For the past 30 years, gene therapy — which involves modifying a person’s DNA to treat or prevent disease — has been one of the most promising areas of medicine. Think about it: Instead of having to take a drug every day to manage an illness for the rest of your life, you could have your genes altered to permanently fix the problem.

But no gene therapy treatments have ever been brought to the US market — until this year.

In a first, the Food and Drug Administration approved several gene treatments for market. There was Luxturna, for adults and children with an inherited form of vision loss that can result in blindness; Yescarta, to treat adult patients with certain types of large B-cell lymphoma; and Kymriah, for children and young adult patients with a form of acute lymphoblastic leukemia.

“2017 is absolutely a watershed for the whole concept of gene therapy,” said Stephan Grupp, who directs the cancer immunotherapy program at the Children’s Hospital of Philadelphia. (Grupp’s hospital was behind two of the new therapies.)