Reduced Intensity Conditioning for Allogeneic Hematopoietic Cell Transplantation: Current Perspectives

AbstractAllogeneic HCT after myeloablative conditioning is an effective therapy for patients with hematologic malignancies. In an attempt to extend this therapy to older patients or those with comorbidities, reduced intensity or truly nonmyeloablative regimens have been developed over the past decade. The principle underlying reduced intensity regimens is to provide some tumor kill with lessened regimen-related morbidity and mortality and then rely on graft-versus-tumor (GVT) effects to eradicate remaining malignant cells, whereas nonmyeloablative regimens rely primarily on GVT effects. In this article, 3 representative approaches are described, demonstrating the clinical application for hematopoietic and nonhematopoietic malignancies. Current challenges include controlling GVHD while allowing GVT to occur. In the future, clinical trials using reduced intensity and nonmyeloablative conditioning will be compared with myeloablative conditioning in selected malignancies to extend the application to standard-risk patients

Intracellular Disposition of Fludarabine Triphosphate in Human Natural Killer Cells

Purpose. Fludarabine is a key component of several reduced-intensity conditioning regimens for hematopoietic cell transplantation (HCT). Shortly after reduced-intensity conditioning, the percent of donor natural killer (NK) cells has been associated with progression-free survival. Insufficient suppression of the recipient’s NK cells by fludarabine may lead to lower donor chimerism; however, the effect of fludarabine upon NK cells is poorly understood. Thus, in purified human NK cells we evaluated the uptake and activation of fludarabine to its active metabolite, fludarabine triphosphate (F-ara-ATP), and assessed the degree of interindividual variability in F-ara-ATP accumulation. Methods. Intracellular F-ara-ATP was measured in purified NK cells isolated from healthy volunteers (n = 6) after ex vivo exposure to fludarabine. Gene expression levels of the relevant transporters and enzymes involved in fludarabine uptake and activation were also measured in these cells. Results. F-ara-ATP accumulation (mean ± s.d.) was 6.00 ± 3.67 pmol/1x106 cells/4 hours, comparable to average levels previously observed in CD4+ and CD8+ T-lymphocytes. We observed considerable variability in F-ara-ATP accumulation and mRNA expression of transporters and enzymes relevant to F-ara-ATP accumulation in NK cells from different healthy volunteers. Conclusions. Human NK cells have the ability to form F-ara-ATP intracellularly and large interindividual variability was observed in healthy volunteers. Further studies are needed to evaluate whether F-ara-ATP accumulation in NK cells are associated with apoptosis and clinical outcomes

Biodistributions, Myelosuppression and Toxicities in Mice Treated with an Anti-CD45 Antibody Labeled with the α-Emitting Radionuclides Bismuth-213 or Astatine-211

We previously investigated the potential of targeted radiotherapy using a bismuth-213- labeled anti-CD45 antibody to replace total body irradiation as conditioning for hematopoietic cell transplantation in a canine model. While this approach allowed sustained marrow engraftment, limited availability, high cost and short half-life of bismuth-213 induced us to investigate an alternative α-emitting radionuclide, astatine-211, for the same application. Biodistribution and toxicity studies were conducted with conjugates of the anti-murine CD45 antibody 30F11 with either bismuth-213 or astatine-211. Mice were injected with 2-50 μCi on 10 μg or 20 μCi on 2 or 40 μg 30F11 conjugate. Biodistribution studies showed that the spleen contained the highest concentration of radioactivity, ranging from 167±23 to 417±109 % injected dose/gram (%ID/g) after injection of the astatine-211 conjugate and 45±9 to 166±11 %ID/g after injection of the bismuth-213 conjugate. The higher concentrations observed for astatine-211- labeled 30F11 were due to its longer half-life, which permitted better localization of isotope to the spleen before decay. Astatine-211 was more effective at producing myelosuppression for the same quantity of injected radioactivity. All mice injected with 20 or 50 μCi astatine-211 but none with the same quantities of bismuth-213 had lethal myeloablation. Severe reversible acute hepatic toxicity occurred with 50 μCi bismuth-213, but not with lower doses of bismuth-213 or with any dose of astatine-211. No renal toxicity occurred with either radionuclide. The data suggest that smaller quantities of astatine-211-labeled anti-CD45 antibody are sufficient to achieve myelosuppression and myeloablation with less non-hematological toxicity compared with bismuth-213-labeled antibody

A Phase I/II Study of Chemotherapy Followed by Donor Lymphocyte Infusion plus Interleukin-2 for Relapsed Acute Leukemia after Allogeneic Hematopoietic Cell Transplantation

