See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/6850092
`
`Inhibition of dipeptidyl peptidase IV activity as
`a therapy of Type 2 diabetes
`
`Article in Expert Opinion on Emerging Drugs · October 2006
`
`DOI: 10.1517/14728214.11.3.525 · Source: PubMed
`
`CITATIONS
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`3 authors:
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`Brian D Green
`Queen's University Belfast
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`Peter R Flatt
`Ulster University
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`Aston University
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`Available from: Peter R Flatt
`Retrieved on: 08 November 2016
`
`Boehringer Ex. 2007
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`

`
`1. Introduction
`
`2. Background
`
`3. Medical need
`
`4. Existing treatment
`
`5. Drug development
`
`6. Current research goals
`
`7. Scientific rationale
`
`8. Competitive environment
`
`9. Potential development issues
`
`10. Expert opinion and conclusion
`
`For reprint orders,
`please contact:
`ben.fisher@informa.com
`
`Review
`
`Oncologic, Endocrine & Metabolic
`
`Inhibition of dipeptidyl
`peptidase IV activity as a therapy
`of Type 2 diabetes
`
`Brian D Green†, Peter R Flatt & Clifford J Bailey
`†Queens University Belfast, School of Biological Sciences, David Keir Building, Stranmillis Road,
`Belfast BT9 5AG, Northern Ireland
`
`Dipeptidyl peptidase IV (DPP IV) is a ubiquitous, multifunctional, serine pro-
`tease enzyme and receptor with roles in the control of endocrine and immune
`function, cell metabolism, growth and adhesion. As an enzyme, DPP IV
`cleaves the N-terminal dipeptide from the incretin hormones glucagon-like
`peptide-1 and glucose-dependent insulinotropic polypeptide. This inactivates
`the hormones, thereby cancelling their prandial insulinotropic effect. One
`approach to restore incretin activity as a therapy for Type 2 diabetes has been
`the development of DPP IV inhibitors. Inhibitors of DPP IV have shown effi-
`cacy and tolerability when used to control the hyperglycaemia of non-
`insulin-dependent animal models and human Type 2 diabetes. These DPP IV
`inhibitors prolong active incretin hormone concentrations and may exert
`additional antidiabetic effects. If long-term clinical trials confirm sustained
`and safe control of blood glucose, DPP IV inhibitors (known as ‘gliptins’) may
`be expected to provide a new treatment modality for Type 2 diabetes.
`
`Keywords: diabetes, dipeptidyl peptidase IV, incretin hormones
`
`Expert Opin. Emerging Drugs (2006) 11(3):525-539
`
`1. Introduction
`
`The concept of dipeptidyl peptidase IV (DPP IV) inhibitors arose through improve-
`ments in our understanding of the physiological inactivation of incretin hormones.
`The incretin hormones, glucagon-like peptide-1 (GLP-1) and glucose-dependent
`insulinotropic polypeptide (GIP) are sister hormones that potentiate postprandial
`insulin secretion and glucose clearance [1]. These peptides have pleiotropic effects on
`a range of tissues. Key actions, shown in Table 1, include the stimulation of insulin
`release from the pancreas [2], reduction of hepatic insulin clearance [3] and insulin-like
`effects on skeletal muscle [4-6], liver [7] and adipose tissue [8-11], which serve to pro-
`mote glucose uptake and metabolism. GLP-1 and GIP have beneficial actions on the
`pancreatic β-cell, such as expansion of cell mass and increased cell survival [12].
`The primary amino acid sequence of GLP-1 and GIP reveals a highly conserved
`alanine penultimate to the N-terminus, thus making these peptides ideal putative
`substrates for DPP IV (Figure 1). The major metabolites generated by DPP IV
`processing of GLP-1 and GIP, namely GLP-1(9-36)amide and GIP(3-42), respec-
`tively, retain the ability to bind to their specific receptors, but are rendered non-
`insulinotropic (Figure 2) [13-16]. The action of ubiquitous DPP IV reduces the
`half-life in vivo of GLP-1 and GIP to < 2 min [13,17,18]. The timing of these findings
`coincided with other observations that demonstrated the therapeutic potential of
`incretin hormones in relation to Type 2 diabetes [2]. Therefore, two strategies were
`conceived to harness the antidiabetic potential of incretin hormones. Initially came
`the development of analogues of GLP-1 and GIP resistant to DPP IV (see recent
`reviews [1,19]), and thereafter came the development of inhibitors of DPP IV. It is the
`
`10.1517/14728214.11.3.525 © 2006 Informa UK Ltd ISSN 1472-8214
`
`525
`
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`
`Inhibition of dipeptidyl peptidase IV activity as a therapy of Type 2 diabetes
`
`Table 1. Overview of functional characteristics of GLP-1 and GIP.
