T Cell Depletion as an Alternative Approach for Patients 55 Years or Older Undergoing Allogeneic Stem Cell Transplantation as Curative Therapy for Hematologic Malignancies

Transplantation and Cellular Therapy for Older Adults-The MSK Approach

PURPOSE OF REVIEW

Hematologic malignances more commonly affect older individuals and often present with advanced, higher risk disease than younger patients. Allogeneic and autologous hematopoietic cell transplantation is well-established treatment modalities with curative potential following either frontline treatments for these diseases or salvage therapy in the relapsed or refractory setting. More recently, novel cellular immunotherapy such as chimeric antigen receptor T-cell therapy has been shown to lead to high response rate and durable remission in many patients with advanced blood cancers.

RECENT FINDINGS

Given unique characteristics of older patients, how best to deliver these higher-intensity and time sensitive treatment modalities for them remains challenging. Moreover, their short-term and potential long-term impact on their functional status, cognitive status, and quality of life may be significant considerations for many older patients. All these issues contributed to the lack of access and significant underutilization of these potential curative treatment strategies. In this review, we present up to date evidence to support potential benefits of transplantation and cellular therapy for older adults, their steady improving outcomes, and most importantly, highlight the use of geriatric assessment to help select appropriate older patients and optimize them prior to and following transplantation and cellular therapy. We specifically describe our approach at Memorial Sloan Kettering Cancer Center and encouraging early results from its implementation.

Combining the Disease Risk Index and Hematopoietic Cell Transplant Co-Morbidity Index provides a comprehensive prognostic model for CD34+-selected allogeneic transplantation

T cell depletion by CD34⁺ cell selection of hematopoietic stem cell allografts ex vivo reduces the incidence and severity of GvHD, without increased risk of relapse in patients with acute leukemia in remission or MDS. The optimal candidate for CD34⁺-selected HCT remains unknown, however.

OBJECTIVE

To determine outcomes based on both disease- and patient-specific factors, we evaluated a prognostic model combining the Disease Risk Index (DRI) and Hematopoietic Cell Transplantation Comorbidity Index (HCT-CI), an approach recently shown to predicted overall survival in a broad population of allograft recipients (1).

METHODS

This was a retrospective analysis of 506 adult recipients of first allogeneic HCT with CD34+ selected PBSCs from 7/8- or 8/8-matched donors for AML (n = 290), ALL (n = 72), or MDS (n = 144). The Kaplan-Meier method estimated OS and RFS. The cumulative incidence method for competing risks estimated relapse and non-relapse mortality (NRM). We evaluated the univariate association between variables of interest and OS and RFS using the log-rank test. Cox regression models assessed the adjusted effect of covariates on OS/RFS.

RESULTS

Stratification of patients based on a composite of DRI (low/intermediate vs. high/very high) and HCT-CI (0-2 vs. ≥ 3) revealed differences in OS and RFS between the 4 groups. Compared with reference groups of patients with low/intermediate DRI and low or high HCT-CI, those with high DRI had a greater risk of death (HR 2.30; 95% CI 1.39, 3.81) and relapse or death (HR 2.50; 95% CI 1.55, 4.05) than patients with any HCT-CI but low/intermediate DRI (HR death 1.80; 95% CI 1.34, 2.43; HR relapse/death 1.68; 95% CI 1.26, 2.24).

CONCLUSIONS AND CLINICAL IMPLICATIONS

A model combining DRI and HCT-CI predicted survival after CD34⁺ cell-selected HCT. Application of this combined model to other cohorts, both in retrospective analyses and prospective trials, will enhance clinical decision making and patient selection for different transplant approaches.

DATA AVAILABILITY STATEMENT

The data that support the findings of this study are available on request from the corresponding author, C Cho. In order to protect the privacy of research participants, the data are not publicly available.

Ex vivo T-cell depletion vs post-transplant cyclophosphamide, sirolimus, and mycophenolate mofetil as graft-vs-host disease prophylaxis for allogeneic hematopoietic stem cell transplantation

OBJECTIVE

To compare the efficacy and safety of CD34+ selected ex vivo T-cell depletion (TCD) vs post-transplant cyclophosphamide, sirolimus, and mycophenolate mofetil (PTCy-Sir-MMF) as graft-vs-host disease (GVHD) prophylaxis.

