Development of dipeptidyl peptidase-4 inhibitors
Encyclopedia
Dipeptidyl peptidase-4 inhibitors
(DPP-4 inhibitors) are enzyme inhibitors that inhibit the enzyme
dipeptidyl peptidase-4
(DPP-4) and are a potent
treatment for type 2 diabetes. Inhibition of the DPP-4
enzyme prolongs and enhances the activity of incretins that play an important role in insulin
secretion and blood glucose control regulation.
Type 2 diabetes is a chronic metabolic disease that can be caused by pancreas β-cell dysfunction, deficiency in insulin
secretion, insulin
resistance and/or increased hepatic glucose production. It is one of the fastest growing health concerns in the world
. Current treatment
s are often inefficient at sustaining glycemic control and may cause undesirable side effect
s, such as weight gain
and episodes of hypoglycemia
. Therefore, new and more effective drugs have been developed with DPP-4 inhibitors playing a significant role.
. The first inhibitors were characterized in the late 1980s
and 1990s
. Each inhibitor
was important to establish an early structure activity relationship (SAR) for subsequent investigation. It should be noted that the inhibitors fall into two main classes, those that interact covalent with DPP-4 and those that do not. DPP-4
is a dipeptidase
that selectively binds substrate
s that contain proline
at the P1-position, thus many DPP-4 inhibitors have 5-membered heterocyclic rings that mimic
proline
, e.g. pyrrolidine
, cyanopyrrolidine, thiazolidine
and cyanothiazolidine. These compounds commonly form covalent bonds to the catalytic residue Ser630.
In 1994, researchers from Zeria Pharmaceuticals unveiled cyanopyrrolidines with a nitrile
function group that was assumed to form an imidate with the catalytic serine
. Concurrently other DPP-4 inhibitors without a nitrile
group were published but they contained other serine-interacting motifs, e.g. boronic acids, phosphonate
s or diacyl hydroxylamine
s. These compound
s were not as potent because of the similarity of DPP-4
and prolyl oligopeptidase (PEP) and also suffered from chemical instability
. Ferring Pharmaceuticals
filed for patent on two cyanopyrrolidine DPP-4 inhibitors, which they published in 1995. These compounds had excellent potency
and improved chemical stability.
In 1995, Edwin B. Villhauer at Novartis
started to explore N-substituted glycinyl-cyanopyrrolidines based on the fact that DPP-4 identifies N-methylglycine as a N-terminal amino acid
. This group of new cyanopyrrolidines became extremely popular field of research in the following years. Some trials with dual inhibitors of DPP-4 and vasopeptidase have been represented, since vasopeptidase inhibition is believed to enhance the antidiabetic effect of DPP-4 inhibition
by stimulating insulin
secretion. Vasopeptidase-inhibiting motif is connected to the DPP-4 inhibitor at the N-substituent.
During a meal
the incretin
s glucagon-like peptide 1 (GLP-1) and glucose-dependent gastric inhibitory polypeptide (GIP) are released from the small intestine
into the vasculature. The hormone
s regulate insulin secretion in a glucose-dependent manner. GLP-1 has many roles in the human body
; it stimulates insulin biosynthesis, inhibits glucagon secretion, slows gastric emptying, reduces appetite and stimulates regeneration of islet β-cells.
GIP and GLP-1 have extremely short plasma half-lives due to a very rapid inactivation. The enzyme
responsible for the metabolism
is DPP-4. Inhibition of DPP-4 leads to potentiation of endogenous GIP and GLP-1 and hence improves treatment of type 2 diabetes (Figure 1).
DPP-4 selectively cleaves two amino acid
s from peptide
s, such as GLP-1 and GIP, which have proline
or alanine
in the second position (Figure 2). At the active site
of the protease
there is a characteristic motif of three amino acid
s, Asp-His-Ser. DPP-4 is the CD26 T-cell-activating antigen
, which is widely distributed in human organs
and tissue. Tissue
s, which strongly express DPP-4, include the exocrine pancreas
, sweat glands, salivary
and mammary glands, thymus
, lymph nodes, biliary tract, kidney
, liver
, placenta
, uterus
, prostate
, skin
and the capillary bed of the gut
mucosa where most GLP-1 is inactivated locally. DPP-4 is attached to the plasma membrane of the endothelia of almost all organs in the body
. It is also present in body fluids, such as blood plasma
and cerebrospinal fluid
, in a soluble form. DPP-4 inactivates GLP-1 and GIP very rapidly. Regarding GIP and GLP-1, alanine
and proline
are crucial for biological activity
, so elimination of these amino acid
s leads to formation of metabolite
s that are inactive. Thus, preventing the degradation of the incretin
hormone
s GIP and GLP-1 by inhibition of DPP-4 is an exciting therapeutic strategy.
, it is not unexpected that inhibitors would likely have a peptide
nature and this theme has carried through to contemporary research.
structures of DPP-4
that have been published since 2003 give rather detailed information about the structural characteristics of the binding site
. Many structurally diverse DPP-4 inhibitors have been discovered and it is not that surprising considering the properties of the binding site:
1. A deep lipophilic
pocket combined with several exposed aromatic side chain
s for achieving high affinity small molecule binding.
2. A significant solvent
access that makes it possible to tune the physico-chemical properties of the inhibitors that leads to better pharmacokinetic behavior.
DPP-4 is a 766-amino acid transmembrane glycoprotein
that belongs to the prolyloligopeptidase family. It consists of three parts; a cytoplasmic tail, a transmembrane region and an extracellular
part. The extracellular
part is divided into a catalytic domain and an eight-bladed β-propeller domain. The latter contributes to the inhibitor binding site. The catalytic domain shows an α/β-hydrolase fold and contains the catalytic triad Ser630 - Asp708 - His740. The S1-pocket is very hydrophobic and is composed of the side chains: Tyr631, Val656, Trp662, Tyr666 and Val711. Existing X-ray
structures show that there is not much difference in size and shape of the pocket that indicates that the S1-pocket has high specificity for proline
residues
DPP-4 inhibitors usually have an electrophilic group that can interact with the hydroxyl
of the catalytic serine in the active binding site (Figure 3). Frequently that group is a nitrile
group but can also be boronic acid
or diphenyl phosphonate
. This electrophilic group can bind to the imidate complex
with covalent bonds and slow, tight-binding kinetics but this group is also responsible for stability issues due to reaction
s with the free amino group of the P2-amino acid. Therefore inhibitors without the electrophilic group have also been developed, but these molecule
s have shown toxicity
due to affinity to other dipeptidyl peptidases, e.g. DPP-2, DPP-8
and DPP-9
.
DPP-4 inhibitors span diverse structural types. In 2007 few of the most potent
compounds contain a proline
mimetic
cyanopyrrolidine P1 group. This group enhances the potency, probably due to a transient covalent trapping of the nitrile
group by the active site Ser630 hydroxyl, leading to delayed dissociation and slow tight binding of certain inhibitors. When these potency enhancements were achieved, some chemical stability issues were noted and more advanced molecules had to be made. To avoid these stability issues, the possibility to exclude the nitrile
group was investigated. Amino acids with aryl
or polar
side chains did not show appreciable DPP-4 inhibition
and in fact, all compounds without the nitrile group in this research suffered a 20 to 50-fold loss of potency corresponding to the compounds containing the nitrile
group.
(VS) can give higher rates. VS
has for example been used to screen for small primary aliphatic amines to identify fragment
s that could be placed in S1 and S2 sites of DPP-4
. On the other hand, these fragments were not very potent and therefore identified as a starting point to design better ones.
Three-dimensional models
can provide a useful tool for designing novel DPP-4 inhibitors. Pharmacophore
models have been made based on key chemical features of compound
s with DPP-4 inhibitory activity. These models can provide a hypothetical picture of the primary chemical feature responsible for inhibitory activity.
The first DPP-4 inhibitors were reversible inhibitors and came with bad side effects
because of low selectivity. Researchers suspected that inhibitors with short half-lives would be preferred in order to minimize possible side effects
. However, since clinical trials showed the opposite, the latest DPP-4 inhibitors have a long-lasting effect. One of the first reported DPP-4 inhibitor was P32/98 from Merck
. It used thiazolidide as the P1-substitute and was the first DPP-4 inhibitor that showed effects in both animal
s and human
s but it was not developed to a market drug
due to side effects
. Another old inhibitor is DPP-728 from Novartis
, where 2-cyanopyrrolidine is used as the P1-substitute. The addition of the cyano group generally increases the potency. Therefore, researchers' attention was directed to those compounds. Usually, DPP-4 inhibitors are either substrate
-like or non-substrate-like.
mimetic
that occupies the S1-pocket. Large substituents on the 2-cyanopyrrolidine ring are normally not tolerated since the S1-pocket is quite small.
Since DPP-4
is identical with the T-cell activation marker CD26 and DPP-4 inhibitors are known to inhibit T-cell proliferation
, these compounds were initially thought to be potential immunomodulator
s. When the function against type 2 diabetes was discovered, the cyanopyrrolidines became a highly popular research material. A little later vildagliptin
and saxagliptin
, which are the most developed cyanopyrrolidine DPP-4 inhibitors to date, were discovered.
1. Nitrile
in the position of the scissile bond of the peptidic substrate that is important for high potency. The nitrile group forms reversible covalent bonds with the catalytically active serine
hydroxyl (Ser630), i.e. cyanopyrrolidines are competitive inhibitors with slow dissociation kinetics.
2. Hydrogen bond
ing network between the protonated amino group and a negatively charged
region of the protein
surface, Glu205, Glu206 and Tyr662. All cyanopyrrolidines have basic, primary or secondary amine
, which makes this network possible but these compounds usually drop in potency if these amines are changed. Nonetheless, two patent applications unveil that the amino group can be changed, i.e. replaced by a hydrazine
, but it is claimed that these compounds do not only act via DPP-4 inhibition but also prevent diabetic vascular complications by acting as a radical
scavenger.
Important structure-activity relationship
:
1. Strict steric constraint exists around the pyrrolidine
ring of cyanopyrrolidine-based inhibitors, with only hydrogen
, fluoro, acetylene
, nitrile
, or methano substitution permitted.
2. Presence of a nitrile
moiety on the pyrrolidine
ring is critical to achieving potent activity
Also, systematic SAR investigation has shown that the ring size and stereochemistry
for the P2 position is quite conditioned. A 5-membered ring and L-configuration has shown better results than a 4-membered or 6-membered ring with D-configuration. Only minor changes on the pyrrolidine
ring can be tolerated since the good fit of the ring with the hydrophobic S1 pocket is very important for high affinity. Some trials have been made, e.g. by replacing the pyrrolidine
with a thiazoline
. That led to improved potency but also loss of chemical stability. Efforts to improve chemical stability often led to loss of specificity because of interactions with DPP-8
and DPP-9
. These interactions have been connected with increased toxicity
and mortality
in animals. There are strict limitations in the P1 position and hardly any changes are tolerated, on the other hand a variety of changes can be made in the P2 position. In fact, substitution
with quite big branched side chains, e.g. tert-butylglycin, normally increased activity and chemical stability, which could lead to longer-lasting inhibition of the DPP-4 enzyme. It has also been noted that biaryl-based side-chains can also give highly active inhibitors. It was originally believed that only lipophilic
substitution would be tolerated. Now it is stated that also the substitution of polar
negatively charged side-chains as well as hydrophilic substitution can lead to excellent inhibitory activity.
In general, DPP-4 inhibitors are not very stable compounds. Therefore, many researchers focus on enhancing the stability for cyanopyrrolidines. The most widespread technique to improve chemical stability is to incorporate a steric bulk. The two cyanopyrrolidines that have been most pronounced, vildagliptin
and saxagliptin
, were created in this manner. K579 is a DPP-4 inhibitor discovered by researchers at Kyowa Hakko Kyogo. It had improved not only chemical stability but also a longer-lasting action. That long-lasting action was most likely due to slow dissociation of the enzyme-inhibitor complex and an active oxide
metabolite
that undergoes enterohepatic circulation. The discovery of the active oxide
was in fact a big breakthrough as it led to the development of vildagliptin
and saxagliptin
. One major problem in DPP-4 inhibitor stability is intramolecular
cyclisation. The precondition for the intramolecular
cyclisation is the conversion of the trans-rotamer, which is the DPP-4 binding rotamer(Figure 5). Thus, preventing this conversion will increase stability. This prevention was successful when incorporating an amide group into a ring, creating a compound that kept the DPP-4 inhibitory activity that, did not undergo the intramolecular
cyclisation and was even more selective over different DPP enzymes. It has also been reported that a cyanoazetidine in the P1 position and a β-amino acid in the P2 position increased stability.
Vildagliptin
(Galvus)(Figure 6) was first synthesized in May 1998 and was named after Edwin B. Villhauer. It was discovered when researchers at Novartis
examined adamantyl derivative
s that had proven to be very potent
. The adamantyl group worked as a steric bulk and slowed intramolecular
cyclization while increasing chemical stability. Furthermore, the primary metabolite
s were highly active. To avoid additional chiral center a hydroxylation
at the adamantyl ring was carried out (Figure 5). The product, vildagliptin
, was even more stable, undergoing intramolecular
cyclisation 30-times slower, and having high DPP-4 inhibitory activity and longer-lasting pharmacodynamic effect.
