6-Azaspiro[2.5]octanes as small molecule agonists of the human glucagon-like peptide-1 receptor.

Activation of the glucagon-like peptide-1 (GLP-1) receptor stimulates insulin release, lowers plasma glucose levels, delays gastric emptying, increases satiety, suppresses food intake, and affords weight loss in humans. These beneficial attributes have made peptide-based agonists valuable tools for the treatment of type 2 diabetes mellitus and obesity. However, efficient, and consistent delivery of peptide agents generally requires subcutaneous injection, which can reduce patient utilization. Traditional orally absorbed small molecules for this target may offer improved patient compliance as well as the opportunity for co-formulation with other oral therapeutics. Herein, we describe an SAR investigation leading to small-molecule GLP-1 receptor agonists that represent a series that parallels the recently reported clinical candidate danuglipron. In the event, identification of a benzyloxypyrimidine lead, using a sensitized high-throughput GLP-1 agonist assay, was followed by optimization of the SAR using substituent modifications analogous to those discovered in the danuglipron series. A new series of 6-azaspiro[2.5]octane molecules was optimized into potent GLP-1 agonists. Information gleaned from cryogenic electron microscope structures was used to rationalize the SAR of the optimized compounds.

Preparation of Azinones from (Cyclopropylmethoxy)azine Ethers.

A general and convenient procedure for the synthesis of azinones is presented. Cyclopropylmethanol is readily introduced onto various azines where it functions as both a protecting group and surrogate for hydroxyl. After acidic deprotection, under mild reaction conditions, the corresponding azinones are formed and isolated in excellent yields. >20 examples are included along with a discussion of reaction optimization, scope, and mechanism.

A General Synthesis of Dihydronaphthyridinones with Aryl-Substituted Quaternary Benzylic Centers.

A variety of 7,8-dihydro-1,6-naphthyridin-5(6H)-ones and 3,4-dihydro-2,7-naphthyridin-1(2H)-ones with quaternary centers and aryl substitutions at the benzylic carbon were synthesized with a new 3-step, 2-pot method. The first step is an SNAr using widely available 2- and 4-chloronicotinate esters and tertiary benzylic nitriles. The last two steps are a one-pot selective nitrile reduction in the presence of various heterocycles followed by a lactam ring closure of the free amine on the ester.

Cutaneous lupus-erythematosus-like reaction arising after COVID-19 vaccination.

Multiple adverse cutaneous reactions have been described following vaccination against COVID-19. This case report describes a reaction to the Pfizer-BioNTech (BNT162b2) vaccine that histopathologically resembles cutaneous lupus erythematosus with vacuolar interface alteration, superficial to mid-dermal perivascular and periadnexal lymphocytic infiltrate with clusters of CD123+ cells, and mildly increased dermal mucin.

Design and Identification of a Novel, Functionally Subtype Selective GABAA Positive Allosteric Modulator (PF-06372865).

The design, optimization, and evaluation of a series of novel imidazopyridazine-based subtype-selective positive allosteric modulators (PAMs) for the GABAA ligand-gated ion channel are described. From a set of initial hits multiple subseries were designed and evaluated based on binding affinity and functional activity. As designing in the desired level of functional selectivity proved difficult, a probability-based assessment was performed to focus the project's efforts on a single subseries that had the greatest odds of delivering the target profile. These efforts ultimately led to the identification of two precandidates from this subseries, which were advanced to preclinical safety studies and subsequently to the identification of the clinical candidate PF-06372865.

Highly potent and selective NaV1.7 inhibitors for use as intravenous agents and chemical probes.

The discovery and selection of a highly potent and selective NaV1.7 inhibitor PF-06456384, designed specifically for intravenous infusion, is disclosed. Extensive in vitro pharmacology and ADME profiling followed by in vivo preclinical PK and efficacy model data are discussed. A proposed protein-ligand binding mode for this compound is also provided to rationalise the high levels of potency and selectivity over inhibition of related sodium channels. To further support the proposed binding mode, potent conjugates are described which illustrate the potential for development of chemical probes to enable further target evaluation.

One-Pot Synthesis of α-Branched N-Acylamines via Titanium-Mediated Condensation of Amides, Aldehydes, and Organometallics.

