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Science | AAAS – 25 Mar 20
Science visited Moderna in 2017 for an early look at its innovative RNA-based technology for drugs and vaccines
Noen “stikkord”:
- An mRNA drug would also be easier to control than traditional gene therapy.
-If you can hack the rules of mRNA, “essentially the entire kingdom of life is available for you to play with,” says Hoge, a physician by training who left a position as a health care analyst to become Moderna’s president in 2012. Adjusting mRNA translation to fight disease “isn’t actually super high-risk biology,” he adds. "It’s what your genes would do if they were rational actors.
-One key problem, however, is that our bodies would normally destroy incoming mRNA before it could get cranking. It’s a relatively large molecule that is prone to degradation, and as far as our cells are concerned, it’s supposed to come from the nucleus, where it’s transcribed from DNA. RNA invading from outside the cell is the hallmark of a virus, and our immune system has evolved ways to recognize and destroy it.
-Among dozens of mouse studies, he presented work led by Moderna Co-Founder Kenneth Chien, then at Harvard Medical School in Boston, showing that mice recovering from induced heart attacks survived longer and had stronger hearts when injected with mRNA encoding a protein that drives blood vessel formation—vascular endothelial growth factor (VEGF).
“That got us excited,” says Pangalos, who was eager to build up AstraZeneca’s pipeline of cardiovascular drugs. “It was incredibly high risk. It was untried and untested.” But if it could work for one disease, it would likely work for many. Changing the disease target didn’t require developing or identifying a whole new drug, just altering the mRNA sequence.
-Her calculations informed an algorithm that predicts, for a given protein, what mRNA sequence would produce the structure most appealing to a ribosome. Across many drug candidates, the team saw a several-fold increase in protein production using the new designs. Bancel recalls the meeting when they described this breakthrough: “They blew my brain on the walls.”
-But for now, the company’s only published paper is the one from Chien’s group on producing VEGF in mice. It hasn’t revealed which modified nucleoside is in its newest generation of drug candidates.
-For many researchers who have worked with companies, that isn’t surprising. “It’s a highly competitive field, and they’ve made the decision that they don’t want to publish a bunch of papers. That makes sense,” says Daniel Anderson, a molecular geneticist who develops drug delivery systems at MIT. “Publishing papers can generate excitement. … But if you have a whole lot of people and a whole lot of money, it may be smart just to stay quiet and develop your technology and patent the heck out of it.”
-Last month, Moderna also began trials of its VEGF drug, developed with AstraZeneca. Intended to treat cardiovascular diseases as well as slow wound healing in diabetes, the growth factor-encoding mRNA is first being injected under the skin of trial participants to evaluate safety.
-ast month’s presentation also got attention for what it didn’t describe—trials of drugs that replace missing or deficient proteins to treat chronic diseases. Most of Moderna’s advanced candidates are vaccines, which require just a low dose of mRNA that makes enough protein to kick the immune system into gear. And all of them are administered locally, under the skin or into a muscle or tumor. To tackle lifelong diseases where patients are missing a key protein, such as an enzyme that removes toxic compounds from the body, mRNA drugs will likely have to be delivered intravenously for decades. That makes even mild toxicity or subtle immune reactions a potential deal-breaker.
-Much of the risk comes down to formulation—the molecular packaging that ferries mRNA into cells and protects it from being hacked apart by enzymes along the way. “That’s where the breakthroughs are really needed,” says RaNA’s Heartlein. Many RNA drugs to date have encapsulated the nucleic acid in nanoparticles made of lipids. But because mRNA is so large—roughly 100 times the length of the RNA used for interference therapies—it’s harder to stabilize and to encapsulate. And many lipid nanoparticles are not easily degraded in the body, so they can cause toxic buildup in the liver. “We’re going to find applications [for mRNA drugs],” Heartlein says, but “it may not be as broadly applicable at the end of the day as people are thinking.”
- Moderna is developing delivery systems that may limit toxicity.
- A separate “delivery innovation” team is developing nonlipid formulations, such as polymers that form solid, porous structures interspersed with mRNA.
- AstraZeneca’s Pangalos says his group has its sights set firmly on mRNA drugs for chronic use, and expects a drug intended for repeated dosing to enter trials in the next 18 months. But Moderna has had to retreat from optimistic predictions about a partnership with Alexion to treat a rare disease called Crigler-Najjar syndrome. The mRNA treatment would code for an enzyme that breaks down bilirubin, a toxic substance that builds up in patients’ blood. Before it can enter human testing, the companies must be sure the dose needed to impact the disease is many-fold lower than the dose that causes toxicity.
