Structure-based optimisation of 2-aminobenzylstatine derivatives: potent and selective inhibitors of the chymotrypsin-like activity of the human 20S proteasome

We have identified 2-aminobenzylstatine derivatives that inhibit non-covalently the chymotrypsin-like activity of the human 20S proteasome. A structure-based optimisation approach has allowed us to improve the potency of this structural class of proteasome inhibitors from micromolar to nanomolar level. The new derivatives showed good selectivity against the trypsin-like and post-glutamyl-peptide hydrolytic activities of this enzyme.

A new structural class of selective and non-covalent inhibitors of the chymotrypsin-like activity of the 20S proteasome

We describe the identification and in vitro characterization of a series of 2-aminobenzylstatine derivatives that inhibit non-covalently the chymotrypsin-like activity of the 20S proteasome. Our initial SAR data demonstrate that the 2-aminobenzylstatine core structure can effectively serve as the basis for designing potent, selective and non-covalent inhibitors of the chymotrypsin-like activity of the 20S proteasome.

Modeling of the binding mode of a non-covalent inhibitor of the 20S proteasome. Application to structure-based analogue design

The 2-aminobenzvlstatine derivative I is a 20S proteasome inhibitor of a novel chemical type identified by high throughput screening. The compound specifically inhibits the chymotrypsin-like catalytic activity of the human proteasome with an IC50 value in the micromolar range. Using the crystal structure of the yeast proteasome, we modeled the structure of the human proteasome in complex with 1. As one of the first applications of the model in our oncology programme targeting the proteasome, we designed an analogue of the inhibitor having enhanced stacking/hydrophobic interactions with the enzyme. One order of magnitude in inhibitory potency was gained.

X-ray structure and conformational dynamics of the HIV-1 protease in complex with the inhibitor SDZ283-910: agreement of time-resolved spectroscopy and molecular dynamics simulations

Based on the X-ray structure of the human immunodeficiency virus type-1 (HIV-1) protease in complex with the statine-derived inhibitor SDZ283-910, a 542 ps molecular dynamics trajectory was computed. For comparison with the 805 ps trajectory obtained for the uncomplexed enzyme, the theoretical fluorescence anisotropy decay of the unliganded protease and the inhibitor complex was calculated from the trajectories of the Trp6A/Trp6B and Trp42A/Trp42B transition dipole moments. This enabled us to directly compare the simulated data with the experimental picosecond time-resolved fluorescence data. Fitting both experimental and simulated data to the Kohlrausch-Williams-Watts (KWW) function exp(-t/tauk)beta revealed a very good agreement for the uncomplexed protease as well as for the SDZ283-910 complex. Binding of the inhibitor induced a faster decay of both the experimental and the computed protease fluorescence anisotropy decay. By this integrative approach, the atomic detail of inhibitor-induced changes in the conformational dynamics of the HIV-1 protease was experimentally verified and will be used for further inhibitor optimisation.

Paracyclophanes: a novel class of water-soluble inhibitors of HIV proteinase

A versatile synthesis of functionalized para- and metacyclophanes (macrocycles with one or more aromatic rings incorporated; ansa-compounds) has been developed. Cyclophanes constitute a novel building block for potent human immunodeficiency virus (HIV) protease inhibitors. The synthesis of the macrocyclic ring system was achieved by regio- and stereospecific ring opening of N-protected 4-amino-2,3-epoxy-5-phenylpentanoates with appropriate alpha, omega-diamines and consecutive ring closure under high dilution conditions. The resulting macrocyclic building blocks enabled further broad and flexible derivation. Paracyclophanes, containing oxyethylene substructures, were found to dissolve in phosphate-buffered saline at concentrations as high as 3 mg/mL at physiological pH. Several derivatives with Ki values lower than 10 nM and antiviral activities in the range of 15-50 nM have been obtained. The influence of the ring size and of the substitution pattern of the cyclophane moiety on enzyme inhibition, antiviral activity, and water solubility are discussed. Preliminary data on oral bioavailability in mice are given for selected compounds.

Inhibitors of human immunodeficiency virus type 1 protease containing 2-aminobenzyl-substituted 4-amino-3-hydroxy-5-phenylpentanoic acid: synthesis, activity, and oral bioavailability

Systematic modifications of HIV protease inhibitor (2R,3S,4S)-4-[[(benzyloxycarbonyl)-L-valyl]-amino]-3-hydroxy-2-[(4- methoxybenzyl)amino]-5-phenylpentanoyl)-L-valine 2-(aminomethyl)- benzimidazole amide led to a novel series of inhibitors with shortened, modified carboxy terminus. Their synthesis, in vitro enzyme inhibitory data, and antiviral activities are reported. Of particular interest are derivatives featuring the (1S,2R)-1-amino-2-hydroxyindan moiety at the P2'-position since some of them exhibit substantial oral bioavailability in mice. The influence of aqueous solubility and structural parameters on the oral resorption of the inhibitors is discussed. Optimum enhancement of oral bioavailability was observed with L-tert-leucine in P2-position, resulting in the discovery of (2R,3S,4S)-4-[[(benzyloxycarbonyl)-L-tert-leucyl]- amino]-3-hydroxy-2-[(4-methoxybenzyl)amino]-5-phenylpentanoic acid (1S,2R)-1-amino-2-hydroxyindan amide which combines high antiviral activity (IC50 = 250 nM) with a good pharmacokinetic profile (AUC = 82.5 microM.h at a dose of 125 mg/kg po in mice).