METHODS

We retrospectively included patients who underwent allogeneic hematopoietic stem cell transplantation (allo-HSCT) with either TCD (n = 38) or PTCy-Sir-MMF (n = 91).

RESULTS

Cumulative incidence of neutrophil and platelet recovery was 92% vs 99% (P = .06) and 89% vs 97% (P = .3) in TCD and PTCy-Sir-MMF, respectively. Cumulative incidences of aGHVD grade II-IV, III-IV, and moderate to severe cGVHD were 11% vs 19% (P = .2), 3% vs 2% (P = .9), and 3% vs 36% (P < .001) in TCD and PTCy-Sir-MMF, respectively. The 2-year non-relapse mortality, relapse, disease-free and overall survival were 25% vs 8% (P = .01), 20% vs 16% (P = .2), 55% vs 76% (P = .004), 57% vs 83% (P = .004) for TCD and PTCy-Sir-MMF, respectively. Cumulative incidence of cytomegalovirus and Epstein-Barr infection requiring therapy was 76% vs 40% (P < .001) and 32% vs 0% (P < .001) in TCD and PTCy-Sir-MMF, respectively. PTCy-Sir-MMF platform showed faster T-cell reconstitution.

CONCLUSIONS

PTCy-Sir-MMF provides better survival outcomes but is associated with higher risk of cGVHD compared to TCD.

Checkpoint inhibitors in AML: are we there yet?

Immunotherapy is distinct from traditional chemotherapy in that it acts on immune cells rather than cancer cells themselves. Monoclonal antibodies targeting immune checkpoints on T cells - CTLA-4 and PD-1 - and PD-L1 on the cells of immune microenvironment are now approved for clinical use in several solid tumors and hematological malignancies. This article provides a general overview of the use of checkpoint inhibitors in hematologic malignancies with a special focus in acute myeloid leukemia.

Ex Vivo T Cell-Depleted Hematopoietic Stem Cell Transplantation for Adult Patients with Acute Myelogenous Leukemia in First and Second Remission: Long-Term Disease-Free Survival with a Significantly Reduced Risk of Graft-versus-Host Disease

Large series of patients with acute myelogenous leukemia (AML) after ex vivo T cell-depleted (TCD) allogeneic hematopoietic stem cell transplantation (allo-HSCT) have not been reported previously. We retrospectively analyzed the outcomes of 266 patients (median age, 54 years) with AML who received CD34-selected TCD allo-HSCTs while in first (75%) or second (25%) complete remission (CR1/CR2) at a single institution. The conditioning regimens were all myeloablative, and no additional graft-versus-host disease (GVHD) prophylaxis was given. The cumulative incidences of grade II-IV and grade III-IV acute GVHD at 180 days were 14% (95% confidence interval [CI], 10% to 18%) and 3% (95% CI, 1% to 5%), respectively. The cumulative incidence of chronic GVHD at 3 years was 3% (95% CI, 1% to 6%). The 3-year cumulative incidence of nonrelapse mortality was 21% (95% CI, 16% to 26%) and that of relapse was 21% (95% CI, 17% to 27%). Overall survival (OS) and disease-free survival (DFS) at 1, 3, and 5 years were 75%, 61%, and 56% and 68%, 57%, and 53%, respectively. There were no significant differences in OS, DFS, and relapse rates for patients who underwent transplantation in CR1 and those who did so in CR2. However, patients with high-risk cytogenetics at diagnosis had significantly poorer outcomes. The OS and DFS rates compare favorably with those for unmodified allo-HSCT, but with considerably lower rates of GVHD.

Allogeneic Stem Cell Transplantation with CD34+ Cell Selection

The success of allogeneic stem cell transplant is hampered by the development of acute and chronic graft-versus-host disease (GvHD) which has direct impact on treatment-related mortality and morbidity. As a result, T cell depletion through positive selection of CD34+ cells has emerged as a promising strategy to reduce acute and chronic GvHD in these patients.

In this review, we summarize the main characteristics of allogeneic stem cell transplant with CD34+ cell selection including risks of graft failure, GvHD, infection, organ toxicity, and long-term survival. Moreover, we highlight future strategies to improve the results of this platform and to consolidate its use in clinical practice.

Advances in Ex Vivo T Cell Depletion - Where Do We Stand?

