Graft-versus-disease effect following allogeneic transplantation for acute leukaemia

Allogeneic hematopoietic cell transplantation can overcome the adverse prognosis indicated by secondary-type mutations in de novo acute myeloid leukemia

Secondary-type mutations (STMs), namely SRSF2, SF3B1, U2AF1, ZRSR2, ASXL1, EZH2, BCOR, and STAG2, are more frequently detected in secondary acute myeloid leukemia (AML) than in de novo AML. Whether de novo AML with STMs should be differently managed is, however, unclear. In 394 patients diagnosed with de novo AML who had a normal karyotype, the genetic profiling via targeted deep sequencing of 45 genes revealed 59 patients carrying STMs (STM⁺). The STM⁺ group showed shorter overall survival (OS) than the STM^- group (5-year OS, 15.3 vs. 31.0%) (hazard ratio [HR]: 1.975, 95% confidence interval [CI]: 1.446-2.699, p < 0.001). Among the 40 STM⁺ patients who achieved CR, those who received allogeneic HCT (n = 15) showed better OS (5-year OS, 40.0 vs. 12.0%) (HR: 0.423, 95% CI: 0.184-0.975, p = 0.043) and relapse-free survival (5-year, 40.0 vs. 8.0%) (HR: 0.438, 95% CI: 0.189-1.015, p = 0.054) than those who received consolidation chemotherapy only. The cumulative incidence of relapse was lower in the patients who received allogeneic HCT (5-year, 33.3 vs. 60.0%) (HR: 0.288, 95% CI: 0.111-0.746, p = 0.011), and non-relapse mortality was similar between the two groups (p = 0.935). In conclusion, STM is an independent prognostic factor for adverse outcomes in AML that can be overcome by allogeneic HCT.

The impact of the graft-versus-leukemia effect on survival in acute lymphoblastic leukemia

Allogeneic hematopoietic cell transplant is a potential curative therapy for acute lymphoblastic leukemia (ALL). Delineating the graft-versus-leukemia (GVL) effect as a function of graft-versus-host disease (GVHD) offers the potential to improve survival. We examined 5215 transplant recipients with ALL reported to the Center for International Blood and Marrow Transplant Research registry. Overall survival (OS) was compared according to the presence and severity of GVHD and evaluated in 3 cohorts: 2593 adults in first or second complete remission (CR1/CR2), 1619 pediatric patients in CR1/CR2, and 1003 patients with advanced (CR ≥3 or active disease) ALL. For patients in CR1/CR2, development of acute GVHD (aGVHD) or chronic GVHD (cGVHD) was associated with lower risk of relapse than no GVHD (hazard ratio [HR], 0.49-0.69). Patients with advanced ALL developing grades III and IV aGVHD or cGVHD were also at lower risk of relapse (HRs varied from 0.52 to 0.67). Importantly, adult and children in CR1/CR2 with grades I and II aGVHD without cGVHD experienced the best OS compared with no GVHD (reduction of mortality with HR, 0.83-0.76). Increased nonrelapse mortality accompanied grades III and IV aGVHD (HRs varied from 2.69 to 3.91) in all 3 cohorts and abrogated any protection from relapse, resulting in inferior OS. Patients with advanced ALL had better OS (reduction in mortality; HR, 0.69-0.73) when they developed cGVHD with or without grades I and II aGVHD. In conclusion, GVHD was associated with an increased GVL effect in ALL. GVL exerted a net beneficial effect on OS only if associated with low-grade aGVHD in CR1/CR2 or with cGVHD in advanced ALL.

The Graft-Versus-Leukemia Effect in AML

Allogeneic hematopoietic stem cell transplantation (allo-SCT) is the most established and commonly used cellular immunotherapy in cancer care. It is the most potent anti-leukemic therapy in patients with acute myeloid leukemia (AML) and is routinely used with curative intent in patients with intermediate and poor risk disease. Donor T cells, and possibly other immune cells, eliminate residual leukemia cells after prior (radio)chemotherapy. This immune-mediated response is known as graft-versus-leukemia (GvL). Donor alloimmune responses can also be directed against healthy tissues, which is known as graft-versus-host disease (GvHD). GvHD and GvL often co-occur and, therefore, a major barrier to exploiting the full immunotherapeutic benefit of donor immune cells against patient leukemia is the immunosuppression required to treat GvHD. However, curative responses to allo-SCT and GvHD do not always occur together, suggesting that these two immune responses could be de-coupled in some patients. To make further progress in successfully promoting GvL without GvHD, we must transform our limited understanding of the cellular and molecular basis of GvL and GvHD. Specifically, in most patients we do not understand the antigenic basis of immune responses in GvL and GvHD. Identification of antigens important for GvL but not GvHD, and vice versa, could impact on donor selection, allow us to track GvL immune responses and begin to specifically harness and strengthen anti-leukemic immune responses against patient AML cells, whilst minimizing the toxicity of GvHD.

