(E)-5-(2-Bromovinyl)-2'-deoxyuridine: a potent and selective anti-herpes agent.

Of a series of five newly synthesized 2'-deoxyuridine derivatives, including 5-vinyl-dUrd, 5-ethynyl-dUrd, 5-(1-chlorovinyl)-dUrd, (E)-5-(2-bromovinyl)-dUrd, and (E)-5-(2-iodovinyl)-dUrd, the last two compounds were found to exert a marked inhibitory effect on the replication of herpes simplex virus type 1 [ID50 (mean inhibitory dose), 0.004-0.02 microgram/ml]. Both (E)-5-(2-bromovinyl)-dUrd and (E)-5-(2-iodovinyl)-dUrd were highly selective in their anti-herpes activity in that they did not affect the growth or metabolism of the host (primary rabbit kidney) cells unless drug concentrations were used that were 5,000- to 10,000-fold greater than those required to inhibit virus multiplication. In this sense (E)-5-(2-bromovinyl)-dUrd and (E)-5-(2-iodovinyl)-dUrd proved more selective in their activity against herpes simplex virus type 1 than all other anti-herpes compounds that have been described so far. In animal model systems (namely, cutaneous herpes infections of athymic nude mice), (E)-5-(2-bromovinyl)-dUrd suppressed the development of herpetic skin lesions and mortality therewith associated, whether the compound was administered topically or systemically. Under the same conditions, the standard anti-herpes drug 5-iodo-dUrd (Idoxuridine) offered little, if any, protection. Although the precise mechanism of action of (E)-5-(2-bromovinyl)-dUrd and (E)-5-(2-iodovinyl)-dUrd remains to be established, preliminary findings indicate that they do not specifically act at the thymidylate synthetase step.