Design and Rationale of the LAPLACE-TIMI 57 Trial: A Phase II, Double-Blind, Placebo-Controlled Study of the Efficacy and Tolerability of a Monoclonal Antibody Inhibitor of PCSK9 in Subjects With Hypercholesterolemia on Background Statin Therapy
Payal Kohli MD,
TIMI Study Group, Cardiovascular Division, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA
Lowering low-density lipoprotein cholesterol (LDL-C) is a cornerstone for the prevention of atherosclerotic heart disease, improving clinical outcomes and reducing vascular mortality in patients with hypercholesterolemia. The clinical benefits of LDL-C reduction appear to extend even to patients starting with LDL-C as low as 60–80 mg/dL prior to initiating therapy. Statins are the first-line agents for treating hypercholesterolemia and are effective in reducing LDL-C, but many patients are unable to achieve their optimal lipid targets despite intensive statin therapy. Therefore, there has been a strong impetus for the development of novel pharmacologic agents designed to lower LDL-C further in patients already on statin therapy. Genetic mutations resulting in altered cholesterol homeostasis provide valuable information regarding novel approaches for treating hypercholesterolemia. To that end, mutations in proprotein convertase subtilisin/kexin type 9 (PCSK9) were linked to altered levels of LDL-C, illustrating this protein's role in lipid metabolism. PCSK9 promotes degradation of the LDL receptor, preventing its transport back to the cell surface and thereby increasing circulating LDL-C. Conversely, inhibition of PCSK9 can profoundly decrease circulating LDL-C, and thus is an attractive new target for LDL-C–lowering therapy. AMG 145 is a fully human monoclonal immunoglobulin G2 antibody that binds specifically to human PCSK9 and inhibits its interaction with the low-density lipoprotein receptor. In this manuscript, we describe the rationale and design of LDL-C Assessment with PCSK9 Monoclonal Antibody Inhibition Combined With Statin Therapy–Thrombolysis In Myocardial Infarction 57 (LAPLACE-TIMI 57; NCT01380730), a 12-week, randomized, double-blind, dose-ranging, placebo-controlled study designed to assess the safety and efficacy of AMG 145 when added to statin therapy in patients with hypercholesterolemia. Clin. Cardiol. 2012. doi: 10.1002/clc.22014
This trial was supported by Amgen. Payal Kohli, Nihar R. Desai, Robert P. Giugliano, Timothy Abrahamsen, Shannon McDonald and Marc S. Sabatine are members of the TIMI Study Group, which received research grant support from Amgen for the conduct of this trial. Payal Kohli has received honorarium for consultation from Daiichi-Sankyo. Robert P. Giugliano has received honoraria for lectures and consultation from Amgen, Merck, Regeneron, and Sanofi-Aventis, and research-grant support from Merck for work related to lipid-lowering therapies. Marc S. Sabatine has received research-grant support from AstraZeneca, Bristol-Myers Squibb/Sanofi-Aventis Joint Venture, Merck, and Pfizer and honoraria for lectures and consultation from Amgen, Bristol-Myers Squibb/Sanofi-Aventis Joint Venture, GlaxoSmithKline, Merck, and Pfizer. Jae B. Kim, Ransi Somaratne, Fannie Huang, Beat Knusel, Scott M. Wasserman, and Robert Scott are employees and stockholders of Amgen, Inc.
Payal Kohli, MD, and Nihar R. Desai, MD, MPH, contributed equally to this work.
The authors have no other funding, financial relationships, or conflicts of interest to disclose.
Morbidity and mortality from cardiovascular disease impose a significant burden on healthcare resources and remain the number one cause of death worldwide.1 There is a robust inverse relationship between low-density lipoprotein cholesterol (LDL-C) and the occurrence of major vascular events.2–5 To that end, reducing circulating levels of LDL-C has consistently been shown to reduce the risk of major vascular events, including vascular death, in patients with hypercholesterolemia,3,6,7 both in primary as well as secondary prevention. More recently, this finding also appears to apply to patients who already have low baseline LDL-C values (eg, <60–80 mg/dL) whether in a primary8 or secondary prevention setting.9 Importantly, pharmacologically achieving LDL-C concentrations <40 mg/dL appears to be safe and well-tolerated.8,10–14 Although statins, the first-line agents for treating hypercholesterolemia, are effective in reducing LDL-C, many patients are unable to achieve their optimal lipid targets despite intensive statin therapy.7,15 With the advent of guidelines endorsing lower LDL-C targets (LDL-C <70 mg/dL or <1.8 mmol/L) in very-high-risk patients, there is an increasing awareness of the limits of LDL-C lowering that can be achieved with statin monotherapy and consequently the need for adjunctive therapy. Therefore, there has been a strong impetus for the development of new pharmacologic agents to lower LDL-C further in patients already being treated with statins.
