Without a risky bone-marrow transplant before symptoms appear, children with brain disease ALD can expect to live no longer than five years as nerve cells in the brain die off and erase one's ability to walk, talk, and think. Even a successful transplant can result in permanent disabilities, reports the New York Times. That's why a new study in the New England Journal of Medicine is raising eyebrows: For the first time, doctors say they have successfully repelled adrenoleukodystrophy using gene therapy, a feat that could boost the survival rate of the rare brain disease affecting one in 20,000 boys, usually around age 7. Two years after gene therapy—a treatment expected to cost hundreds of thousands of dollars—15 of 17 boys with a mutated gene causing ALD showed no symptoms. Of the two who died, one had ALD too advanced to be halted, while the other withdrew from the study.
Gene therapy "has effectively arrested the progress" of the disease, study author David A. Williams says in a release. There are drawbacks in addition to cost, however: Like with a bone-marrow transplant, it's necessary to start the therapy early as the good ALD genes, which are introduced into a patient's blood stem cells via a disabled form of HIV, take a year to multiply in bone marrow and reach the brain, where they protect neurons. Indeed, the only sign of ALD in the patients of the clinical trial was deterioration evident in brain scans. But this is not so much an issue in states that have begun newborn screening for ALD, reports NPR. Additionally, "patients don't have to wait to find a donor match" and there's no need for "immunosuppression drugs, which can have very significant, even fatal, side effects," says Williams. This "is a curative therapy."