Chemical compounds, being the alkyl sulfate of sulfated saccharides, particularly, dextrin, dextran, and cyclodextrin, and pharmaceutical compositions containing these compounds. The compounds of the invention provide antiviral activity, particularly in the treatment and prevention of sexually-transmitted diseases. Methods of treating viral infection and preventing viral transmission include administration include administration of the compounds of the invention orally, topically, subcutaneously, by muscular injection, by intraperitoneal injection and by intravenous injection.