TCR αβ+/CD19+ cell depletion in haploidentical hematopoietic allogeneic stem cell transplantation: a review of current data

Phase I study of zoledronic acid combined with escalated doses of interleukine-2 for early in vivo generation of Vγ9Vδ2 T-cells after haploidentical stem cell transplant with posttransplant cyclophosphamide

The presence of donor Vγ9Vδ2 T-cells after haploidentical hematopoietic stem cell transplant (h-HSCT) has been associated with improved disease-free survival. These cells kill tumor cells in a non-MHC restricted manner, do not induce graft-versus-host disease (GVHD), and can be generated by stimulation with zoledronic acid (ZA) in combination with interleukin-2 (IL-2). This monocentric phase I, open-label, dose-escalating study (ClinicalTrials.gov: NCT03862833) aimed at evaluating the safety and possibility to generate Vγ9Vδ2 T-cells early after h-HSCT. It applied a standard 3 + 3 protocol to determine the maximum tolerated dose (MTD) of increasing low-doses of IL-2 (5 days [d] per week, 4 weeks) in combination with a single dose of ZA, starting both the first Monday after d + 15 posttransplant. Vγ9Vδ2 T-cell monitoring was performed by multiparameter flow cytometry on blood samples and compared with a control cohort of h-HSCT recipients. Twenty-six patients were included between April 2019 and September 2022, 16 of whom being ultimately treated and seven being controls who received h-HSCT only. At the three dose levels tested, 1, 0, and 1 dose-limiting toxicities were observed. MTD was not reached. A significantly higher number of Vγ9Vδ2 T-cells was observed during IL-2 treatment compared with controls. In conclusion, early in vivo generation of Vγ9Vδ2 T-cells is feasible after h-HSCT by using a combination of ZA and repeated IL-2 infusions. This study paves the way to a future phase 2 study, with the hope to document lesser posttransplant relapse with this particular adaptive immunotherapy.

Automatic generation of alloreactivity-reduced donor lymphocytes and hematopoietic stem cells from the same mobilized apheresis product

INTRODUCTION

In vitro or in vivo depletion of alloreactive T cells can facilitate haplo-identical hematopoietic stem cell transplantation (HSCT). Very satisfactory transplant outcomes were thus reported for TCRαβ/CD19-depleted hematopoietic stem/progenitor cell (HSPC) grafts. The current semi-automatic manufacturing process on the CliniMACS Plus, although robust, still requires a significant amount of manual labor to be completed. Towards advancing and further facilitating large scale cell processing, a new TCRαβ/CD19 depletion module combined with the previously described CD45RA depletion module (to serve as allo-reactivity attenuated donor lymphocyte infusion) was established on the CliniMACS Prodigy.

METHODS

We evaluated six apheresis products from G-CSF-mobilized volunteer donors which were split automatically by the Prodigy, one portion each depleted of CD45RA+ or of TCRαβ+ and CD19+ cells. We investigated critical quality attributes for both products. Products were assessed for recovery of HSPCs and mature subsets, as well as depletion efficiency of targeted cells using flow cytometry. Effects of apheresis and product age post 48 h storage at 2-6 °C as well as freeze-thawing on product viability and recovery of WBC and HPSCs were assessed by flow cytometry.

RESULTS

Ten sequential automatic processes were completed with minimal hands-on time beyond tubing set installation. Depletion efficiency of CD45RA+ resp. TCRαβ+ and CD19+ cells was equivalent to previous reports, achieving mean depletions of 4 log of targeted cells for both products. HSPC products retained TCRγδ+ and NK cells. 48 h storage of apheresis product was associated with the expected modest loss of HSPCs, but depletions remained efficient. Depleted products were stable until at least 72 h after apheresis with stem cell viabilities > 90%. Freeze-thawing resulted in loss of NK cells; post-thaw recovery of viable CD45+ and HSPCs was > 70% and in line with expectation.

CONCLUSION

The closed, GMP-compatible process generates two separate medicinal products from the same mobilized apheresis product. The CD45RA-depleted products contained functional memory T cells, whereas the TCRαβ/CD19-depleted products included HSPCs, TCRγδ+ and NK cells. Both products are predicted to be effectively depleted of GVH-reactivity while providing immunological surveillance, in support of haplo-identical HSCT.

Immunological recovery following HLA-matched CD3+ TCR αß+/CD19+ depleted hematopoietic stem cell transplantation in children

BACKGROUND

Allogeneic hematopoietic stem cell transplantation (HSCT) is a potentially curative option for children with both malignant and nonmalignant diseases. T-cell depletion techniques may result in reduced transplant-related mortality compared with unmanipulated grafts due to a lower incidence of GvHD.

