The present invention concerns the inactivation of viral infectivity in a cell-free environment as well as the preparation of a pharmaceutical agent and a method therefore. According to the invention the use of a sequence of oligodeoxynucleotides or oligoribonucleotides or a chimera or a combination thereof capable of binding to conserved regions of viral RNA for the inactivation of viral infectivity outside in a cell-free environment is intended. Furthermore said sequences are used for the preparation of a pharmaceutical agent for the inactivation of viral infectivity.