A three-component, titanium-mediated synthesis of α-branched N-acylamines from commercial or readily accessible amides, aldehydes, and organometallic reagents is reported. The transformation proceeds under mild reaction conditions and tolerates a variety of functional groups (including nitrile, carbamate, olefin, basic amine, furan, and other sensitive heteroaromatics) to generate a large umbrella of α-branched N-acylamine products in high yields. The operationally practical procedure enables the use of this method in parallel chemical synthesis, a valuable feature that can facilitate the screening of bioactive molecules by medicinal chemists.

Practical synthesis of capromorelin, a growth hormone secretagogue, via a crystallization-induced dynamic resolution.

A practical synthesis of capromorelin (1), a growth hormone secretagogue, is described that utilizes as a key step a crystallization-induced dynamic resolution (CIDR) of (±)-3a-benzyl-2-methyl-4,5,6,7-tetrahydro-2H-pyrazolo[4,3-c]pyridin-3(3aH)-one [(±)-2] by L-tartaric acid salt formation, yielding (R)-2.L-tartaric acid in high chemical yield (>85%) and with diastereomeric excess (de) of ∼98%. Treatment of (R)-2.L-tartaric acid with ammonium hydroxide provided (R)-2 without loss of chiral purity. In situ generated (R)-2 was coupled with (R)-3-(benzyloxy)-2-(2-(tert-butoxycarbonyl)-2-methylpropanamido)propanoic acid [(R)-3] to give predominantly a single diastereomer of N-Boc-protected capromorelin [(1R,3aR)-4]. This process was used to prepare bulk quantities of capromorelin from (±)-2 to support preclinical toxicology studies.

Discovery and Preclinical Characterization of 6-Chloro-5-[4-(1-hydroxycyclobutyl)phenyl]-1H-indole-3-carboxylic Acid (PF-06409577), a Direct Activator of Adenosine Monophosphate-activated Protein Kinase (AMPK), for the Potential Treatment of Diabetic Nephropathy.

Adenosine monophosphate-activated protein kinase (AMPK) is a protein kinase involved in maintaining energy homeostasis within cells. On the basis of human genetic association data, AMPK activators were pursued for the treatment of diabetic nephropathy. Identification of an indazole amide high throughput screening (HTS) hit followed by truncation to its minimal pharmacophore provided an indazole acid lead compound. Optimization of the core and aryl appendage improved oral absorption and culminated in the identification of indole acid, PF-06409577 (7). Compound 7 was advanced to first-in-human trials for the treatment of diabetic nephropathy.

The Synthesis of Methyl-Substituted Spirocyclic Piperidine-Azetidine (2,7-Diazaspiro[3.5]nonane) and Spirocyclic Piperidine-Pyrrolidine (2,8-Diazaspiro[4.5]decane) Ring Systems.

The synthesis of a series of pharmaceutically important N-protected methyl-substituted spirocyclic piperidine-azetidine (2,7-diazaspiro[3.5]nonane) and spirocyclic piperidine-pyrrolidine (2,8-diazaspiro[4.5]decane) ring systems was developed. These motifs contain two differentiated sites (protected secondary amines) to allow for further functionalization via reductive amination, amidation, or other chemistry. The methyl-substituted spiroazetidine ring systems were accessed using nitrile lithiation/alkylation chemistry while the methyl-substituted spiropyrrolidines were synthesized by 1,4-addition reactions with nitroalkanes, followed by reduction and cyclization. These conditions were then scaled for the synthesis of 1-methyl spirocyclic piperidine-pyrrolidine with a classical resolution of the product using a tartaric acid derivative to isolate a single enantiomer.

Design and development of histone deacetylase (HDAC) chemical probes for cell-based profiling.

Histone deacetylases (HDACs) contribute to regulation of gene expression by mediating higher-order chromatin structures. They assemble into large multiprotein complexes that regulate activity and specificity. We report the development of small molecule probes with class IIa and pan-HDAC activity that contain photoreactive crosslinking groups and either a biotin reporter, or a terminal alkyne handle for subsequent bioorthogonal ligation. The probes retained inhibitory activity against recombinant HDAC proteins and caused an accumulation of acetylated histone and tubulin following cell treatment. The versatility of the probes has been demonstrated by their ability to photoaffinity modify HDAC targets in vitro. An affinity enrichment probe was used in conjunction with mass spectrometry proteomics to isolate HDACs and their interacting proteins in a native proteome. The performance of the probes in recombinant versus cell-based systems highlights issues for the development of chemoproteomic technologies targeting class IIa HDACs in particular.

