Treg-Enriched Stem Cell Transplant for Leukemia

Recruiting in Palo Alto (17 mi)

Overseen by John Koreth, MD

Age: 18+

Sex: Any

Travel: May Be Covered

Time Reimbursement: Varies

Trial Phase: Phase 1

Recruiting

Sponsor: Dana-Farber Cancer Institute

Must not be taking: Antiretrovirals, Investigational agents

Disqualifiers: HIV, Hepatitis B/C, Psychiatric illness, others

No Placebo Group

Trial Summary

What is the purpose of this trial?

This research study is evaluating the safety and efficacy of the IS-free Treg-cell graft-engineered haplo transplant method in people with relapsed/refractory and Ultra-high risk acute myeloid leukemia (AML) and/or myelodysplastic syndromes (MDS) receiving a haploidentical donor allogeneic hematopoietic stem cell transplant (HSCT). The names of the study interventions involved in this study are: * Radiation-Total Myeloid and Lymphoid Irradiation (TMLI * Chemotherapy (Fludarabine, Thiotepa, Cyclophosphamide plus Mesna) * Infusion of haplo Treg-enriched donor cells (experimental therapy) * Infusion of unmodified haplo donor T cells (includes cancer-fighting T effector cells) * Infusion of haplo donor CD34+ Peripheral Blood Stem Cells

Do I need to stop my current medications for the trial?

The trial protocol does not specify if you need to stop your current medications, but it mentions that you must avoid certain medications that interact with specific enzymes during a specific period (day -10 through day -5). It's best to discuss your current medications with the study team to ensure they don't interfere with the trial.

What data supports the effectiveness of the Treg-Enriched Stem Cell Transplant for Leukemia treatment?

Research shows that using fludarabine and thiotepa as part of a conditioning regimen can lead to successful engraftment and stable donor chimerism in patients, even those who are poor candidates for conventional treatments. Additionally, cyclophosphamide has been shown to enhance anti-tumor effects by reducing regulatory T cells, which may contribute to the effectiveness of the treatment.

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Is the Treg-Enriched Stem Cell Transplant for Leukemia generally safe for humans?

Research indicates that the combination of thiotepa and fludarabine, used in conditioning regimens for stem cell transplants, is generally well tolerated, with some studies reporting no major toxicity. However, other studies have noted regimen-related toxicity, including delayed pulmonary toxicity and graft-versus-host disease, which can be serious. Safety outcomes can vary based on the specific regimen and patient condition.

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What makes the Treg-Enriched Stem Cell Transplant for Leukemia treatment unique?

This treatment is unique because it combines Treg-enriched donor cells with traditional chemotherapy and radiation to enhance immune regulation and reduce complications like graft-versus-host disease (GVHD). The use of regulatory T cells (Tregs) is a novel approach that aims to improve the safety and effectiveness of stem cell transplants by promoting immune tolerance and reducing harmful immune responses.

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Eligibility Criteria

Adults aged 18-65 with relapsed/refractory acute myeloid leukemia (AML) or high-risk myelodysplastic syndromes (MDS), who have a compatible family donor, can join this trial. Participants need good heart, lung, and kidney function and must not be pregnant or breastfeeding. They should agree to use contraception during the study.

Inclusion Criteria

Ability to understand and the willingness to sign a written informed consent document

My liver function tests are within normal range, except for bilirubin which may be high due to Gilbert's Syndrome.

Pulmonary Function: FEV1, FVC and DLCO ≥ 60% of predicted (corrected for hemoglobin)

Exclusion Criteria

I do not have any uncontrolled infections.

I do not have hepatitis B or C.

I do not have cancer in areas like the brain, eyes, or testes.

