Haploidentical stem cell transplantation for children with high-risk leukemia

Reconstitution of multifunctional CD56lowCD16low natural killer cell subset in children with acute leukemia given α/β T cell-depleted HLA-haploidentical haematopoietic stem cell transplantation

We recently described the CD56^lowCD16^low subset of Natural Killer (NK) cells that both mediate cytotoxic activity and produce IFNγ, being more abundant in bone marrow (BM) than in peripheral blood (PB) of pediatric normal subjects. Given the multifunctional properties of this subset, we examined its development and functional recovery in a cohort of children undergoing α/β T-cell depleted HLA-haploidentical haematopoietic stem cell transplantation (HSCT). The results obtained indicate that CD56^lowCD16^low NK cells are present in both PB and BM already at one month post-HSCT, with an increased frequency in BM of graft recipients as compared with normal subjects. During the first 6 months after HSCT, no difference in CD56^lowCD16^low NK cells distribution between PB and BM was observed. In comparison to normal subjects, CD56^lowCD16^low NK cells from transplanted patients show lower expression levels of CD25 and CD127 and higher levels of CD122, and accordingly, produce higher amounts of IFNγ after stimulation with IL-12 plus IL-15. The recovery of NK-cell cytotoxicity after HSCT was strictly restricted to CD56^lowCD16^low NK cells, and their ability to degranulate against K562 target cells or autologous leukemic blasts was completely restored only one year after HSCT. Based on the phenotypic and functional ability of reconstituted CD56^lowCD16^low NK cells, we suggest that they play an important role in host defense against leukemia relapse and infections after HSCT, and represent an ideal candidate for approaches of adoptive immunotherapy.

Improving the safety of T-Cell therapies using an inducible caspase-9 gene

Adoptive transfer of T cells can be an effective anticancer treatment. However, uncontrolled or unpredictable immediate or persistent toxic effects are a source of concern. The ability to conditionally eliminate aberrant cells in vivo is therefore becoming a critical step for the successful translation of this approach to the clinic. We review the evolution of safety systems, focusing on a suicide switch that can be expressed stably and efficiently in human T cells without impairing phenotype, function, or antigen specificity. This system is based on the fusion of human caspase-9 to a modified human FK-binding protein, allowing conditional dimerization in the presence of an otherwise bio-inert small molecule drug. When exposed to the synthetic dimerizing drug, the inducible caspase-9 becomes activated, resulting in the rapid apoptosis of cells expressing this construct. We have illustrated the clinical feasibility and efficacy of this approach after haploidentical hematopoietic stem cell transplant. Here we review the benefits and limitations of the approach.

Haploidentical hematopoietic stem cell transplantation without total body irradiation for pediatric acute leukemia: a single-center experience

Hematopoietic stem cell transplantation (HSCT) is a promising method for therapy of pediatric patients with acute leukemia. However, less availability of matched donors limited its wide application. Recently, haploidentical HSCT has become a great resource. Here, we have retrospectively reported our experience of 20 pediatric patients with acute leukemia who underwent haploidentical HSCT without total body irradiation (TBI) myeloablative regimen in our center from November 2007 to June 2014. All the patients attained successful HSCT engraftment in terms of myeloid and platelet recovery. Thirteen patients developed grade I–IV acute graft-versus-host disease (a-GVHD). The incidence of grade I–II a-GVHD, grade III–IV a-GVHD, and chronic GVHD (c-GVHD) was 45%, 20%, and 25%, respectively. The mean myeloid and platelet recovery time was 13.20±2.41 and 19.10±8.37 days. The median follow-up time was 43.95±29.26 months. During the follow-up, three patients died. The overall survival (OS) rate was 85%. The present study indicated that haploidentical HSCT without TBI myeloablative regimen significantly improved the OS rate of pediatric patients with acute leukemia.