`
`GLP-1
`
`GIP
`
`√
`Released in response to a mixed meal
`√
`Lower blood glucose
`√
`Glucose-dependent stimulation of insulin secretion
`√
`Suppress glucagon secretion
`√
`Enhance β-cell survival
`√
`Stimulate β-cell expansion
`√
`Extrapancreatic glucose-lowering actions
`-
`Suppress gastric acid secretion
`√
`Inhibition of gastric emptying
`√
`Inhibition of hepatic insulin extraction
`√
`Enhance satiety
`√
`Reduce body weight
`√: Yes; -: Effect uncertain; GIP: Glucose-dependent insulinotropic polypeptide; GLP-1: Glucagon-like peptide-1.
`
`√
`√
`√
`-
`√
`√
`√
`√
`-
`√
`-
`-
`
`aim of this review to summarise the most recent and impor-
`tant advances in the development of DPP IV inhibitors as a
`new drug class for the treatment of Type 2 diabetes [20,21]. In
`particular, how the recent discovery of several DPP IV-related
`proline specific peptidases has prompted a re-evaluation of
`DPP IV inhibitors and their degree of selectivity is discussed.
`
`2. Background
`
`2.1 Type 2 diabetes
`Type 2 diabetes represents ∼ 90% of all cases of diabetes and is
`characterised by two main defects: i) impairment of pancre-
`atic β-cell function, and ii) impairment of insulin sensitivity
`of muscle, adipose tissue and liver. Ideally, future treatment
`strategies should seek to address both of these defects, as well
`as the resultant hyperglycaemia [22,23]. Type 2 diabetes is a
`major debilitating illness throughout the world and resulting
`complications place a growing burden on healthcare budgets.
`
`2.2 DPP IV and related enzymes
`Despite the vast array of different proteases found physio-
`logically, few can cleave the peptide bond following a proline
`amino acid residue. Fewer still can cleave this bond when it is
`located just two positions from the N-terminus. Serine pro-
`teases that carry out this specific cleavage function are termed
`the ‘postproline dipeptidyl aminopeptidases’. Many of these
`proteases belong to the DPP IV gene family. The family of
`enzymes related to DPP IV comprise: i) DPP IV, ii) fibro-
`blast activation protein (FAP), iii) DPP 8, iv) DPP 9 and
`v) DPP II, also known as DPP 7 or quiescent cell proline
`dipeptidase (QPP) [24]. DPP IV is usually identified by its
`postproline aminopeptidase activity, that is, its ability to pre-
`ferentially cleave Xaa-Pro or Xaa-Ala dipeptides from the
`N-terminus of polypeptides (where Xaa is any amino acid
`except Pro).
`
`2.2.1 DPP IV (EC 3.4.14.5)
`DPP IV doubles as the cell-surface CD26 T-cell-activating
`antigen and is expressed in almost all organs and tissues [25]. In
`humans it is strongly expressed in the exocrine pancreas, kid-
`ney, gastrointestinal tract, biliary tract, thymus, lymph nodes,
`uterus, placenta, prostate, adrenal, sweat glands, salivary and
`mammary glands. It is also found on endothelia of all organs
`examined, including spleen, lungs, brain and vessels supplying
`the liver [26]. In addition to being a cell-surface ectoenzyme
`anchored to the plasma membrane, DPP IV is found solubi-
`lised in body fluids such as blood plasma and cerebrospinal
`fluid. The distribution of DPP IV activity gives it ready access
`to endocrine peptides, neuropeptides and a wide range of
`paracrine and autocrine peptides and polypeptides.
`
`2.2.2 FAP
`FAP is a type II membrane-bound serine protease with 52%
`similarity to DPP IV. There has been speculation that FAP
`could be involved in wound healing as well as tumour growth
`and proliferation. It has also been linked with liver injury and
`chronic liver disease [27,28]. FAP is capable of dipeptidyl pepti-
`dase activity to cleave N-terminal dipeptides from polypep-
`tides, and collagenolytic activity that can degrade gelatin and
`type I collagen [29]. A common active site in FAP is used for
`both functions [29]. Immunopurified recombinant FAP pos-
`sesses DPP IV-like activity, as demonstrated by its ability to
`cleave an Ala-Pro-NH F3 Mec substrate [27]. FAP does not
`appear to be as ubiquitously expressed as other members of
`the DPP IV enzyme family, but has been found in serum and
`the α-cells of the pancreas [28].
