Design, synthesis and anticonvulsive activity of analogs of γ-vinyl GABA

Discovery of Novel Isonipecotic Acid-Based Heteroaryl Amino Acid Derivatives as Potential Anticonvulsant Agents: Design, Synthesis, In-Silico ADME Study, and Molecular Docking Studies

Background

Epilepsy is a neurological disorder characterized by anomalous brain activity, convulsions, and odd behavior. Several substituted-(naphthalen-2-yl)-3-(1H-indol-3-yl) allyl)-1,4-dihydropyridine-4-carboxylic acid derivatives (5a-j) were intended to be produced in the current research effort to reduce convulsions and seizures.

Materials and Methods

The newly developed compounds were produced by the prescribed process. Numerous methods (infrared spectroscopy (IR), nuclear magnetic resonance (NMR), mass, elemental analysis, etc.) were used to characterize these substances. Several models were used to test each of these molecules for anticonvulsant activity. By using the rotarod and ethanol potentiation techniques, neurotoxicity was also evaluated. The study meticulously examined each parameter and showed absorption, distribution, metabolism, and excretion (ADME) predictions for each of the 10 congeners that were produced. In addition, studies on molecular docking employed the gamma amino butyric acid (GABA)-A target protein.

Results

Anticonvulsant screening results identified compounds 5f, 5h, 5d, and 5b as the most efficacious of the series. All synthesized equivalents largely passed the neurotoxicity test. The results of molecular docking revealed significant interactions at the active site of GABA-A with LEU B: 99, TYR A: 62, Ala A: 174, and THR B: 202, and the outcomes were good and in agreement with in vivo findings.

Conclusions

The study's findings showed that some substances had promising anticonvulsant properties that were comparable to those of the standard drug. The highly active novel anticonvulsant analogs may therefore represent a possible lead, and additional studies may result in a potential new drug candidate.

Positive Predictive Value Surfaces as a Complementary Tool to Assess the Performance of Virtual Screening Methods

BACKGROUND

Since their introduction in the virtual screening field, Receiver Operating Characteristic (ROC) curve-derived metrics have been widely used for benchmarking of computational methods and algorithms intended for virtual screening applications. Whereas in classification problems, the ratio between sensitivity and specificity for a given score value is very informative, a practical concern in virtual screening campaigns is to predict the actual probability that a predicted hit will prove truly active when submitted to experimental testing (in other words, the Positive Predictive Value - PPV). Estimation of such probability is however, obstructed due to its dependency on the yield of actives of the screened library, which cannot be known a priori.

OBJECTIVE

To explore the use of PPV surfaces derived from simulated ranking experiments (retrospective virtual screening) as a complementary tool to ROC curves, for both benchmarking and optimization of score cutoff values.

METHODS

The utility of the proposed approach is assessed in retrospective virtual screening experiments with four datasets used to infer QSAR classifiers: inhibitors of Trypanosoma cruzi trypanothione synthetase; inhibitors of Trypanosoma brucei N-myristoyltransferase; inhibitors of GABA transaminase and anticonvulsant activity in the 6 Hz seizure model.

RESULTS

Besides illustrating the utility of PPV surfaces to compare the performance of machine learning models for virtual screening applications and to select an adequate score threshold, our results also suggest that ensemble learning provides models with better predictivity and more robust behavior.

CONCLUSION

PPV surfaces are valuable tools to assess virtual screening tools and choose score thresholds to be applied in prospective in silico screens. Ensemble learning approaches seem to consistently lead to improved predictivity and robustness.

Structural modifications of (1S,3S)-3-amino-4-difluoromethylenecyclopentanecarboxylic acid, a potent irreversible inhibitor of GABA aminotransferase

Low brain levels of the inhibitory neurotransmitter gamma-aminobutyric acid (GABA) lead to convulsions. Inhibition of GABA aminotransferase increases the concentration of GABA and can terminate the convulsions. Earlier we reported the synthesis of (1S,3S)-3-amino-4-difluoromethylenecyclopentanecarboxylic acid (2), which is 186 times more potent an inactivator of GABA aminotransferase than the epilepsy drug S-vigabatrin. The corresponding dichloromethylene analogue of 2 (compound 3) has been made, but it shows only weak reversible inhibition of GABA aminotransferase. However, the tetrazole isostere of 2 (compound 4) has been found to be a time-dependent inactivator of GABA aminotransferase. Although it is 20 times less potent than carboxylic acid 2, it is 2.5 times more potent than S-vigabatrin. A calculation of the ClogP values indicates that 4 is the most lipophilic of the three, being 69 times more lipophilic than 2 and 55 times more lipophilic than S-vigabatrin, indicating potential for improved bioavailability.