Allogeneic Hematopoietic Stem Cell Transplantation for Severe Aplastic Anemia and Other Bone Marrow Failure Syndromes Using G-CSF Mobilized CD34+ Selected Hematopoietic Precursor Cells Co-Infused With a Reduced Dose of Non-Mobilized Donor T-Cells

Trial Information

Allogeneic Hematopoietic Stem Cell Transplantation for Severe Aplastic Anemia and Other Bone Marrow Failure Syndromes Using G-CSF Mobilized CD34+ Selected Hematopoietic Precursor Cells Co-Infused With a Reduced Dose of Non-Mobilized Donor T-Cells

Allogeneic hematopoietic stem cell transplantation (aHSCT) can cure patients with a variety
of bone marrow failure syndromes (BMFS) including severe aplastic anemia (SAA), paroxysmal
nocturnal hematuria (PNH), and refractory anemia (RA) myelodysplastic syndrome (MDS)
associated with cytopenias. Patients with BMFS have traditionally been transplanted with
bone marrow (BM) as a stem cell source. Although chronic graft versus host disease (cGVHD)
occurs less commonly with BM compared to G-CSF mobilized peripheral blood stem cell (PBSC)
transplants, BM allografts have lower CD34+ progenitor cell numbers, which increases the
risk of graft rejection in heavily transfused BMFS patients to 15-20 percent. To overcome
this risk, our group developed a novel transplant approach for patients at high risk for
graft rejection that utilized cyclophosphamide, fludarabine and ATG conditioning followed by
infusion of a CD34+ cell rich, T-cell replete G-CSF mobilized PBSC allograft. Remarkably, in
56 consecutive BMFS patients who had multiple risk factors for graft rejection who underwent
this transplant approach graft rejection did not occur, with all patients achieving complete
donor lymphohematopoietic chimerism. Unfortunately, recipients of G-CSF mobilized PBSC had a
higher incidence of chronic GVHD than has historically been observed with BM transplantation
(72 percent vs. 50 percent cumulative incidence of cGVHD at 1 year respectively). G-CSF
mobilized PBSC transplants contained approximately a 20 fold higher dose of T-cells that had
undergone a TH- 2 type cytokine polarization, a factor which likely contributed to this high
incidence of cGVHD.

In this protocol, we attempt to prevent graft failure and to reduce the incidence of cGVHD
by transplanting high numbers of CD34+ selected PBSC co-infused with a reduced dose of
non-mobilized donor T-cells that have not undergone a TH-2 cytokine polarization.

Subjects with BMFS at high risk for graft rejection will undergo allogeneic stem cell
transplantation from an HLA identical sibling using the identical conditioning regimen
utilized in protocol 99-H-0050. Using the Miltenyi ClinicMACs system, recipients will
receive an allograft on day 0 containing donor CD34+ cells that have been positively
selected and T-cell depleted following G-CSF mobilization (goal CD34+ cell dose of 5 times
10(6) CD34+ cells /kg recipient) combined with 2 times 10(7) cells/kg of non-mobilized CD3+
T-cells previously collected and cryopreserved from the same donor by apheresis prior to
G-CSF mobilization.

Primary objective: To evaluate whether administering a CD34+ selected, T-cell depleted
peripheral blood stem cell graft with a concomitant infusion of non-mobilized donor T-cells
at a dose that matches the T-cell dose that is infused in historical bone marrow transplant
cohorts will reduce the incidence of cGVHD at 1 year to that observed with a conventional
bone marrow transplant (50 percent) without increasing the risk of graft failure. This trial
design will allow the trial to stop early if it is unlikely that we have reduced the
proportion of one year cGVHD to 50 percent or if the combined event rate for failed donor
engraftment or treatment related mortality (TRM) at day 100 exceeds 20 percent.

The primary endpoint of this study will be cGVHD at day 365.

Secondary end points include transplant related mortality, engraftment, degree of donor-host
chimerism, incidence of acute and chronic graft versus host disease (GVHD), transplant
related morbidity and overall survival. Health related quality of life will also be
assessed as a secondary outcome measure pre-transplant, 30 and 100 days post transplant and
every 6 months until 5 years post transplant.