`
`2.2.3 DPP 8 and 9
`DPP 8 and 9 are soluble postproline cleaving dipeptidases
`localised in the cytoplasm. Although DPP 8 and 9 share
`∼ 50% amino acid similarity to human DPP IV, they appear
`
`526
`
`Expert Opin. Emerging Drugs (2006) 11(3)
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`Boehringer Ex. 2007
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`

`
`Green, Flatt & Bailey
`
`GIP
`
`Y1 A2 E3
`
`42
`GTFISDYSIAMDKIHQQDFVNWLLAQKGKKNDWKHNITQ
`
`GLP-1
`
`H7 A8 E9
`
`36
`GTFTSDVSSYLEGQAAKEFIAWLVKGR
`
`Site of DPP IV degradation
`leading to a loss in insulin-releasing activity
`
`Figure 1. Degradation of incretin hormones by DPP IV. Incretins GLP-1 and GIP possess a highly conserved alanine amino acid
`residue penultimate to the N-terminus, making them ideal putative substrates for DPP IV. His7-Ala8 and Tyr1-Ala2 dipeptides are removed
`from GLP-1 and GIP, respectively, leading to noninsulinotropic metabolites GLP-1(9-36)amide and GIP(3-42).
`DPP IV: Dipeptidyl peptidase IV; GIP: Glucose-dependent insulinotropic polypeptide; GLP-1: Glucagon-like peptide-1.
`
`Meal
`ingestion
`
`L-cells
`
`Gut
`
`K-cells
`
`DPP IV
`inhibitors
`
`DPP IV
`
`GLP-1
`
`+
`
`Pancreas
`
`+
`
`GIP
`
`Insulin
`
`Glucose
`lowering
`
`Figure 2. DPP IV inhibitor mode of action. The incretin
`hormones GLP-1 and GIP, released from the L- and K-cells of the
`intestine, stimulate insulin release from the pancreas, leading to
`lower plasma glucose concentrations. However, enzymatic
`cleavage by ubiquitous DPP IV renders them noninsulinotropic.
`DPP IV inhibitors prevent processing by DPP IV and, therefore,
`improve incretin-stimulated insulin release and glucose lowering.
`DPP IV: Dipeptidyl peptidase IV;
`GIP: Glucose-dependent insulinotropic polypeptide;
`GLP-1: Glucagon-like peptide-1.
`
`to be more closely related to each other (∼ 76% similarity) [30].
`They are widely distributed in human tissues, but have not yet
`been associated with any particular biological process. DPP 8
`and 9 are active as monomers and hydrolyse H-Ala-Pro- and
`H-Gly-Pro-derived substrates [28]. It remains a distinct possi-
`bility that many of the functions ascribed to DPP IV may
`actually be derived from the activity of DPP 8 and/or 9. The
`
`recent discovery of DPP 8 and 9 has had major implications
`for the specificity of DPP IV inhibitors, to avoid inhibition of
`DPP 8 and 9.
`
`2.2.4 DPP II (DPP 7 or QPP) (E.C. 3.4.14.2)
`DPP II was originally referred to as dipeptidyl aminopepti-
`dase II [31] and its activity was detected by the hydrolysis of
`Lys-Ala-derived chromogenic or fluorogenic substrates at
`acidic pH. DPP II activity has been detected in a range of
`mammalian tissues [32]. Recent evidence has strongly indi-
`cated that DPP II, DPP 7 and QPP are not different enzymes,
`but in fact the same enzyme with three different names in the
`literature [32,33]. Although only a few compounds have been
`discovered with an inhibitory effect on DPP II activity, they
`were all originally described as DPP IV inhibitors. Com-
`pounds such as Val-boro-Pro and Ala-Pyrr-2-CN, as well as
`aminoacyl pyrrolidines and thiazolidine derivatives actually
`have a higher potency towards DPP IV [34-36]. There are two
`compounds, Ala-ψ[CS-N]-Pyrr and Ala-ψ[CS-N]-Thia, with
`more selectivity towards DPP II than DPP IV [37].
`
`2.3 Natural substrates of DPP IV enzyme activity
`Table 2 lists examples of the extensive range of physiological
`regulatory peptides identified as substrates or potential sub-
`strates of DPP IV. All of these peptides have either Ala, Pro
`or Ser penultimate to the N-terminus. It is evident that
`DPP IV acts on several chemokines that affect the immune
`system. Chemokine substrates of DPP IV include RANTES,
`interferon-γ-inducible protein-10, monocyte
`eotaxin,
`chemotactic protein
`(MCP)-1,
`-2 and
`-3,
`stromal
`cell-derived factor-1α and -β, granulocyte chemotactic pro-
`tein-2 and macrophage-derived chemokine (see Table 2) [25].
`By altering chemokine activity, DPP IV can modify specifi-
`city for, and ability to activate, immune receptors. For exam-
`ple, the peptide RANTES(1-68), which is chemotactic for
`lymphocytes, monocytes, dendritic cells, eosinophils,
`basophils and NK cells, is truncated to RANTES(3-68) by
`DPP IV. RANTES(3-68) is unable to increase cytosolic cal-
`cium levels and induce chemotaxis in human monocytes [38].
`Furthermore, RANTES(3-68) antagonises the chemotactic
`effects of RANTES(1-68) and other chemotactic proteins
`
`Expert Opin. Emerging Drugs (2006) 11(3)
`
`527
`
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`C o p yrig ht of Infor m a U K Ltd.