Trial Timeline

Screening

Participants are screened for eligibility to participate in the trial

2-4 weeks

Radiation and Chemotherapy

Participants receive Total Myeloid and Lymphoid Irradiation (TMLI) and chemotherapy with Fludarabine, Thiotepa, Cyclophosphamide, and Mesna as a preparatory regimen

10 days

Daily visits for radiation and chemotherapy administration

Transplantation

Participants receive Treg-enriched donor cell infusion, unmodified donor T Cell infusion, and CD34+ Haplo Peripheral Blood Stem Cell Infusion

5 days

Daily visits for cell infusions and GVHD assessments

Follow-up

Participants are monitored for safety and effectiveness, including assessments of minimal residual disease (MRD) and graft vs host disease (GVHD)

12 months

Visits on days 30, 60, 100, 180, and 365 post-transplant

Participant Groups

The trial is testing an experimental stem cell transplant method using radiation, chemotherapy (Fludarabine, Thiotepa, Cyclophosphamide plus Mesna), and infusions of Treg-enriched donor cells along with unmodified haplo donor T cells and CD34+ Peripheral Blood Stem Cells in patients with AML/MDS.

Group I: IS-FREE TREG CRAFT_ENGINEERED HaploHCT for relapsed/refractory AML or MDS EB-2 (Closed to Accrual) Experimental Treatment 8 Interventions

Please note that this arm is closed due to meeting accrual goal as of June 2024. After meeting eligibility criteria and being enrolled, patients will receive: Day -15 to -6 prior to hematopoietic stem cell transplant (HSCT), preparatory regimen of radiation and chemotherapy: Total Myeloid and Lymphoid Irradiation (TMLI): Days -15 to -11 prior to HSCT; - Chemotherapy (infusion): Day -10 to day -6 prior to HSCT: Fludarabine (all days), Thiotepa (days -10 and -9) and Cyclophosphamide and Mesna (days -8 and -7) Day -4 prior to (HSCT), a Treg-enriched donor cell infusion and graft vs host disease (GVHD) assessment Day -1 prior to (HSCT), a unmodified donor T Cell infusion and (GVHD) assessment Day of (day 0) (HSCT), CD34+ Haplo Peripheral Blood Stem Cell Infusion/Transplant and (GVHD) assessment Days 30, 60,100, 180, 365 post hematopoietic stem cell transplant (HSCT), participants will undergo testing and assessment of minimal residual disease (MRD) and (GVHD)

Group II: IS-FREE TREG CRAFT_ENGINEERED HaploHCT for Ultra high-risk AML or MDS with mutated TP53 Experimental Treatment 8 Interventions

After meeting eligibility criteria and being enrolled, patients will receive: Day -15 to -6 prior to hematopoietic stem cell transplant (HSCT), preparatory regimen of radiation and chemotherapy: Total Myeloid and Lymphoid Irradiation (TMLI): Days -15 to -11 prior to HSCT; - Chemotherapy (infusion): Day -10 to day -6 prior to HSCT: Fludarabine (all days), Thiotepa (days -10 and -9) and Cyclophosphamide and Mesna (days -8 and -7) Day -4 prior to (HSCT), a Treg-enriched donor cell infusion and graft vs host disease (GVHD) assessment Day -1 prior to (HSCT), a unmodified donor T Cell infusion and (GVHD) assessment Day of (day 0) (HSCT), CD34+ Haplo Peripheral Blood Stem Cell Infusion/Transplant and (GVHD) assessment Days 30, 60,100, 180, 365 post hematopoietic stem cell transplant (HSCT), participants will undergo testing and assessment of minimal residual disease (MRD) and (GVHD)

Cyclophosphamide is already approved in United States, European Union, Canada, Japan for the following indications:

🇺🇸 Approved in United States as Cytoxan for:

• Breast cancer
• Ovarian cancer
• Multiple myeloma
• Leukemia
• Lymphoma
• Rheumatoid arthritis

🇪🇺 Approved in European Union as Endoxan for:

• Breast cancer
• Ovarian cancer
• Multiple myeloma
• Leukemia
• Lymphoma
• Rheumatoid arthritis

🇨🇦 Approved in Canada as Neosar for:

• Breast cancer
• Ovarian cancer
• Multiple myeloma
• Leukemia
• Lymphoma
• Rheumatoid arthritis

🇯🇵 Approved in Japan as Endoxan for:

• Breast cancer
• Ovarian cancer
• Multiple myeloma
• Leukemia
• Lymphoma

Find a Clinic Near You

Research Locations Nearby Select from list below to view details:

Dana Farber Cancer Institute Boston, MA

Who Is Running the Clinical Trial?

