Article date: December 2000
By: Stephen Kewn,1, Patrick G. Hoggard,1, D. Sales,1, A. Johnson2, David J. Back1, Sean
, Mark
in Volume 50, Issue 6, pages 597-604
Aims Lamivudine (3TC, 2′‐deoxy‐3′‐thiacytidine) requires intracellular metabolism to its active 5′‐triphosphate, 3TC‐5′‐triphosphate (3TCTP), to inhibit the replication of hepatitis B virus (HBV). We have investigated the activation of 3TC, in the presence and absence of a range of compounds, in HepG2 cells. The intracellular levels of the endogenous competitor of 3TCTP, 2′‐deoxycytidine‐5′‐triphosphate (dCTP), were also determined and 3TCTP/dCTP ratios calculated.
Methods The effects of a number of compounds on 3TC (3H; 1 µm) phosphorylation were investigated by radiometric h.p.l.c. dCTP levels were determined using a template primer extension assay. 3TCTP/dCTP ratios were calculated from these results.
Results The phosphorylation of 3TC was significantly increased in the presence of either hydroxyurea (HU), methotrexate (MTX), or fludarabine (FLU). For example, at 100 µm HU, control 3TCTP levels were increased to 361% of control, whereas at 100 µm FLU, control 3TCTP levels were increased to 155%. dCTP pools were significantly reduced in the presence of HU and FLU, at 100 µm concentrations only. However, for all the above three compounds investigated, the ratio of 3TCTP/dCTP was favourably enhanced (e.g. at 1 µm MTX, 255% of control). Neither ganciclovir (GCV), lobucavir (LCV), penciclovir (PCV), adefovir dipivoxil (ADV), nor foscarnet (FOS) had any significant effects on 3TC phosphorylation or dCTP pools.
Conclusions These results suggest that the activity of 3TC may be potentiated when combined with one of the modulators studied. The lack of an interaction between 3TC and the other anti‐HBV agents is reassuring. These in vitro studies can be used as an initial screen to examine potential interactions at the phosphorylation level.
DOI: 10.1046/j.1365-2125.2000.00302.x
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