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Transient receptor potential ankyrin 1 (TRPA1) is a nonselective calcium-permeable ion channel highly expressed in the primary sensory neurons functioning as a polymodal sensor for exogenous and endogenous stimuli and has generated widespread interest as a target for inhibition due to its implication in neuropathic pain and respiratory disease. Herein, we describe the optimization of a series of potent, selective, and orally bioavailable TRPA1 small molecule antagonists, leading to the discovery of a novel tetrahydrofuran-based linker. Given the balance of physicochemical properties and strong in vivo target engagement in a rat AITC-induced pain assay, compound 20 was progressed into a guinea pig ovalbumin asthma model where it exhibited significant dose-dependent reduction of inflammatory response. Furthermore, the structure of the TRPA1 channel bound to compound 21 was determined via cryogenic electron microscopy to a resolution of 3 A, revealing the binding site and mechanism of action for this class of antagonists.

Despite the development of effective therapies, a substantial proportion of asthmatics continue to have uncontrolled symptoms, airflow limitation, and exacerbations. Transient receptor potential cation channel member A1 (TRPA1) agonists are elevated in human asthmatic airways, and in rodents, TRPA1 is involved in the induction of airway inflammation and hyperreactivity. Here, the discovery and early clinical development of GDC-0334, a highly potent, selective, and orally bioavailable TRPA1 antagonist, is described. GDC-0334 inhibited TRPA1 function on airway smooth muscle and sensory neurons, decreasing edema, dermal blood flow (DBF), cough, and allergic airway inflammation in several preclinical species. In a healthy volunteer Phase 1 study, treatment with GDC-0334 reduced TRPA1 agonist-induced DBF, pain, and itch, demonstrating GDC-0334 target engagement in humans. These data provide therapeutic rationale for evaluating TRPA1 inhibition as a clinical therapy for asthma.

Amplification and copy number alterations of the 17q23 amplicon are common in breast cancer and neuroblastoma and have been associated with early relapse and poor prognosis. Recent work identified a key vulnerability associated with amplicon-driven overexpression of TRIM37 in these tumor types (Meitinger et al. 2020; Yeow et al. 2020). High levels of TRIM37 prevent acentrosomal spindle assembly and render cells mitotically vulnerable to inhibition of polo-like kinase 4 (PLK4), a serine/threonine protein kinase that controls centrosome duplication. We have discovered potent small molecule inhibitors of PLK4 that are highly selective against the kinome, including against the closely related aurora kinases and PLK1-3. Self-regulation of PLK4 protein levels occurs through proteasomal degradation induced by PLK4 trans-autophosphorylation. ORIC PLK4 inhibitors blocked trans-autophosphorylation leading to stabilization of PLK4, thus directly demonstrating target inhibition in cells. Importantly, PLK4 inhibitor induced PLK4 protein stabilization correlated with cell viability, providing a quantifiable pharmacodynamic (PD) association with antitumor activity. Cell viability assessment across a cancer cell line panel revealed that the highly selective ORIC PLK4 inhibitors showed greater potency in TRIM37 high cancer cell lines as compared to TRIM37 low cell lines. In contrast, less selective compounds, including from the clinical literature, did not display differential potency in TRIM37 high versus low cancer cell lines. Importantly, cell potency in TRIM37 high cancer cells was rescued with knockdown of TRIM37, illustrating that selective PLK4 inhibitors are synthetic lethal with TRIM37 amplification. Oral administration of ORIC PLK4 inhibitors resulted in regressions of TRIM37 high xenograft tumors, with corresponding PD effects and no body weight loss. In summary, we have discovered novel, potent, highly selective small molecule inhibitors of PLK4 that are orally bioavailable and confirmed the potential for this new target in treating tumors with high levels of TRIM37. Citation Format: Kyle A. Edgar, Amy Young, Jared Moore, Xi Chen, Wei Fang, Jae H. Chang, Wayne Kong, Jason E. Long, Aleksandr Pankov, Anneleen Daemen, Daniel G. Shore, Robert Warne, Paul Gibbons, Chudi O. Ndubaku, Melissa R. Junttila, Lori S. Friedman. Discovery of novel, highly selective inhibitors of PLK4 that demonstrate in vivo regressions in TRIM37 high xenografts [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2633.

