CSL112 Infusion Rapidly Increases APOA1 Exchange Rate via Specific Serum Amyloid-Poor HDL Subpopulations When Administered to Patients Post-Myocardial Infarction

BACKGROUND: To characterize the effects of CSL112 (human APOA1 [apolipoprotein A1]) on the APOA1 exchange rate (AER) and the relationships with specific HDL (high-density lipoprotein) subpopulations when administered in the 90-day high-risk period post-acute myocardial infarction. METHODS: A subset of patients (n=50) from the AEGIS-I (ApoA-I Event Reducing in Ischemic Syndromes I) study received either placebo or CSL112 post-acute myocardial infarction. AER was measured in AEGIS-I plasma samples incubated with lipid-sensitive fluorescent APOA1 reporter. HDL particle size distribution was assessed by native gel electrophoresis followed by fluorescent imaging and detection of APOA1 and SAA (serum amyloid A) by immunoblotting. RESULTS: CSL112 infusion increased AER peaking at 2 hours and returning to baseline 24 hours post-infusion. AER correlated with cholesterol efflux capacity (r=0.49), HDL-cholesterol (r=0.30), APOA1 (r=0.48), and phospholipids (r=0.48; all P<0.001) over all time points. Mechanistically, changes in cholesterol efflux capacity and AER induced by CSL112 reflected HDL particle remodeling resulting in increased small HDL species that are highly active in mediating ABCA1 (ATP-binding cassette transporter 1)-dependent efflux, and large HDL species with high capacity for APOA1 exchange. The lipid-sensitive APOA1 reporter predominantly exchanged into SAA-poor HDL particles and weakly incorporated into SAAenriched HDL species. CONCLUSIONS: Infusion of CSL112 enhances metrics of HDL functionality in patients with acute myocardial infarction. This study demonstrates that in post-acute myocardial infarction patients, HDL-APOA1 exchange involves specific SAA-poor HDL populations. Our data suggest that progressive enrichment of HDL with SAA may generate dysfunctional particles with impaired HDL-APOA1 exchange capacity, and that infusion of CSL112 improves the functional status of HDL with respect to HDL-APOA1 exchange.