Could CRISPR cure rare diseases before birth? Scientists are getting closer - CNBC

One of the keys to curing a rare disease is treating patients early. But what if you treated them before they were born?

Over the past decade, several researchers have pursued this provocative idea. Now, they are starting to make meaningful progress in fetal gene editing, an approach that holds the potential to stop genetic disorders before it's too late.

"If you really want to prevent the worst ravages of the disease, you can't wait until they're born," said Kiran Musunuru, a gene editing expert at the University of Pennsylvania. "You've got to go in utero."

The futuristic technique is benefiting from new advances in prenatal diagnostics and CRISPR, the Nobel Prize-winning DNA editing tool. Other scientists pursuing the idea include David Stitelman at the Yale School of Medicine, Tippi MacKenzie at University of California, San Francisco, and Aijun Wang, a biomedical engineer at UC Davis.

Musunuru made headlines is 2025 when he helped develop the world's first personalized gene editing treatment for an infant with a rare genetic disorder. But long before that, he began studying the potential for fetal gene editing with William Peranteau, a co-director of the Center for Fetal Research at the Children's Hospital of Philadelphia.

Progress had been slow. But the pair have discovered something they were not expecting.

After babies are born, their bodies' blood vessels erect barriers to help them breathe on their own. That has made it difficult to deliver gene-editing treatments to organs beyond the liver. As a result, scientists are limited in the types of diseases that they can go after.

But before babies are born, it's a different story. To their surprise, Musunuru and Peranteau found that CRISPR's molecular scissors can reach the heart and other hard-to-reach muscles of unborn animals. Their discovery could open the door to fixing genetic muscle disorders like Duchenne muscular dystrophy before the damage is done.

At Children's Hospital of Philadelphia, Peranteau is part of a team that has performed surgeries on fetuses with birth defects like spina bifida, where the spinal cord is exposed during birth. The mother goes under anesthesia while the surgeon opens up the uterus and operates on the fetus to correct the birth defect. Afterward, the unborn baby continues to develop until ready to be born.

Fetal gene editing would be less invasive than that, Peranteau said. It would be similar to how doctors routinely treat unborn babies diagnosed with fetal anemia by performing a blood transfusion through the umbilical vein.

Musunuru and Peranteau have seen promising early results in animals. But they are at least three years away from trying the approach in humans and careful to temper expectations, worrying that they might give families false hope. While the scientists believe they could treat heart and muscle disorders, getting past the blood-brain barrier still remains difficult. That means, for now, neurological conditions are off the table.

The scientists plan to make edits to what are called somatic cells. They want to steer clear of editing reproductive cells, an approach that has become one of science's biggest controversies. To many researchers, editing those cells crosses an ethical line because it can affect future generations and lead to so-called "designer babies" whose parents could modify their genes to make their descendants taller or faster. After a scientist revealed in 2018 that he had edited embryos of twin girls to protect them from HIV, a Chinese court sentenced him to three years in prison. Despite the controversy, some researchers are studying DNA editing of embryos.

Editing the DNA of a fetus has not been controversial. And new breakthroughs are bringing it closer to reality. Scientists can deliver CRISPR components by infusing trillions of microscopic fat bubbles known as lipid nanoparticles into a patient's bloodstream. The tiny containers – which hold the tools to fix DNA misspellings and guide them to the right place – are considered safer than the older method of ferrying the drug through the body inside the shell of an inactivated virus.

Meanwhile, diagnostic companies are offering "non-invasive prenatal testing," promising to identify whether a fetus is at risk of a genetic disease by testing the mother's blood. The approach is seen as less risky than screening a fetus for conditions like Down syndrome by guiding a thin, hollow needle through the mother's abdomen, known as amniocentesis.

"People used to ask `Can you even diagnose any of these things before birth?'" said Stitelman, the Yale professor who has studied fetal gene editing for over a decade. "But the technology to make these diagnoses is improving. It seems less far-fetched now than it did when I started."

For Musunuru and Peranteau, the hardest question ahead may be which diseases to tackle first. They are looking at disorders that start before birth and do not have effective treatments. They want to focus on conditions "where there's a good scientific and biological rationale to doing it before birth," Peranteau said.

"I want to be efficient and develop these therapies as quickly as possible," Peranteau said. "But more importantly, we need to make sure we're doing it in a safe and ethically responsible way."

CNBC Cures is underwritten by Alexion, AstraZeneca Rare Disease and BridgeBio.