Inhibition of KKO-induced platelet accretion and fibrin generation by PRT318. (A) Inhibition of Syk signaling by PRT318 in whole human blood for platelet accretion and fibrin generation compared with vehicle control. Relative inhibition is shown as a ratio of sample pre-incubated with the Syk-pathway inhibitor and the sample incubated with the vehicle control. KKO plus PF4 was added to each and samples were run in parallel. Mean ± 1 SEM is shown. N = 3 with each experiment performed in triplicate. Paired two-tailed Student t tests were used to evaluate the significance of differences between samples with PRT318 and those with vehicle control. (B) Same as in (A), but using monocyte-targeted Syk inhibition prior to repleting monocyte-depleted blood.