Discovery of pyrrolo[2,1-f][1,2,4]triazine-based inhibitors of adaptor protein 2-associated kinase 1 for the treatment of pain.

Adaptor protein 2-associated kinase 1 (AAK1) is a member of the Ark1/Prk1 family of serine/threonine kinases and plays a role in modulating receptor endocytosis. AAK1 was identified as a potential therapeutic target for the treatment of neuropathic pain when it was shown that AAK1 knock out (KO) mice had a normal response to the acute pain phase of the mouse formalin model, but a reduced response to the persistent pain phase. Herein we report our early work investigating a series of pyrrolo[2,1-f][1,2,4]triazines as part of our efforts to recapitulate this KO phenotype with a potent, small molecule inhibitor of AAK1. The synthesis, structure-activity relationships (SAR), and in vivo evaluation of these AAK1 inhibitors is described.

Oral rimegepant for preventive treatment of migraine: a phase 2/3, randomised, double-blind, placebo-controlled trial.

BACKGROUND: Rimegepant is a calcitonin gene-related peptide receptor antagonist that has shown efficacy and safety in the acute treatment of migraine. We aimed to compare the efficacy of rimegepant with placebo for preventive treatment of migraine. METHODS: We did a multicentre, phase 2/3, randomised, double-blind, placebo-controlled trial at 92 sites in the USA. Adults with at least a 1-year history of migraine were recruited. After a 4-week observation period, eligible participants were randomised using an interactive web response system to oral rimegepant 75 mg or matching placebo every other day for 12 weeks (double-blind treatment phase). The primary efficacy endpoint was change from the 4-week observation period in the mean number of migraine days per month in the last 4 weeks of the double-blind treatment phase (weeks 9-12). Participants who received at least one dose of their assigned study medication and who had 14 days or more of data in the observation period and 14 days or more of data for at least one 4-week interval during the double-blind treatment phase were analysed for efficacy. Those who received at least one dose of study medication were analysed for safety. This study is registered with ClinicalTrials.gov, NCT03732638. FINDINGS: Between Nov 14, 2018, and Aug 30, 2019, 1591 participants were recruited and assessed for eligibility, of whom 747 were randomly allocated either rimegepant (n=373) or placebo (n=374). 695 participants were included in the analysis for efficacy, of whom 348 were assigned rimegepant and 347 were allocated placebo. Rimegepant was superior to placebo on the primary endpoint of change in the mean number of migraine days per month during weeks 9-12. The change from the observation period in mean number of migraine days per month during weeks 9-12 was -4·3 days (95% CI -4·8 to -3·9) with rimegepant and -3·5 days (-4·0 to -3·0) with placebo (least squares mean difference -0·8 days, 95% CI -1·46 to -0·20; p=0·0099). 741 participants received study medication and were included in the safety analysis. 133 (36%) of 370 patients who received rimegepant reported an adverse event, compared with 133 (36%) of 371 who received placebo. Seven (2%) participants who received rimegepant and four (1%) who received placebo discontinued the study due to an adverse event; no patients died. INTERPRETATION: Taken every other day, rimegepant was effective for preventive treatment of migraine. Tolerability was similar to that of placebo, and no unexpected or serious safety issues were noted. FUNDING: Biohaven Pharmaceuticals.

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%).

Efficacy, safety, and tolerability of rimegepant orally disintegrating tablet for the acute treatment of migraine: a randomised, phase 3, double-blind, placebo-controlled trial.

BACKGROUND: Rimegepant, a small molecule calcitonin gene-related peptide receptor antagonist, has shown efficacy in the acute treatment of migraine using a standard tablet formulation. The objective of this trial was to compare the efficacy, safety, and tolerability of a novel orally disintegrating tablet formulation of rimegepant at 75 mg with placebo in the acute treatment of migraine. METHODS: In this double-blind, randomised, placebo-controlled, multicentre phase 3 trial, adults aged 18 years or older with history of migraine of at least 1 year were recruited to 69 study centres in the USA. Participants were randomly assigned to receive rimegepant (75 mg orally disintegrating tablet) or placebo and instructed to treat a single migraine attack of moderate or severe pain intensity. The randomisation was stratified by the use of prophylactic medication (yes or no), and was carried out using an interactive web response system that was accessed by each clinical site. All participants, investigators, and the sponsor were masked to treatment group assignment. The coprimary endpoints were freedom from pain and freedom from the most bothersome symptom at 2 h postdose. The efficacy analyses used the modified intention-to-treat population, which included all patients who were randomly assigned, had a migraine attack with pain of moderate or severe intensity, took a dose of rimegepant or placebo, and had at least one efficacy assessment after administration of the dose. The safety analyses included all randomly assigned participants who received at least one dose of study medication. This study is registered with ClinicalTrials.gov, number NCT03461757, and is closed to accrual. FINDINGS: Between Feb 27 and Aug 28, 2018, 1811 participants were recruited and assessed for eligibility. 1466 participants were randomly assigned to the rimegepant (n=732) or placebo (n=734) groups, of whom 1375 received treatment with rimegepant (n=682) or placebo (n=693), and 1351 were evaluated for efficacy (rimegepant n=669, placebo n=682). At 2 h postdose, rimegepant orally disintegrating tablet was superior to placebo for freedom from pain (21% vs 11%, p<0·0001; risk difference 10, 95% CI 6-14) and freedom from the most bothersome symptom (35% vs 27%, p=0·0009; risk difference 8, 95% CI 3-13). The most common adverse events were nausea (rimegepant n=11 [2%]; placebo n=3 [<1%]) and urinary tract infection (rimegepant n=10 [1%]; placebo n=4 [1%]). One participant in each treatment group had a transaminase concentration of more than 3â€ˆ× the upper limit of normal; neither was related to study medication, and no elevations in bilirubin greater than 2â€ˆ× the upper limit of normal were reported. Treated participants reported no serious adverse events. INTERPRETATION: In the acute treatment of migraine, a single 75 mg dose of rimegepant in an orally disintegrating tablet formulation was more effective than placebo. Tolerability was similar to placebo, with no safety concerns. FUNDING: Biohaven Pharmaceuticals.

