Tamiflu
Systematic structure-based design and stereoselective synthesis of novel multisubstituted cyclopentane derivatives with potent antiinfluenza activity.

Chand P, Kotian PL, Dehghani A, El-Kattan Y, Lin TH, Hutchison TL, Babu YS, Bantia S, Elliott AJ, Montgomery JA.

BioCryst Pharmaceuticals, Inc., 2190 Parkway Lake Drive, Birmingham, Alabama 35244, USA. pchand biocryst.com

The design and synthesis of novel, orally active, potent, and selective inhibitors of influenza neuraminidase differing structurally from existing neuraminidase inhibitors are described. X-ray crystal structures of complexes of neuraminidase with known five- and six-membered ring inhibitors revealed that potent inhibition of the enzyme is determined by the relative positions of the interacting inhibitor substituents (carboxylate, glycerol, acetamido, hydroxyl) rather than by the absolute position of the central ring. This led us to design potential neuraminidase inhibitors in which the cyclopentane ring served as a scaffold for substituents (carboxylate, guanidino, acetamido, alkyl) that would interact with the four binding pockets of the neuraminidase active site at least as effectively as those of the established six-membered ring inhibitors such as DANA (2), zanamivir (3), and oseltamivir (4). A mixture of the isomers was prepared initially. Protein crystallography of inhibitor-enzyme complexes was used to screen mixtures of isomers in order to identify the most active stereoisomer. A synthetic route to the identified candidate 50 was developed, which featured (3 + 2) cycloaddition of 2-ethylbutyronitrile oxide to methyl (1S,4R)-4[(tert-butoxycarbonyl)amino]cyclopent-2-ene-1-carboxylate (43). Structures of the synthetic compounds were verified by NMR spectroscopy using nuclear Overhauser effect methodology. Two new neuraminidase inhibitors discovered in this work, 50 and 54, have IC(50) values vs neuraminidase from influenza A and B of <1 and <10 nM, respectively. These IC(50) values are comparable or superior to those for zanamivir and oseltamivir, agents recently approved by the FDA for treatment of influenza. The synthetic route used to prepare 50 and 54 was refined so that synthesis of pure active isomer 54, which has five chiral centers, required only seven steps from readily available intermediates. Further manipulation was required to prepare deoxy derivative 50. Because the activities of the two compounds are comparable and 54 [RWJ-270201 (BCX-1812)] is the easier to synthesize, it was selected for further clinical evaluation.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11728184&dopt=Abstract oseltamivir Tamiflu



Tamiflu
Neuraminidase inhibitors for treatment of influenza A and B infections.

[No authors listed]

Influenza epidemics are responsible for an average of approximately 20,000 deaths per year in the United States. The main method for preventing influenza and its severe complications is influenza vaccination. Influenza-specific antiviral drugs are an important adjunct to vaccine but are not a substitute for vaccine. In the United States, four antiviral agents are approved for preventing or treating influenza: amantadine, rimantadine, zanamivir, and oseltamivir. Amantadine was approved for prophylaxis of influenza A(H2N2) infection in the United States in 1966 and was approved for prophylaxis and treatment of influenza A infection in 1976; rimantadine was approved for treatment and prophylaxis of influenza A infection in 1993 [corrected]. This report provides information on two neuraminidase inhibitors, zanamivir and oseltamivir, which were approved in 1999. Neuraminidase inhibitors are a new class of antiviral drugs that inhibit influenza A and B viruses. Zanamivir is approved for treatment of uncomplicated acute illness caused by influenza virus in persons aged > or =12 years who have been symptomatic for no more than 2 days. Oseltamivir is approved for treatment of uncomplicated illness caused by influenza infection in adults aged > or =18 years who have been symptomatic for no more than 2 days. Neither zanamivir nor oseltamivir is approved for influenza prophylaxis. This report and the Advisory Committee on Immunization Practices (ACIP) 1999 recommendations on influenza prevention and control (MMWR 1999;48[No.RR-4]:1-28) can be accessed at the website for the Influenza Branch, Division of Viral and Rickettsial Diseases, National Center for Infectious Diseases, CDC, at <http://www.cdc.gov/ncidod/diseases/flu/ fluvirus.htm> or at the MMWR website at <http://www2.cdc.gov/mmwr/>.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=10632443&dopt=Abstract oseltamivir Tamiflu



Tamiflu
In vitro characterization of A-315675, a highly potent inhibitor of A and B strain influenza virus neuraminidases and influenza virus replication.

Kati WM, Montgomery D, Carrick R, Gubareva L, Maring C, McDaniel K, Steffy K, Molla A, Hayden F, Kempf D, Kohlbrenner W.

Antiviral Drug Discovery Research, Abbott Laboratories, Abbott Park, Illinois 60064-6217, USA. warren.kati abbott.com

A-315675 is a novel, pyrrolidine-based compound that was evaluated in this study for its ability to inhibit A and B strain influenza virus neuraminidases in enzyme assays and influenza virus replication in cell culture. A-315675 effectively inhibited influenza A N1, N2, and N9 and B strain neuraminidases with inhibitor constant (K(i)) values between 0.024 and 0.31 nM. These values were comparable to or lower than the K(i) values measured for oseltamivir carboxylate (GS4071), zanamivir, and BCX-1812, except for the N1 enzymes that were found to be the most sensitive to BCX-1812. The time-dependent inhibition of neuraminidase catalytic activity observed with A-315675 is likely due to its very low rate of dissociation from the active site of neuraminidase. The half times for dissociation of A-315675 from B/Memphis/3/89 and A/Tokyo/3/67 (H3N2) influenza virus neuraminidases of 10 to 12 h are significantly slower than the half times measured for oseltamivir carboxylate (33 to 60 min). A-315675 inhibited the replication of several laboratory strains of influenza virus in cell culture with potencies that were comparable or superior to those for oseltamivir carboxylate and BCX-1812, except for the A/H1N1 viruses that were found to be two- to fourfold more susceptible to BCX-1812. A-315675 and oseltamivir carboxylate exhibited comparable potencies against a panel of A/H1N1 and A/H3N2 influenza virus clinical isolates, but A-315675 was found to be significantly more potent than oseltamivir carboxylate against the B strain isolates. The favorable in vitro results relative to other clinically effective agents provide strong support for the further investigation of A-315675 as a potential therapy for influenza virus infections.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11897583&dopt=Abstract oseltamivir Tamiflu



