As you know, Esperion is focused on developing and commercializing therapies for the treatment of patients with hypercholesterolemia who are not adequately controlled by currently available lipid-modifying therapies. Like any medical innovation, the journey of bempedoic acid started long before Esperion with the earliest identification of LDL-cholesterol (LDL-C) more than a century ago. So as National Cholesterol Education Month recently came to a close, we thought this would be an appropriate time to break down the history of LDL-C lowering.
Today, research and understanding of the treatment of elevated LDL-C is ongoing. To help us better understand our future, it’s always important to look at our past. So I sat down with Antonio M. Gotto, Jr., MD, DPhil, Dean Emeritus and Co-Chair of Board of Overseers, Weill Cornell Medical College, a man with decades of experience in the field, for a historical look back at the discovery and evolution of LDL-C and the therapies to lower it.
Tim Mayleben (Tim): Let’s start by speaking generally about LDL-cholesterol (LDL-C or low-density lipoprotein-cholesterol): what it is, when it was first discovered and when people realized it was important to the health of humans.
Dr. Antonio Gotto (Dr. Gotto): The discovery of cholesterol goes back over two hundred years, but in recent history – 1913 – Nikolay Anichkov caused arteriosclerotic vascular lesions in rabbits by feeding them purified cholesterol.
Lipoproteins were first described in 1929 by Michael Macheboeuf in his doctoral thesis. He separated a lipoprotein in fraction from horse plasma by ammonium sulfate precipitation. I believe the fractionation that he described was most likely HDL (high-density lipoprotein), but there weren’t any designations of high-density or low-density at that time.
To skip ahead to humans, the first real attention that was called to the relationship between high levels of cholesterol and early cardiovascular disease was in the 1930s by the Swedish physician Karl Müller, who observed his first patient with familial hypercholesterolemia, xanthomas and angina pectoris, in 1937. Xanthomas are visible deposits of lipids under the skin and are commonly seen in patients with familial hypercholesterolemia. He saw a number of patients like this over the next few months, and this really was the first solid evidence or observation that linked hypercholesterolemia as an important risk factor for heart disease.
Tim: How was familial hypercholesterolemia identified?
Dr. Gotto: Primarily through family history of heart disease associated with very high levels of cholesterol and xanthoma in affected family members. But when Müller published his observations in 1939, he still didn’t have LDL and HDL in the nomenclature; that came later.
A procedure called Cohn fractionation of plasma was used to isolate coagulation factors during the Second World War for wounded soldiers who needed transfusions. A researcher at Harvard, John Oncley, used Cohn fractionation and electrophoresis to separate the lipoproteins, and the initial classification was based on their migration with the globulins. And that’s why you had a fraction called beta lipoprotein that migrated with the beta globulins, alpha lipoprotein with the alpha globulins and a prebeta in front of the beta globulins.
It was John Gofman at University of California at Berkely who pioneered this technique of ultracentrifugation to separate the lipoproteins. This procedure was based on their flotation rate in salt solutions in the ultracentrifuge. The more lipid the fraction had, the faster it would float.
Gofman measured flotation coefficients. And that’s where the terminology “low-density” and “high-density” came from. It turned out that the high-density correlated with the alpha lipoproteins, the low-density correlated with the beta lipoproteins, and the very low density with the prebeta lipoproteins. That’s really how we got “Apo B” and “Apo A”, the proteins or apolipoproteins associated with each fraction.
Then Gofman made the observations that people who had higher levels of the beta lipoproteins, or the low-density lipoproteins, had more frequent coronary disease and ones with higher levels of the HDL had fewer coronary events.
Tim: Around what time was this when they made the association between low-density lipoproteins and coronary disease?
Dr. Gotto: Gofman started separating the lipoproteins with the ultracentrifuge in Berkeley soon after the Second World War in 1949, and then began publishing papers on his observations. Gofman was the first to describe the atherogenic potential of the LDL particles. And he also showed that, in patients with familial hypercholesterolemia, the cholesterol elevation was mainly in the LDL particle fraction.
Russ, Eder and Barr from New York Hospital-Cornell Medical Center used preparative ultracentrifugation to separate the lipoproteins in the 1950s. This involved using different strengths of salt solutions to separate the lipoprotein fractions. They also published that pre-menopausal women had a higher level of HDL-cholesterol than men did. But, it was Gofman who really was responsible for initially characterizing the lipoproteins as LDL, VLDL, and HDL.
