HLA-mismatched stem-cell microtransplantation as postremission therapy for acute myeloid leukemia: long-term follow-up

Harnessing allogeneic CD4+ T cells to reinvigorate host endogenous antitumor immunity

Immune checkpoint blockade (ICB) therapies developed over the past decade have been among the most promising approaches for the treatment of patients with advanced cancers. However, the overall objective response rate of ICB therapy for various cancers remains insufficient. Hence, novel strategies are required to improve the efficacy of immunotherapy for advanced cancers. The graft-versus-tumor (GVT) effect, which reflects strong antitumor immunity, is known to occur after allogeneic hematopoietic stem cell transplantation (HSCT). The GVT effect is mainly caused by transplanted donor lymphocytes that recognize and react to distinct alloantigens on tumor cells. In contrast, transplanted allogeneic cells can, in some instances, induce endogenous antitumor immunity in recipients if the graft has been rejected. Because of this ability, allogeneic cells have also been used to induce endogenous antitumor immunity without HSCT, and their beneficial immune response is referred to as the "allogenic effect." Here, we review the usefulness of allogeneic cells, particularly allogeneic CD4+ T cells, in cancer immunotherapy by highlighting their unique potential to induce host endogenous antitumor immunity.

Expert consensus on microtransplant for acute myeloid leukemia in elderly patients -report from the international microtransplant interest group

Recent studies have shown that microtransplant (MST) could improve outcome of patients with elderly acute myeloid leukemia (EAML). To further standardize the MST therapy and improve outcomes in EAML patients, based on analysis of the literature on MST, especially MST with EAML from January 1st, 2011 to November 30th, 2022, the International Microtransplant Interest Group provides recommendations and considerations for MST in the treatment of EAML. Four major issues related to MST for treating EAML were addressed: therapeutic principle of MST (1), candidates for MST (2), induction chemotherapy regimens (3), and post-remission therapy based on MST (4). Others included donor screening, infusion of donor cells, laboratory examinations, and complications of treatment.

Measurable residual disease study through three different methods can anticipate relapse and guide pre-emptive therapy in childhood acute myeloid leukemia

PURPOSE

Although outcomes of children with acute myeloid leukemia (AML) have improved over the last decades, around one-third of patients relapse. Measurable (or minimal) residual disease (MRD) monitoring may guide therapy adjustments or pre-emptive treatments before overt hematological relapse.

METHODS

In this study, we review 297 bone marrow samples from 20 real-life pediatric AML patients using three MRD monitoring methods: multiparametric flow cytometry (MFC), fluorescent in situ hybridization (FISH) and polymerase chain reaction (PCR).

RESULTS

Patients showed a 3-year overall survival of 73% and a 3-year event-free survival of 68%. Global relapse rate was of 25%. All relapses were preceded by the reappearance of MRD detection by: (1) MFC (p = 0.001), (2) PCR and/or FISH in patients with an identifiable chromosomal translocation (p = 0.03) and/or (3) one log increase of Wilms tumor gene 1 (WT1) expression in two consecutive samples (p = 0.02). The median times from MRD detection to relapse were 26, 111, and 140 days for MFC, specific PCR and FISH, and a one log increment of WT1, respectively.

CONCLUSIONS

MFC, FISH and PCR are complementary methods that can anticipate relapse of childhood AML by weeks to several months. However, in our series, pre-emptive therapies were not able to prevent disease progression. Therefore, more sensitive MRD monitoring methods that further anticipate relapse and more effective pre-emptive therapies are needed.

Hyper-CVAD-Based Stem Cell Microtransplant as Post-Remission Therapy in Acute Lymphoblastic Leukemia

Post-remission strategies for patients with acute lymphoblastic leukemia (ALL) are limited to the multiagent chemotherapy and allogeneic stem cell transplant (allo-SCT), and cellular therapies are seldom involved. Although chemotherapy combined with mismatched granulocyte colony-stimulating factor mobilized peripheral blood mononuclear cell infusion (microtransplant, MST) has been studied in patients with acute myeloid leukemia, its efficacy in ALL is still undetermined. We enrolled 48 patients receiving hyper-CVAD-based MST between July 1, 2009, and January 31, 2018. No acute or chronic graft-versus-host disease occurred in patients receiving MST. Four-year overall survival (OS) and leukemia-free survival (LFS) were 62% and 35%, respectively, and the 4-year relapse rate was 65%. No patient experienced non-relapse mortality. Subgroup analysis showed that OS rates were comparable between groups with different age, risk stratification, minimal residual disease status prior to MST and immunophenotype. Adult patients tended to achieve better 4-year LFS (62% vs. 26%, P = .058) and lower hematologic relapse rate (38% vs. 74%, P = .058) compared with adolescent and young adult patients. Donor chimerism/microchimerism was detectable ranging from 0.002% to 42.78% in 78% (42/54) available samples within 14 days after each infusion and at 3 months or one year after the last cell infusion. Multivariate analyses demonstrated that white blood cells <30 × 109/L at diagnosis and sufficient hyper-CVAD cycles were prognostic factors for better 4-year OS and LFS, while the B-cell phenotype and higher number of infused CD34+ cells in the first cycle were predictors for favorable 4-year LFS. The hyper-CVAD-based MST was a feasible strategy for treating ALL patients with mild toxicity.

Case report: Rare persistent complete donor chimerism and GVHD following micro-transplantation from HLA haplotype homozygous donors

HLA-mismatched hematopoietic stem cell micro-transplantation (MST) is an effective treatment for older patients (≥60 years) with acute myeloid leukemia. Donor selection for MST is broad, ranging from HLA fully mismatched unrelated donors to HLA partially matched related donors. However, the influence of HLA haplotype homozygous donors such donors on MST has not been studied. Such donors has been reported to be associated with a higher risk of graft-versus-host disease (GVHD) in transfusion and cord blood transplantation (CBT). Additionally, sustained complete donor chimerism is rare in MST and usually accompanied by severe acute GVHD and death. Herein, we report the first case of MST using an HLA haplotype homozygous donor. The patient developed persistent complete donor chimerism (donor cells&gt;95%) for 7 months and prolonged isolated thrombocytopenia (PT) for 3 months, after receiving MST from his HLA homozygous son. Grade I acute GVHD presented on day 12 post-MST and it was controlled by timely immunosuppressive treatment. Then he maintained complete molecular remission, complete donor chimerism and mild GVHD for 5 months. However, moderate overlapping GVHD with skin, oral, eyes, and intestinal involvement developed after he self-discontinued Tacrolimus treatment. Fortunately, the GVHD was controlled after intensive anti-rejection therapy and Tacrolimus is now being continued for prophylaxis. This case underscores that HLA haplotype homozygous donors might not be a good choice for MST and GVHD prophylactic should be administrated if such donors have to be selected.

