Discovery of novel pyrrole-based scaffold as potent and orally bioavailable free fatty acid receptor 1 agonists for the treatment of type 2 diabetes

Pyrrole: A Decisive Scaffold for the Development of Therapeutic Agents and Structure-Activity Relationship

An overview of pyrroles as distinct scaffolds with therapeutic potential and the significance of pyrrole derivatives for drug development are provided in this article. It lists instances of naturally occurring pyrrole-containing compounds and describes the sources of pyrroles in nature, including plants and microbes. It also explains the many conventional and modern synthetic methods used to produce pyrroles. The key topics are the biological characteristics, pharmacological behavior, and functional alterations displayed by pyrrole derivatives. It also details how pyrroles are used to treat infectious diseases. It describes infectious disorders resistant to standard treatments and discusses the function of compounds containing pyrroles in combating infectious diseases. Furthermore, the review covers the uses of pyrrole derivatives in treating non-infectious diseases and resistance mechanisms in non-infectious illnesses like cancer, diabetes, and Alzheimer's and Parkinson's diseases. The important discoveries and probable avenues for pyrrole research are finally summarized, along with their significance for medicinal chemists and drug development. A reference from the last two decades is included in this review.

Potential Therapeutic Targets for the Management of Diabetes Mellitus Type 2

Diabetes is one of the lifelong chronic metabolic diseases which is prevalent globally. There is a continuous rise in the number of people suffering from this disease with time. It is characterized by hyperglycemia, which leads to severe damage to the body's system, such as blood vessels and nerves. Diabetes occurs due to the dysfunction of pancreatic β -cell which leads to the reduction in the production of insulin or body cells unable to use insulin produce efficiently. As per the data shared International diabetes federation (IDF), there are around 415 million affected by this disease worldwide. There are a number of hit targets available that can be focused on treating diabetes. There are many drugs available and still under development for the treatment of type 2 diabetes. Inhibition of gluconeogenesis, lipolysis, fatty acid oxidation, and glucokinase activator is emerging targets for type 2 diabetes treatment. Diabetes management can be supplemented with drug intervention for obesity. The antidiabetic drug sale is the second-largest in the world, trailing only that of cancer. The future of managing diabetes will be guided by research on various novel targets and the development of various therapeutic leads, such as GLP-1 agonists, DPP-IV inhibitors, and SGLT2 inhibitors that have recently completed their different phases of clinical trials. Among these therapeutic targets associated with type 2 diabetes, this review focused on some common therapeutic targets for developing novel drug candidates of the newer generation with better safety and efficacy.

Synthesis and Biological Evaluation of 12-Aryl-11-hydroxy-5,6-dihydropyrrolo[2″,1″:3',4']pyrazino[1',2':1,5]pyrrolo[2,3-d]pyridazine-8(9H)-one Derivatives as Potential Cytotoxic Agents

In the present paper, a facile and efficient synthetic procedure has been applied to obtain dihydrodipyrrolo[1,2-a:2',1'-c]pyrazine-2,3-dicarboxylates (5a-s), which have subsequently gone through the cyclization in the presence of hydrazine hydrate to afford 12-aryl-11-hydroxy-5,6-dihydropyrrolo[2″,1″:3',4']pyrazino[1',2':1,5]pyrrolo[2,3-d]pyridazine-8(9H)-ones (7a-q). The molecular structures of these novel compounds were extensively examined through the analysis of spectroscopic data in combination with X-ray crystallography techniques. Following that, the in vitro cytotoxic activities of all derivatives against three human cancer cell lines (Panc-1, PC3, and MDA-MB-231) were comprehensively evaluated alongside the assessment on normal human dermal fibroblast (HDF) cells using the MTT assay. Among the compounds, the 3-nitrophenyl derivative (7m) from the second series showed the best antiproliferative activity against all tested cell lines, particularly against Panc-1 cell line, (IC50 = 12.54 μM), being nearly twice as potent as the standard drug etoposide. The induction of apoptosis and sub-G1 cell cycle arrest in Panc-1 cancer cells by compound 7m was confirmed through further assessment. Moreover, the inhibition of kinases and the induction of cellular apoptosis by compound 7m in Panc-1 cancer cells were validated using the Western blotting assay.

