Patent Review
For reprint orders, please contact [email protected]
Oral insulin-delivery system for diabetes mellitus
Current insulin therapy for diabetes mellitus involves frequent dosing of subcutaneous injections, causing local discomfort, patient noncompliance, hypoglycemia and hyperinsulinemia, among others. While noninvasive therapy through oral delivery is greatly desired, there are challenges that include low bioavailability due to rapid enzymatic degradation in the stomach, inactivation and digestion by proteolytic enzymes in the intestinal lumen, poor permeability across the intestinal epithelium and poor stability. This article reviews patents that provide novel approaches for oral insulin delivery to the bloodstream through the GI tract.
Brief details of the criteria employed to select the patents under review Patents and published patent applications related to oral insulin delivery were searched by combining the following three concepts : (1) oral drug delivery; (2) insulin, and (3) diabetes. Patent classes (both international patent class and US patent class) were also used. For the purposes of this present article, we analyzed patents and published patent applications that were published from 2008 to 2014. Oral insulin delivery: general overview & current challenges Diabetes (both Type 1 diabetes and Type 2 diabetes) is one of the leading causes of death globally, with expenditures of over US$376 billion in 2010, which are estimated to become $490 billion in 2030 [1] . Over the next 20 years, approximately 592 million people will be affected globally by diabetes [2] , making insulin-delivery systems a major research area [3–5] . The main existing and near-term delivery systems to treat diabetic mellitus are summarized in Figure 1. The existing delivery methods for diabetes mellitus mostly use subcutaneous routes for insulin delivery. The most prominent challenge with the subcutaneous route of insulin delivery is patient noncompliance. The next considerable challenge is that insulin administered
10.4155/PPA.14.53 © 2015 Future Science Ltd
Minakshi Kanzarkar1, Prem Prakash Pathak*,1, Mandar Vaidya1, Charles Brumlik1 & Abhishek Choudhury1 Nanobiz LLC & Cocreate Consulting Pvt. Ltd. 3322 US Hwy 22 West, Suite 421, Branchburg, NJ 08876, USA *Author for correspondence: [email protected]
1
subcutaneously cannot be controlled by the metabolic activities of the liver, thereby often causing peripheral hyperinsulinemia [6] . Hyperinsulinemia leads to increased glucose uptake, glycogen synthesis, glycolysis, fatty acid synthesis and triacylglycerol synthesis. Subcutaneous administration of insulin also causes other complications, such as the development of atherosclerosis, cancer, hypoglycemia and other adverse metabolic effects. Repeated injection also causes injection site issues, such as lipodystrophy or lipoatrophy and lipo hypertrophy [7] . In order to help diabetic patients overcome these injection-related problems, several noninvasive approaches for insulin delivery and therapies are being developed. Patents and publications regarding several noninvasive approaches for insulin delivery are proliferating. Some of the more common examples include: intranasal [8] , inhaled [9] , rectal [10] , implanted insulin-producing cells (gene therapy) [11] , β-cell or pancreatic transplants [12] and stem cell therapy [13] . This article focuses on oral insulin delivery via the GI tract (GIT) because this has the highest patient compliance and avoids the discomfort and disadvantages of the subcutaneous route of insulin delivery. In addition, the oral route of insulin delivery provides ease of administration, eliminates the pain caused by injection, decreases chances
Pharm. Pat. Anal. (2015) 4(1), 29–36
part of
ISSN 2046-8954
29
Patent Review Kanzarkar, Pathak, Vaidya, Brumlik & Choudhury
Solution for diabetic mellitus Therapies
Insulin delivery Invasive route Intravenous infusion
Gene therapy
Non-invasive route Oral
Transdermal
Nasal
Ocular
Rectal
Vaginal Stem cell therapy
Iontophoresis Per-oral gastrointestinal Subcutaneous infusion
Sonophoresis
Islet cell or pancreas transplantation
Buccal & sublingual
Figure 1. Delivery methods for treating diabetic mellitus. The dark gray box highlights the focus of this article.
of infection, improves the absorption rate and mimics the normal route of insulin secretion [6] . Oral insulin is delivered directly into the liver via portal circulation, which is similar to endogenously produced insulin [7] . Challenges in oral insulin delivery via GIT & possible approaches to solve them Currently, the oral bioavailability of most oral protein-based drugs such as insulin is less than 1%. Therefore, the main focus of the oral delivery of proteinbased drugs is on improving their bioavailability to 30–50% [14] . There are several challenges in increasing the bioavailability of insulin. The patents describing approaches to solve the challenges in the oral delivery of insulin are summarized below. Enzymatic & pH degradation of insulin in the GIT
Insulin undergoes rapid degradation in the stomach and the GIT due to enzymatic activities and harsh pH conditions. Pepsin and pancreatic proteolytic enzymes such as trypsin and α-chymotrypsin causes degradation of insulin in the GIT [15] . Overall, insulin is subjected to acid-catalyzed degradation in the stomach, luminal degradation in the intestine and intracellular degradation. In addition, 50% of the insulin that reaches the liver is degraded inside the liver via first-pass hepatic insulin extraction. These processes lead to poor bioavailability of insulin in the systemic circulation [4] . Therefore, there is a need for protecting insulin inside the GIT in order to increase its bioavailability. The main patent trends for avoiding the enzymatic and pH degradation of insulin are formulations with enzyme inhibitors or physical protection.
30
Pharm. Pat. Anal. (2015) 4(1)
Protection from pH denaturation & enzymatic degradation in the GIT
A pH-sensitive system should not release insulin within the stomach, but rather should carry it safely to the higher-pH region of the intestine in order to minimize the acidic degradation of insulin. Universidade de Coimbra [16] uses gelled submicron particles of insulin immobilized within a matrix of sodium alginate with calcium carbonate as an immobilizing agent. They are coated with two layers that are themselves capable of enhancing the absorption of insulin across the intestinal mucosal tissues and of inhibiting degradation by gastric enzymes. Insulin is immobilized by emulsification within these gelled particles. Chitosan acetate and paraffin oil aid the emulsification. The first coating agent is a blend of hydrophilic polymers, such as chitosan acetate, PEG and calcium chloride. The second coating material that coats the primary submicron particles is albumin. These gelled submicron particles can provide protection against the protease enzymes and adverse pH conditions in the GIT. Hydrogels are cross-linked networks of hydrophilic polymers with pH-dependent water swellability. These polymers have lower swellability indices at the lower pH in the stomach, but have higher swellability indices in the higher-pH region of the intestine. The pH-dependent swellability of these polymers makes them suitable carriers of insulin in the GIT. Their general degradability enables safe transport through the stomach to the intestine. There are good data on hydrogel that describe their importance in oral insulin delivery [17,18] . Reliance Life Science Pvt Ltd [19,20] uses pH-sensitive copolymers of poly(methacrylic acid-co-N-vinyl caprolactam) for the pH-sensitive oral delivery of active ingredients such
future science group
Oral insulin-delivery system for diabetes mellitus