The clinical application of SNP-based next-generation sequencing (SNP-NGS) for evaluation of chimerism and microchimerism after HLA-mismatched stem cell microtransplantation

Genetic diagnostic methods for evaluation of chimerism after HSCT, such as STR-PCR and XY-FISH, have limited sensitivity. When donor chimerism is in the micro range (< 1%), deviations in the accuracy of assessment are the most significant disadvantage of these common methods. We developed a highly sensitive method that applies SNPs based on NGS in order to explore the value of donor cell microchimerism in microtransplantation (MST). This improved SNP-NGS approach has higher sensitivity (0.01–0.05%) and only requires a small amount of DNA (8–200 ng). We retrospectively analyzed the clinical data of 48 patients with AML who received HLA-mismatched stem cell MST at our center to assess the impact of microchimerism on clinical prognosis. Patients whose duration of microchimerism was > 10.5 months (median) had a relapse rate of 26.1%, and had better 5-year LFS and OS (73.4% and 82.6%). In contrast, patients whose duration of microchimerism was < 10.5 months had a higher relapse rate (69.6%), and their 5-year LFS and OS were 30.4% and 43.5%. In conclusion, duration of donor chimerism is highly valuable for assessment of survival and prognosis in patients with AML who have received HLA-mismatched stem cell MST, especially the intermediate-risk group.

Microtransplantation for myeloid sarcoma: Two case reports

Myeloid sarcoma (MS), is a rare extramedullary tumor with a poor prognosis and high recurrence rate. Microtransplantation is one of the alternative methods of traditional transplantation, which does not rely on HLA complete matching, has low toxicity and may retain part of graft-versus-leukemia (GVL) effect. It has been reported that microtransplantation can significantly improve the survival rate of elderly AML patients. At present, there is no report on the application of micro transplantation in MS. We will report two cases of MS treated by micro transplantation. The disease-free survival was 66 months and 55 months respectively.

Non-Ablative Chemotherapy Followed by HLA-Mismatched Allogeneic CD3+ T-Cells Infusion Causes An Augment of T-Cells With Mild CRS: A Multi-Centers Single-Arm Prospective Study on Elderly Acute Myeloid Leukemia and int-2/High Risk Myelodysplastic Syndrome Patients

Objective

To evaluate the efficacy and safety of standard or low-dose chemotherapy followed by HLA-mismatched allogeneic T-cell infusion (allo-TLI) for the treatment of elderly patients with acute myeloid leukemia (AML) and patients with intermediate-2 to high-risk myelodysplastic syndrome (MDS).

Methods

We carried out a prospective, multicenter, single-arm clinical trial. Totally of 25 patients were enrolled, including 17 AML patients and 8 MDS patients. Each patient received four courses of non-ablative chemotherapy, with HLA-mismatched donor CD3⁺ allo-TLI 24 h after each course. AML patients received chemotherapy with decitabine, idarubicin, and cytarabine, and MDS patients received decitabine, cytarabine, aclarubicin, and granulocyte colony-stimulating factor.

Results

A total of 79 procedures were performed. The overall response rates of the AML and MDS patients were 94% and 75% and the 1-year overall survival rates were 88% (61-97%) and 60% (13-88%), respectively. The overall 60-day treatment-related mortality was 8%. Compared with a historical control cohort that received idarubicin plus cytarabine (3 + 7), the study group showed significantly better overall response (94% vs. 50%, P=0.002) and overall survival rates (the 1-year OS rate was 88% vs. 27%, P=0.014). Post-TLI cytokine-release syndrome (CRS) occurred after 79% of allo-TLI operations, and 96% of CRS reactions were grade 1.

Conclusion

Elderly AML patients and intermediate-2 to high-risk MDS patients are usually insensitive to or cannot tolerate regular chemotherapies, and may not have the opportunity to undergo allogeneic stem cell transplantation. Our study showed that non-ablative chemotherapy followed by HLA-mismatched allo-TLI is safe and effective, and may thus be used as a first-line treatment for these patients.

Clinical Trial Registration

https://www.chictr.org.cn/showproj.aspx?proj=20112.

Alloantigen-activated (AAA) CD4+ T cells reinvigorate host endogenous T cell immunity to eliminate pre-established tumors in mice

BACKGROUND

Cancer vaccines that induce endogenous antitumor immunity represent an ideal strategy to overcome intractable cancers. However, doing this against a pre-established cancer using autologous immune cells has proven to be challenging. "Allogeneic effects" refers to the induction of an endogenous immune response upon adoptive transfer of allogeneic lymphocytes without utilizing hematopoietic stem cell transplantation. While allogeneic lymphocytes have a potent ability to activate host immunity as a cell adjuvant, novel strategies that can activate endogenous antitumor activity in cancer patients remain an unmet need. In this study, we established a new method to destroy pre-developed tumors and confer potent antitumor immunity in mice using alloantigen-activated CD4⁺ (named AAA-CD4⁺) T cells.

METHODS

AAA-CD4⁺ T cells were generated from CD4⁺ T cells isolated from BALB/c mice in cultures with dendritic cells (DCs) induced from C57BL/6 (B6) mice. In this culture, allogeneic CD4⁺ T cells that recognize and react to B6 mouse-derived alloantigens are preferentially activated. These AAA-CD4⁺ T cells were directly injected into the pre-established melanoma in B6 mice to assess their ability to elicit antitumor immunity in vivo.

RESULTS

Upon intratumoral injection, these AAA-CD4⁺ T cells underwent a dramatic expansion in the tumor and secreted high levels of IFN-γ and IL-2. This was accompanied by markedly increased infiltration of host-derived CD8⁺ T cells, CD4⁺ T cells, natural killer (NK) cells, DCs, and type-1 like macrophages. Selective depletion of host CD8⁺ T cells, rather than NK cells, abrogated this therapeutic effect. Thus, intratumoral administration of AAA-CD4⁺ T cells results in a robust endogenous CD8⁺ T cell response that destroys pre-established melanoma. This locally induced antitumor immunity elicited systemic protection to eliminate tumors at distal sites, persisted over 6 months in vivo, and protected the animals from tumor re-challenge. Notably, the injected AAA-CD4⁺ T cells disappeared within 7 days and caused no adverse reactions.

CONCLUSIONS

Our findings indicate that AAA-CD4⁺ T cells reinvigorate endogenous cytotoxic T cells to eradicate pre-established melanoma and induce long-term protective antitumor immunity. This approach can be immediately applied to patients with advanced melanoma and may have broad implications in the treatment of other types of solid tumors.

Adoptive immunotherapy with CB following chemotherapy for patients with refractory myeloid malignancy: chimerism and response

We conducted a prospective evaluation of cord blood (CB)-derived adoptive cell therapy, after salvage chemotherapy, for patients with advanced myeloid malignancies and poor prognosis. Previously, we reported safety, feasibility, and preliminary efficacy of this approach. We present updated results in 31 patients who received intensive chemotherapy followed by CB infusion and identify predictors of response. To enhance the antileukemic effect, we selected CB units (CBU) with shared inherited paternal antigens and/or noninherited maternal antigens with the recipients. Twenty-eight patients with acute myeloid leukemia (AML), 2 with myelodysplastic syndrome, and 1 in chronic myeloid leukemia myeloid blast crisis were enrolled; 9 had relapsed after allogeneic transplant. Response was defined as <5% blasts in hypocellular bone marrow at 2 weeks after treatment. Thirteen patients (42%) responded; a rate higher than historical data with chemotherapy only. Twelve had CBU-derived chimerism detected; chimerism was a powerful predictor of response (P < .001). CBU lymphocyte content and a prior transplant were associated with chimerism (P < .01). Safety was acceptable: 3 patients developed mild cytokine release syndrome, 2 had grade 1 and 2 had grade 4 graft-versus-host disease. Seven responders and 6 nonresponders (after additional therapy) received subsequent transplant; 5 are alive (follow-up, 5-47 months). The most common cause of death for nonresponders was disease progression, whereas for responders it was infection. CB-derived adoptive cell therapy is feasible and efficacious for refractory AML. Banked CBU are readily available for treatment. Response depends on chimerism, highlighting the graft-versus-leukemia effect of CB cell therapy. This trial was registered at www.clinicaltrials.gov as #NCT02508324.

