Rational design of dual peptides targeting ghrelin and Y2 receptors to regulate food intake and body weight

Design of Xenopus GLP-1-Based Long-Acting Dual GLP-1/Y2 Receptor Agonists

GLP-1 receptor (GLP-1R) and neuropeptide Y₂ receptor (Y₂R) dual agonists have shown great potential to treat obesity and type 2 diabetes (T2DM). We developed a multitarget strategy to design monomeric agonists based on Xenopus GLP-1 (xGLP-1) and PYY_3-36 analogues with dual activation activities on GLP-1R and Y₂R. A novel peptide, 6q, was obtained via stepwise structure optimization and in vitro receptor screens. In db/db and diet-induced obesity (DIO) mice, 6q produced greater effects on long-term glycemic control and body weight reduction than GLP-1R and Y₂R monoagonist counterparts. Notably, in high-fat diet-induced nonalcoholic steatohepatitis (NASH) mice, 6q treatment significantly reduced hepatic triglyceride and total cholesterol levels and reversed hepatic steatosis compared with GLP-1R monoagonist (liraglutide) treatment. Collectively, these data support the therapeutic potential of our GLP-1R/Y₂R dual agonist 6q as a novel antidiabetic, antiobesity, and antisteatotic agent.

Advances in the Development of Nonpeptide Small Molecules Targeting Ghrelin Receptor

Ghrelin is an octanoylated peptide acting by the activation of the growth hormone secretagogue receptor, namely, GHS-R1a. The involvement of ghrelin in several physiological processes, including stimulation of food intake, gastric emptying, body energy balance, glucose homeostasis, reduction of insulin secretion, and lipogenesis validates the considerable interest in GHS-R1a as a promising target for the treatment of numerous disorders. Over the years, several GHS-R1a ligands have been identified and some of them have been extensively studied in clinical trials. The recently resolved structures of GHS-R1a bound to ghrelin or potent ligands have provided useful information for the design of new GHS-R1a drugs. This perspective is focused on the development of recent nonpeptide small molecules acting as GHS-R1a agonists, antagonists, and inverse agonists, bearing classical or new molecular scaffolds, as well as on radiolabeled GHS-R1a ligands developed for imaging. Moreover, the pharmacological effects of the most studied ligands have been discussed.

Development of a ghrelin receptor inverse agonist for positron emission tomography

Imaging of Ghrelin receptors in vivo provides unique potential to gain deeper understanding on Ghrelin and its receptors in health and disease, in particular, in cancer. Ghrelin, an octanoylated 28-mer peptide hormone activates the constitutively active growth hormone secretagogue receptor type 1a (GHS-R1a) with nanomolar activity. We developed novel compounds, derived from the potent inverse agonist K-(D-1-Nal)-FwLL-NH₂ but structurally varied by lysine conjugation with 1,4,7-triazacyclononane,1-glutaric acid-4,7-acetic acid (NODAGA), palmitic acid and/or diethylene glycol (PEG2) to allow radiolabeling and improve pharmacokinetics, respectively. All compounds were tested for receptor binding, potency and efficacy in vitro, for biodistribution and -kinetics in rats and in preclinical prostate cancer models on mice. Radiolabeling with Cu-64 and Ga-68 was successfully achieved. The Cu-64- or Ga-68-NODAGA-NH-K-K-(D-1-NaI)-F-w-L-L-NH₂ radiotracer were specifically accumulated by the GHS-R1a in xenotransplanted human prostate tumor models (PC-3, DU-145) in mice. The tumors were clearly delineated by PET. The radiotracer uptake was also partially blocked by K-(D-1-Nal)-FwLL-NH₂ in stomach and thyroid. The presence of the GHS-R1a was also confirmed by immunohistology. In the arterial rat blood plasma, only the original compounds were found. The Cu-64 or Ga-68-NODAGA-NH-K-K-(D-1-NaI)-F-w-L-L-NH₂ radiolabeled inverse agonists turned out to be potent and safe. Due to their easy synthesis, high affinity, medium potency, metabolic stability, and the suitable pharmacokinetic profiles, they are excellent tools for imaging and quantitation of GHS-R1a expression in normal and cancer tissues by PET. These compounds can be used as novel biomarkers of the Ghrelin system in precision medicine.

