Ivan Coulter

Current status of selected oral peptide technologies in advanced preclinical development and in clinical trials

The development of oral dosage forms that allows absorption of therapeutic peptides to the systemic circulation is one of the greatest challenges for the pharmaceutical industry. Currently, a number of technologies including either mixtures of penetration enhancers or protease inhibitors and/or nanotechnology-based products are under clinical development. Typically, these formulations are presented in the form of enteric-coated tablets or capsules. Systems undergoing preclinical investigation include further advances in nanotechnology, including intestinal microneedle patches, as well as their combination with regional delivery to the colon. This review critically examines four selected promising oral peptide technologies at preclinical stage and the twelve that have progressed to clinical trials, as indicated in www.clinicaltrials.gov. We examined these technologies under the criteria of peptide selection, formulation design, system components and excipients, intestinal mechanism of action, efficacy in man, and safety issues. The conclusion is that most of the technologies in clinical trials are incremental rather than paradigm-shifting and that even the more clinically advanced oral peptide drugs examples of oral bioavailability appear to yield oral bioavailability values of only 1-2% and are, therefore, only currently suitable for a limited range of peptides.

Targeted delivery of the hydroxylase inhibitor DMOG provides enhanced efficacy with reduced systemic exposure in a murine model of colitis

Targeting hypoxia-sensitive pathways has recently been proposed as a new therapeutic approach to the treatment of intestinal inflammation. HIF-hydroxylases are enzymes which confer hypoxic-sensitivity upon the hypoxia-inducible factor (HIF), a major regulator of the adaptive response to hypoxia. Previous studies have shown that systemic (intraperitoneal) administration of hydroxylase inhibitors such as dimethyloxalylglycine (DMOG) is profoundly protective in multiple models of colitis, however the therapeutic potential of this approach is limited due to potential side-effects associated with systemic drug exposure and the fact that orally delivered DMOG is ineffective (likely due to drug inactivation by gastric acid). In order to overcome these issues, we formulated DMOG in a liquid emulsion drug delivery system which, when coated with specific polymer coatings, permits oral delivery of a reduced dose which is released locally throughout the colon. This colon-targeted DMOG formulation demonstrated increased relative colonic bioactivity with reduced systemic exposure and provided a similar degree of protection to systemic (intraperitoneal) administration at a 40-fold lower dose in DSS-induced colitis. In summary, targeted delivery of DMOG to the colon provides local protection resulting in enhanced efficacy with reduced systemic exposure in the treatment of colitis. This novel approach to targeting hydroxylase inhibitors to specific diseased regions of the GI tract may improve its potential as a new therapeutic in inflammatory bowel diseases such as ulcerative colitis.

Enhanced colonic delivery of ciclosporin A self-emulsifying drug delivery system encapsulated in coated minispheres

Abstract Objectives: Investigate the potential of coated minispheres (SmPill®) to enhance localized Ciclosporin A (CsA) delivery to the colon. Methods: CsA self-emulsifying drug delivery systems (SEDDS) were encapsulated into SmPill® minispheres. Varying degrees of coating thickness (low, medium and high) were applied using ethylcellulose and pectin (E:P) polymers. In vitro CsA release was evaluated in simulated gastric and intestinal media. Bioavailability of CsA in vivo following oral administration to pigs of SmPill® minispheres was compared to Neoral® po and Sandimmun® iv in a pig model. CsA concentrations in blood and intestinal tissue were determined by HPLC-UV. Results: In vitro CsA release from coated minispheres decreased with increasing coating thickness. A linear relationship was observed between in vitro CsA release and in vivo bioavailability (r2 = 0.98). CsA concentrations in the proximal, transverse and distal colon were significantly higher following administration of SmPill®, compared to Neoral® po and Sandimmun® iv (p < 0.05). Analysis of transverse colon tissue subsections also revealed significantly higher CsA concentrations in the mucosa and submucosa using SmPill® minispheres (p < 0.05). Conclusions: Modulating E:P coating thickness controls release of CsA from SmPill® minispheres. Coated minispheres limited CsA release in the small intestine and enhanced delivery and uptake in the colon. These findings demonstrate clinical advantages of an oral coated minisphere-enabled CsA formulation in the treatment of inflammatory conditions of the large intestine.

