Comparing PCSK9 Inhibitor Prescription Rates Within High-Risk Populations: Diabetes Mellitus, Multi-Territory Vascular Disease, Multivessel and Recurrent Coronary Artery Disease

Proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors are subsidised in Australia for treatment of hypercholesterolemia in particularly high-risk patients with atherosclerotic cardiovascular disease (ASCVD). These high-risk groups are defined as: diabetes mellitus (with age≥60, Aboriginal or Torres Strait Islander origin or microalbuminuria), recurrent ASCVD (≥2 events within 5 years), multivessel coronary disease (≥50% stenosis in ≥2 large vessels) and multi-territory vascular disease (concurrent cerebrovascular or peripheral vascular disease). A retrospective observational analysis was conducted on high-risk patients with LDL>2.6 admitted to a quaternary hospital with ASCVD between 2020-2022. Australian Pharmaceutical Benefits Scheme (PBS) criteria was applied to assess and compare PCSK9 inhibitor eligibility and prescription rates within high-risk populations. In total, 477 ASCVD patients with LDL>2.6 were included. This was further categorised into: multivessel coronary disease (n=239, 50.1%), diabetes mellitus (n=60, 12.6%), recurrent ASCVD (n=55, 11.5%) and multi-territory vascular disease (n=32, 6.7%), p<0.001. When 2020 PBS criteria was applied, the number of eligible patients were 16/239 (6.7%), 5/60 (8.3%), 13/55 (23.6%) and 4/32 (12.5%) respectively, p=0.002. Of PBS eligible patients, the number prescribed PCSK9 inhibitors were: 7/16 (43.8%) for multi-vessel coronary disease, 1/5 (20%) for diabetes mellitus, 4/13 (30.8%) for recurrent ASCVD and 1/4 (25%) for multi-territory vascular disease patients (p=0.73). Despite a significantly higher prevalence of multivessel coronary disease and a higher proportion of eligible patients with recurrent ASCVD, prescribing rates for PCSK9 inhibitor therapy remain low amongst all high-risk groups including diabetes mellitus, multi-territory vascular disease, multivessel and recurrent ASCVD.