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PurposeCriticalSorb™, with the principal component Solutol® HS15, is a novel mucosal drug delivery system demonstrated to improve the bioavailability of selected biotherapeutics. The intention of this study is to elucidate mechanism(s) responsible for the enhancement of trans-mucosal absorption of biological drugs by Solutol® HS15.MethodsMicelle size and CMC of Solutol® HS15 were determined in biologically relevant media. Polarised airway Calu-3 cell layers were used to measure the permeability of a panel of biological drugs, and to assess changes in TEER, tight junction and F-actin morphology. The rate of cell endocytosis was measured in vitro in the presence of Solutol® HS15 using a membrane probe, FM 2–10.ResultsThis work initially confirms surfactant-like behaviour of Solutol® HS15 in aqueous media, while subsequent experiments demonstrate that the effect of Solutol® HS15 on epithelial tight junctions is different from a ‘classical’ tight junction opening agent and illustrate the effect of Solutol® HS15 on the cell membrane (endocytosis rate) and F-actin cytoskeleton.ConclusionSolutol® HS15 is the principle component of CriticalSorb™ that has shown an enhancement in permeability of medium sized biological drugs across epithelia. This study suggests that its mechanism of action arises primarily from effects on the cell membrane and consequent impacts on the cell cytoskeleton in terms of actin organisation and tight junction opening.

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Osteoporosis treatment with PTH 1-34 injections significantly reduces the incidence of bone fracture. Potential further reductions in fracture rate should be observed through nasal spray delivery to address the poor compliance associated with patient dislike of repeated PTH 1-34 subcutaneous injections. In vitro human osteoblast-like Saos-2 cell intracellular cAMP levels were used to define PTH 1-34 nasal spray formulation bioactivity. The chemically synthesised PTH 1-34 had an EC of 0.76nM. Absorption enhancers polyethylene glycol (15)-hydroxystearate (Solutol HS15), poloxamer 407, chitosan or sodium hyaluronate did not diminish the bioactivity of PTH 1-34 within an in vitro cell culture model (p >0.05). We also demonstrated the effectiveness of the transmucosal absorption enhancer Solutol HS15 in a nasal spray formulation using a preclinical pharmacokinetic model. In Sprague-Dawley rats without the absorption enhancer the uptake of PTH 1-34 into the blood via intranasal delivery produced a Cmax of 2.1±0.5ng/ml compared to 13.7±1.6ng/ml with Solutol HS15 enhancer (p=0.016) and a Cmax14.8±8ng/ml in subcutaneous injections. Together these data illustrate that the nasal spray formulation bioactivity in vitro is not affected by the nasal spray absorption enhancers investigated, and the Solutol HS15 nasal spray formulation had an equivalent pharmacokinetic profile to subcutaneous injection in the rat model. The Solutol HS15 formulation therefore demonstrated potential as a PTH 1-34 nasal spray formulation for the treatment of osteoporosis.

Systemic delivery of proteins via the nasal route has to date been limited by their poor absorption across the nasal mucosa, and the less than optimal tolerability of known permeation enhancers. We have recently developed a highly effective nasal delivery system (CriticalSorb™) based on Solutol HS15. Extensive toxicology studies have shown CriticalSorb™ to be very well tolerated, non-toxic and non-irritant. Cell culture and ex vivo-isolated tissue studies have shown it to promote transport of molecules mainly via transcellular but also to some extent, via paracellular routes. Pharmacokinetic/pharmacodynamic studies in rats, rabbits, non-human primates and recently in man have demonstrated significantly enhanced systemic delivery of nasally administered proteins including insulin (~6 kDa) and human growth hormone (~22 kDa), and pharmacodynamics similar to those after subcutaneous injection. CriticalSorb™ therefore opens up the possibility of developing nasal spray formulations for macromolecules such as proteins.