Researchers at Bristol-Myers Squibb
found that increased steric bulk of the N-terminal amino acid
side-chain led to increased stability. To additionally increase stability the trans-rotamer was stabilized with a cis-4,5-methano substitution of the pyrrolidine
ring, resulting in an intramolecular
van-der-Waals
interaction, thus preventing intramolecular
cyclisation. Because of that increased stability, the researchers continued their investigation on cis-4,5-methano cyanopyrrolidines and came across with a new adamantyl derivative
, which showed extraordinary ex vivo DPP-4 inhibition in rat plasma. Also noted, high microsomal turnover rate which indicated that the derivative was quickly converted to an active metabolite
. After hydroxylation
on the adamantyl group they had a product with better microsomal stability and improved chemical stability. That product was named saxagliptin
(Onglyza)(Figure 6). In June 2008 AstraZeneca
and Bristol-Myers Squibb
submitted a new drug application for Onglyza
in the United States
and a marketing authorization application in Europe
. Approval is still pending.
Denagliptin (Figure 6) is an advanced compound
with a branched side-chain at the P2 position, but also has (4S)-fluoro substitution on the cyanopyrrolidine ring. It is a well-known DPP-4 inhibitor developed by GlaxoSmithKline
(GSK). Biological evaluations have shown that the S-configuration of the amino acid
portion is essential for the inhibitory activity since the R-configuration showed reluctantly inhibition. These findings will be useful in future designs and synthesis of DPP-4 inhibitors. GSK
suspended phase-III clinical trials in October 2008.
-based DPP-4 inhibitors can roughly be grouped into three main subcategories; 2-cyanoazetidines, 3-fluoroazetidines, and 2-ketoazetidines. The most potent ketoazetidines and cyanoazetidines have large hydrophobic amino acid
groups bound to the azetidine
nitrogen
and are active below 100nM.
do not take after dipeptidic nature of DPP-4 substrates. They are non-covalent inhibitors and usually have an aromatic ring that occupies the S1-pocket, instead of the proline mimetic.
In 1999, Merck
started a drug development program on DPP-4 inhibitors. When they started internal screening and medicinal chemistry
program, two DPP-4 inhibitors were already in clinical trials, isoleucyl thiazolidide (P32/38) and NVP-DPP728 from Novartis
. Merck
in-licensed L-threo-isoleucyl thiazolidide
and its allo stereoisomer. In animal studies, they found that both isomers had similar affinity for DPP-4, similar in vivo efficacy, similar pharmacokinetic and metabolic profiles. Nevertheless, the allo isomer was 10-fold more toxic. The researchers found out that this difference in toxicity
was due to the allo isomer's greater inhibition of DPP-8
and DPP-9
but not because of selective DPP-4 inhibition. More research also supported that DPP-4 inhibition would not cause compromised immune function. Once this link between affinity for DPP-8/DPP-9 and toxicity
was discovered, Merck
decided on identifying an inhibitor with more than a thousandfold affinity for DPP-4 over the other dipeptidases. For this purpose, they used positional scanning libraries. From scanning these libraries, the researchers discovered that both DPP-4 and DPP-8
showed a strong preference for breaking down peptide
s with a proline
at the P1 position but they found a great difference at the P2 site; i.e., they found that acidic functionality at the P2 position could provide a greater affinity for DPP-4 over DPP-8
. Merck
kept up doing even more research and screening. They stopped working on compounds from the α-amino acid series related to isoleucyl thiazolidide
due to lack of selectivity but instead they discovered a very selective β-amino acid
piperazine
series through SAR
studies on two screening leads. When trying to stabilize the piperazine
moiety, a group of bicyclic derivatives were made, which led to the identification of a potent
and selective triazolopiperazine series. Most of these analogs showed excellent pharmacokinetic properties in preclinical species. Optimization of these compounds finally led to the discovery of sitagliptin
.
Sitagliptin
(Januvia) has a novel structure with β-amino amide derivatives
(Figure 7). Since sitagliptin
has shown excellent selectivity and in vivo efficacy it urged researches to inspect the new structure of DPP-4 inhibitors with appended β-amino acid
moiety. Further studies are being developed to optimize these compounds for the treatment of diabetes.
In October 2006 Sitagliptin
became the first DPP-4 inhibitor that got FDA approval for the treatment of type 2 diabetes. Crystallographic structure of sitagliptin
along with molecular modeling has been used to continue the search for structurally diverse inhibitors. A new potent
, selective and orally bioavailable DPP-4 inhibitor was discovered by replacing the central cyclohexylamine
in sitagliptin
with 3-aminopiperidine. A 2-pyridyl substitution was the initial SAR breakthrough since that group plays a significant role in potency and selectivity for DPP-4.
It has been shown with an X-ray
crystallography
how sitagliptin
binds to the DPP-4 complex:
1. The trifluorophenyl group occupies the S1-pocket
2. The trifluoromethyl group interacts with the side chains of residues Arg358 and Ser209.
3. The amino group forms a salt bridge
with Tyr662 and the carboxylated groups of the two glutamate residues, Glu205 and Glu206.
4. The triazolopiperazine group collides with the phenyl group
of residue Phe357
identified three novel series of DPP-4 inhibitors using HTS. After more research and optimization ABT-341 was discovered (Figure 8). It is a potent and selective DPP-4 inhibitor with a 2D-structure very similar to sitagliptin
. However, the 3D-structure is quite different. ABT-341 also has a trifluorophenyl group that occupies the S1-pocket and the free amino group, but the two carbonyl groups are orientated 180° away from each other. ABT-341 is also believed to interact with the Tyr547, probably because of steric hindrance between the cyclohexenyl ring and the tyrosine
side-chain.
type of DPP-4 inhibitors was first discovered after HTS. Research showed that the pyrrolidine
rings were the part of the compounds that fit into the binding site
. Further development has led to fluoro substituted pyrrolidines that show superior activity, as well as pyrrolidine
s with fused cyclopropylrings that are highly active.
s (Figure 10) as DPP-4 inhibitors came from Boehringer-Ingelheim
(BI) and Novo Nordisk
.
When xanthine
based DPP-4 inhibitors are compared with sitagliptin
and vildagliptin
it has shown a superior profile. Xanthines are believed to have higher potency
, longer-lasting inhibition and longer-lasting improvement of glucose tolerance.
Alogliptin
(Figure 9) is a novel DPP-4 inhibitor developed by the Takeda Pharmaceutical Company
. Researchers hypothesized that a quinazolinone
based structure (Figure 9) would have the necessary groups to interact with the active site
on the DPP-4 complex
. Quinazolinone
based compounds interacted effectively with the DPP-4 complex, but suffered from low metabolic half-life
. It was found that when replacing the quinazolinone
with a pyrimidinedione, the metabolic stability was increased and the result was a potent
, selective, bioavailable DPP-4 inhibitor named alogliptin
. The quinazoline based compounds showed potent inhibition and excellent selectivity over related protease
, DPP-8
. However, short metabolic half-life
due to oxidation of the A-ring phenyl group was problematic. At first, the researchers tried to make a fluorinated derivative. The derivative showed improved metabolic stability and excellent inhibition of the DPP-4 enzyme. However, it was also found to inhibit CYP 450 3A4 and block the hERG
channel. The solution to this problem was to replace the quinazolinone
with other heterocycles, but the quinazolinone
could be replaced without any loss of DPP-4 inhibition. Alogliptin
was discovered when quinazolinone was replaced with a pyrimidinedione
. Alogliptin
has shown excellent inhibition of DPP-4 and extraordinary selectivity, greater than 10.000 fold over the closely related serine proteases DPP-8
and DPP-9
. Also, it does not inhibit the CYP 450 enzymes nor block the hERG
channel at concentration up to 30µM. Based on this data, alogliptin
was chosen for preclinical evaluation. In January 2007 alogliptin
was undergoing the phase III clinical trial
and in October 2008 it was being reviewed by the U.S. Food and Drug Administration.
Researchers at BI discovered that using a buty-2-nyl group resulted in a potent candidate, called BI-1356 (Figure 10). In 2008 BI-1356 was undergoing phase III clinical trials; it was released as linagliptin
in May 2011. X-ray crystallography
has shown that that xanthine
type binds the DPP-4 complex in a different way than other inhibitors
:
1. The amino group also interacts with the Glu205, Glu206 and Tyr662
2. The buty-2-nyl group occupies the S1-pocket
3. The uracil group undergoes a π-stacking interaction with the Tyr547 residue
4. The quinazoline group undergoes a π-stacking interaction with the Trp629 residue
The pharmacokinetic properties of sitagliptin and vildagliptin appear unaffected by age, sex or BMI
. Clinical research
es have shown that sitagliptin
and vildagliptin
do not have the side effects
that tend to follow type 2 diabetes treatment, e.g. weight gain
and hyperglycemia
, but however, other side effects have been observed, including upper respiratory tract
infection
s, sore throat
and diarrhea
.
Dipeptidyl peptidase-4 inhibitors
Inhibitors of dipeptidyl peptidase 4, also DPP-4 inhibitors or gliptins, are a class of oral hypoglycemics that block DPP-4. They can be used to treat diabetes mellitus type 2....
(DPP-4 inhibitors) are enzyme inhibitors that inhibit the enzyme
Enzyme
Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...
dipeptidyl peptidase-4
Dipeptidyl peptidase-4
Dipeptidyl peptidase-4 , also known as adenosine deaminase complexing protein 2 or CD26 is a protein that, in humans, is encoded by the DPP4 gene.-Function:...
(DPP-4) and are a potent
Potency (pharmacology)
In the field of pharmacology, potency is a measure of drug activity expressed in terms of the amount required to produce an effect of given intensity. A highly potent drug evokes a larger response at low concentrations, while a drug of lower potency evokes a small response at low concentrations...
treatment for type 2 diabetes. Inhibition of the DPP-4
Dipeptidyl peptidase-4
Dipeptidyl peptidase-4 , also known as adenosine deaminase complexing protein 2 or CD26 is a protein that, in humans, is encoded by the DPP4 gene.-Function:...
enzyme prolongs and enhances the activity of incretins that play an important role in insulin
Insulin
Insulin is a hormone central to regulating carbohydrate and fat metabolism in the body. Insulin causes cells in the liver, muscle, and fat tissue to take up glucose from the blood, storing it as glycogen in the liver and muscle....
secretion and blood glucose control regulation.
Type 2 diabetes is a chronic metabolic disease that can be caused by pancreas β-cell dysfunction, deficiency in insulin
Insulin
Insulin is a hormone central to regulating carbohydrate and fat metabolism in the body. Insulin causes cells in the liver, muscle, and fat tissue to take up glucose from the blood, storing it as glycogen in the liver and muscle....
secretion, insulin
Insulin
Insulin is a hormone central to regulating carbohydrate and fat metabolism in the body. Insulin causes cells in the liver, muscle, and fat tissue to take up glucose from the blood, storing it as glycogen in the liver and muscle....
resistance and/or increased hepatic glucose production. It is one of the fastest growing health concerns in the world
World
World is a common name for the whole of human civilization, specifically human experience, history, or the human condition in general, worldwide, i.e. anywhere on Earth....
. Current treatment
Therapy
This is a list of types of therapy .* Adventure therapy* Animal-assisted therapy* Aquatic therapy* Aromatherapy* Art and dementia* Art therapy* Authentic Movement* Behavioral therapy* Bibliotherapy* Buteyko Method* Chemotherapy...
s are often inefficient at sustaining glycemic control and may cause undesirable side effect
Adverse effect
In medicine, an adverse effect is a harmful and undesired effect resulting from a medication or other intervention such as surgery.An adverse effect may be termed a "side effect", when judged to be secondary to a main or therapeutic effect. If it results from an unsuitable or incorrect dosage or...
s, such as weight gain
Weight gain
Weight gain is an increase in body weight. This can be either an increase in muscle mass, fat deposits, or excess fluids such as water.-Description:...
and episodes of hypoglycemia
Hypoglycemia
Hypoglycemia or hypoglycæmia is the medical term for a state produced by a lower than normal level of blood glucose. The term literally means "under-sweet blood"...
. Therefore, new and more effective drugs have been developed with DPP-4 inhibitors playing a significant role.
History
Since its discovery in 1967, serine protease DPP-4 has been a popular subject of research. Inhibitors of DPP-4 have long been sought as tools to elucidate the functional significance of the enzymeEnzyme
Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...
. The first inhibitors were characterized in the late 1980s
1980s
File:1980s decade montage.png|thumb|400px|From left, clockwise: The first Space Shuttle, Columbia, lifted off in 1981; American President Ronald Reagan and Soviet leader Mikhail Gorbachev eased tensions between the two superpowers, leading to the end of the Cold War; The Fall of the Berlin Wall in...
and 1990s
1990s
File:1990s decade montage.png|From left, clockwise: The Hubble Space Telescope floats in space after it was taken up in 1990; American F-16s and F-15s fly over burning oil fields and the USA Lexie in Operation Desert Storm, also known as the 1991 Gulf War; The signing of the Oslo Accords on...
