John Kastelein: Latest Therapeutics in CVD, APOE’s Role in Alzheimer’s disease, Familial Hypercholesterolemia

Familial Hypercholesterolemia (FH)

• Autosomal dominant genetic disease 
  • Not sex-​​linked
  • Only need one parent to have it
  • Almost 100% penetrant (if you have a robust mutation in one of the genes that cause FH, you’re almost certain to get the phenotype)
• Phenotype starts early in life 
  • Cholesterol deposits on tendons and in the eye
  • First serious manifestation often angina or heart attack
  • Dangerous due to soft, cholesterol-​​rich plaque in coronary arteries
• Diagnosis based on: 
  • Family history of premature coronary disease
  • Elevated LDL cholesterol without other abnormalities
  • Elevated LDL in first-​​degree relatives
• Over 3,500 different mutations can cause FH
• LDL cut off of 190 milligrams per deciliter used for diagnosis
  Lipid Clinic and Referral Bias
• Initial patients had LDLs of 300 or more
• Genotype determination requires accurate diagnosis

Diagnosing Familial Hypercholesterolemia (FH) in Children 

• High cholesterol in children likely due to FH
• Excluding other causes and looking at family history helps confirm diagnosis
• 95% of cases have a mutation found through screening
• Majority of mutations are in the LDL receptor, followed by epob and PCSK Nine

Mutations in LDL Receptor, Apob, and PCSK Nine 

• Mutations in these genes are prevalent in the general population
• FH is the most frequent autosomal dominant disorder in men
• Increased plant sterols in circulation can indicate mutations in ABCG five, G eight
• Cytosterolemia may be more frequent than originally thought

Physical Signs of FH 

• Tendon xanthomas and cholesterol deposits in extensor tendons and Achilles tendon
• Deposits in the eyes (arcus cornealis) due to movement and blinking
• Diagnosis can sometimes be made by observing these physical signs

Diagnosis of FH 

• Clinical manifestations not required for diagnosis, but can help confirm it
• Accurate diagnosis is crucial for determining genotype and appropriate treatment
  Understanding Familial Hypercholesterolemia (FH)
• 5% of people with FH do not develop premature ASCVD (atherosclerotic cardiovascular disease) 
  • Majority of these are women
  • Possible explanations for this immunity: 
    • Efficient reverse cholesterol transport system
    • High HDL cholesterol levels
    • Non-​​smokers
    • Rarely have diabetes
    • Thin and active lifestyle
  • No clear genetic reason found for this resistance against LDL cholesterol
• Dutch Lipid Clinic Criteria for diagnosing FH 
  • Internally and externally validated
  • Points-​​based system 
    • Family history, physical signs, and genetic mutations contribute to the score
  • Categories: Definite FH, Probable FH, Possible FH, and Unlikely FH
  • Treatment for definite FH starts as early as age 6
• Monozygotic twins with FH 
  • No specific study mentioned, but a large monozygotic twin cohort exists in Amsterdam
  • Studying differences in progression as a function of lifestyle factors could provide insights into the role of behavior in FH outcomes
    FH (Familial Hypercholesterolemia) Treatment
• Treatment varies based on age, sex, and level of disease at the time of diagnosis
• Primary prevention: treatment when there is not a single discernible sign of disease
• Secondary prevention: treatment when there are abnormalities on a CTA or calcium score

Children

• Start with a healthy lifestyle early on 
  • Anti-​​smoking training
  • Dietary counseling for healthy choices
  • Physical exercise
• Start with a statin at the age of six 
  • Pravastatin, Rosuvastatin, or Atorvastatin
  • Goal is to have an LDL below 130
• PCSK9 inhibitors may be considered, but there is debate due to potential effects on brain development

Adults

• Treatment as aggressive as guidelines for non-​​FH patients
• For heterozygous FH: 
  • Statins, PCSK9 inhibitors, and Ezetimibe
  • Strive for the lowest LDL possible
• For homozygous FH: 
  • High-​​dose statin, Ezetimibe, Evolocumab (PCSK9 inhibitor), and Evinacumab (ANGPTL3 monoclonal antibody)
  • Aim for relatively normal LDL levels
• Severe heterozygous FH: patients who don’t reach reasonable LDL levels with triple therapy (statin, PCSK9 inhibitor, and Ezetimibe)
  Opposition to LDL Cholesterol Therapy
• Some people argue that LDL cholesterol is not causally related to ASCVD or only related in the context of metabolic illness
• However, genetic diseases like FH are often modified by environmental and genetic factors
• The argument is similar to the fact that some people smoke their whole lives and don’t get lung cancer, while others never smoke and do get lung cancer
• Neither of these facts diminish the causal case for smoking and lung cancer

