The Impact of Convertase Subtilisin/Kexin Type 9 Monoclonal Antibodies with and without Apheresis on Platelet Aggregation in Familial Hypercholesterolemia

Abstract

Background and aims: It is well known that elevated cholesterol is associated with enhanced platelet aggregation and patients suffering from familial hypercholesterolemia (FH) have a high risk of thrombotic cardiovascular events. Although decreasing cholesterol level is associated with attenuation of platelet hyperactivity, there are currently no data on the effect of convertase subtilisin/kexin type 9 monoclonal antibodies (PCSK9ab) on platelet reactivity in FH. The aim of the study was to analyse the impact of different therapies including PCSK9ab on platelet aggregation in FH.

Methods: This study enrolled all 15 patients treated in the University Hospital Hradec Králové for FH. PCSK9ab have been administered in 12 of 15 patients while 8 patients were also undergoing lipid apheresis. Blood samples from all patients including pre- and post-apheresis period were tested for platelet aggregation triggered by 7 inducers, and the effect of 3 clinically used drugs (acetylsalicylic acid, ticagrelor and vorapaxar) was compared as well.

Results: Although apheresis decreased the reactivity of platelets in general, platelet responses were not different between non-apheresis patients treated with PCSK9ab and apheresis patients (post-apheresis values) with the exception of ristocetin. However, when compared to age-matched healthy population, FH patients had significantly lower platelet aggregation responses to 4 out of 7 used inducers and higher profit from 2 out of 3 used antiplatelet drugs even after exclusion of FH patients regularly receiving conventional antiplatelet treatment.

Conclusion: This study showed for the first time the suitability of PCSK9ab treatment for reduction of platelet reactivity in FH patients.

Keywords: ADP receptor; Acetylsalicylic acid; Antiplatelet; Dyslipidemia; Ticagrelor; Vorapaxar.

Fig. 1

Included familial hypercholesterolemia (FH) patients, their treatment and subgroups. For reason of comparison between FH treatment modalities, patients were divided into 2 subgroups — (1) apheresis group (n = 6) and (2) pharmacotherapy group (n = 6). The remaining 3 FH patients were used solely together with other 12 patients from the above-mentioned two subgroups for comparison between FH and age-matched generally healthy controls

Fig. 2

Graphical scheme of the performed experiment. The first part (A) depicts both treatment types and blood collection: 1 — patients suffering from familial hypercholesterolemia (FH); 2 — the first group of patients treated with PCSK9ab and undergoing apheresis as well (apheresis group, n = 6), the samples were measured before apheresis — tube A and after apheresis — tube B; 3 — the second group of patients treated with PCSK9ab (pharmacotherapy group, n = 6) — tube C; 4 — all samples (including the rest of FH patients, total n = 15) were tested for biochemical parameters (glucose, serum lipids and creatinine). The second part (B) depicts experiment with platelet aggregation analyser: 1 — experiment was initiated precisely 30 min after the blood draw, whole blood with preheated saline was incubated with tested antagonist/inhibitor (ASA, vorapaxar, ticagrelor) or their solvent DMSO; 2 — 6 min monitoring after addition of inducers of platelet aggregation (collagen, ristocetin, TRAP, ADP, AA, PAF, U-46619). The administered hypolipidemic drugs are summarized in the Fig. 1 and Supplementary information (Supplementary information Table S4)

Fig. 3

Comparison of various inducers of platelet aggregation with or without antagonist in all PCSK9ab-treated patients with or without lipid apheresis. A Area under the curve (AUC) of aggregation induced by collagen at a final concentration of 1 µg/ml in PSCK9ab-treated patients, with apheresis (before and after) and without apheresis. B AUC of aggregation induced by ristocetin at a final concentration of 400 µM in PSCK9ab-treated patients, with apheresis (before and after) and without apheresis. C AUC of aggregation induced by TRAP at a final concentration of 10 µM in PSCK9ab-treated patients, with apheresis (before and after) and without apheresis. D AUC of aggregation induced by TRAP after 1 µM vorapaxar pre-treatment in PSCK9ab-treated patients, with apheresis (before and after) and without apheresis. P-values were calculated by a paired test (pre- and post-apheresis) or an unpaired test (apheresis samples vs. pharmacotherapy group). Results are shown as median with 95% confidence interval

Fig. 4

Comparison of various inducers of platelet aggregation in a group of generally healthy donors and all included familial hypercholesterolemic patients. A Area under the curve (AUC) of aggregation induced by AA at a final concentration of 200 μM. B AUC of aggregation induced by collagen at a final concentration of 1 µg/ml. C AUC of aggregation induced by ADP at a final concentration of 5 µM. D AUC of aggregation induced by ristocetin at a final concentration of 400 µM. E AUC of aggregation induced by U-46619 at a final concentration of 80 nM. P-values were calculated by an unpaired test. Results are shown as median with 95% confidence interval

Fig. 5

Effect of antiplatelet drugs on platelet aggregation in group of generally healthy donors and all included familial hypercholesterolemia patients. A AUC of aggregation induced by AA in blood pre-treated with 30 µM ASA. B AUC of aggregation induced by AA in blood pre-treated with 70 µM ASA. C AUC of aggregation induced by TRAP in blood pre-treated with 1 µM of vorapaxar. D AUC of aggregation induced by ADP in blood pre-treated with 0.5 µM of ticagrelor. P-values were calculated by an unpaired t-test. Results are shown as median with 95% confidence interval