Relapse after allogeneic hematopoietic cell transplantation (HCT) is the leading cause of death in acute myeloid leukemia (AML) patients entering HCT with poor-risk features. 1-3 When HCT does produce prolonged relapse-free survival (RFS), it commonly reflects graft-versus-leukemia (GVL) effects mediated by donor T cells reactive with antigens on leukemic cells. 4 As graft T cells have not been selected for leukemia-specificity and frequently recognize proteins expressed by many normal host tissues, GVL is often accompanied by morbidity and mortality from graft-versus-host disease (GVHD). 5 Thus, AML relapse risk might be more effectively reduced with T cells expressing receptors (TCRs) that target selected AML antigens. 6 We therefore isolated a high

• Iron deficiency results in symptom improvement in CEP and could be considered a novel therapeutic approach for this disease.• CEP marrow cells demonstrated improved growth and erythroid differentiation in vitro under conditions of relative iron restriction.Congenital erythropoietic porphyria (CEP) is an autosomal recessive disorder of heme synthesis characterized by reduced activity of uroporphyrinogen III synthase and the accumulation of nonphysiologic isomer I porphyrin metabolites, resulting in ineffective erythropoiesis and devastating skin photosensitivity. Management of the disease primarily consists of supportive measures. Increased activity of 5-aminolevulinate synthase 2 (ALAS2) has been shown to adversely modify the disease phenotype.Herein, we present a patient with CEP who demonstrated a remarkable improvement in disease manifestations in the setting of iron deficiency. Hypothesizing that iron restriction improved her symptoms by decreasing ALAS2 activity and subsequent porphyrin production, we treated the patient with off-label use of deferasirox to maintain iron deficiency, with successful results. We confirmed the physiology of her response with marrow culture studies. (Blood. 2015;126(2):257-261) IntroductionCongenital erythropoietic porphyria (CEP) is an autosomal recessive disorder resulting from mutations in the uroporphyrinogen III synthase (UROS) gene, which encodes the fourth enzyme in the heme synthetic pathway. 1 Reduced UROS activity leads to nonenzymatic conversion of hydroxymethylbilane to isomer I porphyrin metabolites, which accumulate in late erythroid precursors, reticulocytes, and red cells, resulting in ineffective erythropoiesis, hemolysis, and splenomegaly and which disseminate into tissues such as skin to cause severe photosensitivity. Management is largely comprised of sun avoidance, splenectomy, and supportive measures, and in some patients, hematopoietic stem cell transplantation has been effective. [2][3][4] More than 45 mutations in UROS have been identified, 5 and disease severity correlates with the degree that enzymatic activity is reduced. [6][7][8][9] As evidence that additional factors may influence the disease phenotype, a gain-of-function mutation in 5-aminolevulinate synthase 2 (ALAS2), which encodes the first and rate-limiting enzyme in the heme biosynthetic pathway, has been associated with more severe CEP symptoms.10 This raises the question of whether decreased ALAS2 activity would lessen disease severity by decreasing porphyrin production. Deficiency of iron impedes heme synthesis upstream of UROS by decreasing ALAS2 translation via binding of an iron regulatory protein to an iron-responsive element in the 59 untranslated region of ALAS2 mRNA, suggesting a possible therapeutic role for iron restriction in the treatment of erythropoietic porphyrias. 11,12Study design Bone marrow cell cultures Marrow was obtained postmortem from CEP patient 1 with parental consent. Marrow was also obtained from her younger sister (patient 2) with institutional review board a...

