Ethaverine Hydrochloride

Phosphodiesterase-4 (PDE4) and PDE5 responsible for the hydrolysis of intracellular cAMP and cGMP, respectively, are promising targets for therapeutic intervention in a wide variety of diseases. Here, we report the discovery of novel, drug-like PDE4 inhibitors by performing a high-throughput drug repurposing screening of 2560 approved drugs and drug candidates in clinical trial studies. It allowed us to identify eight potent PDE4 inhibitors with IC₅₀ values ranging from 0.41 to 2.46 μM. Crystal structures of PDE4 in complex with four compounds, namely ethaverine hydrochloride (EH), benzbromarone (BBR), CX-4945, and CVT-313, were further solved to elucidate molecular mechanisms of action of these new inhibitors, providing a solid foundation for optimizing the inhibitors to improve their potency as well as selectivity. Unexpectedly, selectivity profiling of other PDE subfamilies followed by crystal structure determination revealed that CVT-313 was also a potent PDE5 inhibitor with a binding mode similar to that of tadalafil, a marketed PDE5 inhibitor, but distinctively different from the binding mode of CVT-313 with PDE4. Structure-guided modification of CVT-313 led to the discovery of a new inhibitor, compound 2, with significantly improved inhibitory activity as well as selectivity towards PDE5 over PDE4. Together, these results highlight the utility of the drug repurposing in combination with structure-based drug design in identifying novel inhibitors of PDE4 and PDE5, which provides a prime example for efficient discovery of drug-like hits towards a given target protein.

Ghrelin is known as a hunger hormone and plays a pivotal role in appetite, food intake, energy balance, glucose metabolism, and insulin secretion, making it a potential target for the treatment of obesity and type 2 diabetes. The essential maturation step of ghrelin to activate the GHS-R1a is the octanoylation of the Ser3, which is catalyzed by the ghrelin O-acyltransferase enzyme (GOAT) enzyme. Therefore, the inhibition of GOAT may be useful for treating ghrelin-related diseases.

To discover the novel inhibitors against GOAT enzyme by a fast and accurate computational method, here, we tried to develop the homology model of GOAT. Subsequently, the generated model was stabilized by molecular dynamics simulation. The consecutive process of docking, pharmacophore mapping, and large-scale virtual screening were performed to find the potential hit compounds.

The homology model of the GOAT enzyme was generated and the quality of 3D structures was increased to the highest level of > 99.8% of residue in allowed regions. The model was inserted into the lipid bilayer and was stabilized by molecular dynamics simulation in 200 ns. The sequential process of pharmacophore-based virtual screening led to the introduction of three compounds including ethaverine, kaempferitrin, and reglitazar as optimal candidates for GOAT inhibition.

The results of this study may provide a starting point for further investigation for drug design in the case of GOAT inhibitors and help pave the way for clinical targeting of obesity and type 2 diabetes.