Quantitative structure-activity relationship studies on benzodiazepine receptor binding: recognition of active sites in receptor and modelling of interaction

Investigation of [3H]diazepam derivatives as allosteric modulators of GABAA receptor α1β2γ2 subtypes: combination of molecular docking/dynamic simulations, pharmacokinetics/drug-likeness prediction, and QSAR analysis

In this paper, a data set of [³H] diazepam derivatives was analyzed using various computational methods: molecular docking/dynamic simulations, and QSAR analysis. The main aims of these studies are to understand the binding mechanisms by which benzodiazepines allosterically modulate GABA_A receptor α₁β₂γ₂ subtypes, from inducing neuronal inhibition at lower doses to the anesthetic effect at higher doses, and also, to define the structural requirements that contribute to improving the response of GABA_A/α₁β₂γ₂ receptor to benzodiazepine drugs. The results of the molecular docking study allowed selecting Ro12-6377 and proflazepam as the best modulators for the four binding sites simultaneously. Subsequently, the stability of the selected complexes was investigated by performing molecular dynamics simulation. The latter confirmed the features of both modulators to exert direct effects on the chloride-channel lining residues. Pharmacokinetics and drug-likeness profile were assessed through in silico tool. Furthermore, a QSAR analysis was conducted using an improved vemolecular dynamics simulations proposed byrsion of PLS regression. The goodness of fit and the predictive power of the resulting PLS model were estimated according to internal and external validation parameters: R² = 0.632, R²_adj = 0.584, F = 12.806; p-value = 6.2050e − 07, Q²_loo = 0.639, and Q²_F3 = 0.813. Clearly, the obtained results ensure the predictive ability of the developed QSAR model for the design of new high-potency benzodiazepine drugs.

Development of Neural Network QSPR Models for Hansch Substituent Constants. 1. Method and Validations

In an attempt to develop predictive models for Hansch substituent constants for less common substituents, neural network QSPR (Quantitative Structure-Property Relationship) studies were conducted to correlate Hansch substituent constants for hundreds of chemically diverse functional groups with two different molecular descriptor sets. The Hansch substituent constants under study were pi, MR, F and R, describing the hydrophobic, steric/polarizability, and electronic (field and resonance) characteristics of the substituents, respectively. E-state descriptors were used for pi and MR, while the molecular descriptor set based upon the approach of Kvasnicka, Sklenak, and Pospichal (J. Am. Chem. Soc. 1993, 115, 1495-1500) was adopted for F and R. Both QSPR models demonstrated good predictivity in test sets.

11C-labeled 2'-iododiazepam for PET studies of benzodiazepine receptors: synthesis and comparison of biodistribution with its radioiodinated compound

For PET studies of benzodiazepine receptors, N-11C-methyl-2'-iododiazepam (2'-IDZ) was synthesized by N-methylation of its desmethyl derivative with 11C-methyl iodide, and was subsequently purified by HPLC. The labeling and purification procedures were completed within 45 min after 11C-methyl iodide trapping, and the radiochemical yield (corrected for decay) was approximately 40% based on the initial trapped radioactivity of 11C-methyl iodide. Biodistribution studies in mice demonstrated that 11C-2'-IDZ was rapidly and noticeably accumulated in the brain, and subsequently decreased with time. Accumulation was greater in the cortex than in other brain regions. When compared with 125I-2'-IDZ, the distribution was almost the same until 5 min after injection, but levels were low after 20 min. Metabolic studies indicated that the difference between these two compounds in the time course of brain radioactivity distribution may be due to N-demethylation in vivo.