Interesting you should bring up patenting.
A patent attorney or someone well versed in the area can much better address this, but I will offer my thoughts.
At some point Seymour or Diwan have addressed patents either directly or indirectly through PR, Filing, presentation or other media.
What I gather is, the patents that have been filed are for the main design, that is PEG combined with ligand equals effective drug (viricide), perhaps even more generic than that. Then because of the uniqueness of each ligand to a potential indication, the specific combination of a PEG molecule to a ligand will be uniquely patentable. So as long as the process is patented, the ligands are protected by the process patent. Patents for the specific cides will be filed closer to their actual approval ensuring maximum exposure to patent protection.
Also, I believe there may be ways to apply for patent protection extensions in pharma, but others might know better.