Dana-Farber Cancer Institute Lead Sponsor

References

1. United States pubmed.ncbi.nlm.nih.gov

A reduction of recipient regulatory T cells by cyclophosphamide contributes to an anti-tumor effect of nonmyeloablative allogeneic stem cell transplantation in mice. [2016] We have recently established a unique model system of nonmyeloablative allogeneic stem cell transplantation (SCT) for treatment of murine solid tumors, based on cyclophosphamide-induced tolerance. An injection of allogeneic donor spleen cells and bone marrow cells (BMC) followed by cyclophosphamide treatment induced a stable mixed chimerism with long lasting tolerance to the allografts. A donor lymphocyte infusion (DLI) in the cyclophosphamide-induced tolerant mice exerted strong anti-tumor effects on an MBT-2 murine bladder tumor, MBT-2 via their graft versus tumor (GVT) activity. In the present study, we determined whether a cyclophosphamide-induced reduction of naturally occurring regulatory T cells (Tregs) was associated with the anti-tumor activity in our nonmyeloablative SCT system. The number of recipient CD4+ CD25+ Foxp3+ Tregs significantly decreased 3 days after an intraperitoneal injection of cyclophosphamide in C3H/HeN mice that had been injected with spleen cells and BMC of donor AKR/J mice, compared with the number of CD4+ CD25+ Foxp3- T cells. An adoptive transfer of CD4+ CD25+ T cells from naïve C3H/He x AKR/J F1 mice into recipient mice 1 day after DLI significantly suppressed the expansion and IFN-γ production of host-reactive donor CD4+T cells and hampered the MBT-2 anti-tumor activity when compared with the transfer of CD4+ CD25- T cells. These results indicated that cyclophosphamide-induced reduction of recipient Tregs is associated with retardation of tumor progression via the expansion of host-reactive donor T cells and IFN-γ production after DLI in our nonmyeloablative SCT system.

2. England pubmed.ncbi.nlm.nih.gov

Non-radiotherapy conditioning with stem cell transplantation from alternative donors in children with refractory severe aplastic anemia. [2013] Conditioning including total body/lymphoid irradiation is widely used to prevent graft rejection in patients with refractory severe aplastic anemia (SAA) undergoing hemopoietic cell transplantation (HCT) from alternative donors and or after graft manipulation. To reduce regimen-related toxicity we transplanted three children with refractory SAA after conditioning with radiotherapy-free regimens. Conditioning included fludarabine 175-180 mg/m2 in all patients. In addition, patient 1 (failing two previous grafts) received thiotepa 10 mg/kg and Campath-1H 60 mg/m2; patient 2 cyclophosphamide 120 mg/kg, thiotepa 15 mg/kg and OKT-3 0.1 mg/kg/day for 4 weeks; and patient 3 cyclophosphamide 120 and ATG 90 mg/kg. Stem cell source was unmanipulated marrow from the same unrelated donor as for the two previous transplantations in patient 1 and CD34+-purified peripheral blood stem cells from an HLA-matched unrelated donor and from the haploidentical mother in patients 2 and 3. Only patient 1 received graft-versus-host disease (GVHD) prophylaxis with cyclosporine A and mycophenolate mofetil. Follow-up is now 30, 51, and 15 months. None of the patients developed GVHD. All patients have normal counts with complete donor chimerism. Fludarabine-based conditioning is powerfully immunosuppressive and may be used for children with refractory SAA undergoing HCT from alternative donors even after rejection following previous HCT.

