PNU-140690 is a member of a new class of nonpeptidic human immunodeficiency virus (HIV) protease inhibitors (sulfonamide-containing 5,6-dihydro-4-hydroxy-2-pyrones) discovered by structure-based design. PNU-140690 has excellent potency against a variety of HIV type 1 (HIV-1) laboratory strains and clinical isolates, including those resistant to the reverse transcriptase inhibitors zidovudine or delavirdine. When combined with either zidovudine or delavirdine, PNU-140690 contributes to synergistic antiviral activity. PNU-140690 is also highly active against HIV-1 variants resistant to peptidomimetic protease inhibitors, underscoring the structural distinctions between PNU-140690 and substrate analog protease inhibitors. PNU-140690 retains good antiviral activity in vitro in the presence of human plasma proteins, and preclinical pharmacokinetic studies revealed good oral bioavailability. Accordingly, PNU-140690 is a candidate for clinical evaluation.

Bisheteroarylpiperazine compounds are nonnucleoside reverse transcriptase inhibitors of human immunodeficiency virus type 1 (HIV-1). To provide a rationale for combination therapy with a second-generation bisheteroarylpiperazine, we investigated the effect of U-90152 in combination with 3'-azido-3'-deoxythymidine (AZT) or 2',3'-dideoxycytidine (ddC). HIV-1-infected cells were cultured in the presence of test compounds, and drug effects on p24 core antigen production were measured by an enzyme-linked immunosorbent assay. In a CD4+ T-cell line (H9) infected with HIV-1IIIB, the 501% effective concentrations for U-90152, AZT, and ddC were 6.0, 80.4, and 31.8 nM, respectively. In human peripheral blood mononuclear cells infected with the molecularly cloned clinical isolate HIV-lJRCSF, the 50%o effective concentrations for U-90152, AZT, and ddC were 5.3, 5.9, and 25.0 nM, respectively. Over a range of drug concentrations (U-90152 and AZT at 0.3, 1, 3, 10, and 30 nM; ddC at 3, 10, 30, and 100 nM), U-90152 in combination with AZT or ddC synergistically inhibited the replication of a laboratory-adapted strain and a clinical isolate of HIV-1.The bisheteroarylpiperazine (BHAP) class of compounds has been shown to inhibit the reverse transcriptase (RT) of human immunodeficiency virus type 1 (HIV-1) and block HIV-1 replication in culture cells (1,3,7,8,28,33). The BHAPs belong to a structurally diverse group of compounds known as the nonnucleoside RT inhibitors. These compounds inhibit the HIV-1 RT by binding to a common region of the enzyme away from the substrate binding site (8,12,33). In contrast, nucleoside analog inhibitors, such as 3'-azido-3'-deoxythymidine (AZT), 2',3'-dideoxyinosine, and 2',3'-dideoxycytidine (ddC), mimic the normal deoxynucleotide triphosphate substrate for RT and thus act as chain terminators during proviral synthesis (31). Other nonnucleoside RT inhibitors include dipyridodiazepinones (nevirapine) (18, 23), pyridinones (L-697,661) (12), thiobenzimidazolone compounds (TIBO Ro82150) (25), and the more recently reported TSAO [2',5' -bis-O-(tert-butyl-dimethylsilyl)-3' -spiro-5"-(4"-amino-1",2"-oxathiole-2",2"-dioxide)pyrimidine] and HEPT {1-[(2-hydroxyethoxy)methyl]-6-(phenylthio)thymine} compounds (2, 32).Drug

PNU-140690 (sulfonamide-containing 5,6-dihydro-4-hydroxy-2-pyrone) is a potent, nonpeptidic inhibitor of the human immunodeficiency virus type 1 (HIV-1) protease currently under clinical evaluation. PNU-140690 and ritonavir were studied in two-drug combinations against the replication of HIV-1 clinical isolates in peripheral blood mononuclear cells. A ritonavir-sensitive (301-1x) and -resistant (301-6x) isolate pair derived from an individual before and after monotherapy with ritonavir were used. These isolates showed no significant difference in sensitivity to PNU-140690, but isolate 301-6x was more than 50-fold less sensitive to ritonavir than isolate 301-1x. Mathematical analysis showed that the combination of various concentrations of PNU-140690 with ritonavir yielded additive to moderately synergistic antiviral effects against the ritonavir-sensitive isolate and stronger synergy against the ritonavir-resistant isolate. The mechanism of synergy was not investigated, but the results suggested that both the virological and the observed in vitro pharmacological effects may have contributed to the observed synergy. Importantly, no significant antagonism was observed with the drug combinations studied. These data suggest that PNU-140690 may be useful in combination regimens with a structurally unrelated protease inhibitor such as ritonavir.

SummaryDelavirdine (DLV), a non-nucleoside human immunodeficiency virus type 1 (HIV-1) reverse transcriptase inhibitor, was evaluated in two-and three-drug combination regimens with lamivudine (3TC) and zidovudine (ZDV). The effect of continuous drug treatment on HIV-1JR-CSF replication in human peripheral blood mononuclear cells was measured by an ELISA for p24 core antigen. Drug synergy, estimated by the combination index method and the method of Pritchard & Shipman, was observed when DLV was combined with 3TC over a range of drug concentrations (DLV at 1, 3, 10, 30 and 100 nM; 3TC at 3, 10,30, 100 and 300 nM). Two-drug combinations of ZDV and DLV at a 1:3 ratio or ZDV and 3TC at a 1:10 ratio were synergistic at greater than 75% inhibition levels. Three-drug combinations of ZDV, DLV and 3TC (ZDV at 0.3, 1,3 and 10 nM; DLV at 1, 3, 10 and 30 nM; 3TC at 3, 10,30 and 100 nM) at the ratio of 1:3:10 also yielded significant synergistic effects. None of the combinations studied showed significant additive or synergistic drug toxicity. These in vitro data suggest that DLV should be evaluated in two-and three-drug combinations with 3TC and ZDV in clinical trials.