What role will proprotein convertase subtilisin/kexin type 9 inhibitors play in hyperlipidemia management?

PURPOSE OF REVIEW

This article summarizes the role that the recently approved proprotein convertase subtilisin/kexin type 9 (PCSK9) monoclonal antibodies (mAbs) will play in LDL cholesterol management.

RECENT FINDINGS

The discovery of PCSK9 in 2003 and its association with a rare form of autosomal-dominant hypercholesterolemia quickly led to the understanding of the role of circulating PCSK9 in regulating the recycling of the LDL receptor and LDL cholesterol (LDL-C) and impact on cardiovascular disease. Development of monoclonal antibodies that bind and inhibit PCSK9 entered clinical development in late 2009 and demonstrated substantial LDL-C reductions as monotherapy, added to statins, in heterozygous familial hypercholesterolemia and patients intolerant of statins. Large and comprehensive trials over the last 5 years also indicated good tolerability and safety and resulted in the 2015 regulatory approval in the USA and Europe for the marketing of two mAbs, evolocumab and alirocumab, for the treatment of LDL-C.

SUMMARY

The background, clinical trials and approved indications for the current PCSK9 inhibitors are reviewed along with their likely role in the management of LDL-C and cardiovascular disease prevention.

Comparison of PCSK9 Inhibitor Evolocumab vs Ezetimibe in Statin-Intolerant Patients: Design of the Goal Achievement After Utilizing an Anti-PCSK9 Antibody in Statin-Intolerant Subjects 3 (GAUSS-3) Trial

Statins are the accepted standard for lowering low-density lipoprotein cholesterol (LDL-C). However, 5% to 10% of statin-treated patients report intolerance, mostly due to muscle-related adverse effects. Challenges exist to objective identification of statin-intolerant patients. Evolocumab is a monoclonal antibody that binds proprotein convertase subtilisin/kexin type 9 (PCSK9), resulting in marked LDL-C reduction. We report the design of Goal Achievement After Utilizing an Anti-PCSK9 Antibody in Statin-Intolerant Subjects 3 (GAUSS-3), a phase 3, multicenter, randomized, double-blind, ezetimibe-controlled study to compare effectiveness of 24 weeks of evolocumab 420 mg monthly vs ezetimibe 10 mg daily in hypercholesterolemic patients unable to tolerate an effective statin dose. The study incorporates a novel atorvastatin-controlled, double-blind, crossover phase to objectively identify statin intolerance. Eligible patients had LDL-C above the National Cholesterol Education Project Adult Treatment Panel III target level for the appropriate coronary heart disease risk category and were unable to tolerate ≥3 statins or 2 statins (one of which was atorvastatin ≤10 mg/d) or had a history of marked creatine kinase elevation accompanied by muscle symptoms while on 1 statin. This trial has 2 co-primary endpoints: mean percent change from baseline in LDL-C at weeks 22 and 24 and percent change from baseline in LDL-C at week 24. Key secondary efficacy endpoints include change from baseline in LDL-C, percent of patients attaining LDL-C <70 mg/dL (1.81 mmol/L), and percent change from baseline in total cholesterol, non-high-density lipoprotein cholesterol, and apolipoprotein B. Recruitment of 511 patients was completed on November 28, 2014.

Delayed emergence of methamphetamine's enhanced cardiovascular effects in nonhuman primates during protracted methamphetamine abstinence

BACKGROUND

Methamphetamine abuse is linked with brain abnormalities, but its peripheral effects constitute an integral aspect of long-term methamphetamine use.

METHODS

Eight male rhesus monkeys with long histories of intravenous methamphetamine self-administration were evaluated 1 day, and 1, 4, 12, 26, and 52 weeks after their last methamphetamine self-administration session. On test days, isoflurane-anesthetized animals received a 0.35 mg/kg IV methamphetamine challenge. A control group consisted of 10 age and gender matched drug naïve monkeys. Cardiovascular responses to methamphetamine were followed for 2.5h. Echocardiograms were acquired at 3 and 12 months of abstinence and in the control animals.

