Long-term Leukemia-free Survival Research Articles

Optimized therapeutic strategy for patients with refractory or relapsed acute myeloid leukemia: long-term clinical outcomes and health-related quality of life assessment.

Patients with refractory or relapsed acute myeloid leukemia (AML) have poor survival, necessitating the exploration of optimized therapeutic strategy. Here, we aimed to investigate clinical outcomes and health-related quality of life (HR-QoL) after total therapy, which included allogeneic hematopoietic stem cell transplantation (allo-HSCT), and prophylactic donor lymphocyte infusion (DLI) in the early phase after transplantation, followed by multiple measurable residual disease (MRD) and graft-versus-host disease (GvHD)-guided DLIs. Consecutive patients who had refractory or relapsed AML and had received non-T-cell-depleted allo-HSCT at Peking University Institute of Hematology were included in the study. If the patients achieved complete remission at 30 days after transplantation and had no evidence of relapse, severe infection, organ failure, and active GvHD at the time of planned DLI, prophylactic DLI was administered at 30 days after transplantation for human leukocyte antigen (HLA)-matched related HSCT or at 45-60 days after transplantation for haploidentical or unrelated HSCT. Subsequently, multiple DLIs were administered based on MRD results and whether they developed GvHD after transplantation. A total of 105 patients were eligible. Eighty-seven patients received prophylactic DLI (group B), while 18 did not receive prophylactic DLI (group A). Among 105 patients, the cumulative incidence of grade 2-4 acute GvHD and chronic GvHD was 40.6% (95% confidence interval [CI] = 30.6%-50.6%) and 73.3% (95% CI = 67.4%-79.2%), respectively. The cumulative incidence of relapse (CIR), transplant-related mortality (TRM), and leukemia-free survival (LFS) at 5 years after transplantation were 31.5% (95% CI = 21.9%-41.1%), 22.1% (95% CI = 11.3%-32.9%), and 46.4% (95% CI = 36.8%-56.0%), respectively. In group B, the CIR, TRM, and LFS at 5 years after transplantation were 27.6% (95% CI = 17.6%-37.6%), 21.6% (95% CI = 11.2%-32.0%), and 50.8% (95% CI = 40.0%-61.6%), respectively. At the end of follow-up, 48 patients survived, and more than 90% of survivors had satisfactory recoveries of HR-QoL. Our study indicated that total therapy is not only associated with decreased CIR, comparable TRM, and better long-term LFS, but also with satisfactory HR-QoL for refractory or relapsed AML, compared with those of standard of care therapy reported previously. Therefore, total therapy may be an optimized therapeutic strategy for refractory or relapsed AML.

CAR-T Therapy Followed By Unrelated Cord Blood Transplantation for the Treatment of Children and Young Adults Relapsed/Refractory B-Cell ALL: Superior Survival but Relatively High Post-Transplant Relapse

Relapsed/refractory (R/R) acute lymphoblastic leukemia (ALL) has poor long-term survival even after chimeric antigen receptor (CAR)-T cell therapy or allogeneic hematopoietic stem cell transplantation (allo-HSCT). Several studies supported that CAR-T therapy followed by allo-HSCT is benefit for improving long-term leukemia free survival (LFS). Since probably a stronger graft versus leukemia (GVL) effect of unrelated cord blood transplantation (UCBT), it is uncertain whether consolidative UCBT is suitable for R/R B-ALL after CAR-T therapy. Here, we conducted a retrospective comparative study for R/R B-ALL patients receiving UCBT in our transplantation center. Totally 43 cases with R/R B-ALL who underwent UCBT were assigned to CAR-T group (patients achieved CR or CRi by CAR-T cell therapy before bridging to UCBT, n = 21) or non-remission (NR) group (n = 22). The median time from CAR-T infusion to UCBT was 62 (range, 42-185) days. All patients achieved neutrophil engraftment by day 42 in CAR-T group. The 180-day cumulative incidence of platelet engraftment was higher in CAR-T group than in NR group (90.5% vs 65.7%, P = 0.16). Incidence of grade II-IV and III-IV acute graft-versus-host disease (GVHD) were 28.6% and 23.8% in CAR-T group, which were both tendency lower than in NR group (45.5% and 31.8%, P = 0.32 and P = 0.63, respectively). No patient suffered from extensive chronic GVHD in CAR-T group, which was lower than in NR group (9.1%, P = 0.23). Lower 2-year cumulative incidence of transplant-related mortality (TRM), and higher probabilities of 2-year overall survival, leukemia free survival (LFS), graft-versus-host disease (GVHD)-free relapse-free survival (GRFS) were found in CAR-T group (4.8% vs 28.2%; 75.0% vs 37.7%; 49.8% vs 23.0%; 42.4% vs 14.8%; P = 0.037, 0.005, 0.028 and 0.017; respectively). However, 2-year cumulative incidence of relapse was comparably high between CAR-T and NR group (26.7% vs 38.3%; P = 0.41). CAR-T therapy followed by UCBT has a superior survival for R/R B-ALL, but remains relatively high post-transplant relapse rate. Prevention of relapse after UCBT is warranted in this patient cohort. DisclosuresNo relevant conflicts of interest to declare.

Will New Drugs Replace Transplants for Chronic Lymphocytic Leukaemia?

Transplants have been used to treat chronic lymphocytic leukemia (CLL) for more than 35 years. Use has been restricted to <1 percent of highly selected persons typically failing concurrent conventional therapies. As therapies of CLL have evolved, so have indications for transplantation and transplant techniques. The data that we review indicate that transplants can result in long-term leukemia-free survival in some persons but are associated with substantial transplant-related morbidity and mortality. We discuss the mechanisms underlying the anti-leukemia effects of transplants including drugs, ionizing radiations, immune-mediated mechanisms and/or a combination. We discuss prognostic and predicative covariates for transplant outcomes. Importantly, we consider whether there is presently a role of transplants in CLL and who, if anyone, is an appropriate candidate in the context of new drugs.

