Design, synthesis and structure–activity relationship studies of novel free fatty acid receptor 1 agonists bearing amide linker

Synthetic GPR40/FFAR1 agonists: An exhaustive survey on the most recent chemical classes and their structure-activity relationships

Free fatty acid receptor 1 (FFAR1 or GPR40) is a potential target for treating type 2 diabetes mellitus (T2DM) and related disorders that have been extensively researched for many years. GPR40/FFAR1 is a promising anti-diabetic target because it can activate insulin, promoting glucose metabolism. It controls T2DM by regulating glucose levels in the body through two separate mechanisms: glucose-stimulated insulin secretion and incretin production. In the last few years, various synthetic GPR40/FFAR1 agonists have been discovered that fall under several chemical classes, viz. phenylpropionic acid, phenoxyacetic acid, and dihydrobenzofuran acetic acid. However, only a few synthetic agonists have entered clinical trials due to various shortcomings like poor efficacy, low lipophilicity and toxicity issues. As a result, pharmaceutical firms and research institutions are interested in developing synthetic GPR40/FFAR1 agonists with superior effectiveness, lipophilicity, and safety profiles. This review encompasses the most recent research on synthetic GPR40/FFAR1 agonists, including their chemical classes, design strategies and structure-activity relationships. Additionally, we have emphasised the structural characteristics of the most potent GPR40/FFAR1 agonists from each chemical class of synthetic derivatives and analysed their chemico-biological interactions. This work will hopefully pave the way for developing more potent and selective synthetic GPR40/FFAR1 agonists for treating T2DM and related disorders.

Visible-Light-Controlled Histone Deacetylase Inhibitors for Targeted Cancer Therapy

The lack of selectivity of anticancer drugs limits current chemotherapy. Light-activatable drugs, whose activity can be precisely controlled with external light, could provide a more localized action of the drugs in the tumor, thus decreasing side effects and increasing efficacy. Herein, we introduce a series of photoswitchable azobenzene histone deacetylase inhibitors (HDACis) whose activity can be controlled by external visible light. Initial HDACis isomerized under ultraviolet light and were up to >50-fold more active under illumination than in the dark in enzyme assays. These were then optimized toward compounds responding to more permeable and less harmful green light by introducing o-halogen atoms into the azobenzene. Selected compounds decreased cell viability only under illumination in four different cancer cell lines. Overall, we present photoswitchable HDACis with optimized activation wavelengths, which inhibit enzyme activity and cell viability only upon illumination with visible light, contributing to the still limited toolbox of photoswitchable anticancer drugs.

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.

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).

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.

Quercetin/oleic acid-based G-protein-coupled receptor 40 ligands as new insulin secretion modulators

Aim: Management of Type 2 diabetes mellitus by diet is achievable at the early stage of the disease; patients usually underestimate this approach and an appropriate drug therapy is required. Results: Starting from quercetin and oleic acid, that have effect on insulin secretion, a small set of hybrid molecules was synthesized. Insulin secretion was evaluated in both in vitro and ex vivo models.  AV1  was able to enhance insulin secretion dose dependently, behaving as a conceivable agonist of G-protein-coupled receptor 40. Conclusion: AV1 represents an interesting tool that interacts with G-protein-coupled receptor 40. Further studies will be carried out to evaluate the exact binding mode, and also to enlarge the library of these antidiabetic agents.

[Formula: see text]