- The Cys607-->Tyr change in the UL97 phosphotransferase confers ganciclovir resistance to two human cytomegalovirus strains recovered from two immunocompromised patients. Baldanti, F., Underwood, M.R., Talarico, C.L., Simoncini, L., Sarasini, A., Biron, K.K., Gerna, G. Antimicrob. Agents Chemother. (1998)