Empowering Voices: Inspiring Women in Medicinal Chemistry.

As we celebrate International Women's Day 2024 with the theme "Inspire Inclusion", the women of the ACS Medicinal Chemistry Division (MEDI) want to foster a sense of belonging, relevance, and empowerment by sharing uplifting stories of what inspired them to become medicinal chemists. In this editorial, we are featuring female medicinal chemistry scientists to provide role models, encouragement, and inspiration to others. We asked women medicinal chemists to contribute a brief paragraph about what inspired them to become medicinal chemists or what inspires them today as medicinal chemists. The responses and contributions highlight their passions and motivations, such as their love of the sciences and their drive to improve human health by contributing to basic research and creating lifesaving drugs.

Empowering Voices: Inspiring Women in Medicinal Chemistry.

As we celebrate International Women's Day 2024 with the theme "Inspire Inclusion", the women of the ACS Medicinal Chemistry Division (MEDI) want to foster a sense of belonging, relevance, and empowerment by sharing uplifting stories of what inspired them to become medicinal chemists. In this editorial, we are featuring female medicinal chemistry scientists to provide role models, encouragement, and inspiration to others. We asked women medicinal chemists to contribute a brief paragraph about what inspired them to become medicinal chemists or what inspires them today as medicinal chemists. The responses and contributions highlight their passions and motivations, such as their love of the sciences and their drive to improve human health by contributing to basic research and creating lifesaving drugs.

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.

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.

Bicyclic Heterocyclic Replacement of an Aryl Amide Leading to Potent and Kinase-Selective Adaptor Protein 2-Associated Kinase 1 Inhibitors.

Adaptor protein 2-associated kinase 1 (AAK1) is a serine/threonine kinase that was identified as a therapeutic target for the potential treatment of neuropathic pain. Inhibition of AAK1 in the central nervous system, particularly within the spinal cord, was found to be the relevant site for achieving an antinociceptive effect. We previously reported that compound 7 is a brain-penetrant, AAK1 inhibitor that showed efficacy in animal models for neuropathic pain. One approach we took to improve upon the potency of 7 involved tying the amide back into the neighboring phenyl ring to form a bicyclic heterocycle. Investigation of the structure-activity relationships (SARs) of substituents on the resultant quinazoline and quinoline ring systems led to the identification of (S)-31, a brain-penetrant, AAK1-selective inhibitor with improved enzyme and cellular potency compared to 7. The synthesis, SAR, and in vivo evaluation of a series of quinazoline and quinoline-based AAK1 inhibitors are described herein.

Discovery, Structure-Activity Relationships, and In Vivo Evaluation of Novel Aryl Amides as Brain Penetrant Adaptor Protein 2-Associated Kinase 1 (AAK1) Inhibitors for the Treatment of Neuropathic Pain.

Effective treatment of chronic pain, in particular neuropathic pain, without the side effects that often accompany currently available treatment options is an area of significant unmet medical need. A phenotypic screen of mouse gene knockouts led to the discovery that adaptor protein 2-associated kinase 1 (AAK1) is a potential therapeutic target for neuropathic pain. The synthesis and optimization of structure-activity relationships of a series of aryl amide-based AAK1 inhibitors led to the identification of 59, a brain penetrant, AAK1-selective inhibitor that proved to be a valuable tool compound. Compound 59 was evaluated in mice for the inhibition of µ2 phosphorylation. Studies conducted with 59 in pain models demonstrated that this compound was efficacious in the phase II formalin model for persistent pain and the chronic-constriction-injury-induced model for neuropathic pain in rats. These results suggest that AAK1 inhibition is a promising approach for the treatment of neuropathic pain.

Discovery of VU2957 (Valiglurax): An mGlu4 Positive Allosteric Modulator Evaluated as a Preclinical Candidate for the Treatment of Parkinson's Disease.

Herein, we report the discovery of a novel potent, selective, CNS penetrant, and orally bioavailable mGlu4 PAM, VU0652957 (VU2957, Valiglurax). VU2957 possessed attractive in vitro and in vivo pharmacological and DMPK properties across species. To advance toward the clinic, a spray-dried dispersion (SDD) formulation of VU2957 was developed to support IND-enabling toxicology studies. Based on its overall profile, VU2957 was evaluated as a preclinical development candidate for the treatment of Parkinson's disease.

