Triple Combination of Amantadine, Ribavirin, and Oseltamivir Is Highly Active and Synergistic against Drug Resistant Influenza Virus Strains In Vitro

Abstract

The rapid emergence and subsequent spread of the novel 2009 Influenza A/H1N1 virus (2009 H1N1) has prompted the World Health Organization to declare the first pandemic of the 21st century, highlighting the threat of influenza to public health and healthcare systems. Widespread resistance to both classes of influenza antivirals (adamantanes and neuraminidase inhibitors) occurs in both pandemic and seasonal viruses, rendering these drugs to be of marginal utility in the treatment modality. Worldwide, virtually all 2009 H1N1 and seasonal H3N2 strains are resistant to the adamantanes (rimantadine and amantadine), and the majority of seasonal H1N1 strains are resistant to oseltamivir, the most widely prescribed neuraminidase inhibitor (NAI). To address the need for more effective therapy, we evaluated the in vitro activity of a triple combination antiviral drug (TCAD) regimen composed of drugs with different mechanisms of action against drug-resistant seasonal and 2009 H1N1 influenza viruses. Amantadine, ribavirin, and oseltamivir, alone and in combination, were tested against amantadine- and oseltamivir-resistant influenza A viruses using an in vitro infection model in MDCK cells. Our data show that the triple combination was highly synergistic against drug-resistant viruses, and the synergy of the triple combination was significantly greater than the synergy of any double combination tested (P<0.05), including the combination of two NAIs. Surprisingly, amantadine and oseltamivir contributed to the antiviral activity of the TCAD regimen against amantadine- and oseltamivir-resistant viruses, respectively, at concentrations where they had no activity as single agents, and at concentrations that were clinically achievable. Our data demonstrate that the TCAD regimen composed of amantadine, ribavirin, and oseltamivir is highly synergistic against resistant viruses, including 2009 H1N1. The TCAD regimen overcomes baseline drug resistance to both classes of approved influenza antivirals, and thus may represent a highly active antiviral therapy for seasonal and pandemic influenza.

Antioxidant Therapy as a Potential Approach to Severe Influenza-Associated Complications

“…These results suggest the need for development of new anti-influenza drugs utilizing alternative antiviral mechanisms and consideration of using anti-influenza drug combinations. Some such approaches have been explored, whereby a triple combination of amantadine, ribavirin and oseltamivir was highly active and synergistic against drug resistant influenza virus strains in vitro [17]. In cases of severe influenza-associated complications, the pathological manifestations are the result of complex biological phenomena, such as apoptosis induction, macrophage activation, oxidative tissue damage and higher contents of pro-inflammatory cytokines [18].…”

Virological Clearance Rate of High-Dose Oseltamivir or Triple-Combination Antiviral Therapy in Complicated 2009 Pandemic Influenza A (H1N1) Infection

“…However, clinical data are lacking to substantiate this recommendation. The limitations of neuramidase inhibitor monotherapy for severe influenza illness have also renewed interest in combination antiviral therapy (5)(6)(7)(8). Previous studies have demonstrated that triple combination of antiviral drugs (TCAD)-amantadine, ribavirin, and oseltamivir-was highly and synergistically effective against influenza A virus in vitro, even for drugresistant strains (6).…”

Chemotherapy of Influenza: Current and Novel Approach

“…The effect of the same combination against different strains of H5N1 highly pathogenic influenza virus was additive or synergistic for certain doses again depending on the strain (41) ( Table 3). (39,62) and synergy in another study against amantadine-sensitive H5N1 virus (80) ( Table 2). …”

“…Amantadine, ribavirin and osletamivir have also been tested in vitro demonstrating highly synergistic effect against 13 influenza strains A (H1N1), A (H3N2), A(H5N1) viruses (61,62). This combination is in ongoing clinical testing as TCAD (triple combination of antiviral drugs) by Adamas Pharmaceuticals Company.…”