- Guanosine nucleoside analogue similar to acyclovir
- Inhibits all human herpesviruses by inhibiting DNA polymerase
- Major toxicity is cytopenias
- Resistance in CMV
- Most often conferred by mutations of UL97 kinase, which is required in order to phosphorylate ganciclovir into its active form
- Can also develop through mutations in the target UL54 DNA polymerase
- Oral bioavailability 6-8%
- Indications: CMV after hematopoietic stem cell transplantation, CMV after solid organ transplantation, Congenital CMV, Cytomegalovirus, Herpesviridae, Macacine alphaherpesvirus 1, Post-transplant acute limbic encephalitis