Control of leukemia relapse after allogeneic hematopoietic stem cell transplantation: integrating transplantation with genetically modified T cell therapies

PURPOSE OF REVIEW

Leukemia relapse remains a significant cause of failure after allogeneic hematopoietic stem cell transplantation (HSCT). Although it is widely accepted that immunological components of the stem cell graft play a critical role in promoting leukemia eradication (graft versus leukemia effect), it is also evident that their efficacy is frequently inadequate and leukemia relapse still occurs. This article reviews recent insights into T cell-based posttransplant immunotherapy approaches aimed at preventing or controlling leukemia relapse.

RECENT FINDINGS

Donor lymphocyte infusion with T cells genetically modified with safety switches improves the patient's immune reconstitution while offering appropriate control of graft versus host disease. T lymphocytes engineered with artificial tumor-specific receptors such as αβT-cell receptor chains or chimeric antigen receptors are major players in promoting antileukemia effects after allogeneic HSCT.

SUMMARY

The landscape of adoptive T cell therapies after allogeneic HSCT has seen significant achievements with the introduction of T cell engineering. Gene transfer grants the generation of T cell products characterized by standardizable specificity and functionality. This aspect is critical for scalable and reproducible approaches for application in large clinical studies. The clinical results so far reported are encouraging and multicenter studies conducted by pharmaceutical companies will provide definitive conclusions on the clinical impact of these new methodologies.

Significance of minimal residual disease before myeloablative allogeneic hematopoietic cell transplantation for AML in first and second complete remission

Minimal residual disease (MRD) before myeloablative hematopoietic cell transplantation (HCT) is associated with adverse outcome in acute myeloid leukemia (AML) in first complete remission (CR1). To compare this association with that for patients in second complete remission (CR2) and to examine the quantitative impact of MRD, we studied 253 consecutive patients receiving myeloablative HCT for AML in CR1 (n = 183) or CR2 (n = 70) who had pre-HCT marrow aspirates analyzed by 10-color flow cytometry. Three-year estimates of overall survival were 73% (64%-79%) and 32% (17%-48%) for MRDneg and MRDpos CR1 patients, respectively, and 73% (57%-83%) and 44% (21%-65%) for MRDneg and MRDpos CR2 patients, respectively. Similar estimates of relapse were 21% (14%-28%) and 58% (41%-72%) for MRDneg and MRDpos CR1 patients, respectively, and 19% (9%-31%) and 68% (41%-85%) for MRDneg and MRDpos CR2 patients, respectively. Among the MRDpos patients, there was no statistically significant evidence that increasing levels of MRD were associated with increasing risks of relapse and death. After multivariable adjustment, risks of death and relapse were 2.61 times and 4.90 times higher for MRD(pos) patients (P < .001). Together, our findings indicate that the negative impact of pre-HCT MRD is similar for AML in CR1 and CR2 with even minute levels (≤ 0.1%) as being associated with adverse outcome.

Evidence for a GVL effect following reduced-intensity allo-SCT in ALL: a British Society of Blood and Marrow Transplantation study

Myeloablative allo-SCT decreases relapse incidence (RI) in ALL. Reduced intensity conditioning (RIC) may extend allo-SCT to older and less fit patients. Sixty-nine ALL patients reported to the BSBMT underwent fludarabine-based RIC allo-SCT, 38 from unrelated donors (UD). Forty-four patients received alemtuzumab. ALL was in CR in 64 patients (93%). This was a second or third SCT in 23 patients. Two-year OS and PFS were 36% and 32%, respectively. In multivariate analysis male recipients demonstrated better OS and PFS (hazard ratio (HR) = 0.42, P = 0.008 and HR = 0.45, P = 0.012, respectively). Two-year TRM was 29%: higher with younger age (HR = 0.97/year, P = 0.041), female recipient (HR = 2.55, P = 0.049) and increasing grade of acute GVHD (HR = 1.87, P = 0.001). Two-year RI was 38% and was lower in patients with acute and chronic GVHD (HR = 0.62 per increasing grade, P = 0.035 and HR = 0.52, P = 0.025, respectively). Long-term ALL-free survival is achievable following fludarabine-based RIC allo-SCT. The association between GVHD and decreased RI suggests the presence of a GVL effect.