Tamiflu
Use of oseltamivir during influenza outbreaks in Ontario nursing homes, 1999-2000.

Bowles SK, Lee W, Simor AE, Vearncombe M, Loeb M, Tamblyn S, Fearon M, Li Y, McGeer A; Oseltamivir Compassionate Use Program Group.

Department of Pharmacy, Sunnybrook and Women's College Health Sciences Centre, Toronto, Ontario.

OBJECTIVES: To describe the experience of Ontario long-term care facilities that used oseltamivir during influenza outbreaks in 1999/2000. DESIGN: Case series. SETTING: Ten Ontario long-term care facilities for older people and their residents. PARTICIPANTS: Older residents of long-term care facilities. INTERVENTION: Oseltamivir for treatment or prophylaxis during 11 influenza outbreaks in 1999/2000. MEASUREMENTS: Control of outbreaks; pneumonia, hospitalization, and death complicating acute influenza. RESULTS: All outbreaks were due to influenza A//H3N2/Sydney/05/97. One facility elected to use oseltamivir for treatment and amantadine for prophylaxis. The remaining nine facilities (10 outbreaks) recommended oseltamivir for treatment and prophylaxis (after amantadine failure in five and as primary prophylaxis in five). Use of oseltamivir was associated with termination of the outbreak in all eight evaluable outbreaks. Overall, 178/185 (96%) case-residents met the case definition of influenza and had complete data for evaluation. Of these, 63 (35%) were treated with antibiotics, 37 (21%) were diagnosed with pneumonia, 19 (11%) were hospitalized, and 16 (9%) died. Compared with residents receiving no therapy or who became ill while taking amantadine, residents who received oseltamivir within 48 hours of the onset of symptoms were less likely to be prescribed antibiotics, to be hospitalized, or to die (P <.05 for each outcome). These differences persisted and remained statistically significant when corrected for influenza immunization status. A total of 730 residents received oseltamivir prophylaxis for a median of 9 days (range 5-12). Of these, side effects were identified in 30 (4.1%), the most common being diarrhea (12 residents, 1.6%), cough (5, 0.7%), confusion (4, 0.5%) and nausea (4, 0.5%). CONCLUSIONS: Oseltamivir is safe and appears to be effective when used as treatment or prophylaxis to control outbreaks of influenza in older nursing home residents.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11982659&dopt=Abstract oseltamivir Tamiflu



Tamiflu
In vitro selection and characterization of influenza A (A/N9) virus variants resistant to a novel neuraminidase inhibitor, A-315675.

Molla A, Kati W, Carrick R, Steffy K, Shi Y, Montgomery D, Gusick N, Stoll VS, Stewart KD, Ng TI, Maring C, Kempf DJ, Kohlbrenner W.

Global Pharmaceutical Research and Development, Abbott Laboratories, Abbott Park, Illinois 60064, USA. m.molla abbott.com

With the recent introduction of neuraminidase (NA) inhibitors into clinical practice for the treatment of influenza virus infections, considerable attention has been focused on the potential for resistance development and cross-resistance between different agents from this class. A-315675 is a novel influenza virus NA inhibitor that has potent enzyme activity and is highly active in cell culture against a variety of strains of influenza A and B viruses. To further assess the therapeutic potential of this compound, in vitro resistance studies have been conducted and a comparative assessment has been made relative to oseltamivir carboxylate. The development of viral resistance to A-315675 was studied by in vitro serial passage of influenza A/N9 virus strains grown in MDCK cells in the presence of increasing concentrations of A-315675. Parallel passaging experiments were conducted with oseltamivir carboxylate, the active form of a currently marketed oral agent for the treatment of influenza virus infections. Passage experiments with A-315675 identified a variant at passage 8 that was 60-fold less susceptible to the compound. Sequencing of the viral population identified an E119D mutation in the NA gene, but no mutations were observed in the hemagglutinin (HA) gene. However, by passage 10 (2.56 microM A-315675), two mutations (R233K, S339P) in the HA gene appeared in addition to the E119D mutation in the NA gene, resulting in a 310-fold-lower susceptibility to A-315675. Further passaging at higher drug concentrations had no effect on the generation of further NA or HA mutations (20.5 microM A-315675). This P15 virus displayed 355-fold-lower susceptibility to A-315675 and >175-fold-lower susceptibility to zanamivir than did wild-type virus, but it retained a high degree of susceptibility to oseltamivir carboxylate. By comparison, virus variants recovered from passaging against oseltamivir carboxylate (passage 14) harbored an E119V mutation and displayed a 6,000-fold-lower susceptibility to oseltamivir carboxylate and a 175-fold-lower susceptibility to zanamivir than did wild-type virus. Interestingly, this mutant still retained susceptibility to A-315675 (42-fold loss). This suggests that cross-resistance between A-315675- and oseltamivir carboxylate-selected variants in vitro is minimal.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11991966&dopt=Abstract oseltamivir Tamiflu