Introduction

Two decades ago, basic scientists discovered that knocking out the genetic locus encoding for Angiopoietin-like 3 (ANGPTL3) led to abnormally low lipid levels in mice.¹ Later, exome-sequencing in humans linked loss-of-function ANGPTL3 mutations with hypolipidemia² and lower risk of coronary artery disease.³ Inhibition of ANGPTL3 activates both lipoprotein lipase and endothelial lipase and prevents hepatic secretion of triglyceride-rich lipoproteins, thereby reducing triglycerides and total cholesterol. With growing recognition of the residual risk posed by lipoproteins beyond LDL,⁴ ANGPTL3 offered a promising therapeutic target secondary to its multifaceted lipid regulation.

Subsequently, therapies targeting ANGPTL3 were developed by two mechanisms: 1) a monoclonal antibody neutralizing levels in the serum (evinacumab)⁵ and 2) an antisense oligonucleotide inhibiting production in hepatocytes (vupanorsen).^6-7

Here, we review recently published outcomes for evinacumab and vupanorsen, demonstrating their effects on LDL-C, triglycerides, and other lipoproteins. We conclude by outlining future questions for this emerging therapeutic class.

Monoclonal Antibody Approach: Evinacumab

Given its LDL receptor-independent reduction of LDL-C, evinacumab was first applied to patients with homozygous familial hypercholesterolemia (HoFH), characterized by absent or defective LDL receptors. In a phase 3, double-blind, placebo-controlled trial, 65 patients with HoFH receiving standard therapy (94% receiving statin; 77% PCSK9 inhibitor; 75% ezetimibe; 34% apheresis) were randomized to IV evinacumab every 4 weeks or placebo.⁸ With a primary outcome of percent change in LDL-C at 24 weeks, evinacumab therapy was associated with a 49% reduction in LDL-C (CI -65 to -33%; p<0.001) compared to placebo, with the absolute LDL-C difference between groups being 132 mg/dL.

Subsequently, evinacumab was studied outside the HoFH population, trialed in individuals with refractory hypercholesterolemia (defined as LDL-C ≥70 with atherosclerotic cardiovascular disease [ASCVD] and LDL-C ≥100 without) due to heterozygous FH (HeFH) or an unspecified cause already on advanced therapies.⁹ Beyond broadening the trial population, investigators assessed subcutaneous (SQ) delivery of evinacumab. In a phase 2, double-blind, placebo-controlled trial, 272 patients were randomized to SQ or IV arms of varying doses with a primary outcome of percent change in LDL-C from baseline. In the study, 70-80% of participants had HeFH and approximately 60% were receiving statin, 100% PCSK9 inhibitor, and approximately 30% ezetimibe.

After 16 weeks, both SQ and IV evinacumab were associated with LDL-C reductions compared to placebo in a dose-dependent manner (-56% with high-dose SQ [CI -74 to -38%] and -51% with high-dose IV [CI -68 to -33%]; p-values <0.001), with responses seen as early as 2 weeks. SQ and IV routes were not compared directly but achieved comparable LDL-C reductions. Secondary endpoints demonstrated significant reductions in apoB, non-HDL-C, triglycerides, and HDL-C.

Limitations for both trials included their small sample sizes, limited diversity (>70% white in HoFH trial and >90% in HeFH trial) and being underpowered to measure clinical outcomes. Moreover, both trials employed the Friedewald equation which can underestimate LDL-C when triglycerides are elevated,¹⁰ expected in many of the patients with advanced hyperlipidemia anticipated to receive these therapies, and particularly at lower post-treatment LDL-C levels.

Antisense Oligonucleotide Approach: Vupanorsen

Vupanorsen is a GalNAc-conjugated therapy targeting delivery of antisense oligonucleotides to hepatocytes to prevent upstream production of ANGPTL3. In a phase 2, double-blind, placebo-controlled trial, 105 patients with hypertriglyceridemia (>150 mg/dL), type 2 diabetes, and hepatic steatosis were randomized to varying regimens of subcutaneous vupanorsen or placebo, with a primary outcome of percent change in triglycerides from baseline.⁷ Notably, both the study populations (hypercholesterolemia vs. hypertriglyceridemia) and primary outcomes (LDL-C vs. triglyceride reduction) of the evinacumab and vupanorsen trials differed significantly.

After 6 months, vupanorsen therapy was associated with a 53% reduction in triglycerides (CI -43 to -60%; p-value <0.0001). Secondary endpoints demonstrated reductions in Apo-C III (58%), remnant cholesterol (38%), total cholesterol (19%), and HDL-C (24%) [all p < 0.0001], but interestingly no significant change in LDL-C. It is unclear to what extent the inability to replicate the LDL-C reduction seen with evinacumab was due to patient selection, drug delivery, or other factors. The authors hypothesized that trialing higher doses in the future might replicate the LDL-C reductions seen in those with inherent ANGPTL3 deficiencies.

Limitations of the study included its small sample size, limited diversity (> 92% white), and low prevalence of CAD (7% of patients). Moreover, the baseline use of statins was low at only 45% of patients and with only 4% on ezetimibe.

