Yasuaki Hanasaki

Discovery of anti-influenza A virus activity of a corynanthe-type indole alkaloid, hirsutine, in vitro and the structure-activity relationship of natural and synthetic analogs

Abstract An indole alkaloid, hirsutine (1), was found to exhibit potent inhibitory effect against influenza A virus in vitro, and the essential structural feature for revealing the activity was elucidated by study of the structure-activity relationship using natural and synthetic derivatives of 1.

Upregulation of HIV-1 replication in chronically infected cells by ingenol derivatives

SummaryWe have previously reported that ingenol derivatives are highly potent inhibitors of human immunodeficiency virus type 1 (HIV-1) replication in acutely infected cells. In this study, however, we have found that some ingenol derivatives strongly enhance the replication of HIV-1 in chronically infected cells at nanomolar concentrations. One of the derivatives could activate nuclear factor κB(NF-κB), a potent inducer of HIV-1 replication, through the activation of protein kinase C (PKC). Whereas another derivative, which affected neither PKC nor NF-κB, significantly enhanced HIV-1 replication, suggesting that a PKC-independent mechanism may also exist in ingenol derivative-induced HIV-1 upregulation.

Anti-HIV-1 activity of thiadiazole derivatives : structure-activity relationship, reverse transcriptase inhibition, and lipophilicity

The structure-activity relationship of the non-nucleoside HIV-1-specific reverse transcriptase (RT) inhibitors 4-phenyl-1,2,5-thiadiazol-3-yl N,N-dialkylcarbamate (TDA) derivatives was investigated with respect to their anti-HIV-1 activity, RT inhibition, and lipophilicity. 4-Phenyl-1,2,5-thiadiazol-3-yl N,N-dimethylcarbamate inhibited HIV-1-induced cytopathic effect (CPE) by 50% at a concentration of 28.8 microM in MT-4 cells. The activity increased more than 100-fold when the hydrogens at the 2-position and the 6-position in phenyl moiety were substituted by chlorines. However, the derivative with a chlorine at the 4-position of phenyl moiety did not show any inhibition of HIV-1 replication at its non-toxic concentrations. All of the 4-(2,6-dichlorophenyl)-1,2,5-thiadiazol-3-yl N-methyl-N-alkylcarbamates proved inhibitory to HIV-1 replication in the nanomolar concentration range. The TDA derivatives that showed anti-HIV-1 activity also inhibited RT activity in an enzymatic assay. However, the TDA derivatives did not show any specific inhibition of a non-nucleoside RT inhibitor (NNRTI)-resistant mutant and its RT activity. When the TDA derivatives were examined for their inhibitory effect on HIV-1 replication in the presence of 50% human serum, the activity significantly decreased depending on-their lipophilicity.

Utilization of wieland furoxan synthesis for preparation of 4-aryl-1,2,5-oxadiazole-3-yl carbamate derivatives having potent anti-HIV activity

Abstract The classical Wieland furoxan synthesis was reinvestigated and this procedure was applied to the preparation of 4-aryl-1,2,5-oxadiazole-3-yl N,N-dialkylcarbamate derivatives, which were found to exhibit potent anti-HIV-1 activity.

Thiadiazole Derivatives: Highly Potent and Selective Inhibitors of Human Immunodeficiency Virus Type 1 (HIV‐1) Replications In Vitro

We have recently reported that thiadiazole (TDA) derivatives are highly potent inhibitors of human immunodeficiency virus type 1 (HIV‐1) replication. These compounds belong to the family of nonnucleoside reverse transcriptase inhibitors (NNRTIs). In an attempt to develop more effective and pharmacologically favorable compounds, novel TDA derivatives have been synthesized and examined for their anti‐HIV‐1 activity in vitro. Among them, RD4‐2217 was found to be the most potent inhibitor of HIV‐1 replication. It inhibited replication of the HTLV‐IIIB strain in MT‐4 cells at a concentration of 6 nM. RD4‐2217 was also inhibitory to clinical isolates and zidovudine‐resistant mutants of HIV‐1. The combination of RD4‐2217 with zidovudine or the protease inhibitor A‐75925 synergistically inhibited HIV‐1 replication. Studies on the emergence of drug‐resistant mutants revealed that, although much higher concentrations (1‐10 μM) were required, RD4‐2217 completely suppressed the breakthrough of HIV‐1 in the supernatants during long‐term culturing of infected cells. Furthermore, RD4‐2217 at low concentrations (10 or 100 nM), in combination with zidovudine, also completely inhibited viral breakthrough. In addition, RD4‐2217 had lower lipophilicity and improved protein binding as compared to its congener RD4‐2024 and loviride. These results suggest that RD4‐2217, one of the TDA derivatives, is worth pursuing as a candidate drug for the treatment of HIV‐1 infections.