Background: Blasts and leukemic stem cells of acute myeloid leukemia (AML) as well as several other hematologic malignancies express CD123, potentially providing a target for novel therapies. Vibecotamab (XmAb14045, SQZ622) is a potent bispecific antibody targeting both CD123 and CD3 that stimulates targeted T cell-mediated killing of CD123-expressing cells, regardless of T cell antigen specificity. It is a full-length immunoglobulin molecule designed to be dosed intermittently. Methods: Patients with relapsed or refractory AML, B-cell acute lymphoblastic leukemia (B-ALL), blast phase chronic myelogenous leukemia, or blastic plasmacytoid dendritic cell neoplasm were eligible to enroll on this first-in-human, multicenter, open-label phase 1 dose-escalation study (XmAb14045-01) with standard 3+3 design. The primary objective was to estimate the maximum tolerated dose (MTD) or recommended dose and schedule of vibecotamab. Secondary objectives included safety, preliminary antileukemic activity, and pharmacokinetics/pharmacodynamics of vibecotamab. Treatment was administered weekly in 28-day cycles, using a weight-based dose with 3 escalating doses in the first week followed by escalating weekly doses. Therapy was continued for as long as tolerated and there was continuing evidence of therapeutic benefit in the opinion of the investigator. Treatment response was assessed by the 2017 European LeukemiaNet (ELN) criteria after Cycle 1 and after each odd-numbered cycle. CRS was graded using the CRS revised grading system (Lee et al., Blood, 2014). Results: At data cut-off, 104 patients with AML, 1 with B-cell ALL, and 1 with CML as their primary diagnosis have been treated at dosages from 0.003 to 12.0 µg/kg vibecotamab. Patients had a median age of 63 years and were heavily pretreated (median of 3 prior therapies [range 1-8], including 32 (30%) who had undergone prior allogeneic stem cell transplantation). The recommended initial priming dose is 0.75 µg/kg; no MTD has been identified. CRS or its component symptoms was the most common treatment-emergent adverse event (TEAE). CRS occurred in 62 of 106 patients (85% grade 1-2, 15% grade ≥3), the majority on the first dose. Additional events consistent with CRS or infusion related reaction were seen in 24% of subjects (chills, fever, tachycardia, hypotension, etc.), and they were mostly mild or moderate severity. No myelosuppression requiring dose modification or evidence of tumor lysis syndrome was seen. Response of CR (2), CRi (3) or MLFS (2) was observed in 7/51 patients (ORR=14%) treated at higher dose levels (0.75 µg/kg). Stable Disease was observed in an additional 36 patients (71%). No CR, CRi, or morphologic leukemia-free state (MLFS) responses were observed at lower doses. Antileukemic activity occurred quickly; 6 out of 7 responders achieved at least a MLFS response after first cycle. A characterization of responders versus non-responders revealed responding patients harbor a lower burden of disease and specific T-cell subtypes. No association was found between response status and CD123 target expression on AML blasts. Conclusions: Vibecotamab demonstrated evidence of antileukemic activity in heavily pretreated patients with relapsed/refractory AML treated at the ≥0.75 µg/kg doses cohorts, with a 14% response rate. CRS was the most common toxicity but was generally manageable with premedications. The study is ongoing with further optimization of dose and schedule. Biomarker data suggest a population of AML patients that are more likely to respond. Additional information will be provided at the time of the meeting. Disclosures Ravandi: Celgene: Consultancy, Honoraria; BMS: Consultancy, Honoraria, Research Funding; Amgen: Consultancy, Honoraria, Research Funding; Orsenix: Consultancy, Honoraria, Research Funding; Abbvie: Consultancy, Honoraria, Research Funding; Astellas: Consultancy, Honoraria, Research Funding; Xencor: Consultancy, Honoraria, Research Funding; Jazz Pharmaceuticals: Consultancy, Honoraria, Research Funding; AstraZeneca: Consultancy, Honoraria; Macrogenics: Research Funding. Stock:Adaptive Biotechnologies: Consultancy, Membership on an