HLA-mismatched allogeneic adoptive immune therapy in severely immunosuppressed AIDS patients

Severely immunosuppressed AIDS patients with recurrent opportunistic infections (OIs) represent an unmet medical need even in the era of antiretroviral therapy (ART). Here we report the development of a human leukocyte antigen (HLA)-mismatched allogeneic adaptive immune therapy (AAIT) for severely immunosuppressed AIDS patients. Twelve severely immunosuppressed AIDS patients with severe OIs were enrolled in this single-arm study. Qualified donors received subcutaneous recombinant granulocyte-colony-stimulating factor twice daily for 4-5 days to stimulate hematopoiesis. Peripheral blood mononuclear cells were collected from these donors via leukapheresis and transfused into the coupled patients. Clinical, immunological, and virological parameters were monitored during a 12-month follow-up period. We found AAIT combined with ART was safe and well-tolerated at the examined doses and transfusion regimen in all 12 patients. Improvements in clinical symptoms were evident throughout the study period. All patients exhibited a steady increase of peripheral CD4+ T cells from a median 10.5 to 207.5 cells/μl. Rapid increase in peripheral CD8+ T-cell count from a median 416.5 to 1206.5 cells/μl was found in the first 90 days since initiation of AAIT. In addition, their inflammatory cytokine levels and HIV RNA viral load decreased. A short-term microchimerism with donor cells was found. There were no adverse events associated with graft-versus-host disease throughout the study period. Overall, AAIT treatment was safe, and might help severely immunosuppressed AIDS patients to achieve a better immune restoration. A further clinical trial with control is necessary to confirm the efficacy of AAIT medication.

Chimerism, the Microenvironment and Control of Leukemia

Transplantation of allogeneic hematopoietic cells faces two barriers: failure of engraftment due to a host versus graft reaction, and the attack of donor cells against the patient, the graft versus host (GVH) reaction. This reaction may lead to GVH disease (GVHD), but in patients transplanted due to leukemia or other malignant disorders, this may also convey the benefit of a graft versus leukemia (GVL) effect. The interplay of transplant conditioning with donor and host cells and the environment in the patient is complex. The microbiome, particularly in the intestinal tract, profoundly affects these interactions, directly and via soluble mediators, which also reach other host organs. The microenvironment is further altered by the modifying effect of malignant cells on marrow niches, favoring the propagation of the malignant cells. The development of stable mixed donor/host chimerism has the potential of GVHD prevention without necessarily increasing the risk of relapse. There has been remarkable progress with novel conditioning regimens and selective T-cell manipulation aimed at securing engraftment while preventing GVHD without ablating the GVL effect. Interventions to alter the microenvironment and change the composition of the microbiome and its metabolic products may modify graft/host interactions, thereby further reducing GVHD, while enhancing the GVL effect. The result should be improved transplant outcome.

Decitabine With or Without Micro-Transplantation for the Treatment of Intermediate or High-Risk Myelodysplastic Syndrome: A Chinese Single-Center Retrospective Study of 22 Patients

The treatment outcomes of intermediate or high-risk myelodysplastic syndrome (MDS) remain unsatisfactory. This study was designed to evaluate the safety and efficacy of human leukocyte antigen (HLA)-mismatched hematopoietic stem cell micro-transplantation (MST) in patients with MDS. A total of 22 patients with MDS, ranging between the ages of 39 and 74, were enrolled in this study. Eleven patients were given decitabine (DAC), a DNA methyltransferase inhibitor, combined with HLA-mismatched MST (MST-DAC group), and the remaining patients were given decitabine only (DAC group). The median overall survival (OS) of the MST-DAC group was higher than that of the DAC group (24 vs. 14.3 months; HR 0.32; 95% CI: 0.11-0.96; p = 0.04), although it is a study with small samples. The overall response rate (ORR), marrow complete remission (mCR), plus hematological improvement (HI) rates of the MST-DAC group were higher than that of the DAC group (81.8 vs. 54.5%, p = 0.36; 63.6 vs. 27.3%, p = 0.09, respectively); however, there were no statistical differences between the two groups, which may be attributed to the limited number of cases evaluated in this study. No graft-vs.-host disease was observed in the MST-DAC group. Patients in the MST-DAC group demonstrated a slightly lower incidence of hematological and non-hematological adverse events (AEs). DAC combined with HLA-mismatched MST may provide a novel, effective, and safe treatment for use in intermediate or high-risk MDS pathologies.

HLA-mismatched GPBSC infusion therapy in refractory Epstein-Barr virus-associated hemophagocytic lymphohistiocytosis: an observational study from a single center

Background

Hemophagocytic lymphohistiocytosis (HLH) is a severe or even fatal inflammatory state. Epstein–Barr virus (EBV) infection-associated HLH (EBV-HLH) is one of the most common secondary HLH and suffers a very poor prognosis. Allo-HSCT is often required for refractory EBV-HLH, but some patients still cannot proceed to the next allo-HSCT due to various factors. This study aimed to observe the efficacy of HLA-mismatched granulocyte colony-stimulating factor (G-CSF)-mobilized peripheral blood stem cells (GPBSCs) infusion for refractory EBV-HLH.

Methods

A retrospective case-control study of refractory EBV-HLH patients with GPBSC infusion from HLA-mismatched donors after chemotherapy (as GPBSC group) and sole chemotherapy (as control group) was performed. Efficacy was evaluated 2 and 4 weeks and all patients were followed-up until March 1, 2018.

Results

There were 18 cases who accepted infusion between March 2016 and Sep 2017 and 19 were randomly selected from refractory EBV-HLH patients who underwent salvage therapy during the same period for the control group. In GPBSC group, WBC (p = 0.017), Fbg (p = 0.040), and ferritin (p = 0.039) improved significantly after treatment. The overall response rate was 66.7% (CR 22.2%, PR 44.4%). However, there are no significant differences in changes of WBC, HGB, PLT, TG, Fbg, Ferritin, AST, ALT, and T-bil between two groups. Only the Fbg level was recovered better in the GPBSC infusion group (p = 0.003). In the GPBSC group, EBV-DNA decreased significantly after 2 weeks (p = 0.001) and 4 weeks (p = 0.012) after treatment, and the effect of the decrease was significantly better than that of the chemotherapy alone group in 2 weeks but not 4 weeks (p2w = 0.011, p4w = 0.145). The median survival time in the infusion group was 20.4 weeks [95% CI 10.9, 29.9], and the median survival time in the control group was 10.8 weeks [95% CI 0–24.34]. In the short-term, the infusion group’s survival rate was better (2-month 88.89% vs. 52.63%, p = 0.008; 3-month 83.33% vs. 47.09%, p = 0.012), but there was no difference in OS (p = 0.287).

Conclusions

Infusing GPBSCs combined with chemotherapy is effective, especially in decreasing EBV-DNA, performs better than chemotherapy alone, and improves short-term survival rate. GPBSC infusion is suggested as a bridging treatment method to allo-HSCT.