RESULTS

No pre-methamphetamine baseline differences existed among 7 physiological measures across all conditions and controls. As expected, methamphetamine increased heart rate and blood pressure in controls. However, immediately following the self-administration period, the blood pressure response to methamphetamine challenge was reduced when compared to control monkeys. The peak and 150-min average heart rate increases, as well as peak blood pressure increases following methamphetamine were significantly elevated between weeks 12 to 26 of abstinence. These data indicate the development of tolerance followed by sensitization to methamphetamine cardiovascular effects. Echocardiography demonstrated decreased left ventricular ejection fraction and cardiac output at 3 months of abstinence. Importantly, both cardiovascular sensitization and cardiotoxicity appeared to be reversible as they returned toward control group levels after 1 year of abstinence.

CONCLUSIONS

Enhanced cardiovascular effects may occur after prolonged abstinence in addicts relapsing to methamphetamine and may underlie clinically reported acute cardiotoxic events.

Efficacy and safety of evolocumab in reducing lipids and cardiovascular events

BACKGROUND

Evolocumab, a monoclonal antibody that inhibits proprotein convertase subtilisin-kexin type 9 (PCSK9), significantly reduced low-density lipoprotein (LDL) cholesterol levels in short-term studies. We conducted two extension studies to obtain longer-term data.

METHODS

In two open-label, randomized trials, we enrolled 4465 patients who had completed 1 of 12 phase 2 or 3 studies ("parent trials") of evolocumab. Regardless of study-group assignments in the parent trials, eligible patients were randomly assigned in a 2:1 ratio to receive either evolocumab (140 mg every 2 weeks or 420 mg monthly) plus standard therapy or standard therapy alone. Patients were followed for a median of 11.1 months with assessment of lipid levels, safety, and (as a prespecified exploratory analysis) adjudicated cardiovascular events including death, myocardial infarction, unstable angina, coronary revascularization, stroke, transient ischemic attack, and heart failure. Data from the two trials were combined.

RESULTS

As compared with standard therapy alone, evolocumab reduced the level of LDL cholesterol by 61%, from a median of 120 mg per deciliter to 48 mg per deciliter (P<0.001). Most adverse events occurred with similar frequency in the two groups, although neurocognitive events were reported more frequently in the evolocumab group. The risk of adverse events, including neurocognitive events, did not vary significantly according to the achieved level of LDL cholesterol. The rate of cardiovascular events at 1 year was reduced from 2.18% in the standard-therapy group to 0.95% in the evolocumab group (hazard ratio in the evolocumab group, 0.47; 95% confidence interval, 0.28 to 0.78; P=0.003).

CONCLUSIONS

During approximately 1 year of therapy, the use of evolocumab plus standard therapy, as compared with standard therapy alone, significantly reduced LDL cholesterol levels and reduced the incidence of cardiovascular events in a prespecified but exploratory analysis. (Funded by Amgen; OSLER-1 and OSLER-2 ClinicalTrials.gov numbers, NCT01439880 and NCT01854918.).

PCSK9 inhibition with evolocumab (AMG 145) in heterozygous familial hypercholesterolaemia (RUTHERFORD-2): a randomised, double-blind, placebo-controlled trial

BACKGROUND

Heterozygous familial hypercholesterolaemia is characterised by low cellular uptake of LDL cholesterol, increased plasma LDL cholesterol concentrations, and premature cardiovascular disease. Despite intensive statin therapy, with or without ezetimibe, many patients are unable to achieve recommended target levels of LDL cholesterol. We investigated the effect of PCSK9 inhibition with evolocumab (AMG 145) on LDL cholesterol in patients with this disorder.

METHODS

This multicentre, randomised, double-blind, placebo-controlled trial was undertaken at 39 sites (most of which were specialised lipid clinics, mainly attached to academic institutions) in Australia, Asia, Europe, New Zealand, North America, and South Africa between Feb 7 and Dec 19, 2013. 331 eligible patients (18-80 years of age), who met clinical criteria for heterozygous familial hypercholesterolaemia and were on stable lipid-lowering therapy for at least 4 weeks, with a fasting LDL cholesterol concentration of 2·6 mmol/L or higher, were randomly allocated in a 2:2:1:1 ratio to receive subcutaneous evolocumab 140 mg every 2 weeks, evolocumab 420 mg monthly, or subcutaneous placebo every 2 weeks or monthly for 12 weeks. Randomisation was computer generated by the study sponsor, implemented by a computerised voice interactive system, and stratified by LDL cholesterol concentration at screening (higher or lower than 4·1 mmol/L) and by baseline ezetimibe use (yes/no). Patients, study personnel, investigators, and Amgen study staff were masked to treatment assignments within dosing frequency groups. The coprimary endpoints were percentage change from baseline in LDL cholesterol at week 12 and at the mean of weeks 10 and 12, analysed by intention-to-treat. This trial is registered with ClinicalTrials.gov, number NCT01763918.

