Abstract Body (Do not enter title and authors here): Introduction: Cardiovascular events occur in patients without obstructive coronary artery disease (oCAD), indicating a need for better risk stratification tools. CT angiography (CTA)-based high-risk plaque (HRP) characteristics predict such events effectively but are not widely available. We performed comprehensive proteomics profiling in the PROMISE trial to identify biomarkers associated with HRP, oCAD, and major adverse cardiovascular events (MACE).

Methods: The PROMISE trial randomized patients with stable chest pain to CTA vs. stress testing. Proteomic profiling (Olink, 524 proteins) was performed on 1724 participants with CTA and biospecimens. A high-risk composite phenotype (HRCP) was defined as presence of oCAD (≥50% stenosis in any major vessel), Leaman score >5, coronary artery calcium score ≥400, or HRP features on CTA. Individual proteins were tested for association with HRCP (false discovery rate-adjusted p-value [q] <5%), followed by pathway analyses, association testing with MACE, and Mendelian randomization. K-means phenoclustering was used to identify clinical clusters. Proteins were then tested for association with the clusters.

Results: Thirty-seven proteins were significantly associated with HRCP in models adjusted for clinical covariables. These included GDF-15 (OR [95% CI]=1.4 [1.1-1.7], p=0.01), ACE2 (OR=1.4 [1.1-1.7], p=0.002), and LPL (OR=0.7 [0.6-0.9], p=0.01); proteins represented biologic pathways of metabolic regulation, inflammation, and protein degradation. Phenoclustering identified three patient subgroups with varying cardiovascular risk factors; levels of 32/37 proteins varied across the clusters. Seven of the 37 proteins were associated with MACE, including LPL (HR=0.5 [0.4-0.8], q=0.003), CTSD (HR=1.9 [1.2-2.9], q=0.009), GDF-15 (HR=1.7 [1.1-2.5], q=0.01), and ACE2 (HR=1.8 [1.3-2.6], q=0.002) with a direction of effect consistent with odds of HRCP. Mendelian randomization analyses suggest a causal role only for CTSD (cathepsin D) in CAD.

Conclusion: This study identified novel biomarkers associated with high-risk CAD phenotypes and adverse outcomes in the PROMISE trial, most of which also differentiated clinical phenoclusters, suggesting they report on molecular heterogeneity underlying clinical differences in patients at risk for CAD. These findings highlight potential biomarkers with clinical utility for improved risk stratification and elucidate one potential therapeutic target (CTSD) in the causal pathway of CAD events.