[Indications and management of hematologic microtransplantation: Recommendations of the French Society of Bone Marrow transplantation and cellular Therapy (SFGM-TC)]

Microtransplantation (MT) is based on injection of HLA-mismatched G-CSF mobilized hematopoietic stem cells, in combination with chemotherapy but without use of conditioning regimen nor immunosuppressive drugs. As a result, a transient microchimerism is induced without engraftment. Its efficacy relies both on host immune system stimulation (recipient versus tumor) and on a graft versus tumor effect. Data are scarce and concern mostly Asian patients with acute myeloid leukemia (AML) and high risk myelodysplastic syndrome (HR-MDS). In comparison to conventional treatment without MT, higher complete remission rates and longer disease free survival and overall survival have been reported. Safety seems acceptable. The most frequent adverse event is non-severe cytokine release syndrome. Risk of GVHD remains very low. Here, we summarize the published data and detail the practical aspects of the procedure. Current data are not strong enough to provide recommendations on indications. Nevertheless, it seems reasonable to propose MT to patients with AML or HR-MDS, regardless of age, presenting an indication for allogeneic stem cell transplantation but ineligible for it. MT is still under investigation and rather be proposed within clinical trials.

Comparative study of micro-transplantation from HLA fully mismatched unrelated and partly matched related donors in acute myeloid leukemia

Micro-transplantation (MST) by chemotherapy, combined with granulocyte colony-stimulating factor-mobilized peripheral blood stem cell (GPBSC) infusion, from an HLA partial matched related donor has shown some encouraging effective therapy for acute myeloid leukemia (AML). However, the outcome of human leukocyte antigen (HLA) fully mismatched unrelated donor-derived MST in such patients is still unknown. In the present study, we compared the efficacy of HLA fully mismatched unrelated donor-derived MST, and partly matched related donor-derived MST, in AML of 126 patients from two centers in China, These patients, aged 16 to 65 years, were given three or four courses of MST, which consisted of a high dosage cytarabine followed by GPBSC from unrelated donor or related donor. There was a statistically significant difference in 3-year leukemia-free survival (LFS) and 3-year overall survival (OS) between the unrelated and the related group. The non-treatment-related mortality (NRM) rates of patients, and other adverse complications, were no different in the two groups. In conclusion, unrelated donor-derived MST is believed to be a safe treatment, with efficacy similar to or higher than related donor-derived MST. This result provides support for the potential of MST for expanding the donor selection. However, the specific mechanism of action needs further study.

Microtransplantation in older patients with AML: A pilot study of safety, efficacy and immunologic effects

Older AML patients have low remission rates and poor survival outcomes with standard chemotherapy. Microtransplantation (MST) refers to infusion of allogeneic hematopoietic stem cells without substantial engraftment. MST has been shown to improve clinical outcomes compared with chemotherapy alone. This is the first trial reporting on broad correlative studies to define immunologic mechanisms of action of MST in older AML patients. Older patients with newly diagnosed AML were eligible for enrollment, receiving induction chemotherapy with cytarabine (100 mg/m2) on days 1-7 and idarubicin (12 mg/m2) on days 1-3 (7 + 3). MST was administered 24 hours later. Patients with complete response (CR) were eligible for consolidation with high dose cytarabine (HiDAC) and a second cycle of MST. Responses were evaluated according to standard criteria per NCCN. Immune correlative studies were performed. Sixteen patients were enrolled and received 7 + 3 and MST (median age 73 years). Nine (56%) had high-risk and seven (44%) had standard-risk cytogenetics. Ten episodes of CRS were observed. No cases of GVHD or treatment-related mortality were reported. Event-free survival (EFS) was 50% at 6 months and 19% at 1 year. Overall survival (OS) was 63% at 6 months and 44% at 1 year. Donor microchimerism was not detected. Longitudinal changes were noted in NGS, TCR sequencing, and cytokine assays. Addition of MST to induction and consolidation chemotherapy was well tolerated in older AML patients. Inferior survival outcomes in our study may be attributed to a higher proportion of very elderly patients with high-risk features. Potential immunologic mechanisms of activity of MST include attenuation of inflammatory cytokines and emergence of tumor-specific T cell clones.

T-Cell Immunotherapies Targeting Histocompatibility and Tumor Antigens in Hematological Malignancies

Over the last decades, T-cell immunotherapy has revealed itself as a powerful, and often curative, strategy to treat blood cancers. In hematopoietic cell transplantation, most of the so-called graft-vs.-leukemia (GVL) effect hinges on the recognition of histocompatibility antigens that reflect immunologically relevant genetic variants between donors and recipients. Whether other variants acquired during the neoplastic transformation, or the aberrant expression of gene products can yield antigenic targets of similar relevance as the minor histocompatibility antigens is actively being pursued. Modern genomics and proteomics have enabled the high throughput identification of candidate antigens for immunotherapy in both autologous and allogeneic settings. As such, these major histocompatibility complex-associated tumor-specific (TSA) and tumor-associated antigens (TAA) can allow for the targeting of multiple blood neoplasms, which is a limitation for other immunotherapeutic approaches, such as chimeric antigen receptor (CAR)-modified T cells. We review the current strategies taken to translate these discoveries into T-cell therapies and propose how these could be introduced in clinical practice. Specifically, we discuss the criteria that are used to select the antigens with the greatest therapeutic value and we review the various T-cell manufacturing approaches in place to either expand antigen-specific T cells from the native repertoire or genetically engineer T cells with minor histocompatibility antigen or TSA/TAA-specific recombinant T-cell receptors. Finally, we elaborate on the current and future incorporation of these therapeutic T-cell products into the treatment of hematological malignancies.

Transplantation without pretransplant therapy: Is this a possibility? Insights into providing transplantation at diagnosis for patients with acute leukemia

Allogeneic hematopoietic stem cell transplantation (HSCT) has the potential for providing a cure for several hematologic malignancies. Although in most circumstances, allogeneic HSCT is preceded by disease-directed or cytoreductive therapy, it is unclear if these toxic conditioning regimens can be circumvented. This review summarizes evidence that will provide insights into factors that influence outcomes in allogeneic HSCT and whether this curative therapy could be used right at diagnosis.

Current state of nonengrafting donor leukocyte infusion (focus on microtransplantation for acute myeloid leukemia)

PURPOSE OF REVIEW

Microtransplantation (or micro-stem cell transplantation, MST) is one permutation of alloreactive immunotherapy increasingly studied in clinical trials. It is most commonly applied to patients with myeloid malignancies who are not suitable candidates for allogeneic hematopoietic cell transplantation. This review highlights the past 2 years of work on stem/progenitor cell products in the field of nonengrafting donor leukocyte infusion (NE-DLI), with a focus on applications of MST in acute myeloid leukemia (AML).

RECENT FINDINGS

Assessing the utility of MST is hampered by lack of randomized controlled trials and by variability in donor selection algorithms, treatment timing, and unknown factors. The inherent complexity of the bidirectional alloreactive reactions, implicating many cell types, makes it challenging to move beyond correlative, population-level biology toward mechanistic explanations for MST's actions in any given patient-donor pair. Yet there are indicators that by stimulating a recipient-vs.-tumor effect, MST might substantially improve complete remission rates in AML and that it might find a role in postremission therapy.

SUMMARY

The mechanistic underpinnings of MST are gradually being disentangled and its clinical development remains in early stages.

