Administration of leukemia-reactive donor T cells after allogeneic stem cell transplantation or donor lymphocyte infusion to patients with persistent or relapsed mature B cell neoplasm with blood and/or bone marrow involvement

Patients with hematological malignancies can be successfully treated with
allogeneic hematopoietic stem cell transplantation (allo-SCT). The aim of this
strategy is to replace the (malignant) hematopoietic system of the patient with
cells of donor origin. The curative potential of this strategy is not solely
caused by the cytoreductive treatment regimen preceding the transplant, but
relies for an important part on the immune responses mediated by immune
effector cells (e.g. T cells and NK cells) of the donor against the
hematopoietic compartment from the patient including the malignant cells. One
of the major challenges in the field of allo-SCT is to find a balance between
the harmful induction of graft-versus-host disease (GvHD) and the beneficial
graft-versus-leukemia/lymphoma (GvL) response, both mediated by donor T cells
recognizing antigens expressed on cells of the recipient. The chance of
inducing GvL and/or GvHD depends on the expression of the targeted antigens on
hematopoietic and/or non-hematopoietic cells.
At the LUMC, allo-SCT is performed using grafts depleted of mature donor T
cells to decrease the risk of inducing severe acute GvHD after transplantation.
This strategy is successful, but obviously limits the induction of GvL
responses, which is reflected by an increased incidence of (early) disease
relapses after T cell depleted allo-SCT. In previous clinical studies we have
shown that delayed application of mature donor T cells by conventional donor
lymphocyte infusions (DLI) 6 months after the T cell depleted allo-SCT results
in GvL responses with limited induction of acute GvHD. Earlier application of
unselected mature donor T cells resulted in the induction of GvHD in a
significant number of patients, thereby limiting the therapeutic applicability
of unselected DLI for the treatment of early relapses occurring in the first
months after the transplant. Moreover, efficient GvL responses after DLI are
most efficiently induced in patients with chronic myeloid leukemia (CML) in
chronic phase, whereas in patients with acute forms of leukemia (e.g. CML in
accelerated phase or blast crisis, acute lymphoblastic leukemia (ALL), or acute
myeloid leukemia (AML)), and in patients with less immunogenic forms of
leukemia, like chronic lymphocytic leukemia (CLL), curative GvL responses are
induced in only a minority of the patients.
In-vitro induction and selection of leukemia-reactive T cells may be an elegant
strategy to overcome the problem of inefficient induction of GvL reactivity
in-vivo and to select for T cells preferentially recognizing the malignant
cells, thereby reducing the likelihood of concurrent development of GvHD.
Previously, we reported the successful treatment of a patient with accelerated
phase CML refractory to DLI who received in-vitro generated leukemia-reactive
donor T cells resulting in a molecular complete remission. However, in this
initial procedure no specific selection step was included, requiring extensive
long-term in-vitro culture to enrich the leukemia-reactive T cells. This
extensive in-vitro culture will hamper the in-vivo potential of the T cells.
Therefore, in the current protocol we select the leukemia-reactive T cells
based on surface expression of an activation marker, allowing us to limit the
required in-vitro culture period. Moreover, the limited immunogenicity of
leukemic cells of some patients hampered the proper in-vitro priming of GvL
responses for these patients. Especially for the B cell malignancies (CLL, ALL,
and mantle cell lymphoma (MCL)) it was observed that in-vitro manipulation was
pivotal to increase the immunogenicity of the malignant B cells. Pre-clinical
work demonstrated that crosslinking of CD40 on the surface of the malignant B
cells resulted in rapid and homogeneous upregulation of costimulatory and
adhesion molecule expression, which significantly increased their
immunogenicity and allowed successful induction of GvL responses in-vitro.
In the current protocol we will test the safety, tolerability and potential
clinical efficacy of adoptive transfer of leukemia-reactive T cells in patients
with relapsed or persistent mature B cell malignancies after allo-SCT or DLI.
Malignant B cells present in peripheral blood or bone marrow samples of the
patient are transformed ex-vivo into antigen-presenting cells (APC) using
cytokines and CD40 crosslinking. Naïve donor T cells will be enriched from a
leukapheresis product by depletion of regulatory T cells (Treg) and activated
memory T cells, and will be stimulated with these malignant APC. Two weeks
after this initial stimulation, the donor T cells will be restimulated with
malignant APC and those T cells that are capable of recognizing the leukemic
cells will be isolated based on their expression of the activation-marker CD137
after restimulation. Since the T cells in this leukemia-reactive T cell product
are selected for reactivity against the hematopoietic (malignant) target cells,
we anticipate that we have skewed the T cell repertoire in the direction of GvL
reactivity, thereby diminishing the risk of inducing GvHD compared to the
infusion of unmodified DLI. The leukemia-reactive T cell product comprises both
cytotoxic CD4 or CD8 positive T cells and helper CD4 or CD8 positive T cells
that do not exert a direct cytotoxic effect but will produce cytokines in
response to stimulation with the malignant cells. Since it will be a combined
response, we will define leukemia-reactivity of the T cells as their capacity
to respond to the leukemic cells as demonstrated by the expression of the
activation marker CD137 upon restimulation. It is anticipated that both cell
types will contribute to the potential clinical effect of the treatment.

