No abstract

The medicinal chemistry and preclinical biology of imidazopyridine-based inhibitors of diacylglycerol acyltransferase 2 (DGAT2) is described. A screening hit 1 with low lipophilic efficiency (LipE) was optimized through two key structural modifications: (1) identification of the pyrrolidine amide group for a significant LipE improvement, and (2) insertion of a sp(3)-hybridized carbon center in the core of the molecule for simultaneous improvement of N-glucuronidation metabolic liability and off-target pharmacology. The preclinical candidate 9 (PF-06424439) demonstrated excellent ADMET properties and decreased circulating and hepatic lipids when orally administered to dyslipidemic rodent models.

First generation EGFR TKIs (gefitinib, erlotinib) provide significant clinical benefit for NSCLC cancer patients with oncogenic EGFR mutations. Ultimately, these patients' disease progresses, often driven by a second-site mutation in the EGFR kinase domain (T790M). Another liability of the first generation drugs is severe adverse events driven by inhibition of WT EGFR. As such, our goal was to develop a highly potent irreversible inhibitor with the largest selectivity ratio between the drug-resistant double mutants (L858R/T790M, Del/T790M) and WT EGFR. A unique approach to develop covalent inhibitors, optimization of reversible binding affinity, served as a cornerstone of this effort. PF-06459988 was discovered as a novel, third generation irreversible inhibitor, which demonstrates (i) high potency and specificity to the T790M-containing double mutant EGFRs, (ii) minimal intrinsic chemical reactivity of the electrophilic warhead, (iii) greatly reduced proteome reactivity relative to earlier irreversible EGFR inhibitors, and (iv) minimal activity against WT EGFR.

Myeloperoxidase (MPO) is a heme peroxidase that catalyzes the production of hypochlorous acid. Clinical evidence suggests a causal role for MPO in various autoimmune and inflammatory disorders including vasculitis and cardiovascular and Parkinson's diseases, implying that MPO inhibitors may represent a therapeutic treatment option. Herein, we present the design, synthesis, and preclinical evaluation of N1-substituted-6-arylthiouracils as potent and selective inhibitors of MPO. Inhibition proceeded in a time-dependent manner by a covalent, irreversible mechanism, which was dependent upon MPO catalysis, consistent with mechanism-based inactivation. N1-Substituted-6-arylthiouracils exhibited low partition ratios and high selectivity for MPO over thyroid peroxidase and cytochrome P450 isoforms. N1-Substituted-6-arylthiouracils also demonstrated inhibition of MPO activity in lipopolysaccharide-stimulated human whole blood. Robust inhibition of plasma MPO activity was demonstrated with the lead compound 2-(6-(5-chloro-2-methoxyphenyl)-4-oxo-2-thioxo-3,4-dihydropyrimidin-1(2H)-yl)acetamide (PF-06282999, 8) upon oral administration to lipopolysaccharide-treated cynomolgus monkeys. On the basis of its pharmacological and pharmacokinetic profile, PF-06282999 has been advanced to first-in-human pharmacokinetic and safety studies.

Recent studies in adipose tissue, pancreas, muscle, and macrophages suggest that MAP4K4, a serine/threonine protein kinase may be a viable target for antidiabetic drugs. As part of the evaluation of MAP4K4 as a novel antidiabetic target, a tool compound, 16 (PF-6260933) and a lead 17 possessing excellent kinome selectivity and suitable properties were delivered to establish proof of concept in vivo. The medicinal chemistry effort that led to the discovery of these lead compounds is described herein together with in vivo pharmacokinetic properties and activity in a model of insulin resistance.

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 offtarget 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.

Mutant epidermal growth factor receptor (EGFR) is a major driver of non-small-cell lung cancer (NSCLC). Marketed first generation inhibitors, such as erlotinib, effect a transient beneficial response in EGFR mutant NSCLC patients before resistance mechanisms render these inhibitors ineffective. Secondary oncogenic EGFR mutations account for approximately 50% of relapses, the most common being the gatekeeper T790M substitution that renders existing therapies ineffective. The discovery of PF-06459988 (1), an irreversible pyrrolopyrimidine inhibitor of EGFR T790M mutants, was recently disclosed.1 Herein, we describe our continued efforts to achieve potency across EGFR oncogenic mutations and improved kinome selectivity, resulting in the discovery of clinical candidate PF-06747775 (21), which provides potent EGFR activity against the four common mutants (exon 19 deletion (Del), L858R, and double mutants T790M/L858R and T790M/Del), selectivity over wild-type EGFR, and desirable ADME properties. Compound 21 is currently being evaluated in phase-I clinical trials of mutant EGFR driven NSCLC.

Takeda G-protein-coupled receptor 5 (TGR5) represents an exciting biological target for the potential treatment of diabetes and metabolic syndrome. A new class of high-throughput screening (HTS)-derived tetrahydropyrido- [4,3-d]pyrimidine amide TGR5 agonists is disclosed. We describe our effort to identify an orally available agonist suitable for assessment of systemic TGR5 agonism. This effort resulted in identification of 16, which had acceptable potency and pharmacokinetic properties to allow for in vivo assessment in dog. A key aspect of this work was the calibration of human and dog in vitro assay systems that could be linked with data from a human ex vivo peripheral blood monocyte assay that expresses receptor at endogenous levels. Potency from the human in vitro assay was also found to correlate with data from an ex vivo human whole blood assay. This calibration exercise provided confidence that 16 could be used to drive plasma exposures sufficient to test the effects of systemic activation of TGR5. KEYWORDS: GPCR, TGR5, agonist, diabetes, GLP-1 T GR5 (Takeda G-protein-coupled receptor 5) is a class A G-protein-coupled receptor (GPCR) expressed in liver, skeletal muscle, intestine, brown adipose tissues, and monocytes. 1−4 Activation of the TGR5 receptor upon ligand binding results in Gα s -coupled activation of adenylate cyclase. The subsequent downstream signaling cascade is believed to drive multiple effects that are cell type-dependent including (1) enhanced glucagon-like peptide-1 (GLP-1) release from intestinal cells potentially offering improved glycemic control through potentiation of glucose-dependent insulin secretion; 5 (2) nuclear effects, such as endothelial nitric oxide synthase activation and increased nitric oxide production in liver cells; 6 and (3) reduction of macrophage inflammation and lipid loading leading to inhibition of atherosclerosis. 7,8 Activation of TGR5 can also induce type 2 iodothyronine deiodinase in brown adipose tissue. In mice, this leads to increased energy expenditure, but the picture is less clear for humans. 9,10 For these reasons, TGR5 agonists may be useful agents to not only treat diabetes with concurrent management of glucose levels and body weight but also potentially address other aspects of metabolic syndrome.Bile acids are the purported endogenous agonists for TGR5. Of the several bile acids that act as ligands, taurine-conjugated lithocholic acid, lithocholic acid, deoxycholic acid, chenodeoxycholic acid, and cholic acid have all been shown to dose dependently induce accumulation of cyclic adenosine 5′-monophosphate (cAMP) in TGR5-transfected Chinese hamster ovary (CHO) cells. 11 Significant effort has been devoted to synthetic bile acids, such as INT-777 (1). 12,13 In addition, several other nonbile acid agonists have been reported in the literature (2−4), 14−16 which offer the potential for higher selectivity over other bile acid-mediated pathways (Figure 1). Previous work with 1 demonstrated in vivo modulation of