"Bubble boy" has leukaemia after UK gene therapy

LONDON (Reuters) - A 3-year-old "bubble boy" undergoing pioneering gene therapy in London has developed leukaemia in a setback for the experimental treatment.

Doctors at Great Ormond Street Hospital said on Tuesday the boy had been successfully treated for x-linked severe combined immunodeficiency (SCID-X1) often known as "baby in the bubble syndrome," but developed leukaemia two years later.

Although gene therapy has been linked to leukaemia before, this is the first case within the London hospital's programme. Doctors said they are seeking improved formulations of the genetic medicine for new trials next year.

Five years ago, similar cases of leukaemia occurred in two French boys who were given gene therapy.

Researchers believe in those cases the experimental treatment triggered a gene that caused their bone marrow to overproduce immune system cells called T-cells.

Leonard Seymour, professor of gene therapies at the University of Oxford, said the latest case showed the need to balance the risks for patients, given that gene therapy is often the only hope.

Childhood leukaemia is generally treatable, with cure rates of 90 percent or more. In contrast, children with SCID who cannot get a bone marrow transplant almost always die within a year.

The Great Ormond Street Hospital has a worldwide reputation for treating sick children.