Author + information
- Received May 22, 2012
- Revision received August 8, 2012
- Accepted August 30, 2012
- Published online November 6, 2012.
- Clapton S. Dias, PhD⁎,⁎ (, )
- Adam J. Shaywitz, MD, PhD⁎,
- Scott M. Wasserman, MD†,
- Brian P. Smith, PhD‡,
- Bing Gao, PhD‡,
- Dina S. Stolman, MD, MSPH§,
- Caroline P. Crispino, MS§,
- Karen V. Smirnakis, MD, MPH, PhD§,
- Maurice G. Emery, PhD∥,
- Alexander Colbert, BA∥,
- John P. Gibbs, PhD∥,
- Marc W. Retter, PhD∥,
- Blaire P. Cooke, PharmD⁎,
- Stephen T. Uy, MS⁎,
- Mark Matson, MD¶ and
- Evan A. Stein, MD, PhD#
- ↵⁎Reprint requests and correspondence:
Dr. Clapton Dias, Amgen, One Amgen Center Drive, Thousand Oaks, California 91320-1799
Objectives The aim of this study was to evaluate the safety, tolerability, and effects of AMG 145 on low-density lipoprotein cholesterol (LDL-C) in healthy and hypercholesterolemic subjects on statin therapy.
Background Proprotein convertase subtilisin/kexin type 9 (PCSK9) down-regulates surface expression of the low-density lipoprotein receptor (LDL-R), increasing serum LDL-C. AMG 145, a fully human monoclonal antibody to PCSK9, prevents PCSK9/LDL-R interaction, restoring LDL-R recycling.
Methods Healthy adults (phase 1a) were randomized to 1 dose of AMG 145: 7, 21, 70, 210, or 420 mg SC; 21 or 420 mg IV; or matching placebo. Hypercholesterolemic adults (phase 1b) receiving low- to moderate-dose statins were randomized to multiple SC doses of AMG 145: 14 or 35 mg once weekly (QW) ×6, 140 or 280 mg every 2 weeks (Q2W) ×3, 420 mg every 4 weeks ×2, or matching placebo. Eleven subjects receiving high-dose statins and 6 subjects with heterozygous familial hypercholesterolemia were randomized to SC AMG 145 140 mg or placebo Q2W ×3.
Results In the trials (AMG 145 n = 85, placebo n = 28), AMG 145 reduced LDL-C up to 64% (p < 0.0001) versus placebo after 1 dose ≥21 mg and up to 81% (p < 0.001) with repeated doses ≥35 mg QW. No serious adverse events (AEs) occurred. Overall incidence of treatment-emergent AEs was similar in AMG 145 versus placebo groups: 69% versus 71% (phase 1a); 65% versus 64% (phase 1b).
Conclusions In phase 1 studies, AMG 145 significantly reduced serum LDL-C in healthy and hypercholesterolemic statin-treated subjects, including those with heterozygous familial hypercholesterolemia or taking the highest doses of atorvastatin or rosuvastatin, with an overall AE profile similar to placebo.
Low-density lipoprotein cholesterol (LDL-C) reduction (especially with statins) is the cornerstone of therapeutic efforts to reduce the risks of both first and subsequent cardiovascular events (1,2). Serum LDL-C levels are predominantly influenced by clearance of apolipoprotein B (ApoB)-containing lipoproteins via the low-density lipoprotein receptor (LDL-R) (3). Proprotein convertase subtilisin/kexin type 9 (PCSK9) plays a major role in regulating hepatic LDL-R activity (3–6). Proprotein convertase subtilisin/kexin type 9 gain-of-function mutations increase plasma LDL-C and the risk of cardiovascular disease (7,8), whereas PCSK9 loss-of-function mutations reduce plasma LDL-C levels and cardiovascular risk (9,10). Several studies indicate that statins increase PCSK9 levels (11–14), suggesting that a PCSK9 antagonist might further reduce LDL-C levels in patients receiving statins.
AMG 145 is a fully human monoclonal antibody (immunoglobulin G2) that binds specifically to human PCSK9, preventing its interaction with the LDL-R and thereby restoring LDL-R recycling and LDL-C uptake (15). We report results from 2 randomized, double-blind, placebo-controlled, ascending-dose phase 1 studies of AMG 145 in healthy adults and in subjects with hypercholesterolemia receiving stable doses of statins.
The phase 1a study enrolled healthy subjects (7 cohorts); the phase 1b study enrolled hypercholesterolemic subjects receiving stable statin therapy (7 cohorts: 5 receiving low- to moderate-dose statins, 1 receiving high-dose statin therapy, and 1 with heterozygous familial hypercholesterolemia (HeFH) (score ≥9, World Health Organization criteria ) (Fig. 1).
The protocol and study procedures were approved by an institutional review board. All subjects provided written informed consent before study procedures were performed.