as insulin. They also use controlled release formulations in which insulin is encapsulated into microspheres using pH-sensitive and biocompatible polymers [21,22] . These microspheres are produced by double emulsion solvent evaporation. The pH-sensitive biodegradable copolymer is made of the EUDRAGIT® (Evonik) acrylic drug delivery polymer as an enteric coating polymer that releases insulin only at neutral pH, thereby preventing its degradation at acidic pH. Hydrogels of poly(methacrylic acidco-N-vinyl caprolactam) polymers and EUDRAGIT shrink at a pH of 1.2 in order to protect insulin, and swell at a pH of 7.4 in order to release insulin at neutral pH within the intestine. Smolko [23] uses immobilized insulin in polymeric hydrogels formed from alkyl-methacrylate and acrylates polymerized with γ-radiation at very low temperatures (-78°C) and using glycerin as a free radical scavenger. The formulation is resistant to stomach acid. Oramed Ltd [24] uses two protease inhibitors called ‘serpins’ in order to reduce the enzymatic degradation of insulin. Common serpins are lima bean trypsin inhibitor, aprotinin, soybean trypsin inhibitor (SBTI) or ovomucoid. The first protease inhibitor is serpin SBTI and the second protease inhibitor can be aprotinin, cysteine protease inhibitor, threonine protease inhibitor, aspartic protease inhibitor or a metalloprotease inhibitor. Omega-3 fatty acid in combination with SBTI shows a synergistic effect in terms of the absorption of insulin in the GIT. The Inserm Institute [25] uses variant-specific surface proteins (VSPs) obtained from Giardia spp. as carriers for the delivery of insulin. VSP carriers are resistant to acidic pH and to proteolytic degradation and therefore they can protect insulin from degradation in the GIT. These VSP carriers are based on the 573-amino acid sequence with a protein purification tag sequence. Novo Nordisk [26] reports that a mutation of the insulin molecule at a position close to protease cleavage sites increases its stability against protease enzymes. The sitespecific mutations involve substitution of hydrophobic amino acids with hydrophilic amino acids. Insulin is further conjugated with PEG. The PEGylation of insulin is carried out at the ɛ-amino group of the lysine residue in position B29. This PEGylated insulin is stable against the protease enzyme and has higher bioavailability compared with simple PEGylated insulin. Bennis [27] uses a phosphate buffer formulation in order to protect insulin from digestive enzymes without using any protease inhibitors. Novo Nordisk [28] sought to deliver single-chain insulin precursors that are more stable against proteolytic degradation than their double-chain mature analogs that are currently available on the market. This single-chain insulin precursor has a general structure of D–B–C–A–E,
future science group
Patent Review
where A is the human insulin A chain, B is the human insulin B chain, C is a peptide chain of 0–15 amino acid residues connecting the C-terminal amino acid residue in the B chain with the N-terminal amino acid residue in the A chain, D is a N-terminal extension peptide on the B chain of 0–15 amino acid residues and E is a C-terminal extension peptide on the A chain of 0–15 amino acid residues. The insulin available on market is sold in its active state, which is a double-chain form consisting of A and B chains joined together by a disulfide linkage. Under normal physiological conditions, insulin is produced as a single-chain precursor consisting of A and B chains connected by a C-peptide chain. The C-peptide chain is cleaved by endopeptidases or exoproteases, such as carboxypeptidase-E, in order to produce the active or mature insulin that waits for the stimulation to enter into the circulation on demand. However, when the mature double-chain insulin is delivered orally, it undergoes enzymatic degradation in the GIT. Novo Nordisk [28] single-chain insulin becomes double-chain insulin after enzymatic degradation in the GIT. Liposomes are vesicles made up of either one or more lipid bilayers alternating with aqueous compartments. These vesicles encapsulate both hydrophobic and hydrophilic drugs to protect them from enzymatic attack in the GIT. The liposomes are generally unstable and thus need to be lyophilized for long-term storage. Insulin can be protected from enzymatic attack inside the GIT by preparing insulin in the form of liposomes. SDG, Inc. (an Ohio Corporation) [29] describes a method of preparing orally bioavailable insulin formulations of variously sized liposome constructs, such as liposome fragments, lipid particles comprising insulin, gelatin and targeting agents such as biotin. Fan [30] describes a process of lyophilization of insulin liposome powder. Here, insulin is in the Key terms Type 1 diabetes: A form of diabetes mellitus that results from the autoimmune destruction of the insulin-producing β-cells in the pancreatic islets. Type 2 diabetes: A metabolic disorder that is characterized by hyperglycaemia (high blood sugar) in the context of insulin resistance or a relative lack of insulin. Hyperinsulinemia: A condition in which there is an excess level of insulin circulating in the blood. Lipodystrophy: A condition characterized by the loss of fat from an area of repeated injection. Lipohypertrophy: A condition characterized by the deposition of extra fat at a site of repeated injection. Bioavailability: The fraction of unchanged drug available in the systemic circulation. Liposomes: Vesicles made up of either one or more lipid bilayers alternating with aqueous compartments.
www.future-science.com
31
Patent Review Kanzarkar, Pathak, Vaidya, Brumlik & Choudhury aqueous phase and cholesterol, lecithin and ethanol in oil phases are mixed, homogenized and lyophilized in order to form insulin liposome freeze-dried powders. Poor transport of insulin across the epithelial cell membrane
Oral drugs are absorbed within the GIT either by a transcellular route or a paracellular route [31] . In the paracellular route, movement of a drug molecule through a tight junction from apical to basolateral compartments depends on its permeability through the tight junction. Insulin has low lipophilicity, with an octanol–water partition coefficient of approximately 0.0215. Furthermore, the isoelectric point of insulin is approximately 5, and hence insulin is negatively charged at the neutral pH of the small intestine. Thus, entry into the cell membrane is unfavorable. As there is no evidence of active transport for insulin across the intestinal mucosa [32] , the primary pathway available for the transport of insulin across the epithelium is the aqueous paracellular pathway [33] . The absorption of insulin through the GIT can be increased by the use of permeation enhancers. Permeation enhancers increase the absorption of oral drugs in the GIT either by disruption of the cell membrane or by tight junction modulation with tight junction agonists [34] . The concern with permeation enhancers is that they act by local inflammation and thus can cause GIT infections [35] . Ideally, the impact of the permeation enhancers should be reversible and also noncytotoxic. In general, surfactants, bile salts, fatty acids and biomolecules such as chitosan are used as penetration enhancers in oral drug formulations [36] . Permeation enhancers open up the tight junctions of cell membrane and help with paracellular drug uptake. Enhancing transport of insulin across the epithelial cell membrane
Sharma and Mannemcherril at the Council of Scientific and Industrial Research (CSIR) [37] describe methods for facilitating the transport of insulin through the paracellular route by encapsulating insulin into polymeric nanoparticles. These nanoparticles can be easily absorbed through Peyer’s patches or M cells, which have good drug particle absorption. Peyer’s patches are aggregated lymphoid nodules that are associated with the follicle-associated epithelium and M cells in the GIT [38] . The CSIR uses pH-sensitive polymeric nanoparticle formulations of fatty acids and polymers that form a lipid–polymer complex. This complex protects the insulin from the harsh gastrointestinal environment. The submicrometer scale of the formulation also enhances the efficient transport of insulin across the epithelial cell membrane. These nanoparticles are prepared from water-in-oil emulsions.