. Each inhibitor
Enzyme inhibitor
An enzyme inhibitor is a molecule that binds to enzymes and decreases their activity. Since blocking an enzyme's activity can kill a pathogen or correct a metabolic imbalance, many drugs are enzyme inhibitors. They are also used as herbicides and pesticides...
was important to establish an early structure activity relationship (SAR) for subsequent investigation. It should be noted that the inhibitors fall into two main classes, those that interact covalent with DPP-4 and those that do not. DPP-4
Dipeptidyl peptidase-4
Dipeptidyl peptidase-4 , also known as adenosine deaminase complexing protein 2 or CD26 is a protein that, in humans, is encoded by the DPP4 gene.-Function:...
is a dipeptidase
Dipeptidase
Dipeptidases are enzymes secreted by enterocytes into the small intestine. Dipeptidases hydrolyze bound pairs of amino acids, called dipeptides....
that selectively binds substrate
Substrate (biochemistry)
In biochemistry, a substrate is a molecule upon which an enzyme acts. Enzymes catalyze chemical reactions involving the substrate. In the case of a single substrate, the substrate binds with the enzyme active site, and an enzyme-substrate complex is formed. The substrate is transformed into one or...
s that contain proline
Proline
Proline is an α-amino acid, one of the twenty DNA-encoded amino acids. Its codons are CCU, CCC, CCA, and CCG. It is not an essential amino acid, which means that the human body can synthesize it. It is unique among the 20 protein-forming amino acids in that the α-amino group is secondary...
at the P1-position, thus many DPP-4 inhibitors have 5-membered heterocyclic rings that mimic
Mimic
In evolutionary biology, mimicry is the similarity of one species to another which protects one or both. This similarity can be in appearance, behaviour, sound, scent and even location, with the mimics found in similar places to their models....
proline
Proline
Proline is an α-amino acid, one of the twenty DNA-encoded amino acids. Its codons are CCU, CCC, CCA, and CCG. It is not an essential amino acid, which means that the human body can synthesize it. It is unique among the 20 protein-forming amino acids in that the α-amino group is secondary...
, e.g. pyrrolidine
Pyrrolidine
Pyrrolidine, also known as tetrahydropyrrole, is an organic compound with the molecular formula C4H9N. It is a cyclic secondary amine with a five-membered heterocycle containing four carbon atoms and one nitrogen atom...
, cyanopyrrolidine, thiazolidine
Thiazolidine
Thiazolidines are a class of heterocyclic organic compounds with a 5-membered saturated ring with a thioether group and an amine group in the 1 and 3 positions, respectively. It is a sulfur analogue of oxazolidine. The drug pioglitazone contains a thiazolidine ring. It is a drug usually indicated...
and cyanothiazolidine. These compounds commonly form covalent bonds to the catalytic residue Ser630.
In 1994, researchers from Zeria Pharmaceuticals unveiled cyanopyrrolidines with a nitrile
Nitrile
A nitrile is any organic compound that has a -C≡N functional group. The prefix cyano- is used interchangeably with the term nitrile in industrial literature. Nitriles are found in many useful compounds, one example being super glue .Inorganic compounds containing the -C≡N group are not called...
function group that was assumed to form an imidate with the catalytic serine
Serine
Serine is an amino acid with the formula HO2CCHCH2OH. It is one of the proteinogenic amino acids. By virtue of the hydroxyl group, serine is classified as a polar amino acid.-Occurrence and biosynthesis:...
. Concurrently other DPP-4 inhibitors without a nitrile
Nitrile
A nitrile is any organic compound that has a -C≡N functional group. The prefix cyano- is used interchangeably with the term nitrile in industrial literature. Nitriles are found in many useful compounds, one example being super glue .Inorganic compounds containing the -C≡N group are not called...
group were published but they contained other serine-interacting motifs, e.g. boronic acids, phosphonate
Phosphonate
Phosphonates or phosphonic acids are organic compounds containing C-PO2 or C-PO2 groups . Bisphosphonates were first synthesized in 1897 by Von Baeyer and Hofmann. An example of such a bisphosphonate is HEDP . Since the work of Schwarzenbach in 1949, phosphonic acids are known as effective...
s or diacyl hydroxylamine
Hydroxylamine
Hydroxylamine is an inorganic compound with the formula NH2OH. The pure material is a white, unstable crystalline, hygroscopic compound. However, hydroxylamine is almost always provided and used as an aqueous solution. It is used to prepare oximes, an important functional group. It is also an...
s. These compound
Chemical compound
A chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together...
s were not as potent because of the similarity of DPP-4
Dipeptidyl peptidase-4
Dipeptidyl peptidase-4 , also known as adenosine deaminase complexing protein 2 or CD26 is a protein that, in humans, is encoded by the DPP4 gene.-Function:...
and prolyl oligopeptidase (PEP) and also suffered from chemical instability
Instability
In numerous fields of study, the component of instability within a system is generally characterized by some of the outputs or internal states growing without bounds...
. Ferring Pharmaceuticals
Ferring Pharmaceuticals
Ferring Pharmaceuticals is a pharmaceutical company that specializes in the development and marketing of drugs for use in human medicine.It was founded by Frederik Paulsen Sr in Malmö, Sweden, in 1950, initially as the Nordiska Hormon Laboratoriet, renamed Ferring in 1954. A ferring in Frisian is a...
filed for patent on two cyanopyrrolidine DPP-4 inhibitors, which they published in 1995. These compounds had excellent potency
Potency (pharmacology)
In the field of pharmacology, potency is a measure of drug activity expressed in terms of the amount required to produce an effect of given intensity. A highly potent drug evokes a larger response at low concentrations, while a drug of lower potency evokes a small response at low concentrations...
and improved chemical stability.
In 1995, Edwin B. Villhauer at Novartis
Novartis
Novartis International AG is a multinational pharmaceutical company based in Basel, Switzerland, ranking number three in sales among the world-wide industry...
started to explore N-substituted glycinyl-cyanopyrrolidines based on the fact that DPP-4 identifies N-methylglycine as a N-terminal amino acid
Amino acid
Amino acids are molecules containing an amine group, a carboxylic acid group and a side-chain that varies between different amino acids. The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen...
. This group of new cyanopyrrolidines became extremely popular field of research in the following years. Some trials with dual inhibitors of DPP-4 and vasopeptidase have been represented, since vasopeptidase inhibition is believed to enhance the antidiabetic effect of DPP-4 inhibition
Dipeptidyl peptidase-4 inhibitors
Inhibitors of dipeptidyl peptidase 4, also DPP-4 inhibitors or gliptins, are a class of oral hypoglycemics that block DPP-4. They can be used to treat diabetes mellitus type 2....
by stimulating insulin
Insulin
Insulin is a hormone central to regulating carbohydrate and fat metabolism in the body. Insulin causes cells in the liver, muscle, and fat tissue to take up glucose from the blood, storing it as glycogen in the liver and muscle....
secretion. Vasopeptidase-inhibiting motif is connected to the DPP-4 inhibitor at the N-substituent.
DPP-4 mechanism
Meal
A meal is an instance of eating, specifically one that takes place at a specific time and includes specific, prepared food.Meals occur primarily at homes, restaurants, and cafeterias, but may occur anywhere. Regular meals occur on a daily basis, typically several times a day...
the incretin
Incretin
Incretins are a group of gastrointestinal hormones that cause an increase in the amount of insulin released from the beta cells of the islets of Langerhans after eating, even before blood glucose levels become elevated. They also slow the rate of absorption of nutrients into the blood stream by...
s glucagon-like peptide 1 (GLP-1) and glucose-dependent gastric inhibitory polypeptide (GIP) are released from the small intestine
Small intestine
The small intestine is the part of the gastrointestinal tract following the stomach and followed by the large intestine, and is where much of the digestion and absorption of food takes place. In invertebrates such as worms, the terms "gastrointestinal tract" and "large intestine" are often used to...
into the vasculature. The hormone
Hormone
A hormone is a chemical released by a cell or a gland in one part of the body that sends out messages that affect cells in other parts of the organism. Only a small amount of hormone is required to alter cell metabolism. In essence, it is a chemical messenger that transports a signal from one...
s regulate insulin secretion in a glucose-dependent manner. GLP-1 has many roles in the human body
Human body
The human body is the entire structure of a human organism, and consists of a head, neck, torso, two arms and two legs.By the time the human reaches adulthood, the body consists of close to 100 trillion cells, the basic unit of life...
; it stimulates insulin biosynthesis, inhibits glucagon secretion, slows gastric emptying, reduces appetite and stimulates regeneration of islet β-cells.
GIP and GLP-1 have extremely short plasma half-lives due to a very rapid inactivation. The enzyme
Enzyme
Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...
responsible for the metabolism
Metabolism
Metabolism is the set of chemical reactions that happen in the cells of living organisms to sustain life. These processes allow organisms to grow and reproduce, maintain their structures, and respond to their environments. Metabolism is usually divided into two categories...
is DPP-4. Inhibition of DPP-4 leads to potentiation of endogenous GIP and GLP-1 and hence improves treatment of type 2 diabetes (Figure 1).
DPP-4 distribution and function
Amino acid
Amino acids are molecules containing an amine group, a carboxylic acid group and a side-chain that varies between different amino acids. The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen...
s from peptide
Peptide
Peptides are short polymers of amino acid monomers linked by peptide bonds. They are distinguished from proteins on the basis of size, typically containing less than 50 monomer units. The shortest peptides are dipeptides, consisting of two amino acids joined by a single peptide bond...
s, such as GLP-1 and GIP, which have proline
Proline
Proline is an α-amino acid, one of the twenty DNA-encoded amino acids. Its codons are CCU, CCC, CCA, and CCG. It is not an essential amino acid, which means that the human body can synthesize it. It is unique among the 20 protein-forming amino acids in that the α-amino group is secondary...
or alanine
Alanine
Alanine is an α-amino acid with the chemical formula CH3CHCOOH. The L-isomer is one of the 20 amino acids encoded by the genetic code. Its codons are GCU, GCC, GCA, and GCG. It is classified as a nonpolar amino acid...
in the second position (Figure 2). At the active site
Active site
In biology the active site is part of an enzyme where substrates bind and undergo a chemical reaction. The majority of enzymes are proteins but RNA enzymes called ribozymes also exist. The active site of an enzyme is usually found in a cleft or pocket that is lined by amino acid residues that...
of the protease
Protease
A protease is any enzyme that conducts proteolysis, that is, begins protein catabolism by hydrolysis of the peptide bonds that link amino acids together in the polypeptide chain forming the protein....
there is a characteristic motif of three amino acid
Amino acid
Amino acids are molecules containing an amine group, a carboxylic acid group and a side-chain that varies between different amino acids. The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen...
s, Asp-His-Ser. DPP-4 is the CD26 T-cell-activating antigen
Antigen
An antigen is a foreign molecule that, when introduced into the body, triggers the production of an antibody by the immune system. The immune system will then kill or neutralize the antigen that is recognized as a foreign and potentially harmful invader. These invaders can be molecules such as...
, which is widely distributed in human organs
Organ (anatomy)
In biology, an organ is a collection of tissues joined in structural unit to serve a common function. Usually there is a main tissue and sporadic tissues . The main tissue is the one that is unique for the specific organ. For example, main tissue in the heart is the myocardium, while sporadic are...
and tissue. Tissue
Tissue (biology)
Tissue is a cellular organizational level intermediate between cells and a complete organism. A tissue is an ensemble of cells, not necessarily identical, but from the same origin, that together carry out a specific function. These are called tissues because of their identical functioning...
s, which strongly express DPP-4, include the exocrine pancreas
Exocrine pancreas
The exocrine pancreas has ducts that are arranged in clusters called acini . Pancreatic secretions are secreted into the lumen of the acinus, and then accumulate in intralobular ducts that drain to the main pancreatic duct, which drains directly into the duodenum.Control of the exocrine function of...
, sweat glands, salivary
Salivary gland
The salivary glands in mammals are exocrine glands, glands with ducts, that produce saliva. They also secrete amylase, an enzyme that breaks down starch into maltose...
and mammary glands, thymus
Thymus
The thymus is a specialized organ of the immune system. The thymus produces and "educates" T-lymphocytes , which are critical cells of the adaptive immune system....
, lymph nodes, biliary tract, kidney
Kidney
The kidneys, organs with several functions, serve essential regulatory roles in most animals, including vertebrates and some invertebrates. They are essential in the urinary system and also serve homeostatic functions such as the regulation of electrolytes, maintenance of acid–base balance, and...
, liver
Liver
The liver is a vital organ present in vertebrates and some other animals. It has a wide range of functions, including detoxification, protein synthesis, and production of biochemicals necessary for digestion...
, placenta
Placenta
The placenta is an organ that connects the developing fetus to the uterine wall to allow nutrient uptake, waste elimination, and gas exchange via the mother's blood supply. "True" placentas are a defining characteristic of eutherian or "placental" mammals, but are also found in some snakes and...
, uterus
Uterus
The uterus or womb is a major female hormone-responsive reproductive sex organ of most mammals including humans. One end, the cervix, opens into the vagina, while the other is connected to one or both fallopian tubes, depending on the species...
, prostate
Prostate
The prostate is a compound tubuloalveolar exocrine gland of the male reproductive system in most mammals....
, skin
Skin
-Dermis:The dermis is the layer of skin beneath the epidermis that consists of connective tissue and cushions the body from stress and strain. The dermis is tightly connected to the epidermis by a basement membrane. It also harbors many Mechanoreceptors that provide the sense of touch and heat...
and the capillary bed of the gut
Gut (zoology)
In zoology, the gut, also known as the alimentary canal or alimentary tract, is a tube by which bilaterian animals transfer food to the digestion organs. In large bilaterians the gut generally also has an exit, the anus, by which the animal disposes of solid wastes...
mucosa where most GLP-1 is inactivated locally. DPP-4 is attached to the plasma membrane of the endothelia of almost all organs in the body
Body
With regard to living things, a body is the physical body of an individual. "Body" often is used in connection with appearance, health issues and death...