The efficacy of donor lymphocyte infusion (DLI) for treatment of relapsed acute leukemia after allogeneic hematopoietic cell transplantation is limited. We hypothesized that interleukin-2 (IL-2) combined with DLI after chemotherapy might augment graft-versus-leukemia effects. To identify a safe and effective IL-2 regimen, a phase I/II study of DLI plus IL-2 therapy was performed for such patients. After chemotherapy, 17 patients received DLI (1 × 108 CD3/kg for patients with related donors, and 0.1 × 108 CD3/kg for those with unrelated donors) and an escalating dose of induction IL-2 (1.0, 2.0, or 3.0 × 106 IU/m2/day representing levels I [n = 7], Ia [n = 9], and II [n = 1]) for 5 days followed by maintenance (1.0 × 106 IU/m2/day) for 10 days as a continuous intravenous infusion. Unacceptable IL-2–related toxicities developed in 1 patient at level I, 2 at level Ia, and 1 at level II. Grades III-IV acute graft-versus-host disease (aGVHD) developed in 5 patients, and extensive chronic GVHD (cGVHD) developed in 8. Eight patients had a complete remission after chemotherapy prior to DLI, and 2 additional patients had a complete remission after DLI plus IL-2 therapy. In conclusion, the maximal tolerated induction dose of IL-2 combined with DLI appears to be 1.0 × 106 IU/m2/day. IL-2 administration after DLI might increase the incidence of cGVHD

Conditioning intensity and peritransplant flow cytometric MRD dynamics in adult AML

In acute myeloid leukemia (AML), measurable residual disease (MRD) before or after allogeneic hematopoietic cell transplantation (HCT) is an established independent indicator of poor outcome. To address how peri-HCT MRD dynamics could refine risk assessment across different conditioning intensities, we analyzed 810 adults transplanted in first or second remission after myeloablative conditioning (MAC; n = 515) or non-MAC (n = 295) who underwent multiparameter flow cytometry–based MRD testing before as well as 20 to 40 days after allografting. Patients without pre- and post-HCT MRD (MRDneg/MRDneg) had the lowest risks of relapse and highest relapse-free survival (RFS) and overall survival (OS). Relative to those patients, outcomes for MRDpos/MRDpos and MRDneg/MRDpos patients were poor regardless of conditioning intensity. Outcomes for MRDpos/MRDneg patients were intermediate. Among 161 patients with MRD before HCT, MRD was cleared more commonly with a MAC (85 of 104; 81.7%) than non-MAC (33 of 57; 57.9%) regimen (P = .002). Although non-MAC regimens were less likely to clear MRD, if they did, the impact on outcome was greater. Thus, there was a significant interaction between conditioning intensity and “MRD conversion” for relapse (P = .020), RFS (P = .002), and OS (P = .001). Similar findings were obtained in the subset of 590 patients receiving HLA-matched allografts. C-statistic values were higher (indicating higher predictive accuracy) for peri-HCT MRD dynamics compared with the isolated use of pre-HCT MRD status or post-HCT MRD status for prediction of relapse, RFS, and OS. Across conditioning intensities, peri-HCT MRD dynamics improve risk assessment over isolated pre- or post-HCT MRD assessments in patients with AML

C19orf48 encodes a minor histocompatibility antigen recognized by CD8+ cytotoxic T cells from renal cell carcinoma patients.

PURPOSE: Tumor regression has been observed in some patients with metastatic renal cell carcinoma (RCC) after nonmyeloablative allogeneic hematopoietic cell transplantation (HCT). Cellular and molecular characterization of antigens recognized by tumor-reactive T cells isolated from responding patients could potentially provide insight into the mechanisms of tumor regression. EXPERIMENTAL DESIGN: CD8+ CTL clones that recognized a novel RCC-associated minor histocompatibility (H) antigen presented by HLA-A*0201 were isolated from two patients with metastatic RCC who experienced tumor regression or stable disease following nonmyeloablative allogeneic HCT. These clones were used to screen a cDNA library and isolate the unique cDNA encoding the antigen. RESULTS: An alternative open reading frame in the C19orf48 gene located on chromosome 19q13 encodes the HLA-A*0201-restricted minor H antigen recognized by the RCC-reactive T cells. The differential T-cell recognition of donor- and recipient-derived target cells is attributable to a nonsynonymous single-nucleotide polymorphism within the nucleotide interval that encodes the antigenic peptide. Assays for gene expression and CTL recognition showed that the C19orf48-encoded peptide is widely expressed in renal tumors and solid tumors of other histologies. The antigenic peptide can be processed for CTL recognition via both TAP-dependent and TAP-independent pathways. CONCLUSIONS: Donor T-cell responses against the HLA-A*0201-restricted minor H antigen encoded by C19orf48 may contribute to RCC regression after MHC-matched allogeneic HCT

