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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 ...

Kinases are principal components of signal transduction pathways and the focus of intense basic and drug discovery research. Irreversible inhibitors that covalently modify non-catalytic cysteines in kinase active-sites have emerged as valuable probes and approved drugs. Many protein classes, however, possess functional cysteines and therefore understanding the proteome-wide selectivity of covalent kinase inhibitors is imperative. Here, we accomplish this objective using activity-based protein profiling coupled with quantitative mass spectrometry to globally map the targets, both specific and non-specific, of covalent kinase inhibitors in human cells. Many of the specific off-targets represent non-kinase proteins that, interestingly, possess conserved, active-site cysteines. We define windows of selectivity for covalent kinase inhibitors and show that, when these windows are exceeded, rampant proteome-wide reactivity and kinase target-independent cell death conjointly occur. Our findings, taken together, provide an experimental roadmap to illuminate opportunities and surmount challenges for the development of covalent kinase inhibitors.

Glucokinase activators are a class of experimental agents under investigation as a therapy for Type 2 diabetes mellitus. An X-ray crystal structure of a modestly potent agent revealed the potential to substitute the common heterocyclic amide donor–acceptor motif for a pyridone moiety. We have successfully demonstrated that both pyridone and pyrimidone heterocycles can be used as a potent donor–acceptor substituent. Several sub-micromolar analogs that possess the desired partial activator profile were synthesized and characterized. Unfortunately, the most potent activators suffered from sub-optimal pharmacokinetic properties. Nonetheless, these donor–acceptor motifs may find utility in other glucokinase activator series or beyond.

N-(Pyridin-2-yl) arylsulfonamides 1 and 2 (PF-915275) were identified as potent inhibitors of 11β-hydroxysteroid dehydrogenase type 1. A screen for bioactivation revealed that these compounds formed glutathione conjugates. This communication presents the results of a risk benefit analysis carried out to progress 2 (PF-915275) to a clinical study and the strategies used to eliminate reactive metabolites in this series of inhibitors. Based on the proposed mechanism of bioactivation and structure-activity relationships, design efforts led to N-(pyridin-2-yl) arylsulfonamides such as 18 and 20 that maintained potent 11β-hydroxysteroid dehydrogenase type 1 activity, showed exquisite pharmacokinetic profiles, and were negative in the reactive metabolite assay.

N-(Pyridin-2-yl) arylsulfonamides are identified as inhibitors of 11β-hydroxysteroid dehydrogenase type 1 (11βHSD1), an enzyme that catalyzes the reduction of the glucocorticoid cortisone to cortisol. Dysregulation of glucocorticoids has been implicated in the pathogenesis of diabetes and the metabolic syndrome. In this Letter, we present the development of an initial lead to an efficient ligand with improved physiochemical properties using a deletion strategy. This strategy allowed for further optimization of potency leading to the discovery of the clinical candidate PF-915275.

Rapid mutations of proteins that are targeted in cancer therapy often lead to drug resistance. Often, the mutation directly affects a drug’s binding site, effectively blocking binding of the drug, but these mutations can have other effects such as changing the protein turnover half-life. Utilizing SILAC MS, we measured the cellular turnover rates of an important non-small cell lung cancer target, epidermal growth factor receptor (EGFR). Wild-type (WT) EGFR, EGFR with a single activating mutant (Del 746–750 or L858R), and the drug-resistant double mutant (L858R/T790M) EGFR were analyzed. In non-small cell lung cancer cell lines, EGFR turnover rates ranged from 28 hours in A431 cells (WT) to 7.5 hours in the PC-9 cells (Del 746–750 mutant). The measurement of EGFR turnover rate in PC-9 cells dosed with irreversible inhibitors has additional complexity due to inhibitor effects on cell viability and results were reported as a range. Finally, essential amino acid recycling (K and R) was measured in different cell lines. The recycling was different in each cell line, but the overall inclusion of the effect of amino acid recycling on calculating EGFR turnover rates resulted in a 10–20% reduction in rates.

