A recent Phase 2 study, published in the journal Bone Marrow Transplantation, evaluated Mozobil ^[1]’s (plerixafor) ability to mobilize stem cells from the bone marrow into the blood without increasing the mobility of tumor cells in multiple myeloma patients.

One common treatment option available to eligible myeloma patients is high dose chemotherapy followed by autologous stem cell transplantation. Before chemotherapy, the patient’s own stem cells are collected by peripheral blood apheresis, which looks and feels similar to a routine blood donation, and then the stem cells are transplanted back after chemotherapy.

For this regimen to be an option, two million stem cells per kilogram of body weight must be collected. For many patients, multiple sessions of stem cell collection are needed, which increases the risk of contaminating the samples with tumor cells. Even after multiple sessions, some patients cannot collect enough stem cells.

Two drugs, Neupogen (filgrastim) and Mozobil aim to solve these problems. Neupogen is a drug that is commonly used to increase stem cell production in bone marrow. It is a type of granulocyte colony-stimulating factor (G-CSF). Mozobil, which was approved by the United States Food and Drug Administration in December 2008, is designed to increase the movement of stem cells from the bone marrow into the bloodstream, where they can be collected.

According to Dr. Stefan Fruehauf, Professor of Hematology/Oncology at Paracelsus-Klinik Osnabrueck in Germany, “The availability of [Mozobil] will significantly change the management of myeloma patients on the transplantation track.”

Dr. Guido Tricot, Professor of Medicine at the University of Utah, recruited twenty patients with multiple myeloma scheduled for a stem cell transplant. They were split into two test groups. The first group included patients who were proven poor mobilizers of stem cells, and the second group included patients who were predicted poor mobilizers of stem cells.

All patients were given an injection of Mozobil in addition to G-CSF before each stem cell collection. Samples from nine patients were analyzed for tumor cell mobilization before and after Mozobil injection. None of the myeloma patients mobilized tumor cells, and most of the stem cell samples had less than one percent of the abnormal proteins associated with myeloma.

Cell counts found that 70 percent of the proven poor mobilizers and 80 percent of the predicted poor mobilizers yielded at least two million stem cells per kilogram of body weight.

Seventeen out of the 20 myeloma patients received at least one transplant. Of the three who did not receive a transplant, only one patient did not produce at least two million stem cells per kilogram of body weight. The other two patients had large enough yields but chose not to receive a transplant for other reasons.

Twelve of the patients who received the transplant were assessed one year later, and all had durable transplants.

Information collected regarding the safety of the treatment regimen was consistent with previous studies of Mozobil. The most frequent drug-related side effects were mild.

The combination of Mozobil plus G-CSF “increases patient safety and the likelihood of mobilizing sufficient stem cells for transplantation,” said Dr. Fruehauf. “This effort will further reduce the complication rate, morbidity, and mortality of stem cell transplantation in myeloma.”

For more information, please read the study in Bone Marrow Transplantation ^[2] (abstract).