Pharmacokinetics of thiotepa in high-dose regimens for autologous hematopoietic stem cell transplant in Japanese patients with pediatric tumors or adult lymphoma.

PURPOSE: Thiotepa is used in high-dose chemotherapy (HDT) before autologous hematopoietic stem cell transplantation (HSCT) to treat solid tumors and hematological malignancies. This Phase 1 study was conducted to establish the pharmacokinetics (PK) of thiotepa in a Japanese population. METHODS: HDT/HSCT was performed in pediatric patients (≥ 2 years) with solid tumors or brain tumors (thiotepa 200 mg/m2/day IV-infused over 24 h on HSCT Days - 12, - 11, - 5, and - 4 and melphalan 70 mg/m2/day IV-infused over 1 h on Days - 11, - 5, and - 4) and adult patients (≥ 16 years) with malignant lymphoma (thiotepa 200 mg/m2/day 2-h IV-infusion on HSCT Days - 4 and - 3 plus busulfan 0.8 mg/kg 2-h IV-infusion every 6 h from HSCT Days - 8 to - 5). Pharmacokinetics of thiotepa were assessed following initial dose. Safety and efficacy were also evaluated. RESULTS: Nine pediatric and 10 adult patients were enrolled. Mean volume of distribution (Vz) of thiotepa normalized with body surface area (BSA) was lower for pediatric patients (16.4 L/m2) compared with adult patients (26.4 L/m2) as expected due to the higher specific surface area of children. Clearance and biological half-life were similar between pediatric and adult patients. Two serious adverse events (cardiac arrest and pulmonary edema) were observed. Survival rate (Day 100 post-HSCT) was 77.8% (95% CI 36.5-93.9%) for pediatric patients and 100% for adult patients. CONCLUSION: Thiotepa elimination was comparable in pediatric and adult patients with cancer. Lower Vz in pediatric compared with adult patients was expected. HDT with thiotepa prior to autologous HSCT was well tolerated. STUDY REGISTRATION: Japic CTI-163433.

Crystal structure of enoyl-acyl carrier protein reductase (FabK) from Streptococcus pneumoniae reveals the binding mode of an inhibitor.

Enoyl-acyl carrier protein (ACP) reductases are critical for bacterial type II fatty acid biosynthesis and thus are attractive targets for developing novel antibiotics. We determined the crystal structure of enoyl-ACP reductase (FabK) from Streptococcus pneumoniae at 1.7 A resolution. There was one dimer per asymmetric unit. Each subunit formed a triose phosphate isomerase (TIM) barrel structure, and flavin mononucleotide (FMN) was bound as a cofactor in the active site. The overall structure was similar to the enoyl-ACP reductase (ER) of fungal fatty acid synthase and to 2-nitropropane dioxygenase (2-ND) from Pseudomonas aeruginosa, although there were some differences among these structures. We determined the crystal structure of FabK in complex with a phenylimidazole derivative inhibitor to envision the binding site interactions. The crystal structure reveals that the inhibitor binds to a hydrophobic pocket in the active site of FabK, and this is accompanied by induced-fit movements of two loop regions. The thiazole ring and part of the ureido moiety of the inhibitor are involved in a face-to-face pi-pi stacking interaction with the isoalloxazine ring of FMN. The side-chain conformation of the proposed catalytic residue, His144, changes upon complex formation. Lineweaver-Burk plots indicate that the inhibitor binds competitively with respect to NADH, and uncompetitively with respect to crotonoyl coenzyme A. We propose that the primary basis of the inhibitory activity is competition with NADH for binding to FabK, which is the first step of the two-step ping-pong catalytic mechanism.

Phenylimidazole derivatives as specific inhibitors of bacterial enoyl-acyl carrier protein reductase FabK.

Bacterial enoyl-acyl carrier protein (ACP) reductases (FabI and FabK) catalyze the final step in each cycle of bacterial fatty acid biosynthesis and are attractive targets for the development of new antibacterial agents. Here, we report the development of novel FabK inhibitors with antibacterial activity against Streptococcus pneumoniae. Based on structure-activity relationship (SAR) studies of our screening hits, we have developed novel phenylimidazole derivatives as potent FabK inhibitors.

Phenylimidazole derivatives of 4-pyridone as dual inhibitors of bacterial enoyl-acyl carrier protein reductases FabI and FabK.

FabI and FabK are bacterial enoyl-acyl carrier protein (ACP) reductases that catalyze the final and rate-limiting step of bacterial fatty acid biosynthesis (FAS) and are potential targets of novel antibacterial agents. We have reported 4-pyridone derivative 3 as a FabI inhibitor and phenylimidazole derivative 5 as a FabK inhibitor. Here, we will report phenylimidazole derivatives of 4-pyridone as FabI and FabK dual inhibitors based on an iterative medicinal chemistry and crystallographic study of FabK from Streptococcus pneumoniae/compound 26. A representative compound 6 showed strong FabI inhibitory (IC50 = 0.38 microM) and FabK inhibitory (IC50 = 0.0045 microM) activities with potent antibacterial activity against S. pneumoniae (MIC = 0.5 microg/mL). Since elevated MIC value was observed against S. pneumoniae mutant possessing one amino acid substitution in FabK, the antibacterial activity of the compound was considered to be due to the inhibition of FabK. Moreover, this compound showed no significant cytotoxicity (IC50 > 69 microM). These results support compound 6 as a novel agent for the treatment of bacterial infections.

Phenylimidazole derivatives as new inhibitors of bacterial enoyl-ACP reductase FabK.