Venetoclax and dexamethasone synergize with inotuzumab ozogamicin–induced DNA damage signaling in B-lineage ALL

AbstractAdult patients with relapsed B-cell precursor acute lymphoblastic leukemia (BCP-ALL) have a dismal prognosis. To improve pharmacotherapy, we analyzed induction of apoptosis by venetoclax and inotuzumab ozogamicin in terms of cytotoxicity and mode of action. Flow cytometry–based analyses of mitochondrial outer membrane permeabilization (MOMP) and ataxia telangiectasia mutated activation demonstrate rapid induction of MOMP by venetoclax and DNA damage signaling by inotuzumab ozogamicin, respectively. In primary ALL samples and patient-derived xenograft (PDX) models, venetoclax and inotuzumab ozogamicin cooperated and synergized in combination with dexamethasone in vitro in all tested samples of ALL. In murine PDX models, inotuzumab ozogamicin, but not venetoclax, induced complete remission in a dose-dependent manner but constantly failed to achieve relapse-free survival. In contrast, combination therapy with venetoclax, dexamethasone, and inotuzumab ozogamicin induced long-term leukemia-free survival and treatment-free survival in all 3 ALL-PDX models tested. These data demonstrate synergistic and highly efficient pharmacotherapy in preclinical models that qualify for evaluation in clinical trials.

Abstract 531: AT1412, a patient-derived antibody in development for the treatment of CD9-positive precursor B-acute lymphoblastic leukemia

Abstract Introduction Despite rapid advances in immunotherapeutic options for precursor B-acute lymphoblastic leukemia (BCP-ALL), outcomes remain poor especially for adult ALL and relapsed pediatric ALL. With conventional chemotherapy remission percentages in adult ALL range from 75 to 90%, but relapse rates are high and long-term leukemia-free survival ranges between 35-70% depending on age and risk group. The introduction of CD19-targeting immunotherapy has significantly improved patient outcomes in (relapsed) BCP-ALL. However, tumor escape via downregulation of CD19 occurs in a significant number of patients. An ongoing medical need remains for the identification of alternative immunotherapeutic targets for treatment of ALL. Methods CD9 is expressed in 60-80% of BCP-ALL, is correlated with adverse prognosis and has been proposed as therapeutic target for BCP-ALL. AT1412 is a fully human CD9-targeting antibody, that was identified from a patient cured of metastatic melanoma after adoptive T-cell therapy, using our B-cell immortalization technology (AIMSelect) [Kwakkenbos et al. Nat. Med. 2010]. The antibody was selected based on differential binding to melanoma cells as compared to healthy melanocytes and was shown to be successful in killing melanoma cells in vitro and in vivo. Results Binding of AT1412 to BCP-ALL cell lines SUP-B15, MHH-CALL-2 and CCRF-SB varied as expected based on CD9 levels that we detected using a commercial CD9 antibody. AT1412-induced antibody dependent cellular cytotoxicity (ADCC) and antibody dependent cellular phagocytosis (ADCP) correlated with the level of AT1412 binding. No binding was seen to the T-ALL cell line Jurkat. These findings were confirmed in primary ALL samples, obtained prospectively at diagnosis from a cohort of patients with T- or B-ALL (n=38). AT1412 showed binding to the majority of B-ALL samples but not to T-ALL samples. AT1412 induced ADCC of nearly all B-ALL samples it bound to (10/11) and of none of the non-binding B-ALL or T-ALL samples. Cytotoxicity significantly correlated with the level of AT1412 binding. These findings were corroborated by the observation that AT1412 induced specific B-ALL cell death when a bone marrow sample from a newly diagnosed BCP-ALL patient was incubated with AT1412. Remarkably, AT1412 induced cell death in the absence of added effector cells or other (chemo)therapeutic agents, while the sample contained over 80% blasts and as little as 3% lymphocytes. We are currently investigating the in vivo efficacy of the antibody in a humanized immune system mouse model with human BCP-ALL. Conclusion Taken together, the majority of BCP-ALL express CD9 and this is associated with poor prognosis. Our data demonstrate that CD9 can be successfully targeted by the human CD9 antibody AT1412, suggesting that AT1412 has the potential to be developed as a therapeutic antibody for B-ALL. AT1412 is currently being advanced through preclinical development. Citation Format: Greta de Jong, Sophie E. Levie, Remko Schotte, Wouter Pos, Daniel Go, Etsuko Yasuda, Madalina Cercel, Susan E. van Hal, Esmay Frankin, Aniko Szabo, Martijn Kedde, Els Verdegaal, Julien Villaudy, Sjoerd van der Burg, Pauline M. van Helden, Hans van Eenennaam, Hergen Spits, Anita van Rijneveld, Mette D. Hazenberg. AT1412, a patient-derived antibody in development for the treatment of CD9-positive precursor B-acute lymphoblastic leukemia [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 531.

High Risk of Relapse with Intermediate Dose Cytarabine for Consolidation in Young Favorable Risk AML Patients Following Induction with 7+3