Graft-versus-host (GVHD) is an important cause of morbidity and mortality after allogeneic hematopoietic cell transplantation (HCT). As donor T cells are recognized as key drivers of GVHD, some approaches to prevent GVHD have focused on T cell depletion of the allograft. In this review we summarize methods and outcomes of ex vivo T cell depleted (TCD) HCT with a focus on CD34+ selection. This platform is efficacious in preventing acute and chronic GVHD across a wide range of hematologic malignancies, and with the exception of chronic myeloid leukemia, is not associated with adverse relapse or survival outcomes compared to conventional GVHD prophylaxis platforms. In retrospective comparisons recipients of CD34+ selected HCT have higher rates of GVHD-free relapse-free survival (GRFS) than conventional HCT counterparts. Although CD34+ selected allografts require myeloablative and antithymocyte-globulin based conditioning to support engraftment, abrogation of calcineurin inhibitors and methotrexate in this approach reduces its toxicity such that it can be considered in select older and more comorbid patients who could benefit from ablative HCT. A trial comparing GVHD prophylaxis regimens (BMT CTN 1301, NCT02345850) has completed accrual and will be the first to compare CD34+ selected HCT with conventional HCT in a randomized prospective setting. Its findings have potential to establish CD34+ selected HCT as a new standard-of-care platform for GVHD prevention.

Cytomegalovirus Infection in Allogeneic Hematopoietic Cell Transplantation Managed by the Preemptive Approach: Estimating the Impact on Healthcare Resource Utilization and Outcomes

We quantified cytomegalovirus (CMV) antiviral use and hospital length of stay (LOS) associated with CMV infection in a contemporary cohort of conventional (CONV) and CD34-selected (T cell-depleted) hematopoietic cell transplantation (HCT) recipients managed by preemptive therapy (PET) in a single US center. Adults who received first allogeneic HCT at Memorial Sloan Kettering Cancer Center from June 2010 through December 2014 were analyzed. Days on PET, number of readmissions, and readmission LOS by day 180 post-HCT were summarized. Estimated unit value (EUV) was defined as the expected number of PET days for a cohort of 100 HCT with characteristics as the analyzed cohort. Standardized incidence ratio was calculated as the ratio of observed outcomes of patients with CMV viremia over the outcomes of patients without CMV viremia. Of 318 patients, 88 received CONV and 230 CD34-selected HCT. Rates of CMV viremia were 26.3% for CONV and 41.9% for CD34-selected (P = .003). Among patients with viremia 68.2% CONV and 97.9% CD34-selected received PET. EUV for PET was 852 days and 2821 days for CONV and CD34-selected, respectively. The standardized incidence ratios for number of readmission and readmission LOS were 1.7 (95% confidence interval [CI], 1.4 to 2.1) and 1.2 (95% CI, 1.1 to 1.3), respectively, for CONV HCT and 1.7 (95% CI, 1.3 to 2.1) and 1.6 (95% CI, 1.5 to 1.7), respectively, for CD34-selected HCT. Overall survival was similar between patients with and without CMV viremia by HCT type. CMV end-organ disease was associated with lower overall survival only in CD34-selected HCT (P = .0007). CMV infection managed by PET requires substantial antiviral use and is associated with longer readmission LOS more, particularly among CD34-selected HCT.

The case for plerixafor to replace filgrastim as the optimal agent to mobilize peripheral blood donors for allogeneic hematopoietic cell transplantation

Granulocyte colony-stimulating factor (G-CSF)-stimulated peripheral blood progenitor cells (G-PBs) from either a related or unrelated donor continue to be the preferred donor source for most allogeneic hematopoietic cell transplantation (HCT). Recently, the American Society for Blood and Marrow Transplantation has recommended marrow instead of G-PBs as an unrelated graft source due to its lower rate of chronic graft-versus-host disease (cGVHD). However, the use of marrow is limited by both clinical considerations (slower rate of engraftment and increased donor morbidity) and logistical considerations (use of operating room resources and increased physician utilization), so this recommendation has not been widely adopted. An optimal donor source would include the rapid engraftment characteristic and the low donor morbidity associated with G-PBs and a rate of cGVHD similar to or lower than that of marrow. Recent data suggest that plerixafor mobilized PBs (P-PBs) have the rapid engraftment characteristics of G-PBs in allogeneic HCT with less cGVHD. The biologic mechanism of the lower rate of cGVHD appears to be through mobilization of regulator natural killer cells and plasmacytoid dendritic cell precursors that are associated with lower acute and chronic GVHD compared with G-PBs and rapid engraftment characterized by rapid myeloid-repopulating capacity. We suggest that, based on the experience of the two Phase II clinical trials and the unique biology of plerixafor-mobilized donor product, it should be evaluated in Phase III trials as an approach to replacing G-CSF mobilization for allogeneic HCT.

