Structure-activity relationship (SAR) studies on substituted N-(pyridin-3-yl)-2-amino-isonicotinamides as highly potent and selective glycogen synthase kinase-3 (GSK-3) inhibitors.

In our continuing efforts to explore structure-activity relationships around the novel class of potent, isonicotinamide-based GSK3 inhibitors described in our previous report, we extensively explored structural variations around both 4/5-pyridine substitutions and the amide group. Some analogs were found to have greatly improved pTau lowering potency while retaining high kinase selectivity. In contrast to previous active compounds 1a-c, a close analog 3h did not show in vivo efficacy in a triple-transgenic mouse Alzheimer's disease model. In general, these 2­pyridinyl amide derivatives were prone to amidase mediated hydrolysis in mouse plasma.

Rimegepant, an Oral Calcitonin Gene-Related Peptide Receptor Antagonist, for Migraine.

BACKGROUND: Calcitonin gene-related peptide receptor has been implicated in the pathogenesis of migraine. Rimegepant is an orally administered, small-molecule, calcitonin gene-related peptide receptor antagonist that may be effective in acute migraine treatment. METHODS: In a multicenter, double-blind, phase 3 trial, we randomly assigned adults with at least a 1-year history of migraine and two to eight migraine attacks of moderate or severe intensity per month to receive rimegepant orally at a dose of 75 mg or matching placebo for the treatment of a single migraine attack. The primary end points were freedom from pain and freedom from the most bothersome symptom (other than pain) identified by the patient, both of which were assessed 2 hours after the dose of rimegepant or placebo was administered. RESULTS: A total of 1186 patients were randomly assigned to receive rimegepant (594 patients) or placebo (592 patients); of these, 537 patients in the rimegepant group and 535 patients in the placebo group could be evaluated for efficacy. The overall mean age of the patients evaluated for efficacy was 40.6 years, and 88.7% were women. In a modified intention-to-treat analysis, the percentage of patients who were pain-free 2 hours after receiving the dose was 19.6% in the rimegepant group and 12.0% in the placebo group (absolute difference, 7.6 percentage points; 95% confidence interval [CI], 3.3 to 11.9; P<0.001). The percentage of patients who were free from their most bothersome symptom 2 hours after the dose was 37.6% in the rimegepant group and 25.2% in the placebo group (absolute difference, 12.4 percentage points; 95% CI, 6.9 to 17.9; P<0.001). The most common adverse events were nausea and urinary tract infection. CONCLUSIONS: Treatment of a migraine attack with the oral calcitonin gene-related peptide receptor antagonist rimegepant resulted in a higher percentage of patients who were free of pain and free from their most bothersome symptom than placebo. (Funded by Biohaven Pharmaceuticals; ClinicalTrials.gov number, NCT03237845.).

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.

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%).

Asymmetric Synthesis of the Major Metabolite of a Calcitonin Gene-Related Peptide Receptor Antagonist and Mechanism of Epoxide Hydrogenolysis.

An asymmetric synthesis of the major metabolite of the calcitonin gene-related peptide recepotor antagonist BMS-846372 is presented. The variously substituted cyclohepta[b]pyridine ring system represents an underexplored ring system and showed some unexpected chemistry. Reactivities of epoxide and ketone functional groups on the cycloheptane ring were extensively controlled by a remote bulky TIPS group. The rate difference of the hydrogenolysis between two diastereomeric epoxide intermediates shed some light on the mechanism of epoxide hydrogenolysis, and further, deuterium labeling studies revealed more mechanistic details on this well-known chemical transformation for the first time.

Synthesis and SAR of calcitonin gene-related peptide (CGRP) antagonists containing substituted aryl-piperazines and piperidines.

Calcitonin gene-related peptide (CGRP) is a potent neuropeptide implicated in the pathophysiology of migraine. In the course of seeking CGRP antagonists with improved oral bioavailability, metabolic stability, and pharmacokinetic properties, lower molecular weight, structurally simpler piperidine and piperazine analogs of BMS-694153 were prepared. Several were found to have nM binding affinity in vitro. The synthesis and SAR of these substituted piperidine and piperazine CGRP antagonists are discussed.

Discovery of new acylaminopyridines as GSK-3 inhibitors by a structure guided in-depth exploration of chemical space around a pyrrolopyridinone core.

Glycogen synthase kinase-3 (GSK-3) has been proposed to play a crucial role in the pathogenesis of many diseases including cancer, stroke, bipolar disorders, diabetes and neurodegenerative diseases. GSK-3 inhibition has been a major area of pharmaceutical interest over the last two decades. A plethora of reports appeared recently on selective inhibitors and their co-crystal structures in GSK-3ß. We identified several series of promising new GSK-3ß inhibitors from a coherent design around a pyrrolopyridinone core structure. A systematic exploration of the chemical space around the central spacer led to potent single digit and sub-nanomolar GSK-3ß inhibitors. When dosed orally in a transgenic mouse model of Alzheimer's disease (AD), an exemplary compound showed significant lowering of Tau phosphorylation at one of the GSK-3 phosphorylating sites, Ser396. X-ray crystallography greatly aided in validating the binding hypotheses.