Recent advances in haploidentical hematopoietic stem cell transplantation using ex vivo T cell-depleted graft in children and adolescents

Allogeneic hematopoietic stem cell transplantation (HSCT) is a curative treatment for children and adolescents with various malignant and non-malignant diseases. While human leukocyte antigen (HLA)-identical sibling donor is the preferred choice, matched unrelated volunteer donor is another realistic option for successful HSCT. Unfortunately, it is not always possible to find a HLA-matched donor for patients requiring HSCT, leading to a considerable number of deaths of patients without undergoing transplantation. Alternatively, allogeneic HSCT from haploidentical family members could provide donors for virtually all patients who need HSCT. Although the early attempts at allogeneic HSCT from haploidentical family donor (HFD) were disappointing, recent advances in the effective ex vivo depletion of T cells or unmanipulated in vivo regulation of T cells, better supportive care, and optimal conditioning regimens have significantly improved the outcomes of haploidentical HSCT. The ex vivo techniques used to remove T cells have evolved from the selection of CD34⁺ hematopoietic stem cell progenitors to the depletion of CD3⁺ cells, and more recently to the depletion of αβ⁺ T cells. The recent emerging evidence for ex vivo T cell-depleted haploidentical HSCT has provided additional therapeutic options for pediatric patients with diseases curable by HSCT but has not found a suitable related or unrelated donor. This review discusses recent advances in haploidentical HSCT, focusing on transplant using ex vivo T cell-depleted grafts. In addition, our experiences with this novel approach for the treatment of pediatric patients with malignant and non-malignant diseases are described.

Inducible caspase-9 suicide gene controls adverse effects from alloreplete T cells after haploidentical stem cell transplantation

To test the feasibility of a single T-cell manipulation to eliminate alloreactivity while sparing antiviral and antitumor T cells, we infused 12 haploidentical hematopoietic stem cell transplant patients with increasing numbers of alloreplete haploidentical T cells expressing the inducible caspase 9 suicide gene (iC9-T cells). We determined whether the iC9-T cells produced immune reconstitution and if any resultant graft-versus-host disease (GVHD) could be controlled by administration of a chemical inducer of dimerization (CID; AP1903/Rimiducid). All patients receiving >10(4) alloreplete iC9-T lymphocytes per kilogram achieved rapid reconstitution of immune responses toward 5 major pathogenic viruses and concomitant control of active infections. Four patients received a single AP1903 dose. CID infusion eliminated 85% to 95% of circulating CD3(+)CD19(+) T cells within 30 minutes, with no recurrence of GVHD within 90 days. In one patient, symptoms and signs of GVHD-associated cytokine release syndrome (CRS-hyperpyrexia, high levels of proinflammatory cytokines, and rash) resolved within 2 hours of AP1903 infusion. One patient with varicella zoster virus meningitis and acute GVHD had iC9-T cells present in the cerebrospinal fluid, which were reduced by >90% after CID. Notably, virus-specific T cells recovered even after AP1903 administration and continued to protect against infection. Hence, alloreplete iC9-T cells can reconstitute immunity posttransplant and administration of CID can eliminate them from both peripheral blood and the central nervous system (CNS), leading to rapid resolution of GVHD and CRS. The approach may therefore be useful for the rapid and effective treatment of toxicities associated with infusion of engineered T lymphocytes. This trial was registered at www.clinicaltrials.gov as #NCT01494103.

Different aspects of stem cell procedures in children with poor responding AML: when is HSCT the best answer?

Acute myeloid leukemia in children is a heterogeneous disease with different morphological and cytogenetic features. New diagnostic tools and treatments, improved supportive care and the use of genomic tissue typing in selecting donors for hematopoietic stem cell transplantation (HSCT) adds to increased survival rates. Candidates to HSCT in first complete remission are patients with cytogenetic or molecular unfavorable prognostic markers, or blasts >15% after first induction. The use of minimal residual disease can also identify children benefiting from HSCT in first complete remission and the patients post HSCT with signs of relapse. The outcome and cure rate of acute myeloid leukemia, still remains poor and new diagnostic tools and treatments strategies need to be evaluated. In this management perspective, future management of novel minimal residual disease tools are discussed, conditioning therapies, as well as different transplantation procedures including haplo-transplantation and haplo-identical natural killer cell transplantation, but also altered graft-versus-host-disease treatments.

Unrelated cord blood compared with haploidentical grafts in patients with hematological malignancies

BACKGROUND

Alternative donors, such as unrelated umbilical cord blood (UCB) and related haploidentical (haplo) donors, are more and more frequently searched for and used for patients who are candidates for allogeneic hematopoietic stem cell transplantation but are without a suitable related or unrelated donor. The aim of the current retrospective study was to compare the outcome of patients after haplo and UCB grafts prepared using a nonmyeloablative conditioning regimen.

METHODS

A total of 150 adult patients with high-risk hematologic diseases who underwent allogeneic hematopoietic stem cell transplantation from alternative donors at 2 centers (Paoli-Calmettes Institute [Marseille, France] and Humanitas Cancer Center [Milan, Italy]) were analyzed. Sixty-nine patients had haplo donors and 81 patients had UCB donors.

