The Pharmacologic Role and Clinical Utility of PCSK9 Inhibitors for the Treatment of Hypercholesterolemia

In addition to monoclonal antibodies against proprotein convertase subtilisin-kexin type 9 (PCSK9), vaccines against PCSK9 and smaller molecule inhibitors as well as RNA inhibitors of PCSK9 production have been created. The monoclonal antibodies against PCSK9 and the PCSK9 RNA inhibitors can reduce low-density lipoproteins (LDLs) by over 50%, non-high-density lipoprotein (HDL) cholesterol and triglycerides, and increasing HDL. Although effective in several homozygous familial hypercholesterolemia patient types, PCSK9 inhibitors does not work in all patient types. Outcome trials show no effects on mortality but do show reductions in atherosclerotic events such as myocardial infarctions, strokes, and need for coronary revascularization. PCSK9 inhibitors have a very attractive safety profile with no significant elevations in measures of muscle or liver damage. The current and more advanced experimental agents all require subcutaneous dosing, and injection site reactions are among the most common adverse events. Therapy for the Food and Drug Administration (FDA) approved agents is markedly expensive, and this is the primary barrier to utilization. However, it is possible to identify patients with a number needed to treat to prevent an atherosclerotic event low enough to render it cost-effective and one such factor is whether or not you require a 50% reduction in LDL in order to achieve your LDL goal.

Compound heterozygous LDLR variant in severely affected familial hypercholesterolemia patient.

Familial hypercholesterolemia (FH) is most commonly caused by mutations in the LDL receptor (LDLR), which is responsible for hepatic clearance of LDL from the blood circulation. We described a severely affected FH proband and their first-degree blood relatives; the proband was resistant to statin therapy and was managed on an LDL apheresis program. In order to find the causative genetic variant in this family, direct exon sequencing of the LDLR, APOB and PCSK9 genes was performed. We identified a compound heterozygous mutation in the proband with missense p.(W577C) and frameshift p.(G676Afs33) variants at exons 12 and 14 of the LDLR gene respectively. DNA sequencing of LDLR gene from the parents demonstrated that the missense variant was inherited from the mother and frameshift variant was inherited from the father. The frameshift variant resulted in a stop signal 33 codons downstream of the deletion, which most likely led to a truncated protein that lacks important functional domains, including the trans-membrane domain and the cytoplasmic tail domain. The missense variant is also predicted to be likely pathogenic and affect EGF-precursor homology domain of the LDLR protein. The segregation pattern of the variants was consistent with the lipid profile, suggesting a more severe FH phenotype when the variants are in the compound heterozygous state. The finding of a compound heterozygous mutation causing severe FH phenotype is important for the genotype-phenotype correlation and also enlarges the spectrum of FH-causative LDLR variants in the Arab population, including the Saudi population.