CTEP Inhibitors

• CTEP is a protein that grabs a cholesterol ester molecule from HDL and transfers it to LDL
• In the past, this was beneficial for conserving cholesterol and energy
• However, in modern times, adding cholesterol to LDL is not a good idea
• Mendelian randomization studies show that people with high CTEP activity have more heart disease, heart failure, kidney disease, diabetes, and Alzheimer’s
• Pfizer developed a CTEP inhibitor called Torcetrapib, but it had negative side effects and was ultimately a failure
• The failure of Torcetrapib led to a better understanding of the drug’s off-​​target effects and the need for a more effective CTEP inhibitor

Vioxx

• Vioxx was a drug that was removed from the market due to safety concerns
• However, some argue that it should not have been removed, but instead required more work to determine who the susceptible individuals were
  Vioxx and Big Pharma
• Vioxx: a potent Cox‑2 inhibitor, superior to Celebrex
• Merck, the company that made Vioxx, faced controversy due to side effects
• Big pharma often has a negative reputation, sometimes deservedly so

HDL Hypothesis and CTEP Inhibitors

• Roche’s Dulcetrapib raised HDL by 30% but had no effect on cardiovascular outcomes
• This ended the HDL hypothesis
• Merck’s Anacetrapib lowered LDL by 17% and had a 9% reduction in Mace
• CTEP inhibition lowers heart attacks by virtue of its LDL lowering

Thrifty Gene Hypothesis

• Explains why people in Asia get type 2 diabetes at a lower BMI than Caucasians
• Also explains why high LDL may have been advantageous during the Ice Age
• FH mice are more resistant to bacterial infection than non-​​FH mice

Obacibatrib

• Found at Mitsubishi, a potent CTEP inhibitor
• Lowers LDL by 50% on top of high-​​intensity statins
• Increases HDL by 165%
• Being studied for effects on Alzheimer’s, age-​​related macular degeneration, septicemia, and diabetes

Lipoprotein Metabolism and CTEP Inhibition

• Inhibiting CTP changes lipoprotein metabolism
• Forces the liver to produce more ApoA1, which is beneficial for cholesterol export
• Produces more pre-​​beta HDL particles that remove cholesterol from peripheral tissues
• All four CTP inhibitors showed less diabetes in treatment arms than placebo arms in outcome trials
  LDL Reduction and CTP Inhibition
• LDLs can be lowered by 50% due to liver upregulation of LDL receptors
• Large HDLs take APOE on board, which is also a ligand for LDL receptors 
  • Large HDL particles cleared by the liver
  • New equilibrium between removal of lipoproteins by the liver and production of small HDL particles
• CTP inhibition required to be about 90% to achieve these effects

CTP Inhibition and Protection Against Septicemia 

• Loss of function variant in CTP provides better protection against septicemia 
  • Likely due to HDL particles functioning as a sink for endotoxins
  • High HDL during septicemia is beneficial
• CTP inhibition prevents the drop in HDL cholesterol during septicemia

CTP Inhibition and Diabetes 

• Raising HDL with CTP inhibition protects against diabetes 
  • Believed to protect the bronchios against apoptosis
  • Effect of about 16–20% in new onset type 2 diabetes between placebo and active treatment arm

Obacetrapib: A Promising CTP Inhibitor 

• Completed Phase 1 and Phase 2 trials with no toxicity and good tolerability
• Lowers LDL by half, making it as potent as injectable treatments
• Cheap to produce, making it a potential alternative to statins

Phase 3 Trials 

• Broadway: 2400 patients, one year, secondary prevention in high-​​risk patients 
  • Not powered for Mace, but looking for a trend in the right direction
• Brooklyn: 300 patients, heterozygous FH
• Prevail: 9000 patients, secondary prevention in high-​​risk patients 
  • Baseline LDL around 100, aiming for a 20% mace reduction
    PCSK9 Inhibitors and LDL Cholesterol
• PCSK9 inhibitors believed to be safe and effective in lowering LDL cholesterol
• Trial conducted on patients with average LDL cholesterol of 70 mg/​​dL
• Study halted at 3.2 years, showing significant results