32
Pharm. Pat. Anal. (2015) 4(1)
The polymers used in nanoparticle preparations include alginates, derivatized chitosan, derivatized pullulan, gellan gum and xanthan gum. The oils are edible-grade coconut oil, groundnut oil, rice bran oil, olive oil, palm kernel oil, palm oil and blends of these oils. Alba Therapeutics Corp. [39] uses a peptide (with 6–15 amino acid residues) as a zonula occludens toxin (ZOT) receptor agonist. This peptide acts as a noncytotoxic permeation enhancer for modulating the tight junctions of the epithelial cell membrane. ZOT is a protein that is present on the outer membranes of Vibrio cholerae, a pathogenic bacterium that causes cholera. ZOT is capable of reversibly opening the tight junctions between cells and increasing the paracellular transport of many drugs. Novo Nordisk [40] uses fatty acid-acylated amino acids as permeation enhancers for the oral delivery of insulin. Fatty acid-acylated amino acids are mild biodegradable surfactants with low toxicity and are soluble at intestinal pH. Examples of fatty acid-acylated amino acids include sodium lauroyl alaninate, N-dodecanoyl-l-alanine, sodium lauroyl asparaginate and N-dodecanoyl-l-asparagine. Emisphere Technologies, Inc. [41,42] describes a formulation of insulin with monosodium N-(4-chlorosalicyloyl)-4-aminobutyrate as a carrier for enhancing insulin’s bioavailability. GP Medical, Inc. [43] describes preparing nanoparticles by adding poly-γ-glutamic acid solution to regular-molecular-weight chitosan solution. These nanoparticles enhance insulin transport across epithelial cell membranes. Chitosan is a cationic polysaccharide derived from chitin by alkaline deacetylation. It is nontoxic and soft-tissue compatible. In addition, it is known that chitosan has a special property of adhering to the mucosal surface and transiently opening the tight junctions between epithelial cells. Furthermore, chitosan, along with heparin and PEG, is used to prepare nanolayer coatings on insulin in order to increase its loading capacity and bioavailability by decreasing its solubility in acidic pH [44] . The Nano and Advanced Material Institute [45] uses a pH-sensitive nanoparticle emulsion system containing hydroxypropyl methylcellulose phthalate and sodium alginate as the immobilizing agent. The pH-sensitive nanoparticle emulsion contains chitosan acetate as the primary coating and an albumin as the secondary coating. These nanoparticle emulsions prepared by double emulsion solvent evaporation have higher bioavailability than conventional emulsions prepared by the single-emulsion solvent diffusion method. Oshadi Drug Administration Ltd [46] make microparticles containing a noncovalently associated mixture of pharmacologically inert, hydrophobic silica
future science group
Oral insulin-delivery system for diabetes mellitus
nanoparticles, polysaccharides and insulin suspended in oil. The oil acts as a penetration enhancer that increases the bioavailability of insulin. Syracuse University [47] optimizes the link between insulin and vitamin B12 in order to maintain their functional activities while increasing the uptake of insulin within the GIT. Insulin is covalently linked to vitamin B12 at the 5′-hydroxyl group of the ribose moiety of the α-ligand. The length of the linkage is optimized so that the biological activity of both vitamin B12 and insulin is maintained. The conjugation of insulin with vitamin B12 facilitates insulin’s absorption in the GIT via the vitamin B12-intrinsic factor uptake mechanism and increases insulin’s residence time. Intrinsic factors are natural transport proteins that help with the uptake of large molecules, such as vitamin B12, within the GIT. Biocon Ltd [48] has also found that the bioavailability of insulin can be
Patent Review
increased by acylation, conjugation with long-chain carboxylic acids, conjugation with PEG and the formation of a cationic salt with a divalent cation of zinc or dietary substances, such vitamin B12. Receptor-mediated degradation
Glucose uptake by cells is activated by the formation of insulin receptor complexes. The insulin receptor is a transmembrane receptor that belongs to the large class of tyrosine kinase receptors [49] . Binding of insulin with the insulin receptor initiates glucose uptake in normal cases, whereas its improper functioning leads to diabetes and cancer [50,51] . After insulin has completed its function, the insulin receptor complex is taken inside the cells by endocytosis and degraded by insulin-degrading enzymes. The bioefficacy and bioavailability of insulin can be increased by minimizing its receptor-mediated degradation.
Challenges
Approaches
1. Encapsulating insulin by A) Gelled submicron particles [16]
Enzymatic degradation
Oral insulin delivery (gastrointestinal route)
Poor transport of insulin across epithelium membrane
Dosage form stability
Receptor-mediated degradation
Stability of insulin in dosage form
B) pH-sensitive copolymer [19, 21, 23] C) Enzyme Inhibitor [24, 26] D) Variant specific surface protein from Giardia Sp. [25] 2. Use of buffer [27] 3. Dosage form modification [29, 30] 4. Insulin modification [28]
Enhancing insulin permeability across epithelium by 1. Encapsulating insulin in nanoparticle [37, 45, 46] 2. Use of permeation enhancer [39–43] 3. Vitamin B12 as carrier [47, 48]
Self (micro or nano) emulsifying drug-delivery system (SMEDDS; or SNEDDS) [53] Use of betaines [52]
Insulin modification [54]
Figure 2. Summary of the challenges and promising approaches for oral insulin delivery via the gastrointestinal route.
future science group
www.future-science.com
33
Patent Review Kanzarkar, Pathak, Vaidya, Brumlik & Choudhury
Key term Betaine: N-trimethylated amino acids with a positive charge.
Minimizing receptor-mediated degradation
Bio Ethic [52] uses insulin–betaine complex to minimize receptor-mediated degradation. Betaines are N-trimethylated amino acids with a positive charge. The negatively charged insulin becomes covalently bonded with the positively charged betaine, thereby decreasing the receptor binding capacity and lowering receptor-mediated degradation. Dosage-form stability
Self-microemulsifying drug delivery systems (SMEDDs) and self-nanoemulsifying drug delivery systems (SNEDDs) are microemulsion and nanoemulsion preconcentrates. SMEDD or SNEDD formulations are isotropic mixtures containing a surfactant, a solubilizing agent, oil and excipients. SMEDDs or SNEDDs form microemulsions or nanoemulsions upon coming into contact with water (with or without agitation). SMEDD or SNEDD formulations are thermodynamically stable and also increase the bioavailability and solubility of oral drugs. Although SMEDDs and SNEDDs are known to increase the bioavailability of hydrophobic drugs, preparing them for insulin (a hydrophilic peptide) is challenging because of its low solubility. SMEDD & SNEDD formulations for insulin
Novo Nordisk [53] uses SMEDD or SNEDD formulations for oral insulin delivery. These consist of insulin, a semipolar protic organic solvent (e.g., glycerol or propylene glycol) and two nonionic surfactants, such as C8 fatty acids (caprylates), C10 fatty acids (caprates) or C12 fatty acids (laurates) with a hydrophilic–lipophilic balance of above 10. The hydrophilic–lipophilic balance of the two nonionic surfactants has been kept above 10 in order to increase the drug loading capacity and bioavailability. Stability of insulin in the dosage form
Compounds such as aldehydes and ketones are often used in pharmaceutical compositions that degrade insulin and decrease its shelf life.
Insulin modification to increase its stability in the dosage form
Novo Nordisk [54] has shown that insulin’s shelf life can be increased by N-terminal modification with an N-terminal-protecting group, such as carbamoyl, thiocarbamoyl, C1–C4 chain acyl groups, oxalyl, glutaryl and diglycolyl. These groups remove the normal positive or partly positive charge of the N-terminal amino groups of insulin at physiological pH, making it either neutral or negatively charged. Conclusion Oral insulin delivery via GIT is one of the promising approach among the non-invasive approaches for treatment of diabetes yet very challenging. The main focus of research in oral insulin delivery is concentrated towards overcoming insulin degradation and enhancing its absorption in GIT. Other challenges such as receptor mediated degradation of insulin, dosage form stability and stability of insulin in dosage form are also being addressed. Improved patient compliance with oral insulin has attracted companies like Novo Nordisk, Oramed, Emisphere and Biocon to put their endeavor in bringing it to market in near future. Future perspective The major challenges in the oral delivery of insulin and promising approaches are summarized in Figure 2. Insulin modification seems to be a very promising approach for the oral delivery of insulin in the future because it can survive within the GIT [28] , as well as having a longer shelf life [54] . The initial cost for the modified insulin could be high, but with developments in biosimilars, these cost could be reduced [3] . Financial & competing interests disclosure The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties. No writing assistance was utilized in the production of this manuscript.
