Development of canagliflozin nanocrystals sublingual tablets in the presence of sodium caprate permeability enhancer: formulation optimization, characterization, in-vitro, in silico, and in-vivo study.

Canagliflozin (CFZ) is a sodium-glucose cotransporter-2 inhibitor (SGLT2) that lowers albuminuria in type-2 diabetic patients, cardiovascular, kidney, and liver disease. CFZ is classified as class IV in the Biopharmaceutical Classification System (BCS) and is characterized by low permeability, solubility, and bioavailability, most likely attributed to hepatic first-pass metabolism. Nanocrystal-based sublingual formulations were developed in the presence of sodium caprate, as a wetting agent, and as a permeability enhancer. This formulation is suitable for children and adults and could enhance solubility, permeability, and avoid enterohepatic circulation due to absorption through the sublingual mucosa. In the present study, formulations containing various surfactants (P237, P338, PVA, and PVP K30) were prepared by the Sono-homo-assisted precipitation ion technique. The optimized formula prepared with PVP-K30 showed the smallest particle size (157 ± 0.32 nm), Zeta-potential (-18 ± 0.01), and morphology by TEM analysis. The optimized formula was subsequently formulated into a sublingual tablet containing Pharma burst-V® with a shorter disintegration time (51s) for the in-vivo study. The selected sublingual tablet improved histological and biochemical markers (blood glucose, liver, and kidney function), AMP-activated protein kinase (AMPK), and protein kinase B (AKT) pathway compared to the market formula, increased CFZ's antidiabetic potency in diabetic rabbits, boosted bioavailability by five-fold, and produced faster onset of action. These findings suggest successful treatment of diabetes with CFZ nanocrystal-sublingual tablets.

Characterization of the physicochemical interactions between exenatide and two intestinal permeation enhancers: Sodium caprate (C10) and salcaprozate sodium (SNAC).

A common approach to tackle the poor intestinal membrane permeability of peptides after oral administration is to formulate them with a permeation enhancer (PE). Increased oral bioavailability for oral peptide candidates has been reported from clinical trials when either salcaprozate sodium (SNAC) or sodium caprate (C10) is incorporated in the formulation. However, little is known about how they physically interact with peptides in solution. Our objective was to compare the biophysical interactions between the GLP-1 analogue exenatide (Byetta®, Lilly), and C10 or SNAC using a variety of advanced analytical techniques. First, critical micelle concentration was measured in different buffers for both PEs. Dynamic light scattering (DLS) measurements revealed specific supramolecular structures arising from exenatide-PE association. Surface plasmon resonance (SPR) indicated the formation of exenatide-PE complexes with a high contribution from non-specific interactions and rapid binding kinetics, resulting in overall low affinities. DLS and isothermal titration calorimetry (ITC) were used to examine the supramolecular organization of the PEs, and revealed thermodynamic signatures characterized by unfavourable enthalpic contributions compensated by favourable entropic ones, but with low-affinity estimates in water (KD in the 10-100 µM range). With affinity capillary electrophoresis (ACE), weak interactions between exenatide and SNAC or C10 were confirmed in saline, with a dissociation constant around 10 µM and 30 µM respectively. In biorelevant intestinal media, the bile salts in FaSSIF and FeSSIF further reduced the binding of both agents to exenatide (KD ≈ 100 µM), indicating that the interaction between the PEs and exenatide might be inhibited by bile salts in the GI lumen. This study suggests that the interactions of both PEs with exenatide follow a similar non-covalent mechanism and are of low affinity.

Microcontainers for oral insulin delivery - In vitro studies of permeation enhancement.

Oral delivery of peptides is challenging due to their low uptake through the small intestinal epithelium. Tight junctions, connecting the enterocytes, impede permeability, often necessitating the use of permeation enhancers in the formulation. Loading of peptide and permeation enhancer into micro-scale devices, such as microcontainers, can potentially confine the effective absorptive area through unidirectional release and thereby enhance absorption. This concept is investigated by in vitro permeation studies of insulin across Caco-2 cell and Caco-2/HT29-MTX-E12 co-culture monolayers mimicking the intestinal absorption barrier. The importance of proximity between the microcontainers and the barrier is assessed, by keeping the amounts of insulin and sodium caprate fixed throughout all experiments, while collectively orienting the unidirectional release towards the cell monolayers. Increasing the distance is observed to have a negative effect on insulin permeation matching a one-phase exponential decay function, while no difference in insulin transport is observed between Caco-2 and co-culture monolayers. Although there are no signs of cytotoxicity caused by the microcontainer material, reversible cell deterioration, as a consequence of high local concentrations of sodium caprate, becomes evident upon qualitative assessment of the cell monolayers. These results both suggest a potential of increasing oral bioavailability of peptides by the use of microcontainers, while simultaneously visualising the ability of regaining monolayer integrity upon local permeation enhancer induced toxicity.