Discovery of an Atropisomeric PI3Kß Selective Inhibitor through Optimization of the Hinge Binding Motif.

A series of PI3Kß selective inhibitors derived from a novel 4-(1H-benzo[d]imidazol-1-yl)quinoline chemotype has been rationally designed. Crucial to achieving the desired selectivity over the other class I PI3K isoforms, including the challenging δ-isoform, was the identification of a subset of substituted pyridine hinge binders. This work led to the discovery of (P)-14, a highly selective and orally bioavailable PI3Kß inhibitor displaying an excellent pharmacokinetic profile in addition to great cellular potency in various PTEN-deficient tumor cell lines. Results from a dog toxicology study revealing structure-related, off-target ocular toxicity are also briefly discussed.

Leukaemia hijacks a neural mechanism to invade the central nervous system.

Acute lymphoblastic leukaemia (ALL) has a marked propensity to metastasize to the central nervous system (CNS). In contrast to brain metastases from solid tumours, metastases of ALL seldom involve the parenchyma but are isolated to the leptomeninges, which is an infrequent site for carcinomatous invasion. Although metastasis to the CNS occurs across all subtypes of ALL, a unifying mechanism for invasion has not yet been determined. Here we show that ALL cells in the circulation are unable to breach the blood-brain barrier in mice; instead, they migrate into the CNS along vessels that pass directly between vertebral or calvarial bone marrow and the subarachnoid space. The basement membrane of these bridging vessels is enriched in laminin, which is known to coordinate pathfinding of neuronal progenitor cells in the CNS. The laminin receptor α6 integrin is expressed in most cases of ALL. We found that α6 integrin-laminin interactions mediated the migration of ALL cells towards the cerebrospinal fluid in vitro. Mice with ALL xenografts were treated with either a PI3Kδ inhibitor, which decreased α6 integrin expression on ALL cells, or specific α6 integrin-neutralizing antibodies and showed significant reductions in ALL transit along bridging vessels, blast counts in the cerebrospinal fluid and CNS disease symptoms despite minimally decreased bone marrow disease burden. Our data suggest that α6 integrin expression, which is common in ALL, allows cells to use neural migratory pathways to invade the CNS.

Atropisomerism by Design: Discovery of a Selective and Stable Phosphoinositide 3-Kinase (PI3K) ß Inhibitor.

Atropisomerism is a type of axial chirality in which enantiomers or diastereoisomers arise due to hindered rotation around a bond axis. In this manuscript, we report a case in which torsional scan studies guided the thoughtful creation of a restricted axis of rotation between two heteroaromatic systems of a phosphoinositide 3-kinase (PI3K) ß inhibitor, generating a pair of atropisomeric compounds with significantly different pharmacological and pharmacokinetic profiles. Emblematic of these differences, the metabolism of inactive ( M)-28 is primarily due to the cytosolic enzyme aldehyde oxidase, while active ( P)-28 has lower affinity for aldehyde oxidase, resulting in substantially better metabolic stability. Additionally, we report torsional scan and experimental studies used to determine the barriers of rotation of this novel PI3Kß inhibitor.

Discovery of a Phosphoinositide 3-Kinase (PI3K) ß/δ Inhibitor for the Treatment of Phosphatase and Tensin Homolog (PTEN) Deficient Tumors: Building PI3Kß Potency in a PI3Kδ-Selective Template by Targeting Nonconserved Asp856.

Phosphoinositide 3-kinase (PI3K) ß signaling is required to sustain cancer cell growth in which the tumor suppressor phosphatase and tensin homolog (PTEN) has been deactivated. This manuscript describes the discovery, optimization, and in vivo evaluation of a novel series of PI3Kß/δ inhibitors in which PI3Kß potency was built in a PI3Kδ-selective template. This work led to the discovery of a highly selective PI3Kß/δ inhibitor displaying excellent pharmacokinetic profile and efficacy in a human PTEN-deficient LNCaP prostate carcinoma xenograft tumor model.

Discovery of Orally Efficacious Phosphoinositide 3-Kinase δ Inhibitors with Improved Metabolic Stability.

Aberrant signaling of phosphoinositide 3-kinase δ (PI3Kδ) has been implicated in numerous pathologies including hematological malignancies and rheumatoid arthritis. Described in this manuscript are the discovery, optimization, and in vivo evaluation of a novel series of pyridine-containing PI3Kδ inhibitors. This work led to the discovery of 35, a highly selective inhibitor of PI3Kδ which displays an excellent pharmacokinetic profile and is efficacious in a rodent model of rheumatoid arthritis.

