#384 - Special episode — Obicetrapib: The CETP inhibitor with cardiovascular benefits and potential Alzheimer's prevention
Peter Attia discusses obicetrapib, an investigational CETP inhibitor, exploring its history, how it lowers LDL and Lp(a), and its potential cardiovascular benefits. He also delves into emerging data suggesting implications for Alzheimer's disease, particularly in APOE4 carriers, based on biomarker changes.
Deep Dive Analysis
17 Topic Outline
Introducing Obicetrapib: A Revived Drug Class
Understanding CETP Biology and Lipoproteins
Reverse Cholesterol Transport: Direct and Indirect Pathways
The Role of CETP in Lipid Exchange
History of Failed CETP Inhibitors
Why Obicetrapib May Succeed
Obicetrapib's Impact on Lipids: Phase 2 and 3 Trials
Broadway Trial Results: LDL, ApoB, HDL, Lp(a) Effects
Lp(a) Reduction and Metabolic Profile
Obicetrapib Approval Process: Europe vs. US
Brain Lipid Metabolism and APOE4 Genetics
APOE4's Impact on Brain Cholesterol Transport
How CETP Inhibition May Benefit APOE4 Carriers
Broadway Alzheimer's Biomarker Substudy Design
Key Findings from Broadway Alzheimer's Substudy
Interpreting Obicetrapib's Alzheimer's Biomarker Results
Overall Optimism for Obicetrapib's Future
7 Key Concepts
CETP (Cholesterol Ester Transfer Protein)
CETP is a molecular shuttle protein that exchanges cholesterol esters from HDL for triglycerides in ApoB-containing particles like LDL. Inhibiting CETP leads to larger, cholesterol-rich HDL particles and smaller, cholesterol-poor LDL particles, thereby increasing HDL-C and decreasing LDL-C.
Reverse Cholesterol Transport (RCT)
RCT is the process by which cholesterol is moved from peripheral tissues back to the liver. While historically viewed as solely HDL-mediated, a significant portion (40-50%) occurs indirectly, where HDL exchanges cholesterol esters with ApoB-containing particles (like LDL), which then transport the cholesterol back to the liver.
ApoB Lipoproteins
ApoB lipoproteins are a class of particles, including VLDL, IDL, and LDL, characterized by the ApoB protein. These lipoproteins are responsible for transporting cholesterol from the liver to peripheral tissues and are causally linked to the development of atherosclerosis.
ApoA1 Lipoproteins (HDL)
ApoA1 lipoproteins, primarily High-Density Lipoproteins (HDL), are characterized by the ApoA1 protein. They play a role in reverse cholesterol transport by accepting excess cholesterol from peripheral cells and returning it to the liver, either directly or indirectly via exchange with ApoB particles.
APOE (Apolipoprotein E)
APOE is a protein crucial for cholesterol transport within the brain, synthesized by astrocytes and microglia. It organizes lipoproteins that shuttle cholesterol and phospholipids to neurons, supporting membrane repair, synaptic remodeling, and overall lipid homeostasis in the central nervous system.
APOE4 Allele
The APOE4 allele is a genetic variant that produces an ApoE protein less efficient at lipidating and transporting cholesterol in the brain. Individuals with one or two copies of APOE4 face an increased risk for Alzheimer's disease due to impaired lipid trafficking, increased oxidative stress, and less efficient amyloid clearance, contributing to neuronal dysfunction.
P-tau-217 (Phosphorylated tau 217)
P-tau-217 is a plasma biomarker for Alzheimer's disease, considered highly correlated with tau pathology seen on PET scans and clinical outcomes. Its levels are believed to reflect the progression of Alzheimer's pathology in the brain.
10 Questions Answered
Obicetrapib is a CETP inhibitor drug primarily investigated for its ability to reduce LDL cholesterol and ApoB, but it's also generating excitement due to emerging data suggesting potential implications for Alzheimer's disease, particularly in APOE4 carriers.
