Peter Watts

PecSys: in situ gelling system for optimised nasal drug delivery

PecSys™ (PS) is a proprietary pectin-based drug delivery system designed to gel when applied to mucosal surfaces and with potential areas of application for drugs used in local and systemic disease therapy. The current area of focus is intranasal drug delivery where PS is being used to optimise absorption of lipophilic drugs into the systemic circulation. Pectin is described as GRAS (generally regarded as safe) with an excellent regulatory position through its long history of pharmaceutical and food usage. Tests to measure the functional gelling properties of pectin raw material and PS have been devised and validated. The PS-based products at the most advanced stages of development are intranasal formulations containing opioid analgesics intended to provide rapid pain relief with simple and convenient dosing and minimal side effects. The profile of such drugs may not be optimal through current routes of delivery and the ability of PS to modulate their pharmacokinetic profiles, such as attenuation of the peak plasma concentration (Cmax), has been demonstrated in clinical testing. The lead product using PS is a fentanyl nasal spray formulation (NasalFent®), which has successfully met the primary objective in a pivotal Phase III clinical study and is scheduled for regulatory filings in the first half of 2009.

Development of in vitro models to demonstrate the ability of PecSys®, an in situ nasal gelling technology, to reduce nasal run-off and drip.

Many of the increasing number of intranasal products available for either local or systemic action can be considered sub-optimal, most notably where nasal drip or run-off give rise to discomfort/tolerability issues or reduced/variable efficacy. PecSys, an in situ gelling technology, contains low methoxy (LM) pectin which gels due to interaction with calcium ions present in nasal fluid. PecSys is designed to spray readily, only forming a gel on contact with the mucosal surface. The present study employed two in vitro models to confirm that gelling translates into a reduced potential for drip/run-off: (i) Using an inclined TLC plate treated with a simulated nasal electrolyte solution (SNES), mean drip length [±SD, n = 10] was consistently much shorter for PecSys (1.5 ± 0.4 cm) than non-gelling control (5.8 ± 1.6 cm); (ii) When PecSys was sprayed into a human nasal cavity cast model coated with a substrate containing a physiologically relevant concentration of calcium, PecSys solution was retained at the site of initial deposition with minimal redistribution, and no evidence of run-off/drip anteriorly or down the throat. In contrast, non-gelling control was significantly more mobile and consistently redistributed with run-off towards the throat. Conclusion: In both models PecSys significantly reduced the potential for run-off/drip ensuring that more solution remained at the deposition site. In vivo, this enhancement of retention will provide optimum patient acceptability, modulate drug absorption and maximize the ability of drugs to be absorbed across the nasal mucosa and thus reduce variability in drug delivery.

Insight into the relationship between the cell culture model, cell trafficking and siRNA silencing efficiency

Despite research efforts, cell uptake processes determining siRNA silencing efficiency remain unclear. Here, we examine the relationship between in vitro cell culture models, cellular trafficking and siRNA silencing efficiency to provide a mechanistic insight on siRNA delivery system design. Model siRNA-polyplexes, based on chitosan as a ‘classical’ condensing agent, were applied to a panel of lung epithelial cell lines, H1299, A549 and Calu-3 and cell internalization levels, trafficking pathways and gene silencing assessed on exposure to pharmacological inhibitors. The data reveal striking differences in the internalization behaviour and gene silencing efficiency in the tested cell lines, despite their common lung epithelial origins. The model system’s silencing was lower where clathrin internalization pathway predominated in Calu-3, relative to silencing in H1299 cells where a non-clathrin internalization appears dominant. Increased silencing on endosomal disruption was apparent in Calu-3 cells, but absent when cellular internalization was not predominantly clathrin-mediated in A549 cells. This highlights that identifying cell trafficking pathways before incorporation of functional components to siRNA delivery systems (e.g. endosomolytic compounds) is crucial. The study hence stresses the importance of selection of appropriate cell culture model, relevant to in vivo target, to assess the gene silencing efficiency and decide which functionalities the ‘stratified siRNA silencing vector’ requires.

Re-formulating drugs and vaccines for intranasal delivery: maximum benefits for minimum risks?

The challenges being faced by the pharmaceutical industry in terms of patent expiries and a sparse pipeline of new products are well documented, as are the risks and costs associated with developing new molecular entities. Major pharmaceutical companies are increasingly looking to augment their traditional core expertise in the discovery of small molecules with the development of biologicals (e.g. peptide-based, protein-based, antibody-based and nucleic-acid-based therapies), which are seen as a key element in achieving long-term growth. There is also considerable current interest in vaccines, both in the traditional area of mass immunization against infections and as a novel approach to disease treatment.

Water-soluble substituted chitosan derivatives as technology platform for inhalation delivery of siRNA

Abstract Despite research efforts full potential of siRNA-based therapeutics has not yet been fully realized due to a need for suitable, effective delivery formulations. Here, we examine a potential of a new class of water-soluble chitosans as siRNA platform for pulmonary delivery. The system is based on piperazine-substituted chitosans, a material designed to integrate established, safe application of chitosan for mucosal administration with novel properties: the piperazine-substituted chitosans are freely water-soluble at physiological pH, possess low cytotoxicity (no significant reduction in cell viability up to 0.1 mg/ml), and provide efficient incorporation of siRNA into sub-300 nm colloidal complexes (at relatively low polymer/siRNA ratio of 5:1). In vitro, the complexes achieved silencing of a model gene at a level of 40–80%, when tested in a panel of lung epithelial cells. Considering the formulation ‘developability’, there were no significant changes in the complexes’ size and integrity on aerosolisation by microsprayer (PenCentury™) device. Following intratracheal aerolisation, the complexes deposited throughout the lung, although relatively inhomogeneously, as judged from IVIS imaging of the isolated mouse lung (visualizing DY647-siRNA). In vivo data illustrate absence of adverse effects on repeated administration of complexes and significant tumor reduction in atopical lung cancer model in mice. Altogether, the data illustrates potential of substituted chitosan derivatives to be utilized as a safe system for inhalation delivery of siRNA.