Kurzfassung: Introduction: Outcomes of multidisciplinary and molecular tumor boards have been reported. Lymphoma specific tumor board outcomes have not been reported in the molecular era. In addition, the utility of multi-site, interactive tumor boards using videoconference technology are not widely reported. We prospectively followed the outcomes of a multidisciplinary multi-site lymphoma tumor board in the molecular era and during a change in the revision of the World Health Organization Classification in first published in 2016. Methods: The Mayo Clinic Lymphoma Tumor Board is a component of the international Mayo Clinic Care Network (MCCN). The format includes the clinical case presentation, presentation of radiology and hematopathology findings by the appropriate specialist, proposed treatment options, review of the literature pertinent to the case, and discussion followed by recommendations. Requirement for presentation includes having a diagnosis of lymphoma with pathology reviewed at Mayo Clinic, Rochester, MN (MCR). Pathology and radiology material, when relevant to the case, are required to be reviewed at MCR and presented by MCR pathologists/radiologists. Patients must be presented prospectively, and have active clinical issues or questions to be addressed. Four cases are presented per 60-minute meeting. 309 consecutive highly selected cases with a diagnosis of lymphoma were presented at the Mayo Clinic Lymphoma Tumor Board from 2014 to 2018. The pathology material was independently reviewed by the presenting hematopathologists and radiology material by the presenting radiologist. Participants are office based and included multiple members of the health care team which also incudes pharmacists, clinical research associates affiliated with lymphoma research, and physicians in training. Recommendations were prospectively tracked for changes in radiology interpretation, pathologic diagnosis, and treatment approaches. Actual follow-up of all patients after the meeting was not allowed in the MCCN. Participation in the meeting can be either via in-room attendance at MCR, video conference at a participating MCCN site, or via non-participatory live-stream online. Results: 309 cases were presented were presented from 2014-2018. 258 cases were from MCR, and 51 were not physically seen at MCR. 16 cases were presented at a subsequent meeting for further recommendations in the course of their disease after the initial presentation. 54% of patients presented had changes in some aspect of their care as a result of the meeting. Changes in radiologic interpretation occurred in 5 (1.6%) patients. The pathologic diagnosis changed in 27 (8.7%). Additional testing was recommended in 44 (14%). Clinical management changes were recommended in 90 (29%) cases. These included alterations in treatment approach in 43 (14%), change from undecided to pursuit of treatment 10 (3%), change from undecided regarding treatment approach to further diagnostic testing 4 (1.3%), change from observation to treatment 9 (3%), change from treatment to observation 4 (1.3%), and treatment to further tests in 2 (0.6%) Site in room average attendance (internal/external) was 16.8/8.6. Non-participatory live-stream attendance was not possible to track. In an annual electronic evaluation of this activity, 93% of the responders reported an improvement in knowledge and competence, and 100% recommended no changes to the format of the conference. Enhancements over time have included Continuous Medical Education credit, an in room microscope, and real-time radiology images. Selected cases will now be on line on an international web site. Conclusion: In this highly selected group of lymphoma cases from multiple sites over a 4-year period, 54% of the (167/309) case presentations resulted in changes to some aspect of care as a direct result of this tumor board. A multidisciplinary lymphoma tumor board approach was of value, efficacious, and meaningfully impacted lymphoma patients while substantially enhancing interdisciplinary interactions. Disclosures Ansell: Celldex: Research Funding; Seattle Genetics: Research Funding; Takeda: Research Funding; Bristol-Myers Squibb: Research Funding; Pfizer: Research Funding; Merck & Co: Research Funding; LAM Therapeutics: Research Funding; Regeneron: Research Funding; Trillium: Research Funding; Affimed: Research Funding.