. It is also present in body fluids, such as blood plasma
Blood plasma
Blood plasma is the straw-colored liquid component of blood in which the blood cells in whole blood are normally suspended. It makes up about 55% of the total blood volume. It is the intravascular fluid part of extracellular fluid...
and cerebrospinal fluid
Cerebrospinal fluid
Cerebrospinal fluid , Liquor cerebrospinalis, is a clear, colorless, bodily fluid, that occupies the subarachnoid space and the ventricular system around and inside the brain and spinal cord...
, in a soluble form. DPP-4 inactivates GLP-1 and GIP very rapidly. Regarding GIP and GLP-1, alanine
Alanine
Alanine is an α-amino acid with the chemical formula CH3CHCOOH. The L-isomer is one of the 20 amino acids encoded by the genetic code. Its codons are GCU, GCC, GCA, and GCG. It is classified as a nonpolar amino acid...
and proline
Proline
Proline is an α-amino acid, one of the twenty DNA-encoded amino acids. Its codons are CCU, CCC, CCA, and CCG. It is not an essential amino acid, which means that the human body can synthesize it. It is unique among the 20 protein-forming amino acids in that the α-amino group is secondary...
are crucial for biological activity
Biological activity
In pharmacology, biological activity or pharmacological activity describes the beneficial or adverse effects of a drug on living matter. When a drug is a complex chemical mixture, this activity is exerted by the substance's active ingredient or pharmacophore but can be modified by the other...
, so elimination of these amino acid
Amino acid
Amino acids are molecules containing an amine group, a carboxylic acid group and a side-chain that varies between different amino acids. The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen...
s leads to formation of metabolite
Metabolite
Metabolites are the intermediates and products of metabolism. The term metabolite is usually restricted to small molecules. A primary metabolite is directly involved in normal growth, development, and reproduction. Alcohol is an example of a primary metabolite produced in large-scale by industrial...
s that are inactive. Thus, preventing the degradation of the incretin
Incretin
Incretins are a group of gastrointestinal hormones that cause an increase in the amount of insulin released from the beta cells of the islets of Langerhans after eating, even before blood glucose levels become elevated. They also slow the rate of absorption of nutrients into the blood stream by...
hormone
Hormone
A hormone is a chemical released by a cell or a gland in one part of the body that sends out messages that affect cells in other parts of the organism. Only a small amount of hormone is required to alter cell metabolism. In essence, it is a chemical messenger that transports a signal from one...
s GIP and GLP-1 by inhibition of DPP-4 is an exciting therapeutic strategy.
DPP-4 characteristics
Since DPP-4 is a proteaseProtease
A protease is any enzyme that conducts proteolysis, that is, begins protein catabolism by hydrolysis of the peptide bonds that link amino acids together in the polypeptide chain forming the protein....
, it is not unexpected that inhibitors would likely have a peptide
Peptide
Peptides are short polymers of amino acid monomers linked by peptide bonds. They are distinguished from proteins on the basis of size, typically containing less than 50 monomer units. The shortest peptides are dipeptides, consisting of two amino acids joined by a single peptide bond...
nature and this theme has carried through to contemporary research.
Structure
X-rayX-ray
X-radiation is a form of electromagnetic radiation. X-rays have a wavelength in the range of 0.01 to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz and energies in the range 120 eV to 120 keV. They are shorter in wavelength than UV rays and longer than gamma...
structures of DPP-4
Dipeptidyl peptidase-4
Dipeptidyl peptidase-4 , also known as adenosine deaminase complexing protein 2 or CD26 is a protein that, in humans, is encoded by the DPP4 gene.-Function:...
that have been published since 2003 give rather detailed information about the structural characteristics of the binding site
Binding site
In biochemistry, a binding site is a region on a protein, DNA, or RNA to which specific other molecules and ions—in this context collectively called ligands—form a chemical bond...
. Many structurally diverse DPP-4 inhibitors have been discovered and it is not that surprising considering the properties of the binding site:
1. A deep lipophilic
Lipophilic
Lipophilicity, , refers to the ability of a chemical compound to dissolve in fats, oils, lipids, and non-polar solvents such as hexane or toluene. These non-polar solvents are themselves lipophilic — the axiom that like dissolves like generally holds true...
pocket combined with several exposed aromatic side chain
Side chain
In organic chemistry and biochemistry, a side chain is a chemical group that is attached to a core part of the molecule called "main chain" or backbone. The placeholder R is often used as a generic placeholder for alkyl group side chains in chemical structure diagrams. To indicate other non-carbon...
s for achieving high affinity small molecule binding.
2. A significant solvent
Solvent
A solvent is a liquid, solid, or gas that dissolves another solid, liquid, or gaseous solute, resulting in a solution that is soluble in a certain volume of solvent at a specified temperature...
access that makes it possible to tune the physico-chemical properties of the inhibitors that leads to better pharmacokinetic behavior.
DPP-4 is a 766-amino acid transmembrane glycoprotein
Transmembrane protein
A transmembrane protein is a protein that goes from one side of a membrane through to the other side of the membrane. Many TPs function as gateways or "loading docks" to deny or permit the transport of specific substances across the biological membrane, to get into the cell, or out of the cell as...
that belongs to the prolyloligopeptidase family. It consists of three parts; a cytoplasmic tail, a transmembrane region and an extracellular
Extracellular
In cell biology, molecular biology and related fields, the word extracellular means "outside the cell". This space is usually taken to be outside the plasma membranes, and occupied by fluid...
part. The extracellular
Extracellular
In cell biology, molecular biology and related fields, the word extracellular means "outside the cell". This space is usually taken to be outside the plasma membranes, and occupied by fluid...
part is divided into a catalytic domain and an eight-bladed β-propeller domain. The latter contributes to the inhibitor binding site. The catalytic domain shows an α/β-hydrolase fold and contains the catalytic triad Ser630 - Asp708 - His740. The S1-pocket is very hydrophobic and is composed of the side chains: Tyr631, Val656, Trp662, Tyr666 and Val711. Existing X-ray
X-ray
X-radiation is a form of electromagnetic radiation. X-rays have a wavelength in the range of 0.01 to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz and energies in the range 120 eV to 120 keV. They are shorter in wavelength than UV rays and longer than gamma...
structures show that there is not much difference in size and shape of the pocket that indicates that the S1-pocket has high specificity for proline
Proline
Proline is an α-amino acid, one of the twenty DNA-encoded amino acids. Its codons are CCU, CCC, CCA, and CCG. It is not an essential amino acid, which means that the human body can synthesize it. It is unique among the 20 protein-forming amino acids in that the α-amino group is secondary...
residues
Binding site
Hydroxyl
A hydroxyl is a chemical group containing an oxygen atom covalently bonded with a hydrogen atom. In inorganic chemistry, the hydroxyl group is known as the hydroxide ion, and scientists and reference works generally use these different terms though they refer to the same chemical structure in...
of the catalytic serine in the active binding site (Figure 3). Frequently that group is a nitrile
Nitrile
A nitrile is any organic compound that has a -C≡N functional group. The prefix cyano- is used interchangeably with the term nitrile in industrial literature. Nitriles are found in many useful compounds, one example being super glue .Inorganic compounds containing the -C≡N group are not called...
group but can also be boronic acid
Boronic acid
A boronic acid is an alkyl or aryl substituted boric acid containing a carbon–boron bond belonging to the larger class of organoboranes. Boronic acids act as Lewis acids. Their unique feature is that they are capable of forming reversible covalent complexes with sugars, amino acids, hydroxamic...
or diphenyl phosphonate
Phosphonate
Phosphonates or phosphonic acids are organic compounds containing C-PO2 or C-PO2 groups . Bisphosphonates were first synthesized in 1897 by Von Baeyer and Hofmann. An example of such a bisphosphonate is HEDP . Since the work of Schwarzenbach in 1949, phosphonic acids are known as effective...
. This electrophilic group can bind to the imidate complex
Complex
A complex is a whole that comprehends a number of intricate parts, especially one with interconnected or mutually related parts; for example, a complex of buildings.Complex may refer to:-Biology:...
with covalent bonds and slow, tight-binding kinetics but this group is also responsible for stability issues due to reaction
Reaction
Reaction may refer to:Response to another event*Adverse drug reaction*Chemical reaction*Emotional reaction*Light reaction*Nuclear reaction*TNA Reaction, a documentary show of TNA behind scenes.*Reaction , as defined by Newton's third law...
s with the free amino group of the P2-amino acid. Therefore inhibitors without the electrophilic group have also been developed, but these molecule
Molecule
A molecule is an electrically neutral group of at least two atoms held together by covalent chemical bonds. Molecules are distinguished from ions by their electrical charge...
s have shown toxicity
Toxicity
Toxicity is the degree to which a substance can damage a living or non-living organisms. Toxicity can refer to the effect on a whole organism, such as an animal, bacterium, or plant, as well as the effect on a substructure of the organism, such as a cell or an organ , such as the liver...
due to affinity to other dipeptidyl peptidases, e.g. DPP-2, DPP-8
DPP8
Dipeptidyl peptidase 8 is an enzyme that in humans is encoded by the DPP8 gene.-References:NotesFurther reading...
and DPP-9
DPP9
Dipeptidyl peptidase 9 is an enzyme that in humans is encoded by the DPP9 gene.-Further reading:...
.
DPP-4 inhibitors span diverse structural types. In 2007 few of the most potent
Potency (pharmacology)
In the field of pharmacology, potency is a measure of drug activity expressed in terms of the amount required to produce an effect of given intensity. A highly potent drug evokes a larger response at low concentrations, while a drug of lower potency evokes a small response at low concentrations...
compounds contain a proline
Proline
Proline is an α-amino acid, one of the twenty DNA-encoded amino acids. Its codons are CCU, CCC, CCA, and CCG. It is not an essential amino acid, which means that the human body can synthesize it. It is unique among the 20 protein-forming amino acids in that the α-amino group is secondary...
mimetic
Mimetic
In mathematics, mimesis is the quality of a numerical method which imitates some properties of the continuum problem. The goal of numerical analysis is to approximate the continuum, so instead of solving a partial differential equation one aims to solve a discrete version of the continuum problem...
cyanopyrrolidine P1 group. This group enhances the potency, probably due to a transient covalent trapping of the nitrile
Nitrile
A nitrile is any organic compound that has a -C≡N functional group. The prefix cyano- is used interchangeably with the term nitrile in industrial literature. Nitriles are found in many useful compounds, one example being super glue .Inorganic compounds containing the -C≡N group are not called...
group by the active site Ser630 hydroxyl, leading to delayed dissociation and slow tight binding of certain inhibitors. When these potency enhancements were achieved, some chemical stability issues were noted and more advanced molecules had to be made. To avoid these stability issues, the possibility to exclude the nitrile
Nitrile
A nitrile is any organic compound that has a -C≡N functional group. The prefix cyano- is used interchangeably with the term nitrile in industrial literature. Nitriles are found in many useful compounds, one example being super glue .Inorganic compounds containing the -C≡N group are not called...
group was investigated. Amino acids with aryl
Aryl
In the context of organic molecules, aryl refers to any functional group or substituent derived from an aromatic ring, be it phenyl, naphthyl, thienyl, indolyl, etc....
or polar
Chemical polarity
In chemistry, polarity refers to a separation of electric charge leading to a molecule or its chemical groups having an electric dipole or multipole moment. Polar molecules interact through dipole–dipole intermolecular forces and hydrogen bonds. Molecular polarity is dependent on the difference in...
side chains did not show appreciable DPP-4 inhibition
Dipeptidyl peptidase-4 inhibitors
Inhibitors of dipeptidyl peptidase 4, also DPP-4 inhibitors or gliptins, are a class of oral hypoglycemics that block DPP-4. They can be used to treat diabetes mellitus type 2....
and in fact, all compounds without the nitrile group in this research suffered a 20 to 50-fold loss of potency corresponding to the compounds containing the nitrile
Nitrile
A nitrile is any organic compound that has a -C≡N functional group. The prefix cyano- is used interchangeably with the term nitrile in industrial literature. Nitriles are found in many useful compounds, one example being super glue .Inorganic compounds containing the -C≡N group are not called...
group.
Discovery and development
It is important to find a fast and accurate system to discover new DPP-4 inhibitors with ideal therapeutic profiles. High throughput screening (HTS) usually gives low hit rates in identifying the inhibitors but virtual screeningVirtual screening
Virtual screening is a computational technique used in drug discovery research. By using computers, it deals with the quick search of large libraries of chemical structures in order to identify those structures which are most likely to bind to a drug target, typically a protein receptor or...
(VS) can give higher rates. VS
Virtual screening
Virtual screening is a computational technique used in drug discovery research. By using computers, it deals with the quick search of large libraries of chemical structures in order to identify those structures which are most likely to bind to a drug target, typically a protein receptor or...
has for example been used to screen for small primary aliphatic amines to identify fragment
Fragment
Fragment may refer to:* A small part/portion broken off something; debris* Fragment , all the data necessary to generate a pixel in the frame buffer* Sentence fragment, a sentence not containing a subject or a predicate...
s that could be placed in S1 and S2 sites of DPP-4
Dipeptidyl peptidase-4
Dipeptidyl peptidase-4 , also known as adenosine deaminase complexing protein 2 or CD26 is a protein that, in humans, is encoded by the DPP4 gene.-Function:...
