Pyrazole Agonist of the Apelin Receptor Improves Symptoms of Metabolic Syndrome in Mice

Signaling Modulation via Minimal C-Terminal Modifications of Apelin-13

Apelin is an endogenous peptide that is involved in many diseases such as cardiovascular diseases, obesity, and cancer, which has made it an attractive target for drug discovery. Herein, we explore the penultimate and final sequence positions of [Pyr1]-apelin-13 (Ape13) via C-terminal N α-alkylated amide bonds and the introduction of positive charges, potentially targeting the allosteric sodium pocket, by assessing the binding affinity and signaling profiles at the apelin receptor (APJ). Synthetic analogues modified within this segment of Ape13 showed high affinity (K i 0.12-0.17 nM vs Ape13 K i 0.7 nM), potent Gαi1 activation (EC50 Gαi1 0.4-0.9 nM vs Ape13 EC50 1.1 nM), partial agonist behavior disfavoring β-arrestin 2 recruitment for positively charged ligands (e.g., 49 (SBL-AP-058), EC50 β-arr2 275 nM, E max 54%) and high plasma stability for N-alkyl ligands (t 1/2 > 7 h vs Ape13 t 1/2 0.5 h). Combining the benefits of the N α-alkylated amide bond with the guanidino substitution in a constrained ligand led to 63 (SBL-AP-049), which displayed increased plasma stability (t 1/2 5.3 h) and strong reduction of β-arrestin 2 signaling with partial maximal efficacy (EC50 β-arr 864 nM, E max 48%), significantly reducing the hypotensive effect in vivo.

Synthesis and characterization of an orally bioavailable small molecule agonist of the apelin receptor

The apelin receptor (APJ) is a target for cardiovascular indications. Previously, we had identified a novel pyrazole-based agonist 1 ((S)-N-(1-(cyclobutylamino)-1-oxo-5-(piperidin-1-yl)pentan-3-yl)-1-cyclopentyl-5-(2,6-dimethoxyphenyl)-1H-pyrazole-3-carboxamide hydrochloride) of this GPCR. Systematic modification of 1 was performed to produce compounds with improved potency and ADME properties. Orally bioavailable compound 47 with favorable agonist potency (Ca2+EC50 = 24 nM, cAMPi EC50 = 6.5 nM) and pharmacokinetic properties (clearance ∼20 mL/min/kg in rats) was identified. This compound has vastly reduced brain penetration and is devoid of significant off-target liability. In summary, a potent and selective APJ agonist suitable for in vivo studies of APJ in peripheral tissues after oral administration has been identified.

Scaffold Hopping Strategy to Identify Prostanoid EP4 Receptor Antagonists for Cancer Immunotherapy

Cancer cells can effectively suppress the natural immune response in humans, and prostaglandin E₂ (PGE₂) is a key mediator in the development of tumor cell resistance to immunotherapy. As a major contributor to PGE₂-elicited immunosuppressive activity, the EP4 receptor promotes tumor development and progression in the tumor microenvironment, and the development of selective and potent EP4 receptor antagonists should have promising potential for tumor immunotherapy. Aiming at improving the drug-like properties, a series of 4,7-dihydro-5H-thieno[2,3-c]pyran derivatives were designed and synthesized through a scaffold hopping strategy. The most promising compound 47 exhibited good EP4 antagonistic activity and excellent subtype selectivity, as well as favorable drug-like properties. It effectively suppressed the expression of multiple immunosuppression-related genes in macrophages. Meanwhile, oral administration of compound 47, alone or in combination with anti-PD-1 antibody, significantly enhanced the antitumor immune response and inhibited tumor growth in the mouse CT26 colon carcinoma model.

Neuropeptide B/W receptor 1 peptidomimetic agonists: Structure-activity relationships and plasma stability

Neuropeptides B and W (NPB and NPW) are endogenous ligands of the Neuropeptide B/W Receptor 1 (NPBWR1) which has been implicated in a wide range of functions including regulation of pain and energy homeostasis. There is currently little information on the structure-activity relationships (SAR) of these two neuropeptides. In a quest to develop stable and potent NPBWR1 peptidomimetic agonists, we performed systematic SAR by truncation, Alanine/Glycine and d-amino acid scans, and replacement with unnatural amino acids. Evaluation in the NPBWR1 calcium assay revealed that the C-terminal GRAAGLL and N-terminal WYK regions constitute the two-epitope pharmacophore for NPBWR1 agonism. Replacement of the N-terminal Trp with its desaminoTrp residue resulted in compound 30 which exhibited nanomolar potency comparable to the endogenous NPB at NPBWR1 (Calcium assay: EC₅₀ = 8 nM vs. 13 nM, cAMP assay: 2.7 nM vs 3.5 nM) and enhanced metabolic stability against rat plasma (39.1 min vs. 11.9 min).

The Role of Apelin-APJ System in Diabetes and Obesity

Nowadays, diabetes and obesity are two main health-threatening metabolic disorders in the world, which increase the risk for many chronic diseases. Apelin, a peptide hormone, exerts its effect by binding with angiotensin II protein J receptor (APJ) and is considered to be linked with diabetes and obesity. Apelin and its receptor are widely present in the body and are involved in many physiological processes, such as glucose and lipid metabolism, homeostasis, endocrine response to stress, and angiogenesis. In this review, we summarize the literatures on the role of the Apelin-APJ system in diabetes and obesity for a better understanding of the mechanism and function of apelin and its receptor in the pathophysiology of diseases that may contribute to the development of new therapies.