entity's Board of Directors or advisory committees; Research to Practice: Honoraria; American Society of Hematology: Honoraria; Leukemia and Lymphoma Society: Research Funding; Novartis: Research Funding; Abbvie: Honoraria, Research Funding; Agios: Consultancy, Membership on an entity's Board of Directors or advisory committees; Morphosys: Consultancy, Membership on an entity's Board of Directors or advisory committees; Kite: Consultancy, Membership on an entity's Board of Directors or advisory committees; Amgen: Consultancy, Membership on an entity's Board of Directors or advisory committees; Servier: Consultancy, Membership on an entity's Board of Directors or advisory committees; Jazz Pharmaceuticals: Consultancy, Membership on an entity's Board of Directors or advisory committees; Pfizer: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; UpToDate: Honoraria. Foran:Xencor: Research Funding; H3Biosciences: Research Funding; Agios: Honoraria, Research Funding; Trillium: Research Funding; Takeda: Research Funding; Kura Oncology: Research Funding; Aptose: Research Funding; Aprea: Research Funding; Actinium: Research Funding; Boehringer Ingelheim: Research Funding; Abbvie: Research Funding; BMS: Membership on an entity's Board of Directors or advisory committees; Pfizer: Membership on an entity's Board of Directors or advisory committees; Servier: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees; Revolution Medicine: Consultancy. Mawad:Adaptive Biotechnologies: Speakers Bureau; Abbvie: Speakers Bureau. Blum:Celyad: Research Funding; Amerisource Bergen: Honoraria; Syndax: Membership on an entity's Board of Directors or advisory committees; Leukemia and Lymphoma Society: Research Funding; Xencor: Research Funding. Yang:Xencor: Current Employment, Current equity holder in publicly-traded company; Jazz Pharmaceuticals: Current equity holder in publicly-traded company, Ended employment in the past 24 months. Pastore:Novartis NIBR East Hanover New Jersey: Current Employment, Current equity holder in publicly-traded company; Memorial Sloan Kettering Cancer Center: Ended employment in the past 24 months. Johnson:Xencor: Current Employment, Current equity holder in publicly-traded company. Zheng:Xencor: Current Employment, Current equity holder in publicly-traded company; Tocagen: Ended employment in the past 24 months. Yilmaz:Pint Pharma: Honoraria; Pfizer: Research Funding; Daicho Sankyo: Research Funding. Mims:Syndax Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; Abbvie: Membership on an entity's Board of Directors or advisory committees; Kura Oncology: Membership on an entity's Board of Directors or advisory committees; Leukemia and Lymphoma Society: Other: Senior Medical Director for Beat AML Study; Jazz Pharmaceuticals: Other: Data Safety Monitoring Board; Agios: Consultancy; Novartis: Speakers Bureau.

We investigated the risk associated with variants in three genes involved in estrogen biosynthesis, CYP11A1, CYP17A1, and CYP19A1, in the population-based case control study of Estrogen, Diet, Genetics, and Endometrial Cancer. This study was conducted in New Jersey in 2001-2006 with 417 cases and 402 controls. For CYP11A1, there was no association between the number of [TTTTA] n repeats (D15S520) and risk. For CYP17A1, risk was somewhat lower among women with the C/C genotype at T-34C (rs743572) (adjusted OR=0.65, 95% CI 0.41-1.02). For CYP19A1, risk was lower among women homozygous for the 3-base pair deletion (rs11575899) in exon 4 (adjusted OR=0.44, 95% CI 0.26-0.76), while the number of [TTTA] n repeats was not significantly related to risk: the adjusted OR for n=7/7 repeats vs n>7/>7 repeats was 0.81 (95% CI 0.54-1.23). In stratified analyses, results for CYP19A1 were stronger among women with higher (>27.4) body mass index: for the homozygous deletion, OR=0.30 (95% CI 0.15-0.62); for the n=7/7 genotype, OR=0.49 (95% CI 0.26-0.93). The interaction between the n=7/7 genotype and BMI was statistically significant (p=0.01). The insertion/deletion variant in CYP19A1 appears to be related to risk of endometrial cancer; risk associated with variants in this gene may vary according to BMI.