METHODS

Immune recovery and outcome were analyzed in a cohort of 23 patients with malignant and nonmalignant diseases who received CD3+TCRαβ+ T- and B-cell-depleted allografts from matched donors after reduced-intensity or myeloablative conditioning. The median number of CD34+, CD3+TCRαβ+, and CD19+B-cells infused was 12.7 × 10⁶ /kg, 16.8 × 10³ /kg, and 96 × 10³ /kg bodyweight.

RESULTS

With a median follow-up of 36 (range 1-73) months, overall survival and disease-free survival at 3 years were 65.2% and 60.8%. Eight patients died, six due to the underlying disease and two of extended visceral cGvHD. Immune reconstitution, disease-free, and overall survivals were similar compared with a historical cohort of 23 patients transplanted with matched unmanipulated bone marrow. A significant lower rate of higher grade (III-IV) aGvHD was observed in the manipulated HSCT group (8.7% vs. 26%; p = 0.001), whereas the incidence of cGvHD was equal.

CONCLUSIONS

Our data suggest that this graft manipulation strategy could be a safe and effective alternative to conventional HSCT techniques in matched donors.

Allogeneic MHC-matched T-cell receptor α/β-depleted bone marrow transplants in SHIV-infected, ART-suppressed Mauritian cynomolgus macaques

Allogeneic hematopoietic stem cell transplants (allo-HSCTs) dramatically reduce HIV reservoirs in antiretroviral therapy (ART) suppressed individuals. However, the mechanism(s) responsible for these post-transplant viral reservoir declines are not fully understood. Therefore, we modeled allo-HSCT in ART-suppressed simian-human immunodeficiency virus (SHIV)-infected Mauritian cynomolgus macaques (MCMs) to illuminate factors contributing to transplant-induced viral reservoir decay. Thus, we infected four MCMs with CCR5-tropic SHIV162P3 and started them on ART 6-16 weeks post-infection (p.i.), maintaining continuous ART during myeloablative conditioning. To prevent graft-versus-host disease (GvHD), we transplanted allogeneic MHC-matched α/β T cell-depleted bone marrow cells and prophylactically treated the MCMs with cyclophosphamide and tacrolimus. The transplants produced ~ 85% whole blood donor chimerism without causing high-grade GvHD. Consequently, three MCMs had undetectable SHIV DNA in their blood post-transplant. However, SHIV-harboring cells persisted in various tissues, with detectable viral DNA in lymph nodes and tissues between 38 and 62 days post-transplant. Further, removing one MCM from ART at 63 days post-transplant resulted in SHIV rapidly rebounding within 7 days of treatment withdrawal. In conclusion, transplanting SHIV-infected MCMs with allogeneic MHC-matched α/β T cell-depleted bone marrow cells prevented high-grade GvHD and decreased SHIV-harboring cells in the blood post-transplant but did not eliminate viral reservoirs in tissues.

Updated Trends in Hematopoietic Cell Transplantation in the United States with an Additional Focus on Adolescent and Young Adult Transplantation Activity and Outcomes

Hematopoietic cell transplantation (HCT) has been successfully used to treat many malignant and nonmalignant conditions. As supportive care, donor selection, and treatment modalities evolve, documenting HCT trends and outcomes is critical. This report from the Center for International Blood and Marrow Transplant Research (CIBMTR) provides an update on current transplantation activity and survival rates in the United States. Additional data on the use and outcomes of HCT in the adolescent and young adult (AYA) population are included. AYA patients more frequently receive peripheral blood stem cell grafts than pediatric patients, which may reflect differences in practice in pediatric versus adult treatment centers. The proportions of donor types also differ those in adult and pediatric populations. Outcomes for patients in the AYA age range are similar to those of pediatric patients for acute myelogenous leukemia but worse for acute lymphoblastic leukemia. Outcomes for both leukemias are better in AYA patients compared with older adults. Comparing the time periods 2000 to 2009 and 2010 to 2019 revealed significant improvement in overall survival across the age spectrum, but the greatest improvement in the AYA age group.