Executive summary • The main systemic challenges in the oral delivery of insulin are its enzymatic degradation, the transport of insulin across the epithelial membrane and the receptor-mediated degradation of insulin. • The main formulation challenge relates to the stability of insulin in its dosage form. • A particularly interesting approach uses vitamin B12 as a carrier for effective insulin transport across epithelial cell membranes. • Major players in oral insulin development worldwide are Novo Nordisk, Oramed, Emisphere and Biocon. Novo Nordisk is trying to develop the oral delivery of insulin through multiple approaches.
34
Pharm. Pat. Anal. (2015) 4(1)
future science group
Oral insulin-delivery system for diabetes mellitus
References
25
Inserm Institut. US20140011739 (2014).
Papers of special note have been highlighted as: • of interest; •• of considerable interest
26
Novo Nordisk. US20120071402 (2012).
27
Bennis F. US8309123 (2012).
28
Novo Nordisk. WO2009133099 (2009).
29
SDG, Inc. (an Ohio Corporation). US20090087479 (2010).
•
References [16, 19-21, 23-29] describe the protection of insulin from enzymatic and pH degradation.
30
Fan S. WO2013040784 (2013).
31
Gowthamarajan K, Kulkarni GT. Oral insulin – fact or fiction? Resonance 8(5), 38–46 (2003).
32
Singh S, Patel D, Patel NR et al. Insulin oral delivery may be possible. Int. J. Pharma Prof. Res. 1(1), 24–51 (2010).
33
Sharma A, Arora S. Commercial challenges and emerging trends in oral delivery of peptide and protein drugs: A review. Res. J. Pharm. Biol. Chem. Sci. 2(3), 778–790 (2011).
34
Kavimandana NJ, Peppas NA. Confocal microscopic analysis of transport mechanisms of insulin across the cell monolayer. Int. J. Pharm. 354(1–2), 143–148 (2008).
35
Madhav M. Long-awaited dream of oral insulin: where did we reach? Asian J. Pharm. Clin. Res. 4(2), 15–20 (2011).
36
Shaikh MS, Nikita D, Derle D, Bhamber R. Permeability Enhancement techniques for poorly permeable drugs: a review. J. Appl. Pharm. Sci. 2(6) 34–39 (2012).
37
Council of Scientific and Industrial Research. US20090098205 (2009).
38
Lopes MA, Abrahim BA, Cabral LM et al. Intestinal absorption of insulin nanoparticles: contribution of M cells. Nanomedicine 10, 1139–1151 (2014).
39
Alba Therapeutics Corp. EP1993356 (2008).
40
Novo Nordisk. US20140056953 (2014).
41
Emisphere Technologies, Inc. US7429564 (2008).
42
Emisphere Technologies, Inc. US20100151009 (2010).
43
GP Medical, Inc. US8361439 (2013).
1
2
3
Zhang P, Zhang X, Brown J et al. Global healthcare expenditure on diabetes for 2010 and 2030. Diabetes Res. Clin. Pract. 87(3), 293–301 (2010). Guariguata L, Whiting DR, Hambleton I, Beagley J, Linnenkamp U, Shaw JE. Global estimates of diabetes prevalence for 2013 and projections for 2035. Diabetes Res. Clin. Pract. 103(2), 137–149 (2014). Rotenstein RL, Ran N, Shivers PJ, Yarchoan M, Close KL. Opportunities and challenges for biosimilars: what’s on the horizon in the global insulin market? Clin. Diabetes 30(4), 138–150 (2012).
4
Park K, Kwon IC, Park K. Oral protein delivery: current status and future prospect. React. Funct. Polym. 71, 280–287 (2011).
5
Al Tabakha MM, Arida AI. Recent challenges in insulin delivery systems: a review. Indian J. Pharm. Sci. 70(3), 278–286 (2008).
6
Fonte P, Araújo A, Reis S, Sarmento BP. Oral insulin delivery: how far are we? J. Diabetes Sci. Technol. 7(2), 520–531 (2013).
7
Yogendraji KA, Lokwani P, Singh N. Newer strategies for insulin delivery. Int. J. Res. Ayurveda Pharm. 2(6), 1717–1721 (2011).
8
Marina Biotech, Inc. US20120094903 (2012).
9
Novo Nordisk. US20080099011 (2008).
10
Oramed Pharmaceuticals, Inc. WO2008132731 (2010).
11
Viacyte, Inc. US20140257515 (2014).
12
Insugen, LLC. US8119120 (2012).
13
Shire Human Genetic Therapies, Inc. US20100143314 (2010).
14
Owens DR. New horizons – alternative routes for insulin therapy. Nat. Rev. Drug Discov. 1, 529–540 (2002).
15
Balsubramanian J, Narayanan N, Mohan V, Bindu MS. Nanotechnology based oral delivery of insulin – a retrospect. Int. J. Res. Ayurveda Pharm. 2(4), 144–150 (2013).
16
Universidade de Coimbra. EP2120894 (2009).
44
17
Chaturvedi K, Ganguly K, Nadagouda MN, Aminabhavi TM. Polymeric hydrogels for oral insulin delivery. J. Control. Release 165, 129–138 (2013).
Song L, Zhi LZ, Pickup JC. Nanolayer encapsulation of insulin–chitosan complexes improves efficiency of oral insulin delivery. Int. J. Nanomed. 9, 2127–2136 (2014).
45
18
Babu VR, Patel P, Mundargi RC, Rangaswamy V, Aminabhavi TM. Developments in polymeric devices for oral insulin delivery. Expert Opin. Drug Deliv. 5(4), 403–415 (2008).
Nano and Advanced Material Institute. US20130034589 (2013).
46
Oshadi Drug Administration Ltd. US20100278922 (2010).
47
Syracuse University. US20110092416 (2011).
19
Reliance Life Science Pvt Ltd. WO2010113176 (2010).
20
Mundargi RC, Rangaswamy V, Aminabhavi TM. Poly(Nvinylcaprolactam-co-methacrylic acid) hydrogel microparticles for oral insulin delivery. J. Microencapsulation 28(5), 384–394 (2011).
21
Reliance Life Science Pvt Ltd: WO2010113177 (2010).
22
Mundargi RC, Rangaswamy V, Aminabhavi TM. pHsensitive oral insulin delivery systems using Eudragit microspheres. Drug Dev. Ind. Pharm. 37(8), 977–985 (2011).
23
Smolko EE. US8414923 (2013).
24
Oramed Ltd. EP2279244 (2011).
future science group
48
Biocon Ltd. US8563685 (2013).
•
References [37, 39-43, 45-48] discuss methods of enhancing transport of insulin across the epithelial cell membrane.
49
Ward CW, Lawrence MC. Ligand-induced activation of the insulin receptor: a multi-step process involving structural changes in both the ligand and the receptor. Bioessays 31, 422–434 (2009).
50
Ebina Y, Ellis L. The human insulin receptor cDNA: the structural basis for hormone-activated transmembrane signalling. Cell 40(4), 747–758 (1985).
51
Malaguarnera R, Belfiore A. Proinsulin binds with high affinity the insulin receptor isoform A and predominantly
www.future-science.com
Patent Review
35
Patent Review Kanzarkar, Pathak, Vaidya, Brumlik & Choudhury activates the mitogenic pathway. Endocrinology 155(5), 2152–2163 (2012).
36
••
Describes a method for avoiding receptor-mediated degradation.
52
Bio Ethic. US7780990 (2010).
Pharm. Pat. Anal. (2015) 4(1)
53
Novo Nordisk. EP2523655 (2012).
••
Describes a method for insulin modification in order to decrease its degradation in a dosage form.