Inhibiting Proprotein Convertase Subtilisin/Kexin Type 9
One novel approach to decreasing circulating LDL-C is inhibition of LDL-receptor (LDL-R) regulation and recycling. Gain-of-function mutations in the proprotein convertase subtilisin/kexin type 9 (PCSK9) gene cause autosomal dominant hypercholesterolemia, with elevated LDL-C and associated premature coronary artery disease.16 Conversely, loss-of-function mutations in PCSK9 are associated with a lifelong decrease in LDL-C (28%–40% lower) and lower risk of coronary heart disease (47%–88% lower).17–21 Individuals with 2 loss-of-function alleles, resulting in no detectable PCSK9 levels, typically have very low plasma LDL-C levels (<20 mg/dL) without any apparent adverse clinical consequences from absence of PCSK9.20,21
In animal models, administration of PCSK9 inhibitors markedly lowers LDL-C.14,15 Similarly, in gene-inactivation studies, PCSK9−/− mice demonstrated a 4-fold decrease in the accumulation of cholesteryl esters than did wild-type mice, whereas transgenic mice overexpressing PCSK9 developed more severe aortic lesions and had an accumulation of cholesteryl esters in the aorta.22
The mechanism by which PCSK9 influences LDL-C levels has not been fully elucidated. However, PCSK9 routes the LDL-R to lysosomal degradation, instead it being recycled to the hepatocyte cell surface, thereby regulating the cell-surface expression of LDL-R and removal of LDL-C from the circulation. Further, low intrahepatocyte levels of cholesterol lead to sterol regulatory element-binding protein activation with consequent increased expression of LDL-R and PCSK9.23,24 This phenomenon raises the possibility that PCSK9 up-regulation may play a role in the diminishing returns of LDL-C lowering seen with increasing doses of statins. Results from a randomized controlled trial of a high-potency statin vs. placebo have demonstrated up-regulation of PCSK9 following treatment with statins.25 To that end, inhibiting PCSK9 in murine models results in increased sensitivity to statins, suggesting possible synergy between these 2 pathways in regulating LDL-C and revealing a novel therapeutic target in patients on statins.14
AMG145: A Monoclonal Antibody Inhibitor of Proprotein Convertase Subtilisin/Kexin Type 9
AMG 145 (Amgen, Thousand Oaks, CA) is a fully human monoclonal antibody (immunoglobulin G2) that binds specifically to human PCSK9. This binding prevents the PCSK9–LDL-R interaction, leading to a near-complete absence of detectable unbound PCSK9 immediately after administration and concurrent reduction in circulating LDL-C by 50% to 70% following a single dose of ≥70 mg in healthy volunteers. The duration of this effect is dose dependent and the LDL-C nadir is observed within 2 weeks of dosing.26 Phase Ib data27 in subjects on stable statin therapy demonstrated a dose-dependent decrease in LDL-C and unbound PCSK9 with increasing subcutaneous doses of AMG 145. Low-density lipoprotein cholesterol was lowered by up to 81% at maximal doses, over and above the LDL-lowering achieved with statin alone.27 Similar findings were observed from data of another PCSK9 antibody.28,29 Regarding the safety and tolerability, both phase Ia26 and phase Ib27 data reported no serious adverse events in the AMG 145 group compared with placebo, no discontinuations from the studies related to adverse events, and only 1 case of transaminase elevation >3× upper limit of normal. There were no trends indicative of a clinically important effect of AMG 145 on hepatic-function tests. There were also no cases of creatine kinase elevations (>5×) that were considered related to study drug. Notably, the subcutaneous injections were well-tolerated with no severe injection-site reactions.
In this report, we describe LDL-C Assessment with PCSK9 Monoclonal Antibody Inhibition Combined With Statin Therapy–Thrombolysis In Myocardial Infarction 57 (LAPLACE-TIMI 57), a phase II trial designed to assess safety, tolerability, and efficacy of different doses and dosing frequencies of AMG 145 in patients with hypercholesterolemia on statin therapy to define the optimal regimen(s) for future studies.