Safety of Rimegepant, an Oral CGRP Receptor Antagonist, Plus CGRP Monoclonal Antibodies for Migraine.

OBJECTIVE: Evaluate the safety and tolerability of oral rimegepant when used for acute treatment concomitantly with a monoclonal antibody (mAb) targeting the calcitonin gene-related peptide (CGRP) ligand or receptor (CGRP mAb) for the preventive treatment of migraine. BACKGROUND: The efficacy of CGRP mAbs for the preventive treatment of migraine and the small molecule CGRP receptor antagonist rimegepant for acute treatment has been demonstrated in randomized controlled clinical trials. Over the past few years, the US Food and Drug Administration has approved 4 CGRP mAbs for the preventive treatment of migraine and 2 small molecule CGRP receptor antagonists for the acute treatment of migraine. A previous case report of 2 patients receiving concomitant treatment with rimegepant and erenumab suggested that rimegepant may be safely used as acute treatment in patients who are also receiving a preventive regimen involving CGRP mAbs. We report here 13 additional patients with migraine who simultaneously used rimegepant and either erenumab, fremanezumab, or galcanezumab and assess the rate of on-treatment adverse events (AEs). METHODS: This was a substudy nested within a multicenter, open-label, long-term safety study in adults with 2-14 monthly migraine attacks of moderate to severe pain intensity. A subgroup experiencing 2-8 monthly attacks and taking a stable dose of a CGRP mAb also took rimegepant 75 mg as needed up to once daily for acute treatment for 12 weeks. RESULTS: The 13 patients (11 women [85%]; mean age 49.9 years) enrolled in the substudy were being treated with CGRP mAbs (erenumab [n = 7], fremanezumab [n = 4], or galcanezumab [n = 2]). Mean (SD) time in the rimegepant treatment period was 9.6 (4.6) weeks. Mean (SD) 4-week rimegepant exposure was 7.8 (5.5) doses; a total of 224 doses were taken. Five (38%) patients reported ≥1 on-treatment AE. Of these, 2 (15%) patients had mild or moderate nasopharyngitis; no other AEs occurred in ≥2 patients. Three patients had AEs of mild or moderate severity that were considered potentially treatment-related. No patients had serious AEs, AEs leading to discontinuation, or aminotransferase levels >3× the upper limit of normal. CONCLUSION: Rimegepant, when used as an oral acute treatment in patients receiving CGRP mAbs as preventive treatment, was well tolerated; no safety issues were identified. Studies involving larger patient populations are needed to confirm these findings.

Inhibition Mediated by Glycinergic and GABAergic Receptors on Excitatory Neurons in Mouse Superficial Dorsal Horn Is Location-Specific but Modified by Inflammation.

The superficial dorsal horn is the synaptic termination site for many peripheral sensory fibers of the somatosensory system. A wide range of sensory modalities are represented by these fibers, including pain, itch, and temperature. Because the involvement of local inhibition in the dorsal horn, specifically that mediated by the inhibitory amino acids GABA and glycine, is so important in signal processing, we investigated regional inhibitory control of excitatory interneurons under control conditions and peripheral inflammation-induced mechanical allodynia. We found that excitatory interneurons and projection neurons in lamina I and IIo are dominantly inhibited by GABA while those in lamina IIi and III are dominantly inhibited by glycine. This was true of identified neuronal subpopulations: neurokinin 1 receptor-expressing (NK1R+) neurons in lamina I were GABA-dominant while protein kinase C gamma-expressing (PKCγ+) neurons at the lamina IIi-III border were glycine-dominant. We found this pattern of synaptic inhibition to be consistent with the distribution of GABAergic and glycinergic neurons identified by immunohistochemistry. Following complete Freund's adjuvant injection into mouse hindpaw, the frequency of spontaneous excitatory synaptic activity increased and inhibitory synaptic activity decreased. Surprisingly, these changes were accompanied by an increase in GABA dominance in lamina IIi. Because this shift in inhibitory dominance was not accompanied by a change in the number of inhibitory synapses or the overall postsynaptic expression of glycine receptor α1 subunits, we propose that the dominance shift is due to glycine receptor modulation and the depressed function of glycine receptors is partially compensated by GABAergic inhibition.SIGNIFICANCE STATEMENT Pain associated with inflammation is a sensation we would all like to minimize. Persistent inflammation leads to cellular and molecular changes in the spinal cord dorsal horn, including diminished inhibition, which may be responsible for enhance excitability. Investigating inhibition in the dorsal horn following peripheral inflammation is essential for development of improved ways to control the associated pain. In this study, we have elucidated regional differences in inhibition of excitatory interneurons in mouse dorsal horn. We have also discovered that the dominating inhibitory neurotransmission within specific regions of dorsal horn switches following peripheral inflammation and the accompanying hypersensitivity to thermal and mechanical stimuli. Our novel findings contribute to a more complete understanding of inflammatory pain.

