Abstract: The invention relates to a pharmaceutical composition containing as an active ingredient at least one compound selected from the compounds of the formula (II), in which the S atom is bonded to the nucleoside carbon at T or to the nucleoside carbon at 3?, and from the compounds of the following formula (III): formulae in which B is a nucleotide natural or modified base, x is 0, 1 or 2, and R1 and R represent a carbonated group or a molecular hydrocarbon remnant that can be substituted and/or interrupted by one or more atoms and/or by one or more groups containing one or more atoms, said atoms being selected from N, O, P, S, Si, X where X is halogen. The invention also relates to pharmaceutically acceptable carrier.