Elsevier

The Lancet

Volume 383, Issue 9911, 4–10 January 2014, Pages 60-68
The Lancet

Articles
Effect of an RNA interference drug on the synthesis of proprotein convertase subtilisin/kexin type 9 (PCSK9) and the concentration of serum LDL cholesterol in healthy volunteers: a randomised, single-blind, placebo-controlled, phase 1 trial

https://doi.org/10.1016/S0140-6736(13)61914-5Get rights and content

Summary

Background

Proprotein convertase subtilisin/kexin type 9 (PCSK9) binds to LDL receptors, leading to their degradation. Genetics studies have shown that loss-of-function mutations in PCSK9 result in reduced plasma LDL cholesterol and decreased risk of coronary heart disease. We aimed to investigate the safety and efficacy of ALN-PCS, a small interfering RNA that inhibits PCSK9 synthesis, in healthy volunteers with raised cholesterol who were not on lipid-lowering treatment.

Methods

We did a randomised, single-blind, placebo-controlled, phase 1 dose-escalation study in healthy adult volunteers with serum LDL cholesterol of 3·00 mmol/L or higher. Participants were randomly assigned in a 3:1 ratio by computer algorithm to receive one dose of intravenous ALN-PCS (with doses ranging from 0·015 to 0·400 mg/kg) or placebo. The primary endpoint was safety and tolerability of ALN-PCS. Secondary endpoints were the pharmacokinetic characteristics of ALN-PCS and its pharmacodynamic effects on PCSK9 and LDL cholesterol. Study participants were masked to treatment assignment. Analysis was per protocol and we used ANCOVA to analyse pharmacodynamic endpoint data. This trial is registered with ClinicalTrials.gov, number NCT01437059.

Findings

Of 32 participants, 24 were randomly allocated to receive a single dose of ALN-PCS (0·015 mg/kg [n=3], 0·045 mg/kg [n=3], 0·090 mg/kg [n=3], 0·150 mg/kg [n=3], 0·250 mg/kg [n=6], or 0·400 mg/kg [n=6]) and eight to placebo. The proportions of patients affected by treatment-emergent adverse events were similar in the ALN-PCS and placebo groups (19 [79%] vs seven [88%]). ALN-PCS was rapidly distributed, with peak concentration and area under the curve (0 to last measurement) increasing in a roughly dose-proportional way across the dose range tested. In the group given 0·400 mg/kg of ALN-PCS, treatment resulted in a mean 70% reduction in circulating PCSK9 plasma protein (p<0·0001) and a mean 40% reduction in LDL cholesterol from baseline relative to placebo (p<0·0001).

Interpretation

Our results suggest that inhibition of PCSK9 synthesis by RNA interference (RNAi) provides a potentially safe mechanism to reduce LDL cholesterol concentration in healthy individuals with raised cholesterol. These results support the further assessment of ALN-PCS in patients with hypercholesterolaemia, including those being treated with statins. This study is the first to show an RNAi drug being used to affect a clinically validated endpoint (ie, LDL cholesterol) in human beings.

Funding

Alnylam Pharmaceuticals.

Introduction

LDL cholesterol is one of the major risk factors for coronary heart disease, with a continuous and graded association between its plasma concentration and risk—for every 0·78 mmol/L (30 mg/dL) change in LDL cholesterol, the relative risk for coronary heart disease changes by roughly 30%.1, 2 Additionally, in a large meta-analysis3 of 21 statin studies, the investigators concluded that for every 1·01 mmol/L (39 mg/dL) reduction in LDL cholesterol with statin treatment, cardiovascular events were reduced by about 22%.3 Despite the extensive use of statins, existing treatments for the management of raised LDL cholesterol remain inadequate. This is especially true for individuals with pre-existing coronary heart disease or diabetes, who are at the highest risk and require the most aggressive management of hypercholesterolaemia.4 Among high-risk individuals, it is estimated that only 50% achieve the target LDL cholesterol of less than 2·59 mmol/L at 6 months after statin treatment, despite close monitoring and optimisation of the drug regimen.5, 6, 7, 8, 9 With the LDL cholesterol target of less than 1·81 mmol/L in high-risk individuals, the number who reach their LDL cholesterol goals is even lower at 30%.9, 10 Thus, a clear unmet medical need exists for hypercholesterolaemia treatments, especially in high-risk patient populations.

Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a member of the serine protease family and was first connected to cholesterol metabolism when gain-of-function mutations in PCSK9 were identified in people with familial hypercholesterolaemia who did not have mutations in the LDL receptor (LDLR) or apolipoprotein B (APOB) genes.11 Animal studies subsequently determined that PCSK9 binds hepatocyte LDLRs both intracellularly and extracellularly, leading to their lysosomal degradation (figure 1).12, 13 Loss-of-function mutations in PCSK9 have also been described in human beings, and are associated with reductions in LDL cholesterol and risk of coronary heart disease.14, 15 Several individuals with no circulating PCSK9 due to compound heterozygous loss-of-function mutations have also been identified. These individuals have very low LDL cholesterol (<0·52 mmol/L), but are otherwise healthy.16, 17 In loss-of-function mouse models for PCSK9, reductions in total cholesterol have been noted,18 consistent with the human phenotype. Collectively, these genetics studies support the hypothesis that lowering of circulating plasma PCSK9 by inhibiting its synthesis in hepatocytes should lower LDL cholesterol, potentially resulting in reduced risk of coronary heart disease. Additionally, some evidence suggests that statin treatment increases circulating plasma PCSK9, which could limit the effectiveness of statins as the dose is increased.19, 20, 21, 22 Human clinical trials with PCSK9-blocking antibodies have shown significant reductions in LDL cholesterol in healthy volunteers23, 24 and in individuals with hypercholesterolaemia, with and without statins.25, 26, 27, 28, 29, 30

Small interfering RNA (siRNA) can direct sequence-specific degradation of messenger RNA, leading to suppression of synthesis of the corresponding proteins, as part of the natural biological process known as RNA interference (RNAi).31, 32 Our group has previously reported the acute, hepatocyte-specific lowering of synthesis and plasma concentrations of PCSK9 by treatment with a PCSK9-specific siRNA formulated in a lipid nanoparticle in several preclinical models.33 This treatment resulted in substantial and durable lowering of LDL cholesterol, without an effect on HDL cholesterol. Additionally, we confirmed in these models that the reduction in PCSK9 was based on an RNAi mechanism and resulted in increased numbers of LDLRs on hepatocyte membranes.33 We aimed to investigate the safety and efficacy in human beings of ALN-PCS, an siRNA that inhibits PCSK9 synthesis formulated in a novel lipid nanoparticle for delivery.34

Section snippets

Study design and participants

We undertook a randomised, single-blind, placebo-controlled, phase 1 clinical trial at two phase 1 units in the UK (Covance Clinical Research Unit, Leeds, and Quintiles Drug Research Unit at Guy's Hospital, London). Eligible participants were healthy adults aged 18–65 years with an LDL cholesterol higher than 3·00 mmol/L. Inclusion criteria required that they had received no lipid-lowering treatments in the 30 days before screening and that they had fasting triglyceride concentrations of 2·8

Results

32 eligible participants were recruited between Sept 21, 2011, and Sept 11, 2012. 24 were randomly assigned to receive ALN-PCS and eight to receive placebo (figure 2). One participant was excluded after random assignment because their lipid concentrations proximal to dosing were outside of those defined by the inclusion criteria. Table 1 lists the baseline characteristics of all participants who received study treatment and therefore were included in the analyses.

Overall, ALN-PCS was safe and

Discussion

ALN-PCS was well tolerated, with similar proportions of mild to moderate treatment-emergent adverse events occurring in the treatment and placebo groups. Although some participants developed a rash, it was mild, resolved spontaneously, and occurred with equal frequency in the in placebo and ALN-PCS-treated participants. The rash was identical in appearance and nature in both groups, and was probably a result of the premedications given to all participants, which can cause skin flushing (due to

References (39)

  • Z Zhao et al.

    Molecular characterization of loss-of-function mutations in PCSK9 and identification of a compound heterozygote

    Am J Hum Genet

    (2006)
  • AJ Hooper et al.

    The C679X mutation in PCSK9 is present and lowers blood cholesterol in a Southern African population

    Atherosclerosis

    (2007)
  • HE Careskey et al.

    Atorvastatin increases human serum levels of proprotein convertase subtilisin/kexin type 9

    J Lipid Res

    (2008)
  • P Costet et al.

    Plasma PCSK9 is increased by fenofibrate and atorvastatin in a non-additive fashion in diabetic patients

    Atherosclerosis

    (2010)
  • G Welder et al.

    High-dose atorvastatin causes a rapid sustained increase in human serum PCSK9 and disrupts its correlation with LDL cholesterol

    J Lipid Res

    (2010)
  • CS Dias et al.

    Effects of AMG 145 on low-density lipoprotein cholesterol levels: results from 2 randomized, double-blind, placebo-controlled, ascending-dose phase 1 studies in healthy volunteers and hypercholesterolemic subjects on statins

    J Am Coll Cardiol

    (2012)
  • SA Barros et al.

    Safety profile of RNAi nanomedicines

    Adv Drug Deliv Rev

    (2012)
  • Efficacy and safety of cholesterol-lowering treatment: prospective meta-analysis of data from 90 056 participants in 14 randomised trials of statins

    Lancet

    (2005)
  • Efficacy of cholesterol-lowering therapy in 18 686 people with diabetes in 14 randomised trials of statins: a meta-analysis

    Lancet

    (2008)
  • Cited by (481)

    • The evolving landscape of PCSK9 inhibition in cancer

      2023, European Journal of Pharmacology
    View all citing articles on Scopus
    View full text