In order to prevent neuraminidase activity leading to inefficient virus release (or to cause virus aggregation as described above), treatments with the compound needed to be initiated within 12 h of infection. chosen for clinical development, was studied in greater detail. Its potency and that of oseltamivir carboxylate decreased with increasing multiplicity of virus infection. Time-of-addition studies indicated Vacquinol-1 that treatment with either compound needed to begin 0 to 12 h after virus exposure for optimal activity. Exposure of cells to RWJ-270201 caused most of the virus to remain cell associated, with extracellular virus decreasing in a concentration-dependent manner. This is consistent with its effect as a neuraminidase inhibitor. RWJ-270201 shows promise in the treatment of human influenza virus infections. Influenza has continued to be a significant public health concern, with annual epidemics responsible for serious morbidity and mortality (1, 13). Much attention has consequently been given to the development of antiviral drugs for the treatment of this disease. Amantadine and rimantadine both have been approved for prophylaxis of influenza A virus infection (6). Ribavirin was shown to be effective against experimental influenza virus infections in mice (9), and was studied in humans by small-particle aerosol delivery against severe influenza virus infections (11). However, it was not effective enough to receive drug approval. As early Rabbit Polyclonal to ALK (phospho-Tyr1096) as 1976 Palese and Compans (19) reported an inhibitor of influenza virus neuraminidase. This research was largely ignored for many years, and it was not until recently Vacquinol-1 that the search for more potent neuraminidase inhibitors has intensified. From these investigations, zanamivir (GG167) and oseltamivir carboxylate (GS4071) emerged; these compounds were found to be highly active against both influenza A and B viruses (10, 27). Zanamivir, a topical agent approved for clinical use, is effective prophylactically and therapeutically for the treatment of influenza (16, 17). Oseltamivir, the orally active prodrug form of oseltamivir carboxylate (22), is also clinically approved and has been found to be effective for both prophylaxis and treatment of influenza in humans (7, 18). Structure-activity analyses with the purified influenza virus neuraminidase enzyme and knowledge of its three-dimensional structure (26) have led to the identification of new inhibitors. A series of cyclopentane derivatives was found to cause potent and selective inhibition of influenza virus neuraminidase (2). The chemical structures of the more potent antiviral compounds (Fig. ?(Fig.1)1) have features in common with both zanamivir and oseltamivir carboxylate but differ in having a five-membered-ring structure. In this report the activities of these novel compounds in vitro Vacquinol-1 against various strains of influenza virus are presented. Compound RWJ-270201 was evaluated in greater detail in secondary assays, since it has been selected for clinical development. Open in a separate window FIG. 1 Chemical structures of cyclopentane derivatives, zanamivir, and oseltamivir carboxylate. MATERIALS AND METHODS Compounds. RWJ-270201, BCX-1827, BCX-1898, BCX-1923, zanamivir, and oseltamivir carboxylate were synthesized at BioCryst Pharmaceuticals (Birmingham, Ala.). Ribavirin was Vacquinol-1 obtained from ICN Pharmaceuticals (Costa Mesa, Calif). Viruses. The following viruses were provided by H. Regnery of the Influenza Branch of the Centers for Disease Control and Prevention (Atlanta, Ga.): A/Texas/36/91 (H1N1), A/Bayern/07/95 (H1N1), A/Beijing/262/95 (H1N1), A/Washington/05/96 (H3N2), A/Johannesburg/33/94 (H3N2), A/Sydney/05/97 (H3N2), A/Shangdong/09/93 (H3N2), A/Beijing/32/92 (H3N2), B/Beijing/184/93, B/Panama/45/90, and B/Harbin/07/94. A/NWS/33 (H1N1) was provided by K. Cochran of the University of Michigan (Ann Arbor). A/PR/8/34 (H1N1) was obtained from F. Schabel, Jr., Southern Research Institute (Birmingham, Ala.). A/Victoria/3/75 (H3N2), A/Port Chalmers/1/73 (H3N2), B/Hong Kong/5/72, and B/Lee/40 were obtained from the American Type Culture Collection (Manassas, Va.). A/Los Angeles/2/87 (H3N2) and A/Washington/897/80 (H3N2) were from Program Resources, Inc. (Rockville, Md.). A/X-31 (H3N2), a reassortment virus containing hemagglutinin and neuraminidase genes from A/Aichi/2/68 (H3N2) and the remainder of the genes from A/PR/8/34 (H1N1), was obtained from E. Kilbourne, Mount Sinai School of Medicine, New York Medical College, City University of New York (New York, N.Y.). A/Port Chalmers/1/73r (H3N2), an amantadine-resistant virus, was prepared from the wild-type virus by serial passage in the presence of the drug in this laboratory. A/Virginia/2/88r (H3N2), a clinically isolated amantadine-resistant virus, was provided by F. Hayden, University of Virginia School of Medicine (Charlottesville). A/Duck/MN/1525/81 (H5N1) and A/Gull/PA/4175/83 (H5N1) were obtained from R. Webster of the St. Jude Children’s Research Hospital (Memphis, Tenn.). All viruses were passaged in cells to.