The invention relates to novel compositions and methods of using maribavir which enhance its effectiveness in medical therapy, as well as to maribavir isomers and methods of use thereof for counteracting the potentially adverse effects of maribavir isomerization in vivo in the event it occurs.

Methods and kits for detecting antibodies (e.g., anti-drug antibodies). Such methods and kits permit the detection of, for example, anti-drug antibodies in human body fluids, such as blood, plasma and serum.