Inclisiran: present and future perspectives of a new effective LDL cholesterol-lowering agent

Effect of lipid-lowering therapy on platelet reactivity in patients treated with and without antiplatelet therapy

Circulating lipoproteins may interact with platelets, increasing platelet sensitivity to aggregating agonists and their tendency towards activation and thrombus formation. In particular, patients with hypercholesterolemia exhibit a higher degree of platelet reactivity compared to normolipidemic. Moreover, accruing evidence report that lipid-lowering therapies can reduce thrombus formation, particularly in the absence of concomitant antiplatelet therapy. However, the underlying biological mechanism(s) explaining these clinical observations are not completely understood. Baseline platelet reactivity and high on-treatment platelet reactivity while on antiplatelet therapy (e.g., aspirin and clopidogrel) are associated with poor clinical outcomes. Therefore, strategies to reduce baseline platelet reactivity or improve the pharmacodynamic profile of antiplatelet therapies are an unmet clinical need. The potential use of lipid-lowering therapies for optimizing platelet reactivity provides several advantages as there is strong evidence that reducing circulating lipoproteins can improve clinical outcomes, and they may avoid the need for potent antiplatelet therapies that, although more effective, are associated with increased bleeding risk. This review will provide a systematic overview of the effects of lipid-lowering therapy on platelet reactivity in patients treated with and without antiplatelet therapy. We will focus on the potential biological mechanism(s) of action and the effect of statins, ezetimibe, proprotein convertase subtilisin/kexin 9 inhibitors, omega-3 fatty acids, and recombinant high-density lipoprotein on platelet reactivity. Ultimately, we will assess the current gaps in the literature and future perspective in the field.

Cholesterol reduction by immunization with a PCSK9 mimic

Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a plasma protein that controls cholesterol homeostasis. Here, we design a human PCSK9 mimic, named HIT01, with no consecutive 9-residue stretch in common with any human protein as a potential heart attack vaccine. Murine immunizations with HIT01 reduce low-density lipoprotein (LDL) and cholesterol levels by 40% and 30%, respectively. Immunization of cynomolgus macaques with HIT01-K21Q-R218E, a cleavage-resistant variant, elicits high-titer PCSK9-directed antibody responses and significantly reduces serum levels of cholesterol 2 weeks after each immunization. However, HIT01-K21Q-R218E immunizations also increase serum PCSK9 levels by up to 5-fold, likely due to PCSK9-binding antibodies altering the half-life of PCSK9. While vaccination with a PCSK9 mimic can induce antibodies that block interactions of PCSK9 with the LDL receptor, PCSK9-binding antibodies appear to alter homeostatic levels of PCSK9, thereby confounding its vaccine impact. Our results nevertheless suggest a mechanism for increasing the half-life of soluble regulatory factors by vaccination.

Bempedoic acid: a new player for statin-intolerant patients and beyond

PURPOSE OF REVIEW

Low-density lipoproteins (LDL) cause atherosclerotic cardiovascular disease, a condition associated with significant morbidity and mortality. Statins represent the cornerstone for preventing cardiovascular events in patients with elevated LDL-cholesterol (LDL-C) levels, however, they are associated with frequent musculoskeletal adverse effects, which lead to drug discontinuation or limit their use to low (and less effective) doses. Bempedoic acid (BA) is a newly approved, safe, cholesterol-lowering agent that inhibits ATP-citrate lyase, an enzyme upstream to 3-hydroxy-3-methyl-glutaryl-CoA (HMG-CoA) reductase, the target of statins. Unlike statins, BA is not associated with musculoskeletal side effects, representing a promising drug for statin-intolerant patients. This review aims to summarize the current evidence on the efficacy, safety, and impact on clinical outcomes of BA, to review current indications for its use, and to highlight the ongoing clinical trials that will help deepen our knowledge of this promising compound.

RECENT FINDINGS

BA improves clinical outcomes in statin-intolerant patients. Multiple ongoing studies are evaluating whether BA can be employed in other clinical settings.

SUMMARY

BA safely and effectively reduces the levels of multiple atherogenic markers and can be employed to reach LDL-C targets independently from statin tolerance.

Hepatocyte-targeted siTAZ therapy lowers liver fibrosis in NASH diet-fed chimeric mice with hepatocyte-humanized livers

Nonalcoholic steatohepatitis (NASH) is emerging as the most common cause of liver disease. Although many studies in mouse NASH models have suggested therapies, translation to humans is poor, with no approved drugs for NASH. One explanation may lie in differences between mouse and human hepatocytes. We used NASH diet-fed chimeric mice reconstituted with human hepatocytes (hu-liver mice) to test a mechanism-based hepatocyte-targeted small interfering RNA (siRNA), GalNAc-siTaz, shown previously to block the progression to fibrotic NASH in mice. Following ablation of endogenous hepatocytes, male mice were reconstituted with human hepatocytes from a single donor with the rs738409-C/G PNPLA3 risk variant, resulting in ∼95% human hepatocyte reconstitution. The mice were then fed a high-fat choline-deficient l-amino acid-defined diet for 6 weeks to induce NASH, followed by six weekly injections of GalNAc-siTAZ to silence hepatocyte-TAZ or control GalNAc-siRNA (GalNAc-control) while still on the NASH diet. GalNAc-siTAZ lowered human hepatic TAZ and IHH, a TAZ target that promotes NASH fibrosis. Most important, GalNAc-siTAZ decreased liver inflammation, hepatocellular injury, hepatic fibrosis, and profibrogenic mediator expression versus GalNAc-control, indicating that GalNAc-siTAZ decreased the progression of NASH in mice reconstituted with human hepatocytes. In conclusion, silencing TAZ in human hepatocytes suppresses liver fibrosis in a hu-liver model of NASH.