Kurzfassung: Introduction: DNA mismatch repair (MMR) is a major mechanism cells use to repair erroneous insertion or deletion of bases during DNA replication. MMR deficiency (MMR-d), including rare germline mutations (Lynch syndrome) and somatic inactivation, has been extensively studied in solid tumors, such as colon, endometrial, pancreatic, and ovarian cancers. The prevalence of MMR-d in solid tumors ranges from 1% - 20% of somatic defects, and patients with MMR-d tumors have a longer overall survival. It is also well-known that MMR is an integral part of activation-induced cytidine deaminase (AID)-mediated somatic hypermutation and immunoglobulin class switch processes in normal mature B lymphocytes, while mice deficient in the MMR genes are prone to develop T and B cell lymphomas. It is also known that follicular lymphoma (FL) carries a high degree of somatic hypermutation with some heterogeneity induced by AID. Our understanding of MMR status in human blood cancers, especially in FL remains very limited. One could hypothesize that MMR-d status could permit cells to acquire and sustain high-degree of mutation rates, better sensitivity to DNA damaging chemotherapy while hindering rapid cell proliferation, which could manifest to a better prognosis in patients. Herein, we conducted an exploratory analysis to understand the frequency of MMR-d status and its prognostic significance in FL. Methods: Following approval of the Institution Review Board, we assessed the expression of MMR proteins; MLH1, PMS2 and MSH6 on formalin fixed paraffin embedded (FFPE) lymph node tissue obtained from patients with FL by immunohistochemistry (IHC) using standard methods on Ventana Benchmark XT automated stainers (Ventana Medical Systems, Tucson, AZ). Dako (clone ES05), Cell Marque (clone EPR3947) and Biocare (clone BC/44) antibodies were used to stain MLH1, PMS2 and MSH6, respectively. Fifty cases of FL with existing FFPE blocks were selected randomly. The expression of MLH1, PMS2 and MSH6 proteins in the tumor cells was scored as 0, +1 or +2, (Figure 1A). Cases with absence of the IHC signal (score of 0) in any one of the three proteins were classified as MMR-d. Progression free survival at 12 months (PFS12) or 24 months (PFS24) was defined as being free from disease progression or death at 12 or 24 months, respectively. All time-to-event analyses were done from the time of diagnosis. Results: Fifty patients with FL were included in the study. The median age at diagnosis was 65 years (range 34-85) and 58% were females. At initial diagnosis, 36 (72%) patients had advanced stage (stage 3, n=8, stage 4, n=28) disease. Of the 50 patients, 26 (52%) required treatment; chemotherapy (n=14), radiation treatment alone (n=9), surgery alone (n=3). Out of the 50 patients, 23 (46%) were classified as MMR-d due to lack of expression of one of the three assessed proteins: MLH1 (n=1, 2%), PMS2 (n=11, 22%) and MSH6 (n=19, 38%). The patient who had MLH1 loss had concomitant PMS2 loss. Stage IV disease was observed in 52% of the MMR-d patients and 59% in the MMR proficient (MMR-p) patients, p=0.77. Median age at diagnosis was 62 (range: 34-84) years and 67 (range: 34-85) years in MMR-d and MMR-p patients, respectively, p=0.1. FLIPI score was similar between the MMR-d [low n=10 (43%), intermediate n=9 (39%), high n=4 (18%)] and MMR-p [low n=5 (18%), intermediate n=14 (52%), high n=8 (30%)] patients, p=0.16. Fourteen (61%) of MMR-d patients required initiation of therapy upon diagnosis compared to 12 (44%) of MMR-p patients, p=0.27. The median follow-up for the entire cohort was 17 years [95% confidence interval (CI): 11.7-29.4]. The median overall survival (OS) of MMR-d patients was 10 years (95%CI: 7.8-20.7) compared to 6 years (95%CI: 4.5-NR) in MMR-p patients, p=0.036, Figure 1B. In patients with MMR-d and MMR-p, 83% and 55% achieved PFS12, p=0.04 and 65% and 41% achieved PFS24, p=0.08, respectively. After adjusting for FLIPI score, MMR status remained associated with OS (MMR-d