Novel FabK inhibitors with antibacterial activity against Streptococcus pneumoniae were synthesized and evaluated. Through SAR studies of our initial hit compound 2-(1H-benz[d]imidazol-2-ylthio)-N-(6-methoxycarbonylbenzo[d]thiazol-2-yl)acetamide, a series of novel phenylimidazole derivatives were discovered as potent FabK inhibitors.

Discovery of 4-Pyridone derivatives as specific inhibitors of enoyl-acyl carrier protein reductase (FabI) with antibacterial activity against Staphylococcus aureus.

4-Pyridone derivatives were identified as potent inhibitors of FabI, the enoyl-acyl carrier protein reductase in Escherichia coli and Staphylococcus aureus. 1-Substituted derivatives of a hit compound exhibited potent antibacterial activities against S. aureus. Target specificity of 4-pyridone derivatives was confirmed by the strong inhibition of lipid synthesis in macromolecular biosynthesis assay and also by the reduced antimicrobial activity against triclosan-resistant S. aureus isolates possessing a point mutation (Ala95Val) in FabI. Two 4-pyridone compounds exhibited strong antibacterial activities against 30 clinical isolates of methicillin-resistant S. aureus (MRSA) with MIC(90) of 0.5 and 2 mug/ml, respectively. Moreover, they retained activity against S. aureus with a mutation affecting FabI residue 204, which was recently found to be associated with triclosan resistance in clinical isolates of S. aureus. In conclusion, we have identified a novel chemical series, 4-pyridone derivatives, as specific inhibitors of FabI with potent antibacterial activity against S. aureus.

4-Pyridone derivatives as new inhibitors of bacterial enoyl-ACP reductase FabI.

Bacterial FAS provides essential fatty acids for use in the assembly of key cellular components. Among them, FabI is an enoyl-ACP reductase which catalyzes the final and rate-limiting step of bacterial FAS. It is a potential target for selective antibacterial action, because it shows low overall sequence homology with mammalian enzymes. Until today, various compounds have been reported as inhibitors of bacterial FabI-inhibitory compounds. To discover novel small-molecular FabI inhibitors, we initially screened our compound library for inhibitory activity toward FabI of Escherichia coli. And discovered 4-pyridone derivatives as a lead compound. Structure optimization studies yielded 4-pyridone derivatives 7n having strong FabI-inhibitory and antibacterial activities against Staphylococcus aureus. There have been no reports concerning 4-pyridone derivatives as FabI inhibitor.

AG205, a novel agent directed against FabK of Streptococcus pneumoniae.

AG205 was identified from high-throughput screening as a potent inhibitor of FabK, the enoyl-ACP reductase in Streptococcus pneumoniae. Specific inhibition of lipid biosynthesis in a macromolecular biosynthesis assay and identification of an Ala141Ser substitution in FabK from spontaneous AG205-resistant mutants indicated that AG205 exerts antibacterial activity against S. pneumoniae through the specific inhibition of FabK.

Crystallization and preliminary X-ray analysis of enoyl-acyl carrier protein reductase (FabK) from Streptococcus pneumoniae.

The enoyl-acyl carrier protein (ACP) reductase from Streptococcus pneumoniae (FabK; EC 1.3.1.9) is responsible for catalyzing the final step in each elongation cycle of fatty-acid biosynthesis. Selenomethionine-substituted FabK was purified and crystallized by the hanging-drop vapour-diffusion method at 277 K. The crystal belongs to space group P2(1), with unit-cell parameters a = 50.26, b = 126.70, c = 53.63 A, beta = 112.46 degrees . Diffraction data were collected to 2.00 A resolution using synchrotron beamline BL32B2 at SPring-8. Two molecules were estimated to be present in the asymmetric unit, with a solvent content of 45.1%.

The FWD1/beta-TrCP-mediated degradation pathway establishes a 'turning off switch' of a Cdc42 guanine nucleotide exchange factor, FGD1.

FWD1/beta-TrCP is the F-box protein that functions as the receptor subunit of the SCF(FWD1/beta-TrCP) ubiquitin ligase and has been shown to be responsible for the degradation of important signaling molecules such as IkappaBs and beta-catenin. Protein substrates of FWD1/beta-TrCP contain a consensus DSGPsiXS motif (where Psi represents a hydrophobic residue and X represents any amino acid). Recognition by FWD1/beta-TrCP requires phosphorylation of the conserved serines in that motif. Here we show that FGD1, a Cdc42 guanine nucleotide exchange factor (GEF), is a novel target of the SCF(FWD1/beta-TrCP) ubiquitin ligase. A mutant FGD1 protein, FGD1(SA), in which both of the critical serine residues in the DSGPsiXS motif have been replaced by alanines, does not interact with FWD1/beta-TrCP and exhibits increased stability. Morphological changes induced by wild-type FGD1 (FGD1(WT)) are reduced by the co-expression of SCF(FWD1/beta-TrCP) whereas those induced by FGD1(SA) are not affected. FGD1(SA)-expressing cells show a higher level of cell motility than FGD1(WT)-expressing cells. We present a novel 'turning off' mechanism for the inactivation of FGD1, an upstream regulator for Cdc42.

Sulfenamide catalyzed oxidation of alcohols to the corresponding carbonyl compounds with anhydrous chloramine-T.

N-tert-Butylbenzenesulfenamide (1) catalyzed oxidation of various alcohols with stoichiometric amount of anhydrous chloramines-T (2) proceeded smoothly at room temperature to afford the corresponding carbonyl compounds in good yields.