In vitro and in vivo preclinical evaluation of a minisphere emulsion-based formulation (SmPill®) of salmon calcitonin

Salmon calcitonin (sCT, MW 3432Da) is a benchmark molecule for an oral peptide delivery system because it is degraded and has low intestinal epithelial permeability. Four dry emulsion minisphere prototypes (SmPill®) containing sCT were co-formulated with permeation enhancers (PEs): sodium taurodeoxycholate (NaTDC), sodium caprate (C10) or coco-glucoside (CG), or with a pH acidifier, citric acid (CA). Minispheres protected sCT from thermal degradation and the released sCT retained high bioactivity, as determined by cyclic AMP generation in T47D cells. Pre-minisphere emulsions of PEs combined with sCT increased absolute bioavailability (F) compared to native sCT following rat intra-jejunal (i.j.) and intra-colonic (i.c.) loop instillations, an effect that was more pronounced in colon. Minispheres corresponding to ~2000I.U. (~390μg) sCT/kg were instilled by i.j. or i.c. instillations and hypocalcaemia resulted from all prototypes. The absolute F (i.j.) of sCT was 11.0, 4.8, and 1.4% for minispheres containing NaTDC (10μmol/kg), CG (12μmol/kg) or CA (32μmol/kg) respectively. For i.c. instillations, the largest absolute F (22% in each case) was achieved for minispheres containing either C10 (284μmol/kg) or CG (12μmol/kg), whilst the absolute F was 8.2% for minispheres loaded with CA (32μmol/kg). In terms of relative F, the best data were obtained for minispheres containing NaTDC (i.j.), a 4-fold increase over sCT solution, and also for either C10 or CG (i.c.), where there was a 3-fold increase over sCT solution. Histology of instilled intestinal loops indicated that neither the minispheres nor components thereof caused major perturbation. In conclusion, selected SmPill® minisphere formulations may have the potential to be used as oral peptide delivery systems when delivered to jejunum or colon.

A novel adjuvanted capsule based strategy for oral vaccination against infectious diarrhoeal pathogens

Diarrhoeal infections are a major cause of morbidity and mortality with enterotoxigenic Escherichia coli (ETEC) and cholera imposing a significant global burden. There is currently no licensed vaccine for ETEC. Development of new nonliving oral vaccines has proven difficult due to the physicochemical and immunological challenges associated with the oral route. This demands innovative delivery solutions to protect antigens, control their release and build in immune-stimulatory activity. We describe the Single Multiple Pill® (SmPill®) vaccine formulation which combines the benefits of enteric polymer coating to protect against low gastric pH, a dispersed phase to control release and aid the solubility of non-polar components and an optimized combination of adjuvant and antigen to promote mucosal immunity. We demonstrate the effectiveness of this system with whole cell killed E. coli overexpressing colonization factor antigen I (CFA/I), JT-49. Alpha-galactosylceramide was identified as a potent adjuvant within SmPill® that enhanced the immunogenicity of JT-49. The bacteria associated with the dispersed phase were retained within the capsules at gastric pH but released at intestinal pH. Vaccination with an optimized SmPill® formulation promoted CFA/I-specific immunoglobulin A (IgA) responses in the intestinal mucosa in addition to serum IgG and a solubilized adjuvant was indispensable for efficacy.

Coated minispheres of salmon calcitonin target rat intestinal regions to achieve systemic bioavailability: Comparison between intestinal instillation and oral gavage.

