Novel alpha- and beta-amino acid inhibitors of influenza virus neuraminidase

In an effort to discover novel, noncarbohydrate inhibitors of influenza vir us neuraminidase we hypothesized that compounds which contain positively ch arged amino groups in an appropriate position to interact with the Asp 152 or Tyr 406 side chains might be bound tightly by the enzyme. Testing of 300 alpha- and beta -amino acids led to the discovery of two novel neuraminida se inhibitors, a phenylglycine and a pyrrolidine, which exhibited K-i value s in the 50 muM range versus influenza virus A/N2/Tokyo/3/67 neuraminidase but which exhibited weaker activity against influenza virus B/Memphis/3/89 neuraminidase. Limited optimization of the pyrrolidine series resulted in a compound which was about 24-fold more potent than 2-deoxy-2,3-dehydro-N-ac etylneuraminic acid in an anti-influenza cell culture assay using A/N2Nicto ria/3/75 virus. X-ray structural studies of A/N9 neuraminidase-inhibitor co mplexes revealed that both classes of inhibitors induced the Glu 278 side c hain to undergo a small conformational change, but these compounds did not show time-dependent inhibition. Crystallography also established that the a lpha -amino group of the phenylglycine formed hydrogen bonds to the Asp 152 carboxylate as expected. Likewise, the beta -amino group of the pyrrolidin e forms an interaction with the Tyr 406 hydroxyl group and represents the f irst compound known to make an interaction with this absolutely conserved r esidue. Phenylglycine and pyrrolidine analogs in which the alpha- or beta - amino groups were replaced with hydroxyl groups were 365- and 2,600-fold we aker inhibitors, respectively. These results underscore the importance of t he amino group interactions with the Asp 152 and Tyr 406 side chains and ha ve implications for anti-influenza drug design.