Characterization of human immunodeficiency virus type 1 strains resistant to the non-nucleoside reverse transcriptase inhibitor RD4-2217.

The non-nucleoside reverse transcriptase (RT) inhibitor RD4–2217 is a thiadiazole derivative that has proved to be a highly potent and selective inhibitor of human immunodeficiency virus type 1 (HIV-1) replication in vitro. In this study we examined genotypic and phenotypic characteristics of RD4–2217-resistant mutants that have been obtained by serial passage of HIV-1 in MT-4 cells in the presence of increasing concentrations (0.05, 0.25, 1 and 10 μM) of the compound. The strains obtained, IIIB/2217RE/0.05 and IIIB/2217RE/0.25, were two-and 15-fold resistant to RD4–2217, respectively, whereas IIIB/2217RE/1 and IIIB/2217RE/10 displayed 161-and >238-fold resistance, respectively. Both IIIB/2217RE/1 and IIIB/2217RE/10 had two amino acid substitutions, V189I and T240I, in the RT. Furthermore, RD4–2217 did not inhibit the replication of an HIV-1 molecular clone, which had the same mutation, at concentrations up to 10 μM, indicating that the V189I plus T240I mutation confers high-level resistance to RD4–2217. Interestingly, the replicability of IIIB/2217RE/1 and IIIB/2217RE/10 appeared to be lower than that of wild-type IIIB in MT-4 cells, suggesting that the V189I plus T240I mutation may impair the enzymatic activity of HIV-1 RT.

RD6-2198, a novel betain-type fluoroalkylated oligomer, inhibits the replications of human immunodeficiency virus type 1 and other enveloped viruses

We have examined a novel betain-type fluoroalkylated oligomer, RD6-2198, for its inhibitory effects on the replication of human immunodeficiency virus type 1 (HIV-1) and other enveloped viruses, including herpes simplex virus types 1 and 2 (HSV-1 and HSV-2, respectively) and respiratory syncytial virus (RSV) in cell cultures. We have found that the compound is a potent and selective inhibitor of these viruses. RD6-2198 inhibited the replication of HIV-1IIIB at a concentration of 0.85 microg/ml with a selectivity index greater than 59 in MT-4 cells. Furthermore, its 50% effective concentration (EC50) values for HSV-1, HSV-2 and RSV, were 0.51, 0.94 and 3.0 microg/ml, respectively. We found that the RD6-2198 suppressed the gp120-CD4 interaction (as monitored by an enzyme-linked immunosorbent assay (ELISA) method). RD6-2198 also inhibited the binding of anti-gp120 monoclonal antibody to gp120 expressed on MOLT-4/IIIB cells (MOLT-4 cells chronically infected with HIV-1IIIB). However, the compound did not inhibit the interaction of anti-CD4 antibody with CD4. These results suggest that RD6-2198 interacts with the viral envelope glycoprotein and thereby inhibits the viral adsorption process. In addition, RD6-2198 was also found to suppress the proliferation of MOLT-4/IIIB cells. When applied topically, RD6-2198 at a concentration of 10 mg/ml completely protected mice from an intravaginal HSV-2 infection.

Inhibitory effect of 4‐(2,6‐dichlorophenyl)‐1,2,5‐thiadiazol‐3‐yl‐N‐methyl, N‐ethylcarbamate on replication of human immunodeficiency virus type 1 and the mechanism of action

In the search for effective antiviral agents, we have found 4‐(2, 6‐dichlorophenyl)‐1, 2, 5‐thiadiazol‐3‐yl‐N‐methyl, N‐ethylcarbamate (RD4‐2025) to be a highly potent and selective inhibitor of human immunodeficiency virus type 1 (HIV‐1) in vitro. The 50% effective concentration of RD4‐2025 for HIV‐1‐induced cytopathic effect in MT‐4 cells was 37 nM, yet no antiviral activity was observed against HIV‐2. In HIV‐1 reverse transcriptase (RT) assays, RD4‐2025 inhibited both RNA‐dependent and DNA‐dependent DNA polymerase activities of a recombinant HIV‐1 RT with 50% inhibitory concentrations of 0.11 and 3.5 µM, respectively. However, the compound did not affect the activity of human DNA polymerase α. Kinetic studies revealed that the inhibition was noncompetitive with respect to dGTP as the substrate and poly(C)/(dG)12‐18 as the template/primer. These results were in accordance with those of nonnucleoside RT inhibitors (NNRTIs), such as R89439 (an α‐anilinophenylacetamide derivative) and nevirapine, indicating that RD4‐2025 also belongs to the family of NNRTIs.