FINDINGS

Of 415 screened patients, 331 were eligible and were randomly assigned to the four treatment groups: evolocumab 140 mg every 2 weeks (n=111), evolocumab 420 mg monthly (n=110), placebo every 2 weeks (n=55), or placebo monthly (n=55). 329 patients received at least one dose of study drug. Compared with placebo, evolocumab at both dosing schedules led to a significant reduction in mean LDL cholesterol at week 12 (every-2-weeks dose: 59·2% reduction [95% CI 53·4-65·1], monthly dose: 61·3% reduction [53·6-69·0]; both p<0·0001) and at the mean of weeks 10 and 12 (60·2% reduction [95% CI 54·5-65·8] and 65·6% reduction [59·8-71·3]; both p<0·0001). Evolocumab was well tolerated, with rates of adverse events similar to placebo. The most common adverse events occurring more frequently in the evolocumab-treated patients than in the placebo groups were nasopharyngitis (in 19 patients [9%] vs five [5%] in the placebo group) and muscle-related adverse events (ten patients [5%] vs 1 [1%]).

INTERPRETATION

In patients with heterozygous familial hypercholesterolaemia, evolocumab administered either 140 mg every 2 weeks or 420 mg monthly was well tolerated and yielded similar and rapid 60% reductions in LDL cholesterol compared with placebo.

FUNDING

Amgen Inc.

Inhibition of PCSK9 with evolocumab in homozygous familial hypercholesterolaemia (TESLA Part B): a randomised, double-blind, placebo-controlled trial

BACKGROUND

Homozygous familial hypercholesterolaemia is a rare, serious disorder caused by very low or absent plasma clearance of LDL, substantially raised LDL cholesterol, and accelerated development of cardiovascular disease. Conventional lipid-lowering treatments are modestly effective. Evolocumab, a monoclonal antibody to proprotein convertase subtilisin/kexin type 9 (PCSK9), reduced LDL cholesterol by 16% in a pilot study. We now report results with evolocumab in a randomised, double-blind, placebo-controlled phase 3 trial.

METHODS

This randomised, double-blind, placebo-controlled phase 3 trial was undertaken at 17 sites in ten countries in North America, Europe, the Middle East, and South Africa. 50 eligible patients (aged ≥12 years) with homozygous familial hypercholesterolaemia, on stable lipid-regulating therapy for at least 4 weeks, and not receiving lipoprotein apheresis, were randomly allocated by a computer-generated randomisation sequence in a 2:1 ratio to receive subcutaneous evolocumab 420 mg or placebo every 4 weeks for 12 weeks. Randomisation was stratified by LDL cholesterol at screening (<11 mmol/L or ≥11 mmol/L) and implemented by a computerised interactive voice-response system. Patients, study personnel, and the funder were masked to treatment and to the efficacy results by the central laboratory not returning LDL cholesterol or any lipid results to the clinical sites after the baseline visit. The primary endpoint was percentage change in ultracentrifugation LDL cholesterol from baseline at week 12 compared with placebo, analysed by intention-to-treat. This trial is registered with ClinicalTrials.gov, number NCT01588496.

FINDINGS

Of the 50 eligible patients randomly assigned to the two treatment groups, 49 actually received the study drug and completed the study (16 in the placebo group and 33 in the evolocumab group). Compared with placebo, evolocumab significantly reduced ultracentrifugation LDL cholesterol at 12 weeks by 30·9% (95% CI -43·9% to -18·0%; p<0·0001). Treatment-emergent adverse events occurred in ten (63%) of 16 patients in the placebo group and 12 (36%) of 33 in the evolocumab group. No serious clinical or laboratory adverse events occurred, and no anti-evolocumab antibody development was detected during the study.

