Haplo-Identical Transplantation for Severe Aplastic Anemia and Hypo-Plastic MDS Using Peripheral Blood Stem Cells and Post-Transplant Cyclophosphamide for GVHD Prophylaxis

Severe aplastic anemia (SAA) and myelodysplastic syndrome (MDS) are life-threatening bone
marrow disorders. For SAA patients, long term survival can be achieved with immunosuppressive
treatment. However, of those patients treated with immunosuppressive therapy, one quarter to
one third will not respond, and about 50% of responders will relapse.

Although allogeneic stem cell transplantation (allo-SCT) offers the opportunity of cure,
HLA-matched donors are available for only half the patients needing a transplant. Combined
haplo-cord transplantation has recently been shown to be a viable transplant option for those
patients lacking an HLA matched donor. In our ongoing protocol 08-H-0046, we have utilized
this approach in 29 patients with SAA, and SAA evolving to MDS with 27/29 patients having
sustained engraftment and achieving transfusion independence. However, engraftment patterns
have varied substantially and in some patients, cord engraftment was profoundly delayed or
never occurred.

Haploidentical peripheral blood stem cell transplantation (haplo-SCT) has the advantage over
cord transplantation of immediate allograft availability, higher stem cell doses, and the
feasibility of repeating cell collections if necessary for collecting CD34+ cells for stem
cells boosts or lymphocytes to treat or prevent disease relapse or infection. Recently, the
use of post-transplant cyclophosphamide (Cy) has been shown to be an effective strategy to
prevent GVHD in recipients of haploidentical HSCT, but most reports have focused on patients
with hematological malignancies. At present, few data exist on the use of haploidentical
transplantation using post-transplant cyclophosphamide for patients with aplastic anemia that
have ATG-refractory disease and are heavily-transfused and HLA-alloimmunized. These patients
are at an exceedingly high-risk for graft rejection compared to other patient populations.

This research protocol is therefore designed to evaluate the safety and effectiveness of
using an unmanipulated G- CSF mobilized peripheral stem cell allograft from a haploidentical
donor and post-transplant cyclophosphamide for patients with SAA or SAA evolving to MDS that
has proven to be refractory to conventional immunosuppressive therapy (IST) in patients who
lack an HLA-matched donor (sibling/ or matched unrelated donor) and who do not have access to
a good quality umbilical cord product that meets criteria for expansion (due to insufficient
numbers of TNC and/or CD 34+ cells and/or inadequate HLA match) on NHLBI protocol number No.
17-H-0091.

The primary endpoint of the study is chronic GVHD-free survival (defined as the percentage of
patients who are alive with no evidence of moderate or severe chronic GVHD at 1 year
post-transplant). Secondary endpoints will include engraftment, 100 day and 200-day treatment
related mortality (TRM), and standard transplant outcome variables such as non-hematologic
toxicity, incidence and severity of acute and chronic GVHD, and relapse of disease. Health
related quality of life will also be assessed as secondary outcome measure.

- INCLUSION CRITERIA - RECIPIENT:

- Diagnosed with severe aplastic anemia characterized by all the following:

1. Bone marrow cellularity <30% (excluding lymphocytes)

2. Transfusion dependence for platelets and/or RBCs

3. Neutropenia ((absolute neutrophil count less than or equal to 1000 cells/ uL) OR
for patients receiving granulocyte transfusions, absolute neutrophil count less
than or equal to 1000 cells/ uL before beginning granulocyte transfusions)

OR

- History of severe aplastic anemia transformed to MDS that meet the following criteria:
a) International Prognostic Scoring System (IPSS) risk category of INT-1 or greater,
b) <5% myeloblasts and <30% of cellularity in the bone marrow on screening morphologic
analysis.

- Intolerance of or failure to respond to standard immunosuppressive therapy.

- Availability of at least one HLA- haploidentical (i.e. > 5/10 and less than or equal
to 8/10 HLA match) related donor (HLA- A, B, C, DR, and DQ loci) who is available to
donate stem cell graft (6-75 years old).