. On the other hand, these fragments were not very potent and therefore identified as a starting point to design better ones.
Three-dimensional models
3D modeling
In 3D computer graphics, 3D modeling is the process of developing a mathematical representation of any three-dimensional surface of object via specialized software. The product is called a 3D model...
can provide a useful tool for designing novel DPP-4 inhibitors. Pharmacophore
Pharmacophore
thumb|right|300px|An example of a pharmacophore model.A pharmacophore is an abstract description of molecular features which are necessary for molecular recognition of a ligand by a biological macromolecule....
models have been made based on key chemical features of compound
Chemical compound
A chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together...
s with DPP-4 inhibitory activity. These models can provide a hypothetical picture of the primary chemical feature responsible for inhibitory activity.
The first DPP-4 inhibitors were reversible inhibitors and came with bad side effects
Adverse effect
In medicine, an adverse effect is a harmful and undesired effect resulting from a medication or other intervention such as surgery.An adverse effect may be termed a "side effect", when judged to be secondary to a main or therapeutic effect. If it results from an unsuitable or incorrect dosage or...
because of low selectivity. Researchers suspected that inhibitors with short half-lives would be preferred in order to minimize possible side effects
Adverse effect
In medicine, an adverse effect is a harmful and undesired effect resulting from a medication or other intervention such as surgery.An adverse effect may be termed a "side effect", when judged to be secondary to a main or therapeutic effect. If it results from an unsuitable or incorrect dosage or...
. However, since clinical trials showed the opposite, the latest DPP-4 inhibitors have a long-lasting effect. One of the first reported DPP-4 inhibitor was P32/98 from Merck
Merck & Co.
Merck & Co., Inc. , also known as Merck Sharp & Dohme or MSD outside the United States and Canada, is one of the largest pharmaceutical companies in the world. The Merck headquarters is located in Whitehouse Station, New Jersey, an unincorporated area in Readington Township...
. It used thiazolidide as the P1-substitute and was the first DPP-4 inhibitor that showed effects in both animal
Animal
Animals are a major group of multicellular, eukaryotic organisms of the kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life. Most animals are motile, meaning they can move spontaneously and...
s and human
Human
Humans are the only living species in the Homo genus...
s but it was not developed to a market drug
Drug
A drug, broadly speaking, is any substance that, when absorbed into the body of a living organism, alters normal bodily function. There is no single, precise definition, as there are different meanings in drug control law, government regulations, medicine, and colloquial usage.In pharmacology, a...
due to side effects
Adverse effect
In medicine, an adverse effect is a harmful and undesired effect resulting from a medication or other intervention such as surgery.An adverse effect may be termed a "side effect", when judged to be secondary to a main or therapeutic effect. If it results from an unsuitable or incorrect dosage or...
. Another old inhibitor is DPP-728 from Novartis
Novartis
Novartis International AG is a multinational pharmaceutical company based in Basel, Switzerland, ranking number three in sales among the world-wide industry...
, where 2-cyanopyrrolidine is used as the P1-substitute. The addition of the cyano group generally increases the potency. Therefore, researchers' attention was directed to those compounds. Usually, DPP-4 inhibitors are either substrate
Substrate (biochemistry)
In biochemistry, a substrate is a molecule upon which an enzyme acts. Enzymes catalyze chemical reactions involving the substrate. In the case of a single substrate, the substrate binds with the enzyme active site, and an enzyme-substrate complex is formed. The substrate is transformed into one or...
-like or non-substrate-like.
Substrate-like inhibitors
Substrate-like inhibitors (Figure 4) are more common than the non-substrate-likes. They bind either covalently or non-covalently and have a basic structure where the P1-substituent occupies the S1-pocket and the P2-substituent occupies the S2-pocket. Usually they contain a prolineProline
Proline is an α-amino acid, one of the twenty DNA-encoded amino acids. Its codons are CCU, CCC, CCA, and CCG. It is not an essential amino acid, which means that the human body can synthesize it. It is unique among the 20 protein-forming amino acids in that the α-amino group is secondary...
mimetic
Mimetic
In mathematics, mimesis is the quality of a numerical method which imitates some properties of the continuum problem. The goal of numerical analysis is to approximate the continuum, so instead of solving a partial differential equation one aims to solve a discrete version of the continuum problem...
that occupies the S1-pocket. Large substituents on the 2-cyanopyrrolidine ring are normally not tolerated since the S1-pocket is quite small.
Since DPP-4
Dipeptidyl peptidase-4
Dipeptidyl peptidase-4 , also known as adenosine deaminase complexing protein 2 or CD26 is a protein that, in humans, is encoded by the DPP4 gene.-Function:...
is identical with the T-cell activation marker CD26 and DPP-4 inhibitors are known to inhibit T-cell proliferation
Cell growth
The term cell growth is used in the contexts of cell development and cell division . When used in the context of cell division, it refers to growth of cell populations, where one cell grows and divides to produce two "daughter cells"...
, these compounds were initially thought to be potential immunomodulator
Immunomodulator
An immunomodulator, also known as an immunotherapy is a substance which has an effect on the immune system.- Immunosuppressants :Inhibits immune response in organ transplantation and autoimmune diseases.- Immunostimulants :...
s. When the function against type 2 diabetes was discovered, the cyanopyrrolidines became a highly popular research material. A little later vildagliptin
Vildagliptin
Vildagliptin is an oral anti-hyperglycemic agent of the new dipeptidyl peptidase-4 inhibitor class of drugs...
and saxagliptin
Saxagliptin
Saxagliptin , previously identified as BMS-477118, is a new oral hypoglycemic of the new dipeptidyl peptidase-4 inhibitor class of drugs. Early development was solely by Bristol-Myers Squibb; in 2007 AstraZeneca joined with Bristol-Myers Squibb to co-develop the final compound and collaborate on...
, which are the most developed cyanopyrrolidine DPP-4 inhibitors to date, were discovered.
Cyanopyrrolidines
Cyanopyrrolidines have two key interactions to the DPP-4 complex:1. Nitrile
Nitrile
A nitrile is any organic compound that has a -C≡N functional group. The prefix cyano- is used interchangeably with the term nitrile in industrial literature. Nitriles are found in many useful compounds, one example being super glue .Inorganic compounds containing the -C≡N group are not called...
in the position of the scissile bond of the peptidic substrate that is important for high potency. The nitrile group forms reversible covalent bonds with the catalytically active serine
Serine
Serine is an amino acid with the formula HO2CCHCH2OH. It is one of the proteinogenic amino acids. By virtue of the hydroxyl group, serine is classified as a polar amino acid.-Occurrence and biosynthesis:...
hydroxyl (Ser630), i.e. cyanopyrrolidines are competitive inhibitors with slow dissociation kinetics.
2. Hydrogen bond
Hydrogen bond
A hydrogen bond is the attractive interaction of a hydrogen atom with an electronegative atom, such as nitrogen, oxygen or fluorine, that comes from another molecule or chemical group. The hydrogen must be covalently bonded to another electronegative atom to create the bond...
ing network between the protonated amino group and a negatively charged
Electric charge
Electric charge is a physical property of matter that causes it to experience a force when near other electrically charged matter. Electric charge comes in two types, called positive and negative. Two positively charged substances, or objects, experience a mutual repulsive force, as do two...
region of the protein
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
surface, Glu205, Glu206 and Tyr662. All cyanopyrrolidines have basic, primary or secondary amine
Amine
Amines are organic compounds and functional groups that contain a basic nitrogen atom with a lone pair. Amines are derivatives of ammonia, wherein one or more hydrogen atoms have been replaced by a substituent such as an alkyl or aryl group. Important amines include amino acids, biogenic amines,...
, which makes this network possible but these compounds usually drop in potency if these amines are changed. Nonetheless, two patent applications unveil that the amino group can be changed, i.e. replaced by a hydrazine
Hydrazine
Hydrazine is an inorganic compound with the formula N2H4. It is a colourless flammable liquid with an ammonia-like odor. Hydrazine is highly toxic and dangerously unstable unless handled in solution. Approximately 260,000 tons are manufactured annually...
, but it is claimed that these compounds do not only act via DPP-4 inhibition but also prevent diabetic vascular complications by acting as a radical
Radical (chemistry)
Radicals are atoms, molecules, or ions with unpaired electrons on an open shell configuration. Free radicals may have positive, negative, or zero charge...
scavenger.
Structure-activity relationship (SAR)
Important structure-activity relationship
Structure-activity relationship
The structure–activity relationship is the relationship between the chemical or 3D structure of a molecule and its biological activity. The analysis of SAR enables the determination of the chemical groups responsible for evoking a target biological effect in the organism...
:
1. Strict steric constraint exists around the pyrrolidine
Pyrrolidine
Pyrrolidine, also known as tetrahydropyrrole, is an organic compound with the molecular formula C4H9N. It is a cyclic secondary amine with a five-membered heterocycle containing four carbon atoms and one nitrogen atom...
ring of cyanopyrrolidine-based inhibitors, with only hydrogen
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...
, fluoro, acetylene
Acetylene
Acetylene is the chemical compound with the formula C2H2. It is a hydrocarbon and the simplest alkyne. This colorless gas is widely used as a fuel and a chemical building block. It is unstable in pure form and thus is usually handled as a solution.As an alkyne, acetylene is unsaturated because...
, nitrile
Nitrile
A nitrile is any organic compound that has a -C≡N functional group. The prefix cyano- is used interchangeably with the term nitrile in industrial literature. Nitriles are found in many useful compounds, one example being super glue .Inorganic compounds containing the -C≡N group are not called...
, or methano substitution permitted.
2. Presence of a nitrile
Nitrile
A nitrile is any organic compound that has a -C≡N functional group. The prefix cyano- is used interchangeably with the term nitrile in industrial literature. Nitriles are found in many useful compounds, one example being super glue .Inorganic compounds containing the -C≡N group are not called...
moiety on the pyrrolidine
Pyrrolidine
Pyrrolidine, also known as tetrahydropyrrole, is an organic compound with the molecular formula C4H9N. It is a cyclic secondary amine with a five-membered heterocycle containing four carbon atoms and one nitrogen atom...
ring is critical to achieving potent activity
Also, systematic SAR investigation has shown that the ring size and stereochemistry
Stereochemistry
Stereochemistry, a subdiscipline of chemistry, involves the study of the relative spatial arrangement of atoms within molecules. An important branch of stereochemistry is the study of chiral molecules....
for the P2 position is quite conditioned. A 5-membered ring and L-configuration has shown better results than a 4-membered or 6-membered ring with D-configuration. Only minor changes on the pyrrolidine
Pyrrolidine
Pyrrolidine, also known as tetrahydropyrrole, is an organic compound with the molecular formula C4H9N. It is a cyclic secondary amine with a five-membered heterocycle containing four carbon atoms and one nitrogen atom...
ring can be tolerated since the good fit of the ring with the hydrophobic S1 pocket is very important for high affinity. Some trials have been made, e.g. by replacing the pyrrolidine
Pyrrolidine
Pyrrolidine, also known as tetrahydropyrrole, is an organic compound with the molecular formula C4H9N. It is a cyclic secondary amine with a five-membered heterocycle containing four carbon atoms and one nitrogen atom...
with a thiazoline
Thiazolidine
Thiazolidines are a class of heterocyclic organic compounds with a 5-membered saturated ring with a thioether group and an amine group in the 1 and 3 positions, respectively. It is a sulfur analogue of oxazolidine. The drug pioglitazone contains a thiazolidine ring. It is a drug usually indicated...
. That led to improved potency but also loss of chemical stability. Efforts to improve chemical stability often led to loss of specificity because of interactions with DPP-8
DPP8
Dipeptidyl peptidase 8 is an enzyme that in humans is encoded by the DPP8 gene.-References:NotesFurther reading...
and DPP-9
DPP9
Dipeptidyl peptidase 9 is an enzyme that in humans is encoded by the DPP9 gene.-Further reading:...
. These interactions have been connected with increased toxicity
Toxicity
Toxicity is the degree to which a substance can damage a living or non-living organisms. Toxicity can refer to the effect on a whole organism, such as an animal, bacterium, or plant, as well as the effect on a substructure of the organism, such as a cell or an organ , such as the liver...
and mortality
Mortality rate
Mortality rate is a measure of the number of deaths in a population, scaled to the size of that population, per unit time...
in animals. There are strict limitations in the P1 position and hardly any changes are tolerated, on the other hand a variety of changes can be made in the P2 position. In fact, substitution
Substitution
Substitution may refer to:- Sciences :* Substitution , a syntactic transformation on strings of symbols of a formal language* Substitution of variables* Substitution cipher, a method of encryption...
with quite big branched side chains, e.g. tert-butylglycin, normally increased activity and chemical stability, which could lead to longer-lasting inhibition of the DPP-4 enzyme. It has also been noted that biaryl-based side-chains can also give highly active inhibitors. It was originally believed that only lipophilic
Lipophilic
Lipophilicity, , refers to the ability of a chemical compound to dissolve in fats, oils, lipids, and non-polar solvents such as hexane or toluene. These non-polar solvents are themselves lipophilic — the axiom that like dissolves like generally holds true...
substitution would be tolerated. Now it is stated that also the substitution of polar
Chemical polarity
In chemistry, polarity refers to a separation of electric charge leading to a molecule or its chemical groups having an electric dipole or multipole moment. Polar molecules interact through dipole–dipole intermolecular forces and hydrogen bonds. Molecular polarity is dependent on the difference in...
negatively charged side-chains as well as hydrophilic substitution can lead to excellent inhibitory activity.