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`Boehringer Ex. 2007
`Mylan v. Boehringer Ingelheim
`IPR2016-01566
`Page 4
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`

`
`Inhibition of dipeptidyl peptidase IV activity as a therapy of Type 2 diabetes
`
`Table 2. Physiological regulatory peptides identified as substrates of DPP IV
`
`Peptide
`
`GLP-1 (7-36)amide
`GLP-1 (7-37)
`GLP-2 (1-33)
`GIP (1-42)
`GHRH
`GHRH (1-29)
`GHRH (1-44)
`Peptide histidine methionine
`PACAP (1-27)
`PACAP (1-38)
`Gastrin-releasing peptide
`Substance P
`Insulin-like growth factor-1
`Bradykinin
`Neuropeptide Y
`Peptide YY (1-36)
`Prolactin
`Human chorionic gonadotropin-α
`Luteinising hormone α-chain
`Thyrotropin-α
`Enkephalins
`Vasostatin-1
`Trypsinogen
`Trypsinogen propeptide
`Procolipase
`IL-2
`IL-1β
`α1-Microglobulin
`Tyr-melanostatin
`Endomorphin-2
`Enterostatin
`β-Casomorphin
`Corticotropin-like intermediate lobe peptide
`Aprotinin
`RANTES
`Granulocyte chemotactic protein-2
`SDF-1α
`SDF-1β
`Macrophage-derived chemokine
`MCP-1
`MCP-2
`
`N-terminus
`
`His-Ala-Glu-
`His-Ala-Glu-
`His-Ala-Asp-
`Tyr-Ala-Asp-
`Tyr-Ala-Glu-
`Tyr-Ala-Asp-
`Tyr-Ala-Asp-
`His-Ala-Asp-
`His-Ser-Asp-
`His-Ser-Asp-
`Val-Pro-Leu-
`Arg-Pro-Lys-
`Gly-Pro-Glu-
`Arg-Pro-Pro-
`Tyr-Pro-Ser-
`Tyr-Pro-Ile-
`Thr-Pro-Val-
`Ala-Pro-Asp-
`Phe-Pro-Asn-
`Phe-Pro-Asp-
`Tyr-Pro-Val-
`Leu-Pro-Val-
`Phe-Pro-Thr-
`Phe-Pro-Thr-
`Val-Pro-Asp-
`Ala-Pro-Thr-
`Ala-Pro-Val-
`Gly-Pro-Val-
`Tyr-Pro-Leu-
`Tyr-Pro-Phe-
`Val-Pro-Asp-
`Tyr-Pro-Phe-
`Arg-Pro-Val-
`Arg-Pro-Asp-
`Ser-Pro-Tyr-
`Gly-Pro-Val-
`Lys-Pro-Val-
`Lys-Pro-Val-
`Gly-Pro-Tyr-
`Glu-Pro-Asp-
`Glu-Pro-Asp-
`
`Reference
`
`[101]
`
`[101]
`
`[102]
`
`[101]
`
`[101]
`
`[103]
`
`[101]
`
`[101]
`
`[44-46]
`
`[44-46]
`
`[104]
`
`[104]
`
`[25]
`
`[105]
`
`[106]
`
`[106]
`
`[104]
`
`[104]
`
`[25]
`
`[25]
`
`[107]
`
`[108]
`
`[104]
`
`[104]
`
`[104]
`
`[104]
`
`[109]
`
`[104]
`
`[104]
`
`[110]
`
`[111]
`
`[104]
`
`[104]
`
`[104]
`
`[112]
`
`[38]
`
`[113]
`
`[113]
`
`[114]
`
`[38]
`
`[112]
`
`DPP IV: Dipeptidyl peptidase IV; GHRH: Growth hormone-releasing hormone; GIP: Glucose-dependent insulinotropic polypeptide; GLP-1: Glucagon-like peptide-1;
`MCP: Monocyte chemotactic protein; PACAP: Pituitary adenylyl cyclase-activating peptide; SDF: Stromal cell-derived factor.
`
`528
`
`Expert Opin. Emerging Drugs (2006) 11(3)
`
` Printin g an d distrib utio n strictly pro hibited
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`Boehringer Ex. 2007
`Mylan v. Boehringer Ingelheim
`IPR2016-01566
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`

`
`Table 2. Physiological regulatory peptides identified as substrates of DPP IV (continued)
`
`Peptide
`
`N-terminus
`
`Reference
`
`Green, Flatt & Bailey
`
`[38]
`
`Glu-Pro-Val-
`Gly-Pro-Ala-
`Val-Pro-Leu-
`
`MCP-3
`Eotaxin
`IFN-γ-inducible protein-10
`DPP IV: Dipeptidyl peptidase IV; GHRH: Growth hormone-releasing hormone; GIP: Glucose-dependent insulinotropic polypeptide; GLP-1: Glucagon-like peptide-1;
`MCP: Monocyte chemotactic protein; PACAP: Pituitary adenylyl cyclase-activating peptide; SDF: Stromal cell-derived factor.
