Depending on the strain, influenza A virus causes animal, zoonotic, pandemic, or seasonal influenza with varying degrees of severity. Two surface glycoprotein spikes, hemagglutinin (HA) and neuraminidase (NA), are the most important influenza A virus antigens. NA plays an important role in the propagation of influenza virus by removing terminal sialic acid from sialyl decoy receptors and thereby facilitating the release of viruses from traps such as in mucus and on infected cells. Some NA inhibitors have become widely used drugs for treatment of influenza. However, attempts to develop effective and safe NA inhibitors that can be used for treatment of anti-NA drugs-resistant influenza viruses have continued. In this chapter, we describe the following updates on influenza A NA inhibitor development: (i) N-acetylneuraminic acid (Neu5Ac)-based derivatives, (ii) covalent NA inhibitors, (iii) sulfo-sialic acid analogs, (iv) N-acetyl-6-sulfo-β-d-glucosaminide-based inhibitors, (v) inhibitors targeting the 150-loop of group 1 NAs, (vi) conjugation inhibitors, (vii) acylhydrazone derivatives, (viii) monoclonal antibodies, (ix) PVP-I, and (x) natural products. Finally, we provide future perspectives on the next-generation anti-NA drugs.