Ex vivo and in vivo T cell-depleted allogeneic stem cell transplantation in patients with acute myeloid leukemia in first complete remission resulted in similar overall survival: on behalf of the ALWP of the EBMT and the MSKCC

Background

Graft-versus-host disease (GVHD) is one of the leading causes of non-relapse mortality and morbidity after allogeneic hematopoietic stem cell transplantation (allo-HCT).

Methods

We evaluated the outcomes of two well-established strategies used for GVHD prevention: in vivo T cell depletion using antithymocyte globulin (ATG) and ex vivo T cell depletion using a CD34-selected (CD34+) graft. A total of 525 adult patients (363 ATG, 162 CD34+) with intermediate or high-risk cytogenetics acute myeloid leukemia (AML) in first complete remission (CR1) were included. Patients underwent myeloablative allo-HCT using matched related or unrelated donors.

Results

Two-year overall survival estimate was 69.9% (95% CI, 58.5–69.4) in the ATG group and 67.6% (95% CI, 60.3–74.9) in the CD34+ group (p = 0.31). The cumulative incidence of grade II–IV acute GVHD and chronic GVHD was higher in the ATG cohort [HR 2.0 (95% CI 1.1–3.7), p = 0.02; HR 15.1 (95% CI 5.3–42.2), p < 0.0001]. Parameters associated with a lower GVHD-free relapse-free survival (GRFS) were ATG [HR 1.6 (95% CI 1.1–2.2), p = 0.006], adverse cytogenetic [HR 1.7 (95% CI 1.3–2.2), p = 0.0004], and the use of an unrelated donor [HR 1.4 (95% CI 1.0–1.9), p = 0.02]. There were no statistical differences between ATG and CD34+ in terms of relapse [HR 1.52 (95% CI 0.96–2.42), p = 0.07], non-relapse mortality [HR 0.96 (95% CI 0.54–1.74), p = 0.90], overall survival [HR 1.43 (95% CI 0.97–2.11), p = 0.07], and leukemia-free survival [HR 1.25 (95% CI 0.88–1.78), p = 0.21]. Significantly, more deaths related to infection occurred in the CD34+ group (16/52 vs. 19/112, p = 0.04).

Conclusions

These data suggest that both ex vivo CD34-selected and in vivo ATG T cell depletion are associated with a rather high OS and should be compared in a prospective randomized trial.

Electronic supplementary material

The online version of this article (10.1186/s13045-018-0668-3) contains supplementary material, which is available to authorized users.

Cytomegalovirus resistance in CD34+ -selected hematopoietic cell transplant recipients

BACKGROUND

Cytomegalovirus (CMV) viremia after CD34+ -selected hematopoietic stem cell transplant (HCT) often requires prolonged antiviral therapy. We report rates and outcomes of resistant CMV in a contemporary cohort of CD34+ -selected HCT recipients managed preemptively.

METHODS

We retrospectively reviewed 220 consecutive, CMV-seropositive recipients (R+), who received CD34+ -selected HCT at Memorial Sloan Kettering Cancer Center between June 2010 and December 2014. Patients were monitored by quantitative CMV PCR and were treated preemptively. CMV resistance was tested by a genotypic assay.

RESULTS

One hundred and sixty-one (73%) patients developed CMV viremia and 47 (29% of viremic and 21% of total patients) had CMV resistance testing by one-year from HCT. CMV resistance was confirmed in 19 (12% of viremic and 9% of total) patients and was identified >3 months from HCT in 90% of patients. Twelve patients had mutations in UL97 only; the remaining 7 patients had mutations in UL54 only or UL54 and UL97. By 1 year from HCT, 11 of 19 (58%) patients with mutations had CMV end-organ disease. CMV-related mortality in patients with resistance was 42%.

CONCLUSIONS

Nine percent of CMV R+, CD34+ -selected HCT recipients had resistant CMV by 1 year from HCT. Of 19 patients with resistant CMV, 58% had CMV end-organ disease and 42% died of CMV. Effective strategies for CMV prevention and restoration of CMV immunity are needed for CD34+ -selected HCT.