Design of a brain-penetrant CDK4/6 inhibitor for glioblastoma.

CDK4 and CDK6 are kinases with similar sequences that regulate cell cycle progression and are validated targets in the treatment of cancer. Glioblastoma is characterized by a high frequency of CDKN2A/CCND2/CDK4/CDK6 pathway dysregulation, making dual inhibition of CDK4 and CDK6 an attractive therapeutic approach for this disease. Abemaciclib, ribociclib, and palbociclib are approved CDK4/6 inhibitors for the treatment of HR+/HER2- breast cancer, but these drugs are not expected to show strong activity in brain tumors due to poor blood brain barrier penetration. Herein, we report the identification of a brain-penetrant CDK4/6 inhibitor derived from a literature molecule with low molecular weight and topological polar surface area (MW = 285 and TPSA = 66 Å2), but lacking the CDK2/1 selectivity profile due to the absence of a basic amine. Removal of a hydrogen bond donor via cyclization of the pyrazole allowed for the introduction of basic and semi-basic amines, while maintaining in many cases efflux ratios reasonable for a CNS program. Ultimately, a basic spiroazetidine (cpKa = 8.8) was identified that afforded acceptable selectivity over anti-target CDK1 while maintaining brain-penetration in vivo (mouse Kp,uu = 0.20-0.59). To probe the potency and selectivity, our lead compound was evaluated in a panel of glioblastoma cell lines. Potency comparable to abemaciclib was observed in Rb-wild type lines U87MG, DBTRG-05MG, A172, and T98G, while Rb-deficient cell lines SF539 and M059J exhibited a lack of sensitivity.

Hippo pathway inhibition by blocking the YAP/TAZ-TEAD interface: a patent review.

Introduction: The Hippo pathway represents a new and intriguing opportunity for the treatment of cancer. Activation or overexpression of Yes-associated protein (YAP) or transcriptional coactivator with PDZ-binding motif (TAZ) has been shown to lead to cell transformation and tumor development. To date, no small molecule compounds targeting this pathway have progressed to the clinic, illustrating both its potential and its infancy. Areas covered: The present review seeks to summarize published patent applications from assignee companies that have disclosed direct small molecule inhibitors of the YAP/TAZ-transcriptional enhanced associate domain (TEAD) interaction. Expert opinion: The Hippo pathway, and specifically the YAP/TAZ-TEAD transcriptional complex, has been shown to be a promising target for the treatment of cancer. However, reports in the area of small molecules targeting the YAP/TAZ-TEAD transcriptional activation complex are few and far between, with only two published patent applications that disclose compounds with moderate levels of pathway inhibition. Interestingly, the YAP/TAZ-TEAD complex can be disrupted through two very different mechanisms, one of which is direct inhibition at either the Ω-loop or the α-helix of the YAP-TEAD binding interface. Both YAP protein segments have been shown to be important to TEAD binding. Alternatively, it has been reported that allosteric inhibition might be accomplished by binding the TEAD palmitoylation pocket, thus disrupting YAP binding and also native protein stabilization. The advantages and liabilities of disrupting the YAP/TAZ-TEAD complex through these two distinct mechanisms have yet to be fully elucidated, and it remains unclear which approach, if any, will generate the first clinical stage inhibitor of the Hippo pathway.

Design and synthesis of a biaryl series as inhibitors for the bromodomains of CBP/P300.

A novel, potent, and orally bioavailable inhibitor of the bromodomain of CBP, compound 35 (GNE-207), has been identified through SAR investigations focused on optimizing al bicyclic heteroarene to replace the aniline present in the published GNE-272 series. Compound 35 has excellent CBP potency (CBP IC50 = 1 nM, MYC EC50 = 18 nM), a selectively index of >2500-fold against BRD4(1), and exhibits a good pharmacokinetic profile.

A Unique Approach to Design Potent and Selective Cyclic Adenosine Monophosphate Response Element Binding Protein, Binding Protein (CBP) Inhibitors.

The epigenetic regulator CBP/P300 presents a novel therapeutic target for oncology. Previously, we disclosed the development of potent and selective CBP bromodomain inhibitors by first identifying pharmacophores that bind the KAc region and then building into the LPF shelf. Herein, we report the "hybridization" of a variety of KAc-binding fragments with a tetrahydroquinoline scaffold that makes optimal interactions with the LPF shelf, imparting enhanced potency and selectivity to the hybridized ligand. To demonstrate the utility of our hybridization approach, two analogues containing unique Asn binders and the optimized tetrahydroquinoline moiety were rapidly optimized to yield single-digit nanomolar inhibitors of CBP with exquisite selectivity over BRD4(1) and the broader bromodomain family.

