Emma Whitehead is a 7-year-old cancer patient. After two years of battling with acute lymphoblastic leukemia, she was selected to participate in an experimental trial that uses a disabled version of HIV to “cure” cancer.

Emma is now in remission.

This remarkable new treatment used a manipulated version of the HIV virus to modify the girl’s white blood cells to attach her cancer. The breakthrough procedure could potentially replace bone marrow transplants in leukemia treatment, and and is administered with a single injection. For patients like Emma, the procedure is extraordinary, particularly since she responded so poorly to chemotherapy.

Generally, chemotherapy is hoped to put patients into remission long enough to receive a bone-marrow tansplant. For Emma, her leukemia never responded well enough to chemo. She never went into remission long enough to be eligible for the potentially life-saving bone marrow transplant.

Previously, the process was tested only on adult patients. In April, Emma became the first child to undergo the treatment. She was also the first patient to be treated for her kind of leukemia, reports the American Society of Hematology.

Doctors from the University of Pennsylvania and the Children’s Hospital of Philadelphia worked together to manipulate Emma’s immune system to make it target cancer cells. The took a batch of her own T cells — a type of white blood cell — and genetically engineered them to kill the B cells — another type of white blood cell — responsible for her disease.

To do this, doctors used a modified and disabled form of HIV, the virus responsible for AIDS, to alter the T cells’ genes, causing them to produce a protein called a chimeric antigen receptor on their surface, making the T cells attach to the B cells, and ultimately destroy them.

Two months after the procedure, Emma showed no sign of cancer. Six months later, Emma is still in remission and back in school.

While the procedure worked miraculously for Emma, it has not had a 100 per cent success rate. And even in Emma’s case, it was risky. The girl almost died when the procedure caused a spontaneous high fever and other near-fatal symptoms.

Out of the 12 patients in the clinical trial, three adults had complete remission; four improved but did not completely beat the cancer; one is still in early stages and therefore cannot be fully evaluated; two patients saw no effects from the treatment.

One other child was treated. Although the child initially responded, they eventually relapsed.