54
Novo Nordisk. EP2627670 (2013).
future science group
For reprint orders, please contact [email protected]
Oral insulin-delivery system for diabetes mellitus
Current insulin therapy for diabetes mellitus involves frequent dosing of subcutaneous injections, causing local discomfort, patient noncompliance, hypoglycemia and hyperinsulinemia, among others. While noninvasive therapy through oral delivery is greatly desired, there are challenges that include low bioavailability due to rapid enzymatic degradation in the stomach, inactivation and digestion by proteolytic enzymes in the intestinal lumen, poor permeability across the intestinal epithelium and poor stability. This article reviews patents that provide novel approaches for oral insulin delivery to the bloodstream through the GI tract.
Brief details of the criteria employed to select the patents under review Patents and published patent applications related to oral insulin delivery were searched by combining the following three concepts : (1) oral drug delivery; (2) insulin, and (3) diabetes. Patent classes (both international patent class and US patent class) were also used. For the purposes of this present article, we analyzed patents and published patent applications that were published from 2008 to 2014. Oral insulin delivery: general overview & current challenges Diabetes (both Type 1 diabetes and Type 2 diabetes) is one of the leading causes of death globally, with expenditures of over US$376 billion in 2010, which are estimated to become $490 billion in 2030 [1] . Over the next 20 years, approximately 592 million people will be affected globally by diabetes [2] , making insulin-delivery systems a major research area [3–5] . The main existing and near-term delivery systems to treat diabetic mellitus are summarized in Figure 1. The existing delivery methods for diabetes mellitus mostly use subcutaneous routes for insulin delivery. The most prominent challenge with the subcutaneous route of insulin delivery is patient noncompliance. The next considerable challenge is that insulin administered
10.4155/PPA.14.53 © 2015 Future Science Ltd
Minakshi Kanzarkar1, Prem Prakash Pathak*,1, Mandar Vaidya1, Charles Brumlik1 & Abhishek Choudhury1 Nanobiz LLC & Cocreate Consulting Pvt. Ltd. 3322 US Hwy 22 West, Suite 421, Branchburg, NJ 08876, USA *Author for correspondence: [email protected]
1
subcutaneously cannot be controlled by the metabolic activities of the liver, thereby often causing peripheral hyperinsulinemia [6] . Hyperinsulinemia leads to increased glucose uptake, glycogen synthesis, glycolysis, fatty acid synthesis and triacylglycerol synthesis. Subcutaneous administration of insulin also causes other complications, such as the development of atherosclerosis, cancer, hypoglycemia and other adverse metabolic effects. Repeated injection also causes injection site issues, such as lipodystrophy or lipoatrophy and lipo hypertrophy [7] . In order to help diabetic patients overcome these injection-related problems, several noninvasive approaches for insulin delivery and therapies are being developed. Patents and publications regarding several noninvasive approaches for insulin delivery are proliferating. Some of the more common examples include: intranasal [8] , inhaled [9] , rectal [10] , implanted insulin-producing cells (gene therapy) [11] , β-cell or pancreatic transplants [12] and stem cell therapy [13] . This article focuses on oral insulin delivery via the GI tract (GIT) because this has the highest patient compliance and avoids the discomfort and disadvantages of the subcutaneous route of insulin delivery. In addition, the oral route of insulin delivery provides ease of administration, eliminates the pain caused by injection, decreases chances
Pharm. Pat. Anal. (2015) 4(1), 29–36
part of
ISSN 2046-8954
29
Patent Review Kanzarkar, Pathak, Vaidya, Brumlik & Choudhury
Solution for diabetic mellitus Therapies
Insulin delivery Invasive route Intravenous infusion
Gene therapy
Non-invasive route Oral
Transdermal
Nasal
Ocular
Rectal
Vaginal Stem cell therapy
Iontophoresis Per-oral gastrointestinal Subcutaneous infusion
Sonophoresis
Islet cell or pancreas transplantation
Buccal & sublingual
Figure 1. Delivery methods for treating diabetic mellitus. The dark gray box highlights the focus of this article.
of infection, improves the absorption rate and mimics the normal route of insulin secretion [6] . Oral insulin is delivered directly into the liver via portal circulation, which is similar to endogenously produced insulin [7] . Challenges in oral insulin delivery via GIT & possible approaches to solve them Currently, the oral bioavailability of most oral protein-based drugs such as insulin is less than 1%. Therefore, the main focus of the oral delivery of proteinbased drugs is on improving their bioavailability to 30–50% [14] . There are several challenges in increasing the bioavailability of insulin. The patents describing approaches to solve the challenges in the oral delivery of insulin are summarized below. Enzymatic & pH degradation of insulin in the GIT
Insulin undergoes rapid degradation in the stomach and the GIT due to enzymatic activities and harsh pH conditions. Pepsin and pancreatic proteolytic enzymes such as trypsin and α-chymotrypsin causes degradation of insulin in the GIT [15] . Overall, insulin is subjected to acid-catalyzed degradation in the stomach, luminal degradation in the intestine and intracellular degradation. In addition, 50% of the insulin that reaches the liver is degraded inside the liver via first-pass hepatic insulin extraction. These processes lead to poor bioavailability of insulin in the systemic circulation [4] . Therefore, there is a need for protecting insulin inside the GIT in order to increase its bioavailability. The main patent trends for avoiding the enzymatic and pH degradation of insulin are formulations with enzyme inhibitors or physical protection.
30
Pharm. Pat. Anal. (2015) 4(1)
Protection from pH denaturation & enzymatic degradation in the GIT
A pH-sensitive system should not release insulin within the stomach, but rather should carry it safely to the higher-pH region of the intestine in order to minimize the acidic degradation of insulin. Universidade de Coimbra [16] uses gelled submicron particles of insulin immobilized within a matrix of sodium alginate with calcium carbonate as an immobilizing agent. They are coated with two layers that are themselves capable of enhancing the absorption of insulin across the intestinal mucosal tissues and of inhibiting degradation by gastric enzymes. Insulin is immobilized by emulsification within these gelled particles. Chitosan acetate and paraffin oil aid the emulsification. The first coating agent is a blend of hydrophilic polymers, such as chitosan acetate, PEG and calcium chloride. The second coating material that coats the primary submicron particles is albumin. These gelled submicron particles can provide protection against the protease enzymes and adverse pH conditions in the GIT. Hydrogels are cross-linked networks of hydrophilic polymers with pH-dependent water swellability. These polymers have lower swellability indices at the lower pH in the stomach, but have higher swellability indices in the higher-pH region of the intestine. The pH-dependent swellability of these polymers makes them suitable carriers of insulin in the GIT. Their general degradability enables safe transport through the stomach to the intestine. There are good data on hydrogel that describe their importance in oral insulin delivery [17,18] . Reliance Life Science Pvt Ltd [19,20] uses pH-sensitive copolymers of poly(methacrylic acid-co-N-vinyl caprolactam) for the pH-sensitive oral delivery of active ingredients such
future science group
Oral insulin-delivery system for diabetes mellitus