In this prospective, randomized, phase II "pick the winner" trial we assessed the efficacy of transplant conditioning with treosulfan/fludarabine ± 2 Gy total body irradiation (TBI) in reducing post-transplant relapse in 100 patients, aged 2 to 70 years (median, 57), with myelodysplastic syndrome (MDS)/chronic myelomonocytic leukemia (n = 51) or acute myeloid leukemia (AML; n = 49). Patients received i.v. treosulfan, 14 g/m/day on days -6 to -4 and i.v. fludarabine, 30 mg/m/day on days -6 to -2, alone or combined with 2 Gy TBI (day 0). Donors were related (n = 43) or unrelated (n = 57). When a planned interim analysis showed superior progression-free survival in the TBI arm (P = .04), all subsequent patients received TBI. With a follow-up of 12 to 40 months (median, 20), the 1-year overall survival was 80% for the TBI arm and 69% for the non-TBI arm. The 1-year cumulative incidence of relapse was 22% and 34%, respectively (P = .06). Among patients with low-risk disease the 1-year relapse incidence was 15% and 31% (P = .20) and for patients with high-risk disease, 26% and 36% (P = .18), respectively. Among MDS patients the 1-year relapse incidence was 27% versus 33% (P = .49) and among AML patients 16% versus 35% (P = .05), respectively. The largest difference was among patients with unfavorable cytogenetics, with 1-year relapse incidences of 31% and 63% (P = .18), respectively. Nonrelapse mortality in this high-risk patient population was 9% at 6 months and did not differ between arms. Thus, treosulfan/fludarabine/low-dose TBI provided effective conditioning for allogeneic hematopoietic cell transplantation in high-risk patients up to 70 years of age. The addition of TBI had a more profound effect in patients with AML than in those with MDS. High-risk disease features were associated with a lower overall success rate. Further studies are warranted.

Introduction Fusion of BCR-ABL1 genes causes chronic myeloid leukemia (CML). As a reliable marker of disease burden, it also serves as the target of tyrosine kinase inhibitors (TKIs). New more sensitive molecular diagnostic tools for BCR-ABL1 can contribute to therapeutic decision-making, especially in considering drug discontinuation for patients enjoying prolonged deep molecular response. Areas covered Several novel platforms are transforming CML molecular diagnostics to enable faster point-of-care devices, better understanding of clonal diversity and resistance mutations. Here, we review these molecular platforms, knowing implementation in other hematological malignancies will ensue. Expert commentary Treatment with TKI in CML is the first example of a highly effective targeted therapy. Monitoring of BCR-ABL1 mRNA is standard in assessing disease burden being highly predictive of outcomes recommended by both ELN and NCCN; however, studies has demonstrated poor adherence to these recommendations. In both clinical practice and assay performance, further optimizing of BCR-ABL1 monitoring can be envisioned including point-of-care methods for increased availability of rapid, standardized testing and increasingly sensitive molecular assays that allow for quantification of MRD and detecting resistance mutations.

Despite the successes of tyrosine kinase inhibitors (TKIs) in improving outcomes in patients with chronic myeloid leukemia (CML) and Philadelphia-positive acute lymphoblastic leukemia (Ph+ ALL), allogeneic hematopoietic stem cell transplantation (HSCT) continues to be an important and potentially curative option for selected patients with either disease. After HSCT, TKIs are increasingly being used to treat or prevent disease relapse, and practice patterns suggest that these TKIs are often chosen empirically without regard to pre-HSCT mutation status. We investigated whether ABL kinase domain mutations persist after transplantation, and thus whether pre-HSCT mutation status should inform the selection of post-HSCT TKIs in these patients. We retrospectively analyzed adults who underwent allogeneic HSCT for CML and Ph+ ALL at our institution between 2000 and 2010, and identified subjects who had detectable BCR-ABL transcripts by polymerase chain reaction (PCR), as well as available RNA for Sanger sequencing of the ABL kinase domain, in both the pre- and post-HSCT settings. In total, 95 CML and 20 Ph+ ALL patients with positive PCR transcripts were identified, of which 10 (10.5%) and 4 (20.0%), respectively, were found to have pre-HSCT ABL kinase mutations known to confer TKI resistance. In 9 (64.2%) of these 14 patients, the same kinase mutation was also detectable at an average time of 191 days post-HSCT. Seven (50.0%) of the 14 harboring mutations had relapsed/refractory disease by last follow-up, of which, in retrospect, 6 had received a predictably ineffective TKI within the first 100 days following transplant, based on our mutation analysis. These data support the idea that pre-existing mutations in the ABL kinase domain, frequently associated with resistance to TKIs and prevalent in a transplant population, are persistently detectable in the majority of patients after transplant. We propose that such resistance patterns should be considered when selecting TKIs in the post-HSCT setting, including clinical trials of post-HSCT TKI prophylaxis.

