Real‐world effectiveness of monoclonal antibody inhibitors of PCSK9 in patients with heterozygous familial hypercholesterolemia: A retrospective cohort study

Abstract Background Heterozygous familial hypercholesterolemia (HeFH) is a genetic condition that is associated with a high risk of atherosclerotic cardiovascular disease (ASCVD) due to elevated lipid levels. Proprotein convertase subtilisin/kexin type 9 (PCSK9) monoclonal antibody inhibitors have been shown to reduce low‐density lipoprotein cholesterol (LDL‐C) substantially. This study aimed to assess the real‐world effectiveness of PCSK9 inhibitor therapy among patients with HeFH. Methods Retrospective cohort study of patients with probable or definite HeFH on a PCSK9 inhibitor at a specialized lipid clinic between 2015 and 2022. The primary objective was the proportion of patients who attained a ≥50% reduction in LDL‐C after 12 months of treatment. Results In total, 141 patients were screened and 95 were included. Mean age was 63 years, 51% were female, and mean baseline LDL‐C level was 4.0 mmol/L (155 mg/dL). A majority of patients (60%) had statin intolerance, and 73% were on ezetimibe. The most common PCSK9 inhibitor was evolocumab (94%). Overall, 74% of patients achieved a ≥50% reduction in LDL‐C after 12 months of therapy. Mean LDL‐C concentration decreased to 1.7 mmol/L (66 mg/dL) (approximately 59% reduction from baseline) after 12 months of follow‐up but increased to 1.9 mmol/L (73 mg/dL) after ≥24 months of follow‐up. Similar trends were observed in non‐high‐density lipoprotein cholesterol and apolipoprotein B. Lipoprotein(a) was significantly reduced by 45% over 12 months. Twelve percent of patients permanently discontinued therapy. Barriers to PCSK9i use were mostly related to cost. Conclusions In a real‐world cohort of HeFH patients, most of which were intolerant to statins, a high majority were able to achieve a ≥50% reduction in LDL‐C after 12 months of PCSK9 inhibitor therapy (mean reduction of approximately 59%), which is similar to clinical trial data of patients with ASCVD. A significant reduction in non‐high‐density lipoprotein cholesterol, apolipoprotein B, and lipoprotein(a) were also observed.