Beginning in the 1960s, the Framingham Heart Study initially identified elevated cholesterol, elevated blood pressure and cigarette smoking as three major risk factors for coronary disease.
Tim: When they initiated the Framingham study, what was the objective? Was it simply to track these risk factors longitudinally in a population?
Dr. Gotto: It was observed that there was a high rate of coronary disease in the Framingham area, but it then turned out it wasn’t any higher than most other places. But it caused great alarm. One out of five people were dying of heart attacks.
So yes, it was a longitudinal study, and the investigators started following the risk factors. At the same time, began investigations about diet, dietary fat, cholesterol, and heart disease.
Ancel Keys did the Seven Countries Study in the 1960s which showed that people who had the highest percent of caloric intake from saturated fat had the highest level of cholesterol and highest rates of cardiovascular disease. Saturated fat was shown to be associated with increases in cholesterol and LDL-C. Dietary polyunsaturated fats reduced them, appeared to reduce LDL-C and coronary heart disease.
There was also a movement in the 1960s to do a national diet heart study – Jeremiah Stamler and others were pushing for that – but it was estimated it would cost over a billion dollars so it never got done.
Dr. Gotto: In 1965, Frederickson, Levy and Lees published three seminal papers in the New England Journal of Medicine which described a new classification system of the lipoprotein disorders. It was based on which fractions of lipoproteins were elevated. This classification used electrophoresis along with preparative ultracentrifugation to separate the lipoproteins; ultimately their approach led later on to the Friedewald equation for calculating LDL-C concentrations. This equation is still a standard method in use today.
In the 1970s, under the influence of Donald Fredrickson and Robert Levy, the NIH leaders, the Specialized Centers Of Research (SCOR) in arterioscleorosis, and the Lipid Research Clinics (LRC), the LRCs launched a study to test the LDL-C hypothesis, which was whether lowering elevated LDL-C led to a decrease in coronary events.
Tim: And what was the motivation for starting those clinics and the research centers?
Dr. Gotto: Cardiovascular disease was the number one cause of death and disability in the U.S. and in Europe.
Tim: And so it was perceived as a national health concern?
Dr. Gotto: Yes, these were the initiatives to address it. One of the first drugs that was shown to lower cholesterol was nicotinic acid in 1955. With the relationship between cholesterol and cardiovascular disease, the pharmaceutical industry became interested in developing a drug to block cholesterol or inhibit cholesterol synthesis. And so MER/29 (also known as triparanol) was developed and ultimately went on the market in 1960 for a little more than a year. It was pulled off the market because of toxicity, including cataracts.
Triparanol inhibited 24-dehydroxycholesterol reductase, which catalyzes the last step in cholesterol biosynthesis and there was an accumulation of desmosterol which was causal for the observed toxicities. At the time, that really frightened the pharmaceutical community and the medical community regarding the potential dangers of developing anything that inhibited cholesterol synthesis.
After a period of time the next class of drugs introduced were the fibrates. The first of these was clofibrate which was developed in the ‘60s and it was approved around 1970. It was called Atromid-S and Wyeth-Ayerst was the manufacturer.
Tim: And was that drug approved based on clinical trials that showed LDL-C lowering, or was there a requirement for an outcome study?
Dr. Gotto: At that time the FDA would approve a drug if it was safe and lowered LDL-C by 15 percent or more. This LDL-C became a surrogate for coronary heart disease.
Tim: And that was in the ‘70s that they did that?
Dr. Gotto: Yes, that was in the mid ‘70s.
A study called the Coronary Drug Project that tested four different ways of lowering cholesterol and reducing cardiovascular disease in male subjects.
One way was clofibrate; the second one was nicotinic acid; the third was dextrothyroxine; and the fourth one was estrogen. The estrogen arm was stopped early because the estrogen-treated patients increased thrombophlebitis, pulmonary embolism and death.
The dextrothyroxine was associated with cardiac arrhythmias and was also stopped early. And the other two were continued out to the end. There was nothing significant in the clofibrate arm. Total mortality was the main endpoint.
