Gene Therapy Advance In Leukemia Suggests New Treatment Options For Multiple Myeloma
Published: Aug 12, 2011 2:52 am
A promising experimental method for treating advanced leukemia may point the way to important new treatment options for multiple myeloma.
“It is very exciting,” said Dr. Leif Bergsagel, a myeloma specialist from the Mayo Clinic in Arizona who was not involved in the study investigating the leukemia treatment. “I think this approach could and should be extended to multiple myeloma.” He pointed out, however, that “It will be several years before myeloma patients will be treated this way.”
In two recently published research articles, scientists from the University of Pennsylvania described initial results of a pilot study they are conducting. The results are for three men with very advanced cases of chronic lymphocytic leukemia (CLL). Each of the men in the study received an experimental treatment that used genetically altered versions of the patient’s own immune cells to attack the patient’s cancer cells.
Two of the men in the study achieved complete responses and continue to be free of any signs of cancer after 10 months of follow-up time. The other patient achieved a partial response lasting at least eight months.
The Penn researchers said that they plan to treat more patients with longer follow-up times and that they would like to expand their study to include other types of cancer.
As with myeloma, donor stem cell transplantation is currently the only possible cure for CLL. However, most CLL patients who receive a transplant relapse, and there are significant risks and side effects to transplantation.
The study authors suggested that their new approach has the potential to cure leukemia patients like donor stem cell transplantation, but in a safer manner.
Previous studies, including those for myeloma, have attempted to use patients’ immune cells to kill their cancer cells. However, these studies have had limited success. According to Dr. Bergsagel, the Penn approach to modifying the patients’ immune cells “is quite different from anything tried before for multiple myeloma.”
In the Penn study, the researchers collected T-cells, which are a type of white blood cell, from the patients in the study.
The T-cells were then infected with a virus designed to genetically alter the T-cells so that they can recognize, attack, and kill leukemia cells.
The virus also was structured so that the altered T-cells would be able to reproduce and pass along to their later generations the ability to recognize and kill leukemia cells.
Once the patients in the study had their T-cells collected and altered, the patients were treated with chemotherapy, and the engineered T-cells were then re-infused into the patients.
Within a couple weeks of treatment, each of the patients developed flu-like symptoms due to tumor lysis syndrome, a life-threatening complication caused by large numbers of cancer cells dying too fast for the body to be able to dispose of them. Within a couple more weeks, the patients recovered from the condition and, in two of the three cases, no leukemia was able to be detected.
The Penn researchers found that, as designed, the T-cells infused into the study patients multiplied dramatically. Additionally, six months after treatment, the patients still had T-cells that persisted in seeking out and killing leukemia cells.
Leukemia cells are malignant forms of immune cells known as B-cells. The modified T-cells in the Penn study were not able to differentiate between leukemia cells and healthy B-cells. As a result, the patients in the study also experienced loss of normal B-cells and required monthly intravenous doses of immunoglobulins to prevent infection. The study researchers note, though, that there are methods to counteract overactive T-cells, including immunosuppressive agents.
An approach similar to the Penn method could be used to treat multiple myeloma, although it would need to be modified so that the T-cells target myeloma cells.
Multiple myeloma cells are cancerous forms of plasma cells, another type of immune cell. It is therefore possible, Dr. Bergsagel explained, that “If [the Penn approach] is successful in myeloma, it might permanently wipe out all plasma cells, both normal and malignant.” He added, however, that it is possible for people to live without plasma cells.
Dr. Bergsagel also cautioned that genetically engineering T-cells could activate cancer-causing genes, or inactivate genes that suppress cancer, eventually leading to T-cell leukemia.
“Only with the more widespread clinical use of [engineered] T-cells will we learn whether the results…reflect an authentic advance toward a clinically applicable and effective therapy or yet another promising lead that runs into a barrier that cannot be easily overcome,” wrote Drs. Walter Urba and Dan Longo from the Chiles Research Institute in Portland, Oregon, in an editorial about the Penn study.
For more information about the experimental leukemia treatment, see the study results in The New England Journal of Medicine and Science Translational Medicine as well as the related New England Journal of Medicine editorial.
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