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PCSK9 http://circ.ahajournals.org/content/vol124/21_MeetingAbstracts

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Arsenault BJ, Huijgen R, Boekholdt SM, et al. Abstract 14235: Plasma PCSK9 Levels and Clinical Outcomes in the Treating to New Targets Trial: A Nested Case-Control Study. Circulation 2011;124(21 Supplement):A14235. http://circ.ahajournals.org/cgi/content/meeting_abstract/124/21_MeetingAbstracts/A14235

Background - Statins activate low-density lipoprotein (LDL) receptor gene expression, thus lowering plasma LDL levels. But statins also activate the expression of proprotein convertase subtilisin kexin type 9 (PCSK9), a secreted inhibitor of the LDL receptor, thereby limiting their beneficial effects. Clinical studies have shown that statin therapy may increase plasma PCSK9 levels. Here, we have hypothesized that increasing statin dose would increase circulating PCSK9 levels and that high levels of PCSK9 would in fact increase cardiovascular risk in statin treated patients.

Methods and Results - We have measured plasma PCSK9 in a subgroup of patients with stable coronary heart disease (CHD) enrolled in the Treating to New Targets (TNT) clinical trial. After a run in period with atorvastatin 10 mg daily, patients were randomized to either continue with 10 mg (n=849) or to 80 mg of atorvastatin (n=764), and followed 5 years for major cardiovascular events (MCVE). MCVE was defined as CHD death, nonfatal, non-procedure-related myocardial infarction, resuscitated cardiac arrest, and fatal or nonfatal stroke. PCSK9 levels one year after randomization did not differ significantly between the 10 and 80 mg atorvastatin treatment groups (318 ng/mL; IQR 231-417 ng/mL vs. 311 ng/mL; IQR 231-407 ng/mL, P=0.82). There were no significant differences between the two treatment groups in terms of change in PCSK9 between the randomization and 1-year post-randomization levels. Circulating PCSK9 levels measured at randomization were predictive of clinical outcomes in the group randomized to remain on atorvastatin 10 mg (adjusted hazard ratio per 100 ng/ml of PCSK9 level = 1.08 [95% CI, 1.04-1.16], p=0.026), but not in the group that intensified atorvastatin treatment to 80 mg (adjusted hazard ratio per 100 ng/ml of PCSK9 level = 0.95 [95% CI, 0.86-1.04], p=0.22).

Conclusion - Increasing statin dose from 10 to 80 mg did not increase plasma PCSK9 levels. PCSK9 levels predict cardiovascular events in patients treated with low dose atorvastatin.

Author Disclosures: B.J. Arsenault: Honoraria; Modest; Pfizer. R. Huijgen:None. S. Boekholdt: Honoraria; Modest; Pfizer. W. Bao: Employment; Significant; Pfizer. F. Tabet: None. F. Petrides: None. K. Rye: None. D.A. DeMicco: Employment; Significant; Pfizer. P.J. Barter: Honoraria; Modest; Abbott, AstraZeneca, Merck, Pfizer, Roche and Sanofi-Aventis. Consultant/Advisory Board; Modest; AstraZeneca, CSL, Merck, Pfizer, Roche and Sanofi-Aventis. J.J. Kastelein: Honoraria; Modest; Pfizer. G. Lambert: None.



Kawashiri M-a, Ikewaki K, Tada H, et al. Abstract 14785: Impact of Impaired LDL Catabolism and Increased VLDL and VLDL Remnant Production on Hypercholesterolemia in Homozygous PCSK9 Gene Mutation: Evidence from Kinetic Study with Stable Isotope. Circulation 2011;124(21 Supplement):A14785. http://circ.ahajournals.org/cgi/content/meeting_abstract/124/21_MeetingAbstracts/A14785