- To investigate the feasibility and safety of administration of donor
leukemia-reactive T cells
- To evaluate the persistence of leukemia-reactive T cells after administration
- To evaluate whether administration of leukemia-reactive T cells leads to
complete remission (CR), partial remission (PR) or mixed response (MR) within
12 weeks after last infusion

This is an open-label non-randomized phase I/II feasibility study to administer
leukemia-reactive T cells to 20 patients with persistent or relapsed mature B
cell neoplasm with blood and/or bone marrow involvement at least 3 months after
allo-SCT or DLI, in a maximal dose of 1x10^6 adoptively transferred cells per
kg bodyweight of the patient.
First, malignant cells will be collected from the patient and cryopreserved
under GMP conditions (if no cryopreserved malignant cells are available).
Secondly, a leukapheresis product will be obtained from the donor.
The leukemia-reactive T cells will be generated from the PBMC from the
leukapheresis product as summarized in the investigational medicinal product
chapter of the protocol.
The leukemia-reactive T cells will be administered to the patient when the
product meets the release criteria and the patient has no contraindications for
administration of the cells. When the infusion of the leukemia-reactive T cell
product is well tolerated by the patient, a second product will be generated
and infused 6 weeks later.
Follow-up will be performed until 12 weeks after administration of the last T
cell product or until subsequent DLI, whichever comes first. From then, routine
follow up will be performed.

Leukemia-reactive T cells are a cell therapy product that will be administered
to patients with persistent or relapsed disease from 3 months after allo-SCT or
DLI. The maximal number of T cells that may be administered to the patient is
1x10^6 cells per kg bodyweight of the patient. This number will be determined
in the final leukemia-reactive T cell product after post-isolation expansion.
Post-isolation, the maximal dose of unselected donor T cells of unknown
specificity in case of a related donor will be <=0.3x10^6 per kg bodyweight of
the patient and in case of an unrelated donor <=0.15x10^6/kg per kg bodyweight
of the patient. The cells will be administered intravenously at the department
of Hematology of the Leiden University Medical Center (LUMC) during a clinical
short stay with a maximum of 1 night. In case of contraindications for
administration of leukemia-reactive T cells, administration will be postponed
or cancelled. When the infusion of this leukemia-reactive T cell product is
well tolerated by the patient, a second product will be generated and infused 6
weeks later.

The potential benefit of this treatment will be the induction of a curative
Graft versus Leukemia/Lymphoma effect mediated by the donor T cells recognizing
the malignant cells of the patient. A potential risk may be contaminating
non-leukemia-reactive T cells in the final product, harboring potential GvHD
reactivity.