HR: 0.51, 95%CI: 0.2-1.02, p=0.05). Discussion and Conclusion: In this pilot study, MMR-d in the FL tumors was common (46%) and, as predicted, was associated with a favorable OS. Association of MMR-d status with PFS in general and patients with early progression (short PFS12 and PFS24) and relationship of MMR-d with types of therapy need further study in large FL datasets. Figure 1 Figure 1. Disclosures Paludo: Karyopharm: Research Funding. King: Celgene/BMS: Research Funding. Maurer: Celgene: Research Funding; Genentech: Research Funding; Kite Pharma: Membership on an entity's Board of Directors or advisory committees; Morphosys: Membership on an entity's Board of Directors or advisory committees, Research Funding; Nanostring: Research Funding; Pfizer: Consultancy, Membership on an entity's Board of Directors or advisory committees. Nowakowski: Celgene, NanoString Technologies, MorphoSys: Research Funding; Celgene, MorphoSys, Genentech, Selvita, Debiopharm Group, Kite/Gilead: Consultancy, Membership on an entity's Board of Directors or advisory committees. Witzig: Karyopharm Therapeutics, Celgene/BMS, Incyte, Epizyme: Consultancy, Membership on an entity's Board of Directors or advisory committees; Celgene/BMS, Acerta Pharma, Kura Oncology, Acrotech Biopharma, Karyopharm Therapeutics: Research Funding.

Kurzfassung: Introduction Due to the higher metabolic demand, malignant cells have an increased dependency on the nucleocytoplasmic trafficking of proteins, as compared to normal cells. Chromosome region maintenance protein 1 (CRM1), encoded by the XPO1 gene, is the main protein receptor which facilitates export of molecules, including tumor suppressor proteins, from the nucleus to the cytoplasm thereby making them inactive. Expression of CRM1 in tumor tissue has been shown to be an independent prognostic marker in several solid tumors and in acute myeloid leukemia; high CRM1 expression by immunohistochemistry (IHC) was associated with more aggressive disease and shorter survival. Importantly, selinexor, a first in class small molecule inhibitor of CRM1, was recently approved for the treatment of relapsed diffuse large B-cell lymphoma (DLBCL). The expression of CRM1 on tumor cells and the assessment of its prognostic impact have not been studied in patients (pts) with DLBCL or primary mediastinal B-cell lymphomas (PMBCL). Methods Paraffin embedded tumor tissue from pts with DLBCL or PMBCL treated with immunochemotherapy was assessed for CRM1 expression through IHC on tissue microarray (TMA). CRM1 anti-rabbit monoclonal antibody (Cell Signaling, catalog-no: 46249) was used at 1:100 dilution. Tumor cell grading was based on CRM1 staining in tumor cells compared to background non-malignant lymphocytes and non-malignant lymphocytes in spleen and tonsillar tissue controls. Renal cell carcinoma (RCC) was used as a positive control [known high levels of CRM1 staining (Inoue et al, J Urol, 2012)] . Two expert hematopathologists (RLK & AJW) independently scored CRM1 nuclear staining and assigned a grade of 0-3; 0 (no definitive nuclear staining, equal to background lymphocytes), 1 (dim nuclear staining), 2 (consistent nuclear staining, nuclear detail still visible behind the stain) and 3 (strong nuclear staining obscuring most nuclear detail, staining equivalent to RCC control). The average CRM1 score per case across all available cores on the TMA was calculated. Low CRM1 expression for a case was arbitrarily defined as a score of 0-2.0; high CRM1 expression was score 2.1-3.0. Scoring reliability between reviewers and between cores was assessed using intra-class correlation coefficient; score 0.75-0.90 was considered as a good scoring reliability. Event-free survival (EFS) was defined as time from diagnosis to progression, relapse, retreatment, or death. The association of CRM1 expression and risk of failing to achieve EFS at 24 months after diagnosis (EFS24) was estimated using odds ratios (OR) and 95% confidence intervals (CI) from logistic regression