Serendipitous oxidation product of BIBN4096BS: a potent CGRP receptor antagonist.

An oxidation product (5) formed during the synthesis of BIBN-4096BS (1) was found to be a potent CGRP antagonist (IC50=0.11nM). While 5 was found to be ten-fold less potent than 1, another analog 8 with lower molecular weight containing the oxidized fragment demonstrated twenty-fold higher activity than its parent 7. Alternative conditions which preclude the formation of the oxidation product are described. The activities of 1, 5, 7 and 8 in functional cAMP assay are also discussed.

Preparation of imidazoles as potent calcitonin gene-related peptide (CGRP) antagonists.

Several new potent CGRP receptor antagonists have been prepared in which the amide bond of lead compound 1 has been replaced by bioisosteric imidazole moieties. Substitution at N-1 of the imidazole was optimized to afford compounds with comparable potency to that of lead 1. Conformational restraint of the imidazole to form tetrahydroimidazo[1,5-a]pyrazine 43 gave substantially improved permeability.

Discovery of (R)-N-(3-(7-methyl-1H-indazol-5-yl)-1-(4-(1-methylpiperidin-4-yl)-1-oxopropan-2-yl)-4-(2-oxo-1,2-dihydroquinolin-3-yl)piperidine-1-carboxamide (BMS-742413): a potent human CGRP antagonist with superior safety profile for the treatment of migraine through intranasal delivery.

Calcitonin gene-related peptide (CGRP) receptor antagonists have been shown to be efficacious as abortive migraine therapeutics with the absence of cardiovascular liabilities that are associated with triptans. Herein, we report the discovery of a highly potent CGRP receptor antagonist, BMS-742413, with the potential to provide rapid onset of action through intranasal delivery. The compound displays excellent aqueous solubility, oxidative stability, and toxicological profile. BMS-742413 has good intranasal bioavailability in the rabbit and shows a robust, dose-dependent inhibition of CGRP-induced increases in marmoset facial blood flow.

The synthesis and SAR of calcitonin gene-related peptide (CGRP) receptor antagonists derived from tyrosine surrogates. Part 2.

Various substituted indazole and benzoxazolone amino acids were investigated as d-tyrosine surrogates in highly potent CGRP receptor antagonists. Compound 3, derived from the 7-methylindazole core, afforded a 30-fold increase in CGRP binding potency compared with its unsubstituted indazole analog 1. When dosed at 0.03mg/kg SC, compound 2 (a racemic mixture of 3 and its (S)-enantiomer) demonstrated robust inhibition of CGRP-induced increases in mamoset facial blood flow up to 105min. The compound possesses a favorable predictive in vitro toxicology profile, and good aqueous solubility. When dosed as a nasal spray in rabbits, 3 was rapidly absorbed and showed good intranasal bioavailability (42%).

Design, Structure-Activity Relationships, and In Vivo Evaluation of Potent and Brain-Penetrant Imidazo[1,2-b]pyridazines as Glycogen Synthase Kinase-3ß (GSK-3ß) Inhibitors.

Glycogen synthase kinase-3 (GSK-3) is a serine/threonine kinase that regulates numerous cellular processes, including metabolism, proliferation, and cell survival. Due to its multifaceted role, GSK-3 has been implicated in a variety of diseases, including Alzheimer's disease, type 2 diabetes, cancer, and mood disorders. GSK-3ß has been linked to the formation of the neurofibrillary tangles associated with Alzheimer's disease that arise from the hyperphosphorylation of tau protein. The design and synthesis of a series of imidazo[1,2-b]pyridazine derivatives that were evaluated as GSK-3ß inhibitors are described herein. Structure-activity relationship studies led to the identification of potent GSK-3ß inhibitors. In vivo studies with 47 in a triple-transgenic mouse Alzheimer's disease model showed that this compound is a brain-penetrant, orally bioavailable GSK-3ß inhibitor that significantly lowered levels of phosphorylated tau.

Discovery of 2-(Anilino)pyrimidine-4-carboxamides as Highly Potent, Selective, and Orally Active Glycogen Synthase Kinase-3 (GSK-3) Inhibitors.

Glycogen synthase kinase-3 (GSK-3) is a serine/threonine kinase that serves as an important regulator of a broad range of cellular functions. It has been linked to Alzheimer's disease as well as various other diseases, including mood disorders, type 2 diabetes, and cancer. There is considerable evidence indicating that GSK-3ß in the central nervous system plays a role in the production of abnormal, hyperphosphorylated, microtubule-associated tau protein found in neurofibrillary tangles associated with Alzheimer's disease. A series of analogues containing a pyrimidine-based hinge-binding heterocycle was synthesized and evaluated, leading to the identification of highly potent GSK-3 inhibitors with excellent kinase selectivity. Further evaluation of 34 and 40 in vivo demonstrated that these compounds are orally bioavailable, brain-penetrant GSK-3 inhibitors that lowered levels of phosphorylated tau in a triple-transgenic mouse Alzheimer's disease model.

