Dac M. Dinh

Discovery of (10R)-7-amino-12-fluoro-2,10,16-trimethyl-15-oxo-10,15,16,17-tetrahydro-2H-8,4-(metheno)pyrazolo[4,3-h][2,5,11]-benzoxadiazacyclotetradecine-3-carbonitrile (PF-06463922), a macrocyclic inhibitor of anaplastic lymphoma kinase (ALK) and c-ros oncogene 1 (ROS1) with preclinical brain exposure and broad-spectrum potency against ALK-resistant mutations.

Although crizotinib demonstrates robust efficacy in anaplastic lymphoma kinase (ALK)-positive non-small-cell lung carcinoma patients, progression during treatment eventually develops. Resistant patient samples revealed a variety of point mutations in the kinase domain of ALK, including the L1196M gatekeeper mutation. In addition, some patients progress due to cancer metastasis in the brain. Using structure-based drug design, lipophilic efficiency, and physical-property-based optimization, highly potent macrocyclic ALK inhibitors were prepared with good absorption, distribution, metabolism, and excretion (ADME), low propensity for p-glycoprotein 1-mediated efflux, and good passive permeability. These structurally unusual macrocyclic inhibitors were potent against wild-type ALK and clinically reported ALK kinase domain mutations. Significant synthetic challenges were overcome, utilizing novel transformations to enable the use of these macrocycles in drug discovery paradigms. This work led to the discovery of 8k (PF-06463922), combining broad-spectrum potency, central nervous system ADME, and a high degree of kinase selectivity.

PF-06463922, an ALK/ROS1 Inhibitor, Overcomes Resistance to First and Second Generation ALK Inhibitors in Preclinical Models

We report the preclinical evaluation of PF-06463922, a potent and brain-penetrant ALK/ROS1 inhibitor. Compared with other clinically available ALK inhibitors, PF-06463922 displayed superior potency against all known clinically acquired ALK mutations, including the highly resistant G1202R mutant. Furthermore, PF-06463922 treatment led to regression of EML4-ALK-driven brain metastases, leading to prolonged mouse survival, in a superior manner. Finally, PF-06463922 demonstrated high selectivity and safety margins in a variety of preclinical studies. These results suggest that PF-06463922 will be highly effective for the treatment of patients with ALK-driven lung cancers, including those who relapsed on clinically available ALK inhibitors because of secondary ALK kinase domain mutations and/or brain metastases.

Pioglitazone hydrochloride inhibits cholesterol absorption and lowers plasma cholesterol concentrations in cholesterol-fed rats

Diabetes is associated with altered cholesterol metabolism that may contribute to cardiovascular complications. Treatment of rats with pioglitazone hydrochloride, a novel antidiabetic compound that improves the general response of target cells to insulin, significantly lowered cholesterol levels in rats fed a hypercholesterolemic diet and produced a significant reduction in cholesterol absorption. Drug treatment was ineffective in rats that were not given dietary cholesterol. To determine whether these effects of pioglitazone hydrochloride might be related to the known ability of this compound to improve the response to circulating insulin, similar studies were conducted in streptozocin-induced diabetic rats with and without insulin replacement. Diabetic rats absorbed a greater percentage of dietary cholesterol than control rats. Treatment of insulin-deficient diabetic rats with pioglitazone alone did not affect cholesterol absorption; however, the combination of insulin and pioglitazone was synergistic to lower absorption of cholesterol and circulating cholesterol and triglycerides. Treatment of either normal rats or diabetic rats receiving insulin with pioglitazone hydrochloride produced a twofold decrease in the ratio of total cholesterol to high-density lipoprotein cholesterol. These results suggest that treatments that improve insulin sensitivity may also have a positive impact on coronary artery disease associated with diabetes.

Design of Potent and Selective Inhibitors to Overcome Clinical Anaplastic Lymphoma Kinase Mutations Resistant to Crizotinib.

Crizotinib (1), an anaplastic lymphoma kinase (ALK) receptor tyrosine kinase inhibitor approved by the U.S. Food and Drug Administration in 2011, is efficacious in ALK and ROS positive patients. Under pressure of crizotinib treatment, point mutations arise in the kinase domain of ALK, resulting in resistance and progressive disease. The successful application of both structure-based and lipophilic-efficiency-focused drug design resulted in aminopyridine 8e, which was potent across a broad panel of engineered ALK mutant cell lines and showed suitable preclinical pharmacokinetics and robust tumor growth inhibition in a crizotinib-resistant cell line (H3122-L1196M).

Substituted 4-aminopiperidines having high in vitro affinity and selectivity for the cloned human dopamine D4 receptor

We have discovered two substituted 4-aminopiperidine compounds having high in vitro affinity and selectivity for the human dopamine D1 receptor. Both compounds, 3-ethoxy-N-methyl-N-[1-(phenylmethyl)-4-piperidinyl]-2-pyridinylamine (U-99363E), and its 3-isopropoxy analog (U-101958), were found through a routine receptor binding screen. The determined affinities (Ki) of these compounds for the cloned human dopamine D4 receptor were 2.2 and 1.4 nM, respectively. They exhibited at least 100-fold lower affinities for dopamine D2 and for other dopaminergic, serotonergic and adrenergic receptors. Both compounds were found to antagonize quinpirole-induced mitogenesis in Chinese hamster ovary cells expressing the human dopamine D4 receptor. In spite of their poor metabolic stability and low bioavailability. U-99363E and U-101958 appear to be among the first high-affinity, highly selective dopamine D4 receptor antagonists reported, and may have utility in in vitro investigations requiring selective tagging or blockade of dopamine D4 sites.

