Some diseases are caused by errors (mutations) in
specific genes. Gene therapy delivers DNA into cells to replace
mutated (“bad”) or missing genes or to add new, “good” genes.
Scientists are investigating a number of different
ways to do this. Right now, gene therapy is only done through research studies
called clinical trials. Unlike medicine, gene therapy directly addresses the underlying
genetic problem, not just the symptoms.
Genes are in the nucleus of every living cell. A gene is an instruction manual for the body. It
gives the direction to make the proteins that make the body work.
A gene cannot be inserted directly into a cell.
Instead, a carrier called a vector is genetically engineered to deliver the
gene. Viruses are usually used as the vectors because they are very good at
“infecting” cells and inserting the gene(s) into the cells’ DNA. Types of viral
vectors are retrovirus, adenovirus, adeno-associated virus and herpes simplex
No. The virus is specially engineered to remove the infectious piece. We only keep the part of the virus that is good at burrowing
into a cell’s nucleus. Once the virus delivers the gene into the cell, the
virus slips away.
It is not for all genetic diseases. It is only for
some diseases caused by a single gene mutation. Some diseases that might be
treated with gene therapy are:
The goal is to cure a disease or make changes so the
body can better fight off disease. It does not correct 100% of your child’s cells.
Instead, every time a cell with the “good” gene reproduces, it carries a copy
of the new healthy gene.
The vector can be injected or given by IV directly
into a specific tissue. Or a sample of cells can be removed and exposed to the
vector in a laboratory. The cells with the vector are then returned to the
1) Stem cells are collected in one of two ways: by bone marrow aspiration, or by purifying blood drawn through a central line in a process called apheresis.
2) Before the infusion, most children have chemotherapy. This makes room for the new cells by getting rid of the existing cells in the bone marrow.
3) In the laboratory, the stem cells from the blood or bone marrow are exposed to a virus or other type of vector containing the desired genes.
4) Once the stem cells take up the vector and merge the genes into cells’ DNA, the cells are given back to the patient in an IV infusion.
Bone marrow transplants use
stem cells from another person (a donor). Gene therapy uses your child’s own
cells. Using your child’s own cells is a benefit because there is no risk of
rejection, or graft vs. host disease, like there is with donor cells. Gene
therapy is still only offered through clinical trials and at only a few
research hospitals and centers.
Gene therapy is still very new,
and is mostly used to treat children who cannot be cured by standard
treatments. Gene therapy is not for every
disease or a good fit for every patient. Your child
needs to meet certain criteria for safety reasons. Your child’s doctor will
talk to you about whether your child is a good fit for a gene therapy clinical
Your child will have 4–10 days
of chemotherapy before the infusion. This is called chemotherapy conditioning.
It clears out bone marrow to make room for the new stem cells. This has typical
side effects from chemotherapy, like nausea/vomiting, mouth sores and pain.
Your child has the transfusion
on the Bone Marrow Transplant floor (6 West) at the Jimmy Fund Clinic. It is given one time
intravenously (through an IV), just like a blood transfusion. It takes 15–30
minutes. The amount of time your child
will stay in the hospital depends on many factors. Most children stay 4–6
Your child will have blood
tests to check for the vector in the cells, and to see how the cells are responding. Your child will come in for
follow-ups frequently. Your child’s care team will talk to you about when you
should call your child’s doctor. Always call with questions or concerns or if
you notice signs of an infection.
Many research studies are
underway to test gene therapy as a safe treatment for a growing number of
diseases. Improvements have already been
made in safety. Early gene therapy trials showed a high risk of “turning on”
oncogenes that cause cancer. Now, experts have retooled the vector to lower the
likelihood of turning on oncogenes.