There may be good reasons to be skeptical about Vivagel's near-term prospects, but I don't think a Cassandran attitude about HIV mutation is one of them.
From "Structure Activity Relationship of Dendrimer Microbicides with Dual Action Antiviral Activity" 2010
The authors discuss interaction of dendrimers (including Vivagel's SPL7013) with the highly mutable HIV external glycoprotein gp120:
"Our studies demonstrate that SPL7013 and SPL7115 block HIV-1 entry indicating that they bind to HIV-1 surface proteins and/or host cell receptors required for entry...Moreover, multiple mutations in HIV-1 gp120 are required to develop resistance to dendrimers as observed for the related DNAA dendrimer SPL2923"
