David Barrett

Role of Micafungin in the Antifungal Armamentarium

Serious infections caused by opportunistic molds remain a major problem for public health. Immune deficiency following organ transplantation and aggressive cancer treatment has greatly increased the incidence of systemic mycoses, and invasive aspergillosis in patients with AIDS is associated with significant morbidity and mortality. Amphotericin B is the first-line therapy for systemic infection because of its broad-spectrum and fungicidal activity. However, considerable side effects limit its clinical utility. The echinocandins are large lipopeptide molecules that inhibit the synthesis of 1,3-beta-D-glucan, a key component of the fungal cell wall. Three echinocandins have reached the market, and some others are in early clinical development. Caspofungin was the first echinocandin to be licensed for clinical use in most countries. Micafungin is licensed for clinical use in Japan, China, Taiwan, Jordan, Korea, Hong-Kong and the US, and anidulafungin is currently licensed in the US. The novel class of echinocandins represents a milestone in antifungal drug research that has further expanded our therapeutic options. Studies to date have shown that micafungin exhibits extremely potent antifungal activity against clinically important fungi, including Aspergillus and azole-resistant strains of Candida. In animal studies, micafungin is as efficacious as amphotericin B with respect to improvement of survival rate. Micafungin is also characterized by a linear pharmacokinetic profile and substantially fewer toxic effects. Micafungin is a poor substrate for the cytochrome P450 enzymes, and compared to azoles, fewer drug interactions are described. No dose adjustments of the drug are required in the presence of mycophenolate mofetil, cyclosporin, tacrolimus, prednisolone, or sirolimus. Strategies using this new echinocandin agent will benefit a large number of patients with severe immune dysfunction.

Synthesis and antibacterial activity of novel 4-pyrrolidinylthio carbapenems Part IV. 2-Alkyl substituents containing cationic heteroaromatics linked via a C–C bond

The synthesis and biological activity of a novel series of 2-alkyl-4-pyrrolidinylthio-beta-methylcarbapenems containing a variety of cationic heteroaromatic substituents linked via a C-C bond is described. As a result of these studies, we selected FR21818 (In) as a candidate compound for development. FR21818 exhibited a well balanced spectrum of antibacterial activity, including Pseudomonas aeruginosa and methicillin-resistant Staphylococcus aureus (MRSA), excellent urinary recovery, good stability against renal dehydropeptidase-I (DHP-I). no antigenicity and mutagenicity, weak toxicities, and good efficacy and therapeutic effect on mice systemic infections. Affinities to PBPs, permeability of outer membrane, and plasma levels in mice, dog, and cynomolgous monkey of FR21818 are also reported.

Synthesis and biological activity of novel macrocyclic antifungals: acylated conjugates of the ornithine moiety of the lipopeptidolactone FR901469.

A series of acylated analogues of the novel macrocyclic lipopeptidolactone FR901469 has been prepared and evaluated for antifungal and hemolytic activity. Several analogues displayed markedly reduced hemolytic potential and comparable protective effects to the natural product in a mouse model of candidiasis.

An expedient synthesis of the amide analog of the potent antifungal lipopeptidolactone FR901469

An expedient synthesis of the lactam analog (2) of the 40-membered lipopeptidolactone antifungal antibiotic, FR901469 (1), is described. The key steps in this synthesis are a novel biotransformation of the natural product to produce the highly versatile linear peptide building block 3, and efficient formation of the 40-membered ring by macrolactamization under high-dilution conditions.