Preliminary studies by Researchers at Johns Hopkins Kimmel Cancer Center, have shown that a vaccine made with leukemia cells may be able to reduce or eliminate the last remaining cancer cells in some chronic myeloid leukemia ( CML ) patients taking the drug Imatinib mesylate ( Gleevec, Glivec ).

Imatinib, one of the first targeted cancer therapies with wide success in chronic myeloid leukemia patients, destroys most leukemic cells in the body, but in most patients, some cancerous cells remain and are measurable with sensitive molecular tests. These remaining cells are a source of relapse, especially if Imatinib therapy is stopped.

In a pilot study published in Clinical Cancer Research, the Johns Hopkins investigators used a vaccine made from CML cells irradiated to halt their cancerous potential and genetically altered to produce an immune system stimulator called GM-CSF. The treated cells also carry molecules, called antigens, specific to CML cells, which prime the immune system to recognize and kill circulating CML cells.

The study vaccine was given to 19 CML patients with measurable cancer cells, despite taking Imatinib for at least one year. A series of 10 skin injections were given every three weeks for a total of four times. After a median of 72 months of follow-up, the number of remaining cancer cells declined in 13 patients, 12 of whom reached their lowest levels of residual cancer cells. In seven patients, chronic myeloid leukemia became completely undetectable. Because the study was conducted in a limited number of patients and not compared with other therapies, the researchers warn they cannot be sure that the responses were a result of the vaccine.

The Researchers will be testing blood samples taken from the study patients to identify the precise antigens that the immune system is recognizing. With this information, they will tailor their vaccine for additional studies that monitor immune response more precisely.

Patients receiving the trial vaccine experienced relatively few side effects that included injection site pain and swelling, occasional muscle aches and mild fevers.

According to the investigators, most patients with chronic myeloid leukemia will need to remain on Imatinib therapy for the rest of their lives. More than 90 percent of them will achieve remission, but about 10 to 15 percent of patients cannot tolerate the drug long term. Often patients have low blood cell counts, fluid retention, significant nausea and other gastrointestinal problems. Secondary therapies, including Dasatinib ( Sprycel ) and Nilotinib ( Tasigna ), also have many side effects.
Another common side effect of Imatinib is fatigue.

Imatinib also cannot be taken during pregnancy, and since one-third of CML patients are in their 20s and 30s, many patients hoping to start families would like to discontinue taking it.

Source: Johns Hopkins Medical Institutions, 2010

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