In vitro activity of isavuconazole against 140 reference fungal strains and 165 clinically isolated yeasts from Japan.

The in vitro susceptibilities of 140 laboratory reference strains of fungi, including type strains, and 165 clinical yeast isolates from Japan towards isavuconazole compared with fluconazole (FLC), itraconazole (ITC), voriconazole and amphotericin B were measured. Broth microdilution methods based on Clinical and Laboratory Standards Institute (CLSI) methods were used for yeasts, and RPMI-MOPS medium semi-solidified with 0.2% low-melting-point agarose based on CLSI guidelines was used for moulds. The range of isavuconazole minimum inhibitory concentrations (MICs) was 0.0004-0.21 mg/L for Candida albicans, 0.0036-0.4 mg/L for Candida glabrata, 0.023-0.058 mg/L for Candida krusei, 0.0026-0.032 mg/L for Cryptococcus neoformans, 0.1-0.39mg/L for Aspergillus fumigatus and 0.2-0.39 mg/L for Aspergillus terreus. Isavuconazole was as active as ITC against the dimorphic true pathogenic fungi, with a range of MICs from <0.0004 mg/L to 0.0063 mg/L for Blastomyces dermatitidis and Histoplasma capsulatum. It was also active against uncommon dematiaceous fungi such as Exophiala spp. and Phialophora spp. as well as against dermatophytic species. Isavuconazole showed very good in vitro antifungal activity with a broad spectrum, including against FLC-resistant Candida spp., Aspergillus spp. and uncommon opportunistic fungal species. This is the first report of the in vitro susceptibility of Japanese clinical yeast isolates to isavuconazole. No cross-resistance was found to isavuconazole amongst FLC-resistant strains.

Synthesis and biological activities of a pH-dependently activated water-soluble prodrug of a novel hexacyclic camptothecin analog.

CH0793076 (1) is a novel hexacyclic camptothecin analog showing potent antitumor activity in various human caner xenograft models. To improve the water solubility of 1, water-soluble prodrugs were designed to generate an active drug 1 nonenzymatically, thus expected to show less interpatient PK variability than CPT-11. Among the prodrugs synthesized, 4c (TP300, hydrochloride) having a glycylsarcosyl ester at the C-20 position of 1 is highly water-soluble (>10mg/ml), stable below pH 4 and rapidly generates 1 at physiological pH in vitro. The rapid (ca. <1min) generation of 1 after incubation of TP300 with plasma (mouse, rat, dog and monkey) was also demonstrated. TP300 showed a broader antitumor spectrum and more potent antitumor activity than CPT-11 in various human cancer xenograft models.

Synthesis of new camptothecin analogs with improved antitumor activities.

Novel hexacyclic camptothecin analogs containing cyclic amidine, urea, or thiourea moiety were designed and synthesized based on the proposed 3D-structure of the topoisomerase I (Topo I)/DNA/camptothecin ternary complex. The analogs were prepared from 9-nitrocamptothecin via 7,9-diaminocamptothecin derivatives as a key intermediate. Among them, 7c exhibited in vivo antitumor activities superior to CPT-11 in human cancer xenograft models in mice at their maximum tolerated doses though its in vitro antiproliferative activity was comparable to SN-38 against corresponding cell lines.

Mechanistic investigation of poly(ethylene imine)-based siRNA delivery: disulfide bonds boost intracellular release of the cargo.

Poly(ethylene imine) (PEI) has gained increasing attention in the delivery of small interfering RNAs (siRNAs) into cells. In order to further optimize PEI for this application, the first goal of this study was to examine particular steps of siRNA delivery with various PEI derivatives as carriers. Furthermore, the hypothesis that disulfide cleavable carrier systems are favorable for the release of siRNA into the cell cytoplasm was investigated. Flow cytometry and confocal microscopy were used to assess the cellular uptake and intracellular distribution of siRNA, which were then related to gene silencing efficacy. We observed a strong correlation between cellular uptake and RNAi activity. The cellular uptake of siRNA was more efficient with increasing branching of the polymer, i.e. linear PEI (lPEI) 5 kDa < lPEI cross-linked via disulfide bonds (ssPEI) < branched PEI (bPEI) 25 kDa. However, it was also evident that the siRNA release from the carrier, which was promoted by ssPEI, played an important role in the accessibility of siRNA for the gene silencing complex. Therefore, we suggest that a combination of a high branching density and reductively cleavable bonds within the PEI-based carrier system could be one possible step towards improving siRNA delivery.

Design, synthesis and antifungal activity of a novel water soluble prodrug of antifungal triazole.

A highly potent water soluble triazole antifungal prodrug, RO0098557 (1), has been identified from its parent, the novel antifungal agent RO0094815 (2). The prodrug includes a triazolium salt linked to an aminocarboxyl moiety, which undergoes enzymatic activation followed by spontaneous chemical degradation to release 2. Prodrug 1 showed high chemical stability and water solubility and exhibited strong antifungal activity against systemic candidiasis and aspergillosis as well as pulmonary aspergillosis in rats.

Synthesis of novel water soluble benzylazolium prodrugs of lipophilic azole antifungals.

Water soluble N-benzyltriazolium or N-benzylimidazolium salt type prodrugs of several highly lipophilic triazole or imidazole antifungals have been synthesized. They were designed to undergo an enzymatic activation followed by a self-cleavage to release a parent drug. The prodrugs such as 16 had enough chemical stability and water solubility for parenteral use and were rapidly and quantitatively converted to the active substance in human plasma.