Gene therapy on the rise Having fallen out of favour in the 2000s, gene therapy is now helping

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Gene
therapy
on
the
rise
Having fallen out of favour in the 2000s, gene therapy is now helping 
children who would otherwise have died at a young age, reports 
Alice 
Klein 
CHILDREN with some rare genetic conditions who would once have died 
at just a few years old could now have typical life expectancies due to 
gene-replacement therapy.
Gene therapy works by replacing sections of DNA in the body 
“
We’re curing kids of fatal diseases. It’s wonderful,” says Donald Kohn at 
the University of California, Los Angeles. 
Kohn and his colleagues are trialling a gene therapy – in which disease-
causing versions of genes are replaced by normally functioning versions 
– for leukocyte adhesion deficiency type-1 (LAD-1). 
This rare condition occurs when immune cells called leukocytes can’t 
travel to the site of a wound or injury, causing otherwise benign skin 
infections to become chronic. LAD-1 usually results in death before the 
age of 2, unless the child has a stem cell transplant. 
The gene therapy works by replacing a mutated version of the ITGB2
gene, which is responsible for LAD-1. Kohn and his colleagues take a 
child’s stem cells from bone marrow and insert regular copies of the 

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ITGB2
gene using a virus that has been modified not to cause harm. They 
then use a low dose of chemotherapy to destroy the remaining bone 
marrow, and return the edited cells back into the child. 
Since 2019, nine children have received ITGB2-replacement therapy, with 
their age at the initiation of treatment ranging from 5 months to 9 years. 
Now, none of those children experience chronic skin or lung infections 
and “they’re leading normal lives, they’re in school, they’re off all their 
antibiotics”, says Kohn. 
This is just one promising clinical trial result for several gene-replacement 
therapies presented at the annual meeting of the American Society of 
Gene and Cell Therapy, held in Washington DC from 16 to 19 May. Ewelina 
Mamcarz from St. Jude Children’s Research Hospital in Memphis, 
Tennessee, presented positive results for a gene therapy for X-linked 
severe combined immunodeficiency (X-SCID), another rare immune 
condition that is usually fatal before the age of 2 without a stem cell 
transplant. 
X-SCID is sometimes known as “bubble boy disease”, because it only 
affects males, with these children previously having to isolate in plastic 
chambers to avoid infections.