Future Considerations

As the recent evinacumab and vupanorsen trials were not powered for hard clinical outcomes, future research is needed to quantify effects on cardiovascular events in the high-risk populations expected to receive ANGPTL3 therapies. An improvement in outcomes is expected with evinacumab given the large LDL-C reductions seen, although a decrease in HDL-C is unique to ANGPTL3 therapies and should be further investigated to rule out detrimental effects on outcomes. Findings in those with inherently low ANGPTL3, and the broader HDL-C literature, would however suggest otherwise.⁵ Additional clinical trials for antisense oligonucleotide therapy is particularly needed, since vupanorsen did not demonstrate LDL-C reductions seen with evinacumab.

As clinical outcomes are further defined, the next question will be how to integrate ANGPTL3 therapies into the current armamentarium of lipid lowering agents. With the expanding landscape of monoclonal antibody and mRNA therapies, it will be increasingly necessary to define which patients should receive which drugs and when.

Additionally, as opposed to using evinacumab as only add-on therapy to PCSK9 inhibitors, future trials might compare these agents head-to-head to define the sequence in which these advanced therapies should be used, particularly with respect to cost-effectiveness.

Moreover, cost-effectiveness might change if use of first and second-line therapies improve; in the evinacumab and vupanorsen trials, only 50-60% of patients were receiving statins, and 30% or less receiving ezetimibe. Recent findings from the SAMSON trial highlight the degree of symptom burden from statins driven by the nocebo effect and might help to reframe conversations between clinicians and patients about initiating or intensifying statin therapy.¹¹

Conclusion

ANGPTL3 therapies have the potential to reinforce the current arsenal of lipid lowering agents, particularly for high-risk populations with refractory hyperlipidemia despite advanced treatments. Future research is needed on hard ASCVD outcomes and long-term safety. Further investigation will define which patients are ideal candidates for these therapies and how best to incorporate them amid the growing landscape of both biologic and non-biologic agents.  

References

1. Koishi R, Ando Y, Ono M, et al. Angptl3 regulates lipid metabolism in mice. Nat Genet 2002;30:151-7.
2. Musunuru K, Pirruccello JP, Do R, et al. Exome sequencing, ANGPTL3 mutations, and familial combined hypolipidemia. N Engl J Med 2010;363:2220-7.
3. Stitziel NO, Khera AV, Wang X, et al. ANGPTL3 deficiency and protection against coronary artery disease. J Am Coll Cardiol 2017;69:2054–63.
4. Boekholdt SM, Arsenault BJ, Mora S, et al. Association of LDL cholesterol, non-HDL cholesterol, and apolipoprotein B levels with risk of cardiovascular events among patients treated with statins: a meta-analysis. JAMA 2012;307:1302-09.
5. Dewey FE, Gusarova V, Dunbar RL, et al. Genetic and pharmacologic inactivation of ANGPTL3 and cardiovascular disease. N Engl J Med 2017;377:211-21.
6. Graham MJ, Lee RG, Brandt TA, et al. Cardiovascular and metabolic effects of ANGPTL3 antisense oligonucleotides. N Engl J Med 2017;377:222-32.
7. Gaudet D, Karwatowska-Prokopczuk E, Baum SJ, et al. Vupanorsen, an N-acetyl galactosamine-conjugated antisense drug to ANGPTL3 mRNA, lowers triglycerides and atherogenic lipoproteins in patients with diabetes, hepatic steatosis, and hypertriglyceridaemia. Eur Heart J 2020;41:3936–45.
8. Raal FJ, Rosenson RS, Reeskamp LF, et al. Evinacumab for homozygous familial hypercholesterolemia. N Engl J Med 2020;383:711-20.
9. Rosenson, RS, Burgess LJ, Ebenbichler CF, et al. Evinacumab in patients with refractory hypercholesterolemia. N Engl J Med 2020;383:2307-19.
10. Martin SS, Blaha MJ, Elshazly MB, et al. Friedewald-estimated versus directly measured low-density lipoprotein cholesterol and treatment implications. J Am Coll Cardiol 2013;62:732-9.
11. Wood, FA, Howard JP, Finegold JA, et al. N-of-1 trial of a statin, placebo, or no treatment to assess side effects. N Engl J Med 2020;383:2182-84.

Clinical Topics: Diabetes and Cardiometabolic Disease, Dyslipidemia, Prevention, Atherosclerotic Disease (CAD/PAD), Homozygous Familial Hypercholesterolemia, Hypertriglyceridemia, Lipid Metabolism, Nonstatins, Novel Agents, Primary Hyperlipidemia, Statins

Keywords: Dyslipidemias, Primary Prevention, Hydroxymethylglutaryl-CoA Reductase Inhibitors, Apolipoprotein C-III, Hyperlipoproteinemia Type II, Mice, Lipoprotein Lipase, Hyperlipidemias, Cholesterol, LDL, Apolipoproteins B, PCSK9 protein, human, Proprotein Convertase 9, Pharmaceutical Preparations, Hypercholesterolemia, Oligonucleotides, Antisense, Double-Blind Method, Patient Selection, RNA, Messenger, Diabetes Mellitus, Type 2, Cost-Benefit Analysis, Nocebo Effect, Prevalence, Coronary Artery Disease, Cardiovascular Diseases, Exome, Antibodies, Monoclonal, Triglycerides, Lipoproteins, Hypertriglyceridemia, Receptors, LDL, Blood Component Removal, Lipase, Hepatocytes, Mutation, Genetic Loci, Bodily Secretions, Biological Products, Reference Standards

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