The discovery of disease-modifying therapies for Parkinson’s Disease (PD) represents a critical need in neurodegenerative medicine. Genetic mutations in LRRK2 are risk factors for the development of PD, and some of these mutations have been linked to increased LRRK2 kinase activity and neuronal toxicity in cellular and animal models. As such, research towards brain-permeable kinase inhibitors of LRRK2 has received much attention. In the course of a program to identify structurally diverse inhibitors of LRRK2 kinase activity, a 5-azaindazole series was optimized for potency, metabolic stability and brain penetration. A key design element involved the incorporation of an intramolecular hydrogen bond to increase permeability and potency against LRRK2. This communication will outline the structure-activity relationships of this matched pair series including the challenge of obtaining a desirable balance between metabolic stability and brain penetration.

Transient receptor potential ankyrin 1 (TRPA1) is a non-selective cation channel expressed in sensory neurons where it functions as an irritant sensor for a plethora of electrophilic compounds and is implicated in pain, itch, and respiratory disease. To study its function in various disease contexts, we sought to identify novel, potent, and selective small-molecule TRPA1 antagonists. Herein we describe the evolution of an N-isopropylglycine sulfonamide lead (1) to a novel and potent (4 R,5 S)-4-fluoro-5-methylproline sulfonamide series of inhibitors. Molecular modeling was utilized to derive low-energy three-dimensional conformations to guide ligand design. This effort led to compound 20, which possessed a balanced combination of potency and metabolic stability but poor solubility that ultimately limited in vivo exposure. To improve solubility and in vivo exposure, we developed methylene phosphate prodrug 22, which demonstrated superior oral exposure and robust in vivo target engagement in a rat model of AITC-induced pain.

A practical method for the Minisci reaction of electron-deficient pyrimidines with carboxylic acids is described. The one-step protocol allows for the alkylation of halo- and trifluoromethyl pyrimidines with a variety of readily available alkyl and (hetero)cycloalkyl carboxylic acids. These conditions permitted the facile synthesis of substituted pyrimidines, which are poised for further elaboration through divergent means.

A batchwise, multigram preparation of 2-azabicyclo-[2.1.1]hexane hydrochloride (1·HCl) was developed, delivering a total of 195 grams of material. The key synthetic step involves an intramolecular displacement of a primary alkyl chloride with a tert-butylsulfinamide to forge the [2.1.1]-bicyclic ring system.

The modulation of LRRK2 kinase activity by a selective small molecule inhibitor has been proposed as a potentially viable treatment for Parkinson's disease. By using aminopyrazoles as aniline bioisosteres, we discovered a novel series of LRRK2 inhibitors. Herein, we describe our optimization effort that resulted in the identification of a highly potent, brain-penetrant aminopyrazole LRRK2 inhibitor (18) that addressed the liabilities (e.g., poor solubility and metabolic soft spots) of our previously disclosed anilino-aminopyrimidine inhibitors. In in vivo rodent PKPD studies, 18 demonstrated good brain exposure and engendered significant reduction in brain pLRRK2 levels post-ip administration. The strategies of bioisosteric substitution of aminopyrazoles for anilines and attenuation of CYP1A2 inhibition described herein have potential applications to other drug discovery programs.

A one-pot procedure for the conversion of aromatic and heteroaromatic 2-nitroamines into bicyclic 2H-benzimidazoles is described. The procedure employs formic acid, iron powder, and an additive such as NH 4 Cl to reduce the nitro group and effect the imidazole cyclization with high-yielding conversions generally within one to two hours. The compatibility with a wide range of functionality demonstrates the general utility of this procedure.

A practical method for the Minisci reaction of electron-deficient pyrimidines with carboxylic acids is described. The one-step protocol allows for the alkylation of halo- and trifluoromethyl pyrimidines with a variety of readily available alkyl and (hetero)cycloalkyl carboxylic acids. These conditions permitted the facile synthesis of substituted pyrimidines, which are poised for further elaboration through divergent means.

A series of α-aryl pyrrolidine sulfonamide TRPA1 antagonists were advanced from an HTS hit to compounds that were stable in liver microsomes with retention of TRPA1 potency. Metabolite identification studies and physicochemical properties were utilized as a strategy for compound design. These compounds serve as starting points for further compound optimization.

