Abstract Body (Do not enter title and authors here): Background: Lipoprotein(a) [Lp(a)] and other atherogenic lipoproteins each contain one molecule of apolipoprotein B (apoB) per particle. Recent studies have suggested that on a per particle basis, Lp(a) is more strongly associated with major adverse cardiovascular events (MACE) than low density lipoprotein.
Hypothesis: In statin-treated patients with recent acute coronary syndrome (ACS), we tested the hypothesis that, on a per particle basis, Lp(a) and its change on treatment with alirocumab (ALI) are more strongly associated with MACE than other [non-Lp(a)] apoB-containing particles.
Methods: Molar apolipoprotein(a) [corresponding to Lp(a)] and apo B were measured by mass spectrometry at baseline and month 4 (M4) in a subgroup of 11,957 patients who provided consent for use of stored samples in the ODYSSEY OUTCOMES trial. Non-Lp(a) apoB in nmol/L was calculated as total apo B – Lp(a). Lp(a) and non-Lp(a) apo B at baseline in the placebo group, and absolute changes in their levels on ALI, were related to risk of MACE using proportional hazards models. The latter analysis was adjusted for baseline Lp(a) and non-Lp(a) apo B and stratified by baseline Lp(a) (<125 nmol/L and ≥125 nmol/L).
Results: Baseline levels of Lp(a) and non-Lp(a) apoB are shown in the Table. In the placebo group, both baseline Lp(a) and non-Lp(a) apo B independently predicted MACE. At M4 in the ALI group, median Lp(a) change from baseline was -40.9 and -7.0 in those with baseline levels ≥ or <125 nmol/L, respectively. Corresponding median changes in non-Lp(a) apoB were -739 and -776 nmol/L (all P<0.001). In the ALI group with baseline Lp(a)>125 nmol/L, the decrease from baseline in Lp(a), but not the decrease in non-Lp(a) apo B, was significantly related to risk of MACE. Among those with baseline Lp(a)≤125 nmol/L, the decrease from baseline in non-Lp(a) apo B, but not in Lp(a), with ALI was significantly related to risk of MACE.
Conclusions: On a per particle basis, baseline Lp(a) and non-Lp(a) apo B both predicted MACE. Among those with high baseline Lp(a), reduction in MACE with ALI was predominantly associated with reduction of Lp(a); among those with lower baseline Lp(a) reduction in MACE with ALI was predominantly associated with reduction in non-Lp(a) apo-B. Lp(a) may be an important target of treatment with ALI in those with elevated levels after ACS.