Replies to post #84760 on Biotech Values

[mcbio]

Re: VRUS JMP webcast

PSI-879 and PSI-938, the 3rd-gen purine nukes, both deliver the same active triphosphate to the liver with the only difference being that the prodrug is different.

This statement requires clarification. If my understanding of these drugs is correct, the prodrug resolves to a monophosphate nucleotide, not a triphosphate. I.e., the second and third phosphorylation steps are performed in vivo. I know this is how IDIX’s IDX184 works, and I presume that VRUS’ latest and greatest nukes work the same way.

Thus, the statement in your post, while technically true, is somewhat misleading insofar as it might suggest to some readers that the prodrug resolves to the active triphosphate. The ambiguity arises from the imprecise meaning of word delivers.

From a practical standpoint, the first phosphorylation step is the critical one to perform ex vivo, and all three of these drugs (PSI-879, PSI-938, and IDX184) do that.

It's right at the 17 minute mark of the presentation (http://investor.pharmasset.com/events.cfm ) where Schaefer Price, the CEO, makes the statement that both compounds "deliver the exact same active triphosphate." Perhaps he misspoke?