The FDA has suspended the gene therapy study at St. Jude Children's Hospital and Baylor College of Medicine while they investigate whether researchers followed federal safety regulations.
Dr. Laura Bowman, who headed the research for St. Jude said, "We were very concerned about letting the families know. We also didn't want to cause them undue alarm."
The FDA stresses the evidence of contamination is preliminary, and initial tests often give false results. More definitive screening could take up to two weeks. The FDA called initial contamination testing of the gene-based medicine so tenuous that it would not have alarmed the children's families by telling until the tests are confirmed.
St. Jude's gave the gene therapy to 19 relapsed children, 15 of whom have died from their cancer. Only two received the batch of gene-based medicine suspected of possible contamination, and they are among the cancer fatalities, the hospital said. Even if the cells they received were tainted, only trace amounts of HIV were involved, probably too little to infect anyone.
But the scare represents another public relations nightmare for the fledgling field of gene therapy, which continues to stumble in the race to prove its potential to cure disease.
According to the Washington Post, the FDA is investigating whether the study was performed correctly, including whether researchers notified the government quickly enough when they saw signs of possible contamination.
At question is a drug given to the patients, who suffered from neuroblastoma, the second most common childhood malignancy. It is usually diagnosed in children under 5 and strikes one in 100,000 people.
The gene therapy at St. Jude's used a special virus, an adenovirus, designed to help the patient's immune system fight the cancer. Tumor cells were removed from patients and the adenovirus was put in.
Those viruses are grown in cells in a laboratory. Researchers at St. Jude discovered last fall that the wrong cells had been used in the study. Two patients received viruses that had not been tested and could have been contaminated.
In November, tests of cells twice showed the presence of DNA from HIV.
If it occurred, the contamination could have been caused by HIV-infected blood in the laboratory being accidentally splashed on the viruses.
St. Jude notified the FDA on Feb. 4 of the problem, and mailed samples to the federal agency for more thorough testing that began Thursday, an FDA official, who spoke on condition of anonymity, said Friday.
The surviving volunteers would probably only need AIDS testing if further tests confirm the contamination, Bowman said.
The cotamination evidence reportedly came from St. Jude. No contamination has been found in the therapy given to the six children treated at Baylor.
The revelations come amid increasing concern over how safe gene therapy experiments are. The FDA last month shut down an experiment at the University of Pennsylvania after an 18-year-old patient died. Since then, the NIH has learned of hundreds of previously reported problems with gene therapy experiments. A Senate subcommittee held hearings on gene tests in early February.