3. England pubmed.ncbi.nlm.nih.gov

Safety and outcome after fludarabine-thiotepa-TBI conditioning for allogeneic transplantation: a prospective study of 30 patients with hematologic malignancies. [2013] Fludarabine, thiotepa and total body irradiation (TBI) has been used as conditioning in haplo-identical transplantation. We studied this conditioning regimen in adults undergoing matched sibling transplantation and alternative donor transplantation. A total of 30 consecutive patients underwent matched related, haplo-identical related or matched unrelated donor transplantation with fludarabine, thiotepa and TBI conditioning. All but four had advanced hematologic malignancies. For haplo-identical transplant, ATG was added to the regimen. All patients received peripheral blood stem cells; these were T-cell depleted for 2-antigen or 3-antigen mismatched related transplantation. Additional graft-versus-host disease prophylaxis consisted of tacrolimus and mini-methotrexate. One recipient of haplo-identical transplant failed to engraft; all other evaluable patients had prompt engraftment. Four patients died of regimen-related toxicity. In all, 14 additional patients died of regimen-related causes including four from failure to thrive with persistent thrombocytopenia and four from delayed pulmonary toxicity. Six patients relapsed. Progression-free survival at 12 months was 47% (90% CI: 25-69%) for recipients of HLA-identical sibling transplants and 30% (90% CI: 14-46%) for all patients. Five of six long-term survivors have extensive chronic GVHD. As a result of the delayed complications and a relatively high recurrence rate, we abandoned this regimen.

4. Germany pubmed.ncbi.nlm.nih.gov

Thiotepa and fludarabine (TT-FLUDA) as conditioning regimen in poor candidates for conventional allogeneic hemopoietic stem cell transplant. [2019] Standard conditioning for allogeneic bone marrow transplantation induces high transplant-related mortality (TRM) in patients with a poor performance status. Less intensive regimens have been tested to reduce the TRM; our purpose was to evaluate the feasibility and tolerability of a new combination: thiotepa and fludarabine (TT-FLUDA). Six patients received 5 mg thiotepa/kg daily from day -8 to -7 and 25 mg fludarabine/m2 daily from day -6 to -2 followed by an allogeneic peripheral blood progenitor cell infusion; three of these patients with signs of overt leukemia received 18 mg idarubicin/m2 i.v. at day -12. Graft-versus-host-disease (GVHD) prophylaxis was performed i.v. with 1 mg cyclosporine A/kg per day from day -5 to the day of marrow engraftment, then 6 mg/kg per day orally up to day +100, and 10 mg methotrexate/m2 at day +1, and 8 mg/m2 at days +3, +6, and +11. Chimerism was studied with fluorescent in situ hybridization for sex chromosomes (XY-FISH) and minisatellite polymerase chain reaction (PCR) at days +30, +100, +180, and +360. Engraftment was achieved in all cases with complete donor chimerism in all but one patient who had refractory acute leukemia. No major toxicity was noticed; only one patient died at day +51 of acute GVHD because of early cyclosporine A discontinuation. One patient with refractory non-Hodgkin's lymphoma (NHL) had a testicular relapse at day +180. Three patients (one with mantle cell lymphoma, two with acute myeloid leukemia) are still in continuous complete remission (CR) with complete donor chimerism at days +180, +210, and +450, respectively. TT-FLUDA seems to be well tolerated, allowing engraftment and stable donor chimerism in patients who are poor candidates for conventional conditioning regimens.