Study design and treatment
In the phase 1a study, eligible subjects at 1 U.S. center were randomized (1 placebo/3 AMG 145) to a single dose of placebo or AMG 145, 7 mg to 420 mg administered SC or 21 mg or 420 mg administered IV in a 1-h infusion (Fig. 1A). In the phase 1b study, conducted at 10 U.S. centers, subjects receiving low- to moderate-dose statins were randomized 1:3 to subcutaneous placebo or AMG 145 and sequentially assigned to 1 of 5 dose-escalation cohorts (14 mg QW × 6 doses to 420 mg Q4W × 2 doses) (Fig. 1B). The high-dose statin and HeFH cohorts received 140 mg SC Q2W × 3 doses or placebo.
Endpoints and assessments
In both studies, the primary endpoint was the safety and tolerability of AMG 145; secondary endpoints included effects of AMG 145 on serum LDL-C (measured by a homogeneous direct assay). Additional lipid parameters, free PCSK9, Apo-B, and lipoprotein (Lp)(a) levels were also measured. On-study treatment-emergent and treatment-related adverse events (AEs) were reported; treatment-related AEs were those that the investigator felt might have been caused by the investigational product.
Methods used for safety and efficacy assessments are described in the Online Appendix.
Safety analyses included all subjects who received ≥1 dose of AMG 145 or placebo. The analyses of the effects of AMG 145 on lipids included all subjects who received investigational product and had ≥1 post-baseline value. Descriptive statistics were used for demographic, safety, and efficacy data. All placebo subjects were pooled in the phase 1a study. In the phase 1b study, all placebo subjects were pooled for safety analyses; for lipid analyses, placebo subjects were pooled for dose-escalation cohorts and analyzed separately for the high-dose statin and HeFH cohorts. As pre-specified, the ratio of LDL-C and other lipids to baseline at various time points was log-transformed and analyzed by repeated-measures analysis of covariance, with treatment, day, and treatment × day interaction as independent variables; baseline LDL-C as a covariate; and subject as a random effect. Percentage changes were calculated as inverses of the ratios. Repeated-measures analyses analogous to those for LDL-C were done for all efficacy endpoints, and p values were generated.
In the phase 1a study, 56 healthy subjects were randomized and received the investigational product (AMG 145, n = 42; placebo, n = 14) (Fig. 2A). Three AMG 145 subjects discontinued the study after receiving the investigational product, all for personal reasons and none because of AEs. In the phase 1b study, 57 subjects were randomized, received AMG 145 (n = 43) or placebo (n = 14), and completed the study; 3 subjects were randomized but withdrew before receiving the investigational product (Fig. 2B). In both studies, baseline demographic data and disease characteristics were balanced overall between the AMG 145 and placebo groups (Table 1).
Effects of AMG 145 on lipids
Treatment with AMG 145 resulted in significant, dose-dependent reductions in LDL-C in both studies (Fig. 3,Table 2). In the phase 1a study, single doses of AMG 145 ≥21 mg reduced mean LDL-C levels by up to 64% compared with placebo (p < 0.0001). Minimal differences in the magnitude or duration of LDL-C reduction were observed between equivalent subcutaneous or intravenous doses. In the phase 1b study, AMG 145 reduced mean LDL-C levels up to 81% versus placebo (p < 0.001) at nadir and by up to 75% versus placebo (p < 0.001) at the end of the dosing interval. The LDL-C reductions in the high-dose statin and HeFH cohorts were comparable to those in the dose-matched low- to moderate-dose statin cohort (Table 2).
AMG 145 treatment also resulted in significant dose-dependent reductions in ApoB versus placebo in both the phase 1a and 1b studies, up to 55% (p < 0.0001) and 59% (p < 0.001), respectively (Fig. 4,Table 2). In the phase 1b study, ApoB reductions in the high-dose statin and HeFH cohorts were similar to those in the dose-matched low- to moderate-dose statin cohort (Table 2). Treatment with AMG 145 in phase 1b reduced mean serum levels of Lp(a) by 27% (35 mg QW × 6, p = 0.033) to 50% (HeFH cohort 140 mg Q2W × 3, p < 0.001) versus placebo at the end of the dosing interval (Fig. 4, Table 2). Significant, dose-related reductions in total cholesterol were also observed in both studies (Table 2). As expected, no treatment effects were observed on HDL-C or triglyceride levels (data not shown).
AMG 145 significantly reduced free PCSK9 levels in both studies; the magnitude and duration of PCSK9 reductions influenced the extent and duration of LDL-C reductions (Fig. 5). In the phase 1b study, PCSK9 reductions in the high-dose statin and HeFH cohorts were similar to those in the dose-matched low- to moderate-dose statin cohort (data not shown).
Safety, tolerability, and immunogenicity
Key safety data for both studies are summarized in Table 3. The overall incidence of treatment-emergent AEs was similar between the AMG 145 and placebo groups (Table 3). No serious AEs or AEs leading to discontinuation occurred during either study. No clinically important effects of AMG 145 were observed on selected laboratory parameters, electrocardiograms, or vital signs. No neutralizing antibodies to AMG 145 were detected during either study. AEs considered treatment-related by the investigator were reported in 43% of AMG 145 subjects and 71% of placebo subjects in the phase 1a study and in 23% of AMG 145 subjects and 14% of placebo subjects in phase 1b.