HLA-Mismatched Microtransplant in Older Patients Newly Diagnosed With Acute Myeloid Leukemia: Results From the Microtransplantation Interest Group

Importance

The outcome of older patients with acute myeloid leukemia (AML) remains unsatisfactory. Recent studies have shown that HLA-mismatched microtransplant could improve outcomes in such patients.

Objective

To evaluate outcomes in different age groups among older patients with newly diagnosed AML who receive HLA-mismatched microtransplant.

Design, Setting, and Participants

This multicenter clinical study included 185 patients with de novo AML at 12 centers in China, the United States, and Spain in the Microtransplantation Interest Group. Patients were divided into the following 4 age groups: 60 to 64 years, 65 to 69 years, 70 to 74 years, and 75 to 85 years. The study period was May 1, 2006, to July 31, 2015.

Exposures

Induction chemotherapy and postremission therapy with cytarabine hydrochloride with or without anthracycline, followed by highly HLA-mismatched related or fully mismatched unrelated donor cell infusion. No graft-vs-host disease prophylaxis was used.

Main Outcomes and Measures

The primary end point of the study was to evaluate the complete remission rates, leukemia-free survival, and overall survival in different age groups. Additional end points of the study included hematopoietic recovery, graft-vs-host disease, relapse rate, nonrelapse mortality, and other treatment-related toxicities.

Results

Among 185 patients, the median age was 67 years (range, 60-85 years), and 75 (40.5%) were female. The denominators in adjusted percentages in overall survival, leukemia-free survival, relapse, and nonrelapse mortality are not the sample proportions of observations. The overall complete remission rate was not significantly different among the 4 age groups (75.4% [52 of 69], 70.2% [33 of 47], 79.1% [34 of 43], and 73.1% [19 of 26). The 1-year overall survival rates were 87.7%, 85.8%, and 77.8% in the first 3 age groups, which were much higher than the rate in the fourth age group (51.7%) (P = .004, P = .008, and P = .04, respectively). The 2-year overall survival rates were 63.7% and 66.8% in the first 2 age groups, which were higher than the rates in the last 2 age groups (34.2% and 14.8%) (P = .02, P = .03, P < .001, and P < .001, respectively). The 1-year cumulative incidences of nonrelapse mortality were 10.2%, 0%, 3.4%, and 26.0% in the 4 age groups and 8.1% in all patients. The median times to neutrophil and platelet recovery were 12 days and 14 days after induction chemotherapy, respectively. Five patients had full or mixed donor engraftment, and 30.8% (8 of 26) of patients demonstrated donor microchimerism. Two patients (1.1%) developed severe acute graft-vs-host disease.

Conclusions and Relevance

Microtransplant achieved a high complete remission rate in AML patients aged 60 to 85 years and higher 1-year overall survival in those aged 60 to 74 years.

Impact of T Cell Dose on Outcome of T Cell-Replete HLA-Matched Allogeneic Peripheral Blood Stem Cell Transplantation

Data on whether the T cell dose of allogeneic peripheral blood stem cell (PBSC) products influences transplantation outcomes are conflicting. Using the Center for International Blood and Marrow Transplant Research database, we identified 2736 adult patients who underwent first allogeneic PBSC transplantation for acute leukemia or myelodysplastic syndrome between 2008 and 2014 using an HLA-matched sibling donor (MSD) or an 8/8-matched unrelated donor (MUD). We excluded ex vivo and in vivo T cell-depleted transplantations. Correlative analysis was performed between CD3+ T cell dose and the risk of graft-versus-host-disease (GVHD), relapse, nonrelapse mortality (NRM), disease-free survival (DFS), and overall survival (OS). Using maximum likelihood estimation, we identified CD3+ T cell dose cutoff that separated the risk of acute GVHD (aGVHD) grade II-IV in both the MSD and MUD groups. A CD3+ T cell dose cutoff of 14 × 107 cells/kg identified MSD/low CD3+ (n = 223) and MSD/high CD3+ (n = 1214), and a dose of 15 × 107 cells/kg identified MUD/low CD3+ (n = 197) and MUD/high CD3+ (n = 1102). On univariate analysis, the MSD/high CD3+ group had a higher cumulative incidence of day +100 aGVHD grade II-IV compared with the MSD/low CD3+ group (33% versus 25%; P = .009). There were no differences between the 2 groups in engraftment rate, risk of aGVHD grade III-IV or chronic GVHD (cGVHD), NRM, relapse, DFS, or OS. The MUD/high CD3+ group had a higher cumulative incidence of day +100 aGVHD grade II-IV compared with the MUD/low CD3+ group (49% versus 41%; P = .04). There were no differences between the 2 groups in engraftment rate, risk of severe aGVHD or cGVHD, NRM, relapse, DFS, or OS. Multivariate analysis of the MSD and MUD groups failed to show an association between CD3+ T cell dose and the risk of either aGVHD grade II-IV (P = .10 and .07, respectively) or cGVHD (P = .80 and .30, respectively). Subanalysis of CD4+ T cells, CD8+ T cells, and CD4+/CD8+ ratio failed to identify cutoff values predictive of transplantation outcomes; however, using the log-rank test, the sample size was suboptimal for identifying a difference at this cutoff cell dose. In this registry study, the CD3+ T cell dose of PBSC products did not influence the risk of aGVHD or cGVHD or other transplantation outcomes when using an MSD or an 8/8-matched MUD. Subset analyses of CD4+ and CD8+ T cell doses were not possible given our small sample size.

Quantitative characterization of T-cell repertoire alteration in Chinese patients with B-cell acute lymphocyte leukemia after CAR-T therapy

Chimeric antigen receptor (CAR) T-cell therapy has displayed potent anti-leukemia activity in acute lymphocytic leukemia (ALL), acting as a new ray of hope to refractory/relapsed patients. However, the influence of CAR-T therapy on host immune system has not been well elucidated. Thus, We applied high-throughput T cell receptor β chain sequencing to track the dynamic change of T-cell repertoire induced by CAR-T therapy in B-cell ALL patients. Six Chinese patients achieving complete remission were under observation, whose blood samples, bone marrow samples and infused CAR-T samples were collected at serial time points before and after CAR-T therapy. We observed decreased TCR diversity and increased clonality of T-cell repertoire in both peripheral blood and bone marrow after CAR-T administration. The persistent T cell clones in blood and bone marrow expanded following leukemic cell destruction and were barely detected in CAR T-cell pool. For the first time, our results demonstrated CAR-T therapy could stimulate the clonal proliferation of CAR-negative T cells in patients. Considering other groups' animal results indicating that CAR-T therapy could facilitate the proliferation of tumor antigen-specific T cells and that the emergence of these T cell clones followed the destruction of leukemic cells, they are most likely tumor antigen-specific.

Induction of anti-leukemic responses by stimulation of leukemic CD3+ cells with allogeneic stimulator cells

Background

Immunotherapeutic protocols have focused on identification of stimuli that induce effective anti-leukemic immune responses. One potent immune stimulus is the encounter with allogeneic cells. Our group previously showed that the infusion of haploidentical donor white blood cells (1-2 × 10⁸ CD3+ cells/kg) into patients with refractory hematological malignancies induced responses of varying magnitude in over half of the patients. Because donor cells were eliminated within 2 weeks in these patients, it is presumed that the responses of recipient lymphocytes were critically important in achieving prolonged anti-leukemic responses.

