Beyond LDL-cholesterol: effects of alirocumab on the human apolipoproteome

Abstract Introduction The PACMAN-AMI (Effects of the PCSK9 Antibody Alirocumab on Coronary Atherosclerosis in Patients With Acute Myocardial Infarction) trial enrolled 300 participants with longitudinal plasma samples available at four time points (enrollment, 24 hours, 4 weeks, 52 weeks), of which 266 completed the 52-week follow-up. Purpose Expanding on a previous investigation employing apolipoprotein proteomics in patients with coronary heart disease, the current study aimed to evaluate the impact of the monoclonal antibody alirocumab on apolipoprotein and proprotein convertase subtilisin/kexin type 9 (PCSK9) levels. Methods A mass spectrometry assay was employed to quantify 15 apolipoproteins. Linear mixed-effects models assessed the impact of timepoints and treatments (alirocumab: n = 131, placebo: n = 135, in addition to statins) on apolipoprotein levels. Results Alirocumab led to a fast rise in PCSK9 levels, with a marked increase [inter-quartile range] of 262% [207%] as early as 24 hours after treatment initiation, followed by more pronounced elevations at 4 weeks and 52 weeks, reaching 1575% [813%] and 1480% [747%], respectively (P < 0.001 for all comparisons). At 52 weeks, the ApoB reduction compared with enrollment was -75% [10%] with alirocumab vs. -43% [19%] with placebo (P < 0.001, between groups), while the change in LDL-C was -88% [9%] with alirocumab vs. -54% [19%] with placebo (P < 0.001). Alongside significantly greater reductions in ApoC2 (P = 0.0041) and ApoC3 (P < 0.001) with alirocumab, ApoE changed by -41.6% [21.1%] with alirocumab compared to -15.4% [24.5%] with placebo (P < 0.001). Overall, there was no impact on Apo(a) levels compared to baseline. Conclusion The rapid increase in PCSK9 levels after 24 hours suggests immediate immunocomplex formation. A compensatory rise in PCSK9 production may contribute to later elevations. Alirocumab not only lowered LDL-C but also achieved a sustained reduction in very low-density lipoprotein-associated apolipoproteins (ApoC2, ApoC3, and ApoE), indicating additional benefits of PCSK9 inhibitors.