Study Design and Objectives
LAPLACE–TIMI 57 (NCT01380730) is a 12-week, randomized, double-blind, dose-ranging, placebo-controlled study designed to assess the safety, tolerability, and efficacy of AMG 145 when added to ongoing statin therapy in subjects with hypercholesterolemia (Figure 1). The primary objective of the study is to assess the effect of 12 weeks of therapy with AMG 145, administered every 2 weeks (Q2W) or every 4 weeks (Q4W), on percent change from baseline in LDL-C as compared with placebo. In addition, secondary objectives include evaluation of the safety and tolerability of the study treatment, characterization of the pharmacokinetics of AMG 145, and the effects of AMG 145 on other lipid parameters (e.g. non–high-density lipoprotein cholesterol [HDL-C], apolipoprotein B [ApoB], total cholesterol/HDL-C, and ApoB/ApoA1).
Subjects age 18 to 80 years (inclusive) with known hypercholesterolemia (LDL-C ≥85 mg/dL) on statin therapy (with or without concomitant ezetimibe) were eligible for screening. If a subject was on a nonstatin lipid-modifying agent (other than ezetimibe) prior to enrollment, the investigator could withdraw this therapy and allow for a 4-week “wash-out” period prior to screening the subject again for enrollment. Subjects with a recent acute coronary syndrome, severe heart failure, or a recent serious arrhythmia were excluded, as were subjects with severe chronic kidney disease or other major medical comorbidities. The full inclusion and exclusion criteria are listed in Table 1.
GI, endocrine, metabolic, or hematological dysfunction
Malignancy (except non-melanoma skin cancers, cervical cancer in situ, ductal carcinoma in situ, or stage I prostate cancer) within 5 years
Premenopausal female subjects who are pregnant or breastfeeding or have inadequate birth control
Sensitivity to AMG 145 or anti-PCSK9 therapy
Inability to provide informed consent or attend follow-up visits
Unreliability as a participant or alcohol/drug dependence in the past year
Currently enrolled in another investigational device or drug study, <30 days since ending another investigational device or drug study
After signing informed consent, eligible subjects entered a screening phase that lasted for up to 6 weeks. During this period, fasting LDL-C was measured, safety laboratory values were assessed, and the subject received a subcutaneous (SC) placebo injection of 6 mL of normal saline (administered as 3 injections of 2 mL each). Subjects who met all eligibility criteria and tolerated the placebo injection were eligible for randomization.
Subjects were randomized in an equal fashion across all 8 treatment arms (Figure 1). Randomization was stratified by screening LDL-C (<130 mg/dL vs ≥130 mg/dL) and concomitant use of ezetimibe. Enrollment of subjects with fasting LDL-C of 85 to 100 mg/dL was to be limited to ≤20% of the overall cohort. The treatment arms were designed to study 2 dosing frequencies: every 2 weeks (Q2W) and every 4 weeks (Q4W). To maintain blinding within each dosing frequency, the Q2W and Q4W each had its own matching placebo arm. Within the Q2W group, there were 3 active treatment arms, with doses of 70 mg, 105 mg, and 140 mg (each consisting of a 2-mL injection administered SC Q2W); within the Q4W group, the doses were 280 mg, 350 mg, and 420 mg (each consisting of 6 mL administered SC Q4W) (Figure 1). All subjects returned to the investigative center every 2 weeks for study visits (regardless of the dosing frequency of study drug), during which they were examined and assessed for adverse events (AEs), concurrent treatment, and dietary changes, and provided blood samples for measurements of plasma lipids and collection of safety laboratories. Throughout the duration of the study, assessment of unblinded lipids, lipoprotein profiles, or high-sensitivity C-reactive protein was prohibited. Laboratory assessments were conducted centrally at the study core laboratories (Medpace Reference Laboratories [MRL], Cincinnati, OH, for lipids; and Covance Central Laboratory Services, Inc., Indianapolis, IN, for safety laboratories).
