Oseltamivir phosphate is an inhibitor of influenza neuraminidase, with IC₅₀ values of 13nM, 1.34nM, 0.9nM, and 0.67nM against Influenza B, A/H1N1, A/H1N2, and A/H3N2 viruses, respectively[1]. As a neuraminidase inhibitor, Oseltamivir phosphate attenuates the penetration of viruses through the mucus on the respiratory tract and inhibits the release of virus progeny from infected cells[2].
In vitro, with 3 days of treatment, Oseltamivir phosphate at 0.0125nM showed partial inhibition, whereas concentrations above 0.05nM showed complete inhibition in H1N1 IVA-infected MDCK cells[2]. Oseltamivir phosphate (500-800μg/mL; 24-72h) inhibited the viability of MDA-MB-231 and MCF-7 cells in a dose- and time-dependent manner[3].
In vivo, in BALB/c mice infected with the H3N1 influenza virus, Oseltamivir phosphate (1 and 10mg/kg/d; p.o.; twice daily from 4 hours before infection to 5 days post-infection) dose-dependently reduced total cells, neutrophils, macrophages, and pro-inflammatory cytokines in bronchoalveolar lavage fluid (BALF)[4].
References:
[1] Ferraris, O et al. “Sensitivity of influenza viruses to zanamivir and Oseltamivir phosphate: a study performed on viruses circulating in France prior to the introduction of neuraminidase inhibitors in clinical practice.” Antiviral research vol. 68,1 (2005): 43-8.
[2] Chan RWY, Tao KP, Ye J, et al. Inhibition of Influenza Virus Replication by Oseltamivir phosphate Derivatives. Pathogens. 2022;11(2):237.
[3] Haxho F, Allison S, Alghamdi F, et al. Oseltamivir phosphate phosphate monotherapy ablates tumor neovascularization, growth, and metastasis in mouse model of human triple-negative breast adenocarcinoma. Breast Cancer (Dove Med Press). 2014;6:191-203.
[4] Wong ZX, Jones JE, Anderson GP, Gualano RC. Oseltamivir phosphate treatment of mice before or after mild influenza infection reduced cellular and cytokine inflammation in the lung. Influenza Other Respir Viruses. 2011;5(5):343-350.