`
`[112]
`
`[112]
`
`such as macrophage inflammatory protein-1α and -1β and
`MCP-3 [39].
`Neuropeptide substrates of DPP IV include substance P,
`bradykinin, peptide YY (PYY), neuropeptide Y (NPY), endo-
`morphin and pituitary adenylyl cyclase activating peptide
`(PACAP). With their conserved Tyr-Pro N-terminus, PYY
`and NPY appear to be convenient substrates for DPP IV [25].
`NPY normally stimulates food intake and promotes weight
`gain [40] and this effect could be reduced by DPP IV. The spe-
`cificity of PYY(1-36) for receptor subtypes is significantly
`altered following cleavage to PYY(3-36). Whereas PYY(1-36)
`binds to and activates at least three Y receptor subtypes (Y1,
`-2 and -5), PYY(3-36) is selective for the Y2 receptor.
`PYY(3-36) has a satiety effect, acting via the Y2 receptor in
`the arcuate nucleus to reduce food intake [41]. It remains to be
`seen whether inhibition of DPP IV activity could change the
`balance of PYY(1-36) and PYY(3-36), and potentially
`increase food intake or interfere with effects of NPY and
`GLP-1 on food intake. PACAP is another neuropeptide sub-
`strate of DPP IV. PACAP is a member of the glucagon super-
`family of peptides and, therefore, is closely related to the
`incretin hormones. PACAP is localised in pancreatic islet
`nerves and islet β-cells [42,43], and like the incretins, PACAP is
`an insulinotropic peptide. PACAP is found in active 1-27 and
`1-38 amino acid
`isoforms, which are degraded
`to
`[44-46].
`PACAP(3-27)
`and PACAP(3-38),
`respectively
`PACAP(3-27) and PACAP(3-38) fragments are noninsulino-
`tropic [44]. It appears that PACAP(3-27) undergoes further
`degradation to PACAP(5-27) and PACAP(6-27), neither of
`which are insulinotropic. Interestingly, PACAP(6-27) appears
`to antagonise the actions of PACAP(1-27). Similarly, DPP IV
`truncates glucagon to generate glucagon(3-29) and gluca-
`gon(5-29). This substantially reduces affinity for the glucagon
`receptor and removes biological activity [47].
`
`2.4 The incretin hormones as substrates of DPP IV
`The two major incretin hormones, GLP-1 and GIP, are
`degraded by DPP IV [1,2,48]. These peptide hormones are 30
`and 42 amino acids in length, respectively, and the action of
`DPP IV removes an N-terminal dipeptide from each. Physiolog-
`ically, DPP IV degrades GLP-1(7-36)amide and GLP-1(7-37)
`into major truncated metabolites GLP-1(9-36)amide and
`GLP-1(9-37) (Figure 1). Similarly, GIP(1-42) is truncated to
`GIP(3-42) (Figure 1). These truncated peptides are rendered
`noninsulinotropic. However, recent evidence suggests that
`
`truncated GLP-1(9-36)amide may retain other biological func-
`tions, particularly in relation to glucose disposal [49]. In healthy
`male volunteers, GLP-1(9-36)amide lowers postprandial glycae-
`mia independent of any effects on insulin secretion, glucagon
`secretion or the rate of gastric emptying [50]. Therefore, the
`action of DPP IV on incretin hormones may be confined to an
`effect on insulin secretion and not on other glucoregulatory
`effects of these hormones.
`
`3. Medical need
`
`Type 2 diabetes represents a large and growing unmet
`medical need. In developed countries the prevalence of
`Type 2 diabetes is rising rapidly, and at least a third of cases
`are undiagnosed. The resulting comorbidities (e.g., retino-
`pathy, neuropathy, nephropathy) associated with Type 2
`diabetes are placing larger burdens on health services and
`budgets. Several of the current drug therapies have been
`associated with secondary failure as well as undesirable side
`effects, such as hypoglycaemia.
`
`4. Existing treatment
`
`Although dietary control is always the primary approach to
`Type 2 diabetes, and tackling obesity will enhance insulin sensi-
`tivity and glucose control [22,23], moderate or severe hyper-
`glycaemia invariably requires drug intervention [22,23]. Current
`therapies improve metabolic abnormalities by either enhancing
`insulin secretion (sulfonylureas, meglitinides) or reducing insu-
`lin resistance (biguanides, thiazolidinediones). All of the availa-
`ble agents are limited in efficacy by the progressive deterioration
`of β-cell function that occurs throughout the natural history of
`Type 2 diabetes. Improvements in our understanding of the
`pancreatic β-cell function are necessary to address current
`unmet medical needs and achieve better glycaemic control in
`more patients. Compounds based on the physiological incretin
`hormones, GLP-1 and GIP, may meet such needs. The first
`GLP-1 analogue, exenatide, was launched in the US in 2005
`and other stable analogues are expected soon. There are indica-
`tions that incretin hormones may prevent or even reverse the
`gradual β-cell decline, thus making them a particularly advanta-
`geous addition to current treatments. DPP IV inhibitors seek to
`improve the action of endogenous incretin hormones, thereby
`representing a potential new addition to the growing armoury
`of antidiabetic drugs.