Thioether benzenesulfonamide inhibitors of carbonic anhydrases II and IV: Structure-based drug design, synthesis, and biological evaluation

A novel series of potent thioether benzenesulfonamide inhibitors of carbonic anhydrases II and IV was discovered using structure-based drug design. Synthesis, structure-activity relationship, and optimization of physicochemical properties are described. Low nanomolar potency was achieved, and selected compounds with improved thermodynamic solubility showed promising in vitro inhibition of carbonic anhydrase activity in rabbit iris ciliary body homogenate.

Conformationally-restricted cyclic sulfones as potent and selective mTOR kinase inhibitors.

Novel conformationally-restricted mTOR kinase inhibitors with cyclic sulfone scaffold were designed. Synthesis and structure-activity relationship (SAR) studies are described with emphasis on optimization of the mTOR potency and selectivity against class I PI3Kα kinase. PF-05139962 was identified with excellent mTOR biochemical inhibition, cellular potency, kinase selectivity and in vitro ADME properties.

Discovery of N-((3R,4R)-4-Fluoro-1-(6-((3-methoxy-1-methyl-1H-pyrazol-4-yl)amino)-9-methyl-9H-purin-2-yl)pyrrolidine-3-yl)acrylamide (PF-06747775) through Structure-Based Drug Design: A High Affinity Irreversible Inhibitor Targeting Oncogenic EGFR Mutants with Selectivity over Wild-Type EGFR.

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.

Design and Synthesis of Pyridone-Containing 3,4-Dihydroisoquinoline-1(2H)-ones as a Novel Class of Enhancer of Zeste Homolog 2 (EZH2) Inhibitors

A new enhancer of zeste homolog 2 (EZH2) inhibitor series comprising a substituted phenyl ring joined to a dimethylpyridone moiety via an amide linkage has been designed. A preferential amide torsion that improved the binding properties of the compounds was identified for this series via computational analysis. Cyclization of the amide linker resulted in a six-membered lactam analogue, compound 18. This transformation significantly improved the ligand efficiency/potency of the cyclized compound relative to its acyclic analogue. Additional optimization of the lactam-containing EZH2 inhibitors focused on lipophilic efficiency (LipE) improvement, which provided compound 31. Compound 31 displayed improved LipE and on-target potency in both biochemical and cellular readouts relative to compound 18. Inhibitor 31 also displayed robust in vivo antitumor growth activity and dose-dependent de-repression of EZH2 target genes.

Mitotic Checkpoint Kinase Mps1 Has a Role in Normal Physiology which Impacts Clinical Utility

Cell cycle checkpoint intervention is an effective therapeutic strategy for cancer when applied to patients predisposed to respond and the treatment is well-tolerated. A critical cell cycle process that could be targeted is the mitotic checkpoint (spindle assembly checkpoint) which governs the metaphase-to-anaphase transition and insures proper chromosomal segregation. The mitotic checkpoint kinase Mps1 was selected to explore whether enhancement in genomic instability is a viable therapeutic strategy. The basal-a subset of triple-negative breast cancer was chosen as a model system because it has a higher incidence of chromosomal instability and Mps1 expression is up-regulated. Depletion of Mps1 reduces tumor cell viability relative to normal cells. Highly selective, extremely potent Mps1 kinase inhibitors were created to investigate the roles of Mps1 catalytic activity in tumor cells and normal physiology (PF-7006, PF-3837; K i<0.5 nM; cellular IC50 2–6 nM). Treatment of tumor cells in vitro with PF-7006 modulates expected Mps1-dependent biology as demonstrated by molecular and phenotypic measures (reduced pHH3-Ser10 levels, shorter duration of mitosis, micro-nucleation, and apoptosis). Tumor-bearing mice treated with PF-7006 exhibit tumor growth inhibition concomitant with pharmacodynamic modulation of a downstream biomarker (pHH3-Ser10). Unfortunately, efficacy only occurs at drug exposures that cause dose-limiting body weight loss, gastrointestinal toxicities, and neutropenia. Mps1 inhibitor toxicities may be mitigated by inducing G1 cell cycle arrest in Rb1-competent cells with the cyclin-dependent kinase-4/6 inhibitor palbociclib. Using an isogenic cellular model system, PF-7006 is shown to be selectively cytotoxic to Rb1-deficient cells relative to Rb1-competent cells (also a measure of kinase selectivity). Human bone marrow cells pretreated with palbociclib have decreased PF-7006-dependent apoptosis relative to cells without palbociclib pretreatment. Collectively, this study raises a concern that single agent therapies inhibiting Mps1 will not be well-tolerated clinically but may be when combined with a selective CDK4/6 drug.