Achieving oral peptide delivery is an elusive challenge. Emulsion-based minispheres of salmon calcitonin (sCT) were synthesized using single multiple pill (SmPill®) technology incorporating the permeation enhancers (PEs): sodium taurodeoxycholate (NaTDC), sodium caprate (C10), or coco-glucoside (CG), or the pH acidifier, citric acid (CA). Minispheres were coated with an outer layer of Eudragit® L30 D-55 (designed for jejunal release) or Surelease®/Pectin (designed for colonic release). The process was mild and in vitro biological activity of sCT was retained upon release from minispheres stored up to 4months. In vitro release profiles suggested that sCT was released from minispheres by diffusion through coatings due to swelling of gelatin and the polymeric matrix upon contact with PBS at pH6.8. X-ray analysis confirmed that coated minispheres dissolved at the intended intestinal region of rats following oral gavage. Uncoated minispheres at a dose of ~2000I.U.sCT/kg were administered to rats by intra-jejunal (i.j.) or intra-colonic (i.c.) instillation and caused hypocalcaemia. Notable sCT absolute bioavailability (F) values were: 5.5% from minispheres containing NaTDC (i.j), 17.3% with CG (i.c.) and 18.2% with C10 (i.c.). Coated minispheres administered by oral gavage at threefold higher doses also induced hypocalcaemia. A highly competitive F value of 2.7% was obtained for orally-administered sCT-minispheres containing CG (45μmol/kg) and coated with Eudragit®. In conclusion, the SmPill® technology is a potential dosage form for several peptides when formulated with PEs and coated for regional delivery. PK data from instillations over-estimates oral bioavailability and poorly predicts rank ordering of formulations.

Microbeads: a novel multiparticulate drug delivery technology for increasing the solubility and dissolution of celecoxib.

Abstract The purpose of this study was to develop a novel multipaticulate drug delivery technology suitable for the delivery of pre-solubilized celecoxib to the gastrointestinal tract and more specifically to the colon. The solubility of celecoxib in a range of oils, surfactants and co-solvents was evaluated. Celecoxib was solubilized in mixtures of these vehicles to produce liquid formulations. The in vitro dissolution of these liquid formulations was assessed and the data obtained was used to design microbead formulations containing celecoxib dissolved within an emulsion/micellar solution core. Microbead formulations were optimized to increase drug loading, avoid precipitation and to achieve good in vitro dissolution performance. An optimized formulation with a celecoxib loading of 6% w/w was produced and yielded an in vitro dissolution result of 80% over 6 h. The structure of these microbead formulations was characterized using light microscopy to reveal a correlation between droplet size and dissolution performance.

Thermostability of the coating, antigen and immunostimulator in an adjuvanted oral capsule vaccine formulation

Oral vaccines present an attractive alternative to injectable vaccines for enteric diseases due to ease of delivery and the induction of intestinal immunity at the site of infection. However, susceptibility to gastrointestinal proteolysis, limited transepithelial uptake and a lack of clinically acceptable adjuvants present significant challenges. A further challenge to mass vaccination in developing countries is the very expensive requirement to maintain the cold chain. We recently described the effectiveness of a Single Multiple Pill® (SmPill®) adjuvanted capsule approach to enhance the effectiveness of a candidate enterotoxigenic Escherichia coli (ETEC) oral vaccine. Here it was demonstrated that this delivery system maintains the antigenicity of ETEC colonisation factor antigen I (CFA/I) and the immunostimulatory activity of the orally active α-Galactosylceramide (α-GalCer) adjuvant after storage of SmPill® minispheres under room temperature and extreme storage conditions for several months. In addition, the internal structure of the cores of SmPill® minispheres and antigen release features at intestinal pH were found to be preserved under all these conditions. However, changes in the surface morphology of SmPill® minispheres leading to the antigen release at gastric pH were observed after a few weeks of storage under extreme conditions. Those modifications were prevented by the introduction of an Opadry® White film coating layer between the core of SmPill® minispheres and the enteric coating. Under these conditions, protection against antigen release at gastric pH was maintained even under high temperature and humidity conditions. These results support the potential of the SmPill® minisphere approach to maintain the stability of an adjuvanted whole cell killed oral vaccine formulation.

In‐vitro characterisation of a novel celecoxib microbead formulation for the treatment and prevention of colorectal cancer

Colorectal cancer (CRC) is a life‐threatening disease that can develop as a consequence of a sustained chronic inflammatory pathology of the colon. Although not devoid of side effects, the anti‐inflammatory drug celecoxib (CLX) has been shown to exert protective effects in CRC therapy. The purpose of this study was to develop and characterise a novel CLX microbead formulation suitable for use in the treatment and prevention of CRC, which has the potential to minimise the side effects associated with CLX.