CETP inhibitors block the cholesterol ester transfer protein, which normally exchanges cholesterol esters from HDL for triglycerides in LDL. This inhibition leads to less cholesterol ester leaving HDL, resulting in larger, cholesterol-rich HDL particles (increasing HDL-C) and lower LDL-C and ApoB.
Early CETP inhibitors like torcetrapib, dalcetrapib, and evacetrapib failed either due to off-target toxicities (e.g., torcetrapib raising blood pressure) or because they did not sufficiently lower LDL cholesterol and ApoB, which Mendelian randomizations later showed to be the causal factor for cardiovascular risk, not just high HDL.
Obicetrapib has not shown off-target toxicities and has demonstrated a robust ability to significantly reduce LDL cholesterol and ApoB, even when added to maximum lipid-lowering therapy, addressing the key shortcomings of its predecessors.
Obicetrapib has been shown to reduce Lp(a) by about one-third, which is significant because Lp(a) is an independent and genetically determined cardiovascular risk factor that is notoriously difficult to modify with existing therapies.
The brain operates a semi-independent lipid management system behind the blood-brain barrier, relying on its own lipoproteins organized around apolipoprotein E (ApoE) to shuttle cholesterol and phospholipids to neurons, rather than circulating ApoB or ApoA1 lipoproteins.
The APOE4 gene produces an ApoE protein that is less efficient at lipidating and transporting cholesterol in the brain, leading to impaired lipid trafficking, increased oxidative stress, and less efficient amyloid clearance. This dysfunction contributes to synaptic dysfunction and neuronal death, increasing the risk and accelerating the onset of Alzheimer's disease.
Small, lipid-poor HDL particles containing ApoA1 can cross the blood-brain barrier in limited amounts. By increasing the circulating pool of ApoA1, Obicetrapib could augment cholesterol efflux within the CNS, potentially offsetting the impaired lipid trafficking caused by the APOE4 protein, and also deliver antioxidants.
The substudy showed that Obicetrapib significantly attenuated the increase in plasma P-tau-217 (a key Alzheimer's biomarker) over 12 months across all participants. The effect was even more pronounced in APOE4 carriers, particularly in the small subset of E4/E4 individuals, where P-tau-217 actually decreased.
Obicetrapib's data is sufficient for approval in Europe, where it is expected to be on the market in Q4 2026. In the US, approval will require hard cardiovascular outcome data (mortality or MACE reduction) from the PREVAIL trial, meaning it will likely lag Europe by a couple of years.
3 Actionable Insights
1. Re-evaluate High HDL Cholesterol
Do not assume high HDL cholesterol levels guarantee cardiovascular safety, as Mendelian randomizations have not supported a causal link between high HDL and reduced cardiovascular disease outcomes. This challenges the common notion that high HDL is always ‘good cholesterol’.
2. Screen for SRB1 Mutations
If you have consistently very high HDL cholesterol (e.g., 110-120 mg/dL) and low LDL cholesterol, consider getting a calcium score. This can help rule out a loss-of-function SRB1 mutation, which can lead to high HDL but paradoxically increased coronary artery disease risk.
3. APOE4 Not Deterministic
While carrying one or two copies of the APOE4 gene increases the risk for Alzheimer’s disease, it is not deterministic. Many individuals with APOE4 genes live to advanced age without cognitive decline, indicating that other factors can significantly modify this genetic risk.
5 Key Quotes
I haven't been as excited about any drug in the market or a drug that's about to enter the market as I am with respect to this drug.
Peter Attia
The problem with cholesterol is it is not water soluble. So the fancy word for that is it is hydrophobic. And so something that is hydrophobic or something that repels water can't be transmitted through the blood because the blood is water.
Peter Attia
do not assume that because a person has high HDL cholesterol or low LDL cholesterol, that they're necessarily safe.
Peter Attia
The brain lives behind a paywall. We call it the blood-brain barrier.
Peter Attia
In my mind, you want people who are completely cognitively intact in mid-life or slightly older. So these are probably people in their 60s, maybe 70s, but again, completely cognitively intact, no evidence of MCI.
Peter Attia