The
antiviral activity of
didemnin A and
didemnin B against a lethal Semliki Forest virus (SFV)
infection of mice and a cutaneous herpes type 1
infection in hairless mice was evaluated. Both compounds significantly decreased the severity of herpesvirus lesions if topical treatment with either
didemnin A or
didemnin B was started 2 days prior to
infection. The survival rate was significantly greater (P = 0.03) in the
didemnin B treated group than in controls. If initiation of treatment was delayed until 1 h after
infection, no activity was obtained. The compounds were not active against cutaneous
herpesvirus infection when injected intraperitoneally (i.p.).
Didemnin B at concentrations as low as 1.5 micrograms, administered topically 3 times daily for 5 days, produced skin irritation. Eight times this level of
didemnin A could be administered before similar toxicity was observed. The limited activity of
didemnins A and B coupled with irritation at the treatment site limits their usefulness in treating cutaneous
herpesvirus infection. Neither
didemnin A nor B had significant activity in SFV-infected mice.