[Effect of losartan on human platelet activation by thromboxane A2]

Progress toward a Glycoprotein VI Modulator for the Treatment of Thrombosis

Pathogenic thrombus formation accounts for the etiology of many serious conditions including myocardial infarction, stroke, deep vein thrombosis, and pulmonary embolism. Despite the development of numerous anticoagulants and antiplatelet agents, the mortality rate associated with these diseases remains high. In recent years, however, significant epidemiological evidence and clinical models have emerged to suggest that modulation of the glycoprotein VI (GPVI) platelet receptor could be harnessed as a novel antiplatelet strategy. As such, many peptidic agents have been described in the past decade, while more recent efforts have focused on the development of small molecule modulators. Herein the rationale for targeting GPVI is summarized and the published GPVI modulators are reviewed, with particular focus on small molecules. A qualitative pharmacophore hypothesis for small molecule ligands at GPVI is also presented.

Discovery of novel GPVI receptor antagonists by structure-based repurposing

Inappropriate platelet aggregation creates a cardiovascular risk that is largely managed with thienopyridines and aspirin. Although effective, these drugs carry risks of increased bleeding and drug ‘resistance’, underpinning a drive for new antiplatelet agents. To discover such drugs, one strategy is to identify a suitable druggable target and then find small molecules that modulate it. A good and unexploited target is the platelet collagen receptor, GPVI, which promotes thrombus formation. To identify inhibitors of GPVI that are safe and bioavailable, we docked a FDA-approved drug library into the GPVI collagen-binding site in silico. We now report that losartan and cinanserin inhibit GPVI-mediated platelet activation in a selective, competitive and dose-dependent manner. This mechanism of action likely underpins the cardioprotective effects of losartan that could not be ascribed to its antihypertensive effects. We have, therefore, identified small molecule inhibitors of GPVI-mediated platelet activation, and also demonstrated the utility of structure-based repurposing.

[Beyond blood pressure reduction in the treatment of arterial hypertension. Clinical implications of the LIFE study]

To date, blood-pressure lowering has been the main therapeutic objective in patients with arterial hypertension, regardless of the drug used, except for drugs selected for accompanying conditions. The LIFE study, carried out in 9,193 high-risk hypertensive patients (with ECG criteria of left ventricular hypertrophy), has shown that a therapeutic regimen based on losartan combined with a thiazide was accompanied by a significant reduction in the risk of cardiovascular complications in more than 90% of patients compared with atenolol and a thiazide over a mean follow-up period of 4.8 years. The incidence of the primary endpoints (cardiovascular death, stroke, and myocardial infarction) was 11% in the losartan group and 13% in the atenolol group (13% relative risk reduction, p = 0.021). Losartan therapy was associated with more benefits in stroke risk reduction and in the development of new cases of diabetes. In the analysis of the subgroup of 1,195 patients with hypertension and diabetes included in the LIFE study, losartan had a special prognostic benefit. One of the cardiovascular events included as a primary endpoint was observed in 18% of the losartan-treated patients and in 23% of the atenolol-treated patients (24% relative risk reduction, p = 0.031). The LIFE trial showed that losartan produced better cardiovascular protection than atenolol, a similar blood pressure reduction, and was better tolerated. This drug seems to confer extra cardiovascular protection in addition to reducing blood pressure.