Background: Statin activates sterol regulatory element binding protein 2 (SREBP2) due to depletion of cholesterol in hepatocyte and results both in induction of low-density lipoprotein (LDL) receptor and proprotein convertase subtilisin/kexin type 9 (PCSK9) gene. PCSK9 is known to increase the degradation of LDL receptor, thus it may cancel a part of LDL-cholesterol lowering effect of statin. Moreover, PCSK9 is recognized as a third cause of familial hypercholesterolemia (FH). Although we identified 2 true homozygous FH patients with PCSK9 gene mutation (E32K), few data exist regarding the detailed metabolism of homozygous FH due to PCSK9 gene mutation compared with normal controls. Therefore, we examined lipoprotein metabolism in homozygous FH patients with PCSK9 gene mutation (E32K) using stable isotope method.

Methods and Results: We enrolled 2 homozygous FH patients with PCSK9 E32K mutation (female=2, 53±9yr., LDL-C=286±42mg/dL) and 8 control subjects (female=1, 41±8yr., LDL-C=119±19mg/dL) who were given 10mg/kg of [2H3]-leucine after wash-out of any lipid lowering drugs. Tracer/tracee ratio of apolipoprotein B (apoB) was determined by GC-MS and fractional catabolic rate (FCR) were determined by multi-compartment modeling. As expected, FCR of LDL apoB of homozygous FH with PCSK9 gene mutation (E32K) was significantly lower than those of controls (0.217±0.021 vs. 0.455±0.114 pools/day). Interestingly, the production rate of very-LDL (VLDL)(29.6±1.5 vs. 12.7±4.5), the direct removal of VLDL (42±6 vs. 15±19%) and VLDL remnant (41±5 vs. 2±2%) were significantly greater compared with those of controls, suggesting the existence of another metabolic pathway of VLDL remnant.

Conclusion: Homozygous patients with PCSK9 gene mutation (E32K) showed impaired catabolism of LDL as well as VLDL. Thus, inhibition of PCSK9 may be alternative method for further cholesterol lowering therapy over statin alone.

Author Disclosures: M. Kawashiri: Research Grant; Significant; Ministry of Education, Culture, Sports, Science and Technology of Japan. K. Ikewaki: None.H. Tada: None. T. Noguchi: None. A. Nohara: None. A. Inazu: None. J. Kobayashi: None. H. Mabuchi: None. M. Yamagishi: None.


Melone M, Rashid S. Abstract 9763: Discovery of a New Role of Human Resistin in Hepatocyte Low-Density Lipoprotein (LDL) Receptor Suppression Mediated by PCSK9. Circulation 2011;124(21 Supplement):A9763. http://circ.ahajournals.org/cgi/content/meeting_abstract/124/21_MeetingAbstracts/A9763

Background: Serum levels of the adipose tissue-derived signalling protein, resistin, are increased in human obesity and are positively correlated with atherosclerotic cardiovascular disease (ASCVD). However, the function of resistin in humans has been enigmatic. An elevation in serum low-density lipoprotein (LDL) levels is both necessary and sufficient for ASCVD development in humans. However, few physiological factors have been identified that directly affect LDL levels through its main receptor, the LDL receptor (LDLR). In this study, we wished to determine if human resistin plays a role in regulating the uptake of atherogenic LDL in human hepatocytes.

Methods: Human hepatocytes (HepG2 and primary) were treated for 24 hours with: (1.) purified human resistin at various concentrations, with and without PCSK9 siRNA, and with and without lovastatin; and (2.) obese human serum with elevated resistin levels or serum from which resistin was removed via antibody-immunoprecipitation. The effect of the treatments on cellular LDL receptor (LDLR) and PCSK9 mRNA and protein levels were determined via real-time PCR and Western blotting, respectively.

