Every drug that worked came with the same brutal bargain
For generations, medicine has offered patients with the most severe inherited cholesterol disorder a grim exchange — lower your risk of heart disease, but slowly damage your liver in the process. Now, researchers at the Medical University of South Carolina have identified a compound called DL-1 that appears to dissolve that tradeoff, reducing dangerous cholesterol output by more than 40 percent in human liver cells without triggering the fatty buildup that has long shadowed existing treatments. The discovery, born from screening 10,000 compounds against lab-grown human liver tissue, points toward a new philosophy in cholesterol medicine — cutting off the supply rather than chasing the excess — and may extend hope to the millions of patients for whom current drugs have never been enough.
- Patients with the most severe form of familial hypercholesterolemia face heart disease that can arrive before adulthood, and the drugs meant to help them quietly injure their livers over time.
- Every existing backup treatment — lomitapide and mipomersen — works by blocking cholesterol assembly in the liver, but the fat that can't exit simply accumulates inside liver cells, trading one danger for another.
- Researchers grew functional human liver cells from reprogrammed skin and blood samples, then ran a sweeping screen of 10,000 compounds, watching for anything that could silence cholesterol output without harming the cells.
- The winning compound, DL-1, cut cholesterol-carrying protein secretion by up to 44 percent and reduced total cholesterol by 32 percent — and when researchers examined the liver cells afterward, they found no fat buildup whatsoever, breaking a pattern that had held across every prior drug in this class.
- When tested in mice engineered with mostly human liver tissue, a refined version of the compound drove down LDL, triglycerides, and even Lp(a) — a stubborn blood-fat marker most cholesterol drugs never touch — while leaving healthy cholesterol and liver tissue undisturbed.
Every drug available for the most severe form of inherited high cholesterol carries the same hidden cost: it lowers cholesterol while quietly filling the liver with fat. Stephen Duncan, a regenerative medicine researcher at the Medical University of South Carolina, set out to find whether that tradeoff was truly unavoidable.
The condition, familial hypercholesterolemia, disables the receptor that normally pulls cholesterol from the bloodstream. Its severe form affects roughly one in 300,000 people and leaves patients almost entirely unresponsive to statins, with LDL levels that stay dangerously high and heart disease that can arrive before adulthood. When statins fail, doctors turn to lomitapide and mipomersen — drugs that block cholesterol-particle assembly inside the liver and lower bad cholesterol effectively, but also cause fatty buildup that damages the organ over time.
Duncan's team took an unconventional route. They grew working human liver cells from reprogrammed stem cells and used them to screen 10,000 chemically diverse compounds, watching for anything that could reduce the secretion of apoB — the structural protein wrapped around every LDL particle that leaves the liver. After several rounds of filtering, one compound emerged clearly. They named it DL-1. At low doses, it cut apoB secretion by 40 percent in healthy liver cells and 44 percent in cells from a patient with the severe form of the disease. Total cholesterol in the cell medium dropped by 32 percent.
What set DL-1 apart was what it didn't do. Existing drugs prevent fat from being loaded onto apoB, so whatever fat can't exit accumulates inside liver cells instead. DL-1 left the cells looking entirely normal — no extra fat droplets, no buildup. It was the first compound of its kind to reduce apoB production without triggering hepatic steatosis.
A complication followed: mouse liver cells ignored DL-1 entirely, meaning standard rodent trials would have missed it. The team turned to mice engineered so that more than 70 percent of their liver cells are human. Over seven days of dosing with a more soluble version called DL-27, these animals showed significant drops in apoB, LDL, total cholesterol, and triglycerides. Lp(a) — a blood-fat particle that raises long-term heart risk and that most cholesterol drugs don't affect — also fell substantially. Liver tissue from treated animals looked indistinguishable from untreated controls.
Where most cholesterol drugs work by pushing the liver to clear more from the blood — a strategy that fails when the clearing receptor is broken — DL-1 cuts off the supply line instead. That mechanism could matter well beyond familial hypercholesterolemia: roughly two-thirds of coronary artery disease patients on statins alone never reach their cholesterol targets. Duncan describes the work as the epitome of personalized medicine — using human stem cells to model disease, run drug discovery, and potentially return a treatment to the very patients whose cells made it possible.
Every drug that works for the most severe form of inherited high cholesterol comes with the same brutal bargain: it lowers cholesterol but fills the liver with fat. Stephen Duncan, a regenerative medicine researcher at the Medical University of South Carolina, decided that tradeoff didn't have to exist.
The condition is called familial hypercholesterolemia. It disables the receptor that normally pulls cholesterol from the bloodstream. The mild form affects about one in 300 adults. The severe homozygous version, striking roughly one in 300,000 people, leaves patients almost completely unresponsive to statins. Their LDL numbers stay dangerously high. Heart disease often arrives early—sometimes before they reach adulthood.