Design and synthesis of potent antagonists containing rigid spirocyclic privileged structures for the CGRP receptor.

We report the synthesis of rigid spirocyclic systems as conformationally constrained variants of the Ala-Phe-NH(2) dipeptide amide C-terminus of the calcitonin gene-related peptide (CGRP). CGRP receptor antagonists containing these moieties displayed potent affinity, functional antagonism and excellent oxidative stability. Structure-activity relationship studies demonstrated the relative importance of hydrogen bond donor/acceptor functionalities and the preferred orientation of an aromatic ring. Antagonists showed potent and full reversal of CGRP-induced dilation of ex vivo human intracranial arteries.

Calcitonin gene-related peptide (CGRP) receptor antagonists: novel aspartates and succinates.

Novel aspartate and succinate CGRP full antagonists were identified through core modification of a potent lead CGRP antagonist, BMS-694153. While aspartates were much less active and had a flat SAR, some of the succinates were very potent CGRP full antagonists and matched the potency of BMS-694153. The most potency resides in the S enantiomer as demonstrated through an asymmetric synthesis.

Calcitonin gene-related peptide (CGRP) receptor antagonists: pyridine as a replacement for a core amide group.

In our continuing efforts to identify CGRP receptor antagonists that can be dosed orally for the treatment of migraine headache, we have investigated a pyridine bioisosteric replacement of a polar amide portion of a previous lead compound, BMS-694153. Pyridine derivatives were discovered and their SAR was studied. Some of them showed excellent binding potency. However, oral bioavailability was low, even for compounds with good Caco-2 cell permeability.

The synthesis and SAR of calcitonin gene-related peptide (CGRP) receptor antagonists derived from tyrosine surrogates. Part 1.

We have systematically studied the effects of varying the central unnatural amino acid moiety on CGRP receptor antagonist potency and CYP inhibition in a series of ureidoamides. In this Letter, we report the discovery of compound 23, a potent CGRP receptor antagonist with only weak CYP3A4 inhibition. Unlike the triptans, compound 23 did not cause active constriction of ex vivo human cerebral arteries. At doses of 0.3-1 mg/kg (s.c.), 23 showed robust inhibition of CGRP-induced increases in marmoset facial blood flow, a validated migraine model. Ureidoamide 23 derives from a novel amino acid, 1H-indazol-5-yl substituted alanine as a tyrosine surrogate.

Design, synthesis and evaluation of constrained tetrahydroimidazopyrimidine derivatives as antagonists of corticotropin-releasing factor type 1 receptor (CRF1R).

Several tetrahydroimidazopyrimidines were prepared using silver assisted cyclization as the key step. The binding affinities of compounds thus prepared were evaluated in vitro toward hCRF(1)R. Initial lead compound 16 (K(i)=32 nM) demonstrated modest putative anxiolytic effects in the mouse canopy test. Further optimization using parallel synthesis provided compounds with K(i)'s <50 nM.

Discovery of 6-chloro-2-trifluoromethyl-7-aryl-7H-imidazo[1,2-a]imidazol-3-ylmethylamines, a novel class of corticotropin-releasing factor receptor type 1 (CRF1R) antagonists.

A novel series of [6-chloro-2-trifluoromethyl-7-aryl-7H-imidazo[1,2-a]imidazol-3-ylmethyl]-dialkylamines was discovered as potent CRF(1)R antagonists. The optimization of binding affinity in the series by the parallel reaction approach is discussed herein.

Blocking the CGRP Pathway for Acute and Preventive Treatment of Migraine: The Evolution of Success.

The pivotal role of calcitonin gene-related peptide (CGRP) in migraine pathophysiology was identified over 30 years ago, but the successful clinical development of targeted therapies has only recently been realized. This Perspective traces the decades long evolution of medicinal chemistry required to advance small molecule CGRP receptor antagonists, also called gepants, including the current clinical agents rimegepant, vazegepant, ubrogepant, and atogepant. Providing clinically effective blockade of CGRP signaling required surmounting multiple challenging hurdles, including defeating a sizable ligand with subnanomolar affinity for its receptor, designing antagonists with an extended confirmation and multiple pharmacophores while retaining solubility and oral bioavailability, and achieving circulating free plasma levels that provided near maximal CGRP receptor coverage. The clinical efficacy of oral and intranasal gepants and the injectable CGRP monoclonal antibodies (mAbs) are described, as are recent synthetic developments that have benefited from new structural biology data. The first oral gepant was recently approved and heralds a new era in the treatment of migraine.