Researchers have successfully used gene therapy to halt the progression of fatal degenerative disease adrenoleukodystrophy (ALD)—the illness at the center of the film Lorenzo’s Oil, the Los Angeles Times reports. The breakthrough therapy—highlighted in the November 6 issue of Science—used a harmless version of HIV as a delivery system to stabilize ALD in two boys, who were 7 at the time of treatment.

About 120 young boys are diagnosed with ALD in the United States annually. While those born with the defective ALD gene seem normal until they reach about five years of age, the condition could kill them or leave them in a vegetative state within one to two years. “This is as bad as neurological disorders gets,” said Florian Eichler, MD, of Massachusetts General Hospital.

If ALD is identified before brain deterioration occurs, Lorenzo’s oil—a mixture of fats from olive and rapeseed oils—is somewhat useful in delaying progression. A bone marrow transplant is the only effective treatment option once deterioration has occurred.

This new research—conducted by Nathalie Cartier, MD, and Patrick Aubourg, MD, of Paris Descartes University—involved taking the healthy form of the ALD gene and inserting it into a benign or “defanged” version of HIV. The virus has generated interest among gene therapists because it can insert genes into cells that are not dividing. In contrast, previous viruses used as delivery systems have only been able to insert genes into actively dividing cells.

According to the Times article, HIV may also be safer as a delivery system. As a member of the lentivirus family, HIV is less likely than other retroviruses to activate unwanted genes and cause other health complications.

French researchers have already treated a third boy with ALD, and they plan to expand their trial to older men with a milder version of the disease.