When statins fail, doctors turn to backup drugs: lomitapide and mipomersen. Both work by blocking the assembly line inside the liver that builds cholesterol-carrying particles. Both lower bad cholesterol effectively. Both also cause hepatic steatosis, a fatty buildup that damages the organ over time. It's a choice between two kinds of harm.
Duncan's team took an unusual path. They grew working human liver cells from stem cells—reprogrammed samples of human skin or blood, nudged step by step into hepatocytes, the liver's workhorse cells. These lab-grown cells behaved like real liver tissue, including how they assembled cholesterol-carrying particles for export. That setup let the team run a massive drug screen. They tested 10,000 chemically diverse compounds from a proprietary collection of 130,000, hunting for anything that could quiet cholesterol output without poisoning the cells.
The marker they watched was apoB, the structural protein wrapped around every particle of LDL that exits the liver. Less apoB in the dish meant less cholesterol on the move. After several rounds of filtering, one compound surfaced as the clear lead. They named it DL-1. At a low dose, it cut apoB secretion by 40 percent in healthy liver cells and 44 percent in cells from a patient with the severe form. Total cholesterol in the cell medium dropped by 32 percent. DL-1 belonged to a chemical family called triazine thiols and shared no resemblance to any existing cholesterol drug.
Here's where the result split from everything that came before. Lomitapide and mipomersen prevent fat from being loaded onto apoB inside the liver—and whatever fat can't exit that way accumulates inside liver cells instead. DL-1 left the cells looking normal. Stained sections showed no extra fat droplets, no buildup. "We found that apoB levels go way down when we give the cells the drug. Cholesterol levels go down," Duncan said. Until this study, every drug that reduced apoB production also caused fat to pile up inside hepatocytes. DL-1 broke the pattern.
Then came a complication. When researchers gave triazine thiols to mice with high cholesterol, nothing happened. Mouse liver cells simply ignored the compound. Whatever DL-1 latches onto inside the liver, mouse cells apparently don't carry the same molecular target—which explains why standard rodent drug screens would have missed it entirely. An unusual animal model provided the solution: mice engineered so that more than 70 percent of their liver cells are human, repopulated from a donor. Over seven days of daily dosing with a more soluble version called DL-27, the humanized mice showed sharp drops in serum apoB, total cholesterol, LDL, and triglycerides. Lp(a), a separate blood-fat particle that raises long-term heart risk and that most cholesterol drugs do not touch, also dropped substantially. Good cholesterol stayed steady. Liver tissue from the treated animals looked indistinguishable from controls under the microscope.
Most cholesterol drugs work by pushing the liver to clear more from the blood—an approach that fails entirely when the receptor is broken. DL-1 cuts off the supply line instead. Even outside familial hypercholesterolemia, that mechanism opens a route for patients who don't respond to first-line drugs. Roughly two-thirds of coronary artery disease patients on statin therapy alone fail to hit their cholesterol targets. The study, published in Communications Biology, represents what Duncan calls the epitome of personalized medicine: using human stem cells to model disease, complete a drug discovery process, and find a drug that could potentially treat a patient.
Citações Notáveis
We found that apoB levels go way down when we give the cells the drug. Cholesterol levels go down.— Stephen A. Duncan, Medical University of South Carolina
Showing that you can use these human stem cells as a system to model disease, complete a drug discovery process and find a drug that could potentially be used to treat a patient—that is the epitome of personalized medicine.— Stephen A. Duncan
A Conversa do Hearth Outra perspectiva sobre a história
Why does it matter that this compound works differently from the existing drugs?
Because the existing drugs work by blocking the assembly line, which causes fat to back up inside the liver cells. It's like damming a river—the water has to go somewhere. DL-1 doesn't block the assembly line. It reduces how much cholesterol gets made in the first place. The fat never accumulates.
How did they find this compound among 10,000 others?
They grew human liver cells in a dish and watched what happened when they exposed them to different chemicals. They were looking for one specific signal: less apoB leaving the cells, which means less cholesterol being exported. Most compounds either did nothing or poisoned the cells. DL-1 did exactly what they wanted.
The mouse problem is interesting. Why didn't it work in regular mice?
Mouse livers don't have whatever molecular target DL-1 binds to. So the compound was invisible to them. That's actually why this discovery matters—a standard drug screen using mice would have thrown it away. They only found it because they used human cells first.
What about the humanized mice? How does that even work?
They're engineered so that over 70 percent of their liver cells are actually human cells, grown from a donor. When you give those mice the drug, the human cells respond. It's a bridge between the dish and a real organism.
Does this help people with familial hypercholesterolemia right away?
Not yet. This is early-stage research. They've shown it works in cells and in mice. The next step is human trials. But for people with the severe form who can't tolerate existing drugs or don't respond to them, this represents a completely different mechanism. That's hope.
You mentioned it might help beyond familial hypercholesterolemia.
Yes. About two-thirds of people with coronary artery disease who take statins still don't hit their cholesterol targets. They're statin-resistant for various reasons. A drug that works by a different mechanism—cutting off production instead of increasing clearance—could help them too.