models, while the association of CRM1 expression with continuous EFS and overall survival (OS) was estimated using Kaplan-Meier curves and hazard ratios (HR) and 95% CI from Cox regression models. Results Tumor tissue from 282 pts was studied for CRM1 staining, including 275 pts with DLBCL and 7 pts with PMBCL. Median age of the study population was 61 years (range: 18-93) and 59% were male. The median follow-up for the entire cohort was 88.6 months. The first-line treatment regimens and baseline patient characteristics at diagnosis are outlined in Figure 1A. Of the 282 pts, 200 (71%) had high level of CRM1 expression and 82 (29%) had low CRM1 expression [only 4 (1.4%) had no or 0 staining]. Intra-class correlation coefficient to measure scoring reliability was 0.8. There was no difference in International Prognostic Index (IPI), ECOG performance score, lactate dehydrogenase or age at diagnosis among the groups with high CRM1 expression compared to low CRM1 expression (Figure 1A). The EFS24 failure was 29% for pts with low CRM1 expression while 26% in pts who had high CRM1 expression, OR=1.16, 95% CI 0.63-2.07; p=0.63. Null associations were also observed for EFS (HR=1.21, 95% CI 0.80-1.83; p=0.38) and OS (HR=1.02, 95% CI 0.61-1.69; p=0.95), (Figure 1B, C). Results were similar when adjusted for gender and IPI. Conclusion CRM1 expression by IHC on paraffin embedded tumor tissue is feasible in DLBCL and PMBCL. These data demonstrate that the CRM1 protein, the target for selinexor, is indeed expressed in the vast majority of these tumors; only 1.4% had no staining. However, CRM1 expression by IHC is not a prognostic marker for EFS24, EFS or OS. Whether CRM1 staining predicts selinexor response has not been studied but should be included in any new studies using CRM1 inhibitors. Disclosures Maurer: Nanostring: Research Funding; Morphosys: Membership on an entity's Board of Directors or advisory committees; Pfizer: Membership on an entity's Board of Directors or advisory committees; Kite: Membership on an entity's Board of Directors or advisory committees; Celgene / BMS: Research Funding. Cerhan:BMS/Celgene: Research Funding; NanoString: Research Funding. Witzig:Acerta: Research Funding; Immune Design: Research Funding; Incyte: Consultancy; MorphSys: Consultancy; Celgene: Consultancy, Research Funding; Spectrum: Consultancy; Karyopharm Therapeutics: Research Funding; AbbVie: Consultancy.

Kurzfassung: Abstract 3146 Background: High dose chemotherapy and stem cell transplantation (HDSCT) has been a standard of care for younger patients with adequate organ function since the early 1980s, due to its superiority over standard chemotherapy in prolonging disease-free and overall survival. Immunomodulatory agents, including thalidomide and lenalidomide, have significant single-agent activity and an additive effect when combined with melphalan. Preclinical data suggest an increased DNA damage and an anti-angiogenic effect with the combination. Additive clinical benefits were also observed when the 2 agents were used in combination in non-transplant settings. The antimyeloma effects of both agents are dose-dependent with myelosuppression being the dose limiting toxicity (DLT). This toxicity can be attenuated with stem cell rescue. Purpose: We conducted a phase I/II trial designed to evaluate the safety and efficacy of combining lenalidomide with high-dose melphalan as conditioning for autologous transplant for myeloma. The phase I portion of the study is complete and the results are reported in this abstract. Experimental Design: The enrolled patients included any patients with myeloma, regardless of the status of the disease, undergoing high dose melphalan for autologous stem cell transplantation. The melphalan dose was fixed (200 mg/m2) while the doses of lenalidomode were escalated from 50, 75, 100, and 150 mg/m2 administered orally days -7 to +2 of the transplantation. Dose escalation was based upon a 3+3 phase I design. DLTs were defined as grade ≥4, both hematologic