RESULTS

The cumulative incidence of nonrecurrence mortality at 1 year was 23% in the UCB group versus 17% in the haplo group (P = .39). The incidence of grade 2 to 4 acute graft-versus-host disease and extensive chronic graft-versus-host disease in the UCB group versus the haplo group was 52% versus 29% (P = .05) and 12% versus 6% (P<.0001), respectively. The overall survival rate at 2 years was 45% in the UCB group (95% confidence interval [95% CI], 34%-56%) versus 69% in the haplo group (95% CI, 58%-80%) (P = .10). The progression-free survival rate at 2 years was 36% in the UCB group (95% CI, 25%-47%) versus 65% in the haplo group (95% CI, 53%-77%) (P = .01).

CONCLUSIONS

The results of the current study suggest that for patients with high-risk hematological diseases without a related or unrelated donor, haploidentical transplants are a promising alternative option that deserves further investigation.

A critical review of which children with acute myeloid leukaemia need stem cell procedures

The last decades have seen parallel improvements in chemotherapy-based and haematopoietic stem cell transplantation (HSCT) regimens for acute myeloid leukaemia (AML) in children. There has been no consensus on indication for HSCT. Reserving HSCT for high-risk and relapsed patients spare many patients from the long-term toxicity of this treatment. The results of matched unrelated donor HSCT equal family donor transplantation and the presence of a matched sibling should no longer be a transplant indication. Minimal residual disease measured by flow cytometry may identify poor responders benefitting from HSCT in first complete remission (CR1) and those with a favourable response to induction therapy who do not need HSCT even with adverse cytogenetic aberrations. FLT3-internal tandem duplication without NPM1 mutation has a very high relapse rate despite favourable response and HSCT is indicated in CR1 in these cases. Finding the optimal indications for HSCT is a delicate balance between risk of relapse and late effects.

Long-term outcome after haploidentical stem cell transplant and infusion of T cells expressing the inducible caspase 9 safety transgene

Adoptive transfer of donor-derived T lymphocytes expressing a safety switch may promote immune reconstitution in patients undergoing haploidentical hematopoietic stem cell transplant (haplo-HSCT) without the risk for uncontrolled graft versus host disease (GvHD). Thus, patients who develop GvHD after infusion of allodepleted donor-derived T cells expressing an inducible human caspase 9 (iC9) had their disease effectively controlled by a single administration of a small-molecule drug (AP1903) that dimerizes and activates the iC9 transgene. We now report the long-term follow-up of 10 patients infused with such safety switch-modified T cells. We find long-term persistence of iC9-modified (iC9-T) T cells in vivo in the absence of emerging oligoclonality and a robust immunologic benefit, mediated initially by the infused cells themselves and subsequently by an apparently accelerated reconstitution of endogenous naive T lymphocytes. As a consequence, these patients have immediate and sustained protection from major pathogens, including cytomegalovirus, adenovirus, BK virus, and Epstein-Barr virus in the absence of acute or chronic GvHD, supporting the beneficial effects of this approach to immune reconstitution after haplo-HSCT. This study was registered at www.clinicaltrials.gov as #NCT00710892.

Optimal stem cell source for allogeneic stem cell transplantation for hematological malignancies

Hematopoietic stem cell transplant (HSCT) is a standard treatment for many hematological malignancies. Three different sources of stem cells, namely bone marrow (BM), peripheral blood stem cells (PBSC) and cord blood (CB) can be used for HSCT, and each has its own advantages and disadvantages. Randomized controlled trials (RCTs) suggest that there is no significant survival advantage of PBSC over BM in Human Leukocyte Antigen-matched sibling transplant for adult patients with hematological malignancies. PBSC transplant probably results in lower risk of relapse and hence better disease-free survival, especially in patients with high risk disease at the expense of higher risks of both severe acute and chronic graft-versus-host disease (GVHD). In the unrelated donor setting, the only RCT available suggests that PBSC and BM result in comparable overall and disease-free survivals in patients with hematological malignancies; and PBSC transplant results in lower risk of graft failure and higher risk of chronic GVHD. High level evidence is not available for CB in comparison to BM or PBSC. The risks and benefits of different sources of stem cells likely change with different conditioning regimen, strategies for prophylaxis and treatment of GVHD and manipulation of grafts. The recent success and rapid advance of double CB transplant and haploidentical BM and PBSC transplants further complicate the selection of stem cell source. Optimal selection requires careful weighing of the risks and benefits of different stem cell source for each individual recipient and donor. Detailed counseling of patient and donor regarding risks and benefits in the specific context of the patient and transplant method is essential for informed decision making.