Introduction CALGB study in 1994 reported improved leukemia free survival (LFS) with sequential courses of high dose cytarabine (HIDAC- 3 gm/m2, q12h on days 1, 3 and 5) compared to lower doses of 100 mg/m2 and 400 mg/m2 per day. Following this study, HIDAC has been commonly used for chemotherapy consolidation in AML patients 60 years or younger. More recently, several groups investigated the role of intermediate dose cytarabine (IDAC-1.5 gm/m2 q12h D 1, 3 and 5 or D 1-3) in this population and reported equivalent outcomes for IDAC compared to HIDAC (Table 1). ELN guidelines published in January 2017 recommend IDAC for consolidation therapy in young (&amp;lt;60 years) favorable risk AML patients. Following these studies and ELN publication, consolidation protocols for AML patients 60 years or younger were changed from HIDAC to IDAC at Singapore General Hospital (SGH) in 2011 and at University of Minnesota Medical Center (UMMC) in February 2017. NCCN continues to recommend HIDAC as category 1 recommendation for consolidation of patients in this setting. We performed a combined analysis of outcomes in young favorable risk AML patients to assess impact of this change in practice on outcomes at our institutions as a quality initiative. Methods Patients 60 years or younger with ELN favorable risk AML between 2004 and 2015 at SGH and between September 2015 and March 2018 at UMMC, who underwent induction therapy with 7+3 regimen (idarubicin 12 mg/m2 D1-3 or daunorubicin 60 - 90 mg/m2 and cytarabine 100 mg/m2 continuous infusion from D1-7) and consolidation with cytarabine monotherapy were identified. These dates were chosen to allow reasonably equal time distribution before and after change in our practice. We extracted relevant outcomes data using chart review. We used Chi-square testing and applied Kaplan-Meier survival analysis to detect differences in relapse and survival outcomes. Results Of 67 ELN favorable risk patients 60 years or younger, 42 received HIDAC and 25 received IDAC. Median age was 39 years (range 16-59). 64 patients received 1 induction cycle and 3 patients received 2 induction cycles to achieve complete remission. Median LFS and overall survival (OS) with HIDAC vs IDAC were not-reached (NR, median time for follow up = 6.9 years) vs 1.35 years (p=0.004) and NR vs 2.27 years (p=0.001) respectively (Figure 1). Cumulative incidence of relapse at 2 years was 23.8% for HIDAC and 60% for IDAC groups (p=0.003). 3-year LFS and OS for HIDAC vs IDAC groups were 71% vs 36% (p=0.06) and 90% vs 48% (p=0.002). Discussion Historical data suggests chemotherapy consolidation with 3-4 cycles of HIDAC achieves long-term LFS of 60 - 70 % in young favorable risk AML patients. While the outcomes in HIDAC group in this study are comparable to historical data with good outcomes, a significantly larger proportion of patients in the IDAC group had early relapse (60%) and death. A major difference between the patients in this study and the other studies which showed similar outcomes with HIDAC and IDAC is the mode of induction. Data from large randomized studies in AML (Table 1) that suggest similar efficacy of IDAC compared to HIDAC used higher intensity induction regimens (frequently double induction therapy) compared to 7+3 and/or used other agents in combination with Ara-C for consolidation. These data are not broadly applicable in patients who receive a single cycle of 7+3 for induction, when selecting dose of Ara-C as monotherapy for consolidation. Furthermore, studies that used 7+3 for induction therapy showed benefit for HIDAC compared with multi-agent chemotherapy that included IDAC (Table 1). Conclusion Using single agent IDAC for post remission therapy is associated with higher rates of relapse and poor overall survival compared to HIDAC among young, ELN favorable risk AML patients who achieve complete remission following 7+3. The large randomized studies that suggested equivalency of IDAC to HIDAC for post remission therapy in AML patients, either used more than one cycle of intensive induction regimen and/or used cytarabine in combination with an anthracycline for consolidation. Hence, ELN guidelines should be cautiously interpreted given the above limitations in generalizability. Our study suggests that HIDAC, rather than IDAC, is the preferred chemotherapy consolidation regimen in young, favorable risk AML patients following standard 7+3 induction. Foot note: BK &amp; NAAH contributed equally. FH &amp; ZL contributed equally. Disclosures Kolla: Amgen: Equity Ownership. Weisdorf:Pharmacyclics: Consultancy; Incyte: Research Funding; Fate Therapeutics: Consultancy.

AT1412, a Patient-Derived Antibody in Development for the Treatment of CD9 Positive Precursor B-Acute Lymphoblastic Leukemia

Despite rapid advances in immunotherapeutic options for precursor B-acute lymphoblastic leukemia (ALL), outcomes remain poor especially for adult ALL and relapsed pediatric ALL. With conventional chemotherapy, remission percentages in adult ALL range from 75 to 90%, but relapse rates are high and long-term leukemia-free survival ranges between 35-70% depending on age and risk group. The introduction of CD19 targeting immunotherapy has significantly improved patient outcomes in (relapsed) B-ALL. However, tumor escape via downregulation of CD19 occurs in a significant number of patients. Therefore an ongoing urgency remains for the identification of additional or alternative immunotherapeutic targets for the treatment of ALL. AT1412 is an antibody that was identified from the peripheral blood memory B cell pool of a patient cured of metastatic melanoma after adoptive T-cell therapy, using a B cell immortalization technology (AIMSelect) with ectopic Bcl-6 and Bcl-xL expression as described previously [Kwakkenbos et al. Nat. Med. 2010]. The antibody was selected based on differential binding to melanoma cells as compared to healthy melanocytes and was shown to be successful in killing melanoma cells in vitro and in vivo [manuscript submitted]. In addition to melanoma, AT1412 binds other tumor types including B-ALL, gastric, colon- and pancreatic cancer. The target of AT1412 is the tetraspanin CD9, which is expressed by more than half of all B-ALL. Expression of CD9 has been correlated with adverse prognosis [Liang et al. Cancer Biomark. 2018]. We assessed binding of this human CD9 antibody to a panel of ALL cell lines using flow cytometry. Binding of AT1412 to the B-ALL cell lines SUP-B15, MHH-CALL-2 and CCRF-SB varied as expected based on the CD9 levels that we detected using a commercial CD9 antibody. AT1412 induced antibody dependent cellular cytotoxicity (ADCC) on these cells, in line with the level of AT1412 binding. No binding was seen to the T-ALL cell line Jurkat. Importantly, these findings were confirmed in primary ALL samples, obtained prospectively at diagnosis from a cohort of patients with T- or B-ALL (n=30). AT1412 showed binding to 61% of B-ALL samples but not to T-ALL samples. The potential of AT1412 to induce ADCC was tested on patient samples from the same panel. Remarkably, AT1412 induced ADCC of all B-ALL samples it bound to (8 out of 14) and of none of the T-ALL samples. Cytotoxicity significantly correlated with the level of AT1412 binding. These findings were supported by the observation that AT1412 induced B-ALL cell death when a freshly drawn whole bone marrow sample from a patient with newly diagnosed B-ALL was cocultured with AT1412. AT1412-induced cell death of B-ALL blasts occurred without affecting the monocytic, granulocytic and lymphocytic populations. This cell death was not observed when this patient's ALL blasts were incubated with AML-targeting antibodies. Remarkably, AT1412 induced cell death in the absence of added effector cells or other (chemo)therapeutic agents, while the bone marrow sample contained over 80% blasts and as little as 3% lymphocytes. We are currently investigating the in vivo efficacy of the antibody in a humanized immune system mouse model with human B-ALL. Taken together, the majority of precursor B-ALL blasts express CD9 and expression of CD9 is associated with a dismal outcome. Our data demonstrate that CD9 can be successfully targeted by the human CD9 antibody AT1412, suggesting that AT1412 has the potential to be developed as a therapeutic antibody for B-ALL. AT1412 is currently being advanced through preclinical development. Disclosures De Jong: AIMM Therapeutics: Employment. Levie:AIMM Therapeutics: Employment. Schotte:AIMM Therapeutics: Employment, Equity Ownership, Patents &amp; Royalties: Patent WO2017119811A1. Pos:AIMM Therapeutics: Patents &amp; Royalties: Patent WO2017119811A1. Go:AIMM Therapeutics: Employment, Patents &amp; Royalties: Patent WO2017119811A1. Yasuda:AIMM Therapeutics: Employment, Equity Ownership. Cercel:AIMM Therapeutics: Employment. van Hal-van Veen:AIMM Therapeutics: Employment. Frankin:AIMM Therapeutics: Employment. Villaudy:AIMM Therapeutics: Employment, Equity Ownership, Patents &amp; Royalties: Patent WO2017119811A1. van Helden:AIMM Therapeutics: Employment, Equity Ownership, Patents &amp; Royalties: Patent WO2017119811A1. van Eenennaam:AIMM Therapeutics: Employment. Spits:AIMM Therapeutics: Employment, Equity Ownership, Patents &amp; Royalties: Patent WO2017119811A1. Hazenberg:AIMM Therapeutics: Other: Employment/equity of partner/spouse.

