Brian W. Dymock

NVP-AUY922: A Novel Heat Shock Protein 90 Inhibitor Active against Xenograft Tumor Growth, Angiogenesis, and Metastasis

We describe the biological properties of NVP-AUY922, a novel resorcinylic isoxazole amide heat shock protein 90 (HSP90) inhibitor. NVP-AUY922 potently inhibits HSP90 (K(d) = 1.7 nmol/L) and proliferation of human tumor cells with GI(50) values of approximately 2 to 40 nmol/L, inducing G(1)-G(2) arrest and apoptosis. Activity is independent of NQO1/DT-diaphorase, maintained in drug-resistant cells and under hypoxic conditions. The molecular signature of HSP90 inhibition, comprising induced HSP72 and depleted client proteins, was readily demonstrable. NVP-AUY922 was glucuronidated less than previously described isoxazoles, yielding higher drug levels in human cancer cells and xenografts. Daily dosing of NVP-AUY922 (50 mg/kg i.p. or i.v.) to athymic mice generated peak tumor levels at least 100-fold above cellular GI(50). This produced statistically significant growth inhibition and/or regressions in human tumor xenografts with diverse oncogenic profiles: BT474 breast tumor treated/control, 21%; A2780 ovarian, 11%; U87MG glioblastoma, 7%; PC3 prostate, 37%; and WM266.4 melanoma, 31%. Therapeutic effects were concordant with changes in pharmacodynamic markers, including induction of HSP72 and depletion of ERBB2, CRAF, cyclin-dependent kinase 4, phospho-AKT/total AKT, and hypoxia-inducible factor-1alpha, determined by Western blot, electrochemiluminescent immunoassay, or immunohistochemistry. NVP-AUY922 also significantly inhibited tumor cell chemotaxis/invasion in vitro, WM266.4 melanoma lung metastases, and lymphatic metastases from orthotopically implanted PC3LN3 prostate carcinoma. NVP-AUY922 inhibited proliferation, chemomigration, and tubular differentiation of human endothelial cells and antiangiogenic activity was reflected in reduced microvessel density in tumor xenografts. Collectively, the data show that NVP-AUY922 is a potent, novel inhibitor of HSP90, acting via several processes (cytostasis, apoptosis, invasion, and angiogenesis) to inhibit tumor growth and metastasis. NVP-AUY922 has entered phase I clinical trials.

Combining Hit Identification Strategies: Fragment- Based and in Silico Approaches to Orally Active 2-Aminothieno[2,3-D]Pyrimidine Inhibitors of the Hsp90 Molecular Chaperone.

Inhibitors of the Hsp90 molecular chaperone are showing considerable promise as potential molecular therapeutic agents for the treatment of cancer. Here we describe novel 2-aminothieno[2,3-d]pyrimidine ATP competitive Hsp90 inhibitors, which were designed by combining structural elements of distinct low affinity hits generated from fragment-based and in silico screening exercises in concert with structural information from X-ray protein crystallography. Examples from this series have high affinity (IC50 = 50-100 nM) for Hsp90 as measured in a fluorescence polarization (FP) competitive binding assay and are active in human cancer cell lines where they inhibit cell proliferation and exhibit a characteristic profile of depletion of oncogenic proteins and concomitant elevation of Hsp72. Several examples (34a, 34d and 34i) caused tumor growth regression at well tolerated doses when administered orally in a human BT474 human breast cancer xenograft model.

Design and characterization of libraries of molecular fragments for use in NMR screening against protein targets

We have designed four generations of a low molecular weight fragment library for use in NMR-based screening against protein targets. The library initially contained 723 fragments which were selected manually from the Available Chemicals Directory. A series of in silico filters and property calculations were developed to automate the selection process, allowing a larger database of 1.79 M available compounds to be searched for a further 357 compounds that were added to the library. A kinase binding pharmacophore was then derived to select 174 kinase-focused fragments. Finally, an additional 61 fragments were selected to increase the number of different pharmacophores represented within the library. All of the fragments added to the library passed quality checks to ensure they were suitable for the screening protocol, with appropriate solubility, purity, chemical stability, and unambiguous NMR spectrum. The successive generations of libraries have been characterized through analysis of structural properties (molecular weight, lipophilicity, polar surface area, number of rotatable bonds, and hydrogen-bonding potential) and by analyzing their pharmacophoric complexity. These calculations have been used to compare the fragment libraries with a drug-like reference set of compounds and a set of molecules that bind to protein active sites. In addition, an analysis of the overall results of screening the library against the ATP binding site of two protein targets (HSP90 and CDK2) reveals different patterns of fragment binding, demonstrating that the approach can find selective compounds that discriminate between related binding sites.

Inhibition of the Heat Shock Protein 90 Molecular Chaperone in Vitro and in Vivo by Novel, Synthetic, Potent Resorcinylic Pyrazole/Isoxazole Amide Analogues.