as insulin. They also use controlled release formulations in which insulin is encapsulated into microspheres using pH-sensitive and biocompatible polymers [21,22] . These microspheres are produced by double emulsion solvent evaporation. The pH-sensitive biodegradable copolymer is made of the EUDRAGIT® (Evonik) acrylic drug delivery polymer as an enteric coating polymer that releases insulin only at neutral pH, thereby preventing its degradation at acidic pH. Hydrogels of poly(methacrylic acidco-N-vinyl caprolactam) polymers and EUDRAGIT shrink at a pH of 1.2 in order to protect insulin, and swell at a pH of 7.4 in order to release insulin at neutral pH within the intestine. Smolko [23] uses immobilized insulin in polymeric hydrogels formed from alkyl-methacrylate and acrylates polymerized with γ-radiation at very low temperatures (-78°C) and using glycerin as a free radical scavenger. The formulation is resistant to stomach acid. Oramed Ltd [24] uses two protease inhibitors called ‘serpins’ in order to reduce the enzymatic degradation of insulin. Common serpins are lima bean trypsin inhibitor, aprotinin, soybean trypsin inhibitor (SBTI) or ovomucoid. The first protease inhibitor is serpin SBTI and the second protease inhibitor can be aprotinin, cysteine protease inhibitor, threonine protease inhibitor, aspartic protease inhibitor or a metalloprotease inhibitor. Omega-3 fatty acid in combination with SBTI shows a synergistic effect in terms of the absorption of insulin in the GIT. The Inserm Institute [25] uses variant-specific surface proteins (VSPs) obtained from Giardia spp. as carriers for the delivery of insulin. VSP carriers are resistant to acidic pH and to proteolytic degradation and therefore they can protect insulin from degradation in the GIT. These VSP carriers are based on the 573-amino acid sequence with a protein purification tag sequence. Novo Nordisk [26] reports that a mutation of the insulin molecule at a position close to protease cleavage sites increases its stability against protease enzymes. The sitespecific mutations involve substitution of hydrophobic amino acids with hydrophilic amino acids. Insulin is further conjugated with PEG. The PEGylation of insulin is carried out at the ɛ-amino group of the lysine residue in position B29. This PEGylated insulin is stable against the protease enzyme and has higher bioavailability compared with simple PEGylated insulin. Bennis [27] uses a phosphate buffer formulation in order to protect insulin from digestive enzymes without using any protease inhibitors. Novo Nordisk [28] sought to deliver single-chain insulin precursors that are more stable against proteolytic degradation than their double-chain mature analogs that are currently available on the market. This single-chain insulin precursor has a general structure of D–B–C–A–E,
future science group
Patent Review
where A is the human insulin A chain, B is the human insulin B chain, C is a peptide chain of 0–15 amino acid residues connecting the C-terminal amino acid residue in the B chain with the N-terminal amino acid residue in the A chain, D is a N-terminal extension peptide on the B chain of 0–15 amino acid residues and E is a C-terminal extension peptide on the A chain of 0–15 amino acid residues. The insulin available on market is sold in its active state, which is a double-chain form consisting of A and B chains joined together by a disulfide linkage. Under normal physiological conditions, insulin is produced as a single-chain precursor consisting of A and B chains connected by a C-peptide chain. The C-peptide chain is cleaved by endopeptidases or exoproteases, such as carboxypeptidase-E, in order to produce the active or mature insulin that waits for the stimulation to enter into the circulation on demand. However, when the mature double-chain insulin is delivered orally, it undergoes enzymatic degradation in the GIT. Novo Nordisk [28] single-chain insulin becomes double-chain insulin after enzymatic degradation in the GIT. Liposomes are vesicles made up of either one or more lipid bilayers alternating with aqueous compartments. These vesicles encapsulate both hydrophobic and hydrophilic drugs to protect them from enzymatic attack in the GIT. The liposomes are generally unstable and thus need to be lyophilized for long-term storage. Insulin can be protected from enzymatic attack inside the GIT by preparing insulin in the form of liposomes. SDG, Inc. (an Ohio Corporation) [29] describes a method of preparing orally bioavailable insulin formulations of variously sized liposome constructs, such as liposome fragments, lipid particles comprising insulin, gelatin and targeting agents such as biotin. Fan [30] describes a process of lyophilization of insulin liposome powder. Here, insulin is in the Key terms Type 1 diabetes: A form of diabetes mellitus that results from the autoimmune destruction of the insulin-producing β-cells in the pancreatic islets. Type 2 diabetes: A metabolic disorder that is characterized by hyperglycaemia (high blood sugar) in the context of insulin resistance or a relative lack of insulin. Hyperinsulinemia: A condition in which there is an excess level of insulin circulating in the blood. Lipodystrophy: A condition characterized by the loss of fat from an area of repeated injection. Lipohypertrophy: A condition characterized by the deposition of extra fat at a site of repeated injection. Bioavailability: The fraction of unchanged drug available in the systemic circulation. Liposomes: Vesicles made up of either one or more lipid bilayers alternating with aqueous compartments.
www.future-science.com
31
Patent Review Kanzarkar, Pathak, Vaidya, Brumlik & Choudhury aqueous phase and cholesterol, lecithin and ethanol in oil phases are mixed, homogenized and lyophilized in order to form insulin liposome freeze-dried powders. Poor transport of insulin across the epithelial cell membrane
Oral drugs are absorbed within the GIT either by a transcellular route or a paracellular route [31] . In the paracellular route, movement of a drug molecule through a tight junction from apical to basolateral compartments depends on its permeability through the tight junction. Insulin has low lipophilicity, with an octanol–water partition coefficient of approximately 0.0215. Furthermore, the isoelectric point of insulin is approximately 5, and hence insulin is negatively charged at the neutral pH of the small intestine. Thus, entry into the cell membrane is unfavorable. As there is no evidence of active transport for insulin across the intestinal mucosa [32] , the primary pathway available for the transport of insulin across the epithelium is the aqueous paracellular pathway [33] . The absorption of insulin through the GIT can be increased by the use of permeation enhancers. Permeation enhancers increase the absorption of oral drugs in the GIT either by disruption of the cell membrane or by tight junction modulation with tight junction agonists [34] . The concern with permeation enhancers is that they act by local inflammation and thus can cause GIT infections [35] . Ideally, the impact of the permeation enhancers should be reversible and also noncytotoxic. In general, surfactants, bile salts, fatty acids and biomolecules such as chitosan are used as penetration enhancers in oral drug formulations [36] . Permeation enhancers open up the tight junctions of cell membrane and help with paracellular drug uptake. Enhancing transport of insulin across the epithelial cell membrane
Sharma and Mannemcherril at the Council of Scientific and Industrial Research (CSIR) [37] describe methods for facilitating the transport of insulin through the paracellular route by encapsulating insulin into polymeric nanoparticles. These nanoparticles can be easily absorbed through Peyer’s patches or M cells, which have good drug particle absorption. Peyer’s patches are aggregated lymphoid nodules that are associated with the follicle-associated epithelium and M cells in the GIT [38] . The CSIR uses pH-sensitive polymeric nanoparticle formulations of fatty acids and polymers that form a lipid–polymer complex. This complex protects the insulin from the harsh gastrointestinal environment. The submicrometer scale of the formulation also enhances the efficient transport of insulin across the epithelial cell membrane. These nanoparticles are prepared from water-in-oil emulsions.