Anti-CD19 chimeric antigen receptor-modified T-cell therapy bridging to allogeneic hematopoietic stem cell transplantation for relapsed/refractory B-cell acute lymphoblastic leukemia: An open-label pragmatic clinical trial.

Chimeric antigen receptor-modified T-cell (CAR-T) therapy is effective and safe for patients with relapsed/refractory B-cell acute lymphoblastic leukemia (r/r B-ALL), but its value has been limited in terms of long-term leukemia-free survival. New strategies that can help CAR-T therapy achieve lasting effect are urgently warranted. This non-randomized interventional pragmatic clinical trial had a particular aim. It explored whether consolidative allogeneic hematopoietic stem cell transplantation (allo-HSCT) could improve the long-term prognosis of the minimal residual disease-negative complete remission (MRD- CR) patients after CAR-T therapy. In the first stage, 58 r/r B-ALL patients received split doses of CAR-T cells after lymphodepleting chemotherapy, and 51 (87.9%) achieved CR. In the second stage, 21/47 MRD- CR patients without previous allo-HSCT and contraindications or other restrictions, on their own accord, received consolidative allo-HSCT within three months after CAR-T therapy. There was no difference in overall survival (OS) between the MRD- CR patients who received allo-HSCT and those who did not. However, event-free survival (EFS) and relapse-free survival (RFS) were significantly prolonged by allo-HSCT in the subgroups. This was with either high (≥5%) pre-infusion bone marrow MRD assessed by flow cytometry (BM-FCM-MRD) or poor prognostic markers (P < .05). However, no difference was found in EFS and RFS for patients with pre-infusion BM-FCM-MRD <5% and without poor prognostic markers (P > .05). To conclude, CAR-T therapy bridging to allo-HSCT is a safe and effective therapeutic strategy for r/r B-ALL patients, and may prolong their EFS and RFS, especially when they have high pre-infusion BM-FCM-MRD or poor prognostic markers.

Donor Plasmacytoid Dendritic Cells Home to the Thymus of the Transplant Recipient and Limit Graft Versus Host Diseases through Production of Vasoactive Intestinal Polypeptide