`
`Expert Opin. Emerging Drugs (2006) 11(3)
`
`529
`
` Printin g an d distrib utio n strictly pro hibited
`
`C o p yrig ht of Infor m a U K Ltd.
`
`Boehringer Ex. 2007
`Mylan v. Boehringer Ingelheim
`IPR2016-01566
`Page 6
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`

`
`Inhibition of dipeptidyl peptidase IV activity as a therapy of Type 2 diabetes
`
`Table 3. DPP IV inhibitor compounds in development or recently discontinued.
`
`Inhibitor
`
`Type of action
`
`Company
`
`Status
`
`Phase
`
`NDA submitted to
`FDA 2006
`NDA submitted to
`FDA 2006
`Discontinued
`
`P32/98
`(isoleucine thiazolidide)
`Sitagliptin (MK-0431)
`
`Vildagliptin
`(LAF-237)
`NVP-DPP728
`
`Aminomethylpyridine
`(R-1438)
`Saxagliptin
`(BMS-477118)
`PSN-9301
`
`NN-7201
`
`Ddenagliptin
`(GSK-823093C)
`SYR-322
`
`Reversible product
`analogue
`Reversible product
`analogue
`Reversible product
`analogue
`Covalently bound
`product analogue
`Reversible nonpeptide
`heterocyclic inhibitor
`Covalently bound
`product analogue
`Reversible product
`analogue
`Reversible nonpeptide
`heterocyclic inhibitor
`-
`
`Probiodrug
`
`Merck
`
`Novartis
`
`Novartis
`
`Roche
`
`Bristol-Myers Squibb
`
`Prosidion
`
`NovoNordisk
`
`GlaxoSmithKline
`
`-
`
`Takeda
`
`II
`
`III
`
`III
`
`II
`
`II
`
`III
`
`II
`
`-
`
`II
`
`III
`
`Specificity/
`inhibitory
`coefficient
`
`Ki = 80 nM
`
`IC50 = 18 nM
`
`IC50 = 3.5 nM
`
`IC50 = 22 nM
`
`Ki = 0.1 nM
`
`Ki = 0.45 nM
`
`Not available
`
`Not available
`
`Not available
`
`Not available
`
`Information mostly obtained from Pharmaprojects, V5.1 [201] and a recent review by McIntosh et al. [57].
`-: Not known; DPP IV: Dipeptidyl peptidase IV; NDA: New drug application.
`
`5. Drug development
`
`The concept of DPP IV inhibitors was devised as a method of
`preventing DPP IV-mediated degradation of GLP-1 and GIP
`to extend their insulin-releasing activity. However, when
`GLP-1 and GIP were infused into rats at physiological con-
`centrations, > 50% was truncated within 2 min [13]. Crucially,
`these truncated metabolites appeared to be absent after infu-
`sions into DPP IV-deficient animals [13]. Therefore, it was
`concluded that DPP IV was the primary inactivating enzyme
`of GIP and GLP-1 in vivo, and DPP IV inhibition was pro-
`posed as a potential strategy to prevent physiological inactiva-
`tion of these incretins. Similarly, mice and rats deficient in
`DPP IV activity have an increased proportion of intact GLP-1
`and GIP compared with truncated forms [52,54]. Studies in iso-
`lated perfused porcine ileum revealed that ∼ 50% of released
`GLP-1 was rapidly truncated and that the application of a
`DPP IV inhibitor substantially increased intact levels of
`GLP-1 possibly to > 80% [55].
`A wide range of DPP IV inhibitors have been developed
`and the structures and characteristics of several of these have
`recently been reviewed [56-59]. Table 3 lists various DPP IV
`inhibitors in development and their specificity (Ki) or inhibi-
`tory coefficient (IC50). Many DPP IV inhibitors are classed
`as either reversible product analogues, covalently bound
`product analogues or reversible nonpeptide heterocyclic
`inhibitors (see Table 3). Novartis and Merck have tablet
`
`formulations of DPP IV inhibitors in advanced Phase III
`clinical trials.
