A Gene Expression Signature Reflective of Exposure to Antiplatelet Therapy is Associated with Bleeding

Introduction: Biosignatures composed of gene expression data hold promise for personalized antiplatelet therapy in conjunction with current guidelines and risk scores. The Aspirin Response Signature (ARS) of blood RNA transcripts is associated with lower platelet function after exposure to aspirin 325mg and increased risk of major adverse cardiovascular events (MACE). We studied a challenge cohort to determine if exposure to aspirin 81mg and ticagrelor changes ARS scores and a clinical cohort to determine whether ARS scores are associated with incident bleeding. Methods: Samples of whole blood and platelet-rich plasma (PRP) were collected from volunteers enrolled in a challenge study (N=188) who were sequentially exposed to 4 weeks of daily aspirin 81mg, then 325mg, then ticagrelor 90mg twice daily. ARS scores were calculated from whole blood RNA qPCR; platelet function and protein expression were assessed in PRP. ARS scores were also calculated in patients undergoing cardiac catheterization (N=1421). Results: In mixed models assessing the effect of antiplatelet drug exposure, exposure to aspirin 81mg was not associated with changes in ARS component gene expression or ARS score. Exposure to aspirin 325 mg resulted in an increase of 6.0% in aggregate ARS component gene expression (p<3x10 -4 vs baseline and vs aspirin 81mg) and an increase in expression of platelet proteins corresponding to ARS genes. Exposure to ticagrelor resulted in an increase of 30.7% in ARS component gene expression (p<1x10 -10 vs baseline and each aspirin dose) and ARS score (p<6x10 -4 vs baseline and each aspirin dose). In the catheterization cohort, 25.4% of patients experienced bleeding events over a median 6.2 years of follow up. In a Cox model adjusting for demographics and baseline antithrombotic medication use, patients with ARS scores above the median had a higher risk of incident bleeding (HR 1.26 [95% CI 1.01-1.56], p = 0.038). Conclusions: The ARS gene expression score increased in response to exposure to antiplatelet agents with different mechanisms of action in a dose- and potency-dependent fashion and was associated with increased bleeding risk. ARS scores could inform future strategies to individualize antiplatelet therapy to balance prevention of bleeding and MACE.