Design, synthesis, and biological evaluation of novel dual FFA1 and PPARδ agonists possessing phenoxyacetic acid scaffold

The free fatty acid receptor 1 (FFA1/GPR40) and peroxisome proliferator-activated receptor δ (PPARδ) have been widely considered as promising targets for type 2 diabetes mellitus (T2DM) due to their respective roles in promoting insulin secretion and improving insulin sensitivity. Hence, the dual FFA1/PPARδ agonists may exert synergistic effects by simultaneously activating FFA1 and PPARδ. The present study performed systematic exploration around previously reported FFA1 agonist 2-(2-fluoro-4-((2'-methyl-4'-(3-(methylsulfonyl)propoxy)-[1,1'-biphenyl]-3-yl)methoxy)phenoxy)acetic acid (lead compound), leading to the identification of a novel dual FFA1/PPARδ agonist 2-(2-fluoro-4-((3-(6-methoxynaphthalen-2-yl)benzyl)oxy)phenoxy)acetic acid (the optimal compound), which displayed high selectivity over PPARα and PPARγ. In addition, the docking study provided us with detailed binding modes of the optimal compound in FFA1 and PPARδ. Furthermore, the optimal compound exhibited greater glucose-lowering effects than lead compound, which might attribute to its synergistic effects by simultaneously modulating insulin secretion and resistance. Moreover, the optimal compound has an acceptable safety profile in the acute toxicity study at a high dose of 500 mg/kg Therefore, our results provided a novel dual FFA1/PPARδ agonist with excellent glucose-lowering effects in vivo.

In Silico Searching for Alternative Lead Compounds to Treat Type 2 Diabetes through a QSAR and Molecular Dynamics Study

Free fatty acid receptor 1 (FFA1) stimulates insulin secretion in pancreatic β-cells. An advantage of therapies that target FFA1 is their reduced risk of hypoglycemia relative to common type 2 diabetes treatments. In this work, quantitative structure-activity relationship (QSAR) approach was used to construct models to identify possible FFA1 agonists by applying four different machine-learning algorithms. The best model (M2) meets the Tropsha's test requirements and has the statistics parameters R2 = 0.843, Q2CV = 0.785, and Q2ext = 0.855. Also, coverage of 100% of the test set based on the applicability domain analysis was obtained. Furthermore, a deep analysis based on the ADME predictions, molecular docking, and molecular dynamics simulations was performed. The lipophilicity and the residue interactions were used as relevant criteria for selecting a candidate from the screening of the DiaNat and DrugBank databases. Finally, the FDA-approved drugs bilastine, bromfenac, and fenofibric acid are suggested as potential and lead FFA1 agonists.

Heterocyclic compounds as a magic bullet for diabetes mellitus: a review

Diabetes mellitus (DM) is a major metabolic disorder due to hyperglycemia, which is increasing all over the world. From the last two decades, the use of synthetic agents has risen due to their major involvement in curing of chronic diseases including DM. The core skeleton of drugs has been studied such as thiazolidinone, azole, chalcone, pyrrole and pyrimidine along with their derivatives. Diabetics assays have been performed in consideration of different enzymes such as α-glycosidase, α-amylase, and α-galactosidase against acarbose standard drug. The studied moieties were depicted in both models: in vivo as well as in vitro. Molecular docking of the studied compounds as antidiabetic molecules was performed with the help of Auto Dock and molecular operating environment (MOE) software. Amino acid residues Asp349, Arg312, Arg439, Asn241, Val303, Glu304, Phe158, His103, Lys422 and Thr207 that are present on the active sites of diabetic related enzymes showed interactions with ligand molecules. In this review data were organized for the synthesis of heterocyclic compounds through various routes along with their antidiabetic potential, and further studies such as pharmacokinetic and toxicology studies should be executed before going for clinical trials.

Diabetes mellitus (DM) is a major metabolic disorder due to hyperglycemia, which is increasing all over the world.

Recent Updates on Free Fatty Acid Receptor 1 (GPR-40) Agonists for the Treatment of Type 2 Diabetes Mellitus

BACKGROUND

The global incidence of type 2 diabetes mellitus (T2DM) has enthused the development of new antidiabetic targets with low toxicity and long-term stability. In this respect, free fatty acid receptor 1 (FFAR1), which is also recognized as a G protein-coupled receptor 40 (GPR40), is a novel target for the treatment of T2DM. FFAR1/GPR40 has a high level of expression in β-cells of the pancreas, and the requirement of glucose for stimulating insulin release results in immense stimulation to utilise this target in the medication of T2DM.

METHODS

The data used for this review is based on the search of several scienctific databases as well as various patent databases. The main search terms used were free fatty acid receptor 1, FFAR1, FFAR1 agonists, diabetes mellitus, G protein-coupled receptor 40 (GPR40), GPR40 agonists, GPR40 ligands, type 2 diabetes mellitus and T2DM.

RESULTS

The present review article gives a brief overview of FFAR1, its role in T2DM, recent developments in small molecule FFAR1 (GPR40) agonists reported till now, compounds of natural/plant origin, recent patents published in the last few years, mechanism of FFAR1 activation by the agonists, and clinical status of the FFAR1/GPR40 agonists.