`
`6. Current research goals
`
`The current research goals in this field are:
`
`(cid:127) to review the specificity, selectivity, safety and efficacy of
`DPP IV inhibitors now in development
`(cid:127) to ascertain whether DPP IV inhibitors derive their anti-
`diabetic effect via mechanisms other than prevention of
`incretin hormone degradation
`(cid:127) to further investigate the effects of DPP IV inhibition on
`other systems and side effects resulting from cleavage of
`alternate substrates
`(cid:127) to ascertain whether a DPP IV inhibition strategy could be
`enhanced by the use of other inhibitors such as neutral
`endopeptidase 24.11 (NEP-24.11) inhibitors
`(cid:127) to evaluate effects of DPP IV inhibition on other systems,
`and potential resulting side effects
`
`7. Scientific rationale
`
`7.1 DPP IV in the pathophysiology of obesity
`and diabetes
`There have been significant recent advances in our knowledge
`of the involvement of DPP IV in obesity and diabetes. Of
`
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`
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`Mylan v. Boehringer Ingelheim
`IPR2016-01566
`Page 7
`
`

`
`particular importance has been the application of gene
`‘knockout’ to generate mice lacking DPP IV activity [51].
`These mice are viable, healthy and their plasma possesses
`some residual cleavage of the substrate Gly-Pro-pNA. How-
`ever, no significant N-terminal degradation of the incretin
`hormone GLP-1 was observed [51]. DPP IV-deficient mice
`have enhanced glucose tolerance and increased levels of
`plasma insulin, and it has been suggested that this results from
`higher levels of active GLP-1, and perhaps also active GIP. On
`a high-fat diet, mice lacking DPP IV gained less weight due to
`decreased food intake and increased energy expenditure [52].
`DPP IV-deficient mice have improved insulin sensitivity and
`appear to resist hepatic lipid accumulation when fed a
`high-fat diet [52]. Findings in these DPP IV-knockout mice are
`in broad agreement with those of a rat strain harbouring
`mutant DPP IV, and strengthen the rationale for use of spe-
`cific DPP IV inhibitors in Type 2 diabetes [53,54]. However,
`this evidence must be balanced against reports that receptor
`knockout mice GIPR-/- and GLP-1R-/- resist weight gain and
`show improved insulin sensitivity, thus indicating that loss of
`incretin action can have some similar long-term effects to loss
`of DPP IV activity [60]. The extent to which DPP IV inhibi-
`tion could affect feeding behaviour and metabolite control
`through changes in the concentrations of other peptides (e.g.,
`NPY, PYY or growth hormone-releasing hormone) remains to
`be established.
`
`7.2 The effects of DPP IV inhibitors in animal models
`of diabetes
`Several DPP IV inhibitors have been examined in diabetic
`rodents revealing glucose-lowering effects. In Zucker fatty rats,
`P32/98 (isoleucine thiazolidide) substantially decreased circu-
`lating DPP IV activity and improved glucose tolerance [59]. In
`addition, in Zucker rats, the inhibitor NVP-DPP728 ampli-
`fied the early phase insulin response and restored glucose
`[61]. The effects of P32/98 and
`excursions to normal
`NVP-DPP728 contributed to increased levels of active
`GLP-1(7-36)amide. When the DPP IV inhibitor valine-pyrro-
`lidide was coadministered with intravenous GIP the insulino-
`tropic effect of GIP was improved, glucose clearance was
`enhanced and glucose excursions were reduced [62]. Another
`study examined the effects of vildagliptin (LAF-237) on
`plasma DPP IV activity, intact GLP-1, glucose and insulin
`after an oral glucose load over a 21-day period in insulin-resist-
`ant Zucker fatty rats [63]. Vildagliptin augmented glucose-stim-
`ulated circulating levels of intact, biologically active GLP-1
`and exerted dose-dependent effects on DPP IV, glucose toler-
`ance and β-cell function [63]. Vildagliptin had no effect on
`body weight in these studies.
`Long-term, twice-daily P32/98 administration of Zucker
`rats for 3 months decreased body weight gain, but did not alter
`food intake [64]. Chronic P32/98 treatment improved glucose
`tolerance and increased insulin levels, but no significant differ-
`ences in β-cell area or islet morphology were detected
`following the 12-week treatment period [64]. Strangely, fasting
`
`Green, Flatt & Bailey
`
`DPP IV activity progressively increased over the treatment
`period and it was suggested that this might be a compensatory
`response to chronic DPP IV inhibition [64]. In streptozo-
`tocin-induced diabetic rats, long-term treatment with P32/98
`led to increased weight gain, nutrient intake and insulin secre-
`tion and markedly improved glucose tolerance [65]. Further-
`more, immunohistochemical studies suggested that P32/98
`treatment enhanced islet neogenesis, β-cell survival and insulin
`biosynthesis, tentatively attributed in increased intact GLP-1
`[65]. Mice fed on a high-fat diet, receiving
`and GIP
`NVP-DPP728 for 8 weeks, showed increased levels of intact
`GLP-1,
`improved
`glucose
`tolerance
`and
`increased
`glucose-stimulated insulin secretion, but there was reduced
`islet hyperplasia although expression of the glucose transporter,
`GLUT-2, was enhanced [66].