and non-hematologic, occurring between days -7 to -2 which prevents subjects from undergoing stem cell transplantation, or grade 3 or 4 non-hematologic toxicity occurring after day -2 that does not resolve to a grade 2 or less by day +30 after transplantation, or delayed engraftment. The response was assessed at day +100 post transplantation using the International Myeloma Working Group criteria. Results: 13 patients participated in the phase I portion of the study from September 2010 to May 2012. Patients ages ranged from 42– 72 years (median 63 years). Seven patients were undergoing their first autologous transplant with 2 patients having had 2 lines of previous therapy and 5 having one line of therapy. Six patients were undergoing their second transplantationas salvage for control of progressive disease and all had more than 3 lines of prior therapy. At baseline, 5 patients had progressive disease, 1 had SD, 3 had PR, 3 had VGPR and 1 had CR as responses to their most recent lines of therapy. The median time for ANC and platelet engraftment was 10 days and no delayed engraftment was observed. Toxicities and posttransplant hematopoietic recovery rates were similar to historical data observed with single agent high dose melphalan. The most common grade ≥ 3 adverse events were myelosuppression, neutropenic fever and electrolyte abnormalities, all of which are commonly observed with single agent high dose melphalan. Adverse events related to the study drugs were electrolyte abnormalities (hypokalemia, hyperkalemia and hypocalcemia), gastrointestinal side effects and rash, all of which were grade 1 to 2 and manageable without a delay or discontinuation of the study drugs. One patient died from disease progression prior to scheduled disease evaluation. One patient has not yet reached day +100 post transplant. Therefore, responses were evaluable for 11 patients. Three patients achieved stringent CR (27%), 3 CR (27%), 2 VGPR (18%), 3 PR (27%) and one had progressive disease (9%). The overall response rate was 91%, with 72% achieving VGPR or better. All patients had adequate count recovery and were able to initiate lenalidomide maintenance treatment by day +100 to +110 post transplantation. Conclusions: The use of high dose lenalidomide in conjunction with high-dose melphalan is well tolerated, with preliminary data suggesting that the combination is highly efficacious. DLT was not observed; therefore the recommended phase II dose is 150 mg of lenalidomide orally on days -7 to +2 in combination with melphalan 200 mg/m2. The phase II portion of this trial is ongoing in patients undergoing first HDSCT. Complete response at 3 months post transplantation is the primary end point. Disclosures: Off Label Use: Lenalidomide in myeloma transplant. Abonour:Celgene: Honoraria, Speakers Bureau; Millenium: Honoraria, Speakers Bureau.

Kurzfassung: Introduction: Chimeric antigen receptor (CAR) T-cells redirected against CD19 have demonstrated remarkable clinical activity in children and adults with relapsed/refractory (r/r) B-cell malignancies. The risk of lineage switch (LS) following CD19-directed therapies has been well documented but has been primarily limited to case reports. Additionally, the risk of subsequent malignant neoplasms (SMN) following CAR T-cells has not yet been described. Distinguishing LS (B-ALL to myeloid malignancy) from a therapy-related myeloid neoplasm is both clinically and biologically relevant. The former emerges from a highly refractory leukemic clone, likely resistant to salvage therapy, whereas the latter represents a new malignancy that can be associated with long-term survival. Methods: We conducted a multicenter, retrospective review of children and young adults with r/r B-acute lymphoblastic leukemia (B-ALL) who received either commercial tisagenlecleucel or 1 of 3 investigational murine-based CD19-CAR constructs on clinical trials at 7 US centers between 2012-2019. Patients diagnosed with B-ALL before age 25 years were included