Advances in the oral delivery of proteins

Urease catalyzed high-density sodium alginate microspheres enable high oral bioavailability of macromolecular drugs

Destruction of insulin caused by the gastric microenvironment and rapid deactivation pose inevitable barriers to oral macromolecular absorption, especially for most peptide and protein drugs. In this study, we developed high-density sodium alginate microspheres composed of magnesium oxide and urease to address these challenges. These microspheres aim to anchor the gastric mucus layer and induce microenvironmental liquefaction, thereby enhancing gastric retention and the protection of insulin. The sedimentation test confirmed the capability of the Ins/Ur/MgO@SA microsphere to rapidly traverse the gastric juice under the influence of gravity. Additionally, the urease immobilized on the Ins/Ur/MgO@SA microspheres catalyzes the hydrolysis of urea in the gastric mucus and promotes the liquefaction of mucus, which is beneficial for microsphere retention. The inclusion of MgO particles and urease, acting as pHM modifiers, helps in adjusting the local pH to avoid gastric acid-induced damage. Subsequently, an in vivo pharmacokinetic experiment verified that the relative bioavailability of the p.o. Ins/Ur/MgO@SA treated group was 15-fold higher than that of the p.o.insulin treated group. Meanwhile, satisfactory blood glucose level (BGL) reduction was observed in diabetic animals. In conclusion, Ins/Ur/MgO@SA microspheres demonstrate high biocompatibility as insulin carriers with prolonged drug release time and increased gastric retention properties, showing a far-reaching strategy for oral macromolecular drug delivery.

Recent Advances in Oral and Transdermal Protein Delivery Systems

Protein and peptide drugs are predominantly administered by injection to achieve high bioavailability, but this greatly compromises patient compliance. Oral and transdermal drug delivery with minimal invasiveness and high adherence represent attractive alternatives to injection administration. However, oral and transdermal administration of bioactive proteins must overcome biological barriers, namely the gastrointestinal and skin barriers, respectively. The rapid development of new materials and technologies promises to address these physiological obstacles. This review provides an overview of the latest advances in oral and transdermal protein delivery, including chemical strategies, synthetic nanoparticles, medical microdevices, and biomimetic systems for oral administration, as well as chemical enhancers, physical approaches, and microneedles in transdermal delivery. We also discuss challenges and future perspectives of the field with a focus on innovation and translation.

Safety and efficacy of sodium caprate in promoting oral drug absorption: from in vitro to the clinic

A major challenge in oral drug delivery is the development of novel dosage forms to promote absorption of poorly permeable drugs across the intestinal epithelium. To date, no absorption promoter has been approved in a formulation specifically designed for oral delivery of Class III molecules. Promoters that are designated safe for human consumption have been licensed for use in a recently approved buccal insulin spray delivery system and also for many years as part of an ampicillin rectal suppository. Unlike buccal and rectal delivery, oral formulations containing absorption promoters have the additional technical hurdle whereby the promoter and payload must be co-released in high concentrations at the small intestinal epithelium in order to generate significant but rapidly reversible increases in permeability. An advanced promoter in the clinic is the medium chain fatty acid (MCFA), sodium caprate (C(10)), a compound already approved as a food additive. We discuss how it has evolved to a matrix tablet format suitable for administration to humans under the headings of mechanism of action at the cellular and tissue level as well as in vitro and in vivo efficacy and safety studies. In specific clinical examples, we review how C(10)-based formulations are being tested for oral delivery of bisphosphonates using Gastro Intestinal Permeation Enhancement Technology, GIPET (Merrion Pharmaceuticals, Ireland) and in a related solid dose format for antisense oligonucleotides (ISIS Pharmaceuticals, USA).

Challenges for the oral delivery of macromolecules

The rapid integration of new technologies by the pharmaceutical industry has resulted in numerous breakthroughs in the discovery, development and manufacturing of pharmaceutical products. In particular, the commercial-scale production of high-purity recombinant proteins has resulted in important additions to treatment options for many large therapeutic areas. In addition to proteins, other macromolecules, such as the animal-derived mucopolysaccharide heparins, have also seen dramatic growth as injectable pharmaceutical products. To date, macromolecules have been limited as therapeutics by the fact that they cannot be orally delivered. This article will address the current status and future possibilities of oral macromolecular drug delivery.

Gastrointestinal mucoadhesive patch system (GI-MAPS) for oral administration of G-CSF, a model protein

A new gastrointestinal mucoadhesive patch system (GI-MAPS) has been designed for the oral delivery of protein drugs. The system consists of four layered films, 3.0 x 3.0 mm2, contained in an enteric capsule. The 40 microm backing layer is made of a water-insoluble polymer, ethyl cellulose (EC). The surface layer is made of an enteric pH-sensitive polymer such as hydroxypropylmethylcellulose phthalate (HP-55), Eudragit L100 or S100 and was coated with an adhesive layer. The middle layer, drug-containing layer. made of cellulose membrane is attached to the EC backing layer by a heating press method. Both drug and pharmaceutical additives including an organic acid, citric acid, and a non-ionic surfactant, polyoxyethylated castor oil derivative (HCO-60), were formulated in the middle layer. The surface layer was attached to the middle layer by an adhesive layer made of carboxyvinyl polymer (Hiviswako 103). Fluorescein (FL), 30mg, was first used as a model drug for oral administration of GI-MAPS having different surface layers in beagle dogs. The plasma FL concentration vs. time profiles demonstrated that the targeting of the systems was obtained, because the Tmax, the time when plasma FL concentrations reaches to its maximum lelev, was 2.33+/-0.82 h for HP-55 system, 3.33+/-0.41 h for Eudragit L100 system and 5.00+/-0.00 h for Eudragit S100 system. The same three kinds of GI-MAPSs containing 125 microg of recombinant human granulocyte colony-stimulating factor (G-CSF) were prepared and orally administered to dogs and the increase in total white blood cell (WBC) counts were measured as the pharmacological index for G-CSF. Comparison with the total increase of WBCs after iv injection of the same amount of G-CSF (125 microg) indicated the pharmacological availabilities (PA) of G-CSF were 23%, 5.5% and 6.0% for Eudragit L100, HP-55 and Eudragit S100 systems. By decreasing the amount of HCO-60 and citric acid, the PA of G-CSF decreased. These results suggest the usefulness of GI-MAPS for the oral administration of proteins.

Retention and transit of intestinal mucoadhesive films in rat small intestine

The retention and transit characteristics of intestinal mucoadhesive film systems have been studied after intraduodenal administration in rats. Small size four layered film preparations, 0.5x0.5 mm, were prepared, where the backing layer (45.1+/-2.9 microm thick) was made of a water-insoluble polymer, ethylcellulose (EC), the surface layer was made of enteric pH-sensitive polymers, Eudragit L100, S100 or HP-55 and the middle layer was made of cellulose membrane. The surface layer was attached to the middle layer with an adhesive layer composed of carboxyvinyl polymer (Hiviswako(R) 103). After administration of ten films to the duodenum, the rats were sacrificed hourly and the distribution of the films in the whole small intestine was directly observed after abdominal incision. The HP-55, Eudragit L100 and S100 film systems were found to adhere to the upper, middle and lower part of the small intestine after 1, 2 and 4 h, respectively, for 2-3 h. Direct inspection study suggests that intestinal mucoadhesive film system has functions of: (1) pH-dependent intestinal adhesion site specificity; (2) adhesion to the intestinal wall; and (3) retention in the small intestinal adhesion site for at least 2 h. Intestinal mucoadhesive film system has been suggested to be a targeting system for drugs to the gastrointestinal tract.