5. United States pubmed.ncbi.nlm.nih.gov

Bidirectional immune tolerance in nonmyeloablative MHC-mismatched BMT for murine β-thalassemia. [2021] Nonmyeloablative conditioning using total lymphoid irradiation (TLI) and rabbit antithymocyte serum (ATS) (the murine preclinical equivalent of antithymocyte globulin [ATG]) facilitates immune tolerance after bone marrow transplantation (BMT) across major histocompatibility complex (MHC) disparities and may be a useful strategy for nonmalignant disorders. We previously reported that donor effector T-cell function and graft-versus-host disease (GVHD) are regulated via recipient invariant natural killer T-cell (iNKT) interleukin-4-driven expansion of donor Foxp3+ naturally occurring regulatory T cells (Tregs). This occurs via recipient iNKT- and STAT6-dependent expansion of recipient myeloid dendritic cells (MDCs) that induce contact-dependent expansion of donor Treg through PD-1/PD ligand signaling. After TLI/ATS + BMT, Gr-1lowCD11c+ MDCs and Gr-1highCD11cneg myeloid-derived suppressor cells (MDSCs) were enriched in GVHD target organs. We now report that the recovery of both recipient MDSCs (P < .01) and MDCs (P < .01) is significantly increased when the alkylator cyclophosphamide (CTX) is added to TLI/ATS conditioning. In a BALB/c → B6 lethal GVHD model, adoptive transfer of MDSCs from TLI/ATS/CTX-conditioned recipients is associated with significantly improved GVHD colitis and survival (P < .001), conversion of MDSCs to PD ligand-expressing MDCs, and increased donor naturally occurring Treg recovery (P < .01) compared with control treatment. Using BALB/c donors and β-thalassemic HW-80 recipients, we found significantly improved rates of engraftment and GVHD following TLI/ATS/CTX compared with TLI/ATS, lethal or sublethal total body irradiation/ATS/CTX, or CTX/ATS conditioning. These data provide preclinical support for trials of TLI/ATG/alkylator regimens for MHC-mismatched BMT for hemoglobinopathies. The data also delineate innate immune mechanisms by which TLI/ATS/CTX conditioning may augment transplantation tolerance.

6. United States pubmed.ncbi.nlm.nih.gov

Post-transplantation cyclophosphamide for tolerance induction in HLA-haploidentical bone marrow transplantation. [2021] Allogeneic hematopoietic stem cell transplantation (alloSCT) is a potentially curative therapy for many hematologic and immunologic diseases. Further, partial or full donor hematopoietic chimerism following alloSCT may be sufficient to guarantee immunologic tolerance to solid organs from the same donor, obviating any requirement for prolonged pharmacologic immunosuppression. Despite alloSCT's potential, the procedure is beset by two major limitations. The first relates to the procedure's toxicity, including conditioning regimen toxicity, graft-versus-host disease (GVHD), and infection. The second limitation is the lack of histocompatible donors. A human leukocyte antigen (HLA)-matched sibling or unrelated donor cannot be identified expeditiously for up to 40% of patients. Historically, alloSCT from partially HLA-mismatched, or HLA-haploidentical, relatives has been complicated by unacceptably high incidences of graft rejection, severe GVHD, and non-relapse mortality. Recently, our groups have developed a method to selectively deplete alloreactive cells in vivo by administering high doses of cyclophosphamide in a narrow window after transplantation. Using high-dose, post-transplantation cyclophosphamide (PT/Cy), crossing the HLA barrier in alloSCT is now feasible and donors can be found for nearly all patients. This review discusses the history of HLA-haploidentical SCT, recent clinical results, and immunologic mechanisms of action of high-dose PT/Cy for prevention of graft rejection and GVHD.

