FGCV metabolites present in livers of mice expressing HSV1-tk. A mouse was injected with 1.0 × 109 pfu of AdCMV-HSV1-tk virus followed by injection of FGCV 48 h later and sacrifice 180 min later. HPLC analysis of the liver sample shows peaks corresponding to ≈3, ≈9, ≈16, and ≈32 min, which likely represent FGCV, FGCV-monophosphate, FGCV-diphosphate, and FGCV-triphosphate, respectively. Thirty percent of the radioactivity retained in the liver was present in the DNA/RNA fraction (not shown).