In a future When gene therapy can modify a person’s genome precisely enough to cure them of a serious disease, it’s often better to treat sooner – and the womb is as early as possible. Last week at the annual meeting of the American Society of Gene & Cell Therapy in Los Angeles, a handful of researchers presented their progress on in utero gene therapy, showing that research on laboratory animals offers some hope for humane treatments, but still faces significant hurdles.
Doctors can already detect abnormalities in the DNA of a developing human fetus. Conditions such as sickle cell anemia and spinal muscular atrophy occur with genetic signatures – sometimes as simple as a single genetic mutation – that show up in prenatal screenings. New gene therapies can treat adults and even children with these diseases, but they have some drawbacks: They can cost millions of dollars for a single dose, and many are currently only available to participants in clinical trials. Importantly, by the time a person receives them, they may already have spent months or even years living with a serious illness.
Doctors and scientists hope that by correcting these abnormalities before birth, a newborn will have a better chance of leading a healthy life. “The main benefit of giving these therapies in the womb or before birth would be to prevent disease before it happens,” says Bill Peranteau, a pediatric and fetal surgeon at Children’s Hospital of Philadelphia, whose team presented at the conference.
His team has studied many diseases, including cystic fibrosis and metabolic disorders. Other conference attendees presented research on conditions that affect the liver, muscles, brain, or spinal cord. Overall, these teams tend to focus on serious illnesses that can benefit from early treatment. For some conditions, Peranteau says, “if you wait until after birth — or long after birth — you’ll miss a window of opportunity to prevent irreversible pathology.”
Fetal development provides this window, because at this stage the fetus has many unspecialized stem cells that will give rise to all kinds of body tissue. A fetus’s immune system has not fully matured, so it is less likely to reject biological therapy than an infant’s immune system would be. And he is small, which means that his dose of a complex and expensive drug can also be low.
A gene therapy “drug” is not a drug in the traditional sense; it is not a chemical compound that kills invading germs or soothes the symptoms of illness. Instead, it’s often a DNA-editing tool, such as Crispr, packaged in some sort of delivery vehicle, usually a virus or nanoparticle, that transports it to target cells. Therapy can then cut, swap, or insert genes to reverse or lessen the disease.
“Childbirth remains a very big challenge,” says Rohan Palanki, a bioengineer and medical/doctoral student who works with Peranteau, because it can be difficult to target cells in organs like the brain, lungs and skin. The best way to solve the delivery problem depends on the disease and the type of gene therapy. Researchers can optimize the microscopic vehicle that delivers the genetic machinery, inject the drug into a specific region or at a specific time during pregnancy, or all of the above.