Oral delivery of synthetic eel calcitonin, elcatonin, in rats

Oral Delivery of Mono-PEGylated sCT (Lys18) in Rats: Regional Difference in Stability and Hypocalcemic Effect

In the in vitro experiment using a luminal, mucosal, and fecal fluid/extract from jejunum and colon of a rat, Lys18-residue modified mono-PEG(2k)-sCT (Lys18-PEG(2K)-sCT) exhibited a longer half-life than salmon calcitonin (sCT) in a colonic fluid and its extract. A physical adsorption study showed that Lys18-PEG(2K)-sCT had lower adsorption in the feces than sCT over an 8-hr period. An absorption study of the sCT and Lys18-PEG(2K)-sCT from the jejunum and colon using an in situ closed-loop technique in anesthetized rats showed a dose-dependent reduction in the plasma Ca2+ level but to a certain limit. Furthermore, the hypocalcemic response by intracolonic administration was significantly higher than the intrajejunal one, demonstrating that the colon had better absorption. In particular, Lys18-PEG(2K)-sCT (5 microg/rats) produced the most pronounced hypocalcemia after the intracolonic administration, which resulted in a sustained reduction in the serum calcium level over an 8-hr period, with a maximum reduction (% max(d)) of 38% after 4 hr. The overall reduction in the serum calcium levels, which was expressed as the net change in the AUC relative to the control over an 8-hr period, was 25.51 +/- 3.38 for Lys18-PEG(2K)-sCT. The relative pharmacological bioavailability of the intracolonically administered Lys18-PEG(2K)-sCT was 2.1-fold higher than sCT and the absolute pharmacological bioavailability was 73.59% of i.v.-injected sCT in an 8-hr period. Overall, this study highlights the feasibility of the oral delivery of Lys18-PEG(2K)-sCT in achieving a sustained calcium-lowering effect.

A novel vitamin B12-nanosphere conjugate carrier system for peroral delivery of insulin

In spite of great potential, effective oral delivery of many vitamin B(12)-peptide/protein drug conjugates does not occur due to the limited uptake capacity of the VB(12) transport system, loss of bioactivity of native protein and/or intrinsic factor affinity of VB(12) and liability to GI degradation. In order to overcome these shortcomings in a two pronged way, we have endeavoured to develop a VB(12)-Nanoparticles (NPs) system to enhance the uptake capacity of both NPs and VB(12) transport to deliver orally effective insulin. NPs were prepared using different molecular weight dextrans and epichlorohydrin as cross-linker by an emulsion method. NPs surface was modified with succinic anhydride, and conjugated with amino VB(12) derivatives of carbamate linkage. VB(12) attachment was confirmed by IR, XPS analysis, and was quantified by HPLC (4.0 to 4.4% w/w of NPs). The pre-formed NPs conjugates (Zave=160-250 nm; polydisperse) were loaded with 2, 3 and 4% w/w of insulin, and the entrapment was found to be 45-70%. NPs conjugates were found to protect 65-83% of entrapped insulin against in vitro gut proteases. In vitro release studies exhibit an initial burst followed by diffusion controlled first order kinetics with 75-95% release within 48 h. After oral administration of these carriers (20 IU/kg), a nadir of 70-75% reduction in plasma glucose was found in 5 h, reached basal levels in 8-10 h, and a prolonged second phase was found until 54 h. The % pharmacological availability (PA) of 70 K NPs conjugate containing 2, 3 and 4% w/w insulin was 1.1, 1.9 and 2.6 fold higher, respectively compared to NPs without VB(12); consistent with the hypothesis that uptake was mediated by the vitamin B(12) transport. NPs of 70 K dextran showed 1.4 fold PA compared to 10 K while negligible action was observed with 200 K. The potential utilities of VB(12)-NPs carrier as an oral delivery platform of proteins, especially insulin via dextran-coated particles necessities further elaborate investigations.

Oral delivery of macromolecules using intestinal patches: applications for insulin delivery

Oral drug delivery, though attractive compared to injections, cannot be utilized for the administration of peptides and proteins due to poor epithelial permeability and proteolytic degradation within the gastrointestinal tract. A novel method is described that utilizes mucoadhesive intestinal patches to deliver therapeutic doses of insulin into systemic circulation. Intestinal patches localize insulin near the mucosa and protect it from proteolytic degradation. In vitro experiments confirmed the secure adhesion of patches to the intestine and the release of insulin from the patches. In vivo experiments performed via jejunal administration showed that intestinal insulin patches with doses in the range of 1-10 U/kg induced dose-dependent hypoglycemia in normal rats with a maximum drop in blood glucose levels of 75% observed at a dose of 10 U/kg. These studies demonstrate that reduction in blood glucose levels comparable to that induced by subcutaneous injections can be achieved via enteral insulin absorption with doses only 2-10-fold higher than subcutaneous doses.

Nanoparticles with specific bioadhesive properties to circumvent the pre-systemic degradation of fluorinated pyrimidines

The aim was to evaluate the potential of specific bioadhesive nanoparticles to increase the oral bioavailability of pre-systemic degraded drugs, using 5-fluorouridine (FURD) as model. For this purpose, poly(methylvinylether-co-maleic anhydride) nanoparticles (NP), NP coated with albumin (BSA-NP) and NP treated with albumin and 1,3-diaminopropane (BD-NP) were used. All the formulations displayed a similar size and drug loading. However, BSA-NP showed a tropism for the stomach, NP developed adhesive interactions with both the stomach and middle portions of the small intestine and BD-NP with the distal regions of the small intestine. These formulations were orally administered to laboratory animals and the FURD levels in plasma, tissues and urine were quantified at different times. From the urine data, the FURD bioavailability when loaded in either BSA-NP or NP was about 79% and 21%, respectively. For the control oral solution and BD-NP this parameter was 11% and 2%, respectively. FURD metabolism in gut was assessed by HPLC analysis of the lumen content. A FURD metabolite was found. Comparing the three nanoparticle formulations, the presence of the metabolite in the lumen contents was significantly higher for BD-NP than for NP and BSA-NP. In summary, the use of bioadhesive nanoparticles with tropism for the stomach mucosa may be considered as an adequate alternative to increase the bioavailability of some pre-systemic metabolised drugs.

Reversible lipidization for the oral delivery of salmon calcitonin

Salmon calcitonin (sCT), a 32-amino-acid polypeptide, was lipidized by using a reversible aqueous lipidization (REAL) technology. When injected subcutaneously into mice, the AUC of REAL-sCT was four times greater than that of sCT and a similar pattern of reduction in plasma calcium level was observed. The therapeutic effect of REAL-sCT was evaluated in ovariectomized (OVX) rats. The development of osteoporosis in OVX rats was determined by measuring the urinary level of deoxypyridinoline (DPD), a biochemical marker of bone resorption. It was found that the DPD levels were significantly reduced in rats that were orally administered a dose of 50 microg/kg/day of REAL-sCT. No reduction in urinary DPD levels could be detected in OVX rats treated similarly with unmodified sCT. In addition, significant levels of sCT were detected in rat plasma up to 12 h after oral administration of REAL-sCT at 500 microg/kg, while the plasma concentration of sCT was undetectable at 1 h after oral administration with the same dose of sCT. The AUC of oral REAL-sCT was at least 19 times higher than that of sCT. Our results indicate that reversibly lipidized polypeptides exhibit not only improved pharmacokinetic and pharmacodynamic behaviors, but also an enhanced oral bioavailability.