Kenneth A. Newlander

Identification of Potent, Selective, Cell-Active Inhibitors of the Histone Lysine Methyltransferase EZH2.

The histone H3-lysine 27 (H3K27) methyltransferase EZH2 plays a critical role in regulating gene expression, and its aberrant activity is linked to the onset and progression of cancer. As part of a drug discovery program targeting EZH2, we have identified highly potent, selective, SAM-competitive, and cell-active EZH2 inhibitors, including GSK926 (3) and GSK343 (6). These compounds are small molecule chemical tools that would be useful to further explore the biology of EZH2.

Discovery of a Novel and Potent Class of FabI-Directed Antibacterial Agents

ABSTRACT Bacterial enoyl-acyl carrier protein (ACP) reductase (FabI) catalyzes the final step in each elongation cycle of bacterial fatty acid biosynthesis and is an attractive target for the development of new antibacterial agents. High-throughput screening of the Staphylococcus aureus FabI enzyme identified a novel, weak inhibitor with no detectable antibacterial activity against S. aureus. Iterative medicinal chemistry and X-ray crystal structure-based design led to the identification of compound 4 [(E)-N-methyl-N-(2-methyl-1H-indol-3-ylmethyl)-3-(7-oxo-5,6,7,8-tetrahydro-1,8-naphthyridin-3-yl)acrylamide], which is 350-fold more potent than the original lead compound obtained by high-throughput screening in the FabI inhibition assay. Compound 4 has exquisite antistaphylococci activity, achieving MICs at which 90% of isolates are inhibited more than 500 times lower than those of nine currently available antibiotics against a panel of multidrug-resistant strains of S. aureus and Staphylococcus epidermidis. Furthermore, compound 4 exhibits excellent in vivo efficacy in an S. aureus infection model in rats. Biochemical and genetic approaches have confirmed that the mode of antibacterial action of compound 4 and related compounds is via inhibition of FabI. Compound 4 also exhibits weak FabK inhibitory activity, which may explain its antibacterial activity against Streptococcus pneumoniae and Enterococcus faecalis, which depend on FabK and both FabK and FabI, respectively, for their enoyl-ACP reductase function. These results show that compound 4 is representative of a new, totally synthetic series of antibacterial agents that has the potential to provide novel alternatives for the treatment of S. aureus infections that are resistant to our present armory of antibiotics.

Defining and Combating the Mechanisms of Triclosan Resistance in Clinical Isolates of Staphylococcus aureus

ABSTRACT The MICs of triclosan for 31 clinical isolates of Staphylococcus aureus were 0.016 μg/ml (24 strains), 1 to 2 μg/ml (6 strains), and 0.25 μg/ml (1 strain). All the strains for which triclosan MICs were elevated (>0.016 μg/ml) showed three- to fivefold increases in their levels of enoyl-acyl carrier protein (ACP) reductase (FabI) production. Furthermore, strains for which triclosan MICs were 1 to 2 μg/ml overexpressed FabI with an F204C alteration. Binding studies with radiolabeled NAD+ demonstrated that this change prevents the formation of the stable triclosan-NAD+-FabI complex, and both this alteration and its overexpression contributed to achieving MICs of 1 to 2 μg/ml for these strains. Three novel, potent inhibitors of FabI (50% inhibitory concentrations, ≤64 nM) demonstrated up to 1,000-fold better activity than triclosan against the strains for which triclosan MICs were elevated. None of the compounds tested from this series formed a stable complex with NAD+-FabI. Consequently, although the overexpression of wild-type FabI gave rise to an increase in the MICs, as expected, overexpression of FabI with an F204C alteration did not cause an additional increase in resistance. Therefore, this work identifies the mechanisms of triclosan resistance in S. aureus, and we present three compounds from a novel chemical series of FabI inhibitors which have excellent activities against both triclosan-resistant and -sensitive clinical isolates of S. aureus.

Inhibitors of bacterial enoyl acyl carrier protein reductase (FabI): 2,9-disubstituted 1,2,3,4-tetrahydropyrido[3,4-b]indoles as potential antibacterial agents

An SAR study of a screening lead has led to the identification of 2,9-disubstituted 1,2,3,4-tetrahydropyrido[3,4-b]indoles as inhibitors of Staphylococcus aureus enoyl acyl carrier protein reductase (FabI).

Enantiospecific synthesis of SB 214857, a potent, orally active, nonpeptide fibrinogen receptor antagonist

Abstract An enantiospecific synthesis of SB 214857, a potent, nonpeplide fibrinogen receptor antagonist, is reported. The synthetic route employs as a key step an intramolecular aryl fluoride displacement to form the sevenmembered ring of the 1,4-benzodiazepine system.

The use of γ-turn mimetics to define peptide secondary structure

Abstract A novel γ-turn mimetic 2 has been prepared based on retro amide peptide design. Incorporation of this mimetic into linear peptide fibrinogen receptor antagonist 7 (GPIIb/IIIa receptor) affords the opportunity to test models of antagonist pharmacophore.

Orally bioavailable nonpeptide vitronectin receptor antagonists with efficacy in an osteoporosis model

A new series of potent nonpeptide vitronectin receptor antagonists, based on a novel carbocyclic Gly-Asp mimetic, has been discovered. A representative of this series, SB 265123 (4), has 100% oral bioavailability in rats, and is orally active in vivo in the ovariectomized rat model of osteoporosis.

Synthesis of a 2-benzazepine analog of a potent, nonpeptide GPIIb/IIIa antagonist

Abstract The preparation of the 2-benzazepine derivative 3 as an analog of the potent, nonpeptide GPIIb/IIIa antagonist 2 is reported. The synthetic route employs as key steps a Heck arylation of dimethyl itaconate and a selective cyclization to form the aryl-fused seven-membered ring.

Structure-activity relationships in 3-oxo-1,4-benzodiazepine-2-acetic acid GPIIb/IIIa antagonists. The 2-benzazepine series

Abstract In an investigation of the contribution of N-1 to the binding, antiaggregatory, and oral activity in 3-oxo-1,4-benzodiazepine-2-acetic acid based GPIIb/IIIa antagonists, a series of 2-benzazepine analogs, wherein N-1 of the 1,4-benzodiazepine nucleus has been replaced by a methylene group, was examined.

A trans olefin replacement of the disulfide bridge found in cyclic peptides: synthesis of 6,6-pentamethylene-2-amino-Δ4,5-suberic acid.

Abstract Substitution of the sulfur atoms in the disulfide bridge of cyclic peptides with a trans olefin incorporates the features of a dicarba replacement while introducing a greater torsional restriction The synthesis of the differentially protected racemic 6,6-pentamethylene-2-amino-Δ4,5-suberic acid (2) is described as an example of such a replacement.