HYDROXYETHYLAMINE ISOSTERE INHIBITORS IN COMPLEX WITH HIV-1 PROTEASE

J. Dohnalek^1,2, J. Hasek², J. Brynda³, M. Fabry³, J. Sedlacek³, J. Konvalinka⁴, M. Hradilek⁴, M. Soucek⁴

¹Faculty of Nuclear Sciences and Physical Engineering, Czech Technical University, Brehova 7, 110 00 Praha 1, Czech Republic,
²Institute of Macromolecular Chemistry AS CR, Heyrovského nám. 2, 162 06 Praha 6, CR,
³Institute of Molecular Genetics AS CR, Flemingovo nám. 2, 166 37 Praha 6, CR,
⁴Institute of Organic Chemistry and Biochemistry AS CR, Flemingovo nám. 2, 166 37 Praha 6, CR

Keywords: HIV, protease, drug design, inhibitor, X-ray

The initial class of substrate-based HIV-1 protease inhibitors contained transition-state-analogue hydroxyl group attached to chiral carbon with preferred S configuration. Later on, some clinically successful HIV-1 protease inhibitors proved more potent when the isostere carbon bearing hydroxyl group was in R configuration.

A new series of subnanomolar HIV-1 protease inhibitors was developed (1) aiming for more potent and more mutation resistant drugs. Up to these days at least 22 mutation sites have been reported in HIV-1 protease isolated from bodies of patients treated with clinically proved drugs. Our hydroxyethylamine isostere inhibitors show high affinity in vitro to several protease mutants tested by now and their structure can provide a starting point for optimisation leading to bio-available anti AIDS drugs effectively inhibiting both the wild type HIV protease and its mutants.

In order to make possible observation of subtle structural changes in HIV-1 protease complexes responsible for large differences in inhibition constants, four complexes of HIV-1 protease with inhibitors Boc­Phe­Y[(S/R)-CH(OH)CH₂NH]-Phe-Glu/Gln-Phe-NH₂ (slashes denote alternatives) have been subjected to X-ray crystallographic analysis to elucidate the change of affinity (K_i=0,12÷33,0 nM) as a result of Glu/Gln alteration at the P₂' position and the chirality alternation at the tetrahedrally coordinated transition-state-analogue carbon.

Kinetic data indicate that the hydroxyl group has lower influence on the inhibitor potency in comparison with the strong dependence of binding affinity on the P₂' group. This opens a question of relevance of the isostere hydroxyl group formerly considered necessary for the effective inhibition of the enzyme.

1. J. Konvalinka, et al., Configurations of Diastereomeric Hydroxyethylene Isosteres Strongly Affect Biological Activities of Series of Specific Inhibitors of Human Immunodeficiency Virus Proteinase. Eur. J. Biochem. 250 (1997) 559-566