Methods

The role of patient CD3+ cells in anti-leukemic responses was examined by isolating peripheral blood mononuclear cells from newly diagnosed leukemic patients. Immunophenotyping was performed on these peripheral blood mononuclear cells. CD3+ cells were isolated from the peripheral blood mononuclear cells and tested for their ability to proliferate and lyse autologous leukemic cells when stimulated with unrelated allogeneic cells.

Results

Allostimulated CD3+ cells effectively generated cytolytic responses to autologous CD3-cells in 11/21 patients. Increased numbers of CD4+ cells expressing high levels of granzyme A, B and perforin and CD8+CD39+ cells were found in nonresponsive CD3+ cells.

Conclusions

These results indicate that CD3+ cells from leukemic patients are capable of generating anti-leukemic responses when stimulated with unrelated allogeneic cells. This model can be used to identify approaches using alloreactive responses by patient lymphocytes to enhance in vivo anti-leukemic responses.

Recipient and donor cells in the graft-versus-solid tumor effect: It takes two to tango

Allogeneic hematopoietic stem cell transplantation (alloHSCT) produces -similar to the long-established graft-versus-leukemia effect- graft-versus-solid-tumor effects. Clinical trials reported response rates of up to 53%, occurring mostly but not invariably in association with full donor chimerism and/or graft-versus-host disease. Although donor-derived T cells are considered the principal effectors of anti-tumor immunity after alloHSCT or donor leukocyte infusion (DLI), growing evidence indicate that recipient-derived immune cells may also contribute. Whereas the role of recipient-derived antigen-presenting cells in eliciting graft-versus-host reactions and priming donor T cells following DLI is well known, resulting inflammatory responses may also break tolerance of recipient effector cells towards the tumor. Additionally, mouse studies indicated that post-transplant recipient leukocyte infusion produces anti-leukemia and anti-solid-tumor effects that were exclusively mediated by recipient-type effector cells, without graft-versus-host disease. Here, we review current preclinical and clinical evidence on graft-versus-solid-tumor effects and growing evidence on the effector role of recipient-derived immune cells in the anti-tumor effect of alloHSCT.

Intrathecal Infusion of Haploidentical Nondonor Lymphocytes for Central Nervous System Leukemic Relapse After Haploidentical Hematopoietic Stem Cell Transplantation

Leukemic relapse in the central nervous system (CNS) after conventional treatment is associated with a poor prognosis. The effectiveness and safety of IV infusion of human leukocyte antigen (HLA)-mismatched lymphocytes for leukemia, and intrathecal (IT) infusion of HLA-mismatched lymphocytes for cerebrospinal fluid (CSF) dissemination of medulloblastoma have been reported. A 13-year-old girl (HLA-A31) was diagnosed as relapsing from Philadelphia chromosome-positive acute leukemia in the CNS after receiving chemotherapy, tyrosine kinase inhibitors, haploidentical hematopoietic stem cell transplantation (HSCT) from her father (HLA-A31), and craniospinal irradiation. We performed an IT infusion of haploidentical lymphocytes from her mother. Peripheral blood mononuclear cells obtained from her mother (HLA-A31) were administered by IT infusion weekly. Examination of CSF 1 week after first IT showed that lymphocyte counts had increased markedly and the breakpoint cluster region/abelson-bearing cells had disappeared. Furthermore, CD3 T cells in the CSF were negative for HLA-A31, and expressed high HLA-DR. These results indicate the infused non-HSCT-donor lymphocytes did not survive, and that the HSCT donor(father)-derived lymphocytes migrated to the CSF and were activated. The patient showed partial remission for 2 months following this therapy. Serious adverse reactions and graft versus host disease were not observed. To control leukemic CNS dissemination, haploidentical nondonor lymphocytes might contribute to a graft versus leukemia effect.

Unrelated HLA mismatched microtransplantation in a patient with refractory secondary acute myeloid leukemia

Microtransplantation (MST), a type of HLA-mismatched allogeneic cellular therapy, is a promising, cellular therapy for acute myeloid leukemia (AML). MST transfuses granulocyte colony-stimulating factor (G-CSF)-mobilized, HLA-mismatched donor peripheral blood stem cells into patients undergoing conventional chemotherapy. MST, using haploidentical donors, has been shown to yield clinical benefit without any permanent marrow engraftment in AML. Consequently, graft-versus-host disease concerns are rendered irrelevant with no need for immunosuppression. We describe the first reported patient with refractory AML who underwent salvage MST from an unrelated, complete HLA-mismatched donor. The patient achieved remission without complication, warranting further study of unrelated HLA-mismatched donor MST in AML.

Cooperation of CD4+ T cells and CD8+ T cells and release of IFN-γ are critical for antileukemia responses of recipient mice treated by microtransplantation

Previous studies have demonstrated that infusion of allogeneic matched and haploidentical peripheral blood stem cells with minimal conditioning (microtransplantation) achieved durable responses in patients with refractory leukemia/lymphoma in the absence of engraftment. The mechanisms underlying this response have not been thoroughly elucidated, while host-versus-graft reactions are likely to have an important role. The present study established a mismatched microtransplantation mouse model of leukemia to study the roles of CD4⁺ T cells and CD8⁺ T cells in changes of interferon (IFN)-γ and interleukin (IL)-4 release to explore the mechanisms of the effects of microtransplantation. It was demonstrated that IFN-γ is critical to the antileukemia response in a mouse model of microtransplantation. The therapeutic efficacy was associated with the number of CD4⁺ T cells (Pearson's r=0.722). In addition, CD8⁺ T cells increased the release of IFN-γ with assistance from CD4⁺ T cells. IL-2 augmented IFN-γ release, partly by increasing CD4⁺ T cells (42.8 vs. 35.6%; P<0.05). The present study suggested that the release of IFN-γ via cooperation of CD4⁺ T cells and CD8⁺ T cells represents a crucial mechanism in the antileukemia responses of recipient leukemic mice treated by microtransplantation. During this process, the cooperation of CD4⁺ T cells and CD8⁺ T cells was demonstrated to have a major role in the antileukemia effect. IL-2 may be developed into an agent used for improving the efficacy of microtransplantation by increasing CD4⁺ T cells.

Young donor white blood cell immunotherapy induces extensive tumor necrosis in advanced-stage solid tumors

Background

In the past decade, a variety of immunotherapy approaches focused predominantly on the adaptive immune system have shown unprecedented responses in patients with advanced-stage malignancies. However, studies in spontaneous regression/complete resistance (SR/CR) mice and humans have shown a novel innate cancer-killing activity mediated by granulocytes, which is completely transferable for prevention or therapy against established malignancies.

Methods

Three patients with advanced, relapsed or refractory solid tumors for which no standard therapy was available or was refused were enrolled into this ongoing combined phase I/II open label clinical trial testing the safety, dose tolerance, and possible antineoplastic efficacy of sequential infusions of HLA-mismatched non-irradiated allogeneic white cells (68–91% granulocytes) collected by leukapheresis from young, healthy donors (age 18–35) following mobilization with granulocyte colony stimulating factor (G-CSF) and dexamethasone.

Results

Besides fevers and flushing, no infusional toxicities were observed. All patients remained clinically stable following infusions with mild cytokine release syndrome and no evidence of transfusion-associated graft-versus-host disease, acute tumor lysis syndrome,or transfusion-associated acute lung injury. Pathological examination of all cases post-mortem revealed extensive tumor necrosis up to 80% in patients 1–2, 40–50% in patient 3, and leukocyte infiltration in all cases, which could not be attributed to disease progression.