32
Pharm. Pat. Anal. (2015) 4(1)
The polymers used in nanoparticle preparations include alginates, derivatized chitosan, derivatized pullulan, gellan gum and xanthan gum. The oils are edible-grade coconut oil, groundnut oil, rice bran oil, olive oil, palm kernel oil, palm oil and blends of these oils. Alba Therapeutics Corp. [39] uses a peptide (with 6–15 amino acid residues) as a zonula occludens toxin (ZOT) receptor agonist. This peptide acts as a noncytotoxic permeation enhancer for modulating the tight junctions of the epithelial cell membrane. ZOT is a protein that is present on the outer membranes of Vibrio cholerae, a pathogenic bacterium that causes cholera. ZOT is capable of reversibly opening the tight junctions between cells and increasing the paracellular transport of many drugs. Novo Nordisk [40] uses fatty acid-acylated amino acids as permeation enhancers for the oral delivery of insulin. Fatty acid-acylated amino acids are mild biodegradable surfactants with low toxicity and are soluble at intestinal pH. Examples of fatty acid-acylated amino acids include sodium lauroyl alaninate, N-dodecanoyl-l-alanine, sodium lauroyl asparaginate and N-dodecanoyl-l-asparagine. Emisphere Technologies, Inc. [41,42] describes a formulation of insulin with monosodium N-(4-chlorosalicyloyl)-4-aminobutyrate as a carrier for enhancing insulin’s bioavailability. GP Medical, Inc. [43] describes preparing nanoparticles by adding poly-γ-glutamic acid solution to regular-molecular-weight chitosan solution. These nanoparticles enhance insulin transport across epithelial cell membranes. Chitosan is a cationic polysaccharide derived from chitin by alkaline deacetylation. It is nontoxic and soft-tissue compatible. In addition, it is known that chitosan has a special property of adhering to the mucosal surface and transiently opening the tight junctions between epithelial cells. Furthermore, chitosan, along with heparin and PEG, is used to prepare nanolayer coatings on insulin in order to increase its loading capacity and bioavailability by decreasing its solubility in acidic pH [44] . The Nano and Advanced Material Institute [45] uses a pH-sensitive nanoparticle emulsion system containing hydroxypropyl methylcellulose phthalate and sodium alginate as the immobilizing agent. The pH-sensitive nanoparticle emulsion contains chitosan acetate as the primary coating and an albumin as the secondary coating. These nanoparticle emulsions prepared by double emulsion solvent evaporation have higher bioavailability than conventional emulsions prepared by the single-emulsion solvent diffusion method. Oshadi Drug Administration Ltd [46] make microparticles containing a noncovalently associated mixture of pharmacologically inert, hydrophobic silica
future science group
Oral insulin-delivery system for diabetes mellitus
nanoparticles, polysaccharides and insulin suspended in oil. The oil acts as a penetration enhancer that increases the bioavailability of insulin. Syracuse University [47] optimizes the link between insulin and vitamin B12 in order to maintain their functional activities while increasing the uptake of insulin within the GIT. Insulin is covalently linked to vitamin B12 at the 5′-hydroxyl group of the ribose moiety of the α-ligand. The length of the linkage is optimized so that the biological activity of both vitamin B12 and insulin is maintained. The conjugation of insulin with vitamin B12 facilitates insulin’s absorption in the GIT via the vitamin B12-intrinsic factor uptake mechanism and increases insulin’s residence time. Intrinsic factors are natural transport proteins that help with the uptake of large molecules, such as vitamin B12, within the GIT. Biocon Ltd [48] has also found that the bioavailability of insulin can be
Patent Review
increased by acylation, conjugation with long-chain carboxylic acids, conjugation with PEG and the formation of a cationic salt with a divalent cation of zinc or dietary substances, such vitamin B12. Receptor-mediated degradation
Glucose uptake by cells is activated by the formation of insulin receptor complexes. The insulin receptor is a transmembrane receptor that belongs to the large class of tyrosine kinase receptors [49] . Binding of insulin with the insulin receptor initiates glucose uptake in normal cases, whereas its improper functioning leads to diabetes and cancer [50,51] . After insulin has completed its function, the insulin receptor complex is taken inside the cells by endocytosis and degraded by insulin-degrading enzymes. The bioefficacy and bioavailability of insulin can be increased by minimizing its receptor-mediated degradation.
Challenges
Approaches
1. Encapsulating insulin by A) Gelled submicron particles [16]
Enzymatic degradation
Oral insulin delivery (gastrointestinal route)
Poor transport of insulin across epithelium membrane
Dosage form stability
Receptor-mediated degradation
Stability of insulin in dosage form
B) pH-sensitive copolymer [19, 21, 23] C) Enzyme Inhibitor [24, 26] D) Variant specific surface protein from Giardia Sp. [25] 2. Use of buffer [27] 3. Dosage form modification [29, 30] 4. Insulin modification [28]
Enhancing insulin permeability across epithelium by 1. Encapsulating insulin in nanoparticle [37, 45, 46] 2. Use of permeation enhancer [39–43] 3. Vitamin B12 as carrier [47, 48]
Self (micro or nano) emulsifying drug-delivery system (SMEDDS; or SNEDDS) [53] Use of betaines [52]
Insulin modification [54]
Figure 2. Summary of the challenges and promising approaches for oral insulin delivery via the gastrointestinal route.
future science group
www.future-science.com
33
Patent Review Kanzarkar, Pathak, Vaidya, Brumlik & Choudhury
Key term Betaine: N-trimethylated amino acids with a positive charge.
Minimizing receptor-mediated degradation
Bio Ethic [52] uses insulin–betaine complex to minimize receptor-mediated degradation. Betaines are N-trimethylated amino acids with a positive charge. The negatively charged insulin becomes covalently bonded with the positively charged betaine, thereby decreasing the receptor binding capacity and lowering receptor-mediated degradation. Dosage-form stability
Self-microemulsifying drug delivery systems (SMEDDs) and self-nanoemulsifying drug delivery systems (SNEDDs) are microemulsion and nanoemulsion preconcentrates. SMEDD or SNEDD formulations are isotropic mixtures containing a surfactant, a solubilizing agent, oil and excipients. SMEDDs or SNEDDs form microemulsions or nanoemulsions upon coming into contact with water (with or without agitation). SMEDD or SNEDD formulations are thermodynamically stable and also increase the bioavailability and solubility of oral drugs. Although SMEDDs and SNEDDs are known to increase the bioavailability of hydrophobic drugs, preparing them for insulin (a hydrophilic peptide) is challenging because of its low solubility. SMEDD & SNEDD formulations for insulin
Novo Nordisk [53] uses SMEDD or SNEDD formulations for oral insulin delivery. These consist of insulin, a semipolar protic organic solvent (e.g., glycerol or propylene glycol) and two nonionic surfactants, such as C8 fatty acids (caprylates), C10 fatty acids (caprates) or C12 fatty acids (laurates) with a hydrophilic–lipophilic balance of above 10. The hydrophilic–lipophilic balance of the two nonionic surfactants has been kept above 10 in order to increase the drug loading capacity and bioavailability. Stability of insulin in the dosage form
Compounds such as aldehydes and ketones are often used in pharmaceutical compositions that degrade insulin and decrease its shelf life.
Insulin modification to increase its stability in the dosage form
Novo Nordisk [54] has shown that insulin’s shelf life can be increased by N-terminal modification with an N-terminal-protecting group, such as carbamoyl, thiocarbamoyl, C1–C4 chain acyl groups, oxalyl, glutaryl and diglycolyl. These groups remove the normal positive or partly positive charge of the N-terminal amino groups of insulin at physiological pH, making it either neutral or negatively charged. Conclusion Oral insulin delivery via GIT is one of the promising approach among the non-invasive approaches for treatment of diabetes yet very challenging. The main focus of research in oral insulin delivery is concentrated towards overcoming insulin degradation and enhancing its absorption in GIT. Other challenges such as receptor mediated degradation of insulin, dosage form stability and stability of insulin in dosage form are also being addressed. Improved patient compliance with oral insulin has attracted companies like Novo Nordisk, Oramed, Emisphere and Biocon to put their endeavor in bringing it to market in near future. Future perspective The major challenges in the oral delivery of insulin and promising approaches are summarized in Figure 2. Insulin modification seems to be a very promising approach for the oral delivery of insulin in the future because it can survive within the GIT [28] , as well as having a longer shelf life [54] . The initial cost for the modified insulin could be high, but with developments in biosimilars, these cost could be reduced [3] . Financial & competing interests disclosure The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties. No writing assistance was utilized in the production of this manuscript.
