Topoisomerase Inhibitors Addressing Fluoroquinolone Resistance in Gram-Negative Bacteria.

Since their discovery over 5 decades ago, quinolone antibiotics have found enormous success as broad spectrum agents that exert their activity through dual inhibition of bacterial DNA gyrase and topoisomerase IV. Increasing rates of resistance, driven largely by target-based mutations in the GyrA/ParC quinolone resistance determining region, have eroded the utility and threaten the future use of this vital class of antibiotics. Herein we describe the discovery and optimization of a series of 4-(aminomethyl)quinolin-2(1H)-ones, exemplified by 34, that inhibit bacterial DNA gyrase and topoisomerase IV and display potent activity against ciprofloxacin-resistant Gram-negative pathogens. X-ray crystallography reveals that 34 occupies the classical quinolone binding site in the topoisomerase IV-DNA cleavage complex but does not form significant contacts with residues in the quinolone resistance determining region

Discovery of novel 3,5-disubstituted indole derivatives as potent inhibitors of Pim-1, Pim-2 and Pim-3 protein kinases

A series of novel 3,5-disubstituted indole derivatives as potent and selective inhibitors of all three members of the Pim kinase family is described. High throughput screen identified a pan-Pim kinase inhibitor with a promiscuous scaffold. Guided by structure-based drug design, SAR of the series afforded a highly selective indole chemotype that was further developed into a potent set of compounds against Pim-1, 2, and 3 (Pim-1 and Pim-3: IC50 ≤ 2 nM and Pim-2: IC50 ≤ 100 nM)

Design, synthesis and structure activity relationship of potent pan-PIM kinase inhibitors derived from the pyridyl carboxamide scaffold

The Pim proteins (1, 2 and 3) are serine/threonine kinases that have been found to be upregulated in many hematological malignancies and solid tumors. As a result of overlapping functions among the three isoforms, inhibition of all three Pim kinases has become an attractive strategy for cancer therapy. Herein we describe our efforts in identifying potent pan-PIM inhibitors that are derived from our previously reported pyridyl carboxamide scaffold as part of a medicinal chemistry strategy to address metabolic stability

Optimization of a Dibenzodiazepine Hit to a Potent and Selective Allosteric PAK1 Inhibitor

Most kinase inhibitors discovered to date block the ATP binding site which is highly conserved among different kinases and, as a result, such compounds very often suffer from lack of kinase selectivity. Discovery of inhibitors targeting novel allosteric kinase sites is still considered very challenging. In our previous report we described discovery of allosteric inhibitors, such as 1, targeting PAK1 kinase. Herein we report our structure-based optimization strategy yielding highly potent and selective inhibitors of PAK1 such as 2 and 3. Compound 2 was co-crystallized with PAK1 to confirm binding to an allosteric site and to reveal novel key interactions. Compound 3 modulated PAK1 at the cellular level and due to its selectivity enabled valuable research to interrogate biological functions of the PAK1 kinase

Structure Guided Optimization, In Vitro Activity and In Vivo Activity of Pan-PIM Kinase Inhibitors

Proviral Insertion of Moloney virus (PIM) 1, 2 and 3 kinases are serine/threonine kinases that normally function in survival and proliferation of hematopoietic cells. High expression of PIM1, 2 & 3 is frequently observed in many human malignancies, including multiple myeloma, non-Hodgkins lymphoma, and myeloid leukemias. As such, there is interest in determining whether selective PIM inhibition can improve outcomes of these human cancers. Herein, we describe our efforts towards this goal. The structure guided optimization of a singleton high throughput screening hit in which the potency against all three PIM isoforms was increased >10,000 fold to yield compounds with pan PIM Ki’s < 10 picoM is described. During the optimization, a focus was initially placed on increasing potency while simultaneously reducing the liphophilicity and then, from a low logP space, a hydrophobic interaction was optimized. From these efforts, compound 5d was identified with suitable PK properties and kinase selectivity to establish a PK/PD-efficacy relationship in multiple myeloma and acute myeloid leukemia Pim dependent tumor models

Pan-PIM Kinase Inhibition Provides a Novel Therapy for Treating Hematological Cancers

PIM kinases have been shown to act as oncogenes in mice, with each family member being able to drive progression of hematological cancers. Consistent with this, we found that PIMs are highly expressed in human hematological cancers and show that each isoform has a distinct expression pattern among disease subtypes. This suggests that inhibitors of all three PIMs would be effective in treating multiple hematological malignancies. However, Pan-PIM inhibitors have proven difficult to develop because PIM2 has a low Km for ATP and thus requires a very potent inhibitor to effectively block the kinase activity at the ATP levels in cells. Here we describe a potent and specific Pan-PIM inhibitor, LGB321, and demonstrate that it is active on PIM2 in the cellular context of MM where it inhibits proliferation, mTOR-C1 signaling and phosphorylation of BAD. Broad cancer cell line profiling demonstrated that inhibitory activity was almost exclusively observed in cell lines from hematological lineages. Furthermore, we demonstrate LGB321 activity in human cancer cells and xenograft AML mouse models, where modulation of the pharmacodynamics markers could be used to predict efficacy. Our results strongly support the development of Pan-PIM inhibitors to treat hematological malignancies

Design, Structure Activity Relationship and in vivo Characterization of the Clinical Candidate NVP-HSP990

From a commercial hit (1), a novel dihydroquinazolinone scaffold was developed. The SAR of the series was developed which led to the selection of NVP-HSP990 as a clinical candidate

Identification of N-(4-((1R,3S,5S)-3-amino-5-methylcyclohexyl)pyridin-3-yl)-6-(2,6-difluorophenyl)-5-fluoropicolinamide (PIM447), a Potent and Selective Proviral Insertion Site of Moloney Murine Leukemia (PIM) 1,2 and 3 Kinase Inhibitor in Clinical Trials for Hematological Malignancies

Pan Proviral Insertion Site of Moloney Murine Leukemia (PIM) 1, 2 and 3 kinase inhibitors have recently begun to be tested in humans to assess whether pan PIM kinase inhibition may provide benefit to cancer patients. Herein, the synthesis, in vitro activity, in vivo activity in an acute myeloid leukemia xenograft model and pre-clinical profile of the potent and selective pan PIM kinase inhibitor 8 (PIM447) are described. Starting from the reported aminopiperidyl pan PIM kinase inhibitor 1, a strategy to improve the microsomal stability was pursued resulting in the identification of potent aminocyclohexyl pan PIM inhibitors with high metabolic stability. From this aminocyclohexyl series, 8 entered the clinic in 2012 in multiple myeloma patients and is currently in several phase 1 trials of cancer patients with hematological malignancies