Although the heat shock protein 90 (HSP90) inhibitor 17-allylamino-17-demethoxygeldanamycin (17-AAG) shows clinical promise, potential limitations encourage development of alternative chemotypes. We discovered the 3,4-diarylpyrazole resorcinol CCT018159 by high-throughput screening and used structure-based design to generate more potent pyrazole amide analogues, exemplified by VER-49009. Here, we describe the detailed biological properties of VER-49009 and the corresponding isoxazole VER-50589. X-ray crystallography showed a virtually identical HSP90 binding mode. However, the dissociation constant (Kd) of VER-50589 was 4.5 ± 2.2 nmol/L compared with 78.0 ± 10.4 nmol/L for VER-49009, attributable to higher enthalpy for VER-50589 binding. A competitive binding assay gave a lower IC50 of 21 ± 4 nmol/L for VER-50589 compared with 47 ± 9 nmol/L for VER-49009. Cellular uptake of VER-50589 was 4-fold greater than for VER-49009. Mean cellular antiproliferative GI50 values for VER-50589 and VER-49009 for a human cancer cell line panel were 78 ± 15 and 685 ± 119 nmol/L, respectively, showing a 9-fold potency gain for the isoxazole. Unlike 17-AAG, but as with CCT018159, cellular potency of these analogues was independent of NAD(P)H:quinone oxidoreductase 1/DT-diaphorase and P-glycoprotein expression. Consistent with HSP90 inhibition, VER-50589 and VER-49009 caused induction of HSP72 and HSP27 alongside depletion of client proteins, including C-RAF, B-RAF, and survivin, and the protein arginine methyltransferase PRMT5. Both caused cell cycle arrest and apoptosis. Extent and duration of pharmacodynamic changes in an orthotopic human ovarian carcinoma model confirmed the superiority of VER-50589 over VER-49009. VER-50589 accumulated in HCT116 human colon cancer xenografts at levels above the cellular GI50 for 24 h, resulting in 30% growth inhibition. The results indicate the therapeutic potential of the resorcinylic pyrazole/isoxazole amide analogues as HSP90 inhibitors. [Mol Cancer Ther 2007;6(4):1198–211]

Discovery of the Macrocycle 11-(2-Pyrrolidin-1-yl-ethoxy)-14, 19-dioxa-5,7,26-triaza-tetracyclo[19.3.1.1(2,6).1(8,12)]heptacosa-1(25),2(26),3,5,8,10,12(27),16,21,23-decaene (SB1518), a Potent Janus Kinase 2/Fms-Like Tyrosine Kinase-3 (JAK2/FLT3) Inhibitor for the Treatment of Myelofibrosis and Lymphoma

Discovery of the activating mutation V617F in Janus Kinase 2 (JAK2(V617F)), a tyrosine kinase critically involved in receptor signaling, recently ignited interest in JAK2 inhibitor therapy as a treatment for myelofibrosis (MF). Herein, we describe the design and synthesis of a series of small molecule 4-aryl-2-aminopyrimidine macrocycles and their biological evaluation against the JAK family of kinase enzymes and FLT3. The most promising leads were assessed for their in vitro ADME properties culminating in the discovery of 21c, a potent JAK2 (IC(50) = 23 and 19 nM for JAK2(WT) and JAK2(V617F), respectively) and FLT3 (IC(50) = 22 nM) inhibitor with selectivity against JAK1 and JAK3 (IC(50) = 1280 and 520 nM, respectively). Further profiling of 21c in preclinical species and mouse xenograft and allograft models is described. Compound 21c (SB1518) was selected as a development candidate and progressed into clinical trials where it is currently in phase 2 for MF and lymphoma.

DNA gyrase (GyrB)/topoisomerase IV (ParE) inhibitors: synthesis and antibacterial activity.

The synthesis and antibacterial activities of three chemotypes of DNA supercoiling inhibitors based on imidazolo[1,2-a]pyridine and [1,2,4]triazolo[1,5-a]pyridine scaffolds that target the ATPase subunits of DNA gyrase and topoisomerase IV (GyrB/ParE) is reported. The most potent scaffold was selected for optimization leading to a series with potent Gram-positive antibacterial activity and a low resistance frequency.

New patented histone deacetylase inhibitors

Importance of the field: Following FDA approval of vorinostat in 2006, several novel HDAC inhibitors (HDACis) have entered clinical trials, and there are numerous published patent applications claiming novel HDACis which were optimized as potential drug candidates, designed for regional or systemic release, and created as dual or multifunctional inhibitors. Given the breadth and depth of recent reporting of novel HDACis, there has emerged a need to review the field from a chemists perspective in one compact article. Areas covered in this review: This review provides a summary of published patent applications claiming novel HDACis from 2007 until mid-2009, covering mainly classes I, II and IV anticancer HDACis including those that have recently advanced to the clinic. What the reader will gain: Readers will rapidly gain an overview of the majority of HDACi scaffolds with representative structure–activity relationships; they will learn how these new compounds were created, how their drug like properties were improved and which companies are the main players in the field. Take home message: Although competition in this field is intense, the future application of HDACis to treat human disease either as single agents or in combination with existing drugs holds real promise.