Increased incidence of type 2 diabetes mellitus and obesity has elevated the medical need for new agents to treat these disease states. Resistance to the hormones insulin and leptin are hallmarks of both type 2 diabetes and obesity. Drugs that can ameliorate this resistance should be effective in treating type 2 diabetes and possibly obesity. Protein tyrosine phosphatase 1B (PTP1B) is thought to function as a negative regulator of insulin and leptin signal transduction. This article reviews PTP1B as a novel target for type 2 diabetes, and looks at the challenges in developing small-molecule inhibitors of this phosphatase.

The structure-based design, chemical synthesis, and biological evaluation of bicyclic 2-pyridone-containing human rhinovirus (HRV) 3C protease (3CP) inhibitors are described. An optimized compound is shown to exhibit antiviral activity when tested against a variety of HRV serotypes (EC(50)'s ranging from 0.037 to 0.162 microM).

Two 6-month repeat-dose toxicity studies in cynomolgus monkeys illustrated immune complex–mediated adverse findings in individual monkeys and identified parameters that potentially signal the onset of immune complex–mediated reactions following administration of RN6G, a monoclonal antibody (mAb). In the first study, 3 monkeys exhibited nondose-dependent severe clinical signs accompanied by decreased erythrocytes with increased reticulocytes, neutrophilia, monocytosis, thrombocytopenia, coagulopathy, decreased albumin, azotemia, and increased serum levels of activated complement products, prompting unscheduled euthanasia. Histologically, immunohistochemical localization of RN6G was associated with monkey immunoglobulin and complement components in glomeruli and other tissues, attributable to immune complex disease (ICD). All 3 animals also had anti-RN6G antibodies and decreased plasma levels of RN6G. Subsequently, an investigational study was designed and conducted with regulatory agency input to detect early onset of ICD and assess reversibility to support further clinical development. Dosing of individual animals ceased when biomarkers of ICD indicated adverse findings. Of the 12 monkeys, 1 developed anti-RN6G antibodies and decreased RN6G exposure that preceded elevations in complement products, interleukin-6, and coagulation parameters and decreases in albumin and fibrinogen. All findings in this monkey, except for antidrug antibody (ADA), reversed after cessation of dosing without progressing to adverse sequelae typically associated with ICD.

An encoded 13,020-member combinatorial library was synthesized containing a statine core. Evaluation of this library with plasmepsin II, an aspartyl protease required for hemoglobin metabolism in the malaria parasite, led to the identification of potent and selective inhibitors as well as novel structure-activity relationships.

Pteridinones were designed based on a non-selective kinase template. Because of the uniqueness of the PI3K and mTOR binding pockets, a methyl group was introduced to C-4 position of the peteridinone core to give compounds with excellent selectivity for PI3K and mTOR. This series of compounds were further optimized to improve their potency against PI3Kα and mTOR. Finally, orally active compounds with improved solubility and robust in vivo efficacy in tumor growth inhibition were identified as well.

Drug-induced phospholipidosis (PL) is an excessive accumulation of phospholipids and drug in lysosomes. Phospholipidosis signals a change in cell membrane integrity and accumulation of intracellular drug or metabolite in tissues. The sensitivity and susceptibility of preclinical models to detect PL vary with therapeutic agents, and PL is expected to be reversible after discontinuation of drug treatment. The prevailing scientific opinion is that PL by itself is not adverse; however, some regulatory authorities consider PL to be adverse because a small number of chemicals are able to cause PL and concurrent organ toxicity. Until a greater understanding of PL emerges, a well-thought-out risk management strategy for PL will increase confidence in safety and improve selection and development of new drugs. This paper provides a tiered approach to risk management of drug-induced PL. It begins with use of in silico and in vitro tools to design and select compounds with reduced potential to produce PL. Early in vivo studies in two species are used to better characterize potential for toxicity and PL. Finally, routine risk management tools (i.e., translational biomarkers, assessment of reversibility) are used to support confidence in safety of compounds that induce PL in animals.

A structure-based 18,900-member combinatorial library was synthesized containing a statine template and three cyclic diamino acids as potential P1, P2-P4 surrogates. Evaluation of this encoded library against two aspartyl proteases, plasmepsin II and cathepsin D, led to the identification of selective inhibitors for each enzyme.