Antiplatelet pyrazolopyridines derivatives: pharmacological, biochemical and toxicological characterization

Platelet aggregation is one of the main events involved in vascular thrombus formation. Recently, N'-substituted-phenylmethylene-3-methyl-1,6-diphenyl-H-1-pyrazolo[3,4-b]pyridine-4-carbohydrazides were described as antiplatelet derivatives. In this work, we explore the properties of these antiplatelet agents through a series of pharmacological, biochemical and toxicological studies. The antiplatelet activity of each derivative was confirmed as 3a, 3b and 3h significantly inhibited human platelet aggregation induced by arachidonic acid, with no detectable effect on clotting factors or healthy erythrocytes. Importantly, mice treated with derivative 3a showed a higher survival rate at an in vivo model of pulmonary thromboembolism with a lower bleeding risk in comparison to aspirin. The in silico studies pointed a series of structural parameters related to thromboxane synthase (TXS) inhibition by 3a, which was confirmed by tracking plasma levels of PGE(2) and TXB2 through an in vitro enzyme immunoassay. Derivative 3a showed selective TXS inhibition allied with low bleeding risk and increased animal survival, revealing the derivative as a promising candidate for treatment of cardiovascular diseases.