Intra-marrow transplantation of Mesenchymal Stromal Cells to treat MyeloDysplastic Syndromes: A feasibility study

Myelodysplastic syndromes (MDS) are a heterogeneous group of disorders
characterized by impaired peripheral blood cell production (cytopenias) and
most commonly a hypercellular, dysplastic-appearing bone marrow. About 500 new
cases are reported annually in the Netherlands. Based on the number of bone
marrow blasts, cytogenetic abnormalities and the severity of the cytopenias,
MDS patients can be categorized as lower-risk or higher-risk. Higher-risk
patients tend to evolve in acute myeloid leukemia (AML) and are treated
accordingly. Lower-risk patients usually die of bone marrow failure. Other than
*best supportive care* (transfusions, antibiotics), no standard treatment is
available for these patients.
Most investigations on MDS have focused on the hematopoietic stem/progenitor
compartment, but various abnormalities have also been identified in the immune
system and the bone marrow microenvironment in MDS patients. This insight has
resulted in the successful use of immune modulatory (e.g. lenalidomide) and
immune suppressive drugs (e.g. ATG and/or cyclosporine). However, only a subset
of patients responds to these treatments, without a survival benefit. The
armamentarium of immune regulatory agents has recently been expanded with
mesenchymal stromal cells (MSCs) generated from healthy donors (*third party*).
In contrast to conventional immune modulatory drugs, MSCs provide a more
specific and more powerful modulation of the immune system. This is illustrated
by our experience with MSCs for the treatment of steroid-resistant GVHD. In
addition, MSCs provide another potential advantage: MSCs, derived from bone
marrow stroma, produce bioactive molecules and regenerate the microenvironment,
which is also considered to be crucial for the pathogenesis of MDS. Thus, both
a specific and powerful immune modulation combined with a restoration of the
microenvironment might provide a more sustained response to therapy, compared
with usual therapies. This is in particular important, as in daily clinical
practice, most patients with lower-risk MDS have few treatment options and die
of their disease. To optimally modulate the bone marrow microenvironment we
want to infuse third party MSCs directly into the bone marrow space, a
procedure in our preliminary data shown to be feasible.
In this proposal we aim to study the safety and efficacy of intra-marrow
transplantation of third party MSCs in lower-risk MDS patients. We hypothesize
that intra-marrow transplantation of MSCs will re-establish normal
hematopoiesis in lower-risk MDS patients.

This proposed study has three main objectives:

1. To determine the feasibility of intra-marrow transplantation (IMT) of MSCs
in lower risk MDS patients (a Phase I/II study):
Although we have experience with application of (unrelated) MSCs and
intra-marrow infusion of transplants, we will start this project with a Phase I
dose escalation safety study in 9 patients with lower-risk MDS and a treatment
indication (symptomatic cytopenia). Subsequently, we will treat 20 additional
patients to study feasibility and safety. All relevant clinical parameters for
patients suffering from MDS, including peripheral blood counts and transfusion
dependency, will be monitored.

2. To assess the impact of IMT of MSCs on the bone marrow microenvironment
The bone marrow microenvironment will be studied prior to and 3 months after
intra-marrow transplantation of MSCs. MSCs will be isolated and expanded for
2-3 passages for subsequent analyses. Additional studies, using conventional
cytogenetics and FISH, should identify the impact of intra-marrow MSC
transplantation on clonal composition of both CD34+ hematopoietic
stem/progenitor cells and CD45- MSCs. In addition, the origin of CD45- MSCs
(patient versus donor) in the bone marrow microenvironment 3 months after
intra-marrow MSC transplantation will be investigated.

3. To assess the impact of IMT of MSCs on immune regulatory and effector cells
The immune profile (T-cell subsets, T-cell clonality, myeloid derived
suppressor cells, dendritic cells) and bioactive molecules (e.g. cytokines)
will be studied prior to and 1 and 4 weeks after intra-marrow transplantation.
The aim of these studies is to investigate the impact of MSCs on the immune
profile in MDS patients and to identify predictors for response to MSC therapy.

This is a phase I/II feasibility study. Patients with MDS (RCUD, RARS, RCMD and
RAEB1) and an IPSS score of 0.5 or 1 and an indication for treatment (patients
should have had at least one red blood cell (RBC) transfusion in the two months
prior to inclusion due to a hemoglobin level < 6 mmol/l) are eligible.

Nine patients (classic 3x3 design) will participate in the phase I part and
receive increasing doses of MSCs directly infused in the bone marrow cavity of
the left or right spina iliaca post (intra-marrow). In the phase II study
eligible patients will receive a fixed (safe) dose of MSCs in the left or right
spina iliaca posterior superior. In addition, patients without response after
the first MSC transplantation will be infused with the same dose of MSCS in the
left and right spina iliaca posterior superior (dose and space escalation)
(re-treatment. In addition, patients without response after the first MSC
transplantation will be infused with the same dose of MSCS in the left and
right spina iliaca posterior superior (dose and space escalation)
(re-treatment).

Nine patients (classic 3x3 design) will participate in the phase I part and
receive increasing doses of MSCs directly infused in the bone marrow cavity of
the left or right spina iliaca post (intra-marrow) and will be observed for 3
months.