Instant kit preparation of 68Ga-radiopharmaceuticals via the hybrid chelator DATA: clinical translation of [68Ga]Ga-DATA-TOC

Purpose

The widespread use of ⁶⁸Ga for positron emission tomography (PET) relies on the development of radiopharmaceutical precursors that can be radiolabelled and dispensed in a simple, quick, and convenient manner. The DATA (6-amino-1,4-diazapine-triacetate) scaffold represents a novel hybrid chelator architecture possessing both cyclic and acyclic character that may allow for facile access to ⁶⁸Ga-labelled tracers in the clinic. We report the first bifunctional DATA chelator conjugated to [Tyr³]octreotide (TOC), a somatostatin subtype 2 receptor (SST₂)-targeting vector for imaging and functional characterisation of SSTR₂ expressing tumours.

Methods

The radiopharmaceutical precursor, DATA-TOC, was synthesised as previously described and used to complex ^natGa(III) and ⁶⁸Ga(III). Competition binding assays of [^natGa]Ga-DATA-TOC or [^natGa]Ga-DOTA-TOC against [¹²⁵I-Tyr²⁵]LTT-SS28 were conducted in membranes of HEK293 cells transfected to stably express one of the hSST_2,3,5 receptor subtypes (HEK293-hSST_2/3/5 cells). First in vivo studies were performed in female NMRI-nude mice bearing SST₂-positive mouse phaeochromocytoma mCherry (MPC-mCherry) tumours to compare the in vivo SST₂-specific tumour-targeting of [⁶⁸Ga]Ga-DATA-TOC and its overall pharmacokinetics versus the [⁶⁸Ga]Ga-DOTA-TOC reference. A direct comparison of [⁶⁸Ga]Ga-DATA-TOC with the well-established PET radiotracer [⁶⁸Ga]Ga-DOTA-TOC was additionally performed in a 46-year-old male patient with a well-differentiated NET (neuroendocrine tumour), representing the first in human administration of [⁶⁸Ga]Ga-DATA-TOC.

Results

DATA-TOC was labelled with ⁶⁸Ga with a radiolabelling efficiency of > 95% in less than 10 min at ambient temperature. A molar activity up to 35 MBq/nmol was achieved. The hSST₂-affinities of [^natGa]Ga-DATA-TOC and [^natGa]Ga-DOTA-TOC were found similar with only sub-nanomolar differences in the respective IC₅₀ values. In mice, [⁶⁸Ga]Ga-DATA-TOC was able to visualise the tumour lesions, showing standardised uptake values (SUVs) similar to [⁶⁸Ga]Ga-DOTA-TOC. Direct comparison of the two PET tracers in a NET patient revealed very similar tumour uptake for the two ⁶⁸Ga-radiotracers, but with a higher tumour-to-liver contrast for [⁶⁸Ga]Ga-DATA-TOC.

Conclusion

[⁶⁸Ga]Ga-DATA-TOC was prepared, to a quality appropriate for in vivo use, following a highly efficient kit type process. Furthermore, the novel radiopharmaceutical was comparable or better than [⁶⁸Ga]Ga-DOTA-TOC in all preclinical tests, achieving a higher tumour-to-liver contrast in a NET-patient. The results illustrate the potential of the DATA-chelator to facilitate the access to and preparation of ⁶⁸Ga-radiotracers in a routine clinical radiopharmacy setting.

Electronic supplementary material

The online version of this article (10.1186/s13550-019-0516-7) contains supplementary material, which is available to authorized users.

Control of Food Intake by Gastrointestinal Peptides: Mechanisms of Action and Possible Modulation in the Treatment of Obesity

This review focuses on the control of appetite by food intake-regulatory peptides secreted from the gastrointestinal tract, namely cholecystokinin, glucagon-like peptide 1, peptide YY, ghrelin, and the recently discovered nesfatin-1 via the gut-brain axis. Additionally, we describe the impact of external factors such as intake of different nutrients or stress on the secretion of gastrointestinal peptides. Finally, we highlight possible conservative—physical activity and pharmacotherapy—treatment strategies for obesity as well as surgical techniques such as deep brain stimulation and bariatric surgery also altering these peptidergic pathways.

Rational, computer-enabled peptide drug design: principles, methods, applications and future directions

Peptides provide promising templates for developing drugs to occupy a middle space between small molecules and antibodies and for targeting 'undruggable' intracellular protein-protein interactions. Importantly, rational or in cerebro design, especially when coupled with validated in silico tools, can be used to efficiently explore chemical space and identify islands of 'drug-like' peptides to satisfy diverse drug discovery program objectives. Here, we consider the underlying principles of and recent advances in rational, computer-enabled peptide drug design. In particular, we consider the impact of basic physicochemical properties, potency and ADME/Tox opportunities and challenges, and recently developed computational tools for enabling rational peptide drug design. Key principles and practices are spotlighted by recent case studies. We close with a hypothetical future case study.