Preclinical pharmacokinetics and metabolism of a novel diaryl pyrazole resorcinol series of heat shock protein 90 inhibitors

CCT018159 was recently identified as a novel inhibitor of heat shock protein (Hsp) 90, a promising target for cancer therapy. Pharmacokinetic and metabolic properties are likely to be important for efficacy and need to be optimized during drug development. Here, we define the preclinical metabolism and pharmacokinetics of CCT018159 and some early derivatives. In addition, we assess in vitro metabolic stability screening and in vivo cassette dosing (simultaneous administration of several compounds to a single animal) as approaches to investigate these compounds. The plasma clearance following individual i.v. administration to mice was rapid (0.128–0.816 L/h), exceeding hepatic blood flow. For CCT066950 and CCT066952, this could be attributed in part to extensive (>80%) blood cell binding. Oral bioavailability ranged from 1.8% to 29.6%. Tissue distribution of CCT066952 was rapid and moderate, and renal excretion of the compounds was minimal (<1% of dose excreted). Compounds underwent rapid glucuronidation both in vivo and following incubation with mouse liver microsomes. However, whereas CCT066965 was metabolized to the greatest extent in vitro, this compound displayed the slowest plasma clearance. The rank order of the compounds from the highest to lowest area under the curve was the same following discrete and cassette dosing. Furthermore, pharmacokinetic variables were similar whether the compounds were dosed alone or in combination. We conclude that the pharmacokinetics of CCT018159 are complex. Cassette dosing is currently the best option available to assess the pharmacokinetics of this promising series of compounds in relatively high throughput and is now being applied to identify compounds with optimal pharmacokinetic properties during structural analogue synthesis. [Mol Cancer Ther 2006;5(6):1628–37]

Discovery of (2E)-3-{2-Butyl-1-[2-(diethylamino)ethyl]-1H-benzimidazol-5-yl}-N-hydroxyacrylamide (SB939), an Orally Active Histone Deacetylase Inhibitor with a Superior Preclinical Profile

A series of 3-(1,2-disubstituted-1H-benzimidazol-5-yl)-N-hydroxyacrylamides (1) were designed and synthesized as HDAC inhibitors. Extensive SARs have been established for in vitro potency (HDAC1 enzyme and COLO 205 cellular IC(50)), liver microsomal stability (t(1/2)), cytochrome P450 inhibitory (3A4 IC(50)), and clogP, among others. These parameters were fine-tuned by carefully adjusting the substituents at positions 1 and 2 of the benzimidazole ring. After comprehensive in vitro and in vivo profiling of the selected compounds, SB939 (3) was identified as a preclinical development candidate. 3 is a potent pan-HDAC inhibitor with excellent druglike properties, is highly efficacious in in vivo tumor models (HCT-116, PC-3, A2780, MV4-11, Ramos), and has high and dose-proportional oral exposures and very good ADME, safety, and pharmaceutical properties. When orally dosed to tumor-bearing mice, 3 is enriched in tumor tissue which may contribute to its potent antitumor activity and prolonged duration of action. 3 is currently being tested in phase I and phase II clinical trials.

Inhibitors of JAK2 and JAK3: an update on the patent literature 2010 – 2012

Introduction: Janus kinases (JAKs) comprise a family of four enzymes, JAK1, JAK2, JAK3 and tyrosine kinase 2 (TYK2), centrally implicated in cell signaling processes important in cancer and immune-inflammatory diseases. Progression in the field has taken a recent step forward with the approval of ruxolitinib (Jakafi), a selective inhibitor of JAK1/2 and very recently tofacitinib (Xeljanz), a pan-JAK inhibitor. There are many new JAK family enzyme inhibitors in the clinic now with a range of selectivity profiles. More selective JAK2 or JAK3 compounds are now coming through in considerable numbers and this review attempts to provide an update of the recent patent literature of those new compounds. An overview is given on the diversity of core structures employed for inhibitor design showing that the vast majority of compounds are based on classic ATP-competitive kinase inhibitor heterocycles. Areas covered: This review updates new patents claiming JAK2 and/or JAK3 inhibitors published from 2010 to 2012. Pre-2010 patents have been extensively covered in previous reviews. Comments on the context of each chemical series are given where applicable to orientate the readers on the bewildering array of molecular designs now available. This review does not cover JAK1 or TYK2 inhibitors but mention is made of these where they occur within series of JAK2/3 inhibitors. Given the overlap between many pharmacophores, it was not possible to completely separate inhibitors of JAK2 from JAK3, hence the material is organized by JAK2, JAK3 and JAK2/3 and within each section by alphabetical order of the patent assignee, some companies having published five or more patents, such as Ambit (10), Incyte (9), Galapagos (7), Almirall (6) and Biocryst (5). A total of 98 patents are reviewed herein. Expert opinion: JAK inhibitor therapy is entering a significant new era with the advent on the market of the JAK1/2 inhibitor ruxolitinib and the pan-JAK inhibitor tofacitinib, with unprecedented speed of development. Selectivity against the four individual JAK family enzymes, JAK1, 2, 3 and TYK2, is now a key goal since they each play subtly different roles in cytokine-induced cell signaling. The future looks bright for patients as many new drugs are being developed and now combinations of JAK inhibitors with other targeted agents are being studied in the clinic. These advances are expected to lead to further significant progress improving patient outcomes and quality of life.