Calcitonin gene-related peptide (CGRP), a potent dilator of cerebral and dural vasculature, is known to be elevated in plasma and cerebral spinal fluid during migraine attacks. Selective blockade of the CGRP receptor offers the promise of controlling migraine headache more effectively and without the side-effects associated with the use of triptans. Our efforts to develop a novel, peptide-based CGRP antagonist focused on the C-terminal portion of the peptide which is known to bind the receptor but lack agonist properties. Extensive SAR studies of the C-terminal CGRP (27-37) region identified a novel cyclic structure: Bz-Val-Tyr-cyclo[Cys-Thr-Asp-Val-Gly-Pro-Phe-Cys]-Phe-NH2 (23) with a kb value of 0.126 nM against the cloned human CGRP receptor. Additional SAR studies directed at enhancement of potency and improvement of physicochemical properties yielded a series of analogs with kb values in the 0.05-0.10 nM range. Copyright (C) 2011 European Peptide Society and John Wiley & Sons, Ltd.

The recent emergence of obesity as a major health threat in the industrialized world has intensified the search for novel and effective pharmacologic treatment. The proopiomelanocortin (POMC)-melanocortin 4 receptor (MC4R) axis has been shown to regulate food intake and energy homeostasis and is considered among the most promising antiobesity targets. Our initial efforts in this area have focused on affinity and selectivity directed optimization of the native beta-MSH(5-22) sequence and resulted in the discovery of a potent MC4R agonist: Ac-Tyr-Arg-[Cys-Glu-His-D-Phe-Arg-Trp-Cys]-NH(2) (10). Subcutaneous administration of this peptide produced an excellent in vivo efficacy in reducing food intake and increasing fat metabolism. Additionally, suppression of food intake was observed in wild type but not in MC4R deficient mice, suggesting that the effects observed in the wild type mice were mediated through MC4R signaling. Subsequent optimization efforts led to the identification of a novel series of disulfide constrained hexapeptides as exemplified by Ac-[hCys-His-D-Phe-Arg-Trp-Cys]-NH(2) (100). These cyclic hexapeptides showed a further improved potency in binding MC4R and an enhanced selectivity over MC1R. At a dose of 0.07 mg/kg analog 102 reduced food intake by 38% and increased fat utilization by 58% in rats. These cyclic peptides provide novel and enhanced reagents for the elucidation of melanocortin receptors biology and may find applications in the treatment of obesity and related metabolic disorders.

Extensive structure–activity relationship studies utilizing a β-MSH-derived cyclic nonapeptide, Ac-Tyr-Arg-[Cys-Glu-His-d-Phe-Arg-Trp-Cys]-NH2 (3), led to identification of a series of novel MC-4R selective disulfide-constrained hexapeptide analogs including Ac-[hCys-His-d-Phe-Arg-Trp-Cys]-NH2 (12). The structural modifications associated with profound influence on MC-4R potency and selectivity were ring size, ring conformation, and the aromatic substitution of the d-Phe7. These cyclic peptide analogs provide novel and enhanced reagents for use in the elucidation of melanocortin-4 receptor-related physiology, and may additionally find application in the treatment of obesity and related metabolic disorders.

A series of novel, disulfide-constrained human β-melanocyte stimulating hormone (β-MSH)-derived peptides were optimized for in vitro melanocortin-4 receptor (MC-4R) binding affinity, agonist efficacy, and selectivity. The most promising of these, analogue 18, was further studied in vivo using chronic rat food intake and body weight models.

A general method was developed for the synthesis of serine or threonine containing cyclic peptides utilizing the beta-hydroxyl side-chain of these residues as an anchor point to Wang resin. The peptide chain was assembled by conventional Fmoc/tBu solid-phase chemistry followed by palladium catalyzed exposure of the allyl protected C-terminus and on-resin cyclization. The cyclic heptapeptide stylostatin 1 was prepared to demonstrate the utility of this technique. (C) 2003 Elsevier Ltd. All rights reserved.

Since its initial discovery and characterization as the native growth hormone secretagogue [1], ghrelin GSS(n-octanoyl)FLSPEHQRVQQRKESKKPPAKLQPR has stimulated extensive studies directed toward clarifying its role in feeding, energy balance and growth hormone release [2–5]. A flexible and efficient synthetic procedure was required to produce sufficient quantities of human ghrelin in order to conduct structure-activity studies related to the native peptide. To this end we carried out four separate solid-phase Fmoc/tBu based synthetic protocols which differed with respect to the method of incorporation of the Ser3-octanoyl moiety. The methods were evaluated for yield and purity of final product. In addition, we optimized a procedure for the esterification of the Ser3 side chain with respect to stoichiometry and time course.

A mild N-alkylation method has been developed for the synthesis of N-alkylated pyridiniumcarboxylic acids, using Ag2O-H2O catalysis to enhance the low-reactivity of pyridinecarboxylic acids. Two approaches were undertaken for the synthesis of a series of GnRH antagonists containing pyridinium moieties at the side chain: (1) incorporation of Npy-alkylated D-pyridylalanine during solid phase peptide chain assembly, and (2) coupling of the N-alkylated pyridinium-carboxylic acid to the resin-bound ε-amino group of a D-lysine on a solid support.

About 25 conformationally constrained antagonists of LHRH have been synthesized in order to gain some information about the bioactive conformation of antagonists. The constraints include various C-methyl residues, N-methyl groups, prolines and the 6-7 lactam. The antagonists were evaluated in the rat antiovulatory assay, in a pituitary cell membrane binding assay and by NMR. The results will be discussed and a model of the bioactive conformation proposed.