and patients who had received any prior CAR product were excluded. Results: Of 420 CAR-treated patients, with a median follow-up of 30.1 months, 12 (2.9%) experienced LS and 6 (1.4%) developed a SMN (Table). The median time to diagnosis of LS following CAR T-cell infusion was significantly shorter compared to diagnosis of SMN (65.5 days vs. 883.5 days; p=0.005). Eleven of 12 patients (91.7%) with LS converted to acute myeloid leukemia (AML). One patient converted to mixed phenotype acute leukemia, B/myeloid type. The leukemia of 10 of 12 patients with LS harbored cytogenetics similar to those at initial diagnosis. For the remaining 2 patients with LS, cytogenetics were unavailable, but the leukemias were considered LS by the treating institution. KMT2Ar rearrangement (KMT2Ar) was a predominant cytogenetic abnormality seen in patients with LS. Overall, 38 of 420 patients (9%) had a KMT2Ar. KMT2Ar was present in 9 of 12 (75%) patients with LS compared to 20 of 408 (7.1%) non-LS patients (p & lt;0.001). Patients with LS were younger at initial diagnosis compared to the remaining cohort (median age, 1.6 years vs. 7.7 years; p=0.001), reflecting the inherent association between KMT2Ar and infant ALL. Otherwise, there were no significant differences in gender, prior hematopoietic stem cell transplant (HSCT), prior blinatumomab exposure, or CAR response. Within the KMT2Ar cohort, 31 (81.6%) patients achieved a complete remission post-CAR. Eight of these patients received a consolidative HSCT (representing 4 first and 4 second HSCTs). No KMT2Ar patient experienced a post-HSCT LS and 3 are alive with a median follow-up of 1164 days post-CAR. In contrast, of the 23 KTM2Ar patients who did not receive HSCT post-CAR, 7 developed LS and 14 are alive with a median follow-up of 864 days post-CAR. Relative contraindications to post-CAR HSCT included a prior HSCT (n=11) or early LS (n=5). Of the 7 CAR non-responding patients with KMT2Ar, 2 (28.6%) had rapid emergence of LS by the first restaging timepoint. There are no long-term survivors following LS, regardless of KMT2A status, dying a median of 123 days (range, 36-594 days) after diagnosis of LS. The 6 SMNs were cholangiocarcinoma, synovial sarcoma, malignant melanoma and 3 therapy-related myeloid neoplasms (MDS/AML), distinguished from LS based on loss of original cytogenetics. Notably, 4/6 (67%) patients that developed a SMN had received an allogeneic HSCT prior to development of SMN. Four patients (67%) remain alive and in remission with a median follow-up of 304 days after diagnosis of SMN, including 2 patients with MDS/AML. Conclusions: In the largest series of pediatric patients treated with CAR T-cell therapy, we show that LS occurs in 2.9% of children. The presence of a KMT2Ar was the biggest risk factor, with 23.7% of these patients experiencing LS. We found that LS can occur very early in a patient's post CAR T-cell course, and despite a variety of treatment approaches, the outcomes for these patients are dismal. Given the predisposition to LS, the role for consolidative HSCT in KMT2Ar patients warrants further study. Limited by a short follow-up period, we saw SMNs in only 1.4% of our patients. Causality is unknown and likely unrelated to CAR-T, but this further supports the long-term safety of CAR T-cells in children with B-ALL. Figure 1 Figure 1. Disclosures Borowitz: Amgen, Blueprint Medicines: Honoraria. Lee: Harpoon Therapeutics: Consultancy; Amgen: Membership on an entity's Board of Directors or advisory committees; BMS: Membership on an entity's Board of Directors or advisory committees; Kite Pharma: Other: trial funding; Gilead: Other: trial funding. Grupp: Novartis, Adaptimmune, TCR2, Cellectis, Juno, Vertex, Allogene and Cabaletta: Other: Study steering committees or scientific advisory boards; Novartis, Roche, GSK, Humanigen, CBMG, Eureka, and Janssen/JnJ: Consultancy; Novartis, Kite, Vertex, and Servier: Research Funding; Jazz Pharmaceuticals: Consultancy, Other: Steering committee, Research