Introduction: In allogeneic hematopoietic stem cell transplant (AHSCT), donor T cells promote hematopoietic engraftment, reconstitute T-cell immunity and mediate potent beneficial antitumor effects, such as graft versus leukemia (GVL) as well as detrimental graft-versus-host disease (GVHD). We have shown that purified bone marrow pDC to a donor graft composed of purified HSC and T cells significantly improved long-term leukemia-free survival without increasing the risk of GVHD (Lu BLOOD 2012). Vasoactive intestinal peptide (VIP) is a neuropeptide/neurotransmitter, which acts as a major anti-inflammatory factor in animal models of inflammatory and autoimmune diseases. VIP is produced by T cells and dendritic cells under conditions of inflammation (Li Cancer Research 2016). VIP-signaling, thus represents a newly appreciated co-inhibitory pathway involved in T cell activation and expansion and persistence of antigen-specific T cells, but the role of VIP produced by donor dendritic cells in allo-BMT is unclear. Our previous data has shown that production of VIP in pDC improves survival in a murine allo-BMT model. Since the thymus plays a critical role in regenerating naive T cells in which allo-reactive donor T cells undergoes central deletion. We hypothesized that donor pDCs that home to thymus modulate the negative selection of allo-reactive T cells and iTreg production through VIP signaling.Methods and Results: Our previous data has shown that the mice receiving HSC, T cells and WT pDC had a significantly higher survival (71%) compared to those receiving VIP-KO pDC (31%). On day 15 after transplant, recipients of WT pDC, VIP-KO pDC and no pDC developed ~98% chimerism, without significant differences among the three groups. Local production of VIP in pDC inhibited activation and Th1 immune polarization of donor T cells.Recipient spleens were harvested on day 15 after transplant for analysis of cytokine production by donor T cells. The percentage of CD8+ donor T cells producing IL17 was significantly higher in recipients of VIP-KO pDC compared to recipients of WT-pDC (Fig 2.A-B). The ratio of foxp3+ CD4+ donor T-reg to IL17+ CD4+ T cells from recipients of WT pDC was almost 3 times higher than the recipients of VIP-KO pDC (Fig 2.C-D).To visualize production of VIP by donor pDC, B10.BR mice were transplanted with 5,000 stem cells, 1M T cells and 50,000 pDCs from VIP-GFP (VIP promoter and GFP reporter) or GFP mice. On day 7 post-transplant, the thymus was examined with confocal microscopy with GFP (green), anti-PDCA-1-Alexa Fluor 568 (red) and DAPI (blue). A superimposed profile of the thymus showed that donor GFP pDCs homed to thymus (Fig.2-A), and that donor pDC in the recipient thymus produced VIP (Fig.2-B).Conclusion: Expression of VIP in donor pDCs inhibited activation and Th17 immune polarization of donor CD8+ T cells after allo-BMT. Foxp3+ expression tended to be higher among CD4+ donor T cells from recipients of WT pDCs compared with recipients of VIP-KO pDCs. Thus, VIP-producing donor pDC in thymus could be very critical to contribute to negative selection of allo-reactive donor T cell or facilitate the generation of Foxp3+ nTreg. This data supported a new mechanism by which GvHD maybe regulated and central tolerance maintained. Ongoing experiments aim at defining the role of VIP production in the thymus by donor pDC in positive and negative T cell selection. [Display omitted] DisclosuresWaller:Celldex: Research Funding; Novartis Pharmaceuticals Corporation: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Cambium Medical Technologies: Consultancy, Equity Ownership; Kalytera: Consultancy; Pharmacyclics: Other: Travel Expenses, EHA, Research Funding.

Photochemotherapy and Graft-versus-Leukemia Reaction in Acute Leukemia: Tumor Immunity and Survival Are Dependent on Timing of Photochemotherapy of the Skin

Background: Cure of acute leukemia after transplantation is mediated by the grafted cells. We investigated the graft-versus-leukemia effect (GVL) in patients with cutaneous acute graft-versus-host disease (GVHD) treated with photochemotherapy (psoralen and ultraviolet light type A). Method: Forty-seven patients with acute leukemia were followed 5,000 days after transplantation to assess survival and GVL by multivariate analysis. The primary predictor was time to treatment of cutaneous acute GVHD by photochemotherapy separated into treatment start during the first week of acute GVHD versus after the first week of acute GVHD. Results: Photochemotherapy started after the first week of acute GVHD predicted GVL with a hazard ratio (HR) of 3.94 (95% confidence interval, CI, 1.67-9.33, p = 0.0018) and survival with preserved GVL with an HR of 2.63 (95% CI 1.30-5.32, p = 0.007). The effects on GVL and survival with preserved GVL were present regardless of whether the patients were transplanted in remission or relapse (p < 0.05). Chronic GVHD came earlier in the group that started photochemotherapy after 1 week of acute GHVD, but chronic GVHD did not increase the GVL. Conclusion: The timing of photochemotherapy after cutaneous acute GVHD may direct the GVL and predict long-term leukemia-free survival.

Reduced Intensity Hematopoietic Cell Transplantation in Active Disease AML Is Associated with Leukemia Free Survival and Relapse Comparable to Myeloablative Conditioning

Introduction: Up to 40% of new acute myeloid leukemia (AML) patients fail to achieve complete remission (CR), and a significant number of patients achieving remission eventually relapse. Allogeneic hematopoietic cell transplantation (allo-HCT) remains the best curative option for these patients with a long-term leukemia free survival (LFS) of around 20-30% with the use of intensive myeloablative condition (MAC) transplants. Active disease AML patients otherwise deemed unfit for MAC regimens have limited treatment options. Although reduced intensity condition (RIC) has broadened transplant eligibility in the elderly AML patients particularly in CR, there is a paucity of data on the use RIC allo-HCT in AML patients with active disease. To answer this question, we retrospectively analyzed data from active disease AML patients who underwent RIC allo-HCT and compared their outcomes with contemporaneous patients who underwent MAC allo-HCT at our institution.Patients and methods: Our cohort included all patients with active disease AML (primary induction failure, relapsed refractory or cytogenetic persistence) at the time of transplantation, who underwent allo-HCT at Washington University Medical Center in St. Louis between January 2006 and June 2015. Patients were classified according to the intensity of conditioning regimens: MAC versus RIC. The primary study endpoints were leukemia free survival (LFS) and overall survival (OS). LFS was defined as the time from the achievement of CR after allo-HCT to the time of relapse, death in remission, or last follow-up. OS was defined as the time from transplantation to the time of death from any cause or last follow-up. The between-group differences in LFS and OS were described using Kaplan-Meier (KM) survival curves and compared by log-rank test. Univariate Cox regression analysis for LFS was performed. All analyses were two-sided, and significance was set at a p-value of 0.05, using SAS 9.4 (SAS Institutes, Cary, NC).Results: 138 patients were included. 30 patients (21.7%) underwent RIC allo-HCT and 108 (78.3%) underwent MAC allo-HCT. Their baseline characteristics are listed in Table 1. 21 patients (72.4%) in RIC and 77 (81.9%) in MAC achieved CR on day-28 bone marrow biopsy. Notably, there were 16 patients (1 RIC and 15 MAC) who died prematurely without post-transplant evaluation; subsequently they were excluded from LFS, relapse and NRM calculations. There was no difference in the LFS in these two groups; 1-year and 3-year LFS were 40.6% (95% CI 23-70) and 33.1% (95% CI 17-66) in the RIC patients while 40.7% (95% CI 31-54) and 33.2% (95% CI 23-47) in the MAC patients, respectively (p=0.99) (Figure 1A). Similarly the CI of relapse at 1 year and 3 year was not different in the two groups; 45.8% (95% CI 30-71) and 50.5% (95% CI 33-76) in RIC group vs. 51.9% (95% CI 43-63) and 56.8% (95% CI 48-67) in MAC group, respectively (p=0.61) (Figure 1B).The CI of NRM at 1-year and 3-year was 28.1% (95% CI 16-50) and 32.6% (95% CI 19-56) in RIC group compared to 17.9% (95% CI 11-28) and 21.0% (95% CI 14-31) in the MAC group (p = 0.21). However, OS in both groups remained poor with 1-year and 3-year OS of 25.1% (95% CI 14-44) and 13.2% (95% CI 6-31) in RIC vs. 35.5% (95% CI 28-46) and 22.0% (95% CI 15-32) in MAC, respectively (p = 0.21). On univariate analysis for LFS and relapse, only cGvHD was associated with higher LFS (p<0.01, HR 0.27, 95% HR 0.13-0.52) and lower relapse risk (p= 0.01, HR 0.37, 95% HR 0.15-0.89) in these patients. On multivariate analysis for LFS, only cGvHD was statistically significant (p<0.01, HR 0.32, 95% HR 0.18-0.56). On the other hand, intermediate cytogenetic risk (p=0.01, HR 1.59, 95% HR 1.08-2.34) and cGvHD (p<0.01, HR 0.12, 95% HR 0.05-0.27) were significant for OS.Conclusion: The use of RIC allo-HCT in active disease AML is associated with LFS and relapse comparable to MAC allo-HCT. However, high relapse rates and NRM, in both groups translated into poor long term OS. Careful selection of patients and early utilization of transplant without subjecting these patients to multiple salvage regimens might help lower NRM rates in future studies. Notably, our study might open a window for future prospective studies aimed at finding improved ways to harness the graft versus leukemia (GvL) effect associated with RIC transplantation in patients who are otherwise not able to tolerate more toxic intensive conditioning regimens. [Display omitted] [Display omitted] [Display omitted] DisclosuresDiPersio:Incyte Corporation: Research Funding. Vij:Karyopharm: Honoraria; Janssen: Honoraria; Bristol-Myers Squibb: Honoraria; Novartis: Honoraria; Amgen: Honoraria, Research Funding; Celgene: Consultancy; Takeda: Honoraria, Research Funding.