2,4,6-Triaminopyrimidine as a Novel Hinge Binder in a Series of PI3Kδ Selective Inhibitors.

Inhibition of phosphoinositide 3-kinase δ (PI3Kδ) is an appealing target for several hematological malignancies and inflammatory diseases. Herein, we describe the discovery and optimization of a series of propeller shaped PI3Kδ inhibitors comprising a novel triaminopyrimidine hinge binder. Combinations of electronic and structural strategies were employed to mitigate aldehyde oxidase mediated metabolism. This medicinal chemistry effort culminated in the identification of 52, a potent and highly selective inhibitor of PI3Kδ that demonstrates efficacy in a rat model of arthritis.

Fosfomycin enhances the active transport of tobramycin in Pseudomonas aeruginosa.

Elevated levels of mucins present in bronchiectatic airways predispose patients to bacterial infections and reduce the effectiveness of antibiotic therapies by directly inactivating antibiotics. Consequently, new antibiotics that are not inhibited by mucins are needed to treat chronic respiratory infections caused by Pseudomonas aeruginosa and Staphylococcus aureus. In these studies, we demonstrate that fosfomycin synergistically enhances the activity of tobramycin in the presence of mucin. The bactericidal killing of a novel 4:1 (wt/wt) combination of fosfomycin-tobramycin (FTI) is superior (>9 log(10) CFU/ml) relative to its individual components fosfomycin and tobramycin. Additionally, FTI has a mutation frequency resulting in an antibiotic resistance >3 log(10) lower than for fosfomycin and 4 log(10) lower than for tobramycin for P. aeruginosa. Mechanistic studies revealed that chemical adducts are not formed, suggesting that the beneficial effects of the combination are not due to molecular modification of the components. FTI displayed time-kill kinetics similar to tobramycin and killed in a concentration-dependent fashion. The bactericidal effect resulted from inhibition of protein biosynthesis rather than cell wall biosynthesis. Studies using radiolabeled antibiotics demonstrated that tobramycin uptake was energy dependent and that fosfomycin enhanced the uptake of tobramycin in P. aeruginosa in a dose-dependent manner. Lastly, mutants resistant to fosfomycin and tobramycin were auxotrophic for specific carbohydrates and amino acids, suggesting that the resistance arises from mutations in specific active transport mechanisms. Overall, these data demonstrate that fosfomycin enhances the uptake of tobramycin, resulting in increased inhibition of protein synthesis and ultimately bacterial killing.

Assays to detect West Nile virus in dead birds.

Using oral swab samples to detect West Nile virus in dead birds, we compared the Rapid Analyte Measurement Platform (RAMP) assay with VecTest and real-time reverse-transcriptase-polymerase chain reaction. The sensitivities of RAMP and VecTest for testing corvid species were 91.0% and 82.1%, respectively.

A prodrug approach toward the development of water soluble fluoroquinolones and structure--activity relationships of quinoline-3-carboxylic acids.

A fluoroquinolone prodrug, PA2808, was prepared and shown to convert to the highly active parent drug PA2789. In vitro and in vivo activation of PA2808 by alkaline phosphatase was demonstrated using disk diffusion and rat lung infection models. The water solubility of PA2808 showed a marked increase compared to PA2789 over a pH range suitable for aerosol drug delivery. A total of 48 analogues based on PA2789 were prepared and screened against a panel of Gram-positive and Gram-negative pathogens. Incorporating a cyclopropane-fused pyrrolidine (amine) at C-7 resulted in some of the most active analogues.

VecTest as diagnostic and surveillance tool for West Nile virus in dead birds.

The VecTest antigen-capture assay for West Nile virus was performed on oral and tissue swabs from dead birds in New York State from April 2003 through July 2004. Results were compared with those from real-time reverse transcriptase-polymerase chain reaction of kidney or brain. Oral VecTest sensitivity is adequate for surveillance in American Crows (Corvus brachyrhynchos) (87%), Blue Jays (Cyanocitta cristata) (80%), and House Sparrows (Passer domesticus) (76%). Oral VecTest performed well for small samples of American Kestrels (Falco sparverius), Northern Cardinals (Cardinalis cardinalis), Common Grackles (Quiscalus quiscula), and House Finches (Carpodacus mexicanus). Poor sensitivity occurred in most raptors, Mourning Doves (Zenaida macroura), Fish Crows (Corvus ossifragus), and American Robins (Turdus migratorius). Specificity was excellent (98%), except for false-positive results that occurred mostly in Gray Catbirds (Dumatella carolinensis), Green Herons (Butorides virescens), and tests of blood and tissues. Feather pulp and kidney may be useful for VecTest assays in corvids.