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.

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.

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%).

Discovery of (S,E)-3-(2-fluorophenyl)-N-(1-(3-(pyridin-3-yloxy)phenyl)ethyl)-acrylamide as a potent and efficacious KCNQ2 (Kv7.2) opener for the treatment of neuropathic pain.

Acrylamide (S)-6, a potent and efficacious KCNQ2 (Kv7.2) opener, demonstrated significant activity in two models of neuropathic pain and in the formalin test, suggesting that KCNQ2 openers may be useful in the treatment of neuropathic pain including diabetic neuropathy.

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.

Discovery and Optimization of Biaryl Alkyl Ethers as a Novel Class of Highly Selective, CNS-Penetrable, and Orally Active Adaptor Protein-2-Associated Kinase 1 (AAK1) Inhibitors for the Potential Treatment of Neuropathic Pain.

Recent mouse knockout studies identified adapter protein-2-associated kinase 1 (AAK1) as a viable target for treating neuropathic pain. BMS-986176/LX-9211 (4), as a highly selective, CNS-penetrable, and potent AAK1 inhibitor, has advanced into phase II human trials. On exploring the structure-activity relationship (SAR) around this biaryl alkyl ether chemotype, several additional compounds were found to be highly selective and potent AAK1 inhibitors with good druglike properties. Among these, compounds 43 and 58 showed very good efficacy in two neuropathic pain rat models and had excellent CNS penetration and spinal cord target engagement. Both compounds also exhibited favorable physicochemical and oral pharmacokinetic (PK) properties. Compound 58, a central pyridine isomer of BMS-986176/LX-9211 (4), was 4-fold more potent than 4 in vitro and showed lower plasma exposure needed to achieve similar efficacy compared to 4 in the CCI rat model. However, both 43 and 58 showed an inferior preclinical toxicity profile compared to 4.

Discovery of (S)-1-((2',6-Bis(difluoromethyl)-[2,4'-bipyridin]-5-yl)oxy)-2,4-dimethylpentan-2-amine (BMS-986176/LX-9211): A Highly Selective, CNS Penetrable, and Orally Active Adaptor Protein-2 Associated Kinase 1 Inhibitor in Clinical Trials for the Treatment of Neuropathic Pain.

Recent mouse knockout studies identified adapter protein-2 associated kinase 1 (AAK1) as a viable target for treating neuropathic pain. Potent small-molecule inhibitors of AAK1 have been identified and show efficacy in various rodent pain models. (S)-1-((2',6-Bis(difluoromethyl)-[2,4'-bipyridin]-5-yl)oxy)-2,4-dimethylpentan-2-amine (BMS-986176/LX-9211) (34) was identified as a highly selective, CNS penetrant, potent AAK1 inhibitor from a novel class of bi(hetero)aryl ethers. BMS-986176/LX9211 (34) showed excellent efficacy in two rodent neuropathic pain models and excellent central nervous system (CNS) penetration and target engagement at the spinal cord with an average brain to plasma ratio of 20 in rat. The compound exhibited favorable physicochemical and pharmacokinetic properties, had an acceptable preclinical toxicity profile, and was chosen for clinical trials. BMS-986176/LX9211 (34) completed phase I trials with good human pharmacokinetics and minimum adverse events and is currently in phase II clinical trials for diabetic peripheral neuropathic pain (ClinicalTrials.gov identifier: NCT04455633) and postherpetic neuralgia (ClinicalTrials.gov identifier: NCT04662281).

Oxime carbamate--discovery of a series of novel FAAH inhibitors.

A series of novel oxime carbamates have been identified as potent inhibitors of the key regulatory enzyme of the endocannabinoid signaling system, fatty acid amide hydrolase (FAAH). In this Letter, the rationale behind the discovery and the biological evaluations of this novel class of FAAH inhibitors are presented. Both in vitro and in vivo results of selected targets are discussed, along with inhibition kinetics and molecular modeling studies.(1).

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.