Lyophilized Human Platelets Restore Hemostasis in the Presence of the P2Y12 Inhibitors Cangrelor, Ticagrelor and Clopidogrel

• Background: P2Y12 inhibitors block platelet ADP receptors thereby reducing clotting capacity. In an emergency, these agents must be reversed or therapeutically overcome to stop bleeding. Additionally, prior to and during elective procedures these inhibitors must be withdrawn, thereby increasing thrombotic risk. Lyophilized human platelets (Thrombosomes®) are stabilized platelet derived hemostatic agents currently under Phase 2 clinical development for thrombocytopenia and have potential as antiplatelet reversal agents.

• Aims: The aim of this study was to determine if lyophilized human platelets are resistant to the antiplatelet effect of P2Y12 inhibitors and therefore restore hemostasis in the presence of P2Y12 inhibitors.

• Methods: Fresh drawn platelet rich plasma (PRP) was treated with pharmacological concentrations of P2Y12 inhibitors cangrelor or ticagrelor and confirmed to inhibit ADP-stimulated aggregation on the PAP-8E Platelet Aggregometer. Changes in hemostatic properties of the P2Y12 inhibitor treated PRP were also tested under shear force on the Total Thrombus formation Analysis System (T-TAS®). P2Y12 inhibitor treated PRP samples were dosed with lyophilized platelets and tested for return of hemostatic properties by T-TAS. NOD SCID mice were used in a tail snip model to determine hemostatic efficacy of Thrombosomes® after super pharmacological doses of clopidogrel treatment.

• Results: Fresh PRP derived platelet aggregation response to ADP was inhibited by cangrelor or ticagrelor whereas lyophilized platelets did not respond to either inhibitor. Normal thrombus formation of PRP as measured by T-TAS occurred at 19.5± 1.5 minutes (n=4) but increases to 28.0±3.0 minutes with cangrelor (n=4) or 28.0±3.0 minutes with ticagrelor (n=5) treatment. The addition of 150k/µL lyophilized platelets to P2Y12-inhibited PRP reduced time to thrombus formation to lower than PRP alone; 15.5 ±0.5 minutes in the presence of cangrelor (n=3) versus 17.5 ±1.5 minutes in the presence of ticagrelor (n=5). In the in vivo tail snip mouse model animals treated with super pharmacological dose of clopidogrel bled for 18.0±10.0 minutes (n=5) unlike those not treated that only bleed for 9.5±2.5 minutes (n=6). Lyophilized platelet treated clopidogrel animals stopped bleeding at 12.5 ±4.5 minutes (n=5) after tail snip.

• Conclusion: Lyophilized human platelets, unlike normal platelets were resistant to the antiplatelet effects of P2Y12 inhibitors. In vitro and in vivo studies reveal that lyophilized human platelets can be used to recover the anti-thrombotic effect of P2Y12 antagonists, potentially allowing continued drug compliance prior to elective procedures and as a possible treatment for emergent acute bleeding while on P2Y12 antagonist therapy.