The discovery of VU0652957 (VU2957, Valiglurax): SAR and DMPK challenges en route to an mGlu4 PAM development candidate.

This letter describes the first account of the chemical optimization (SAR and DMPK profiling) of a new series of mGlu4 positive allosteric modulators (PAMs), leading to the identification of VU0652957 (VU2957, Valiglurax), a compound profiled as a preclinical development candidate. Here, we detail the challenges faced in allosteric modulator programs (e.g., steep SAR, as well as subtle structural changes affecting overall physiochemical/DMPK properties and CNS penetration).

Discovery and characterization of N-(1,3-dialkyl-1H-indazol-6-yl)-1H-pyrazolo[4,3-b]pyridin-3-amine scaffold as mGlu4 positive allosteric modulators that mitigate CYP1A2 induction liability.

Previous reports from our laboratory disclosed the structure and activity of a novel 1H-pyrazolo[4,3-b]pyridine-3-amine scaffold (VU8506) which showed excellent potency, selectivity and in vivo efficacy in preclinical rodent models of Parkinson's disease. Unfortunately, this compound suffered from significant CYP1A2 induction as measured through upstream AhR activation (125-fold) and thus was precluded from further advancement in chronic studies. Herein, we report a new scaffold developed recently which was systematically studied in order to mitigate the CYP1A2 liabilities presented in the earlier scaffolds. We have identified a novel structure that maintains the potency and selectivity of other mGlu4 PAMs, leading to 9i (hmGlu4 EC50 = 43 nM; AhR activation = 2.3-fold).

BMS-986163, a Negative Allosteric Modulator of GluN2B with Potential Utility in Major Depressive Disorder.

There is a significant unmet medical need for more efficacious and rapidly acting antidepressants. Toward this end, negative allosteric modulators of the N-methyl-d-aspartate receptor subtype GluN2B have demonstrated encouraging therapeutic potential. We report herein the discovery and preclinical profile of a water-soluble intravenous prodrug BMS-986163 (6) and its active parent molecule BMS-986169 (5), which demonstrated high binding affinity for the GluN2B allosteric site (Ki = 4.0 nM) and selective inhibition of GluN2B receptor function (IC50 = 24 nM) in cells. The conversion of prodrug 6 to parent 5 was rapid in vitro and in vivo across preclinical species. After intravenous administration, compounds 5 and 6 have exhibited robust levels of ex vivo GluN2B target engagement in rodents and antidepressant-like activity in mice. No significant off-target activity was observed for 5, 6, or the major circulating metabolites met-1 and met-2. The prodrug BMS-986163 (6) has demonstrated an acceptable safety and toxicology profile and was selected as a preclinical candidate for further evaluation in major depressive disorder.

Preclinical Characterization of (R)-3-((3S,4S)-3-fluoro-4-(4-hydroxyphenyl)piperidin-1-yl)-1-(4-methylbenzyl)pyrrolidin-2-one (BMS-986169), a Novel, Intravenous, Glutamate N-Methyl-d-Aspartate 2B Receptor Negative Allosteric Modulator with Potential in Major Depressive Disorder.

(R)-3-((3S,4S)-3-fluoro-4-(4-hydroxyphenyl)piperidin-1-yl)-1-(4-methylbenzyl)pyrrolidin-2-one (BMS-986169) and the phosphate prodrug 4-((3S,4S)-3-fluoro-1-((R)-1-(4-methylbenzyl)-2-oxopyrrolidin-3-yl)piperidin-4-yl)phenyl dihydrogen phosphate (BMS-986163) were identified from a drug discovery effort focused on the development of novel, intravenous glutamate N-methyl-d-aspartate 2B receptor (GluN2B) negative allosteric modulators (NAMs) for treatment-resistant depression (TRD). BMS-986169 showed high binding affinity for the GluN2B subunit allosteric modulatory site (Ki = 4.03-6.3 nM) and selectively inhibited GluN2B receptor function in Xenopus oocytes expressing human N-methyl-d-aspartate receptor subtypes (IC50 = 24.1 nM). BMS-986169 weakly inhibited human ether-a-go-go-related gene channel activity (IC50 = 28.4 µM) and had negligible activity in an assay panel containing 40 additional pharmacological targets. Intravenous administration of BMS-986169 or BMS-986163 dose-dependently increased GluN2B receptor occupancy and inhibited in vivo [3H](+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine ([3H]MK-801) binding, confirming target engagement and effective cleavage of the prodrug. BMS-986169 reduced immobility in the mouse forced swim test, an effect similar to intravenous ketamine treatment. Decreased novelty suppressed feeding latency, and increased ex vivo hippocampal long-term potentiation was also seen 24 hours after acute BMS-986163 or BMS-986169 administration. BMS-986169 did not produce ketamine-like hyperlocomotion or abnormal behaviors in mice or cynomolgus monkeys but did produce a transient working memory impairment in monkeys that was closely related to plasma exposure. Finally, BMS-986163 produced robust changes in the quantitative electroencephalogram power band distribution, a translational measure that can be used to assess pharmacodynamic activity in healthy humans. Due to the poor aqueous solubility of BMS-986169, BMS-986163 was selected as the lead GluN2B NAM candidate for further evaluation as a novel intravenous agent for TRD.

