Gene therapy trial forces leukemia remission

Man “cured” of terminal illness in eight days by targeted immunotherapy.

Gene therapy may hold the key to treating what is both the most common cancer among children and a dangerous cancer for adults. A study released last week showed that three adult leukemia patients were successfully treated with their own genetically modified white blood cells, after their illnesses relapsed.

Doctors assumed that one of the participants, David Aponte, was terminally ill, after his chemotherapy treatments stopped working; however, just eight days after beginning the targeted immunotherapy, Aponte’s leukemia was in remission.

The study, published last week in Science Translational Medicine, focused on five people suffering from relapsed B cell acute lymphoblastic leukemia. Researchers took healthy T cells from each of the five participants. The New York researchers exposed the T cells to a harmless virus which caused them to attack B cells and replaced them in the participants’ blood streams. Once exposed to the virus, the T cells will seek out a surface protein called CD19, and destroy any cell carrying the protein. B cells carry CD19 whether cancerous or not. This method of treatment is called targeted immunotherapy.

A press release from New York’s Memorial Sloan-Kettering Cancer Centre, where two of the lead researchers are based, states that the five patients achieved complete remission within eight weeks, with four of the five patients receiving bone marrow transplants, and three surviving beyond the transplants for periods ranging between five months and two years. Two patients died: one patient was unable to receive a bone marrow transplant, and died following a relapse; the other died while in remission from a blood clot which researchers deemed “unrelated” to the treatment.

Last year, The New York Times reported that a six-year-old girl from Pennsylvania, Emma Whitehead, received a similar treatment for the same disease, following two remissions after failed chemotherapy. Her T cells were altered by doctors at the University of Pennsylvania with the help of a genetically modified strain of HIV, with similar effects. This method does not require a bone marrow transplant, and small quantities of the genetically modified T cells remain in Whitehead’s bloodstream. At least three adults have been successfully treated using the Pennsylvania method.

B cell acute lymphoblastic leukemia is typically mild for children, with a ninety percent survival rate, but for adults, the survival rate is only forty percent. According to the Canadian Cancer Society, acute lymphoblastic leukemia is a rapid-onset cancer, developing in just days or weeks. The New York Times reported that Aponte went to his doctor believing he had a bad case of tennis elbow.

The press release from the Memorial Sloan-Kettering Cancer Center says that the next phase of the study has been planned. In this next phase, fifty patients with relapsed B cell acute lymphoblastic leukemia will receive the experimental treatment.

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