to date, and long-term effects from repeat dosing beyond six months have yet to be assessed. Since there are no obvious scientific reasons to prefer SNAC over C10 in orally delivering a poorly permeable macromolecule, then formulation, manufacturing, and commercial considerations are the key drivers in decision-making.

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The application of permeation enhancers (PEs) to improve transport of poorly absorbed active pharmaceutical ingredients across the intestinal epithelium is a widely tested approach. Several hundred compounds have been shown to alter the epithelial barrier, and although the research emphasis has broadened to encompass a role for nanoparticle approaches, PEs represent a key constituent of conventional oral formulations that have progressed to clinical testing. In this review, we highlight promising PEs in early development, summarize the current state of the art, and highlight challenges to the translation of PE-based delivery systems into safe and effective oral dosage forms for patients.

Oral delivery of macromolecular drugs, particularly peptides and proteins, is the focus of many academic and industrial laboratories. Armed with an increased understanding of the structure and regulation of intestinal epithelial junctional complexes of the paracellular barrier, the development of permeation enhancement technology initially focused on the specific and reversible opening of tight junctions in order to enable oral delivery. Despite intense research, none of these specific tight junction-opening technologies has yet been approved in an oral drug product, likely because of poor efficacy. Less specific enhancer technologies with a long history of safe use in man have additional surfactant-like effects on the transcellular pathway that lead to improved efficacy. These are likely to be the first to market for selected poorly permeable peptides. This review presents a summary of some approaches taken to intestinal permeation enhancement and explores in detail the oral delivery system developed by Merrion Pharmaceuticals, Gastrointestinal Permeation Enhancement Technology (GIPET®).

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