Most US gene therapy trials that use viruses to deliver genes to bone marrow cells should be allowed to continue, Food and Drug Administration (FDA) advisors decided at a meeting held last Friday. Gene therapy trials for X-linked severe combined immune deficiency (X-SCID) were suspended in the US and several other countries, after two patients in a French trial developed leukaemia.The FDA also halted 27 other trials that use the same gene delivery system as the experimental X-SCID treatment. But at its meeting last week, the FDA's Biological Response Modifiers Advisory Committee (BRMAC) voted 19-1 in favour of allowing these studies to proceed, in cases where there are no other therapies available. This could also include X-SCID patients, although doctors 'would need to justify on a case by case basis that there were no acceptable alternatives' said Philip Noguchi of the FDA.
This decision mirrors the advice given by the US Recombinant DNA Advisory Committee (RAC) earlier this year.
Children affected by SCID have a faulty gene that means they have no working immune system, so their bodies cannot fight infections. Scientists at the Necker Hospital in Paris treated eleven X-SCID patients by using a virus to deliver a working gene to the immune cells in the bone marrow. But two of these boys, successfully treated soon after birth, subsequently developed symptoms of leukaemia at the age of three. No cases of leukaemia have been identified in X-SCID trials taking place elsewhere, or in any other gene therapy studies using the same virus delivery system. The X-SCID trial taking place at Great Ormond Street Hospital in London remains suspended, pending a joint meeting of the UK's Gene Therapy Advisory Committee and the Committee on the Safety of Medicines later this month.