`It appears that DPP IV inhibition as a strategy for improv-
`ing glycaemic status is more effective in mild and moderate
`hyperglycaemic Type 2 diabetes than in severe diabetes. An
`investigation into the effects of DPP IV inhibition in the early
`and late stages of diabetes in db/db mice found that
`valine-pyrrolidide improved glucose tolerance at 6 weeks of
`age, but did not at 23 weeks of age [67]. These data suggest
`that DPP IV inhibitors may be useful as an early intervention
`strategy to address impaired glucose tolerance and the early
`stages of Type 2 diabetes [67].
`Recent evidence suggests that DPP IV inhibition prevents
`degradation of the intestinotropic hormone, GLP-2, leading
`to enhanced small bowel weight [68]. Because GLP-2 is con-
`sidered a potential treatment for colitis and short bowel syn-
`drome, it has been suggested that DPP IV inhibitors could
`assist in the treatment of these gastrointestinal diseases [69,70].
`
`8. Competitive environment
`
`8.1 DPP IV inhibitors in Type 2 diabetes
`So far, few clinical studies with DPP IV inhibitors in Type 2
`diabetic patients have been reported (Table 4). A preliminary
`account of acute administration of P32/98 (60 mg) in non-
`diabetic and Type 2 diabetic subjects receiving other anti-
`diabetic therapies noted improved oral glucose tolerance
`associated with increased concentrations of intact GLP-1 [71].
`A study giving NVP-DPP728 (100 mg t.i.d. and 150 mg
`b.i.d.) for 12 weeks to diet-treated Type 2 diabetic patients
`reduced
`fasting
`(by 1 mmol/l) and postprandial
`(by
`1.2 mmol/l) blood glucose. Insulin concentrations were mar-
`ginally reduced, possibly reflecting the reduced glycaemia, and
`body weight was unchanged [72]. NVP-DPP728 was a
`short-acting
`inhibitor, and has been discontinued and
`superseded by the longer-acting vildagliptin.
`Administration of vildagliptin (100 mg/day) for 4 weeks to
`diet-treated Type 2 diabetic patients reduced fasting and post-
`prandial plasma glucose (by 0.7 and 1.4 mmol/l, respectively)
`without a measurable change of insulin. Active GLP-1
`(GLP-1[7-36]amide) concentrations were approximately
`doubled (postprandial concentrations rose to ∼ 8 pmol/l
`
`Expert Opin. Emerging Drugs (2006) 11(3)
`
`531
`
` Printin g an d distrib utio n strictly pro hibited
`
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`
`Boehringer Ex. 2007
`Mylan v. Boehringer Ingelheim
`IPR2016-01566
`Page 8
`
`

`
`Inhibition of dipeptidyl peptidase IV activity as a therapy of Type 2 diabetes
`
`RDBPC: Randomised double-blind placebo controlled; t.i.d.: Three times daily.
`b.i.d.: Twice daily; FBG: Fasting blood glucose; FPG: Fasting plasma glucose; PBG: Postprandial blood glucose; PC: Placebo controlled; PPG: Postprandial plasma glucose; RDBC: Randomised double-blind comparator;
`*For first 12weeks; ‡For the 100mg/day dose; ↓: Decrease.
`
`(1.1mmol/l)
`↓ FPG 2.0mg/ml
`↓ HbA1c 0.7%‡
`(0.95mmol/l)‡
`↓ FPG 1.7mg/ml
`
`↓ HbA1c 0.65%
`
`↓ HbA1c 0.79%
`
`↓ HbA1c 1.0%
`↓ FPG 1.2mmol/l
`↓ HbA1c 0.53%‡
`↓ PPG 0.89mmol/l‡
`↓ FPG 0.54mmol/l‡
`↓ HbA1c 1.1%
`↓ PPG 2.4mmol/l
`↓ FPG 1.1mmol/l
`↓ PPG 1.4mmol/l
`↓ FPG 0.7mmol/l
`↓ PBG 1.2mmol/l
`↓ FBG 1mmol/l
`
`RDBPC
`
`RDBPC
`
`RDBPC
`
`RDBPC
`
`RDBC
`RDBPC
`
`PC
`
`RDBPC*
`
`RDBPC
`
`RDBPC
`
`control
`Effect on glycaemic
`
`Study design
`
`28
`
`552
`
`701
`
`741
`
`526
`20
`
`279
`
`107
`
`37
`
`93
`
`n
`
`4
`
`12
`
`24
`
`24
`
`52
`
`4
`
`12
`
`52
`
`4
`
`4
`
`Sitagliptin 100mg/dayMetformin
`
`Diet only
`
`25 – 100mg/day
`Sitagliptin
`
`Sitagliptin 100mg/dayMetformin
`
`Diet only
`
`Sitagliptin 100mg/day
`
`Vildagliptin 100mg/dayDiet only
`Vild