NEW ORLEANSA nonmagnetic method of depleting B cells during
purging before autologous peripheral blood stem cell (PBSC)
transplantation greatly decreases the nonspecific cell loss that can
occur when cells cross a magnet, as in other techniques. The
nonmagnetic method is also simple and quick, John Gribben, MD, of
Dana-Farber Cancer Institute, said at the 41st annual
meeting of the American Society of Hematology.
Among patients with non-Hodgkins lymphoma (NHL), contamination
of stem cells with residual tumor has been associated with a high
incidence of relapse following autologous PBSC transplantation.
Effective purging of tumor cells may improve the results of
transplantation, but current methods are technically difficult to
perform with large numbers of cells and do not consistently remove
all detectable tumor cells, Dr. Gribben explained.
In the new technique, cells are depleted using Eligix High-Density
Micropar-ticles (Eligix, Inc., Medford, Mass) coated with anti-CD19
and anti-CD20 monoclonal antibodies in a gravity-mediated system.
4-Log Depletion of B Cells
After being rotated for 5 to 10 minutes, target cells expressing
these antigens bind to the microparticle beads and then separate from
the other cells. This process is repeated several times and results
in a 4-log or greater depletion of B cells and more than 90% recovery
of CD34+ cells, Dr. Gribben said.
The phase I trial evaluated engraftment and toxicity after infusion
of PBSCs purged in this manner. The study involved nine patients with
relapsed B-cell non-Hodgkins lymphoma receiving high-dose
chemotherapy followed by infusion of autologous PBSCs depleted of B
To be eligible, patients had to be in complete or partial remission,
with less than 20% bone marrow involvement. Median age was 50.
The median yield of nontarget cells postdepletion was 84% for CD34+
cells. Following depletion, there was an 82% recovery of CD34+ cells
and 81% recovery of CD3+ cells. The median number of CD34+ cells
cryopreserved was 3.6 × 106/kg.
Depletion in CD19+ and CD20+ B cells, as assessed by
immunocytochemistry, was by more than 2 logs. B cells were
detected in relatively small numbers in patients and were not
detected at all in the PBSCs of six patients, Dr. Gribben observed.
Treatment of PBSCs with the micro-particles was not associated with a
delay in engraftment. The median time to neutrophil counts of
500/µL was 10 days. The median day to achieve a platelet count
of 20,000/µL unsupported by platelet transfusions was 12. Some
mild infusional toxicity occurred, he said.
The investigators concluded that this treatment does not result in a
delay to platelet or neutrophil engraftment, there is no significant
purging of nontarget cells, and depletion of target cells occurs
below the level of detection. A randomized trial is now being
planned, he said.