Prevail Trial

• Involves patients with higher LDL cholesterol levels
• Baseline LDL around 100 mg/​​dL
• Aiming for a median follow-​​up of 3.5 to 4 years

Side Effects and Safety 

• Bempedoic acid, ezetimibe, obeticholic acid, and PCSK9 inhibitors have minimal to no side effects
• Statins have side effects, but less common than perceived

LP(a) Reduction

• Obeticholic acid reduces LP(a) by 56%
• More effective than PCSK9 inhibitors in reducing LP(a)
• Connection between LP(a) lowering and LDL lowering not yet understood

Mendelian Randomization and CTEP Hypofunction 

• Hypofunctioning CTEP associated with longer life, less heart disease, Alzheimer’s, diabetes, heart failure, and renal disease
• Reduction in blood pressure and hemoglobin A1C also observed
• No clear explanation for blood pressure reduction

APOE4 and Alzheimer’s Disease 

• APOE4 carriers have a higher risk of Alzheimer’s due to inefficient cholesterol transport in the brain
• Accumulation of sterols in neurons leads to oxidation and cell death
• APOA1 protein can help by taking over the functions of APOE4
  EPOA1 and the Brain
• EPOA1 can get through the blood-​​brain barrier due to its small size and a specific receptor that pushes it through brain cells
• CETP inhibitors raise EPOA1 substantially in circulation
• Large HDLs acquire EPOE and lose their EPOA1
• Increasing EPOA1 concentration in circulation can push it into the brain, taking over the function of dysfunctional EPOE4

APOE4 Gene and Protein

• APOE4 gene has three isoforms: 2, 3, and 4
• APOE4 protein differs in one amino acid from the wild type, changing its three-​​dimensional confirmation and making it a poor cholesterol acceptor and transporter
• Carrying an E4 gene has numerous negative effects on the brain, including pro-​​inflammatory properties, insufficient lipoprotein metabolism, and no longer being a chaperone for beta-amyloid

APOE in Cardiovascular Disease

• APOE4 is associated with higher LDL, a more pro-​​inflammatory state, and more heart disease
• APOE4 is a better ligand for the LDL receptor, especially on remnants and VLDL
• This leads to downregulation of the LDL receptor and increased LDL levels
• APOE4 carriership is also associated with a chronic pro-​​inflammatory state

APOE4 Risk Factors

• APOE4 risk factors are not deterministic and are less penetrant than familial hypercholesterolemia (FH)
• Many people with APOE4 do not develop Alzheimer’s disease, and a third of people with Alzheimer’s do not have APOE4
• Raising ApoA1 levels may help offset the damage of a defective APOE in response to APOE4
• Preclinical and early clinical work is being done to determine the potential benefit and effect size of raising ApoA1 levels in the brain
  CTEP Inhibitors and HDL Hypothesis
• CTEP inhibitors have been criticized for the past 15 years 
  • Criticism based on the HDL hypothesis and Mendelian Randomization
  • However, this may have created a blind spot in understanding the biology of CTEP
• CTEP is a longevity gene 
  • Hypofunctioning variant is as much a longevity gene as the hypofunctioning PCSK9
• Obasetrib may redeem the field and provide excitement in clinical practice

CTP Activity and Coronary Disease

• High CTP activity linked to worse progression of coronary disease in a two-​​year trial 
  • Since then, the goal has been to find an inhibitor that works without side effects

Lessons from CTEP Inhibitor Trials

• The field lost its way due to the wrong biomarker (HDL‑C)
  • Initial insight in biology was correct, but the wrong biomarker led to 15 years and billions of dollars wasted
  • Lives were lost during clinical trials
• Current approach:
  • Strong Mendelian Randomization evidence
  • Phase 1 and Phase 2 trials to show no bizarre side effects
  • Gently proceed to Phase 3 with a DSMB

Upcoming Data on Alzheimer’s

• Data on Alzheimer’s expected in the summer 
  • Aim to understand what’s happening in the brain