Hisashi Tamaoka

A Complement Inhibitor Produced by Stachybotrys complementi, nov. sp. K-76, a New Species of Fungi Imperfecti

A complement inhibitor, K‐76, was isolated and purified from the culture supernatant of a fungus, Stachybotrys complementi, nov. sp. K‐76, isolated from soil of Ishigaki Island, Okinawa. K‐76 is a sesquiterpene compound and it can be oxidized to a monocarboxylic derivative (K‐76 COOH), the sodium salt of which is very soluble and much less toxic than K‐76. K‐76 and K‐76 COOH both inhibited complement activation by either the classical or alternative pathway. They inhibited generation of the factor chemotactic to human polymorphonuclear leukocytes from human serum by aggregated immunoglobulin. When sensitized erythrocytes were treated with complement in the presence of K‐76 COOH, the resulting unlysed cells were found to be in the state of EAC1, 4b, 2a, 3b. Thus K‐76 COOH is considered to block mainly the C5 intermediate step. K‐76 COOH did not inhibit any proteases or esterases tested, except when tested at high concentration.

Evaluation of OPC-17116 against important pathogens that cause respiratory tract infections.

The antibacterial activity of OPC-17116, a new fluoroquinolone antibacterial agent, against important pathogens that cause respiratory tract infections was evaluated in vitro and in vivo and compared with those of ciprofloxacin, ofloxacin, and norfloxacin. The pharmacokinetic profiles of OPC-17116 were studied in both mice and rats given the drug orally at doses of 50 and 40 mg/kg of body weight, respectively. OPC-17116 showed a high degree of distribution in the lung tissues of both species, with maximum concentrations of 29.6 and 32.0 micrograms/g, respectively. Furthermore, the drug concentrations in lung tissue were about 10 to 15 times greater than the concentrations in plasma. OPC-17116 showed potent antibacterial activity against such pathogens as Staphylococcus aureus, Streptococcus pneumoniae, Klebsiella pneumoniae, Pseudomonas aeruginosa, Haemophilus influenzae, and Moraxella catarrhalis. The MICs of this compound for 90% of these organisms except methicillin-resistant S. aureus and P. aeruginosa ranged from < or = 0.006 to 0.78 microgram/ml. The in vitro antibacterial activity of OPC-17116 was reflected by the efficacy of a single oral dose against systemic bacterial infections in mice. OPC-17116 showed a superior effect against gram-positive bacteria, H. influenzae, and M. catarrhalis. In comparison with the other reference compounds, the efficacy of OPC-17116 was less than that of ciprofloxacin against K. pneumoniae and P. aeruginosa. OPC-17116 showed a greater therapeutic effect than the other drugs against experimental acute pneumonia caused by these organisms in mice or rats. This excellent therapeutic effect against respiratory tract infections may be a result of its high level of distribution in lung tissue.

Synthesis and biological properties of substituted 1,4-dihydro-5-methyl-4-oxo-3-quinolinecarboxylic acids

A series of substituted 1-cyclopropyl-6-fluoro-1, 4-dihydro-5-methyl-4-oxo-3-quinoline carboxylic acids was synthesized and tested for their in vitro and in vivo antibacterial activity. The introduction of a methyl group at the 5-position of quinoline nucleus enhanced characteristically the antibacterial activity against Gram-positive bacteria, including Streptococcus pneumoniae, which is a major pathogen in the respiratory tract infection, while retaining Gram-negative activity. Among them, 1-cyclopropyl-6-fluoro-1, 4-dihydro-5-methyl-7-(3-methyl-1-piperazinyl)-4-oxo-3-quinolinecarboxyli c acid hydrochloride (grepafloxacin) exhibited potent in vitro antibacterial activity against Gram-positive bacteria such as Streptococcus pneumoniae and high in vivo efficacy on the experimental systemic infections caused by the Gram-positive and -negative bacteria tested. It also showed a high distribution to the lung and bronchoalveolar lavage fluid in comparison to reference drugs and is now undergoing clinical evaluation.