Question

Which is the active form of Ganciclovir?

• A. Phosphate
• B. . Tetraphosphate
• C. Biphosphate
• D. Triphosphate

Answer 1

The Correct Option is D

Understanding the Question:
The question asks which phosphorylated form of ganciclovir is the one that is actually active against the virus.

Key Concept:
Ganciclovir is a prodrug that needs stepwise phosphorylation inside the cell before it can compete with the natural nucleotide at the viral DNA polymerase's active site.

Checking Each Option:
The monophosphate form is only the first phosphorylation step and is not active on its own.
A tetraphosphate species is not part of this activation pathway at all, since nucleoside analogues in this class only go up to a triphosphate.
The diphosphate (biphosphate) form is an intermediate that still needs one more phosphorylation before it becomes active.
The triphosphate form is close enough in structure to deoxyguanosine triphosphate that viral DNA polymerase incorporates it into the growing DNA chain, stopping the chain from extending and halting viral replication.

Final Answer:
Ganciclovir triphosphate is the active form of the drug.