7. England pubmed.ncbi.nlm.nih.gov

Thiotepa improves allogeneic bone marrow engraftment without enhancing stem cell depletion in irradiated mice. [2013] Thiotepa (TT) has long been considered for inclusion in clinical bone marrow transplant (BMT) conditioning regimens in an attempt to prevent allograft rejection and leukemia relapse. These studies have been encouraged by initial murine experiments showing a clear improvement in allogeneic bone marrow engraftment with addition of TT to total body irradiation (TBI) where it was assumed that TT enhances donor-type chimerism via ablation of competing stem cells in the recipient. The aim of the present study was to re-evaluate the hematological toxicity of TT among different stem cell subsets that included primitive cells capable of long-term repopulation and to assess how the combination of TT with TBI influences the development of donor engraftment in both syngeneic (B6-Gpi-1a --> B6-Gpi-1b) and H-2 compatible allogeneic (BALB.B10 --> B6) BMT models. At 24 h after TT (20 mg/kg) the femoral content of different stem cell subsets was determined from the frequency of transient repopulating, and the more primitive cobblestone area-forming, cells (CAFCs) growing in stroma-supported cultures. This assay showed a large TT-induced depletion (2% survival) of early clones developing at day 7 in culture but survival recovered towards normal for later appearing clones developing from more primitive CAFC subsets. The sparing of these primitive stem cells was reflected as undetectable levels of donor marrow repopulation in recipients given TT followed by syngeneic BMT. Addition of TT to TBI did not significantly improve long-term engraftment of syngeneic marrow while this combination had a dramatic effect in allogeneic BMT by preventing allograft rejection. In this respect TT shares similar properties with cyclophosphamide and suggests that the large improvement of allogeneic stem cell engraftment is attributable to the immune suppressive properties of TT rather than to its toxicity against host primitive stem cells.

8. Switzerland pubmed.ncbi.nlm.nih.gov

Post-Transplantation Cyclophosphamide Uniquely Restrains Alloreactive CD4+ T-Cell Proliferation and Differentiation After Murine MHC-Haploidentical Hematopoietic Cell Transplantation. [2022] Post-transplantation cyclophosphamide (PTCy) reduces the incidence and severity of graft-versus-host disease (GVHD), thereby improving the safety and accessibility of allogeneic hematopoietic cell transplantation (HCT). We have shown that PTCy works by inducing functional impairment and suppression of alloreactive T cells. We also have identified that reduced proliferation of alloreactive CD4+ T cells at day +7 and preferential recovery of CD4+CD25+Foxp3+ regulatory T cells (Tregs) at day +21 are potential biomarkers associated with optimal PTCy dosing and timing in our B6C3F1→B6D2F1 MHC-haploidentical murine HCT model. To understand whether the effects of PTCy are unique and also to understand better the biology of GVHD prevention by PTCy, here we tested the relative impact of cyclophosphamide compared with five other optimally dosed chemotherapeutics (methotrexate, bendamustine, paclitaxel, vincristine, and cytarabine) that vary in mechanisms of action and drug resistance. Only cyclophosphamide, methotrexate, and cytarabine were effective in preventing fatal GVHD, but cyclophosphamide was superior in ameliorating both clinical and histopathological GVHD. Flow cytometric analyses of blood and spleens revealed that these three chemotherapeutics were distinct in constraining conventional T-cell numerical recovery and facilitating preferential Treg recovery at day +21. However, cyclophosphamide was unique in consistently reducing proliferation and expression of the activation marker CD25 by alloreactive CD4+Foxp3- conventional T cells at day +7. Furthermore, cyclophosphamide restrained the differentiation of alloreactive CD4+Foxp3- conventional T cells at both days +7 and +21, whereas methotrexate and cytarabine only restrained differentiation at day +7. No chemotherapeutic selectively eliminated alloreactive T cells. These data suggest that constrained alloreactive CD4+Foxp3- conventional T-cell numerical recovery and associated preferential CD4+CD25+Foxp3+ Treg reconstitution at day +21 may be potential biomarkers of effective GVHD prevention. Additionally, these results reveal that PTCy uniquely restrains alloreactive CD4+Foxp3- conventional T-cell proliferation and differentiation, which may explain the superior effects of PTCy in preventing GVHD. Further study is needed to determine whether these findings also hold true in clinical HCT.