Autologous Hematopoietic Stem Cell Transplantation for High-risk Acute Lymphoblastic Leukemia: non-Randomized Study with a maximum Follow-up of more than 22 Years.

ObjectiveTo evaluate the efficacy and toxicity of autologous hematopoietic stem cell transplantation (AHSCT) for high-risk acute lymphoblastic leukemia (ALL).Material and methodsOverall, 128 high-risk ALL patients at a median age of 26 years (range 18–56 years) at diagnosis received AHSCT between 1991–2008. Induction treatment was anthracycline-based in all patients. Conditioning regimen consisted of CAV (cyclophosphamide, cytarabine, etoposide) in 125 patients whereas 3 subjects received cyclophosphamide and TBI (total body irradiation). Bone marrow was stored for 72 hours in 4°C and re-infused 24 hours after conditioning completion. Bone marrow was a source of stem cells in 119 patients, peripheral blood in 2 and 7 subjects received both bone marrow and peripheral blood.ResultsWith a median follow-up after AHSCT of 1.6 years (range 0.1–22.3 years), the probability of leukemia-free survival (LFS) for the whole group at 10 years was 27% and 23% at 20 years. Transplant-related mortality at 100 days after AHSCT was 3.2%. There was a strong tendency for better LFS for MRD-negative patients if compared with patients who had positive or unknown MRD status at AHSCT (32% vs 23% and 25%, respectively; p=0.06). There was no difference in LFS between B- and T-lineage ALL as well as between patients transplanted in first complete remission (CR1) and CR2. LFS at 10 years for patients with Philadelphia-positive (Ph+) ALL at transplant was 20% and this was comparable with subjects with negative and missing Ph status (26% and 28%; p=0.97).ConclusionsThe results of AHSCT for high-risk ALL remains unsatisfactory with low probability of long-term LFS.

Pediatric posttransplant relapsed/refractory B-precursor acute lymphoblastic leukemia shows durable remission by therapy with the T-cell engaging bispecific antibody blinatumomab.

We report on posttransplant relapsed pediatric patients with B-precursor acute lymphoblastic leukemia with no further standard of care therapy who were treated with the T-cell engaging CD19/CD3-bispecific single-chain antibody construct blinatumomab on a compassionate use basis. Blast load was assessed prior to, during and after blinatumomab cycle using flow cytometry to detect minimal residual disease, quantitative polymerase chain reaction for rearrangements of the immunoglobulin or T-cell receptor genes, and bcr/abl mutation detection in one patient with Philadelphia chromosome-positive acute lymphoblastic leukemia. Blinatumomab was administered as a 4-week continuous intravenous infusion at a dosage of 5 or 15 μg/m(2)/day. Nine patients received a total of 18 cycles. Four patients achieved complete remission after the first cycle of treatment; 2 patients showed a complete remission from the second cycle after previous reduction of blast load by chemotherapy. Three patients did not respond, of whom one patient proceeded to a second cycle without additional chemotherapy and again did not respond. Four patients were successfully retransplanted in molecular remission from haploidentical donors. After a median follow up of 398 days, the probability of hematologic event-free survival is 30%. Major toxicities were grade 3 seizures in one patient and grade 3 cytokine release syndrome in 2 patients. Blinatumomab can induce molecular remission in pediatric patients with posttransplant relapsed B-precursor acute lymphoblastic leukemia and facilitate subsequent allogeneic hematopoietic stem cell transplantation from haploidentical donor with subsequent long-term leukemia-free survival.

