Antiviral Drugs - Drug Design and Discovery - page 398

PR

PRPP

PRPP synthetase

NH 2

NH 2 NH 2

N

N

N

N

N

N

N

N N

N

N

N

O

O

P P P O

P P P

AMP
kinase

AMP
kinase

PMEA PMEAp PMEApp

Reverse transcriptase

DNA

RNA

FIGURE 24.3 Mechanism of antiviral action of tenofovir (PMPA) is similar to that of adefovir (PMEA).
PMEA and PMPA need to be phosphorylated, in one or two steps, to the diphosphate form before they
interfere, as chain terminators, with the RT reaction. (After De Clercq, E., Expert Rev. Anti-infect. Ther .,
1, 21, 2003a.)

form, and, after the removal of the diphosphate group, incorporation at the 3 ′ -end of the viral DNA

chain (Figure 24.3).
Principal indication(s) : HIV infection as such or in combination with emtricitabine (see above), or
in combination with emtricitabine and efavirenz (see below).
Administered : Orally as a once-daily 300 mg tablet (Viread) or a 300 mg TDF/200 mg emtricitabine
tablet (Truvada) or a 300 mg TDF/200 mg emtricitabine/600 mg efavirenz tablet (Atripla ® ).