Relapsed childhood acute lymphoblastic leukaemia

With steadily improved cure rates for children with newly diagnosed acute lymphoblastic leukaemia (ALL), treating relapsed ALL has become increasingly challenging largely due to resistance to salvage therapy. Improved biological understanding of mechanisms of relapse and drug resistance, the identification of actionable molecular targets by studying leukaemic cell and host genetics, precise risk stratification with minimum residual disease measurement, and the development of new therapeutic drugs and approaches are needed to improve outcomes of relapsed patients. Molecularly targeted therapies and innovative immunotherapeutic approaches that include specialised monoclonal antibodies and cellular therapies hold promise of enhanced leukaemia cell killing with non-overlapping toxicities. Advances in preparative regimens, donor selection, and supportive care should improve the success of haemopoietic stem-cell transplantation for high-risk patients.

New approaches to graft engineering for haploidentical bone marrow transplantation

Haploidentical transplantation opens the possibility to offer this treatment to a large number of patients with an otherwise incurable disease, such as some hematologic or oncologic malignancies, inborn or acquired bone marrow failure syndromes, hemoglobinopathies, immunodeficiencies, or other genetic diseases. Initial attempts at haploidentical transplantation using unmanipulated bone marrow were associated with a high transplant-related mortality. However, recent insights into the biology of haploidentical transplantation, the availability of effective in vivo large-scale graft-manipulation technology, and improved supportive care strategies have led to and are still leading to significantly better outcomes compared to previous decades. Methods for the in vitro depletion of T lymphocytes from mobilized peripheral blood stem cells (PBSC) to prevent graft-versus-host disease (GvHD) have facilitated the wider use and acceptance of haploidentical transplantation in children and adult patients. Besides in vitro T-cell depletion techniques, other methods, such as the isolation of alloreactive natural killer (NK) cells, virus-specific T lymphocytes, and other effector or regulatory cells are nowadays available to rapidly rebuild the immune system after haploidentical transplantation for the prevention of severe infections or relapses of the underlying diseases.

Global challenges in pediatric oncology

PURPOSE OF REVIEW

Reduction of child mortality is one of the Millennium Development Goals; as low-income and middle-income countries (LMICs) advance toward the achievement of this goal, initiatives aimed at reducing the burden of noncommunicable diseases, including childhood cancer, need to be developed.

RECENT FINDINGS

Approximately 200 000 children and adolescents are diagnosed with cancer every year worldwide; of those, 80% live in LMICs, which account for 90% of the deaths. Lack of quality population-based cancer registries in LMICs limits our knowledge of the epidemiology of pediatric cancer; however, available information showing variations in incidence may indicate unique interactions between environmental and genetic factors that could provide clues to cause. Outcome of children with cancer in LMICs is dictated by late presentation and underdiagnosis, high abandonment rates, high prevalence of malnutrition and other comorbidities, suboptimal supportive and palliative care, and limited access to curative therapies. Initiatives integrating program building with education of healthcare providers and research have proven to be successful in the development of regional capacity. Intensity-graduated treatments adjusted to the local capacity have been developed.

SUMMARY

Childhood cancer burden is shifted toward LMICs; global initiatives directed at pediatric cancer care and control are urgently needed. International partnerships facilitating stepwise processes that build capacity while incorporating epidemiology and health services research and implementing intensity-graduated treatments have been shown to be effective.

Immune reconstitution and strategies for rebuilding the immune system after haploidentical stem cell transplantation

Haploidentical hematopoietic stem cell transplantation is a curative alternative option for patients without an otherwise suitable stem cell donor. In order to prevent graft-versus-host disease (GvHD), different in vitro and in vivo T cell-depletion strategies have been developed. A delayed immune reconstitution is common to all these strategies, and an impaired immune function after haploidentical transplantation with subsequent infections is a major cause of deaths in these patients. In addition to in vitro and in vivo T cell-depletion methods, posttransplant strategies to rapidly rebuild the immune system have been introduced in order to improve the outcome. Advances in in vitro and in vivo T cell-depletion methods, and adoptive transfer of immune cells of the innate and specific immune system, will contribute to reduce the risk of GvHD, lethal infections, and the risk of relapse of the underlying malignant disease.