- The patient does not have any HLA antibodies detectable against any of the mismatched
HLA alleles expressed by the haplo-donor.

- Ages 4-55 years inclusive.

- Ability to comprehend the investigational nature of the study and provide informed
consent. The procedure will be explained to subjects aged 4-17 years with formal
consent being obtained from parents or legal guardian.

EXCLUSION CRITERIA - RECIPIENT (ANY OF THE FOLLOWING):

- Availability of an HLA identical or 9/10 HLA matched (HLA A, B, C, DR, and DQ loci)
-relative to serve as a stem cell donor.

- The patient is deemed to be a candidate for a 10/10 HLA matched unrelated stem cell
transplant (availability of a donor and resources required for such a transplant).

- The patient is eligible for transplantation using an ex vivo expanded cord blood unit
on NHLBI protocol 17-H-0091

- ECOG performance status of 2 or more.

- Major anticipated illness or organ failure incompatible with survival from transplant.

- Current pregnancy, or unwillingness to take oral contraceptives or use a barrier
method of birth control or practice abstinence to refrain from pregnancy, if of
childbearing potential for one year.

- HIV positive.

- Diagnosis of Fanconi s anemia (by chromosome breakage study).

- Diffusion capacity of carbon monoxide (DLCO) <40% using DLCO corrected for Hgb or lung
volumes (patients under the age of 10 may be excluded from this criterion if they have
difficulty performing the test correctly and thus are unable to have their DLCO
assessed).

- Left ventricular ejection fraction < 40% (evaluated by ECHO) or < 30% (evaluated by
MUGA).

- Transaminases > 5x upper limit of normal.

- Serum bilirubin >4 mg/dl.

- Creatinine clearance < 50 cc/min/BSAm2 by 24-hour urine collection adjusted by body
surface area.

- Serum creatinine > 2.5 mg/dl

- Presence of an active infection not adequately responding to appropriate therapy.

- History of a malignant disease liable to relapse or progress within 5 years.

INCLUSION CRITERIA - RELATED HAPLO-IDENTICAL DONOR:

- HLA mismatched family donor (greater than or equal to 5/10 and less than or equal to
8/10 HLA match (HLA-A, B, C, DR, and DQ loci)) who is available to donate cells.

- Ages 4-75 inclusive. Note: a pediatric family member will only be considered as a
donor if a suitable adult haplo-identical donor is not available.

- Weight > 15 kg.

- For adults: Ability to comprehend the investigational nature of the study and provide
informed consent. For minors: Written informed consent from one parent or guardian who
is not the recipient of the transplant and informed assent. The process will be
explained to the minor on a level of complexity appropriate for their age and ability
to comprehend.

- Genetic testing for genes associated with bone marrow failure syndromes (BMFS)
performed at a CLIA- certified laboratory. If there is a suspicion of familial BMFS in
the recipient, then the haplo donor must have undergone genetic testing for genes
associated with BMFS - performed at a CLIA-certified laboratory, prior to enrolling in
this protocol.

EXCLUSION CRITERIA - RELATED DONOR:

- Pregnant or lactating.

- A pediatric haplo-identical donor will be excluded if a suitable adult haplo-identical
donor is available.

- Unfit to receive filgrastim (G-CSF) and undergo apheresis (history of stroke, MI,
unstable angina, uncontrolled hypertension, severe heart disease or palpable spleen).

- HIV positive (Donors who are positive for HBV, HCV or HTLV I/II, T.cruzi [Chagas] may
be used at the discretion of the investigator following counseling and approval from
the recipient).

- Sickling hemoglobinopathies including HbSS or HbSC. Donors with HbAS are acceptable.

- Psychiatric illness that would limit the patient s ability to tolerate and/or comply
with study requirements.

- Screening test positive for Chagas disease (Trypanosoma cruzi /T.
cruzi/trypanosomiasis) confirmed by the Center for Disease Control (CDC).