Subjects were instructed to maintain their diet and exercise regimen for the duration of the study. No change in the statin regimen was permitted from 4 weeks prior to randomization to the final study visit. Likewise, ezetimibe was permitted at the discretion of the investigator up to 4 weeks prior to randomization, but it could not be added, changed, or discontinued between 4 weeks prior to randomization and the end of the study. Nonstatin lipid-modifying therapies, including red yeast rice, niacin >200 mg daily, fibrates, or ω-3 fatty acids >1000 mg daily, were not permitted at any time during the study. Vitamin A derivatives, cyclosporine, systemic steroids, or hormone therapy were not allowed due to their effect on lipids. The final study visit procedures, including a review of AEs, were conducted 4 weeks after the last injection for each dosing frequency (at 14 weeks for subjects on every 2 week injections and at 12 weeks for subjects on monthly injections). Subjects who discontinued the study drug prematurely were to be followed until the end of the study, including measurement of LDL-C at all study visits. At the conclusion of the study, each subject who successfully completed LAPLACE-TIMI 57 was given the option of enrolling in an ongoing open-label extension (Open Label Study of Long-Term Evaluation Against LDL-C Trial [OSLER], NCT01439880) receiving open-label AMG 145 and standard of care or standard of care alone, randomized in a 2:1 fashion, respectively.
The primary endpoint of LAPLACE-TIMI 57 is the percent change in LDL-C, measured using ultracentrifugation, from baseline (defined as the mean of the 2 most recent fasting concentrations measured through the central laboratory prior to and on the day of randomization) to week 12. Secondary efficacy endpoints include absolute change in LDL-C from baseline to week 12, percent change in non–HDL-C and ApoB from baseline to week 12, and percent change in the ratio of total cholesterol/HDL-C and Apo B/ApoA1 from baseline to week 12. Additional exploratory endpoints include the absolute and percent change from baseline at each scheduled visit in various lipid and nonlipid parameters, as well as the incidence of clinical events including death, cardiac or cerebrovascular ischemic events, coronary and noncoronary revascularizations, and hospitalizations for heart failure. Key safety endpoints include the subject incidence of AEs and the incidence of anti-AMG 145 antibodies. Pharmacokinetics endpoints include the serum concentration of PCSK9 and AMG 145 at selected visits, as well as the maximum concentration of AMG 145 after administration (Cmax), the duration of maximum concentration after administration (Tmax), and the area under the curve (AUCt) obtained between weeks 8 and 12.
Statistical Design and Analysis
We estimated that 600 subjects, approximately 75 subjects in each of the 8 treatment groups, would provide approximately 99% power to detect at least a 20% reduction in LDL-C with AMG 145 (either Q2W or Q4W) compared with placebo.
For each dosing frequency, the primary efficacy endpoint will be analyzed using an analysis of covariance (ANCOVA) model to assess the efficacy of each AMG 145 dose group to placebo. The ANCOVA model will include terms for the treatment group and stratification factors. The highest dose will be compared with placebo using the 0.05 significance level. If the highest AMG 145 dose is found to reach statistical significance, the next-highest dose will be assessed using a closed testing procedure. Testing of the doses will continue in descending strength until the 0.05 statistical significance is not met or the lowest dose within the dosing frequency is tested, whichever occurs first. Missing values will be imputed using the last observation carried forward approach.
Analyses will be performed in all randomized subjects who have received ≥1 dose of study drug by randomized treatment group (a modified intention-to-treat analysis). Additional analyses for the primary endpoint will be performed using on-treatment analysis sets. Analyses of secondary endpoints will be similar to the primary analysis for the primary endpoint with no adjustment for multiple comparisons, at a significance level of 0.05. For the exploratory endpoints, lipid parameters will be examined by scheduled visit and the subject incidence of adjudicated events will be summarized.
For the analysis of safety data, the subject incidence of treatment-emergent AEs will be tabulated by system organ class and preferred term by randomized treatment group. Adverse events will be coded using version 14.0 or higher of the Medical Dictionary for Regulatory Activities. The incidence and percentages of subjects who develop anti-AMG 145 antibodies (binding and neutralizing) will be reported.
Independent Data Monitoring Committee
An external independent data monitoring committee was established to formally review the accumulating data from this and other ongoing phase II studies with AMG 145 to ensure there is no avoidable increased risk for harm to subjects (see Appendix). Analyses for the data monitoring committee will be provided by an independent biostatistical group that is external to TIMI and Amgen.
Independent Clinical Endpoint Committee
Although only a limited number of cardiovascular events are expected in this study, an independent clinical endpoint committee blinded to treatment allocation will adjudicate all deaths, suspected cardiac or cerebrovascular ischemic events, coronary and noncoronary revascularizations, hospitalizations for heart failure, and suspected adverse muscle events using standard endpoint definitions30 (see Appendix).
The objectives of this substudy are to further characterize the pharmacokinetic parameters of AMG 145 and PCSK9 levels after multiple SC dose administrations. In addition to the pharmacokinetic samples collected every 2 weeks in all subjects in the trial, additional pharmacokinetic samples will be obtained at weeks 9 and 11 in ≥120 subjects (approximately 15 subjects per treatment arm).
