Residual leukemia cells killed by vaccine

CML cells

A recent study shows the K562/GM-CSF vaccine can improve molecular responses in chronic myeloid leukemia (CML) patients being treated with imatinib. In some cases, complete molecular remission was achieved even after extensive previous treatment with imatinib mesylate.
 
B. Douglas Smith, MD, at Johns Hopkins Medical Institute in Baltimore, Maryland, and colleagues vaccinated 19 patients previously treated with imatinib therapy for a median of 37 months. Each patient must have had a major cytogenetic response and still present persistent, measurable disease.

Patients received a series of 4 vaccines administered every 3 weeks, along with stable doses of imatinib.

Researchers constructed the vaccine from a CML cell line designed to express granulocyte-macrophage colony-stimulating factor (GM-CSF). This protein helps attract immune cells to the vaccination site, where they encounter antigens on the surfaces of the engineered CML cells. Researchers anticipated that the immune cells would then locate and kill CML cells elsewhere in the body.

After vaccination, mean PCR measurements of BCR-ABL showed a significant decline among the entire group (P=0.03). There was a progressive decline in disease in 13 patients, 8 of whom experienced a decrease in disease burden before receiving the vaccination.

Twelve of the participants achieved their lowest measurements of tumor burden following the vaccine, and 7 became PCR-undetectable.

This study was published in the January 1 issue of Clinical Cancer Research.