Family hopes trial drug gives brothers a chance against rare Hunter syndrome

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ELMWOOD PARK, N.J. — Jason Leider can no longer hold a pencil. The 9-year-old is down to his last 20 words, and the only needs he can express are "hot dog" for hungry and "towel" for cold.

He spends hours in his home watching TV and wandering between rooms, his eyes unfocused.

"If he could just go back to where he was," said his mother, Deena Leider, remembering a younger Jason who knew numbers, shapes and colors, who could jump and run and play baseball, and who could sit still and smile for photos. His cheery gaze in vacation photos hanging on their walls are daily reminders of the old Jason.

Jason has Hunter syndrome, a rare, incurable genetic disease that in its severe form — which Jason has — causes progressive brain damage in patients until they descend into a vegetative state and die, usually in their teen years. A little more than a year ago, Jason's IQ was in the mid-50s. He could scrawl a "J" to sign his name, eat on his own and tell his dad he was thirsty. He no longer can do those things. His IQ has dropped 10 points and he has lost motor and mental skills. His mind seems to be adrift.

Recently Jason and his family were at the University of North Carolina at Chapel Hill to receive a drug that his parents hope will not only stop the disease's deadly advance, but prolong his life and even recover some of what he's lost.

His dad, Jeff Leider, said he's never known the real Jason because "he's been masked by this disease." With the monthly treatment, he said, "I'm finally gonna meet my son."

Jason's doctor, Dr. Joseph Muenzer, who is leading the clinical trial of the drug, idursulfase-IT, at the university, said it "appears to be beneficial in helping stabilize the disease," offering hope that victims of the illness could live longer, though how long isn't clear. The drug, which replaces missing enzymes in Hunter patients, is still being tested and hasn't received government approval.

"The key is prevention," Muenzer said, while cautioning, "Once you lose brain cells, you're never going to get them back."

It was to be a bittersweet moment for Jason's parents when he began doses of the drug. They had wanted him to get the treatment a year ago, before his brain damage worsened, and they had fought to hasten him into the clinical trial even as it was put on hold in 2013 because of a defective delivery device.

The Leiders feared Jason was running out of time because his IQ was hovering just above 55, the cutoff to be eligible for the study, and he was losing ground. Between ages 2 and 5, the mental acuity of children born with Hunter syndrome begins to decline. There are an estimated 400 to 500 children in the United States with the disease, most of them boys, and though their rates of decline differ, some patients can lose 15 IQ points a year.

Jason's parents enlisted the support of Rep. Bill Pascrell Jr. to lobby the Food and Drug Administration to fast-track delivery of the drug through spinal taps. Pascrell set up a meeting for Jeff with the director of the FDA's Center for Drug Evaluation and Research in Silver Spring, Md., and representatives from the pharmaceutical company that makes idursulfase-IT, giving Jeff the opportunity to share his sons' story. It worked.

Jason flew to North Carolina last July and barely qualified for the trial with an IQ score of 56.

To his parents' devastation, he was drawn into the control group, which is composed of patients who aren't given the drug so that their outcomes can be measured against those who are. Patients in the control group were promised the drug after a year. Jason's year is up.

"It killed me because he lost so much in that year," Jeff Leider said, pointing out Jason could have received 12 doses by now.

In November, Jason's brother, Justin, 6, a first-grader whose own case of Hunter syndrome is less advanced than Jason's, tested to enter the trial, scoring just below the upper limit of 85 on the IQ test to qualify. Justin began getting monthly doses of idursulfase-IT in November.

Jason and Justin will receive monthly injections of the drug until the clinical trial is over, around January 2017, Muenzer said. If the results show "significant difference" between the treated patients and the untreated patients, the drug could get federal approval and enter the market within months, he said.

In the nine months he's received the drug, Justin has shown no signs of deterioration, his parents said.

"He was always a couple of steps behind or below grade level," his mom said. He left kindergarten knowing all his letters and sounds and knowing to count.

Unlike Jason, he can play football, baseball and street hockey — albeit with a smaller range of motion than his friends. "Socially, he's totally his age," Deena Leider said

The boys already receive weekly injections of an approved version of idursulfase to manage the disease's physical symptoms, which include swollen internal organs, stiff joints and coarse facial features. Still, they can't brush their teeth or shower on their own, or even raise their hands above their heads because their joints are too stiff.

The "muscle juice," as it's known to the boys, enters their bloodstream, but it cannot enter the brain. The treatment they're receiving in North Carolina sends the drug directly into the spine and it reaches the brain through the cerebrospinal fluid.

On a recent afternoon, the boys were getting their weekly muscle juice treatment. A nurse connected bags of idursulfase and saline to ports in their chests. The boys carried the bags in small backpacks during the four hours of treatment.

Jason stared at "Peppa Pig" on TV, then circled the house, making only fleeting eye contact with his parents and siblings as he passed them. Justin colored over a princess coloring book and played a board game with his sister, Jordan, 4, the two constantly bickering.

"Dad, can I have root beer for dinner?" Justin said.

Jason's verbal ability is limited mostly to repeating what he hears. If his parents tell him they're going to a birthday party, he says, "birthday, birthday."

Even as he forgets how to speak, they see signs of the old Jason, such as when he smiles at a familiar sight.

"He's in there somewhere," Deena said. "He's just completely clouded by the disease."

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