Leukemic relapse after allogeneic hematopoietic cell transplantation (HCT) remains a major cause of treatment failure in patients (pts) who enter HCT with high-risk acute myeloid leukemia (AML). Therapeutic "graft-versus-leukemia" (GVL) effects are often accompanied by substantial morbidity and mortality caused by graft versus host disease (GVHD), as graft T cells have not been selected for specificity for leukemia antigens. To selectively promote GVL without inducing GVHD, we first developed a therapy employing CD8+ cytotoxic T lymphocyte (CTL) clones targeting Wilms' Tumor Antigen 1 (WT1), a non-polymorphic protein over-expressed 10-1000x by leukemic cells compared to normal CD34+ cells. Although CTL clones derived from HLA matched donors infused in the corresponding pts were safe, the anti-leukemic efficacy was limited in part due to a wide variability of functional avidities obtained for each patient-donor pair and limited persistence of CTL clones (Chapuis A. et al., STM 2013). We therefore identified and characterized a native, high affinity WT1-specific TCR (TCRC4), isolated from screening the peripheral repertoires of healthy HLA A*0201+ donors. Thus this TCR had been subjected to negative thymic selection, which should minimize the potential risk of off-target toxicity. To enhance persistence, we inserted TCRC4 in EBV- or CMV-specific donor substrate cells, with the former preferred based on the higher frequency of central memory (TCM). Twenty-two HLA A*0201+ pts received up to 1010 TCRC4 transduced donor-derived virus-specific cytotoxic T cells (CTL)/m2, following recovery of hematopoiesis after a matched HCT transplant for AML (NCT01640301). Adverse events included expected transient (<24 hours) cytokine release syndromes managed on the general ward and transient lymphopenia (<10 days). No evidence of immediate or delayed off-target or on-target/off-tissue toxicity was observed. Elevenpts with high-risk AML, all of whom had no evidence of disease (NED) at their day 28 post-HCT marrow assessment, received TCRC4-transduced virus-specific CTL (CTLvirus/TCR-C4) on the "Prophylactic Arm" (PA) at a median of 90 days (range 47-190) post-HCT. All 11 pts remain in continued complete remission at a median follow-up of 21.3 months post-HCT. In a matched concurrent cohort of similar high-risk pts who were also NED 28 days post-HCT but did not receive CTLvirus/TCR-C4, 27% had relapsed at 16 months (Figure 1). This suggests the infusion of WT1-specific cells in the post-HCT setting may prevent leukemia recurrence. Although the analysis is still ongoing, preliminary analysis of pts with detectable disease after HCT (11 pts) who received CTLvirus/TCR-C4 on the "Treatment Arm" (TA) revealed evidence of anti-leukemic activity but did not seem to result in a survival advantage compared to matched controls. Correlative studies revealed that overall persistence was significantly decreased in the TA, potentially accounting for the lack of survival benefit. Donor-derived CTLEBV/TCR-C4 (11/11 pts on the PA and 7/11 pts on the TA) persisted at higher frequencies (up to 50% of CD8+ T cells for > 1 year) compared to CTLCMV/TCR-C4 (no persistence >3% beyond 7 days)(Figure 2). Analysis of donor virus-specific populations demonstrated that EBV- compared to CMV-specific cells expressed significantly higher long-lived memory and decreased exhaustion/activation markers, supporting results suggesting human cells derived from predominantly TCM populations are imprinted with a program that enhances post-transfer survival. CTLEBV/TCR-C4 that persisted at high frequencies in the PA not only exhibited an effector phenotype (i.e., did not convert to TCM as had been previously observed) but also expressed Ki67, suggesting continued activation. The transferred CTLEBV/TCR-C4 maintained the ability to secrete IFNg, TNFa and IL-2, preferentially through TCRC4 (Figure 3), and, as no ongoing EBV-reactivation was detected in serum, the results strongly suggest continued WT1-antigen encounter as the driver of proliferation/persistence and a contributing mechanism for AML relapse prevention in the PA. Furthermore, although the infused CTLEBV/TCR-C4 were polyclonal, the dominant clonotypes in the infusion product also composed the majority of persisting cells, suggesting rare "fit" clonotypes expand during cell production and lead to oligoclonal survival in vivo. Disclosures Chapuis: Juno Therapeutics Inc: Research Funding. Yeung:Gilead Sciences: Research Funding. Greenberg:Juno Therapeutics Inc: Equity Ownership, Research Funding.