Chemical stability
Vildagliptin
Vildagliptin is an oral anti-hyperglycemic agent of the new dipeptidyl peptidase-4 inhibitor class of drugs...
and saxagliptin
Saxagliptin
Saxagliptin , previously identified as BMS-477118, is a new oral hypoglycemic of the new dipeptidyl peptidase-4 inhibitor class of drugs. Early development was solely by Bristol-Myers Squibb; in 2007 AstraZeneca joined with Bristol-Myers Squibb to co-develop the final compound and collaborate on...
, were created in this manner. K579 is a DPP-4 inhibitor discovered by researchers at Kyowa Hakko Kyogo. It had improved not only chemical stability but also a longer-lasting action. That long-lasting action was most likely due to slow dissociation of the enzyme-inhibitor complex and an active oxide
Oxide
An oxide is a chemical compound that contains at least one oxygen atom in its chemical formula. Metal oxides typically contain an anion of oxygen in the oxidation state of −2....
metabolite
Metabolite
Metabolites are the intermediates and products of metabolism. The term metabolite is usually restricted to small molecules. A primary metabolite is directly involved in normal growth, development, and reproduction. Alcohol is an example of a primary metabolite produced in large-scale by industrial...
that undergoes enterohepatic circulation. The discovery of the active oxide
Oxide
An oxide is a chemical compound that contains at least one oxygen atom in its chemical formula. Metal oxides typically contain an anion of oxygen in the oxidation state of −2....
was in fact a big breakthrough as it led to the development of vildagliptin
Vildagliptin
Vildagliptin is an oral anti-hyperglycemic agent of the new dipeptidyl peptidase-4 inhibitor class of drugs...
and saxagliptin
Saxagliptin
Saxagliptin , previously identified as BMS-477118, is a new oral hypoglycemic of the new dipeptidyl peptidase-4 inhibitor class of drugs. Early development was solely by Bristol-Myers Squibb; in 2007 AstraZeneca joined with Bristol-Myers Squibb to co-develop the final compound and collaborate on...
. One major problem in DPP-4 inhibitor stability is intramolecular
Intramolecular
Intramolecular in chemistry describes a process or characteristic limited within the structure of a single molecule, a property or phenomenon limited to the extent of a single molecule.- Examples :...
cyclisation. The precondition for the intramolecular
Intramolecular
Intramolecular in chemistry describes a process or characteristic limited within the structure of a single molecule, a property or phenomenon limited to the extent of a single molecule.- Examples :...
cyclisation is the conversion of the trans-rotamer, which is the DPP-4 binding rotamer(Figure 5). Thus, preventing this conversion will increase stability. This prevention was successful when incorporating an amide group into a ring, creating a compound that kept the DPP-4 inhibitory activity that, did not undergo the intramolecular
Intramolecular
Intramolecular in chemistry describes a process or characteristic limited within the structure of a single molecule, a property or phenomenon limited to the extent of a single molecule.- Examples :...
cyclisation and was even more selective over different DPP enzymes. It has also been reported that a cyanoazetidine in the P1 position and a β-amino acid in the P2 position increased stability.
Vildagliptin
Vildagliptin
Vildagliptin
Vildagliptin is an oral anti-hyperglycemic agent of the new dipeptidyl peptidase-4 inhibitor class of drugs...
(Galvus)(Figure 6) was first synthesized in May 1998 and was named after Edwin B. Villhauer. It was discovered when researchers at Novartis
Novartis
Novartis International AG is a multinational pharmaceutical company based in Basel, Switzerland, ranking number three in sales among the world-wide industry...
examined adamantyl derivative
Derivative
In calculus, a branch of mathematics, the derivative is a measure of how a function changes as its input changes. Loosely speaking, a derivative can be thought of as how much one quantity is changing in response to changes in some other quantity; for example, the derivative of the position of a...
s that had proven to be very potent
Potency (pharmacology)
In the field of pharmacology, potency is a measure of drug activity expressed in terms of the amount required to produce an effect of given intensity. A highly potent drug evokes a larger response at low concentrations, while a drug of lower potency evokes a small response at low concentrations...
. The adamantyl group worked as a steric bulk and slowed intramolecular
Intramolecular
Intramolecular in chemistry describes a process or characteristic limited within the structure of a single molecule, a property or phenomenon limited to the extent of a single molecule.- Examples :...
cyclization while increasing chemical stability. Furthermore, the primary metabolite
Metabolite
Metabolites are the intermediates and products of metabolism. The term metabolite is usually restricted to small molecules. A primary metabolite is directly involved in normal growth, development, and reproduction. Alcohol is an example of a primary metabolite produced in large-scale by industrial...
s were highly active. To avoid additional chiral center a hydroxylation
Hydroxylation
Hydroxylation is a chemical process that introduces a hydroxyl group into an organic compound. In biochemistry, hydroxylation reactions are often facilitated by enzymes called hydroxylases. Hydroxylation is the first step in the oxidative degradation of organic compounds in air...
at the adamantyl ring was carried out (Figure 5). The product, vildagliptin
Vildagliptin
Vildagliptin is an oral anti-hyperglycemic agent of the new dipeptidyl peptidase-4 inhibitor class of drugs...
, was even more stable, undergoing intramolecular
Intramolecular
Intramolecular in chemistry describes a process or characteristic limited within the structure of a single molecule, a property or phenomenon limited to the extent of a single molecule.- Examples :...
cyclisation 30-times slower, and having high DPP-4 inhibitory activity and longer-lasting pharmacodynamic effect.
Saxagliptin
Bristol-Myers Squibb
Bristol-Myers Squibb , often referred to as BMS, is a pharmaceutical company, headquartered in New York City. The company was formed in 1989, following the merger of its predecessors Bristol-Myers and the Squibb Corporation...
found that increased steric bulk of the N-terminal amino acid
Amino acid
Amino acids are molecules containing an amine group, a carboxylic acid group and a side-chain that varies between different amino acids. The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen...
side-chain led to increased stability. To additionally increase stability the trans-rotamer was stabilized with a cis-4,5-methano substitution of the pyrrolidine
Pyrrolidine
Pyrrolidine, also known as tetrahydropyrrole, is an organic compound with the molecular formula C4H9N. It is a cyclic secondary amine with a five-membered heterocycle containing four carbon atoms and one nitrogen atom...
ring, resulting in an intramolecular
Intramolecular
Intramolecular in chemistry describes a process or characteristic limited within the structure of a single molecule, a property or phenomenon limited to the extent of a single molecule.- Examples :...
van-der-Waals
Van der Waals force
In physical chemistry, the van der Waals force , named after Dutch scientist Johannes Diderik van der Waals, is the sum of the attractive or repulsive forces between molecules other than those due to covalent bonds or to the electrostatic interaction of ions with one another or with neutral...
interaction, thus preventing intramolecular
Intramolecular
Intramolecular in chemistry describes a process or characteristic limited within the structure of a single molecule, a property or phenomenon limited to the extent of a single molecule.- Examples :...
cyclisation. Because of that increased stability, the researchers continued their investigation on cis-4,5-methano cyanopyrrolidines and came across with a new adamantyl derivative
Derivative
In calculus, a branch of mathematics, the derivative is a measure of how a function changes as its input changes. Loosely speaking, a derivative can be thought of as how much one quantity is changing in response to changes in some other quantity; for example, the derivative of the position of a...
, which showed extraordinary ex vivo DPP-4 inhibition in rat plasma. Also noted, high microsomal turnover rate which indicated that the derivative was quickly converted to an active metabolite
Metabolite
Metabolites are the intermediates and products of metabolism. The term metabolite is usually restricted to small molecules. A primary metabolite is directly involved in normal growth, development, and reproduction. Alcohol is an example of a primary metabolite produced in large-scale by industrial...
. After hydroxylation
Hydroxylation
Hydroxylation is a chemical process that introduces a hydroxyl group into an organic compound. In biochemistry, hydroxylation reactions are often facilitated by enzymes called hydroxylases. Hydroxylation is the first step in the oxidative degradation of organic compounds in air...
on the adamantyl group they had a product with better microsomal stability and improved chemical stability. That product was named saxagliptin
Saxagliptin
Saxagliptin , previously identified as BMS-477118, is a new oral hypoglycemic of the new dipeptidyl peptidase-4 inhibitor class of drugs. Early development was solely by Bristol-Myers Squibb; in 2007 AstraZeneca joined with Bristol-Myers Squibb to co-develop the final compound and collaborate on...
(Onglyza)(Figure 6). In June 2008 AstraZeneca
AstraZeneca
AstraZeneca plc is a global pharmaceutical and biologics company headquartered in London, United Kingdom. It is the world's seventh-largest pharmaceutical company measured by revenues and has operations in over 100 countries...
and Bristol-Myers Squibb
Bristol-Myers Squibb
Bristol-Myers Squibb , often referred to as BMS, is a pharmaceutical company, headquartered in New York City. The company was formed in 1989, following the merger of its predecessors Bristol-Myers and the Squibb Corporation...
submitted a new drug application for Onglyza
Saxagliptin
Saxagliptin , previously identified as BMS-477118, is a new oral hypoglycemic of the new dipeptidyl peptidase-4 inhibitor class of drugs. Early development was solely by Bristol-Myers Squibb; in 2007 AstraZeneca joined with Bristol-Myers Squibb to co-develop the final compound and collaborate on...
in the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
and a marketing authorization application in Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
. Approval is still pending.
Denagliptin
Denagliptin (Figure 6) is an advanced compound
Chemical compound
A chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together...
with a branched side-chain at the P2 position, but also has (4S)-fluoro substitution on the cyanopyrrolidine ring. It is a well-known DPP-4 inhibitor developed by GlaxoSmithKline
GlaxoSmithKline
GlaxoSmithKline plc is a global pharmaceutical, biologics, vaccines and consumer healthcare company headquartered in London, United Kingdom...
(GSK). Biological evaluations have shown that the S-configuration of the amino acid
Amino acid
Amino acids are molecules containing an amine group, a carboxylic acid group and a side-chain that varies between different amino acids. The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen...
portion is essential for the inhibitory activity since the R-configuration showed reluctantly inhibition. These findings will be useful in future designs and synthesis of DPP-4 inhibitors. GSK
GlaxoSmithKline
GlaxoSmithKline plc is a global pharmaceutical, biologics, vaccines and consumer healthcare company headquartered in London, United Kingdom...
suspended phase-III clinical trials in October 2008.
Azetidine based compounds
Informations for this group of inhibitors are quite restircted. AzetidineAzetidine
Azetidine is a heterocyclic organic compound. It belongs to the class of four membered rings and it contains a nitrogen atom.-External links:* *...
-based DPP-4 inhibitors can roughly be grouped into three main subcategories; 2-cyanoazetidines, 3-fluoroazetidines, and 2-ketoazetidines. The most potent ketoazetidines and cyanoazetidines have large hydrophobic amino acid
Amino acid
Amino acids are molecules containing an amine group, a carboxylic acid group and a side-chain that varies between different amino acids. The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen...
groups bound to the azetidine
Azetidine
Azetidine is a heterocyclic organic compound. It belongs to the class of four membered rings and it contains a nitrogen atom.-External links:* *...
nitrogen
Nitrogen
Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...
and are active below 100nM.
Non-substrate-like inhibitors
Non-substrate-like inhibitorsEnzyme inhibitor
An enzyme inhibitor is a molecule that binds to enzymes and decreases their activity. Since blocking an enzyme's activity can kill a pathogen or correct a metabolic imbalance, many drugs are enzyme inhibitors. They are also used as herbicides and pesticides...
do not take after dipeptidic nature of DPP-4 substrates. They are non-covalent inhibitors and usually have an aromatic ring that occupies the S1-pocket, instead of the proline mimetic.
In 1999, Merck
Merck & Co.
Merck & Co., Inc. , also known as Merck Sharp & Dohme or MSD outside the United States and Canada, is one of the largest pharmaceutical companies in the world. The Merck headquarters is located in Whitehouse Station, New Jersey, an unincorporated area in Readington Township...
started a drug development program on DPP-4 inhibitors. When they started internal screening and medicinal chemistry
Medicinal chemistry
Medicinal chemistry and pharmaceutical chemistry are disciplines at the intersection of chemistry, especially synthetic organic chemistry, and pharmacology and various other biological specialties, where it is involved with design, chemical synthesis and development for market of pharmaceutical...
program, two DPP-4 inhibitors were already in clinical trials, isoleucyl thiazolidide (P32/38) and NVP-DPP728 from Novartis
Novartis
Novartis International AG is a multinational pharmaceutical company based in Basel, Switzerland, ranking number three in sales among the world-wide industry...
. Merck
Merck & Co.