CONCLUSION

The agonists of FFAR1/GRP40 showed considerable potential for the therapeutic control of T2DM. Most of the small molecule FFAR1/GPR40 agonists developed were aryl alkanoic acid derivatives (such as phenylpropionic acids, phenylacetic acids, phenoxyacetic acids, and benzofuran acetic acid derivatives) and thiazolidinediones. Some natural/plant-derived compounds, including fatty acids, sesquiterpenes, phenolic compounds, anthocyanins, isoquinoline, and indole alkaloids, were also reported as potent FFAR1 agonists. The clinical investigations of the FFAR1 agonists demonstrated their probable role in the improvement of glucose control. Though, there are some problems still to be resolved in this field as some FFAR1 agonists terminated in the late phase of clinical studies due to "hepatotoxicity." Currently, PBI-4050 is under clinical investigation by Prometic. Further investigation of pharmacophore scaffolds for FFAR1 full agonists as well as multitargeted modulators and corresponding clinical investigations will be anticipated, which can open up new directions in this area.

Design, synthesis and biological evaluation of novel FFA1/GPR40 agonists: New breakthrough in an old scaffold

Based on an old phenoxyacetic acid scaffold, CPU014 (compound 14) has been identified as a superior agonist by comprehensive exploration of structure-activity relationship. In vitro toxicity study suggested that CPU014 has lower risk of hepatotoxicity than TAK-875. During acute toxicity study (5-500 mg/kg), a favorable therapeutic window of CPU014 was observed by evaluation of plasma profiles and liver slices. Moreover, CPU014 promotes insulin secretion in a glucose-dependent manner, while no GLP-1 secretion has been enhanced. Other than good pharmacokinetic properties, CPU014 significantly improved glucose tolerance both in normal and diabetic models without the risk of hypoglycemia. These subversive findings provided a safer candidate CPU014, which is currently in preclinical study to assess its potential for the treatment of diabetes.

Structure-based design of free fatty acid receptor 1 agonists bearing non-biphenyl scaffold

The free fatty acid receptor 1 (FFA1) enhances the glucose-stimulated insulin secretion without the risk of hypoglycemia. However, most of FFA1 agonists have a common biphenyl moiety, leading to a relative deprivation in structure types. Herein, we describe the exploration of non-biphenyl scaffold based on the co-crystal structure of FFA1 to increase additional interactions with the lateral residues, which led to the identification of lead compounds 3 and 9. In induced-fit docking study, compound 3 forms an edge-on interaction with Trp150 by slightly rotating the indole ring of Trp150, and compound 9 has additional hydrogen bond and δ-π interactions with Leu135, which demonstrated the feasibility of our design strategy. Moreover, lead compounds 3 and 9 revealed improved polar surface area compared to GW9508, and have considerable hypoglycemic effects in mice. This structure-based study might inspire us to design more promising FFA1 agonists by increasing additional interactions with the residues outside of binding pocket.

Improving metabolic stability with deuterium: The discovery of HWL-066, a potent and long-acting free fatty acid receptor 1 agonists

The free fatty acid receptor 1 (FFA1) is a potential target due to its function in enhancing of glucose-stimulated insulin secretion. The FFA1 agonist GW9508 has great potential for the treatment of type 2 diabetes mellitus, but it has been suffering from high plasma clearance probably because the phenylpropanoic acid is vulnerable to β-oxidation. To identify orally available analog without influence on the unique pharmacological mechanism of GW9508, we tried to interdict the metabolically labile group by incorporating two deuterium atoms at the α-position of phenylpropionic acid affording compound 4 (HWL-066). As expected, HWL-066 revealed a lower clearance (CL = 0.23 L^-1  hr^-1  kg^-1 ), higher maximum concentration (C_max  = 5907.47 μg/L), and longer half-life (T_1/2  = 3.50 hr), resulting in a 2.8-fold higher exposure than GW9508. Moreover, the glucose-lowering effect of HWL-066 was far better than that of GW9508 and comparable with TAK-875. Different from glibenclamide, no side-effect of hypoglycemia was observed in mice after oral administrating HWL-066 (80 mg/kg).

