PCSK9 Inhibitor Treatment and Outcomes in Patients with Atherosclerotic Cardiovascular Disease but Without Prior Ischaemic Events: an Observational Study

Background and Aims Low-density lipoprotein cholesterol (LDL-C)-lowering therapies are proven effective in atherosclerotic cardiovascular disease (ASCVD), but real-world evidence for proprotein convertase subtilisin/kexin type 9 inhibitor (PCSK9i) monoclonal antibodies (mAb) remains limited. This study evaluated their impact in patients with ASCVD without prior ischaemic events. Methods Patients initiating PCSK9i mAb from January 2016 to December 2022 were identified in the Optum Research Database. A 1:2 propensity score-matched comparator cohort of PCSK9i non-initiators was developed. The primary endpoint was a composite of non-fatal myocardial infarction, non-fatal ischaemic stroke, or all-cause mortality. Key outcomes from the parametric G-formula were 5-year event rates, relative risk reduction (RRR) and absolute risk reduction (ARR), with intention-to-treat (ITT) analysis. Additional outcomes for PCSK9i mAb initiators included absolute and percent LDL-C reduction from baseline. Results Overall, 19 670 patients met selection criteria (6545 PCSK9i mAb initiators; 13 125 non-initiators). Baseline characteristics were well-balanced. Under ITT, estimated 5-year event rates were 17.5% [95% confidence interval (CI) 15.5%, 19.5%] with PCSK9i mAb vs 25.4% (95% CI 23.6%, 27.1%) without PCSK9i, yielding a RRR of 30.9% and ARR of 7.8%. Individual endpoints showed RRRs of 28.3% for myocardial infarction (P < .0001), 26.4% for ischaemic stroke (P = .02), and 28.5% for all-cause mortality (P < .0001). Among initiators, mean baseline and follow-up LDL-C were 117.8 and 54.7 mg/dL (on-treatment analysis), respectively, representing an absolute reduction of 63.1 mg/dL and percent reduction of 53.6%. Conclusions In ASCVD patients without prior events in clinical practice, PCSK9i mAb treatment was associated with lower ischaemic event and mortality rates.