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Session 97 Poster Abstracts
New Antiretroviral Agents: RTIs and Pis
Thursday, 1:30 - 3:30 pm
Hall A


559    
HIV-1 Acquires Resistance to New NNRTI, Thiazol Derivatives, through Steric Hindrance with Multiple Mutations
Eiichi Kodama*1, N Masuda2, M Orita3, O Yamamoto3, M Fujii3, S Kageyama3, M Ohta3, T Hatta3, H Inoue3, H Suzuki3, K Sudo3, Y Shimizu3, and M Matsuoka1
1Inst for Virus Res, Kyoto Univ, Japan; 2Yamanouchi Pharma Co, Ltd Tsukuba, Japan; and 3Yamanouchi Pharma Co, Ltd Tsukuba, Japan

Background:  We recently reported that a novel thiazol derivative, RD4-2217, has anti-HIV activity not only wild types but also various non-nucleoside reverse transcriptase inhibitors (NNRTI) resistant variants except for a variant containing Y181C substitution in the RT. Here we identify novel thiazole derivatives, YM- 215389 and -228855, that show different resistance profiles. 

Methods:  Resistant variants were selected in vitro by propagating HIV-1LAI in the presence of increasing dose of the drug. Various recombinant HIV-1 clones (HIV-1NL101 background) were generated using the site directed mutagenesis. Antiviral activity was determined using HeLa CD4/LTR-β-Gal cells. Docking and molecular modeling studies were performed with the program GOLD and Sybyl.

Results:  The phenotypic and genotypic analyses revealed that the isolated variants showed marginal cross resistance but distinct resistance profiles although the structural differences between YM-215389 and -228855 are only a bromo- and a cyano-moiety at the benzene ring, and a chlor- and a methyl-moiety at thiazole ring, respectively. The variants resistant to YM- 215389 showed modest cross resistance to nevirapine (NVP) and efavirenz whereas that to YM-228855 showed strong cross resistance to NVP. Primary mutations for YM- 215389 and -228855 resistances were V106L (16 fold) and Y181I (540-fold), respectively. However, 4 amino acids substitutions (V106L/V108I/E138K/L214F) were needed to develop high resistance to YM-215389. Interestingly, a widely observed polymorphism, L214F, plays a role for enhancement of resistance to YM-215389 and -228855. Our docking studies revealed that hydrophobic benzene and thiazol rings of YM-215389 and -228855 bind to at least 13 amino acids located in the RT hydrophobic NNRTI binding pocket whereas the hydrophilic sulfon-amide-moiety turned to outside of the pocket. Steric hindrance by V106L for benzene ring and E138K/Y181I for thiazol ring is considered to be mechanism of the resistance to YM- 215389 and -228855.

Conclusions:  Thiazol derivatives bind to the pocket through multiple amino acids interaction. It is consistent with the data that 4 mutations were needed to develop the resistance. Our data may help the development of compounds to suppress drug resistant HIV replication without the cross resistance.

Keywords: NNRTI; resistance; steric hindrance