Conclusions

Allogeneic white cell immunotherapy (AWIT) from young, healthy donors is well tolerated with minimal side effects and shows antitumor activity against advanced-stage solid tumors. AWIT represents a novel, safe, and cost-effective immunotherapy that can be administered in an outpatient cancer clinic.

Clinical Studies in Hematologic Microtransplantation

The anti-tumor effects of allogeneic hematopoietic stem cell transplantation depend upon engraftment of donor cells followed by a graft-versus-tumor (GVT) effect. However, pre-clinical and clinical studies have established that under certain circumstances, anti-tumor responses can occur despite the absence of high levels of durable donor cell engraftment. Tumor response with little or no donor engraftment has been termed "microtransplantation." It has been hard to define conditions leading to tumor responses without donor cell persistence in humans because the degree of engraftment depends very heavily upon many patient-specific factors, including immune status and degree of prior therapy. Likewise, it is unknown to what degree donor chimerism in the blood or tissue is required for an anti-tumor effect under conditions of microtransplantation. In this review, we summarize some key studies supporting the concept of microtransplantation and emphasize the importance of recent large studies of microtransplantation in patients with acute myelogenous leukemia (AML). These AML studies provide the first evidence of the efficacy of microtransplantation as a therapeutic strategy and lay the foundation for additional pre-clinical studies and clinical trials that will refine the understanding of the mechanisms involved and guide its further development as a treatment modality.

Hitting the Holy Grail of Hematopoietic Cell Transplantation with Naive T-Cell Depleted Allografts-Graft Engineered Hematopoietic Stem Cell Transplant

Hematopoietic cell transplant is a potentially curative procedure for many benign and malignant conditions. The efficacy of allogeneic transplant relies in part on the cytotoxicity of the conditioning regimen and the graft versus tumor effect mediated by alloreactive donor T cells; the same cells are also implicated in the development of graft versus host disease (GVHD). Selective identification and depletion of the T cells implicated in GVHD, while preserving the T cells responsible for graft versus tumor effect has been the focus of many research groups in the recent years. Here we briefly review the physiology of T cells in transplantation, and comment on a recent clinical trial published by Bleakly et al. using a novel way of graft engineered allograft via naïve T cell depletion.

[A retrospective analysis of prognosis in favorable-risk acute myeloid leukemia patients with different consolidation regimens]

Objective: To explore the impact on prognosis in favorable-risk acute myeloid leukemia (AML) patients with different consolidation regimens after first complete remission (CR(1)). Methods: A total of 107 cases of non-refractory adult AML from January 2010 to June 2015 in single center were enrolled in the study. HD-Ara-C group (38 cases) as the control group, we explore the prognosis in three consolidation regimens, including micro-transplantation (16 cases) , autologous transplantation (auto-PBSCT, 14 cases) , allogeneic transplantation (allo-HSCT, 39 cases). Results: Of 107 patients (59 males and 48 females) , with a median age of 33 (16-59) years old and a median follow-up of 36.5 (5.3-79.1) months, the overall relapse rate was 20.6% (22/107) , and overall mortality rate was 18.7% (20/107). The 5 years cumulative relapse rate (CIR) of HD-Ara-C, micro-transplantation, auto-PBSCT and allo-HSCT group were 39.7%, 6.2%, 14.3% and 5.6%, respectively (P<0.001). The CIR of the observed group was lower than the HD-Ara-C group. The 5 years progression-free survival (PFS) rate of HD-Ara-C, micro-transplantation, auto-PBSCT and allo-HSCT group were 44.7%, 93.8%, 85.7% and 78.1%, respectively (P=0.011). The PFS of observed groups were similar, but superior to that in HD-Ara-C group. The 5-year overall survival (OS) in four groups was 54.9%, 100%, 92.9% and 77.4%, respectively (P>0.05). Multiple factors analysis showed that compared to HD-Ara-C regimen, allo-HSCT could improve PFS (HR=0.376, P=0.031) , but not OS (P>0.05) ; micro-transplantation and auto-PBSCT could not improve the PFS or OS (P>0.05). Conclusion: As compared with HD-Ara-C regimen, allo-HSCT could obviously decrease CIR, improve PFS, but treatment-related mortality is high. These results show that auto-PBSCT and micro-transplantation have similar outcomes, compared to HD-Ara-C regimen, so both can be used as a option of consolidation treatment for favorable-risk AML.

Tumors arise from the excessive repair of damaged stem cells

Although many hypotheses for tumorigenesis have been proposed, none can explain the occurrence and development of tumors comprehensively until now. We put forward a new hypothesis: tumors arise from the excessive repair of damaged stem cells. There are stem cells in all tissues and organs, and the stem cells have perfect damage repair mechanisms, including damage repair systems and repair-inhibiting systems. Tumors arise from the excessive repair of damaged stem cells, i.e., carcinogens induce stem cell damage, leading to overexpression of damage repair systems, and simultaneous inactivation of repair-inhibiting systems through genetic or non-genetic mechanisms, finally forming tumors. The outcome (forming clinically significant tumors or death) and development (tumor recurrence, metastasis or spontaneous healing) of the tumor cells depends on whether the injury and the excessive repair persists, whether immune surveillance function is normal and the tumor microenvironment is appropriate. This hypothesis not only addresses the issues of where tumor cells arise from, how tumors form and where they go, but also provides a reasonable explanation for many unresolved issues in tumor occurrence, development, metastasis or healing. In addition, this hypothesis could guide the early diagnosis, reasonable treatment and effective prevention of tumors.

Co-infusion of haplo-identical CD19-chimeric antigen receptor T cells and stem cells achieved full donor engraftment in refractory acute lymphoblastic leukemia

BACKGROUND

Elderly patients with relapsed and refractory acute lymphoblastic leukemia (ALL) have poor prognosis. Autologous CD19 chimeric antigen receptor-modified T (CAR-T) cells have potentials to cure patients with B cell ALL; however, safety and efficacy of allogeneic CD19 CAR-T cells are still undetermined.

CASE PRESENTATION

We treated a 71-year-old female with relapsed and refractory ALL who received co-infusion of haplo-identical donor-derived CD19-directed CAR-T cells and mobilized peripheral blood stem cells (PBSC) following induction chemotherapy. Undetectable minimal residual disease by flow cytometry was achieved, and full donor cell engraftment was established. The transient release of cytokines and mild fever were detected. Significantly elevated serum lactate dehydrogenase, alanine transaminase, bilirubin and glutamic-oxalacetic transaminase were observed from days 14 to 18, all of which were reversible after immunosuppressive therapy.

CONCLUSIONS

Our preliminary results suggest that co-infusion of haplo-identical donor-derived CAR-T cells and mobilized PBSCs may induce full donor engraftment in relapsed and refractory ALL including elderly patients, but complications related to donor cell infusions should still be cautioned.

TRIAL REGISTRATION

Allogeneic CART-19 for Elderly Relapsed/Refractory CD19+ ALL. NCT02799550.