Biomarkers and Pharmacogenetics:
All subjects enrolled in LAPLACE-TIMI 57 will participate in the biomarker substudy, for which 14.5 mL of blood will be collected at baseline and weeks 2, 4, and 12 for the analysis of biomarkers related, but not limited, to PCSK9 signaling, LDL-R turnover, cholesterol metabolism, inflammation, and plaque stability. There is also an optional pharmacogenetic substudy that will allow exploration of the association of relevant genetic variants with lipid levels, the response to PCSK9, inflammatory biomarkers, and other parameters.
LAPLACE-TIMI 57 is a collaboration between the TIMI Study Group (an Academic Research Organization based at Brigham and Women's Hospital and Harvard Medical School) and Amgen, the sponsor. A joint leadership team consisting of members of the TIMI Study Group and Amgen oversees all aspects of the trial (see Appendix). The study is being conducted in 102 sites across 5 countries: Canada, Czech Republic, Denmark, Hungary, and the United States.
Subject recruitment began on July 6, 2011, and was completed on December 22, 2011. A total of 934 subjects were screened, and from this group 631 subjects were randomized into the trial. Baseline characteristics of the 629 subjects who received ≥1 dose of study drug are shown in Table 2. Results are based on the interim data snapshot taken February 2, 2012.
Table 2. Baseline Characteristics (N = 629)
Abbreviations: BMI, body mass index; CAD, coronary artery disease; DBP, diastolic blood pressure; DM, diabetes mellitus; HDL-C, high-density lipoprotein cholesterol; IQR, interquartile range; LDL-C, low-density lipoprotein cholesterol; N, number of subjects randomized and dosed; PVD, peripheral vascular disease; SBP, systolic blood pressure; TG, triglycerides. a Metabolic syndrome is defined by ≥3 of the following: elevated waist circumference (≥102 cm for non-Asian men, ≥88 cm for non-Asian women, ≥90 cm for Asian men, or ≥80 cm for Asian women); TG ≥150 mg/dL; HDL-C <40 mg/dL in men or <50 mg/dL in women; SBP ≥130 mm Hg, DBP ≥85 mm Hg, or history of hypertension; fasting glucose ≥110 mg/dL or type 2 DM. Results are based on interim data snapshot taken February 2, 2012.
PCSK9 is a newly recognized mediator of LDL-C levels through its role in LDL-C receptor degradation.31 Genetic studies have identified loss-of-function mutations in PCSK9 that are associated with increased density of LDL-R, higher rate of clearance of LDL-C from plasma, very low levels of LDL-C, and low rates of cardiovascular events.14,15 Thus, inhibition of PCSK9 has become an attractive target to reduce LDL-C.26,27,32 AMG 145 is a fully human monoclonal antibody that inhibits PCSK9–LDL-R binding and profoundly lowers LDL-C when given either as monotherapy or in combination with statin therapy. The LAPLACE-TIMI 57 trial is studying the LDL-C–lowering efficacy and the safety of AMG 145 in subjects with hypercholesterolemia being treated with statins and has important implications for the dose selection and design of a definitive phase III cardiovascular outcomes trial in subjects with cardiovascular disease at high risk for events.
TIMI Study Group, Brigham and Women's Hospital, Boston, MA: Marc S. Sabatine (study chairman), Robert P. Giugliano (principal investigator), Payal Kohli (co-investigator), Nihar Desai (co-investigator), Suzanne E. Morin (director of operations), Timothy Abrahamsen (senior project director), Shannon McDonald (project director), Samantha Berg (research assistant), Alexandria Cavalieri (research assistant), Andrea Dedonato (research assistant), Mia DiFabbio (research assistant).
Amgen, Thousand Oaks, CA: Rob Scott (vice president, global development), Scott M. Wasserman (executive medical director, global development), Moetaz Albizem (director, global study management), Ransi Somaratne (clinical research medical director), Jae Kim (clinical research medical director), Beat Knusel (development clinical director), Fannie Huang (biostatistics manager), Sarah Hubbard (clinical research study manager), Paul-Michael Johnson (clinical research study manager), Hayley Sloan (global study management, senior associate).
Clinical Events Committee, Boston, MA: Stephen D. Wiviott (chairman).
Independent Data Monitoring Committee: Charles H. Hennekens, (chairman), W. Virgil Brown, Barry Davis.