For this study we will use fixed doses of MSCs: patients whose weight is below
80 kg will receive a lower dose compared with patients whose weight is higher
than 80 kg. The reason to use fixed doses is because we assume, based on our
previous experience with MSCs, that small deviations from the standard dose per
kg will have negligible impact on the clinical effect and because fixed doses
allow bed-side preparation of the cellular product which also has logistic and
financial advantages.

The first 3 patients will receive about 0.1 x 106 MSCs/kg (in 20 ml) directly
infused into the bone marrow cavity via either the left or right spina iliaca
posterior superior. In fact: patients with a weight lower than 80 kg receive
7.5 x 106 MSCs (in 20 ml) and patients with a weight higher than 80 kg receive
10 x 106 MSCs (in 20 ml). If no toxicities are observed, the second set of 3
patients will receive about 0.5 x 106 MSCs/kg (in 20 ml) directly infused into
the bone marrow cavity via either the left or right spina iliaca posterior
superior. In fact: patients with a weight lower than 80 kg receive 40 x 106
MSCs (in 20 ml) and patients with a weight higher than 80 kg receive 50 x 106
MSCs (in 20 ml). If no toxicities are observed, the third set of 3 patients
will receive 1 x 106 MSCs/kg (in 20 ml) directly infused into the bone marrow
cavity. If no toxicities are observed after this last set of patients is
treated, the Phase II study will be started at a dose level of about 1 x 106
MSCs/kg (in 20 ml). In fact: patients with a weight lower than 80 kg receive 75
x 106 MSCs (in 20 ml) and patients with a weight higher than 80 kg receive 100
x 106 MSCs (in 20 ml).

In the phase II part 20 patients will receive the optimal dose of MSCs (as
determined in the phase I part of this study) directly infused in the bone
marrow cavity of the left or right spina iliaca post (intra-marrow). We expect
that the optimal dose will be about 1 x 106 MSCs/kg (in 20 ml). Since we will
infuse fixed doses of MSCs: patients < 80 kg will receive 75 x 106 MSCs/kg (in
20 ml) and patients > 80 kg will receive 100 x 106 MSCs/kg (in 20 ml).

Intra-marrow infusion
Prior to the infusion the patient gets adequate pain relief using continuous
morphine infusion (pump), conform the protocol which was used for our
preliminary study on intra-marrow infusion of autologous stem/progenitor cells.
In addition, prior to infusion of MSCs clemastine (1 or 2 mg) iv, paracetamol 1
g orally, morphine continuous iv and prednisone 25 mg iv will be given. After
thawing the MSCs will be infused over 30 minutes into the bone marrow
compartment via a Jamshidi needle in the spina iliaca posterior superior. Per
infusion, a total volume of 20 ml will be infused. Infusion of the MSC
transplant will be performed by a hematologist experienced in intra-marrow
infusion. Post-infusion patients will be monitored according to routine
practice.

Post-transplant clinical evaluation
To determine response (CR, PR, hematological improvement (erythroid response,
platelet response, neuthophil response), stable disease and treatment failure)
the Interantional Working Group (IWG) criteria will be used. In short:
according to IWG an erythroid response is defined as a Hb increase by * 0.9
mmol/L (1.5 g/dL) or relevant reduction of units of RBC transfusions by an
absolute number of at least 4 RBC transfusions/8 wk compared with the
pretreatment transfusion number in the previous 8 wk. Only RBC transfusions
given for a Hb of * 5.6 mmol/L (9 g/dL) pretreatment will count in the RBC
transfusion response evaluation. A platelet response is defined as an absolute
increase of * 30 x 109/L for patients starting with >20 x 109/L platelets or an
increase from < 20 x 109/L to > 20 x109/L and by at least 100%. A Neutrophil
response is defined as an at least 100% increase and an absolute increase > 0.5
x 109/L. For these response criteria (erythroid, platelet and neutrophils) the
responses must be at least 8 wk. In the IWG response criteria the pretreatment
Hb should be < 6.8 mmol/L (11 g/dL), the pretreatment platelet count < 100 x
109/L and the neutrophils < 1.0 x 109/L.

Respons will be evaluated after 3 and 12 months. Those patients with a response
after 3 months will be observed; those patients without a response after 3
months will receive re-treatment with the same dose, but infused in the bone
marrow cavity of the left and right spina iliaca post sup (dose and space
escalation). These patients will be evaluated again 3 months after the
re-treatment.
All patients will be followed for a maximum of 2 years after intra-marrow
transplantation.

There is a chance that the disease responds favorably to the direct infusion of
MSCs in the bone marrow cavity. This would allow reduction of the amount of
blood transfusions and infections.

A potential disadvantage of the study could be that the treatment has no
effect despite the patient has undergone the procedure. The administration of
MSC in the bone marrow cavity will presumably, despite optimal pain relief,
still give slight pain. In our experience with direct infusion of autologous
transplants in the bone marrow cavity this pain was well tolerated by our
patients.

On standard evaluation points 3 and 12 months after MSC infusion, additional
blood and bone marrow will be collected for scientific research. For routine
bone marrow examination, bone marrow aspirates will be taken from the left and
right side of the back of the iliac crest. At other moments of evaluation
comparable blood tests will performed as would be done routinely if the patient
did not participate in this study.

The information obtained from this study may, in the future, contribute to a
better treatment of patients with lower risk MDS.