OBJECTIVE: The soluble guanylate cyclase (sGC) activator Cinaciguat (BAY 58-2667) represents a novel class of drugs that selectively activate oxidised sGC. The extent of oxidised sGC depends on the patient's oxidative burden. We here describe two platelet-based assays that allow determining the extent of oxidised sGC and thus provide a basis for an individualised pharmacotherapy. METHODS/RESULTS: Platelets obtained from patients with (n=12) and without (n=12) coronary artery disease (CAD) were examined by flow cytometry (P-selectin expression), and Western blots (vasodilator associated phosphoprotein, VASP-phosphorylation). Results were compared to maximal oxidation of sGC achieved by the oxidising agent ODQ (1H-[1,2,4]oxadiazole[4,3-a]quinoxalin-1-one). Treatment of platelets with Cinaciguat resulted in differential activation of oxidised sGC. Platelet P-selectin expression and VASP-phosphorylation revealed significant differences (p=0.012, p=0.039, respectively) between CAD and non-CAD patients. CONCLUSION: We describe platelet-based assays that allow the determination of patients' oxidative status and thus allow the prediction of pharmacological response to direct sGC activators.