Antibody Decreases Cancer Stem Cells in Multiple Myeloma

The number of cancer stem cells decreased by half in multiple myeloma (MM) patients who were administered an experimental antibody treatment, a recent study found.

The antibody Medi-551 was tested in 15 newly diagnosed MM patients administered a monthly regimen of the chemotherapy drugs lenalidomide and dexamethasone.

The impact these drugs had on cancer stems cells was measured by counting the number of stem cells in the bone marrow and patient blood samples, which were measured several times throughout the 7-month study, ending in March 2016.

The results of the study initially showed an average 2.5 fold increase in bone marrow-derived cancer stem cells, after patients received 2 cycles of lenalidomide and dexamethasone alone. Once Medi-551 was added in the third and fourth months of treatment, cancer stem cells decreased on average by half in 14 of the 15 patients.

Furthermore, 5 newly diagnosed patients who did not receive the extra antibody treatment saw a 9.3 fold increase in the number of cancer stem cells after an average of 4 months of treatment with the other 2 drugs.

No serious adverse events were reported in the study.

The Medi-551 antibody had an impact because it targets the protein CD19, which is found on the surface of MM cancer stem cells.

“We chose to carry out this clinical trial in newly diagnosed patients because our original data showed that CD19 was almost always expressed by myeloma stem cells in these patients, whereas we don't know if that is the case in more advanced patients,” said lead researcher William Matsui, MD.

Additionally, researchers also tested 2 different ways to measure cancer stem cells: in tissue samples aspirated from bone marrow and in blood drawn from the patients throughout the study.

“We wanted to see if these two assays gave similar results, and in this clinical trial, they were almost identical,” said lead researcher Carol Ann Huff, MD. “Since it is much easier to draw blood than bone marrow from our patients, we think that we can primarily use blood to track multiple myeloma stem cells in the future.”

Most of the participants in the study saw a decrease in cancer stem cells after 3 doses of Medi-551. However, in 2 patients there was an increase in cancer cells resulting in each of them having their disease grow and spread during the study.

Further research is needed to determine the long-term impact of antibody treatment in MM patients to determine exactly how the antibody may work with other treatments.

“In other studies at Johns Hopkins, we have found that antibody therapies can work much better after a bone marrow transplant, especially allogeneic transplants, where patients receive bone marrow cells donated from a relative,” Matsui said.

The study’s findings were presented at the American Association for Cancer Research (AACR) Annual Meeting 2016 in New Orleans.