Abacavir increases platelet reactivity via competitive inhibition of soluble guanylyl cyclase

OBJECTIVE: To provide a molecular mechanism that explains the association of the antiretroviral guanosine analogue, abacavir, with an increased risk of myocardial infarction. DESIGN: Drug effects were studied with biochemical and cellular assays. METHODS: Human platelets were incubated with nucleoside analogue drugs ex vivo. Platelet activation stimulated by ADP was studied by measuring surface P-selectin with flow cytometry. Inhibition of purified soluble guanylyl cyclase was quantified using an ELISA to measure cGMP production. RESULTS: Pre-incubation of platelets in abacavir significantly increased activation in response to ADP in a time and dose-dependent manner. The active anabolite of abacavir, carbovir triphosphate, competitively inhibited soluble guanylyl cyclase activity with a K(i) of 55 μmol/l. CONCLUSION: Abacavir competitively inhibits guanylyl cyclase, leading to platelet hyperreactivity. This may explain the observed increased risk of myocardial infarction in HIV patients taking abacavir.