Discontinuation of tyrosine kinase inhibitors and new approaches to target leukemic stem cells: Treatment-free remission as a new goal in chronic myeloid leukemia

Only a small fraction of chronic phase chronic myeloid leukemia patients (CP-CML) achieves a very deep reduction of residual disease with imatinib. Second-generation tyrosine kinase inhibitors administered as front-line therapy for CP-CML have improved the rates and degree of deeper molecular responses. Owing to this improvement, new standardized definition of complete molecular remission has been provided, which allowed plan of prospective strategies to definitively discontinue therapy in the long-term. In this review, we report the results of several published discontinuation studies and critically discuss the new approaches and tools to monitor residual disease during treatment and new strategies to target leukemic stem cells to reach a potential “operational” cure and persistent long-term leukemia-free survival.

Alternative approaches to eradicating the malignant clone in chronic myeloid leukemia: tyrosine-kinase inhibitor combinations and beyond

In patients with chronic myeloid leukemia (CML) in chronic phase who have achieved complete molecular remission on imatinib therapy, clinical trials from France and Australia have demonstrated that the majority experience prompt molecular relapse of their leukemia upon discontinuation of the drug, showing that long-term monotherapy with tyrosine kinase inhibitors is not curative in the majority of patients with CML. This has focused attention on strategies to eradicate residual disease in CML that is presumed to arise from malignant Ph+ stem cells, which should result in permanent cure and long-term leukemia-free survival. Here, we review the evidence that targeting CML stem cells will be of clinical benefit and discuss pharmacological and immunological approaches to accomplish this goal. Where possible, we link preclinical studies of CML stem cell biology to emerging results from clinical trials of agents that may target these cells.

Unrelated Donor Allogeneic Transplantation after Failure of Autologous Transplantation for Acute Myelogenous Leukemia: A Study from the Center for International Blood and Marrow Transplantation Research

The survival of patients with relapsed acute myelogenous leukemia (AML) after autologous hematopoietic stem cell transplantation (auto-HCT) is very poor. We studied the outcomes of 302 patients who underwent secondary allogeneic hematopoietic cell transplantation (allo-HCT) from an unrelated donor (URD) using either myeloablative (n = 242) or reduced-intensity conditioning (RIC; n = 60) regimens reported to the Center for International Blood and Marrow Transplantation Research. After a median follow-up of 58 months (range, 2 to 160 months), the probability of treatment-related mortality was 44% (95% confidence interval [CI], 38%-50%) at 1-year. The 5-year incidence of relapse was 32% (95% CI, 27%-38%), and that of overall survival was 22% (95% CI, 18%-27%). Multivariate analysis revealed a significantly better overal survival with RIC regimens (hazard ratio [HR], 0.51; 95% CI, 0.35-0.75; P <.001), with Karnofsky Performance Status score ≥90% (HR, 0.62; 95% CI, 0.47-0.82: P = .001) and in cytomegalovirus-negative recipients (HR, 0.64; 95% CI, 0.44-0.94; P = .022). A longer interval (>18 months) from auto-HCT to URD allo-HCT was associated with significantly lower riak of relapse (HR, 0.19; 95% CI, 0.09-0.38; P <.001) and improved leukemia-free survival (HR, 0.53; 95% CI, 0.34-0.84; P = .006). URD allo-HCT after auto-HCT relapse resulted in 20% long-term leukemia-free survival, with the best results seen in patients with a longer interval to secondary URD transplantation, with a Karnofsky Performance Status score ≥90%, in complete remission, and using an RIC regimen. Further efforts to reduce treatment-related mortaility and relapse are still needed.

Acute Myeloid Leukemia as a Model for Cancer Therapy

Acute Myeloid Leukemia as a Model for Cancer Therapy

Is Standard Treatment (DA 3+7) Is Still Recommended As Front Line Therapy for Adult Patients with De Novo AML? the Role of Etoposide

Abstract 4272 Background:Early intensification of chemotherapy in the remission induction phase of patients with acute myeloid leukemia (AML) has been shown to improve the remission rate and long-term leukemia-free survival. Aim:This trail is designed to assess the role of etoposide in the induction remission schedules in younger patients with de novo AML. Methods:Newly diagnosed previously untreated younger patients (15–60 years) with AML were randomly assigned to 3 groups; group A received conventional treatment DA 3+7 [daunorubicin 60 mg/m2/day (days 1–3) and cytosine arabinoside (Ara-C) 200 mg/m2/day by continuous iv infusion (days 1–7)], group B received conventional treatment [ Ara-C 100 mg/m2/day by continuous iv infusion (days 1–10) + daunorubicin 50mg/m2/day (days 1,3,5)] + etoposide (50 mg/m2/day; days 1–5), and group C received high dose AraC (HD-AraC) 3g/m2/12 hrs. (days 1, 3, 5 and 7) + daunorubicin and etoposide in the same dose as above (as in group B). All patients were treated in the Department of Hematology, University Hospital, Bratislava. Informed consents were obtained. RT-PCR was done to determine the expression of topoizomerase I, II-alpha and II-beta genes in bone marrow samples at diagnosis. The data were analyzed using SPSS statistical software versions 16.0, 2008. Results:Between September 2000 and August 2011, 128 patients were recruited (group A = 27, group B = 57, and group C = 44). There was no statistically significant difference in age, sex, performance state, AML subtype (M4-5), WBC count and cytogenetic risk distribution in the 3 groups. Patients have been followed for a median of 92 months. After 1 course of induction the complete remission (CR) rate was 55.6%, 75.4% and 81.8% in group A, B and C respectively (P = 0.048). Group A vs. B (P = 0.025), group A vs. C (P = 0.027), group B vs. C (P = 0.81). Induction toxicity profile and grade was similar in all groups except for conjunctivitis grade 2 and 3 which was higher in group C. The 5 year's overall survival (OS) was 17%, 41% and 33% (P = 0.36) and disease free survival (DFS) was 25%, 44% and 35% (P = 0.21) in group A, B and C respectively. There was statistically significant improvement in OS but not DFS in patient receiving etoposide (P < 0.00001). Overexpression of topoisomerase I and II genes were detected in 12/19 (63%) and 14/19 (74%) patients at diagnosis; respectively. Topoisomerase II-alpha and II-beta genes were increased by a median of 4.1 (range 1.7–27.3) and 2.9 (range 2.4–5.1) than normal; respectively. Conclusion:the addition of etoposide to standard treatment of AML can improve the rate of complete remission and outcome in adult de novo AML patients. The incorporation of etoposide to HD-AraC regimens during induction may further improve the rate of CR without effect on outcome (DFS and OS). Measurement of topoisomerase II gene expression at diagnosis can help in selecting patients who will benefit from the addition of etoposide. Disclosures:No relevant conflicts of interest to declare.