Conditioning Intensity, Pre-Transplant Flow Cytometric Measurable Residual Disease, and Outcome in Adults with Acute Myeloid Leukemia Undergoing Allogeneic Hematopoietic Cell Transplantation

How conditioning intensity is related to outcomes of AML patients undergoing allografting in morphologic remission is an area of great ongoing interest. We studied 743 patients in morphologic remission and known pre-transplant measurable residual disease (MRD) status determined by multiparameter flow cytometry (MFC) who received a first allograft after myeloablative, reduced intensity, or nonmyeloablative conditioning (MAC, RIC, and NMA). Overall, relapse-free survival (RFS) and overall survival (OS) were longer after MAC than RIC or NMA conditioning, whereas relapse risks were not different. Among MRD(pos)patients, 3-year estimates of relapse risks and survival were similar across conditioning intensities. In contrast, among MRD(neg)patients, 3-year RFS and OS were longer for MAC (69% and 71%) than RIC (47% and 55%) and NMA conditioning (47% and 52%). Three-year relapse risks were lowest after MAC (18%) and highest after NMA conditioning (30%). Our data indicate an interaction between conditioning intensity, MFC-based pre-transplant MRD status, and outcome, with benefit of intensive conditioning primarily for patients transplanted in MRD(neg)remission. Differing from recent findings from other studies that indicated MAC is primarily beneficial for some or all patients with MRD(pos)pre-HCT status, our data suggest MAC should still be considered for MRD(neg)AML patients if tolerated

Nonmyeloablative Unrelated Donor Hematopoietic Cell Transplantation to Treat Patients with Poor-Risk, Relapsed, or Refractory Multiple Myeloma

AbstractThe purpose of this study was to determine long-term outcome of unrelated donor nonmyeloablative hematopoietic cell transplantation (HCT) in patients with poor-risk multiple myeloma. A total of 24 patients were enrolled; 17 patients (71%) had chemotherapy-refractory disease, and 14 (58%) experienced disease relapse or progression after previous autologous transplantation. Thirteen patients underwent planned autologous transplantation followed 43–135 days later with unrelated transplantation, whereas 11 proceeded directly to unrelated transplantation. All 24 patients were treated with fludarabine (90 mg/m2) and 2 Gy of total body irradiation before HLA-matched unrelated peripheral blood stem cell transplantation. Postgrafting immunosuppression consisted of cyclosporine and mycophenolate mofetil. The median follow-up was 3 years after allografting. One patient experienced nonfatal graft rejection. The incidences of acute grades II and III and chronic graft-versus-host disease were 54%, 13%, and 75%, respectively. The 3-year nonrelapse mortality (NRM) was 21%. Complete responses were observed in 10 patients (42%); partial responses, in 4 (17%). At 3 years, overall survival (OS) and progression-free survival (PFS) rates were 61% and 33%, respectively. Patients receiving tandem autologous-unrelated transplantation had superior OS and PFS (77% and 51%) compared with patients proceeding directly to unrelated donor transplantation (44% and 11%) (PFS P value = .03). In summary, for patients with poor-risk, relapsed, or refractory multiple myeloma, cytoreductive autologous HCT followed by nonmyeloablative conditioning and unrelated HCT is an effective treatment approach, with low NRM, high complete remission rates, and prolonged disease-free survival

Effect of conditioning regimen intensity on CMV infection in allogeneic hematopoietic cell transplantation.

Nonmyeloablative conditioning is less toxic and results in initial establishment of mixed hematopoietic T cell chimerism for up to half a year with prolonged presence of host T cell immunity. In this study, we examined whether this translates into differences in the risks and/or severity of cytomegalovirus (CMV) infection and disease. We analyzed data from 537 nonmyeloablative (NM-HCT) and contemporaneous 2489 myeloablative hematopoietic cell transplant (M-HCT) recipients. In CMV seropositive recipients, no difference in the overall hazards of CMV infection at any level (adjusted hazard ratio [adj. HR] 0.9, 95% confidence interval [95% CI]: 0.7-1.0, P = .14) was noted; however, NM-HCT was associated with a lower risk of high-grade CMV infection (adj. HR 0.7, 95% CI: 0.5-0.9, P = .02). CMV disease rates were similar between the groups during the first 100 days after HCT, but NM-HCT recipients had an increased risk of late CMV disease (adj. HR 2.0, 95% CI 1.2-3.4). The increased risk of late CMV disease after NM-HCT was pronounced during the earlier years of the study period, but not detectable in more recent years. Contrary to earlier reports, survival following CMV disease was not reduced after NM-HCT when compared to M-HCT recipients. These results suggest that residual host cells after NM-HCT reduce progression to higher CMV viral load in NM-HCT recipients; however, this effect does not appear to protect against serious complications of CMV. Therefore, CMV prevention strategies in NM-HCT recipients should be similar to those used in M-HCT recipients