Proceedings from the Second Haploidentical Stem Cell Transplantation Symposium-Haplo2014, San Francisco, California, December 4, 2014

Significant progress has been made over the past decade in haploidentical transplantation, with the development of novel methods to control intense alloreactive reactions generated in the major HLA-mismatched setting. Application of post-transplantation cyclophosphamide has gained worldwide acceptance as an effective and low-cost way to perform this type of transplantation, with outcomes now similar to those from HLA-matched unrelated donors. These advances have resulted in improved treatment-related mortality, whereas disease relapse has emerged as the most common cause of treatment failure. In addition, improvements in immunologic reconstitution after transplantation are much needed, not only in haploidentical transplantation but in all forms of stem cell transplantation. This symposium has focused on some of the most promising methods to control alloreactivity in this form of transplantation and application of cellular therapy to prevent disease relapse after transplantation, as well as understanding immunologic reconstitution and foreseeable approaches to improve immune recovery after transplantation.

A Study of Human Leukocyte Antigen Mismatched Cellular Therapy (Stem Cell Microtransplantation) in High-Risk Myelodysplastic Syndrome or Transformed Acute Myelogenous Leukemia

The treatment outcomes of myelodysplastic syndrome (MDS) and transformed acute myelogenous leukemia (tAML) remain very unsatisfactory. We designed a combination of human leukocyte antigen (HLA)-mismatched hematopoietic stem cell microtransplantation (MST) with chemotherapy for patients with MDS and tAML and evaluated its effects and toxicity. Patients were between 13 and 79 years old. Patients with MDS (n=21) were given HLA-mismatched MST combined with decitabine and cytarabine; patients with tAML (n=22) were given HLA-mismatched MST combined with decitabine and cytarabine, and also mitoxantrone. Patients in complete remission (CR) also received MST plus decitabine and medium-dose cytarabine chemotherapy without graft-versus-host disease (GVHD) prophylaxis. The overall response rate of the patients with MDS was significantly higher than that of those with tAML (81% vs. 50%; p=.03). The CR rates were 52.4% and 36.4% in the two groups, respectively. There was no difference in the cytogenetic CR rate between the MDS and tAML groups (85.7% vs. 70%, respectively; p=.7). The 24-month overall survival of the patients with MDS was significantly higher than that of the patients with tAML (84.7% and 34.1%, respectively; p=.003). The median recovery times of neutrophils and platelets were, respectively, 14 and 17 days in the patients with MDS, and 16 and 19 days in those with tAML. The treatment-related mortality rates were 4.8% and 18.2%, respectively, in the MDS and tAML groups (p=.34). No GVHD was observed in any patient. Microtransplantation combined with decitabine and chemotherapy may provide a novel, effective, and safe treatment for high-risk MDS and tAML.

SIGNIFICANCE

Microtransplantation (MST) refers to regular chemotherapy combined with granulocyte colony-stimulating factor-mobilized peripheral blood stem cell infusion of human leukocyte antigen-mismatched donor cells without using immunosuppressive agents. It aims to support hematopoietic recovery and perform graft-versus-leukemia (GVL) effects but differs from traditional allogeneic stem cell transplantation because the rate of donor cell chimerism is low and there is and no graft-versus-host disease (GVHD) risk. Thus, a trial was designed to evaluate the safety and efficacy of MST in patients with myelodysplastic syndrome and those with transformed acute myelogenous leukemia. Higher complete remission and cytogenetic complete response rates were observed, and the treatment improved disease progress-free survival, sped hematopoietic recovery, and avoided GVHD.

A Two-Step Haploidentical Versus a Two-Step Matched Related Allogeneic Myeloablative Peripheral Blood Stem Cell Transplantation

Haploidentical stem cell transplantation (SCT) offers a transplantation option to patients who lack an HLA-matched donor. We developed a 2-step approach to myeloablative allogeneic hematopoietic stem cell transplantation for patients with haploidentical or matched related (MR) donors. In this approach, the lymphoid and myeloid portions of the graft are administered in 2 separate steps to allow fixed T cell dosing. Cyclophosphamide is used for T cell tolerization. Given a uniform conditioning regimen, graft T cell dose, and graft-versus-host disease (GVHD) prophylaxis strategy, we compared immune reconstitution and clinical outcomes in patients undergoing 2-step haploidentical versus 2-step MR SCT. We retrospectively compared data on patients undergoing a 2-step haploidentical (n = 50) or MR (n = 27) peripheral blood SCT for high-risk hematological malignancies and aplastic anemia. Both groups received myeloablative total body irradiation conditioning. Immune reconstitution data included flow cytometric assessment of T cell subsets at day 28 and 90 after SCT. Both groups showed comparable early immune recovery in all assessed T cell subsets except for the median CD3/CD8 cell count, which was higher in the MR group at day 28 compared with that in the haploidentical group. The 3-year probability of overall survival was 70% in the haploidentical group and 71% in the MR group (P = .81), while the 3-year progression-free survival was 68% in the haploidentical group and 70% in the MR group (P = .97). The 3-year cumulative incidence of nonrelapse mortality was 10% in the haploidentical group and 4% in the MR group (P = .34). The 3-year cumulative incidence of relapse was 21% in the haploidentical group and 27% in the MR group (P = .93). The 100-day cumulative incidence of overall grades II to IV acute GVHD was higher in the haploidentical group compared with that in the MR group (40% versus 8%, P < .001), whereas the grades III and IV acute GVHD was not statistically different between both groups (haploidentical, 6%; MR, 4%; P = .49). The cumulative incidence of cytomegalovirus reactivation was also higher in the haploidentical group compared to the MR group (haploidentical, 68%; MR, 19%; P < .001). There were no deaths from GVHD in either group. Using an identical conditioning regimen, graft T cell dose, and GVHD prophylaxis strategy, comparable early immune recovery and clinical outcomes were observed in the 2-step haploidentical and MR SCT recipients.

Effect of the microtransplantation of allogeneic hematopoietic stem cells as maintenance therapy for elderly patients with acute leukemia

The incidence of acute myeloid leukemia (AML) increases with age. Elderly patients with AML are less tolerant to high-intensity consolidation therapy than younger patients, with significantly worse prognoses. Induction and consolidation therapy combined with allogeneic hematopoietic stem cell microtransplantation may improve the prognosis of elderly patients with AML. The present study reports the effect of maintenance therapy with low-dose chemotherapy treatment combined with microtransplantation in elderly patients with AML following consolidation. Between January 2011 and April 2014, three elderly patients (>55 years old), including one 58-year-old patient with acute mixed lineage leukemia (AMLL) and two patients with AML aged 59 years and 62 years, underwent microtransplantation maintenance therapy. Following a complete response to induction chemotherapy and consolidation chemotherapy with two to four cycles of medium dose Ara-c (auto transplantation was performed in the patient with AMLL), maintenance therapy was performed using low-dose Ara-c combined with human leukocyte antigen haploidentical allogeneic hematopoietic stem cell microtransplantation, which was repeated every 3 to 6 months. The patients were followed up for 27, 20 and 16 months, respectively, and all three patients achieved disease-free survival. The bone marrow Wilms' tumor suppression gene (WT1) level of the case with AMLL was dynamically monitored. The results showed that the WT1 level was abnormally high prior to microtransplantation and gradually declined to normal levels subsequent to the process. None of the patients suffered from graft versus host disease during the microtransplantation process. In conclusion, microtransplantation maintenance therapy following consolidation therapy is feasible in elderly patients with AML, and is expected to be able to further remove residual lesions and improve treatment efficacy. A large-scale clinical trial is required to confirm the effect of maintenance therapy in elderly patients with AML.