Merck & Co., Inc. , also known as Merck Sharp & Dohme or MSD outside the United States and Canada, is one of the largest pharmaceutical companies in the world. The Merck headquarters is located in Whitehouse Station, New Jersey, an unincorporated area in Readington Township...
in-licensed L-threo-isoleucyl thiazolidide
Thiazolidine
Thiazolidines are a class of heterocyclic organic compounds with a 5-membered saturated ring with a thioether group and an amine group in the 1 and 3 positions, respectively. It is a sulfur analogue of oxazolidine. The drug pioglitazone contains a thiazolidine ring. It is a drug usually indicated...
and its allo stereoisomer. In animal studies, they found that both isomers had similar affinity for DPP-4, similar in vivo efficacy, similar pharmacokinetic and metabolic profiles. Nevertheless, the allo isomer was 10-fold more toxic. The researchers found out that this difference in toxicity
Toxicity
Toxicity is the degree to which a substance can damage a living or non-living organisms. Toxicity can refer to the effect on a whole organism, such as an animal, bacterium, or plant, as well as the effect on a substructure of the organism, such as a cell or an organ , such as the liver...
was due to the allo isomer's greater inhibition of DPP-8
DPP8
Dipeptidyl peptidase 8 is an enzyme that in humans is encoded by the DPP8 gene.-References:NotesFurther reading...
and DPP-9
DPP9
Dipeptidyl peptidase 9 is an enzyme that in humans is encoded by the DPP9 gene.-Further reading:...
but not because of selective DPP-4 inhibition. More research also supported that DPP-4 inhibition would not cause compromised immune function. Once this link between affinity for DPP-8/DPP-9 and toxicity
Toxicity
Toxicity is the degree to which a substance can damage a living or non-living organisms. Toxicity can refer to the effect on a whole organism, such as an animal, bacterium, or plant, as well as the effect on a substructure of the organism, such as a cell or an organ , such as the liver...
was discovered, Merck
Merck & Co.
Merck & Co., Inc. , also known as Merck Sharp & Dohme or MSD outside the United States and Canada, is one of the largest pharmaceutical companies in the world. The Merck headquarters is located in Whitehouse Station, New Jersey, an unincorporated area in Readington Township...
decided on identifying an inhibitor with more than a thousandfold affinity for DPP-4 over the other dipeptidases. For this purpose, they used positional scanning libraries. From scanning these libraries, the researchers discovered that both DPP-4 and DPP-8
DPP8
Dipeptidyl peptidase 8 is an enzyme that in humans is encoded by the DPP8 gene.-References:NotesFurther reading...
showed a strong preference for breaking down peptide
Peptide
Peptides are short polymers of amino acid monomers linked by peptide bonds. They are distinguished from proteins on the basis of size, typically containing less than 50 monomer units. The shortest peptides are dipeptides, consisting of two amino acids joined by a single peptide bond...
s with a proline
Proline
Proline is an α-amino acid, one of the twenty DNA-encoded amino acids. Its codons are CCU, CCC, CCA, and CCG. It is not an essential amino acid, which means that the human body can synthesize it. It is unique among the 20 protein-forming amino acids in that the α-amino group is secondary...
at the P1 position but they found a great difference at the P2 site; i.e., they found that acidic functionality at the P2 position could provide a greater affinity for DPP-4 over DPP-8
DPP8
Dipeptidyl peptidase 8 is an enzyme that in humans is encoded by the DPP8 gene.-References:NotesFurther reading...
. Merck
Merck & Co.
Merck & Co., Inc. , also known as Merck Sharp & Dohme or MSD outside the United States and Canada, is one of the largest pharmaceutical companies in the world. The Merck headquarters is located in Whitehouse Station, New Jersey, an unincorporated area in Readington Township...
kept up doing even more research and screening. They stopped working on compounds from the α-amino acid series related to isoleucyl thiazolidide
Thiazolidine
Thiazolidines are a class of heterocyclic organic compounds with a 5-membered saturated ring with a thioether group and an amine group in the 1 and 3 positions, respectively. It is a sulfur analogue of oxazolidine. The drug pioglitazone contains a thiazolidine ring. It is a drug usually indicated...
due to lack of selectivity but instead they discovered a very selective β-amino acid
Amino acid
Amino acids are molecules containing an amine group, a carboxylic acid group and a side-chain that varies between different amino acids. The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen...
piperazine
Piperazine
Piperazine is an organic compound that consists of a six-membered ring containing two opposing nitrogen atoms. Piperazine exists as small alkaline deliquescent crystals with a saline taste....
series through SAR
Structure-activity relationship
The structure–activity relationship is the relationship between the chemical or 3D structure of a molecule and its biological activity. The analysis of SAR enables the determination of the chemical groups responsible for evoking a target biological effect in the organism...
studies on two screening leads. When trying to stabilize the piperazine
Piperazine
Piperazine is an organic compound that consists of a six-membered ring containing two opposing nitrogen atoms. Piperazine exists as small alkaline deliquescent crystals with a saline taste....
moiety, a group of bicyclic derivatives were made, which led to the identification of a potent
Potent
Potent may refer to:*Vair#Potent for the heraldic fur*Warren Potent for the Australian Olympic medalist in shootingSee also:*Potency...
and selective triazolopiperazine series. Most of these analogs showed excellent pharmacokinetic properties in preclinical species. Optimization of these compounds finally led to the discovery of sitagliptin
Sitagliptin
Sitagliptin is an oral antihyperglycemic of the dipeptidyl peptidase-4 inhibitor class. It was developed, and is marketed, by Merck & Co...
.
Sitagliptin
Sitagliptin
Sitagliptin is an oral antihyperglycemic of the dipeptidyl peptidase-4 inhibitor class. It was developed, and is marketed, by Merck & Co...
(Januvia) has a novel structure with β-amino amide derivatives
Derivative (chemistry)
In chemistry, a derivative is a compound that is derived from a similar compound by some chemical or physical process. In the past it was also used to mean a compound that can be imagined to arise from another compound, if one atom is replaced with another atom or group of atoms, but modern...
(Figure 7). Since sitagliptin
Sitagliptin
Sitagliptin is an oral antihyperglycemic of the dipeptidyl peptidase-4 inhibitor class. It was developed, and is marketed, by Merck & Co...
has shown excellent selectivity and in vivo efficacy it urged researches to inspect the new structure of DPP-4 inhibitors with appended β-amino acid
Amino acid
Amino acids are molecules containing an amine group, a carboxylic acid group and a side-chain that varies between different amino acids. The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen...
moiety. Further studies are being developed to optimize these compounds for the treatment of diabetes.
In October 2006 Sitagliptin
Sitagliptin
Sitagliptin is an oral antihyperglycemic of the dipeptidyl peptidase-4 inhibitor class. It was developed, and is marketed, by Merck & Co...
became the first DPP-4 inhibitor that got FDA approval for the treatment of type 2 diabetes. Crystallographic structure of sitagliptin
Sitagliptin
Sitagliptin is an oral antihyperglycemic of the dipeptidyl peptidase-4 inhibitor class. It was developed, and is marketed, by Merck & Co...
along with molecular modeling has been used to continue the search for structurally diverse inhibitors. A new potent
Potent
Potent may refer to:*Vair#Potent for the heraldic fur*Warren Potent for the Australian Olympic medalist in shootingSee also:*Potency...
, selective and orally bioavailable DPP-4 inhibitor was discovered by replacing the central cyclohexylamine
Cyclohexylamine
Cyclohexylamine, also called hexahydroaniline, 1-aminocyclohexane, or aminohexahydrobenzene, is an organic chemical, an amine derived from cyclohexane. It is a clear to yellowish liquid with fishy odor, with melting point of −17.7 °C and boiling point 134.5 °C, miscible with water...
in sitagliptin
Sitagliptin
Sitagliptin is an oral antihyperglycemic of the dipeptidyl peptidase-4 inhibitor class. It was developed, and is marketed, by Merck & Co...
with 3-aminopiperidine. A 2-pyridyl substitution was the initial SAR breakthrough since that group plays a significant role in potency and selectivity for DPP-4.
It has been shown with an X-ray
X-ray
X-radiation is a form of electromagnetic radiation. X-rays have a wavelength in the range of 0.01 to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz and energies in the range 120 eV to 120 keV. They are shorter in wavelength than UV rays and longer than gamma...
crystallography
Crystallography
Crystallography is the experimental science of the arrangement of atoms in solids. The word "crystallography" derives from the Greek words crystallon = cold drop / frozen drop, with its meaning extending to all solids with some degree of transparency, and grapho = write.Before the development of...
how sitagliptin
Sitagliptin
Sitagliptin is an oral antihyperglycemic of the dipeptidyl peptidase-4 inhibitor class. It was developed, and is marketed, by Merck & Co...
binds to the DPP-4 complex:
1. The trifluorophenyl group occupies the S1-pocket
2. The trifluoromethyl group interacts with the side chains of residues Arg358 and Ser209.
3. The amino group forms a salt bridge
Salt bridge
A salt bridge, in chemistry, is a laboratory device used to connect the oxidation and reduction half-cells of a galvanic cell , a type of electrochemical cell...
with Tyr662 and the carboxylated groups of the two glutamate residues, Glu205 and Glu206.
4. The triazolopiperazine group collides with the phenyl group
Phenyl group
In organic chemistry, the phenyl group or phenyl ring is a cyclic group of atoms with the formula C6H5. Phenyl groups are closely related to benzene. Phenyl groups have six carbon atoms bonded together in a hexagonal planar ring, five of which are bonded to individual hydrogen atoms, with the...
of residue Phe357
Constrained phenylethylamine compounds
Researchers at Abbott LaboratoriesAbbott Laboratories
Abbott Laboratories is an American-based global, diversified pharmaceuticals and health care products company. It has 90,000 employees and operates in over 130 countries. The company headquarters are in Abbott Park, North Chicago, Illinois. The company was founded by Chicago physician, Dr....
identified three novel series of DPP-4 inhibitors using HTS. After more research and optimization ABT-341 was discovered (Figure 8). It is a potent and selective DPP-4 inhibitor with a 2D-structure very similar to sitagliptin
Sitagliptin
Sitagliptin is an oral antihyperglycemic of the dipeptidyl peptidase-4 inhibitor class. It was developed, and is marketed, by Merck & Co...
. However, the 3D-structure is quite different. ABT-341 also has a trifluorophenyl group that occupies the S1-pocket and the free amino group, but the two carbonyl groups are orientated 180° away from each other. ABT-341 is also believed to interact with the Tyr547, probably because of steric hindrance between the cyclohexenyl ring and the tyrosine
Tyrosine
Tyrosine or 4-hydroxyphenylalanine, is one of the 22 amino acids that are used by cells to synthesize proteins. Its codons are UAC and UAU. It is a non-essential amino acid with a polar side group...
side-chain.
Pyrrolidine compounds
The pyrrolidinePyrrolidine
Pyrrolidine, also known as tetrahydropyrrole, is an organic compound with the molecular formula C4H9N. It is a cyclic secondary amine with a five-membered heterocycle containing four carbon atoms and one nitrogen atom...
type of DPP-4 inhibitors was first discovered after HTS. Research showed that the pyrrolidine
Pyrrolidine
Pyrrolidine, also known as tetrahydropyrrole, is an organic compound with the molecular formula C4H9N. It is a cyclic secondary amine with a five-membered heterocycle containing four carbon atoms and one nitrogen atom...
rings were the part of the compounds that fit into the binding site
Binding site
In biochemistry, a binding site is a region on a protein, DNA, or RNA to which specific other molecules and ions—in this context collectively called ligands—form a chemical bond...
. Further development has led to fluoro substituted pyrrolidines that show superior activity, as well as pyrrolidine
Pyrrolidine
Pyrrolidine, also known as tetrahydropyrrole, is an organic compound with the molecular formula C4H9N. It is a cyclic secondary amine with a five-membered heterocycle containing four carbon atoms and one nitrogen atom...
s with fused cyclopropylrings that are highly active.
Xanthine-based compounds
This is a different class of inhibitors that were identified with HTS. Aromatic heterocyclic-based DPP-4 inhibitors have gained increased attention recently. The first patents describing xanthineXanthine
Xanthine , is a purine base found in most human body tissues and fluids and in other organisms. A number of stimulants are derived from xanthine, including caffeine and theobromine....
s (Figure 10) as DPP-4 inhibitors came from Boehringer-Ingelheim
Boehringer-Ingelheim
C.H. Boehringer Sohn AG & Ko. KG is the parent company of Boehringer Ingelheim, which was founded in 1885 by Albert Boehringer in Ingelheim am Rhein. The Boehringer Ingelheim group is one of the world's 20 leading pharmaceutical companies. Headquartered in Ingelheim, Germany, it operates globally...
(BI) and Novo Nordisk
Novo Nordisk
Novo Nordisk manufactures and markets pharmaceutical products and services. Created in 1989 through a merger of two Danish companies dating back to the 1920s, it has become one of the world's leading companies in diabetes care, where Novo Nordisk pursues research into pulmonary delivery systems;...
.
When xanthine
Xanthine
Xanthine , is a purine base found in most human body tissues and fluids and in other organisms. A number of stimulants are derived from xanthine, including caffeine and theobromine....
based DPP-4 inhibitors are compared with sitagliptin
Sitagliptin
Sitagliptin is an oral antihyperglycemic of the dipeptidyl peptidase-4 inhibitor class. It was developed, and is marketed, by Merck & Co...
and vildagliptin
Vildagliptin
Vildagliptin is an oral anti-hyperglycemic agent of the new dipeptidyl peptidase-4 inhibitor class of drugs...
it has shown a superior profile. Xanthines are believed to have higher potency
Potency (pharmacology)
In the field of pharmacology, potency is a measure of drug activity expressed in terms of the amount required to produce an effect of given intensity. A highly potent drug evokes a larger response at low concentrations, while a drug of lower potency evokes a small response at low concentrations...