GNE-781, A Highly Advanced Potent and Selective Bromodomain Inhibitor of Cyclic Adenosine Monophosphate Response Element Binding Protein, Binding Protein (CBP).

Inhibition of the bromodomain of the transcriptional regulator CBP/P300 is an especially interesting new therapeutic approach in oncology. We recently disclosed in vivo chemical tool 1 (GNE-272) for the bromodomain of CBP that was moderately potent and selective over BRD4(1). In pursuit of a more potent and selective CBP inhibitor, we used structure-based design. Constraining the aniline of 1 into a tetrahydroquinoline motif maintained potency and increased selectivity 2-fold. Structure-activity relationship studies coupled with further structure-based design targeting the LPF shelf, BC loop, and KAc regions allowed us to significantly increase potency and selectivity, resulting in the identification of non-CNS penetrant 19 (GNE-781, TR-FRET IC50 = 0.94 nM, BRET IC50 = 6.2 nM; BRD4(1) IC50 = 5100 nΜ) that maintained good in vivo PK properties in multiple species. Compound 19 displays antitumor activity in an AML tumor model and was also shown to decrease Foxp3 transcript levels in a dose dependent manner.

RORγ antagonists and inverse agonists: a patent review.

INTRODUCTION: The transcription factor RORγ plays a critical role in the expression of pro-inflammatory cytokine interleukin IL-17 and is therefore an attractive target for the treatment of inflammatory diseases. Interest in this molecular target has been heightened by the advancement of orally and topically administered RORγ modulators into clinical trials. Areas covered: The present review seeks to summarize published patent applications from assignee companies that have disclosed Investigational New Drug (IND) filings for small molecule RORγ/RORγt antagonists and inverse agonists. Expert opinion: The field of RORγ research is extremely competitive, with the majority of companies targeting psoriasis as the primary disease indication. Vitae Pharmaceuticals is currently the most advanced, with a potential first-in-class oral RORγ-modulator for the treatment of psoriasis. Future efforts will likely expand into potential applications of RORγ-modulators in the lesser explored immune-related areas of rheumatoid arthritis, type 1 diabetes, lupus, and irritable bowel disorder, as well as cancer immunotherapy and castration-resistant prostate cancer.

Transition-Metal-Free Synthesis of Tertiary Aminocyclopropanes.

A transition-metal-free methodology for the construction of pharmaceutically relevant tertiary aminocyclopropanes is reported. Hydrazonamides, safe and stable carbene precursors, undergo smooth cyclopropanation with vinyl arenes in the presence of a base. The reaction proceeds with stereoselectivity to favor the Z isomer and provides facile access to a variety of substitution patterns through variation of the coupling partners.

Recent progress on nuclear receptor RORγ modulators.

The retinoic acid receptor-related orphan receptor RORγ plays key roles in the development and differentiation of TH17 cells, and thus in IL-17 expression, thymocyte development and regulation of metabolism. With the recent progression into phase 2 clinical trials of both oral and topically administered inverse agonists, and with others close behind, there is significant interest in the discovery of RORγ modulators. This digest covers key developments around RORγ agonists, antagonists and inverse agonists; orthosteric and allosteric binders; and aims to summarize the available information concerning the potential utility of RORγ modulators.

Ru-Based Z-Selective Metathesis Catalysts with Modified Cyclometalated Carbene Ligands.

A series of cyclometalated Z-selective ruthenium olefin metathesis catalysts with alterations to the N-heterocyclic carbene (NHC) ligand were prepared. X-Ray crystal structures of several new catalysts were obtained, elucidating the structural features of this class of cyclometalated complexes. The metathesis activity of each stable complex was evaluated, and one catalyst, bearing geminal dimethyl backbone substitution, was found to be comparable to our best Z-selective metathesis catalyst to date.

Total syntheses of indolactam alkaloids (-)-indolactam V, (-)-pendolmycin, (-)-lyngbyatoxin A, and (-)-teleocidin A-2.

We report the total syntheses of (-)-indolactam V and the C7-substituted indolactam alkaloids (-)-pendolmycin, (-)-lyngbyatoxin A, and (-)-teleocidin A-2. The strategy for preparing indolactam V relies on a distortion-controlled indolyne functionalization reaction to establish the C4-N linkage, in addition to an intramolecular conjugate addition to build the conformationally-flexible nine-membered ring. The total synthesis of indolactam V then sets the stage for the divergent synthesis of the other targeted alkaloids. Specifically, late-stage sp2-sp3 cross-couplings on an indolactam V derivative are used to introduce the key C7 substituents and the necessary quaternary carbons. These challenging couplings, in addition to other delicate manipulations, all proceed in the presence of a basic tertiary amine, an unprotected secondary amide, and an unprotected indole. Thus, our approach not only enables the enantiospecific total syntheses of four indolactam alkaloids, but also serves as a platform for probing complexity-generating and chemoselective transformations in the context of alkaloid total synthesis.