Discovery of spirocyclic-diamine inhibitors of mammalian acetyl CoA-carboxylase.

A novel series of spirocyclic-diamine based, isoform non-selective inhibitors of acetyl-CoA carboxylase (ACC) is described. These spirodiamine derivatives were discovered by design of a library to mimic the structural rigidity and hydrogen-bonding pattern observed in the co-crystal structure of spirochromanone inhibitor I. The lead compound 3.5.1 inhibited de novo lipogenesis in rat hepatocytes, with an IC50 of 0.30 µM.

Evaluation and synthesis of polar aryl- and heteroaryl spiroazetidine-piperidine acetamides as ghrelin inverse agonists.

Several polar heteroaromatic acetic acids and their piperidine amides were synthesized and evaluated as ghrelin or type 1a growth hormone secretagogue receptor (GHS-R1a) inverse agonists. Efforts to improve pharmacokinetic and safety profile was achieved by modulating physicochemical properties and, more specifically, emphasizing increased polarity of our chemical series. ortho-Carboxamide containing compounds provided optimal physicochemical, pharmacologic, and safety profile. pH-dependent chemical stability was also assessed with our series.

Discovery of PF-5190457, a Potent, Selective, and Orally Bioavailable Ghrelin Receptor Inverse Agonist Clinical Candidate.

The identification of potent, highly selective orally bioavailable ghrelin receptor inverse agonists from a spiro-azetidino-piperidine series is described. Examples from this series have promising in vivo pharmacokinetics and increase glucose-stimulated insulin secretion in human whole and dispersed islets. A physicochemistry-based strategy to increase lipophilic efficiency for ghrelin receptor potency and retain low clearance and satisfactory permeability while reducing off-target pharmacology led to the discovery of 16h. Compound 16h has a superior balance of ghrelin receptor pharmacology and off-target selectivity. On the basis of its promising pharmacological and safety profile, 16h was advanced to human clinical trials.

Diastereoselective synthesis of ß-heteroaryl syn-α-methyl-ß-amino acid derivatives via a double chiral auxiliary approach.

The addition of the SuperQuat enolate to five- and six-membered heterocyclic tert-butyl sulfinimines led to a high syn-selectivity of up to 99:1 in good to excellent yields. The reaction is tentatively proposed to proceed through an open-chain transition state with the presence of an α-heteroatom on the sulfinimine leading to high diastereoselectivities. The adducts were derivatized to ß-amino esters and amides in a facile manner.

Identification of spirocyclic piperidine-azetidine inverse agonists of the ghrelin receptor.

The discovery of spirocyclic piperidine-azetidine inverse agonists of the ghrelin receptor is described. The characterization and redressing of the issues associated with these compounds is detailed. An efficient three-step synthesis and a binding assay were relied upon as the primary means of rapidly improving potency and ADMET properties for this class of inverse agonist compounds. Compound 10 n bearing distributed polarity in the form of an imidazo-thiazole acetamide and a phenyl triazole is a unit lower in logP and has significantly improved binding affinity compared to the hit molecule 10a, providing support for further optimization of this series of compounds.

Synthesis of 7-oxo-dihydrospiro[indazole-5,4'-piperidine] acetyl-CoA carboxylase inhibitors.

Synthesis of oxo-dihydrospiroindazole-based acetyl-CoA carboxylase (ACC) inhibitors is reported. The dihydrospiroindazoles were assembled in a regioselective manner in six steps from substituted hydrazines and protected 4-formylpiperidine. Enhanced regioselectivity in the condensation between a keto enamine and substituted hydrazines was observed when using toluene as the solvent, leading to selective formation of 1-substituted spiroindazoles. The 2-substituted spiroindazoles were formed selectively from alkyl hydrazones by ring closure with Vilsmeier reagent. The key step in the elaboration to the final products is the conversion of an intermediate olefin to the desired ketone through elimination of HBr from an O-methyl bromohydrin. This methodology enabled the synthesis of each desired regioisomer on 50-75 g scale with minimal purification. Acylation of the resultant spirocyclic amines provided potent ACC inhibitors.