Results: Resistin, at physiological levels observed in human obesity (50 ng/mL), downregulated hepatocyte LDLR expression substantially by 40%. A key mechanism by which human resistin inhibited hepatocyte LDLR was via increased expression of the recently identified protease, PCSK9, which enhances intracellular LDLR lysosomal degradation. To support this notion, we showed that the addition of resistin reversed the marked over 100% elevation in LDLR expression induced with PCSK9 siRNA treatment. The quantitatively important role of human resistin in LDLR expression was demonstrated by antibody-immunoprecipitation removal of resistin in obese human serum, which increased serum stimulation of LDLR markedly by 80%. Furthermore, resistin diminished statin-mediated upregulation of LDLR by 70%, implicating resistin in the relative ineffectiveness of statins in selective target populations.

Conclusions: These results reveal for the first time that resistin is potentially a highly attractive therapeutic target in ameliorating elevated serum LDL, and, thereby, ASCVD, in obese humans.

Author Disclosures: M. Melone: None. S. Rashid: None.


Dias C, Shaywitz A, Smith B, et al. Abstract 10701: A Phase 1, Randomized, Double-Blind, Placebo-Controlled, Ascending Single Dose Study to Evaluate the Safety, Tolerability and Pharmacodynamics of AMG145. Circulation 2011;124(21 Supplement):A10701. http://circ.ahajournals.org/cgi/content/meeting_abstract/124/21_MeetingAbstracts/A10701

Introduction: The low-density lipoprotein receptor (LDL-R) plays a vital role in maintenance of cholesterol and plasma low-density lipoprotein-cholesterol (LDL-C) levels. Proprotein convertase subtilisin/kexin type 9 (PCSK9) downregulates LDLR levels, leading to increased circulating LDL-C. We assessed the hypothesis that AMG145, a fully human monoclonal antibody against PCSK9, lowers circulating LDL-C. Herein, we report the first-in-human randomized, double-blind, placebo-controlled, ascending-single-dose study of AMG145 in healthy volunteers.

Methods: 7 dose cohorts (A-G) were used in healthy adult subjects to evaluate safety, tolerability, pharmacokinetics and pharmacodynamics (LDL-C). 5 SC cohorts and 2 IV cohorts were employed in this trial. N=8 in each cohort, randomized 3:1, AMG145:placebo. Eligibility criteria included: age 18-45 years, LDL-C 100-190 mg/dL; body mass index 18-32 kg/m2 and no comedications 14 days prior. Safety and tolerability following a single dose was the primary endpoint.

Results: Single SC and IV administrations of AMG145 decreased mean LDL-C up to 64% relative to placebo subjects. The magnitude of LDL-C lowering, time to nadir, and duration of LDL-C lowering were all dose-dependent. Qualitatively, results for total cholesterol and apo-B were similar to those for LDL-C. AMG145 potently suppressed serum unbound PCSK9. The dose response for decrease in unbound PCSK9 correlated well with the dose responses for decreases in LDL-C, total cholesterol, and apo-B. AMG145 had no effects on serum triglycerides, HDL-C, or apo-A1. No serious adverse events were reported and no subjects discontinued the study due to an adverse event. The incidence of treatment-emergent adverse events was similar among subjects treated with AMG145 and subjects treated with placebo. No relationship was apparent between the subject incidence of adverse events and the dose of AMG145.

Conclusions: AMG145 decreased unbound PCSK9 levels and lowered circulating LDL-C, total cholesterol and apo-B. Single doses of administered SC and IV were well tolerated in healthy volunteers.

Author Disclosures: C. Dias: Employment; Significant; Amgen inc. A. Shaywitz:Employment; Significant; Amgen Inc. B. Smith: Employment; Significant; Amgen Inc. M. Emery: Employment; Significant; Amgen Inc. G. Bing: Employment; Significant; Amgen Inc. J. Gibbs: Employment; Significant; Amgen Inc. B. Wishner: Employment; Significant; Retired Amgen Inc employee. D. Stolman:Employment; Significant; Amgen Inc. C. Crispino: Employment; Significant; Amgen Inc. C. Crispino: Employment; Significant; Amgen Inc. B. Cook:Employment; Significant; Amgen Inc. A. Colbert: Employment; Significant; Amgen Inc. M. Retter: Employment; Significant; Amgen Inc. R. Xu: Employment; Significant; Amgen Inc. M. Matson: Other; Significant; Principal Investigator.


