Why bone marrow suppression with Ganciclovir but not other cyclovirs?

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Oct 7, 2014
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I've tried to look up the answer to this question but was unsuccessful :(

Question: Ganciclovir causes bone marrow suppression. Acyclovir/Valcyclovir/Famciclovir do not have this side effect. They are all guanosine analogs, get mono-phosphorylated by viral kinases first, and inhibit viral DNA polymerase. The only difference is that they get mono-phosphorylated by different enzymes (thymidine kinase vs CMV UL97 kinase).

Does anyone know why Ganciclovir has this side effect but the other -cyclovirs do not? It makes sense how this would be a side effect because it's a nucleoside analog and inhibits a DNA polymerase (even though it's preferentially viral) but I would think the other -cyclovirs should have this side effect as well.

Thank you very much in advance!