A Phase l/ll study to assess safety of co-infusion of haematopoietic stem cells from a haplo-identical donor and single unit unrelated cord blood in patients with a high risk of relapse

Although haematopoietic stem cells transplantation (HSCT) has become much safer
over the last decade the major limitation remain *transplantation related
mortality (TRM; e.g. due to viral reactivations/graft versus host disease)* and
relapse (in malignancies). Cord blood (CB) is emerging as stem cell source for
HSCT because it has many advantages above the conventional bone marrow grafts.
Disadvantages are however low stem cell count/kg for adults associated with
prolonged neutropenia and a slower T cell recovery. Haplo-grafts have the
advantage of early neutrophil engraftment but are associated with high rates of
secondary graft-failure and poor T-cell reconstitution associated with viral
infections.

Combining cord blood and readily available haplo-identical family donor-HSCT
combines beneficial effects of both allogenic transplantations strategies, such
as the in the long term excellent T-cell recovery after CB HSCT, and the
NK-cell mediated anti-tumor activity of CB with the early haplo-mediated
neutrophil recovery and the targeted anti-leukemia effect of NK (KIR mismatch)
and **T-cells after selected haplo-HSCT. We propose therefore that this
multimodal treatment protocol will be a preferable treatment option in a
selected group of high risk patients, for different reasons, with either
non-malignant or malignant indications who may profit for various reasons from
this double grafting:
1) Early neutrophil recovery (patients with ongoing infection)
2) Swift (early / fast haplo-engraftment) and secure (CB-engraftment) in
patients with difficult engraftment and ongoing disease: such as hemophagocytic
lymphohistiocytosis (HLH) and osteopetrosis as well as patients without a well
matched unrelated marrow/PBSC donor or cord blood donor with a sufficient
number of nucleated cells available.
3) Multi-modal cellular therapy: Strong early (first 2-4 weeks) NK + **T-cells
mediated (anti-tumor/ antiviral) activity from the haplo-graft and NK + **T-
cellular activity (> 4 weeks) from the CB-graft without increasing the risk of
aGVHD (high risk lymphoma / leukaemia patients without standard SCT-protocol).

Phase l-ll safety study on the development of a multimodal treatment protocol
combining the advantages of CB with the advantages of haploidentical stem cells
in a group HSCT requiring patients with an estimated high risk of transplant
related mortality

1) Co-infusion of haplo-identical hemopoietic stem cells from a third party
donor will reduce the neutropenic period (<14d) without being associated with
an increase of transplant related complications, and will result in sustained
full cord blood donor chimerism. It would make HSCT safer in patients with
ongoing infection and would make cord blood transplantation an attractive
option for more adult patients.
2) Boost the anti-tumor/anti-viral effect by implementing a multi-modal
cellular therapy by combining the allo-reactive NK-cells and **-cells from the
haplo-graft with NK-cells and T-cells from the CB graft. To obtain this, the
haplograft is purified by TCR**- and CD19-negative selection with conservation
of innate cells such as NK cells and **T-cells, while depleting ** Tcells and
B cells.

It is a single center study within the UMC Utrecht, including both adult and
pediatric patients with and indication for allo-SCT. Patients will be included
during a period of 3 years. According to Simon et al. (Optimal two-stage
designs for phase II clinical trials) it was estimated that a minimum of 21 and
a maximum of 43 have to be included. To our opinion in 3 years time a number of
43 should be feasible.

For all patients with an indication for allogenic HSCT, the best treatment
option is discussed in a multidisciplinary meeting. This treatment protocol
will be considered as one of the options for eligible patients. When considered
the best option, the treatment proposal is discussed with the patient/ parents.
Informed consent has to be obtained both for HSCT itself, for immune
reconstitution studies, and for the Cord+ Haplo HSCT protocol.
If informed consent is obtained, the best CB unit is ordered. After apheresis
or bone-marrow harvest of the haplo-donor graft, the cells are purified by the
SCT lab using negative selection with anti-TCR**- and CD19-microbeads.
Just prior to transplant the Cord blood unit is thawed and infused immediately
thereafter, followed by infusion of the selected haplo-cells. All other
treatment, both in- and outpatient care is the same as it is for other
allogenic HSCT patients.
CRFs are filled out by the responsible doctors of the SCT ward and outpatient
clinic on day 0; +1; +3; +10 days; +2 wks, +4 wks, +6 wks, + 8 wks, + 10 wks,
+12 wks: +100 dys; +4 months; +5 months; +6 months, +9 months, +1 year.

Main outcome parameters of this safety trial are aGVHD and TRM. Stopping rules
on the two outcome parameters have been defined , implying an interim analysis
of TRM after the first 100 days of the first 11 patients and of the cumulative
incidence of aGVHD after the first 100 days of the first 15 patients. In line
with Simon the trial will be discontinued early if *5 out of 11 patients died
of TRM or if * 7 out of 15 patients have aGvHD grade 2-4.

The intervention applies to the selection of the donor source and preparation
of the grafts.

1) combining a cord blood unit with a minimum of > 1,5 x 10E7 NC/kg with
coinfused cells form a haplo-identical familydonor
2) preference of a KIR mismatch between haplodonor and recipient for recipients
with a malignant indication for HSCT (see protocol)
3) selection of the haplograft purified by TCR**- and CD19-negative selection
leaving in the graft:
-5 x 10 E6/kg CD34+ /kg (in case of difficult apheresis minimum of 2.5 x
10E6/kg).
-Maximum number of T cells < 5x 10 E4/kg.
-NK cells and gamma delta T cells for extra antiviral and anti-tumor activity

4) Using conditioning regimens without ATG. This is explained on page 18 of
the protocol under "Safety of infusion of innate immune cells".

.

Potential Risks
1) possible increased risk of aGVHD because of using donor cells from an
additional donor and because of coinfusion of NK cells and gamma deltacells
instead of mere Cd34+ cells.
It is however (see protocol) unlikely that coinfusion of CD34+ cells with NK
and **T *cells in our protocol will result in an increase in > aGVHD gr ll in
comparison to the cord- haplo with CD34+ positive selection or general MUD or
uCB HSCT (patient outcome review WKZ). This is particularly true in this high
risk group of patients, in which the expected GVHD and TRM are already higher
on the basis of lower lansky scores, underlying disease or suboptimal donors
available. [32, 33] Patient outcome review WKZ 2009). Stopping rules have been
applied to asses an eventuel unacceptable increased cumulative incidence of
aGVHD.
2)possible increased risk of cGVHD
As the effects of the haplodonor cells are only temporary, it is unlikely that
this protocol will lead to a higher incidence of cGVHD. However, in case of an
increase in aGVHD the cumulative incidence of cGVHD is also increased by
triggerd alloreactivity and tissue damage triggering new alloreactivity.
3) engraftment syndrome.
with increased engraftment rate and fast recovery of neutrophils there is an
increased risk of engraftment syndrome.

Potential Benefits
1) lower TRM and longer event free survival
By swift and secure engraftment, and hopefully less relapse due to NK- and
gammadelta T-cell activity.
2)possible lower risk of aGVHD and cGVHD
By decreasing the risk of infection and associated tissue damage and triggered
alloreactivity
3) creating a platform for future studies: further development of selection
and expansion of specific cell fractions (such as gamma delta T cells, T regs,
or modified T cell populations with specific anti-tumor/antiviral activity)
and use them for immune interventions at specific time points when needed.