CADA, a novel CD4-targeted HIV inhibitor, is synergistic with various anti-HIV drugs in vitro.
OBJECTIVE
To evaluate the anti-HIV-1 activity of the cyclotriazadisulfonamide CADA against primary isolates in vitro and the combination of CADA with approved anti-HIV drugs for potential synergy.


METHODS
Peripheral blood mononuclear cells (PBMC) were treated with CADA and infected with 16 different clinical isolates. After 8 days of infection, the median inhibitory concentration (IC50) was calculated from the p24 viral antigen content in the supernatant. MT-4 cells were infected with HIV-1NL4.3 and then cultured with CADA or other antiretroviral drugs (i.e., several reverse transcriptase, protease and entry inhibitors), alone and in combination. After 4 days, IC50 was determined for the various drugs in replicate assays. Analysis of combined effects was performed using the median effect principle (CalcuSyn; Biosoft).


RESULTS
The entry inhibitor CADA exerted a potent and consistent anti-HIV-1 activity against a wide range of R5, R5/X4 and X4 primary isolates in PBMC. From the two-drug studies, combination indices showed synergy between CADA and reverse transcriptase inhibitors (zidovudine, stavudine, lamivudine, zalcitabine, didanosine, abacavir, tenofovir, nevirapine, delavirdine and efavirenz), and protease inhibitors (lopinavir, saquinavir, indinavir, nelfinavir, amprenavir and ritonavir). In addition, the combination of CADA with the gp41 fusion inhibitor T-20 (enfuvirtide), the CXCR4 antagonist AMD3100 and the gp120-specific interacting plant lectins from Galanthus nivalis (GNA) and Hippeastrum hybrid (HHA) also resulted in a synergistic inhibition.


CONCLUSIONS
Compounds that can specifically downmodulate the CD4 receptor in PBMC have broad-spectrum anti-HIV activity against primary isolates and act synergistically when used in conjunction with currently available antiretroviral drugs. They deserve further study as potential candidate anti-HIV drugs.
Vermeire
Kurt
K
Rega Institute for Medical Research, Katholieke Universiteit Leuven, B-3000 Leuven, Belgium. kurt.vermeire@rega.kuleuven.ac.be
Princen
Katrien
K
Hatse
Sigrid
S
De Clercq
Erik
E
Dey
Kaka
K
Bell
Thomas W
TW
Schols
Dominique
D
D019380:Anti-HIV Agents / Q000494:pharmacology*; D023241:Antiretroviral Therapy, Highly Active; D015704:CD4 Antigens / Q000187:drug effects*; D002460:Cell Line; D004357:Drug Synergism; D005434:Flow Cytometry; D015658:HIV Infections / Q000188:drug therapy* / Q000276:immunology; D015497:HIV-1; D006571:Heterocyclic Compounds / Q000737:chemistry / Q000494:pharmacology*; D006801:Humans; D007963:Leukocytes, Mononuclear / Q000187:drug effects / Q000276:immunology* / Q000821:virology; D008826:Microbial Sensitivity Tests; D018894:Reverse Transcriptase Inhibitors / Q000494:pharmacology*
C498074:9-benzyl-3-methylene-1,5-di-p-toluenesulfonyl-1,5,9-triazacyclododeane; D019380:Anti-HIV Agents; D015704:CD4 Antigens; D006571:Heterocyclic Compounds; D018894:Reverse Transcriptase Inhibitors