9. Egypt pubmed.ncbi.nlm.nih.gov

Regulatory T cells in allogeneic stem cell transplantation. [2021] Growing evidence suggests that cellular adoptive immunotherapy is becoming an attractive though challenging approach in regulating tumor immunity and alloresponses in clinical transplantation. Naturally arising CD4+CD25+Foxp3+ regulatory T cells (Treg) have emerged as a key component in this regard. Over the last decade, a large body of evidence from preclinical models has demonstrated their crucial role in auto- and tumor immunity and has opened the door to their "first-in-man" clinical application. Initial studies in clinical allogeneic stem cell transplantation are very encouraging and may pave the way for other applications. Further improvements in Treg ex vivo or in vivo expansion technologies will simplify their global clinical application. In this review, we discuss the current knowledge of Treg biology and their potential for cell-based immunotherapy in allogeneic stem cell transplantation.

10. United States pubmed.ncbi.nlm.nih.gov

Impact on early outcomes and immune reconstitution of high-dose post-transplant cyclophosphamide vs anti-thymocyte globulin after reduced intensity conditioning peripheral blood stem cell allogeneic transplantation. [2019] We have compared prospectively the outcome and immune reconstitution of patients receiving either post-transplant cyclophosphamide (PTCY) (n = 30) or anti-thymocyte globulin ATG (n = 15) as Graft-versus-host disease (GVHD) prophylaxis after reduced-intensity conditioning (RIC) allogeneic peripheral blood stem cell (PBSC) transplantation (allo-SCT). The outcome and immune reconstitution of patients receiving either of these two regimens were compared prospectively. This study allowed also to investigate the impact of PTCY between haplo-identical vs matched donors and of clofarabine as part of the RIC regimen. The γ/δ T-cells, α/β T-cells (CD8+ and CD4+), NK T-cells, NK cells, B-cells, Tregs and monocytes were analyzed by flow cytometry from a total of 583 samples. In the PTCY group significant delayed platelets recovery, higher CD3+ donor chimerism, higher HHV-6 and lower EBV reactivations were observed. Early survival advantage for CD4+ T-cells, Tregs and α/β T-cells was documented in the PTCY group while it was the case for α/β T-cells, NK cells and monocytes in the ATG group. Higher counts of NK and monocytes were observed at days +30 and/or day+60 in the ATG group. Both results were retained even in the case of mismatched donors. However, higher percentages of CD4+ T-cells, α/β T-cells and Tregs were observed with haplo-identical donors in the PTCY group. Finally, clofarabine was responsible for early survival advantage of NK T-cells in the PTCY group while it abrogated the early survival advantage of γ/δ T-cells in the ATG group. In conclusion, there are marked differences in the immunological effects of ATG vs PTCY as GVHD prophylaxis for RIC PBSC allo-SCT.

11. United States pubmed.ncbi.nlm.nih.gov

Durable engraftment of major histocompatibility complex-incompatible cells after nonmyeloablative conditioning with fludarabine, low-dose total body irradiation, and posttransplantation cyclophosphamide. [2021] Treatment of leukemia by myeloablative conditioning and transplantation of major histocompatibility complex (MHC)-mismatched stem cells is generally avoided because of the high risk of graft rejection or lethal graft-versus-host disease (GVHD). This study shows that MHC-incompatible cells can engraft stably after nonmyeloablative conditioning with immunosuppressive chemotherapy and low-dose total body irradiation (TBI). Long-term mixed hematopoietic chimerism, clonal deletion of donor-reactive T cells, and bidirectional cytotoxic T-cell tolerance were achieved by transplanting MHC-mismatched marrow cells into recipients conditioned with pretransplantation fludarabine or cyclophosphamide (Cy), 50 to 200 cGy TBI on day -1, and Cy 200 mg/kg intraperitoneally on day 3. In this model, long-term donor chimerism was proportional to the dose of TBI or donor marrow cells. Pretransplantation fludarabine and posttransplantation Cy were both required for alloengraftment, but the drugs had additional effects. For example, fludarabine sensitized host stem cells to the toxicity of TBI, because animals conditioned with both agents had higher chimerism than animals conditioned with TBI alone (P