Swergold G, Smith W, Mellis S, et al. Abstract 16265: Inhibition of Proprotein Convertase Subtilisin/Kexin Type 9 With a Monoclonal Antibody REGN727/SAR236553, Effectively Reduces Low-Density-Lipoprotein Cholesterol, as Mono or Add-on Therapy in Heterozygous Familial and Non Familial Hypercholesterolemia. Circulation 2011;124(21 Supplement):A16265. http://circ.ahajournals.org/cgi/content/meeting_abstract/124/21_MeetingAbstracts/A16265

Since 2003 understanding of proprotein convertase subtilisin/kexin type 9 (PCSK9) has advanced from discovery to in vitro, animal, genetic and observational studies to suggest that inhibition of PCSK9 should result in up regulation of hepatic LDL receptors and decrease in LDL cholesterol (LDLc). We report a randomized, double-blind, placebo-controlled, multiple ascending dose trial (NCT01161082 ) to determine if REGN 727/SAR236553 (REGN727), a fully human monoclonal antibody to PCSK9 was safe and effective in patients with Heterozygous Familial Hypercholesterolemia (FH) or other forms of primary hypercholesteremia (nonFH). The study enrolled 61 adults with either FH (n=21) or nonFH (n=30), both on diet plus stable atorvastatin therapy (atorvaRx), or nonFH (n=10) on diet alone. AtorvaRx patients received doses of 10-40 mg and had LDLc 100 mg/dL; those on diet alone LDLc 130 mg/dL. REGN727 was administered subcutaneously at doses of 50, 100 and 150 mg on days 1, 29 and 43. The primary endpoint was the incidence and severity of treatment emergent adverse events (TEAEs). Of 109 patients screened 61were randomized (14 placebo, 47 REGN727) with 100% completing 148 +/–7 days of treatment and follow up. FH were younger than nonFH patients (mean 40 vs 52 yrs), and were on higher doses of atorvastatin (52% on 40 mg). Baseline LDLc was 134, 111, and 179 mg/dL in the FH atrovaRX, nonFH atorvaRx and nonFH diet only groups respectively. No serious adverse events were seen and treatment was generally well tolerated. No drug-related adverse effects were seen on liver function testing or other laboratory parameters. TEAEs that occurred in > 5% of REGN727 treated patients were Headache (n=8), Nasopharyngitis (n=5), and Upper Respiratory Infection (n=3). On day 57, 14 days after the 3rd dose of REGN727, mean % reductions in LDLc on top of statins were 35.6%, 50.2% and 57.5% at the 50, 100 and 150 mg doses, respectively in the combined FH and nonFH populations. There were no apparent differences in response between FH and nonFH or those on or not on statin therapy. Favourable changes were observed in HDLc and apoA1.

We conclude that the PCSK9 inhibitor, REGN727/SAR236553, appears to be a promising therapeutic option for patients with or without FH and elevated LDLc on atorvastatin therapy.

Author Disclosures: G. Swergold: Employment; Significant; Regeneron Pharmaceuticals, Inc. W. Smith: Research Grant; Modest; Regeneron Pharmaceuticals, Inc. S. Mellis: Employment; Significant; Regeneron Pharmaceuticals, Inc. D. Logan: Research Grant; Modest; Regeneron Pharmaceuticals, Inc. C. Webb: Research Grant; Modest; Regeneron Pharmaceuticals, Inc. R. Wu: Employment; Significant; Regeneron Pharmaceuticals, Inc. Y. Du: Employment; Significant; Regeneron Pharmaceuticals, Inc. T. Krans: Research Grant; Modest; Regeneron Pharmaceuticals, Inc. E. Gasparino: Employment; Significant; Regeneron Pharmaceuticals, Inc. E.A. Stein: Research Grant; Significant; Regeneron Pharmaceuticals, Inc..