INHIBITION OF THE CELLULAR REV RESPONSE AND HIV-1 REPLICATION BY 8-ALKYL-2-(4-PYRIDYL)PYRIDO[2,3-D] PYRIMIDIN-5(8H)-ONES

A high-capacity, 96-well plate assay in COS-1 cells was developed to screen for inhibitors of the essential HIV-1 Rev response. The assay used Rev-induced expression and cell excretion of the p24 protein from the HIV-1 gagpol gene as a readout. Co-expression of beta-galactosidase was used as a specificity control. Using this assay as a drug discovery screen, the authors discovered a series of 8-alkyl-2-(4-pyridyl)pyrido[2,3-d]pyrimidin-5(8H)-ones that inhibited the primary Rev response in COS-1 cells with IC(50)s in the range 2-20 mu M. These compounds also inhibited HIV-1 strain IIIB replication in human H9 cells (T-cell lymphoma) with IC(50)s in the same concentration range. Limited structural information suggests that alkyl substituent on N(8) influences potency of this series. These compounds might be the first reported small-molecule inhibitors of HIV-1 replication which act by inhibiting the essential Rev response; further studies in T-cells are in progress to confirm this hypothesis.