Outcome of Myeloablative Conditioning and Unrelated Donor Hematopoietic Cell Transplantation for Childhood Acute Lymphoblastic Leukemia in Third Remission

We conducted a retrospective study of 155 children who underwent unrelated donor hematopoietic cell transplantation (HCT) between 1990 and 2005 for acute lymphoblastic leukemia in third remission. The median patient age was 11 years, the median time from diagnosis to first relapse was 36 months, and the median time from first relapse to second relapse was 26 months. Stem cell sources were bone marrow (n= 115), peripheral blood (n = 11), and cord blood (n = 29). All patients received a myeloablative pretransplantation conditioning regimen. The 5-year estimates of leukemia-free survival, relapse, and nonrelapse mortality were 30%, 25%, and 45%, respectively. In multivariate analysis, the only risk factor associated with relapse was the interval between the first relapse and the second relapse. Second relapses occurring >26 months from the first relapse were associated with lower risk for post-HCT relapse compared with second relapses occurring at ≤26 months (relative risk, 0.4; P = .01). Relapse risk was lowest when late second relapse was preceded by late first relapse (>36 months from diagnosis), as demonstrated by a 3-year relapse rate of 9% (P = .0009). Our data indicate that long-term leukemia-free survival can be achieved in children with acute lymphoblastic leukemia in third remission using unrelated donor HCT, especially when the second relapse occurs late.

Killer Cell Immunoglobulin-Like Receptor (KIR) Ligands Predict Outcomes of Autologous Stem Cell Transplantation for AML

AbstractAbstract 3571The idea of natural killer (NK) cell alloreactivity after allogeneic stem cell transplantation (SCT) was developed from reports of patients with acute myelogenous leukemia (AML). However, little definite information exists about the killer cell immunoglobulin-like receptor (KIR) and its ligand activity in autologous SCT. Since whether autologous NK cells are involved in the eradication of leukemia cells is still unclear, we focused on whether autologous NK or CD8+ T cells are stimulated after myeloablative conditioning, according to the ligand match. In light of a previous report that KIR–HLA combinations have effects in lymphoma and solid tumors, we undertook this retrospective study of KIR–HLA interactions. To examine the impact of autologous KIR–HLA ligands, we analyzed the HLA epitopes in patients with adult AML who benefited from autologous SCT (n = 164). The median age of the patients was 34 years (range, 15–64) and the subjects consisted of 63 females and 101 males. All patients received our modified TAM conditioning, which consisted of fractionated total body irradiation (12 Gy, five fractions in 3 days) from day –8 to –6, followed by intermediate-dose cytarabine (Ara-C; 1.5 g/m2 over 3 h every 12 h for six doses) from day –5 to –3, and melphalan (100 mg/m2 over 30 min) on day –2 only. Following consolidation chemotherapy, we collected peripheral blood stem cells after administering granulocyte colony-stimulating factor in all patients, except for 17 poorly mobilizing patients who received peripheral blood stem cells plus bone marrow together. The median infused CD34+ cell dose was 4.2 × 106/kg (range, 0.4–40.7). Finally, the effects of the KIR genotype compared with HLA ligands on the autologous SCT outcomes were examined in 81 patients who were typed for the presence or absence of 19 different KIR genes and pseudogenes using a polymerase chain reaction-based sequence-specific primer method with the Pel-Freez kit, according to the manufacturer's protocol (Invitrogen, Carlsbad, CA). KIR and HLA typing are defined by two subgroups of KIR ligands called C1 and C2. Furthermore, we divided C1/C1 homozygotes into two different KIR ligand patterns according to the HLA typing results: C1 homozygote homodimers (such as HLA-Cw3 and -Cw3; n = 32) and C1 homozygote heterodimers (such as HLA-Cw3 and -Cw8; n = 71). Fifty-three patients were typed as C1/C2 heterozygotes. The median follow-up for surviving patients was 65 months (range, 5–121). The majority of patients had intermediate (n = 90) or unfavorable (n = 41) cytogenetic features. At present, 66 patients (40%) have relapsed, and 94 patients (57%) have survived, while 10 (6%) died due to non-relapse causes. The Kaplan–Meier estimated 5-year overall and event-free survival (EFS) rates were 55% (95% CI, 50–60%) and 52% (95% CI, 48–56%), respectively. According to the consistent results of analyses of the HLA epitopes and genotypes, HLA ligand C1/C2 heterozygotes were compared with C1/C1 homozygotes. Heterozygotes, defined as KIR-HLA ligand matches, tended to have a better long-term EFS (P = .0636) and had a significantly lower relapse rate (P = .031). The number of infused CD34+ cells at the time of autologous SCT (P = .0279), FAB subtypes (M2 vs. other subtypes) (P = .0375), and risk grouping by cytogenetics (P = .0005) were other factors showing statistical significance on EFS and relapse. Since our findings are based on a single disease entity (i.e., adult AML), they suggest that autologous KIR–HLA ligands are, at least in some ways, critical for the influence of autologous NK immunomodulation on antileukemic effects, especially considering the impact of activating KIR–ligand activity on the long-term survival. Therefore, the identification of “ receptor–ligand ” effects could be useful as a prognostic marker and may be important in predicting patients who can expect long-term leukemia-free survival after autologous SCT for AML. Disclosures:No relevant conflicts of interest to declare.