The nicotinic acid arm showed a decrease in non-fatal MIs, but did not decrease total mortality in that time frame so it was considered to be a failed trial initially. However, the investigators continued to follow the patients and did a post-trial analysis which showed that after 15 years, there was a statistically significant decrease in total mortality.
In the meantime, the resins were developed, also known as the bile acid sequestrants, and one of those, cholestyramine, was used for the Lipid Research Clinics Coronary Primary Prevention Trial.
Tim: And what year was that?
Dr. Gotto: Recruitment started in the 70’s. In the study, patients were supposed to take 24 grams of cholestyramine a day, and they averaged about 12 grams a day. And so when the study finally ended in 1983 and 1984, it showed that for every one percent decrease in cholesterol there was a two percent decrease in cardiovascular events, fatal and nonfatal MI. There was a statistically significant reduction in fatal and non-fatal myocardial infarctions in the group receiving cholestyramine. Approximately thirty-eight hundred patients were followed for seven years. There was a 19 percent reduction in CV events for a 10 percent reduction in LDL.
I happened to be president of the American Heart Association (AHA) at the time and cardiologists discounted the study because there was no reduction in total mortality. There was a non-significant increase in suicide, critics said, “Oh, they’re taking this terrible drug that’s lowering cholesterol but it is going to cause you to jump off bridges or out of windows.”
The study was positive in a one-sided, but not a two-sided way. So they never got an FDA indication for event reduction in cardiac events. This seems analogous to the current FDA failure to give an indication from the IMPROVE-IT trial.
The only indication, to this day, for cholestyramine is for lowering LDL-C as an adjunct to diet, and because of the NHLBI Type II study, FDA approved an angiographic trial, a claim for slowing of atherosclerosis.
Michael Oliver, from Edinburgh, led the WHO Cooperative Clofibrate Trial. This showed a reduction in the coronary events but an increase in total mortality. Clofibrate almost got pulled off the market – but, at that time, FDA just limited its use.
In the meantime, Warner Lambert developed the fibrate Lopid (gemfibrozil) which was used in the Helsinki Heart Study, and showed a significant decrease in CV morbidity and mortality. During the 1980s, Lopid was the number one lipid lowering drug sold in the United States and worldwide.
As a result of the Lipid Research Clinics Coronary Primary Prevention Trial, the NIH launched the National Cholesterol Education Program which led to cholesterol guidelines, the first of which was published in 1987.
NIH, AHA, ACC, and AHA were promoting benefits of reducing high LDL-cholesterol. Obviously the pharmaceutical companies were pushing it. And according to a man named Thomas Moore, in a book called “The Cholesterol Myth,” the “cholesterol mafia” was pushing it.
Tim: When did statins come into the picture?
Dr. Gotto: In 1974 George Popjak said what he was working on was an inhibitor of HMG-CoA reductase.
Tim: And so people already knew about HMG-CoA reductase as a potential enzyme target?
Dr. Gotto: Yes, they did. In 1964, Konrad Bloch got the Nobel Prize in Physiology or Medicine. He and others, including Popjak, worked on cholesterol biosynthesis and they knew that HMG-CoA reductase was the rate limiting step.
I met Akira Endo, the pioneer of statins, later on when he presented his work at the International Atherosclerosis Society symposium in Houston in 1979, which I chaired. Professor Endo presented his work there on compactin, the parent compound of the first marketed statins. Professor Endo hypothesized that anti-cholesterol agents are things that would inhibit cholesterol synthesis and would be made by micro-organisms to help protect them from other organisms trying to invade them.
He screened approximately 6,000 organisms and isolated compactin. The first patient they gave it to became so weak he couldn’t climb stairs. They reduced the dose and then started giving it to FH patients.
Sankyo did a clinical trial with compactin, and then suddenly Merck got interested in it. The two companies did some data sharing under an agreement that Roy Vagelos of Merck negotiated. In 1978, suddenly, Sankyo stopped development of compactin, and it was rumored that it was causing some type of intestinal lymphomas in dogs.
But nobody really ever found out the reason compactin was discontinued. Dr. Vagelos, head of Merck Research, made several trips to meet with Akira Yamamoto at Sankyo to discuss this issue, which was not publicly released. In the meantime, Prof. Endo isolated another compound which called lovastatin, initially referred to as mevinolin, which was a fungal metabolite of compactin.
