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.

A Review of the Potential Receptors of Migraine with a Special Emphasis on CGRP to Develop an Ideal Antimigraine Drug.

Migraine is a neurovascular syndrome associated with a unilateral, throbbing headache accompanied by nausea, vomiting and photo/phonophobia. Several proteins are involved in the etiopathogenesis of migraine headaches. The aim of the present review is to provide an insight into the various target proteins involved in migraine headaches pertaining to the development of a potential anti-migraine drug molecule. Proteins/receptors, such as serotonin (5-HT), Calcitonin Gene-Related Peptide (CGRP), Transient Receptor Potential Vanilloid 1 (TRPV1), cannabinoid, glutamate, opioid, and histamine receptors play various roles in migraine. The nature of the proteins, their types, binding partner membrane proteins and the consequences of the reactions produced have been discussed. The studies conducted on animals and humans with the above-mentioned target proteins/receptors and the results obtained have also been reviewed. Calcitonin Gene-Related Peptide (CGRP), a G protein-coupled receptor (GPCR), significantly contributes to the progression of migraine. CGRP antagonist inhibits the release of CGRP from trigeminal neurons of the trigeminal ganglion. Based on the study results, the present review suggests that the inhibition of the CGRP receptor might be a successful way to treat migraine headaches. Currently, researchers across the world are focusing their attention towards the development of novel molecules to treat migraine headaches by targeting the CGRP receptor, which can be attributed to its specificity among the several proteins involved in migraine.

Azepino-indazoles as calcitonin gene-related peptide (CGRP) receptor antagonists.

Calcitonin gene-related peptide (CGRP) receptor antagonists have been shown clinically to be effective treatments for migraine. Zavegepant (BHV-3500, BMS-742413) is a high affinity antagonist of the CGRP receptor (hCGRP Ki = 0.023 nM) that has demonstrated efficacy in the acute treatment of migraine with intranasal delivery in a Phase 2/3 trial, despite showing low oral bioavailability in rats (FPO = 1.7%). Using zavegepant as a template, we sought to improve oral bioavailability through a series of azepinones which were designed in an attempt to reduce the number of rotatable bonds. These efforts led to the discovery of compound 21 which was able to mostly maintain high affinity binding (hCGRP Ki = 0.100 nM) and in vivo efficacy in the marmoset facial blood flow assay, while greatly improving oral bioavailability (rat FPO = 17%).

Rimegepant: First Approval.

The orally disintegrating tablet (ODT) formulation of rimegepant (NURTEC ODT®) is a small molecule, highly-selective, calcitonin gene-related peptide antagonist that was developed by Biohaven Pharmaceutical Holding Company Ltd as an acute treatment for migraine. A conventional tablet formulation of the drug is being investigated for the acute treatment (under FDA review in the USA) and prevention of migraine and the treatment of refractory trigeminal neuralgia. In February 2020, rimegepant ODT received its first global approval in the USA for the acute treatment of migraine (± aura) in adults. This article summarizes the milestones in the development of rimegepant leading to its first global approval for acute treatment of migraine (± aura) in adults.

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.

Therapeutic novelties in migraine: new drugs, new hope?

BACKGROUND: In the past decade, migraine research has identified novel drug targets. In this review, we discuss recent data on emerging anti-migraine therapies. MAIN BODY: The development of ditans, gepants and anti-calcitonin gene-related peptide monoclonal antibodies for the treatment of migraine is one of the greatest advances in the migraine field. Lasmiditan, rimegepant and ubrogepant will extend our therapeutic armamentarium for managing acute migraine attacks when triptans are not effective or contraindicated due to cardiovascular disorders. The monoclonal antibodies are migraine specific prophylactic drugs with high responder rates and favorable adverse event profiles. Furthermore, they offer convenient treatment regimens of 4- or 12-week intervals. CONCLUSION: Collectively, novel migraine therapies represent a major progress in migraine treatment and will undoubtedly transform headache medicine.

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.