CD40LG and systemic lupus erythematosus: For example, a proof-of-concept study using the P2Y12 inhibitor clopidogrel for 12 weeks in patients with SLE reveals that the mean platelet volume, P-selectin-positive platelets, and the number of activated CD40L+ platelets all significantly decrease after starting clopidogrel treatment, yet these changes did not persist over time [168].