One case of myositis was reported as an AE in each of 3 phase 1a subjects (7%, AMG 145). One event was reported as treatment-related; it was mild, occurred 21 days post-dose concurrent with creatine kinase (CK) elevation >2.5 to 5× the upper limit of normal (ULN), and resolved 23 days post-dose. Two moderate, non-treatment-related events were reported in phase 1a; both events occurred more than 80 days after AMG 145 administration, after strenuous physical activity, and were associated with CK elevations (1 subject, >5 to 10× ULN; 1 subject, >10× ULN). In both cases, no investigational product was detectable at the time of the event. In phase 1a, the overall incidence of CK elevation reported as an AE was 21% for AMG 145 and 14% for placebo (Table 3). In phase 1b, no significant differences between AMG 145 and placebo were observed in the incidence of treatment-emergent AEs of potential clinical importance. Two phase 1b subjects receiving AMG 145 (1 each in the high-dose statin and HeFH cohorts) had grade 3 CK elevations after strenuous physical activity.
In 2 randomized, placebo-controlled, phase 1 ascending-dose studies, AMG 145—a fully human monoclonal antibody to PCSK9—significantly lowered serum LDL-C levels compared with placebo in healthy subjects and in subjects with or without HeFH who were receiving stable statin therapy. The reductions in LDL-C, driven by dose-dependent reductions in free PCSK9, were rapid, dose-related, and consistent across cohorts. The LDL-C reduction seemed to be independent of statin type or dose and was consistent with results recently reported in 2 studies using another PCSK9 antibody, REGN727/SAR236553 (17,18). In contrast to the reported results with REGN727/SAR236553 at a high dose (6), Q4W dosing with 420 mg AMG 145 in this study showed sustained reductions (>60%) over the 4-week dosing interval. AMG 145 also significantly reduced ApoB and Lp(a) versus placebo.
Statins are associated with an increase in PCSK9 (11–14), which might theoretically impact the duration of effect with AMG 145 due to increased PCSK9 synthesis and faster antibody clearance. However, the magnitude and duration of LDL-C lowering observed in the cohort receiving the highest doses of atorvastatin or rosuvastatin were comparable to those of subjects receiving lower statin doses after 3 biweekly 140-mg doses of AMG 145.
Robust and sustained reductions in Lp(a) were observed in this study, consistent with those reported for REGN727/SAR236553 (17,18). Lp(a), an LDL-like particle containing an ApoB molecule linked to apolipoprotein (a), is associated with an increased independent risk of coronary heart disease and stroke (19). Other LDL-C-lowering agents that up-regulate LDL-R activity show no effect on Lp(a); thus, the mechanism of Lp(a) reduction with AMG 145 warrants further exploration. The safety and tolerability profile of AMG 145 was similar to that of placebo, and there were no serious AEs or discontinuations because of AEs.
In summary, AMG 145 provided robust, significant reductions in plasma LDL-C levels versus placebo in different groups of hypercholesterolemic subjects with both Q2W and Q4W doses. The overall AE profiles were similar between AMG 145 and placebo groups. Treatment with AMG 145 may provide substantial LDL-C-lowering benefits in patients who do not respond adequately to statins or who cannot meet their LDL-C reduction goals on the highest doses of atorvastatin and rosuvastatin. Phase 2 studies building upon this foundation are in progress.
The authors thank all of the study investigators. They also thank Meera Kodukulla, PhD, and Dikran Toroser, PhD, of Amgen; Rick Davis, MS, RPh, of Complete Healthcare Communications; and Sue Hudson, BA, on behalf of Amgen, for writing and editorial support. The authors thank Ren Xu, PhD, for his significant contributions to the development and management of the various biomarker assays employed in the Phase 1a and 1b studies.
For additional information, please see the online version of this article.
The studies reported in this manuscript were funded by Amgen, Thousand Oaks, California. Dr. Dias, Dr. Shaywitz, Dr. Wasserman, Mr. Colbert, Dr. Cooke, Ms. Crispino, Dr. Emery, Dr. Gibbs, Dr. Retter, Dr. Smirnakis, Dr. Smith, Dr. Stolman, and Mr. Uy are employees of and stockholders in Amgen. Dr. Gao was an Amgen employee and stockholder during the analysis of this study and development of the manuscript. Dr. Matson has no industry relationships to disclose. Dr. Stein has received consulting fees from Amgen, Adnexus Therapeutics, and Sanofi related to proprotein convertase subtilisin/kexin type 9 inhibitors, and his institution has received research funding related to proprotein convertase subtilisin/kexin type 9 clinical trials from Amgen, Sanofi, and Regeneron.
- Abbreviations and Acronyms
- adverse event
- apolipoprotein B
- creatine kinase
- high-density lipoprotein cholesterol
- heterozygous familial hypercholesterolemia
- low-density lipoprotein cholesterol
- low-density lipoprotein receptor
- lipoprotein (a)
- proprotein convertase subtilisin/kexin type 9
- every 2 weeks
- every 4 weeks
- Received May 22, 2012.
- Revision received August 8, 2012.
- Accepted August 30, 2012.
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