Synthesis and evaluation of prodrugs of corticotropin-releasing factor-1 (CRF1) receptor antagonist BMS-665053 leading to improved oral bioavailability.

A series of phosphate and ester-based prodrugs of anilinopyrazinone 1 (BMS-665053) containing either a methylene or an (acyloxy)alkoxy linker was prepared and evaluated in rat pharmacokinetic studies with the goal of improving the oral bioavailability of the parent (1). The prodrugs, in general, had improved aqueous solubility and oral bioavailability compared to 1. Prodrug 12, which contains an (acyloxy)alkoxy linker, showed the greatest improvement in the oral bioavailability relative to the parent (1), with a seven-fold increase (from 5% to 36%) in rat pharmacokinetic studies.

Triazolopyridine ethers as potent, orally active mGlu2 positive allosteric modulators for treating schizophrenia.

Triazolopyridine ethers with mGlu2 positive allosteric modulator (PAM) activity are disclosed. The synthesis, in vitro activity, and metabolic stability data for a series of analogs is provided. The effort resulted in the discovery of a potent, selective, and brain penetrant lead molecule BMT-133218 ((+)-7m). After oral administration at 10mg/kg, BMT-133218 demonstrated full reversal of PCP-stimulated locomotor activity and prevented MK-801-induced working memory deficits in separate mouse models. Also, reversal of impairments in executive function were observed in rat set-shifting studies at 3 and 10mg/kg (p.o.). Extensive plasma protein binding as the result of high lipophilicity likely limited activity at lower doses. Optimized triazolopyridine ethers offer utility as mGlu2 PAMs for the treatment of schizophrenia and merit further preclinical investigation.

Development of 1H-Pyrazolo[3,4-b]pyridines as Metabotropic Glutamate Receptor 5 Positive Allosteric Modulators.

The metabotropic glutamate receptor 5 (mGluR5) is an attractive target for the treatment of schizophrenia due to its role in regulating glutamatergic signaling in association with the N-methyl-d-aspartate receptor (NMDAR). We describe the synthesis of 1H-pyrazolo[3,4-b]pyridines and their utility as mGluR5 positive allosteric modulators (PAMs) without inherent agonist activity. A facile and convergent synthetic route provided access to a structurally diverse set of analogues that contain neither the aryl-acetylene-aryl nor aryl-methyleneoxy-aryl elements, the predominant structural motifs described in the literature. Binding studies suggest that members of our new chemotype do not engage the receptor at the MPEP and CPPHA mGluR5 allosteric sites. SAR studies culminated in the first non-MPEP site PAM, 1H-pyrazolo[3,4-b]pyridine 31 (BMT-145027), to improve cognition in a preclinical rodent model of learning and memory.

Difluorocyclobutylacetylenes as positive allosteric modulators of mGluR5 with reduced bioactivation potential.

Schizophrenia is a serious illness that affects millions of patients and has been associated with N-methyl-d-aspartate receptor (NMDAR) hypofunction. It has been demonstrated that activation of metabotropic glutamate receptor 5 (mGluR5) enhances NMDA receptor function, suggesting the potential utility of mGluR5 positive allosteric modulators (PAMs) in the treatment of schizophrenia. Herein we describe the optimization of an mGluR5 PAM by replacement of a phenyl with aliphatic heterocycles and carbocycles as a strategy to reduce bioactivation in a biaryl acetylene chemotype. Replacement with a difluorocyclobutane followed by further optimization culminated in the identification of compound 32, a low fold shift PAM with reduced bioactivation potential. Compound 32 demonstrated favorable brain uptake and robust efficacy in mouse novel object recognition (NOR) at low doses.

