Kevin L. Salyers

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.

Antagonism of the osteoclast vitronectin receptor with an orally active nonpeptide inhibitor prevents cancellous bone loss in the ovariectomized rat.

An orally active, nonpeptide Arg‐Gly‐Asp (RGD) mimetic αvβ3 antagonist, (S)‐3‐Oxo‐8‐[2‐[6‐(methylamino)pyridin‐2‐yl]‐1‐ethoxy]‐2‐(2,2,2‐trifluoroethyl)‐2,3,4,5‐tetrahydro‐1H‐2‐benzazepine‐4‐acetic acid (compound 1), has been generated, which prevented net bone loss and inhibited cancellous bone turnover in vivo. The compound binds αvβ3 and the closely related integrin αvβ5 with low nanomolar affinity but binds only weakly to the related integrins αIIbβ3, and α5β1. Compound 1 inhibited αvβ3‐mediated cell adhesion with an IC50 = 3 nM. More importantly, the compound inhibited human osteoclast‐mediated bone resorption in vitro with an IC50 = 11 nM. In vivo, compound 1 inhibited bone resorption in a dose‐dependent fashion, in the acute thyroparathyroidectomized (TPTX) rat model of bone resorption with a circulating EC50 ∼ 20 μM. When dosed orally at 30 mg/kg twice a day (b.i.d.) in the chronic ovariectomy (OVX)‐induced rat model of osteopenia, compound 1 also prevented bone loss. At doses ranging from 3 to 30 mg/kg b.i.d., compound 1 partially prevented the OVX‐induced increase in urinary deoxypyridinoline. In addition, the compound prevented the OVX‐induced reduction in cancellous bone volume (BV), trabecular number (Tb.N), and trabecular thickness (Tb.Th), as assessed by quantitative microcomputerized tomography (μCT) and static histomorphometry. Furthermore, both the 10‐mg/kg and 30‐mg/kg doses of compound prevented the OVX‐induced increase in bone turnover, as measured by percent osteoid perimeter (%O.Pm). Together, these data indicate that the αVβ3 antagonist compound 1 inhibits OVX‐induced bone loss. Mechanistically, compound 1 prevents bone loss in vivo by inhibiting osteoclast‐mediated bone resorption, ultimately preventing cancellous bone turnover.

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.

Phenylbutyrates as potent, orally bioavailable vitronectin receptor (integrin αvβ3) antagonists

In our continuing efforts to identify small molecule vitronectin receptor antagonists, we have discovered a series of phenylbutyrate derivatives, exemplified by 16, which have good potency and excellent oral bioavailability (approximately 100% in rats). This new series is derived conceptually from opening of the seven-membered ring of SB-265123.

Urotensin-II receptor antagonists: Synthesis and SAR of N-cyclic azaalkyl benzamides

SAR exploration of the central diamine, benzyl, and terminal aminoalkoxy regions of the N-cyclic azaalkyl benzamide series led to the identification of very potent human urotensin-II receptor antagonists such as 1a with a K(i) of 4 nM. The synthesis and structure-activity relationships (SAR) of N-cyclic azaalkyl benzamides are described.

SB-242235, a selective inhibitor of p38 mitogen-activated protein kinase. I: preclinical pharmacokinetics.

1. SB-242235 (1-(4-piperidinyl)-4-(4-fluorophenyl)-5-(2-methoxy-4-pyrimidinyl) imidazole) is a potent and selective p38 MAP kinase inhibitor that may be an effective therapy for cytokine-mediated diseases such as autoimmune or inflammatory diseases. The present studies were conducted to evaluate the pharmacokinetics of SB-242235 in several preclinical species, including rat, dog and monkey. 2. SB-242235 demonstrates generally favourable pharmacokinetic properties in all species examined. Systemic plasma clearance was high in rat, but in the non-rodent species SB-242235 demonstrated low to moderate clearance with plasma half-lives > 4 h. Oral bioavailability in each preclinical species was high. In rat and monkey, SB-242235 demonstrated non-linear elimination kinetics that manifested as a decrease in clearance with increasing dose and apparent oral bioavailability >100% at high oral doses. Furthermore, SB-242235 displayed concentration-dependent plasma protein binding over a concentration range of 1000-10,000 ng ml -1. 3. In conclusion, SB-242235 demonstrates high oral bioavailability across the major preclinical species, and may thus be a useful tool compound for investigation of the role of p38 inhibition in various disease states. However, the observations of non-linear protein binding and disposition also suggest the need for caution in the design of and data interpretation from such studies.

Novel inhibitors of the osteoclast specific cysteine protease, cathepsin K

Daniel F. Veber, Dennis S. Yamashita, Hye-Ja Oh, Brian R. Smith, Kevin Salyers, Mark Levy, Chao-Pin Lee, Antonia Marzulli, Phil Smith, Ted Tomaszek, David Tew, Michael McQueney, George B. Stroup, Michael W. Lark, Ian E. James, and Maxine Gowen 6 Department of Medicinal Chemistry, Preclinical Pharmacokinetics, Bioformulations and Drug Delivery, Molecular Recognition, Protein Biochemistry, and Bone & Cartilage Biology, SmithKline Beecham Pharmaceuticals, King of Prussia, PA 19406, U.S.A.