Executive summary • The main systemic challenges in the oral delivery of insulin are its enzymatic degradation, the transport of insulin across the epithelial membrane and the receptor-mediated degradation of insulin. • The main formulation challenge relates to the stability of insulin in its dosage form. • A particularly interesting approach uses vitamin B12 as a carrier for effective insulin transport across epithelial cell membranes. • Major players in oral insulin development worldwide are Novo Nordisk, Oramed, Emisphere and Biocon. Novo Nordisk is trying to develop the oral delivery of insulin through multiple approaches.
34
Pharm. Pat. Anal. (2015) 4(1)
future science group
Oral insulin-delivery system for diabetes mellitus
References
25
Inserm Institut. US20140011739 (2014).
Papers of special note have been highlighted as: • of interest; •• of considerable interest
26
Novo Nordisk. US20120071402 (2012).
27
Bennis F. US8309123 (2012).
28
Novo Nordisk. WO2009133099 (2009).
29
SDG, Inc. (an Ohio Corporation). US20090087479 (2010).
•
References [16, 19-21, 23-29] describe the protection of insulin from enzymatic and pH degradation.
30
Fan S. WO2013040784 (2013).
31
Gowthamarajan K, Kulkarni GT. Oral insulin – fact or fiction? Resonance 8(5), 38–46 (2003).
32
Singh S, Patel D, Patel NR et al. Insulin oral delivery may be possible. Int. J. Pharma Prof. Res. 1(1), 24–51 (2010).
33
Sharma A, Arora S. Commercial challenges and emerging trends in oral delivery of peptide and protein drugs: A review. Res. J. Pharm. Biol. Chem. Sci. 2(3), 778–790 (2011).
34
Kavimandana NJ, Peppas NA. Confocal microscopic analysis of transport mechanisms of insulin across the cell monolayer. Int. J. Pharm. 354(1–2), 143–148 (2008).
35
Madhav M. Long-awaited dream of oral insulin: where did we reach? Asian J. Pharm. Clin. Res. 4(2), 15–20 (2011).
36
Shaikh MS, Nikita D, Derle D, Bhamber R. Permeability Enhancement techniques for poorly permeable drugs: a review. J. Appl. Pharm. Sci. 2(6) 34–39 (2012).
37
Council of Scientific and Industrial Research. US20090098205 (2009).
38
Lopes MA, Abrahim BA, Cabral LM et al. Intestinal absorption of insulin nanoparticles: contribution of M cells. Nanomedicine 10, 1139–1151 (2014).
39
Alba Therapeutics Corp. EP1993356 (2008).
40
Novo Nordisk. US20140056953 (2014).
41
Emisphere Technologies, Inc. US7429564 (2008).
42
Emisphere Technologies, Inc. US20100151009 (2010).
43
GP Medical, Inc. US8361439 (2013).
1
2
3
Zhang P, Zhang X, Brown J et al. Global healthcare expenditure on diabetes for 2010 and 2030. Diabetes Res. Clin. Pract. 87(3), 293–301 (2010). Guariguata L, Whiting DR, Hambleton I, Beagley J, Linnenkamp U, Shaw JE. Global estimates of diabetes prevalence for 2013 and projections for 2035. Diabetes Res. Clin. Pract. 103(2), 137–149 (2014). Rotenstein RL, Ran N, Shivers PJ, Yarchoan M, Close KL. Opportunities and challenges for biosimilars: what’s on the horizon in the global insulin market? Clin. Diabetes 30(4), 138–150 (2012).
4
Park K, Kwon IC, Park K. Oral protein delivery: current status and future prospect. React. Funct. Polym. 71, 280–287 (2011).
5
Al Tabakha MM, Arida AI. Recent challenges in insulin delivery systems: a review. Indian J. Pharm. Sci. 70(3), 278–286 (2008).
6
Fonte P, Araújo A, Reis S, Sarmento BP. Oral insulin delivery: how far are we? J. Diabetes Sci. Technol. 7(2), 520–531 (2013).
7
Yogendraji KA, Lokwani P, Singh N. Newer strategies for insulin delivery. Int. J. Res. Ayurveda Pharm. 2(6), 1717–1721 (2011).
8
Marina Biotech, Inc. US20120094903 (2012).
9
Novo Nordisk. US20080099011 (2008).
10
Oramed Pharmaceuticals, Inc. WO2008132731 (2010).
11
Viacyte, Inc. US20140257515 (2014).
12
Insugen, LLC. US8119120 (2012).
13
Shire Human Genetic Therapies, Inc. US20100143314 (2010).
14
Owens DR. New horizons – alternative routes for insulin therapy. Nat. Rev. Drug Discov. 1, 529–540 (2002).
15
Balsubramanian J, Narayanan N, Mohan V, Bindu MS. Nanotechnology based oral delivery of insulin – a retrospect. Int. J. Res. Ayurveda Pharm. 2(4), 144–150 (2013).
16
Universidade de Coimbra. EP2120894 (2009).
44
17
Chaturvedi K, Ganguly K, Nadagouda MN, Aminabhavi TM. Polymeric hydrogels for oral insulin delivery. J. Control. Release 165, 129–138 (2013).
Song L, Zhi LZ, Pickup JC. Nanolayer encapsulation of insulin–chitosan complexes improves efficiency of oral insulin delivery. Int. J. Nanomed. 9, 2127–2136 (2014).
45
18
Babu VR, Patel P, Mundargi RC, Rangaswamy V, Aminabhavi TM. Developments in polymeric devices for oral insulin delivery. Expert Opin. Drug Deliv. 5(4), 403–415 (2008).
Nano and Advanced Material Institute. US20130034589 (2013).
46
Oshadi Drug Administration Ltd. US20100278922 (2010).
47
Syracuse University. US20110092416 (2011).
19
Reliance Life Science Pvt Ltd. WO2010113176 (2010).
20
Mundargi RC, Rangaswamy V, Aminabhavi TM. Poly(Nvinylcaprolactam-co-methacrylic acid) hydrogel microparticles for oral insulin delivery. J. Microencapsulation 28(5), 384–394 (2011).
21
Reliance Life Science Pvt Ltd: WO2010113177 (2010).
22
Mundargi RC, Rangaswamy V, Aminabhavi TM. pHsensitive oral insulin delivery systems using Eudragit microspheres. Drug Dev. Ind. Pharm. 37(8), 977–985 (2011).
23
Smolko EE. US8414923 (2013).
24
Oramed Ltd. EP2279244 (2011).
future science group
48
Biocon Ltd. US8563685 (2013).
•
References [37, 39-43, 45-48] discuss methods of enhancing transport of insulin across the epithelial cell membrane.
49
Ward CW, Lawrence MC. Ligand-induced activation of the insulin receptor: a multi-step process involving structural changes in both the ligand and the receptor. Bioessays 31, 422–434 (2009).
50
Ebina Y, Ellis L. The human insulin receptor cDNA: the structural basis for hormone-activated transmembrane signalling. Cell 40(4), 747–758 (1985).
51
Malaguarnera R, Belfiore A. Proinsulin binds with high affinity the insulin receptor isoform A and predominantly
www.future-science.com
Patent Review
35
Patent Review Kanzarkar, Pathak, Vaidya, Brumlik & Choudhury activates the mitogenic pathway. Endocrinology 155(5), 2152–2163 (2012).
36
••
Describes a method for avoiding receptor-mediated degradation.
52
Bio Ethic. US7780990 (2010).
Pharm. Pat. Anal. (2015) 4(1)
53
Novo Nordisk. EP2523655 (2012).
••
Describes a method for insulin modification in order to decrease its degradation in a dosage form.
54
Novo Nordisk. EP2627670 (2013).
future science group