Discovery of Indazoles as Potent, Orally Active Dual Neurokinin 1 Receptor Antagonists and Serotonin Transporter Inhibitors for the Treatment of Depression.

Combination studies of neurokinin 1 (NK1) receptor antagonists and serotonin-selective reuptake inhibitors (SSRIs) have shown promise in preclinical models of depression. Such a combination may offer important advantages over the current standard of care. Herein we describe the discovery and optimization of an indazole-based chemotype to provide a series of potent dual NK1 receptor antagonists/serotonin transporter (SERT) inhibitors to overcome issues of ion channel blockade. This effort culminated in the identification of compound 9, an analogue that demonstrated favorable oral bioavailability, excellent brain uptake, and robust in vivo efficacy in a validated depression model. Over the course of this work, a novel heterocycle-directed asymmetric hydrogenation was developed to facilitate installation of the key stereogenic center.

Oxazolidinone-based allosteric modulators of mGluR5: Defining molecular switches to create a pharmacological tool box.

Herein we describe the structure activity relationships uncovered in the pursuit of an mGluR5 positive allosteric modulator (PAM) for the treatment of schizophrenia. It was discovered that certain modifications of an oxazolidinone-based chemotype afforded predictable changes in the pharmacological profile to give analogs with a wide range of functional activities. The discovery of potent silent allosteric modulators (SAMs) allowed interrogation of the mechanism-based liabilities associated with mGluR5 activation and drove our medicinal chemistry effort toward the discovery of low efficacy (fold shift) PAMs devoid of agonist activity. This work resulted in the identification of dipyridyl 22 (BMS-952048), a compound with a favorable free fraction, efficacy in a rodent-based cognition model, and low potential for convulsions in mouse.

Discovery, Synthesis, and Preclinical Characterization of N-(3-Chloro-4-fluorophenyl)-1H-pyrazolo[4,3-b]pyridin-3-amine (VU0418506), a Novel Positive Allosteric Modulator of the Metabotropic Glutamate Receptor 4 (mGlu4).

The efficacy of positive allosteric modulators (PAMs) of the metabotropic glutamate receptor 4 (mGlu4) in preclinical rodent models of Parkinson's disease has been established by a number of groups. Here, we report an advanced preclinically characterized mGlu4 PAM, N-(3-chloro-4-fluorophenyl)-1H-pyrazolo[4,3-b]pyridin-3-amine (VU0418506). We detail the discovery of VU0418506 starting from a common picolinamide core scaffold and evaluation of a number of amide bioisosteres leading to the novel pyrazolo[4,3-b]pyridine head group. VU0418506 has been characterized as a potent and selective mGlu4 PAM with suitable in vivo pharmacokinetic properties in three preclinical safety species.

Discovery and Preclinical Evaluation of BMS-955829, a Potent Positive Allosteric Modulator of mGluR5.

Positive allosteric modulators (PAMs) of the metabotropic glutamate receptor subtype 5 (mGluR5) are of interest due to their potential therapeutic utility in schizophrenia and other cognitive disorders. Herein we describe the discovery and optimization of a novel oxazolidinone-based chemotype to identify BMS-955829 (4), a compound with high functional PAM potency, excellent mGluR5 binding affinity, low glutamate fold shift, and high selectivity for the mGluR5 subtype. The low fold shift and absence of agonist activity proved critical in the identification of a molecule with an acceptable preclinical safety profile. Despite its low fold shift, 4 retained efficacy in set shifting and novel object recognition models in rodents.

Synthesis and evaluation of carbamate and aryl ether substituted pyrazinones as corticotropin releasing factor-1 (CRF1) receptor antagonists.

A series of pyrazinone-based compounds incorporating either carbamate or aryl ether groups was synthesized and evaluated as corticotropin-releasing factor-1 (CRF1) receptor antagonists. Structure-activity relationship studies led to the identification of highly potent CRF1 receptor antagonists 14a (IC50=0.74 nM) and 14b (IC50=1.9 nM). The synthesis, structure-activity relationships and in vitro metabolic stability properties of compounds in this series will be described.