Antiretroviral Therapy: New Agents, New Combinations, and Virologic Responses
Friday, 10 am - 12:30 pm
Presentation Time: 10:00 am
Background: Inhibition of HIV reverse transcriptase (RT) is the backbone of current antiretroviral therapies. We have identified a new class of HIV RT inhibitors that block the polymerization reaction via a mechanism of action that is clearly different from that of current nucleoside- (NRTI), nucleotide- (NtRTI) or non-nucleoside RT inhibitors (NNRTI).
assays were performed in MT4 cells with an
Results: Screening of a random chemical library using a cell-based antiviral assay led to the discovery of a new class of HIV-1 inhibitors with a non-nucleoside/nucleotide structure. Compound-1, a prototype of this class, displayed good potency against HIV-1 (EC50 = 30 nM) and time-of-addition experiments and enzymatic assays proved that it inhibits the reverse transcription step. A reduced susceptibility of < 10-fold was observed when Compound-1 was tested on HIV-2. Enzyme kinetics studies showed that Compound-1 is a competitive inhibitor of nucleotide incorporation by HIV-1 RT and HIV-2 RT. Three other biochemical features differentiate this compound from current NNRTI: the presence of physiological concentrations of ATP in an enzymatic assay increased the potency of Compound-1 more than 10-fold (IC50 = 30 nM); inhibition of RT-mediated polymerization was observed only when using p(rA)p(dT) or p(rG)p(dC) as the primer-template, and not in the presence of p(rC)p(dG) or p(rU)p(dI); and an RT translocation assay showed that Compound-1 forces the enzyme to move on its primer-template in the same way as when a dNTP binds the enzyme.
assays and biochemical experiments showed that Compound-1 inhibits HIV RT by a
mechanism of action that is clearly different from that of current NNRTI and N(t)RTI. The competitive mode of RT inhibition and the
effect on enzyme translocation suggest that Compound-1 blocks the
Keywords: New Antiretroviral Agents; Reverse Transcriptase Inhibitors; Enzymology