A group of doctors in the United States has used the powerful gene-editing technique CRISPR to try and treat a patient suffering from a serious genetic disorder. It will take months or even years before knowing whether the treatment is safe and how well it might be helping patients, but doctors are optimistic.

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CRISPR stands for Clustered Regularly Interspaced Short Palindromic Repeats. The term is used to refer to the various systems that can be programmed to target specific stretches of genetic code and to edit DNA and RNA at precise locations, as well as for other purposes, such as for new diagnostic tools.

“It is just amazing how far things have come,” says Victoria Gray, who received the treatment for sickle cell disease. “I always had hoped that something will come along. It’s a good time to get healed.”

Now, researchers have used CRISPR to try and treat a disorder called sickle cell disease.

Sickle cell affects millions of people around the world, causing bone marrow to produce a defective protein that makes blood cells that are sickle-shaped. The deformed cells get stuck inside blood vessels and don’t carry oxygen normally, causing a host of debilitating and, often, eventually life-shortening complications.

“It’s horrible,” Gray said. “When you can’t walk or lift up a spoon to feed yourself, it gets really hard.”

Doctors used cells taken from patients’ own bone marrow that have been genetically modified with CRISPR to make them produce a protein that is usually only made by fetuses and by babies for a short time following birth. Now, the hope is that the protein will compensate for the defective protein that causes sickle cell disease.

“It’s exciting to see that we might be on the cusp of highly effective therapy for patients with sickle cell,” says Dr. David Altshuler, chief scientific officer at Vertex Pharmaceuticals, which conducted the study.

Gray was diagnosed with sickle cell disease when she was an infant. One major symptom is agonizing, debilitating pain. Like many sickle cell patients, her symptoms have prevented her from living a full life. She couldn’t play like other children, was afraid to travel and had to give up her dreams of becoming a doctor or a nurse.

The defective blood cells also increase the risk of infections and damage to vital organs such as the heart. They also can cause life-threatening strokes. Many people with sickle cell disease don’t live past their 40s. Gray’s heart has already suffered damage.

CRISPR enables scientists to make very precise changes in DNA, raising hopes it will lead to new ways to prevent and treat many diseases. Doctors have already started using it to try to treat cancer, mostly in China. At least two patients in the U.S. have been treated for cancer.

Later this year, doctors in Boston are planning to use CRISPR to edit cells in patients’ retinas, in hopes of restoring vision in patients with an inherited form of blindness. But there are challenges ahead.

Frangoul acknowledged there are always risks with experimental treatments. But he says the research will go very slowly and carefully with close review by the Food and Drug Administration and other advisory panels.

“We are very cautious about how we do this trial in a very systematic way to monitor the patients carefully for any complications related to the therapy,” he said.