, longer-lasting inhibition and longer-lasting improvement of glucose tolerance.
Alogliptin
Alogliptin
Alogliptin is an investigational anti-diabetic drug in the DPP-4 inhibitor class, being developed by Takeda Pharmaceutical Company. In January 2008, Takeda submitted a New Drug Application for alogliptin to the U.S. Food and Drug Administration, after positive results from Phase III clinical trials...
(Figure 9) is a novel DPP-4 inhibitor developed by the Takeda Pharmaceutical Company
Takeda Pharmaceutical Company
is the largest pharmaceutical company in Japan and Asia and a top 15 pharmaceutical company. The company has over 19,000 employees worldwide and achieved $15.7 billion USD in revenue during the 2008 fiscal year...
. Researchers hypothesized that a quinazolinone
Quinazolinone
Quinazolinone is a heterocyclic chemical compound. There are two structural isomers, 2-quinazolinone and 4-quinazolinone, with the 4-isomer being the more common.-Derivatives:...
based structure (Figure 9) would have the necessary groups to interact with the active site
Active site
In biology the active site is part of an enzyme where substrates bind and undergo a chemical reaction. The majority of enzymes are proteins but RNA enzymes called ribozymes also exist. The active site of an enzyme is usually found in a cleft or pocket that is lined by amino acid residues that...
on the DPP-4 complex
Complex
A complex is a whole that comprehends a number of intricate parts, especially one with interconnected or mutually related parts; for example, a complex of buildings.Complex may refer to:-Biology:...
. Quinazolinone
Quinazolinone
Quinazolinone is a heterocyclic chemical compound. There are two structural isomers, 2-quinazolinone and 4-quinazolinone, with the 4-isomer being the more common.-Derivatives:...
based compounds interacted effectively with the DPP-4 complex, but suffered from low metabolic half-life
Half-life
Half-life, abbreviated t½, is the period of time it takes for the amount of a substance undergoing decay to decrease by half. The name was originally used to describe a characteristic of unstable atoms , but it may apply to any quantity which follows a set-rate decay.The original term, dating to...
. It was found that when replacing the quinazolinone
Quinazolinone
Quinazolinone is a heterocyclic chemical compound. There are two structural isomers, 2-quinazolinone and 4-quinazolinone, with the 4-isomer being the more common.-Derivatives:...
with a pyrimidinedione, the metabolic stability was increased and the result was a potent
Potent
Potent may refer to:*Vair#Potent for the heraldic fur*Warren Potent for the Australian Olympic medalist in shootingSee also:*Potency...
, selective, bioavailable DPP-4 inhibitor named alogliptin
Alogliptin
Alogliptin is an investigational anti-diabetic drug in the DPP-4 inhibitor class, being developed by Takeda Pharmaceutical Company. In January 2008, Takeda submitted a New Drug Application for alogliptin to the U.S. Food and Drug Administration, after positive results from Phase III clinical trials...
. The quinazoline based compounds showed potent inhibition and excellent selectivity over related protease
Protease
A protease is any enzyme that conducts proteolysis, that is, begins protein catabolism by hydrolysis of the peptide bonds that link amino acids together in the polypeptide chain forming the protein....
, DPP-8
DPP8
Dipeptidyl peptidase 8 is an enzyme that in humans is encoded by the DPP8 gene.-References:NotesFurther reading...
. However, short metabolic half-life
Half-life
Half-life, abbreviated t½, is the period of time it takes for the amount of a substance undergoing decay to decrease by half. The name was originally used to describe a characteristic of unstable atoms , but it may apply to any quantity which follows a set-rate decay.The original term, dating to...
due to oxidation of the A-ring phenyl group was problematic. At first, the researchers tried to make a fluorinated derivative. The derivative showed improved metabolic stability and excellent inhibition of the DPP-4 enzyme. However, it was also found to inhibit CYP 450 3A4 and block the hERG
HERG
hERG is a gene that codes for a protein known as Kv11.1 potassium ion channel...
channel. The solution to this problem was to replace the quinazolinone
Quinazolinone
Quinazolinone is a heterocyclic chemical compound. There are two structural isomers, 2-quinazolinone and 4-quinazolinone, with the 4-isomer being the more common.-Derivatives:...
with other heterocycles, but the quinazolinone
Quinazolinone
Quinazolinone is a heterocyclic chemical compound. There are two structural isomers, 2-quinazolinone and 4-quinazolinone, with the 4-isomer being the more common.-Derivatives:...
could be replaced without any loss of DPP-4 inhibition. Alogliptin
Alogliptin
Alogliptin is an investigational anti-diabetic drug in the DPP-4 inhibitor class, being developed by Takeda Pharmaceutical Company. In January 2008, Takeda submitted a New Drug Application for alogliptin to the U.S. Food and Drug Administration, after positive results from Phase III clinical trials...
was discovered when quinazolinone was replaced with a pyrimidinedione
Pyrimidinedione
Pyrimidinediones are a class of chemical compounds characterized by a pyrimidine ring substituted with two carbonyl groups.Examples include naturally occurring metabolites:and drugs:* Fluorouracil* Idoxuridine* Primidone* Trifluridine-References:*...
. Alogliptin
Alogliptin
Alogliptin is an investigational anti-diabetic drug in the DPP-4 inhibitor class, being developed by Takeda Pharmaceutical Company. In January 2008, Takeda submitted a New Drug Application for alogliptin to the U.S. Food and Drug Administration, after positive results from Phase III clinical trials...
has shown excellent inhibition of DPP-4 and extraordinary selectivity, greater than 10.000 fold over the closely related serine proteases DPP-8
DPP8
Dipeptidyl peptidase 8 is an enzyme that in humans is encoded by the DPP8 gene.-References:NotesFurther reading...
and DPP-9
DPP9
Dipeptidyl peptidase 9 is an enzyme that in humans is encoded by the DPP9 gene.-Further reading:...
. Also, it does not inhibit the CYP 450 enzymes nor block the hERG
HERG
hERG is a gene that codes for a protein known as Kv11.1 potassium ion channel...
channel at concentration up to 30µM. Based on this data, alogliptin
Alogliptin
Alogliptin is an investigational anti-diabetic drug in the DPP-4 inhibitor class, being developed by Takeda Pharmaceutical Company. In January 2008, Takeda submitted a New Drug Application for alogliptin to the U.S. Food and Drug Administration, after positive results from Phase III clinical trials...
was chosen for preclinical evaluation. In January 2007 alogliptin
Alogliptin
Alogliptin is an investigational anti-diabetic drug in the DPP-4 inhibitor class, being developed by Takeda Pharmaceutical Company. In January 2008, Takeda submitted a New Drug Application for alogliptin to the U.S. Food and Drug Administration, after positive results from Phase III clinical trials...
was undergoing the phase III clinical trial
Clinical trial
Clinical trials are a set of procedures in medical research and drug development that are conducted to allow safety and efficacy data to be collected for health interventions...
and in October 2008 it was being reviewed by the U.S. Food and Drug Administration.
Linagliptin
Linagliptin
Linagliptin is a DPP-4 inhibitor developed by Boehringer Ingelheim for treatment of type II diabetes....
in May 2011. X-ray crystallography
X-ray crystallography
X-ray crystallography is a method of determining the arrangement of atoms within a crystal, in which a beam of X-rays strikes a crystal and causes the beam of light to spread into many specific directions. From the angles and intensities of these diffracted beams, a crystallographer can produce a...
has shown that that xanthine
Xanthine
Xanthine , is a purine base found in most human body tissues and fluids and in other organisms. A number of stimulants are derived from xanthine, including caffeine and theobromine....
type binds the DPP-4 complex in a different way than other inhibitors
Enzyme inhibitor
An enzyme inhibitor is a molecule that binds to enzymes and decreases their activity. Since blocking an enzyme's activity can kill a pathogen or correct a metabolic imbalance, many drugs are enzyme inhibitors. They are also used as herbicides and pesticides...
:
1. The amino group also interacts with the Glu205, Glu206 and Tyr662
2. The buty-2-nyl group occupies the S1-pocket
3. The uracil group undergoes a π-stacking interaction with the Tyr547 residue
4. The quinazoline group undergoes a π-stacking interaction with the Trp629 residue
Pharmacology
| Drug | Absorption | Bioavailability (%) | IC50 (nM) | Mean volume of distribution (L) | Protein binding (%) | Half-life (hours,100 mg dose) | Metabolism | Excretion |
|---|---|---|---|---|---|---|---|---|
| Sitagliptin | Rapidly absorbed with peak concentration at 1–4 hours | 87 | 18 | 198 | 38 | 12.4 | Small fraction undergoes hepatic metabolism via CYP 450 3A4 and 2C8 | Excreted in an unchanged form in the urine (79%) |
| Vildagliptin | Rapidly absorbed with peak concentration at 1–2 hours | 85 | 3 | 70.5 | 9.3 | 1.68 (once a day) and 2.54 (twice a day) | Hydrolysis resulting in a pharmacologically inactive metabolite. A fraction (22%) is also excreted unchanged by the kidneys | Excretion of the metabolite is carried out through urine (85%) and feces (15%) |
The pharmacokinetic properties of sitagliptin and vildagliptin appear unaffected by age, sex or BMI
Body mass index
The body mass index , or Quetelet index, is a heuristic proxy for human body fat based on an individual's weight and height. BMI does not actually measure the percentage of body fat. It was invented between 1830 and 1850 by the Belgian polymath Adolphe Quetelet during the course of developing...
. Clinical research
Clinical research
Clinical research is a branch of medical science that determines the safety and effectiveness of medications, devices, diagnostic products and treatment regimens intended for human use...
es have shown that sitagliptin
Sitagliptin
Sitagliptin is an oral antihyperglycemic of the dipeptidyl peptidase-4 inhibitor class. It was developed, and is marketed, by Merck & Co...
and vildagliptin
Vildagliptin
Vildagliptin is an oral anti-hyperglycemic agent of the new dipeptidyl peptidase-4 inhibitor class of drugs...
do not have the side effects
Adverse effect
In medicine, an adverse effect is a harmful and undesired effect resulting from a medication or other intervention such as surgery.An adverse effect may be termed a "side effect", when judged to be secondary to a main or therapeutic effect. If it results from an unsuitable or incorrect dosage or...
that tend to follow type 2 diabetes treatment, e.g. weight gain
Weight gain
Weight gain is an increase in body weight. This can be either an increase in muscle mass, fat deposits, or excess fluids such as water.-Description:...
and hyperglycemia
Hyperglycemia
Hyperglycemia or Hyperglycæmia, or high blood sugar, is a condition in which an excessive amount of glucose circulates in the blood plasma. This is generally a glucose level higher than 13.5mmol/l , but symptoms may not start to become noticeable until even higher values such as 15-20 mmol/l...
, but however, other side effects have been observed, including upper respiratory tract
Upper respiratory tract
The upper respiratory tract or upper airway primarily refers to the parts of the respiratory system lying outside of the thorax or above the sternal angle. Another definition commomly used in medicine is the airway above the glottis or vocal cords...
infection
Infection
An infection is the colonization of a host organism by parasite species. Infecting parasites seek to use the host's resources to reproduce, often resulting in disease...
s, sore throat
Sore throat
A sore throat or throat pain is a common physical symptom usually caused by acute pharyngitis, or throat inflammation, though it also occurs in a number of other situations, such as post trauma and in diphtheria. It can cause mild to extreme pain....
and diarrhea
Diarrhea
Diarrhea , also spelled diarrhoea, is the condition of having three or more loose or liquid bowel movements per day. It is a common cause of death in developing countries and the second most common cause of infant deaths worldwide. The loss of fluids through diarrhea can cause dehydration and...
.
See also
- Dipeptidyl peptidase-4Dipeptidyl peptidase-4Dipeptidyl peptidase-4 , also known as adenosine deaminase complexing protein 2 or CD26 is a protein that, in humans, is encoded by the DPP4 gene.-Function:...
- Dipeptidyl peptidase-4 inhibitorsDipeptidyl peptidase-4 inhibitorsInhibitors of dipeptidyl peptidase 4, also DPP-4 inhibitors or gliptins, are a class of oral hypoglycemics that block DPP-4. They can be used to treat diabetes mellitus type 2....
- VildagliptinVildagliptinVildagliptin is an oral anti-hyperglycemic agent of the new dipeptidyl peptidase-4 inhibitor class of drugs...
- SitagliptinSitagliptinSitagliptin is an oral antihyperglycemic of the dipeptidyl peptidase-4 inhibitor class. It was developed, and is marketed, by Merck & Co...
- SaxagliptinSaxagliptinSaxagliptin , previously identified as BMS-477118, is a new oral hypoglycemic of the new dipeptidyl peptidase-4 inhibitor class of drugs. Early development was solely by Bristol-Myers Squibb; in 2007 AstraZeneca joined with Bristol-Myers Squibb to co-develop the final compound and collaborate on...
- BerberineBerberineBerberine is a quaternary ammonium salt from the protoberberine group of isoquinoline alkaloids. It is found in such plants as Berberis Berberine is a quaternary ammonium salt from the protoberberine group of isoquinoline alkaloids. It is found in such plants as Berberis Berberine is a quaternary...