FDA Panel Recommends ‘Severely Restricted’ Participation in Gene Therapy Trials

In a "serious blow" to the field of gene therapy, the FDA's biological response modifiers advisory committee on Friday recommended that two pending U.S. gene therapy trials be "severely restricted" to patients who have exhausted all other treatment options, the Washington Post reports. The committee recommended "less stringent" criteria for the continuation of the U.S. single gene therapy study aimed at a related immune system disorder, know as ADA-SCID, the Post reports. The committee also recommended the resumption of 27 "distantly related" gene therapy studies, as long as prospective participants are completely informed of new potential risks and are carefully monitored for signs of leukemia, the Post reports (Weiss, Washington Post, 3/1). In January, the FDA suspended 27 U.S. gene therapy trials after a boy in France who received new genes to cure severe combined immunodeficiency, or X-SCID, often referred to as "bubble-boy" disease, developed cancer. In September 2002, the agency suspended three gene therapy trials after another boy developed cancer. Researchers have long suspected that retroviruses, which were used in the trial in which the second boy participated, could lead to cancer (California Healthline, 1/15).

Some researchers had hoped the committee would find ways to reduce the risk of cancer, but committee members "repeatedly expressed fears" that more of the children who received gene therapy to treat X-SCID would develop leukemia, the Post reports. "We need about two more years before I can say how safe this therapy is," committee Chair Daniel Salomon of the Scripps Research Institute said, referring to the apparent delay between treatment and onset of cancer. He added, "Until then, regardless of its incredible benefits, I'm not comfortable supporting it anymore unless there is no alternative" (Washington Post, 3/1). In a statement, the FDA said it would review the panel's recommendations and "actively consider" researchers' requests to conduct clinical gene therapy trials for patients with fatal or life-threatening conditions and no other treatment options, the New York Times reports (Kolata, New York Times, 3/1).