INTERPRETATION

In patients with homozygous familial hypercholesterolaemia receiving stable background lipid-lowering treatment and not on apheresis, evolocumab 420 mg administered every 4 weeks was well tolerated and significantly reduced LDL cholesterol compared with placebo.

FUNDING

Amgen Inc.

New therapies for reducing low-density lipoprotein cholesterol

Although the past 4 decades have been the most productive in transitioning from an low-density lipoprotein cholesterol (LDL-C) hypothesis to demonstration of clinical benefit, cardiovascular disease remains a major cause of mortality and morbidity. It is fortunate that most of the effective lipid-lowering drugs, the statins, have become generic and inexpensive. However, there remains a large unmet medical need for new and effective agents that are also well tolerated and safe, especially for patients unable to either tolerate statins or achieve optimal LDL-C on current therapies. It is likely that the agents discussed in this review will fill that need.

Reduction of low-density lipoprotein cholesterol by monoclonal antibody inhibition of PCSK9

Published phase I and II trials with two fully human monoclonal antibodies to PCSK9 have provided comprehensive evidence that inhibiting PCSK9 is a very effective method to reduce low-density lipoprotein cholesterol (LDL-C). In all populations studied so far, whether on statins or LDL-C-reducing diet alone, with or without a genetic defect in the LDL receptor, and in subjects intolerant to statins, the LDL-C reductions have been large and consistent. Even the most efficacious statin, rosuvastatin, at its highest dose has not achieved such reductions. The clinical trials have established that monoclonal antibody therapy targeted to PCSK9 may be administered subcutaneously every two or four weeks. Current data suggest these drugs will provide an effective therapeutic option for LDL-C reduction and that, if proven safe in phase III trials, they will be as important to LDL-C control, and likely to cardiovascular disease risk reduction, as statins have been over the past three decades.

Targeting LDL: is lower better and is it safe?

Low density lipoprotein cholesterol (LDL-C) is one of the most validated targets in clinical medicine. Large randomized, outcome trials have demonstrated a clear relationship between reducing LDL-C and cardiovascular disease (CVD) risk, which has been maintained to LDL-C levels of <1.8 mmol/L. To assess the benefit of even lower LDL-C it is important to recognize that CVD risk reduction is related to absolute reduction in LDL-C, not to percent change. Furthermore measurement of LDL-C is also critical as recent studies show the Friedewald calculation significantly underestimates true LDL-C values <1.8 mmol/L, distorting the relationship with CVD risk reduction. Discussion of potential harm from low, or lower, LDL-C has centered on cancer, hemorrhagic stroke, and violent death, but there is little evidence from outcome trials to show a relationship with low LDL-C. Proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors which will reduce LDL-C well below 1.3 mmol/L, will likely provide the clearest answer to both the question of efficacy and safety of low LDL-C within the next few years.

A 52-week placebo-controlled trial of evolocumab in hyperlipidemia

BACKGROUND

Evolocumab, a monoclonal antibody that inhibits proprotein convertase subtilisin/kexin type 9 (PCSK9), significantly reduced low-density lipoprotein (LDL) cholesterol levels in phase 2 studies. We conducted a phase 3 trial to evaluate the safety and efficacy of 52 weeks of treatment with evolocumab.

METHODS

We stratified patients with hyperlipidemia according to the risk categories outlined by the Adult Treatment Panel III of the National Cholesterol Education Program. On the basis of this classification, patients were started on background lipid-lowering therapy with diet alone or diet plus atorvastatin at a dose of 10 mg daily, atorvastatin at a dose of 80 mg daily, or atorvastatin at a dose of 80 mg daily plus ezetimibe at a dose of 10 mg daily, for a run-in period of 4 to 12 weeks. Patients with an LDL cholesterol level of 75 mg per deciliter (1.9 mmol per liter) or higher were then randomly assigned in a 2:1 ratio to receive either evolocumab (420 mg) or placebo every 4 weeks. The primary end point was the percent change from baseline in LDL cholesterol, as measured by means of ultracentrifugation, at week 52.

