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Skip Navigation LinksHome > March 13, 2010 - Volume 24 - Issue 5 > Abacavir and tenofovir disoproxil fumarate co-administration...
AIDS:
doi: 10.1097/QAD.0b013e32833676eb
Clinical Science

Abacavir and tenofovir disoproxil fumarate co-administration results in a nonadditive antiviral effect in HIV-1-infected patients

Goicoechea, Miguela; Jain, Soniaa; Bi, Lucunb; Kemper, Carolc; Daar, Eric Sd; Diamond, Catherinee; Ha, Belindaf; Flaherty, Johng; Sun, Shellya; Richman, Douglasa,h; Louie, Stani; Haubrich, Richarda; the California Collaborative Treatment Group

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Abstract

Objectives: To evaluate a potential pharmacodynamic/pharmacokinetic interaction between abacavir (ABC) and tenofovir disoproxil fumarate (TDF).

Design and methods: This randomized trial compared 7 days of ABC or TDF monotherapy, separated by a 35-day washout, with 7 days of ABC + TDF dual-therapy in treatment-naive, HIV-1-infected patients. During each 7-day course, the slope of the phase I viral decay was estimated and steady-state intracellular concentrations of carbovir triphosphate (CBV-TP), deoxyguanosine triphosphate (dGTP), tenofovir diphosphate (TFV-DP) and deoxyadenosine triphosphate (dATP) were determined.

Results: Twenty-one participants were randomized to initial monotherapy with ABC (n = 11) or TDF (n = 10). The addition of TDF did not increase the slope of viral decay compared to ABC alone (−0.15 log10 per day vs. −0.16 log10 per day, respectively). No decrease in CBV-TP or TFV-DP between monotherapy and dual-therapy was observed. However, intracellular dATP concentrations increased between monotherapy and dual-therapy [median dATP (fmol/106 cells) 3293 vs. 4638; P = 0.08], although this difference was significant only among patients randomized to TDF [median dATP (fmol/106 cells) 3238 vs. 4534; P = 0.047]. A lower TFV-DP-to-dATP ratio was associated with reduced viral decay during dual-therapy (ρ = −0.529; P = 0.045).

Conclusion: In this study, the viral decay during ABC and TDF dual-therapy was similar to that during ABC therapy alone, suggesting a nonadditive antiviral effect. This negative pharmacodynamic interaction was not explained by changes in CBV-TP or TFV-DP concentrations. Rather, modest increases in endogenous dATP pools were associated with reduced antiviral potency of TDF during co-administration with ABC.

© 2010 Lippincott Williams & Wilkins, Inc.

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