Unresolved issues in allogeneic hematopoietic cell transplantation for non-malignant diseases

Allogeneic hematopoietic cell transplantation (HCT) can be curative for a variety of non-malignant diseases (NMDs) as well as hematological malignancies. However, there are several fundamental differences between HCT for NMDs and hematological malignancies, which may necessitate the use of alternative HCT strategies. For example, these diseases differ in the intensity of conditioning regimen sufficient to improve disease. In addition, patients with NMDs are at higher risk of graft failure or mixed chimerism following HCT, and gain no or little survival benefit from graft-versus-host disease. Because more than 80% of patients with NMDs become long-term survivors, greater attention has been paid to late adverse effects and decreased of quality of life after HCT. This review addresses several unresolved issues in allogeneic HCT for patients with NMDs, such as (1) stem cell source, (2) conditioning regimen, (3) use of serotherapy or low-dose irradiation, and (4) therapeutic intervention for mixed chimerism. Resolving these issues may improve transplant outcomes in patients with NMDs.

Optimizing Blood Stem Cell Transplants Through Cellular Engineering

Haematopoietic stem cell transplants (HSCT) are used in the treatment of blood cancers, autoimmune diseases, and metabolic disorders. Over 1.5 million transplants have been performed around the world thus far. In an attempt to enhance the efficacy of the cells used for transplantation, efforts are underway to use cellular engineering to increase cell numbers through: (1) the expansion of hematopoietic stem and progenitor cells (HSPC); (2) cellular subset selection to remove cells that cause graft-versus-host disease (GvHD), while adding back cells, which can mediate anti-tumor and anti-viral immunity; (3) the use of immune regulatory cells, such as mesenchymal stromal cells (MSC) and regulatory T cells (Tregs) to control GvHD; (4) the use of immune effector cells to mount immunological control of tumor cells before, after, or independent of blood stem cell transplants.

Results of a multicenter phase I/II trial of TCRαβ and CD19-depleted haploidentical hematopoietic stem cell transplantation for adult and pediatric patients

Hematopoietic stem cell transplantation (HSCT) from haploidentical donors is a viable option for patients lacking HLA-matched donors. Here we report the results of a prospective multicenter phase I/II trial of transplantation of TCRαβ and CD19-depleted peripheral blood stem cells from haploidentical family donors after a reduced-intensity conditioning with fludarabine, thiotepa, and melphalan. Thirty pediatric and 30 adult patients with acute leukemia (n = 43), myelodysplastic or myeloproliferative syndrome (n = 6), multiple myeloma (n = 1), solid tumors (n = 6), and non-malignant disorders (n = 4) were enrolled. TCR αβ/CD19-depleted grafts prepared decentrally at six manufacturing sites contained a median of 12.1 × 10⁶ CD34⁺ cells/kg and 14.2 × 10³ TCRαβ⁺ T-cells/kg. None of the patients developed grade lll/IV acute graft-versus-host disease (GVHD) and only six patients (10%) had grade II acute GVHD. With a median follow-up of 733 days 36/60 patients are alive. The cumulative incidence of non-relapse mortality at day 100, 1 and 2 years after HSCT was 5%, 15%, and 17% for all patients, respectively. Estimated probabilities of overall and disease-free survival at 2 years were 63% and 50%, respectively. Based on these promising results in a high-risk patient cohort, haploidentical HSCT using TCRαβ/CD19-depleted grafts represents a viable treatment option.

Role of Stem-Cell Transplantation in Leukemia Treatment

Stem cells (SCs) play a major role in advanced fields of regenerative medicine and other research areas. They are involved in the regeneration of damaged tissue or cells, due to their self-renewal characteristics. Tissue or cells can be damaged through a variety of diseases, including hematologic and nonhematologic malignancies. In regard to this, stem-cell transplantation is a cellular therapeutic approach to restore those impaired cells, tissue, or organs. SCs have a therapeutic potential in the application of stem-cell transplantation. Research has been focused mainly on the application of hematopoietic SCs for transplantation. Cord blood cells and human leukocyte antigen-haploidentical donors are considered optional sources of hematopoietic stem-cell transplantation. On the other hand, pluripotent embryonic SCs and induced pluripotent SCs hold promise for advancement of stem-cell transplantation. In addition, nonhematopoietic mesenchymal SCs play their own significant role as a functional bone-marrow niche and in the management of graft-vs-host disease effects during the posttransplantation process. In this review, the role of different types of SCs is presented with regard to their application in SC transplantation. In addition to this, the therapeutic value of autologous and allogeneic hematopoietic stem-cell transplantation is assessed with respect to different types of leukemia. Highly advanced and progressive scientific research has focused on the application of stem-cell transplantation on specific leukemia types. We evaluated and compared the therapeutic potential of SC transplantation with various forms of leukemia. This review aimed to focus on the application of SCs in the treatment of leukemia.