Phosphorothioates, Essential Components of Therapeutic Oligonucleotides

Phosphorothioates have found their usefulness in the general area of oligonucleotide therapeutic applications. Initially this modification was introduced into the antisense methodology because of the nuclease resistance of the phosphorothioate linkage in comparison with that of the phosphate linkage. However, as experimental data accumulated, it was detected that this chemical modification also facilitates cellular uptake and bioavailibity in vivo. Thus, today the majority of therapeutic oligonucleotides contain this modification. This review will discuss the historical development of this modification and present some of its chemical properties where they differ from those of the phosphate group. The…