Calcitonin gene-related peptide (CGRP) receptor antagonists: Heterocyclic modification of a novel azepinone lead.

In our efforts to identify orally bioavailable CGRP receptor antagonists, we previously discovered a novel series of orally available azepinone derivatives that unfortunately also exhibited the unwanted property of potent time-dependent human CYP3A4 inhibition. Through heterocyclic replacement of the indazole ring, we discovered a series of heterocycle derivatives as high-affinity CGRP receptor antagonists. Some of them showed reasonable oral exposures, and the imidazolone derivatives that showed good oral exposure also exhibited substantially reduced time-dependent CYP3A4 inhibition. Several compounds showed strong in vivo efficacy in our marmoset facial blood flow assay with up to 87% inhibition of CGRP-induced activity. However, oral bioavailability generally remained low, emphasizing the challenges we and others encountered in discovering clinical development candidates for this difficult Class B GPCR target.

Structure-Based Drug Discovery of N-((R)-3-(7-Methyl-1H-indazol-5-yl)-1-oxo-1-(((S)-1-oxo-3-(piperidin-4-yl)-1-(4-(pyridin-4-yl)piperazin-1-yl)propan-2-yl)amino)propan-2-yl)-2'-oxo-1',2'-dihydrospiro[piperidine-4,4'-pyrido[2,3-d][1,3]oxazine]-1-carboxamide (HTL22562): A Calcitonin Gene-Related Peptide Receptor Antagonist for Acute Treatment of Migraine.

Structure-based drug design enabled the discovery of 8, HTL22562, a calcitonin gene-related peptide (CGRP) receptor antagonist. The structure of 8 complexed with the CGRP receptor was determined at a 1.6 Å resolution. Compound 8 is a highly potent, selective, metabolically stable, and soluble compound suitable for a range of administration routes that have the potential to provide rapid systemic exposures with resultant high levels of receptor coverage (e.g., subcutaneous). The low lipophilicity coupled with a low anticipated clinically efficacious plasma exposure for migraine also suggests a reduced potential for hepatotoxicity. These properties have led to 8 being selected as a clinical candidate for acute treatment of migraine.

A CGRP receptor antagonist peptide formulated for nasal administration to treat migraine.

OBJECTIVES: To investigate the formulation of the peptide-based antagonist (34 Pro,35 Phe)CGRP27-37 , of the human calcitonin gene-related peptide (CGRP) receptor as a potential nasally delivered migraine treatment. METHODS: Peptide sequences were prepared using automated methods and purified by preparative HPLC. Their structure and stability were determined by LC-MS. Antagonist potency was assessed by measuring CGRP-stimulated cAMP accumulation in SK-N-MC, cells and in CHO cells overexpressing the human CGRP receptor. In vivo activity was tested in plasma protein extravasation (PPE) studies using Evans blue dye accumulation. Peptide-containing chitosan microparticles were prepared by spray drying. KEY FINDINGS: (34 Pro,35 Phe)CGRP27-37 exhibited a 10-fold increased affinity compared to αCGRP27-37 . Administration of (34 Pro,35 Phe)CGRP27-37 to mice led to a significant decrease in CGRP-induced PPE confirming antagonistic properties in vivo. There was no degradation of (34 Pro,35 Phe)CGRP27-37 and no loss of antagonist potency during formulation and release from chitosan microparticles. CONCLUSIONS: (34 Pro,35 Phe)CGRP27-37 is a potent CGRP receptor antagonist both in vitro and in vivo, and it can be formulated as a dry powder with no loss of activity indicating its potential as a nasally formulated anti-migraine medicine.

Synthesis of a CGRP Receptor Antagonist via an Asymmetric Synthesis of 3-Fluoro-4-aminopiperidine.

A practical and efficient enantioselective synthesis of the calcitonin gene-related peptide receptor antagonist 1 has been developed. The key structural component of the active pharmaceutical ingredient is a syn-1,2-amino-fluoropiperidine 4. Two approaches were developed to synthesize this important pharmacophore. Initially, Ru-catalyzed asymmetric hydrogenation of fluoride-substituted enamide 8 enabled the synthesis of sufficient quantities of compound 1 to support early preclinical studies. Subsequently, a novel, cost-effective route to this intermediate was developed utilizing a dynamic kinetic asymmetric transamination of ketone 9. This synthesis also features a robust Ullmann coupling to install a bis-aryl ether using a soluble Cu(I) catalyst. Finally, an enzymatic desymmetrization of meso-diester 7 was exploited for the construction of the γ-lactam moiety in 1.

Solid-Phase Thiol-Ene Lipidation of Peptides for the Synthesis of a Potent CGRP Receptor Antagonist.

We report a new method herein coined SP-CLipPA (solid-phase cysteine lipidation of a peptide or amino acid) for the synthesis of mono-S-lipidated peptides. This technique utilizes thiol-ene chemistry for conjugation of a vinyl ester to a free thiol of a semiprotected, resin-bound peptide. Advantages of SP-CLipPA include: ease of handling, conversions of up to 91 %, by-product removal by simple filtration, and a single purification step. Additionally, the desired lipidated products show high chromatographic separation from impurities, thus facilitating RP-HPLC purification. To showcase the utility of SP-CLipPA, we synthesized a potent calcitonin gene-related peptide (CGRP) receptor antagonist peptide in excellent yield and purity. This peptide, selected from a series of lipidated analogues of CGRP8-37 and CGRP7-37 , has potential for the treatment of migraine.