RESULTS

Among the 901 patients included in the primary analysis, the overall least-squares mean (±SE) reduction in LDL cholesterol from baseline in the evolocumab group, taking into account the change in the placebo group, was 57.0±2.1% (P<0.001). The mean reduction was 55.7±4.2% among patients who underwent background therapy with diet alone, 61.6±2.6% among those who received 10 mg of atorvastatin, 56.8±5.3% among those who received 80 mg of atorvastatin, and 48.5±5.2% among those who received a combination of 80 mg of atorvastatin and 10 mg of ezetimibe (P<0.001 for all comparisons). Evolocumab treatment also significantly reduced levels of apolipoprotein B, non-high-density lipoprotein cholesterol, lipoprotein(a), and triglycerides. The most common adverse events were nasopharyngitis, upper respiratory tract infection, influenza, and back pain.

CONCLUSIONS

At 52 weeks, evolocumab added to diet alone, to low-dose atorvastatin, or to high-dose atorvastatin with or without ezetimibe significantly reduced LDL cholesterol levels in patients with a range of cardiovascular risks. (Funded by Amgen; DESCARTES ClinicalTrials.gov number, NCT01516879.).

Low-density lipoprotein cholesterol reduction by inhibition of PCSK9

PURPOSE OF REVIEW

To review the phase 1 and 2 trials with fully human monoclonal antibodies to proprotein convertase subtilisin/kexin type 9 published in the last 18 months and provide comprehensive data that targeting proprotein convertase subtilisin/kexin type 9 very effectively reduces LDL-cholesterol (LDL-C).

RECENT FINDINGS

The trials studied a number of different populations including patients with LDL receptor defects (heterozygous familial hypercholesterolemia) and non-familial hypercholesterolemia, background statin or diet only treatment, and those intolerant to statins. The LDL-C lowering has been large, consistent and greater than the largest reductions achievable by the most efficacious statins. These subcutaneously administered drugs produce very rapid reductions in LDL-C, maximal in 7 days, with dosing frequency that may be every 2 or 4 weeks. Unexpected, consistent and robust reductions in Lp(a) have also been reported. Based on these short-term trials of 8-12 weeks in over 1500 patients the drugs have been very well tolerated and the emergent safety profile has not identified any specific areas of concern.

SUMMARY

Provided these compounds continue to exhibit an acceptable safety profile in ongoing phase 3 trials they will be as crucial to LDL-C control and reduction of cardiovascular disease, as statins.

Effect of the proprotein convertase subtilisin/kexin 9 monoclonal antibody, AMG 145, in homozygous familial hypercholesterolemia

BACKGROUND

Homozygous familial hypercholesterolemia is a rare, serious disorder with a substantial reduction in low-density lipoprotein (LDL) receptor function, severely elevated LDL cholesterol, cardiovascular disease, and often death in childhood. Response to conventional drug therapies is modest. Monoclonal antibodies to proprotein convertase subtilisin/kexin 9 (PCSK9) reduce LDL cholesterol in heterozygous familial hypercholesterolemia. The effect in homozygous familial hypercholesterolemia is unknown and uncertain. We evaluated the efficacy and safety of AMG 145 in an open-label, single-arm, multicenter, dose-scheduling pilot study in patients with homozygous familial hypercholesterolemia.

METHODS AND RESULTS

Eight patients with LDL receptor-negative or -defective homozygous familial hypercholesterolemia on stable drug therapy were treated with subcutaneous 420 mg AMG 145 every 4 weeks for ≥12 weeks, followed by 420 mg AMG 145 every 2 weeks for an additional 12 weeks. All patients completed both treatment periods. Mean change from baseline in LDL cholesterol at week 12 was -16.5% (range, 5.2% to -43.6%; P=0.0781) and -13.9% (range, 39.9% to -43.3%; P=0.1484) with 4- and 2-week dosing, respectively. No reduction was seen in the 2 receptor-negative patients. Over the treatment periods, mean±SD LDL cholesterol reductions in the 6 LDL receptor-defective patients were 19.3±16% and 26.3±20% with 4- and 2-week dosing, respectively (P=0.0313 for both values), ranging from 4% to 48% with 2-week dosing. No serious side effects were reported.

CONCLUSION

This study demonstrates significant and dose-related LDL cholesterol lowering with a PCSK9 monoclonal antibody in homozygous familial hypercholesterolemia patients with defective LDL receptor activity but no reduction in those who were receptor negative.