Leucine-rich repeat kinase 2 (LRRK2) has drawn significant interest in the neuroscience research community because it is one of the most compelling targets for a potential disease-modifying Parkinson's disease therapy. Herein, we disclose structurally diverse small molecule inhibitors suitable for assessing the implications of sustained in vivo LRRK2 inhibition. Using previously reported aminopyrazole 2 as a lead molecule, we were able to engineer structural modifications in the solvent-exposed region of the ATP-binding site that significantly improve human hepatocyte stability, rat free brain exposure, and CYP inhibition and induction liabilities. Disciplined application of established optimal CNS design parameters culminated in the rapid identification of GNE-0877 (11) and GNE-9605 (20) as highly potent and selective LRRK2 inhibitors. The demonstrated metabolic stability, brain penetration across multiple species, and selectivity of these inhibitors support their use in preclinical efficacy and safety studies.

We have recently reported a series of tetrahydroquinazoline (THQ) mTOR inhibitors that produced a clinical candidate 1 (GDC-0349). Through insightful design, we hoped to discover and synthesize a new series of small molecule inhibitors that could attenuate CYP3A4 time-dependent inhibition commonly observed with the THQ scaffold, maintain or improve aqueous solubility and oral absorption, reduce free drug clearance, and selectively increase mTOR potency. Through key in vitro and in vivo studies, we demonstrate that a pyrimidoaminotropane based core was able to address each of these goals. This effort culminated in the discovery of 20 (GNE-555), a highly potent, selective, metabolically stable, and efficacious mTOR inhibitor.

There is a high demand for potent, selective, and brain-penetrant small molecule inhibitors of leucine-rich repeat kinase 2 (LRRK2) to test whether inhibition of LRRK2 kinase activity is a potentially viable treatment option for Parkinson's disease patients. Herein we disclose the use of property and structure-based drug design for the optimization of highly ligand efficient aminopyrimidine lead compounds. High throughput in vivo rodent cassette pharmacokinetic studies enabled rapid validation of in vitro-in vivo correlations. Guided by this data, optimal design parameters were established. Effective incorporation of these guidelines into our molecular design process resulted in the discovery of small molecule inhibitors such as GNE-7915 (18) and 19, which possess an ideal balance of LRRK2 cellular potency, broad kinase selectivity, metabolic stability, and brain penetration across multiple species. Advancement of GNE-7915 into rodent and higher species toxicity studies enabled risk assessment for early development.

Mutations in the genetic sequence of leucine-rich repeat kinase 2 (LRRK2) have been linked to increased LRRK2 activity and risk for the development of Parkinson's disease (PD). Potent and selective small molecules capable of inhibiting the kinase activity of LRRK2 will be important tools for establishing a link between the kinase activity of LRRK2 and PD. In the absence of LRRK2 kinase domain crystal structures, a LRRK2 homology model was developed that provided robust guidance in the hit-to-lead optimization of small molecule LRRK2 inhibitors. Through a combination of molecular modeling, sequence analysis, and matched molecular pair (MMP) activity cliff analysis, a potent and selective lead inhibitor was discovered. The selectivity of this compound could be understood using the LRRK2 homology model, and application of this learning to a series of 2,4-diaminopyrimidine inhibitors in a scaffold hopping exercise led to the identification of highly potent and selective LRRK2 inhibitors that were also brain penetrable.

Optimized conditions allow the reductive cyclization of various aromatic substrates bearing a wide range of functionalities.

Malonic acid half thioesters (MAHTs) and malonic acid half oxyesters (MAHOs) are shown to undergo decarboxylative nucleophilic addition reactions with ketone and aldehyde electrophiles in the presence of stoichiometric or catalytic quantities of triethylamine at room temperature. The ability to perform these reactions under metal-free conditions has enabled a detailed mechanistic analysis of the reaction pathway leading to the (1)H NMR spectroscopic characterization of a postnucleophilic addition/predecarboxylation intermediate and experimental evidence for a reversible formation of this intermediate followed by an irreversible decarboxylation. Rate constants for each of the bond forming/bond breaking steps in the reaction pathway were also determined, casting light on the differing reactivity between MAHO and MAHT nucleophiles in these processes. Finally, the mechanistic insights gained through these studies have been employed in the development of a new decarboxylative coumarin synthesis.