Al Alberts, a colleague of Dr. Vagelos at Merck, had also isolated lovastatin three months earlier but he hadn’t published on it. The U.S. patent office at that time awarded a patent based on laboratory notebooks to determine who discovered it first, so Merck was awarded the patent in the U.S. and Canada. Sankyo held the patent for lovastatin in other parts of the world.
Tim: I’d like to go back to something that you said earlier about compactin. When compactin was given to the first patient, you told us that the person was so weak that they couldn’t climb the stairs and that the dose was reduced. Was that what we would call today the muscle pain and muscle weakness that some patients on statins experience? So that was known right from the beginning?
Dr. Gotto: Yes. You are right. This was described further after lovastatin came on the market. Dr. Christie Ballantyne and I published about two patients who had heart transplants, developed rhabdomyolysis and kidney failure, and had to be dialyzed. Fortunately, they recovered and were later treated with lower dose of lovastatin without complication.
These patients had been on cyclosporine (for heart transplant) and 80 mg of lovastatin. We restarted them and treated them with 20 milligrams of lovastatin and they tolerated it very well.
Lovastatin was the first statin approved, the date was September 1, 1987.
Tim: And, of course, that was game-changing as we look back historically. Is it because statins were such great LDL-cholesterol-lowering drugs and, I guess, by then the industry had demonstrated a good safety profile for statins?
Dr. Gotto: Merck felt that the increase in liver enzymes seen with lovastatin was related to its effect on the liver and was mechanism related. But the cardiologists still didn’t accept statins for cardiovascular prevention. I remember a cardiologist who was on the National Heart/Lung Advisory Council with me who said, “this is going to cause cancer.” There remained a good deal of skepticism about statins until the Scandinavian Simvastatin Survival Study (4S) was presented at the AHA in November 1994 which showed a reduction in total mortality on simvastatin.
As I mentioned earlier, the Helsinki Heart Study had showed, in patients who had the so-called triple threat – that is an elevation of triglycerides and LDL-C and low HDL-C – patients had a significant reduction in events with gemfibrozil in a primary prevention study but not a reduction in total mortality, the ultimate goal or “holy grail.”
But statins were game changers because there had never been any satisfactory treatment for lowering LDL-C. Previously, FH patients would receive low doses of cholestyramine and nicotinic acid and probucol.
The NIH even supported a trial, where I was the monitor of the DSMB which used partial ileal bypass surgery to lower LDL-C. This was called the POSCH study (Program on the Surgical Control of Hyperlipidemias). POSCH showed both a decrease in LDL-C and a decrease in risk of nonfatal MI, CHD death, and total mortality.
Mechanistically the partial ileal bypass worked through a similar mechanism to cholestyramine, by reducing bile acids which depleted the hepatic cholesterol pool.
As we now know, statins work through the LDL receptor mechanism. So that was a big plus in getting the statins approved. Mike Brown and Joe Goldstein’s research did work in dogs, and showed that inhibition of cholesterol synthesis up-regulated the LDL receptor.
So this really gave a strong rationale for the use of statins. Inhibiting cholesterol synthesis was insufficient to account for LDL-C reduction by statins.
Tim: It sounds like it was a combination of the outcome studies starting with 4S, the scientific understanding where Brown and Goldstein connected the LDL receptor to the inhibition of cholesterol synthesis, and the dramatic LDL cholesterol-lowering that combined to really change the treatment paradigm.
Dr. Gotto: That’s correct. And then you had many pharmaceutical companies entering the statin field in the ‘80s and ‘90s. Statin influence on the treatment and prevention of atherosclerotic cardiovascular disease has freely been transformative. For the first time, cholesterol and LDL-C could be lowered by 40 to 50% and its associated reduction in atherosclerotic cardiovascular disease confirmed in study after study.
Tim: This is very interesting perspective! I want to thank you, Dr. Gotto, for taking us on a journey from the earliest identification of LDL-C to the statin era. I don’t think this story is well-known and I appreciate you taking the time to discuss it with us today.
I look forward to speaking with you again soon for parts 2 and 3 of our blog series on LDL-C – first, the therapies that came after statins, and then we will ask you to look into your crystal ball and talk with us about the future of LDL-C lowering.