Gary Ruot is participating in a gene therapy trial to try to save his degenerating eyesight.

Last week, after more than six months of waiting, 17-year-old Gary Ruot of Debary, Florida, was accepted into a clinical trial testing a novel treatment for a rare degenerative eye disease that strikes fast and leads to irreversible blindness.

Called gene therapy, treatments such as this one attempt to slow or reverse an inherited disease by delivering a new gene to the site of a mutated, disease-causing one. Following years of setbacks, including the death of an 18-year-old patient in a 1999 experimental trial, gene therapy is in the midst of a major revival for illnesses such as hemophilia, immune disorders, and degenerative eye diseases. Several small trials are boasting promising results. And while risks still exist, some patients with inherited diseases have no alternatives to these experimental therapies. For these patients, qualifying for a trial may mean the difference between being cured and remaining sick.

The problem is that the traditional system for clinical trials isn’t equal to the urgency patients like Gary face. To get into a clinical trial for gene therapy, patients must meet specific criteria set by drug makers. Among other things, the patients must fall into a certain age group and must have had symptoms for a defined period of time. Gary was fortunate enough to petition for the rules of one trial to be changed so he could enter. But many other people aren’t so lucky.

In Gary’s case, there was little time to act. His vision first started declining in December 2015. In January he stopped playing baseball, and by February he couldn’t see to drive anymore. That month he was diagnosed with Leber’s hereditary optic neuropathy, or LHON, which affects a few as one in 50,000 people worldwide.

“This is a devastating disorder that has no proven therapy of any great efficacy,” says Nancy Newman, principal investigator in the trial and a professor of ophthalmology at Emory University School of Medicine, one of the sites where it is taking place. “That’s why a patient would be willing to move into the gene therapy area, despite the fact that there will always be risks.”

Gary’s mother, Jennifer Ruot, tracked down the trial, which is sponsored by GenSight Biologics. Since it’s testing a drug intended to correct the exact genetic mutation responsible for Gary’s vision loss, it represented his best hope to get his sight back—but he wasn’t eligible to join, because the minimum age was 18. A friend of his created a petition to deliver to the U.S. Food and Drug Administration to lower the age limit, and Jennifer called or e-mailed GenSight regularly asking for updates about the trial.

Sometimes the FDA needs to see good safety data in adults before giving the go-ahead to researchers to enroll children in clinical trials. This was the case with GenSight, which received regulatory approval this month to enroll patients aged 15 to 18.

GenSight was able to slightly expand the patient population for its trial because LHON is biologically the same disease in a 15-year-old and a 20-year-old, Newman says. Some gene therapy trials specifically target diseases in children or even infants. But not all gene therapies are considered safe for children, because they may damage organs that are not yet fully developed.

An image of an eye with Leber’s hereditary optic neuropathy, or LHON.

Designing clinical trials for gene therapy is tricky. In phase I and II trials, which are trying to establish safety, researchers seek out patients with advanced cases of the disease. That minimizes risk in case an experimental therapy goes wrong. Once a therapy moves into more advanced clinical trials, they enroll patients who have developed symptoms more recently; studying these patients is a better way to measure efficacy. But seeking patients at these different disease stages shrinks the pool of those ultimately able to participate.

Gary was particularly lucky. GenSight’s two LHON trials are enrolling only patients whose symptoms appeared in the past year, so he made the cutoff by just a few months.

Not all patients are so fortunate. Some organizations are stepping in to help connect gene therapy researchers in need of trial subjects with patients desperately seeking to mitigate a devastating disease. For example, the Baltimore-based Foundation Fighting Blindness has a registry where patients can upload their unique genetic information, allowing them to get matched to a clinical trial.

“If you’re doing gene replacement, you need to find people with that mutated gene. That population can vary from a few dozen people around the world with that particular gene to a few thousand,” says Ben Shaberman, director of science communications at the Foundation Fighting Blindness. More than 250 known mutated genes can cause inherited retinal diseases, for example.

The Alliance for Regenerative Medicine, an organization in Washington, D.C., that promotes regenerative and gene therapies, created a special committee in April in part to help guide patients into gene therapy trials.

With gene therapy on the cusp of transitioning from idea to product, many more patients stand to benefit, so there will be an ever greater need for advocacy. Though Gary and his family may have found the perfect fit, they still don’t know whether the GenSight therapy will work—or what the side effects might be.

That doesn’t seem to worry Gary. “It’s only a one-time thing, and it’s a chance to improve my life,” he says.