SIBA (5'-Deoxy-5'-isobutylthioadenosine) is a synthetic analogue of SAH, acts as an inhibitor of S-adenosylmethionine-mediated transmethylation. SIBA can interfere with a variety of enzymatic activities in vitro, such as SAH hydrolase, methylthioadenosine phosphorylase and cAMP phosphodiesterase. SIBA reversibly blocks the multiplication of herpes simplex type 1 virus (HSV)