Allogeneic stem cell transplantation for patients with chronic myeloid leukemia: risk stratified approach with a long-term follow-up

The use of allogeneic stem cell transplantation (SCT) for chronic myeloid leukemia (CML) was almost abandoned in recent years for very effective targeted therapy with tyrosine kinase inhibitors (TKIs). However, approximately one third of patients still need another treatment including SCT. 38 consecutive CML patients were treated (most in preimatinib era) with allogeneic SCT, using partial T cell depletion (TCD) and preemptive donor lymphocyte infusion (DLI), without post-transplant graft-versus-host disease (GvHD) prophylaxis. Conditioning included busulfan, cyclophosphamide, antithymocytic globulin, and fludarabine followed by donor stem cell transfusion. With a median follow up of 90.5 months (1-134), 32 patients are alive. 97% engrafted. 5-year leukemia free survival (LFS) and overall survival (OS) were 78.95% and 84.2%, respectively. All patients are in major molecular remission and 78% in complete molecular remission. Transplant-related mortality (TRM) was 13%. Twenty-four patients received DLI for residual disease. Acute GvHD, mostly Grades I-II, occurred in 18% of patients post-transplant and in 24% of patients receiving DLI. In conclusion, the risk-adapted approach using only partial TCD and preemptive escalated dose of DLI precluded the need for immunosuppressive medications and reduced the risk of significant GvHD without compromising engraftment and long-term disease control. Am. J. Hematol. 2012. © 2012 Wiley Periodicals, Inc.

Predictive impact of allele-matching and EBMT risk score for outcome after T-cell depleted unrelated donor transplantation in poor-risk acute leukemia and myelodysplasia

Many parameters predict for outcome after unrelated donor (URD) allogeneic hematopoietic stem cell transplantation (alloSCT). High-resolution HLA-matching significantly impacts outcome and also the European Group of Blood and Marrow Transplantation (EBMT) risk score, based on patient age, disease stage, donor type, time from diagnosis to SCT and gender combination, may predict for non-relapse mortality and overall survival (OS). We evaluated the individual and combined effects of allele-matching and the EBMT risk score in 327 patients with poor-risk acute leukemia or myelodysplasia, who received a T-cell depleted URD alloSCT. Matching for HLA-A, -B, -C and -DRB1 alleles (8/8 match) was associated with a 5-year OS of 40% compared with 30% for mismatched (≤7/8) pairs (P=0.02). Patients with EBMT risk scores of 1-2, 3, 4 and 5-7 had 5-year OS estimates of 53, 43, 30 and 20%, respectively (P<0.001). The favorable prognostic impact of an 8/8 donor was most pronounced if the EBMT risk score was low (1-2). Five-year OS was 74±8% vs 39±11% for fully matched patients with a low-risk EBMT score as compared with EBMT low-risk patients with ≤7/8 donors. These data underscore the importance of incorporating both the EBMT risk score and the degree of high-resolution HLA-matching in the risk assessment prior to URD alloSCT.

Immunomodulatory effects of vitamin D: implications for GVHD

GVHD remains a major source of morbidity and mortality after allogeneic BMT. GVHD is mediated by alloreactive T cells derived from the hematopoietic graft that target host tissues. Pre-clinical models have shown that presentation of alloantigens by host DCs results in the activation of donor-derived T cells that mediate GVHD. Strategies that interfere with the Ag-presenting capacity of DCs after allogeneic transplantation may decrease the risk of developing GVHD. Vitamin D is a hormone essential for calcium metabolism that shows immunomodulatory properties. We showed that correction of vitamin D deficiency appeared to mitigate manifestations of GVHD. In pre-clinical studies, we have shown that vitamin D inhibits DC maturation, polarizes T-cell populations toward the expression of Th2 as compared with Th1 cytokines, and blunts allogeneic T-cell proliferation in response to DC stimulation. Exposure to vitamin D resulted in increased expression of IDO, an enzyme responsible for tryptophan metabolism that is upregulated in tolerizing DCs. These data suggest that exposure to vitamin D results in immature DC populations that bias toward tolerizing rather than stimulatory T-cell populations. Vitamin D may therefore have a role in the prevention of GVHD.

Transplantation in adult ALL

The value of the allogeneic graft-versus-leukemia effect in adult acute lymphoblastic leukemia (ALL) has now been conclusively demonstrated and confirmed. While this is true for adults in all age groups, it may not be the best clinical option for young adults for whom increasingly intensive pediatric protocols are clearly of benefit. On the other hand, there is potentially wider applicability of allogeneic donor transplantation for adults 25 to 45 years old, for whom matched unrelated donors may be as safe and effective as sibling donors, and for the patient older than 45 years for whom reduced-intensity conditioning may be a promising way forward. Since the treatment-related mortality of allogeneic transplantation remains significant, careful selection of patients is mandatory. Patients with the Philadelphia chromosome, those with t(4;11) and those with a complex karyotype remain transplant candidates, and allogeneic transplantation remains the best option for salvage, where achievable, in a remission beyond first. As in childhood ALL minimal residual disease studies may be extremely useful in predicting outcome and, therefore, strategy, but at present there are less definite data in adults. Clinical indications to harness the allogeneic effect will mature as the true value of pediatric protocols in adult patients and the safety and efficacy of a sibling, unrelated and reduced intensity transplant emerge in this disease.