Formal Anti-Markovnikov Hydroamination of Terminal Olefins.

A new strategy to access linear amines from terminal olefin precursors is reported. This two-step, one-pot hydroamination methodology employs sequential oxidation and reduction catalytic cycles. The formal hydroamination transformation proceeds with excellent regioselectivity, and only the anti-Markovnikov product is observed. Up to 70% yield can be obtained from styrenes or aliphatic olefins and either primary or secondary aromatic amines. Additionally, the scope is broad with respect to the olefin and accommodates a variety of functionalities; we demonstrate that amines with removable aryl protecting groups may be utilized to allow access to a more diverse array of hydroamination adducts.

Steric effects compete with aryne distortion to control regioselectivities of nucleophilic additions to 3-silylarynes.

We report an experimental and computational study of 3-silylarynes. The addition of nucleophiles yield ortho-substituted products as a result of aryne distortion, but meta-substituted products form predominately when the nucleophile is large. Computations correctly predict the preferred site of attack observed in both nucleophilic addition and cycloaddition experiments. Nucleophilic additions to 3-tert-butylbenzyne, which is not significantly distorted, give meta-substituted products.

An efficient computational model to predict the synthetic utility of heterocyclic arynes.

Think before you act: a computational approach is reported for evaluating the synthetic potential of heterocyclic arynes. Routine and rapid calculations of arene dehydrogenation energies and aryne angle distortion predict the likelihood that a given hetaryne can be generated, as well as the degree of regioselectivity expected in a reaction between a given hetaryne and a nucleophilic trapping agent.

Overturning indolyne regioselectivities and synthesis of indolactam V.

We report the design and synthesis of an indolyne that displays a reversal in regioselectivity, in both nucleophilic addition and cycloaddition reactions, compared to typical 4,5-indolynes. Our approach utilizes simple computations to predict regioselectivity in reactions of unsymmetrical arynes. With this methodology, novel benzenoid-substituted indoles can be accessed with significant regiocontrol. Furthermore, the technology provides an unconventional tactic for the synthesis of C4-substituted indole alkaloids, as demonstrated by a synthesis of indolactam V.

Indolyne experimental and computational studies: synthetic applications and origins of selectivities of nucleophilic additions.

Efficient syntheses of 4,5-, 5,6-, and 6,7-indolyne precursors beginning from commercially available hydroxyindole derivatives are reported. The synthetic routes are versatile and allow access to indolyne precursors that remain unsubstituted on the pyrrole ring. Indolynes can be generated under mild fluoride-mediated conditions, trapped by a variety of nucleophilic reagents, and used to access a number of novel substituted indoles. Nucleophilic addition reactions to indolynes proceed with varying degrees of regioselectivity; distortion energies control regioselectivity and provide a simple model to predict the regioselectivity in the nucleophilic additions to indolynes and other unsymmetrical arynes. This model has led to the design of a substituted 4,5-indolyne that exhibits enhanced nucleophilic regioselectivity.

Indolyne and aryne distortions and nucleophilic regioselectivites.

Density functional theory computations reproduce the surprisingly high regioselectivities in nucleophilic additions and cycloadditions to 4,5-indolynes and the low regioselectivities in the reactions of 5,6-indolynes. Transition-state distortion energies control the regioselectivities, activating the 5 and 6 positions over the 4 and 7 positions, leading to high preferences for 5- and 6-substituted products from 4,5- and 6,7-indolynes, respectively. Orbital and electrostatic interactions have only minor effects, producing low regioselectivities in the reactions of 5,6-indolynes. The distortion model predicts high regioselectivities with 6,7-indolynes; these have been verified experimentally. The regioselectivities found with other arynes are explained on the basis of distortion energies that are reflected in reactant geometries.

Efficient synthesis of 2-(trimethylsilyl)phenyl trifluoromethanesulfonate: a versatile precursor to o-benzyne.

An efficient procedure for the gram-scale preparation of 2-(trimethylsilyl)phenyl trifluoromethanesulfonate, a versatile precursor to o-benzyne, is presented. The three-step sequence utilizes phenol as the starting material, requires only one chromatographic purification, and ultimately delivers the desired silyltriflate in 66% overall yield.

Indolynes as electrophilic indole surrogates: fundamental reactivity and synthetic applications.

A mild method to access a variety of substituted indole derivatives has been developed. The strategy relies on the generation of highly reactive indolyne intermediates, which function as electrophilic indole surrogates.