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which this article appears: Genetics
BMJ 2003;326:181 ( 25 January )
News
FDA halts gene therapy trials after leukaemia case in France
Charles Marwick, Washington, DC
After the second occurrence of a leukaemia type illness in a patient in a
gene therapy trial in France for X linked severecombined immune
deficiency disorder (SCID), the US Food and DrugAdministration has
halted all trials that use retroviral vectorsfor inserting genes
into bone marrow stemcells.
The move is described as a "precautionary measure" pending investigation. No
evidence has been shown of leukaemia in any ofthe patients in the
United States who have had this type of genetransfer, says theFDA.
Last September the French investigators, Dr Alain Fischer and Dr Marina
Cavazzanna- Calvo at the Necker Hospital in Paris,reported that one
of 11 patients with X linked SCID they weretreating had developed T
cell leukaemia about three years afterreceiving the gene
transfer.
At that time the FDA suspended the three gene therapy trials of SCID patients
in the United States that most closely resembledthe French trial and
stopped patient enrolment. The UK Departmentof Health's Gene Therapy
Advisory Committee also recommended thatadditional measures be put
in place to protect patients undergoinggene therapy trials
(12 October, p791).
The FDA's latest step puts on hold an additional estimated 27 trials that use
retroviral vectors to insert the defective geneinto haematopoietic
stemcells.
The latest development is disappointing, as the early results of the French
trial were so promising. Seven of the patientsare in good health,
with their immune system restored. One patientwas regarded as too
ill at the time of the procedure tobenefit.
The development is regarded more as a temporary setback than the end of the
road for gene therapy. Dr Philip Noguchi, actingdirector of the FDA
office that regulates US gene therapy studies,says he regards gene
therapy as a promising treatment for patientswho have not benefited
from current treatments, such as bone marrowtransplantation.
An FDA scientific advisory committee will hold a meeting late in February.
Noguchi said the committee will be given the knowndata and asked to
makerecommendations.
Supporting the FDA's action, the American Society of Gene Therapy says that a
key question is why this has occurred only intrials involving
patients with SCID and not in the other clinicaltrials that use
retroviral vectors targeted at haematopoieticstemcells.
The society is conducting its own investigation and will report its findings
at its annual meeting in June. It is possible,says the society, that
the gene that encodes a T cell growth factortriggers the risk of
leukaemia. Other possibilities are the factthat the patients are all
infants, the nature of SCID itself,and the gene transfer
technique.
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