Current anti-diabetic agents and their molecular targets: A review

Diabetes mellitus is a medical condition characterized by the body's loss of control over blood sugar. The frequency of diagnosed cases and consequential increases in medical costs makes it a rapidly growing chronic disease that threatens human health worldwide. In addition, its unnerving statistical projections are perilous to both the economy of the nation and man's life expectancy. Type-I and type-II diabetes are the two clinical forms of diabetes mellitus. Type-II diabetes mellitus (T2DM) is illustrated by the abnormality of glucose homeostasis in the body, resulting in hyperglycemia. Although significant research attention has been devoted to the development of diabetes regimens, which demonstrates success in lowering blood glucose levels, their efficacies are unsustainable due to undesirable side effects such as weight gain and hypoglycemia. Over the years, heterocyclic scaffolds have been the basis of anti-diabetic chemotherapies; hence, in this review we consolidate the use of bioactive scaffolds, which have been evaluated for their biological response as inhibitors against their respective anti-diabetic molecular targets over the past five years (2012-2017). Our investigation reveals a diverse target set which includes; protein tyrosine phosphatase 1 B (PTP1B), dipeptidly peptidase-4 (DPP-4), free fatty acid receptors 1 (FFAR1), G protein-coupled receptors (GPCR), peroxisome proliferator activated receptor-γ (PPARγ), sodium glucose co-transporter-2 (SGLT2), α-glucosidase, aldose reductase, glycogen phosphorylase (GP), fructose-1,6-bisphosphatase (FBPase), glucagon receptor (GCGr) and phosphoenolpyruvate carboxykinase (PEPCK). This review offers a medium on which future drug design and development toward diabetes management may be modelled (i.e. optimization via structural derivatization), as many of the drug candidates highlighted show promise as an effective anti-diabetic chemotherapy.

Structure-based optimization of free fatty acid receptor 1 agonists bearing thiazole scaffold

The free fatty acid receptor 1 (FFA1) plays an important role in amplifying insulin secretion in a glucose dependent manner. We have previously reported a series of FFA1 agonists with thiazole scaffold exemplified by compound 1, and identified a small hydrophobic subpocket partially occupied by the methyl group of compound 1. Herein, we describe further structure optimization to better fit the small hydrophobic subpocket by replacing the small methyl group with other hydrophobic substituents. All of these efforts resulted in the identification of compound 6, a potent FFA1 agonist (EC₅₀ = 39.7 nM) with desired ligand efficiency (0.24) and ligand lipophilicity efficiency (4.7). Moreover, lead compound 6 exhibited a greater potential for decreasing the hyperglycemia levels than compound 1 during an oral glucose tolerance test. In summary, compound 6 is a promising FFA1 agonist for further investigation, and the structure-based study promoted our understanding for the binding pocket of FFA1.

Free fatty acid receptor agonists for the treatment of type 2 diabetes: drugs in preclinical to phase II clinical development

INTRODUCTION

The alarming prevalence of type 2 diabetes mellitus (T2DM) stimulated the exploitation of new antidiabetic drugs with extended durability and enhanced safety. In this regard, the free fatty acid receptor 1 (FFA1) and FFA4 have emerged as attractive targets in the last decade. FFA1 has prominent advantages in promoting insulin and incretin secretion while FFA4 shows great potential in incretin secretion, insulin sensitization and anti-inflammatory effects.

AREA COVERED

Herein, the authors focus specifically on FFA1 and FFA4 agonists in clinical trials and preclinical development. LY2922470, P11187 and SHR0534 are currently active in clinical trials while the CNX-011-67, SAR1, DS-1558 and BMS-986118 are in preclinical phase. The information for this review is retrieved from Integrity, Scifinder, Espacenet and clinicaltrials.gov databases.

EXPERT OPINION

Current proof-of-concept in clinical trials suggests that FFA1 agonists have a significant improvement for T2DM without the risk of hypoglycemia. However, there are still several challenging problems including the mechanism of the receptor and the efficacy and safety of the ligands.

Ligands at Free Fatty Acid Receptor 1 (GPR40)

FFA1 is a G protein-coupled receptor activated by medium- to long-chain fatty acids. FFA1 plays important roles in various physiological processes such as insulin secretion and energy metabolism. FFA1 expressed on pancreatic β-cells and intestine contributes to insulin and incretin secretion, respectively. These physiological functions of FFA1 are interesting as an attractive drug target for type II diabetes and metabolic disorders. A number of synthetic FFA1 ligands have been developed and they have contributed to our current understanding of the physiological and pathophysiological functions of FFA1 both in in vitro and in vivo studies. In addition, these synthetic ligands also provided information on the structure-activity relationships of FFA1 ligands. Further, FFA1 protein crystallized with one of the high affinity agonist leads provided useful insights for the development of more effective ligands. Among FFA1 ligands, several compounds have been further investigated in the clinical trials. Thus, FFA1 ligands have great potential as drug candidates. In this section, recent progress about FFA1 ligands and the possibility of their clinical use are described.