PROS1 and influenza: There are several therapeuticstrategies targeting ACE2 which include: vaccines based on S protein, exogenousadministration of a soluble form of ACE2, and administration of small molecules [e.g.,arbidol (19), an anti-influenza drug] or antibodies (e.g., STI-1499, an anti-spikeantibody) to block the interaction of ACE2 with S protein.66