Funding. Verneris: jazz: Other: advisory board; Novartis: Other: advisory board; Fate Therapeutics: Consultancy. Gore: Mirati: Current equity holder in publicly-traded company; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees; Amgen: Consultancy, Current equity holder in publicly-traded company, Honoraria, Membership on an entity's Board of Directors or advisory committees; Roche/Genentech: Consultancy, Honoraria; Clovis: Current equity holder in publicly-traded company; Celgene: Current equity holder in publicly-traded company, Membership on an entity's Board of Directors or advisory committees; Sanofi Paris: Current equity holder in publicly-traded company; Anchiano: Current equity holder in publicly-traded company; Blueprint Medicines: Current equity holder in publicly-traded company. Brown: Novartis: Membership on an entity's Board of Directors or advisory committees; Takeda: Membership on an entity's Board of Directors or advisory committees; Amgen: Membership on an entity's Board of Directors or advisory committees; Kura: Membership on an entity's Board of Directors or advisory committees; KIte: Membership on an entity's Board of Directors or advisory committees. Pulsipher: Equillium: Membership on an entity's Board of Directors or advisory committees; Adaptive: Research Funding; Jasper Therapeutics: Honoraria. Rheingold: Pfizer: Research Funding; Optinose: Other: Spouse's current employment. Gardner: BMS: Patents & Royalties; Novartis: Consultancy.

Kurzfassung: Over the last decade, allogeneic HCT has been increasingly administered in the United States to adults aged 70 and older with hematologic malignancies. Allogeneic transplant outcomes were reasonable; high comorbidity and ablative conditioning regimens were associated with inferior outcomes.

Kurzfassung: Introduction Children with relapsed T-ALL and T-LL have a dismal prognosis, with survival of less than 25% (Goldberg et al, J Clin Oncol 2003; Reismuller et al, Brit J Haematol 2009). Fewer than a third of children with relapsed T-ALL/LL attain a second remission with standard reinduction therapies (Raetz et al, J Clin Oncol 2008). Nelarabine (NEL) is a purine nucleoside analogue prodrug of AraG, which is resistant to cleavage by endogenous purine nucleoside phosphorylase and cytotoxic to T-lymphoblasts at micromolar concentrations. NEL has substantial single-agent activity in first and multiply relapsed T-ALL (Berg et al, J Clin Oncol 2005). In an effort to improve reinduction rates for children with T-ALL and T-lymphoblastic lymphoma (T-LL) in first relapse, we evaluated the safety and preliminary efficacy of NEL in combination with cyclophosphamide (CPM) and etoposide (ETOP) in this setting. Methods T2008-002: A Phase I trial of NECTAR (Nelarabine, Etoposide and Cyclophosphamide in T-ALL Relapse), is an investigator-initiated collaboration between the Therapeutic Advances in Childhood Leukemia & Lymphoma consortium (TACL), the Pediatric Oncology Experimental Therapeutics Investigators' Consortium (POETIC), and the Innovative Therapies for Children with Cancer consortium (ITCC). Eligible patients had first relapse or initial induction failure of T-ALL or T-LL, no CNS-3, no prior stem cell transplantation, and adequate performance status and organ function. The studyÕs primary objective was to establish the recommended phase 2 doses (RP2D) of NEL and CPM in combination with a fixed dose of ETOP. Subjects received a single course of NEL (325-650 mg/m2) and CPM (330-440 mg/m2) at 1 of 3 assigned dose levels in combination with a fixed ETOP dose (100 mg/m2), each for 5 consecutive days. Intrathecal therapy was administered no less than 7 days prior to or 21 days following the start of a course. Responding patients without dose-limiting toxicity (DLT) were eligible for a second course. The primary study endpoint was the occurrence of dose-limiting toxicity (DLT) during course 1. Secondary endpoints included rates of CR2, complete remission without platelet recovery (CRp), or partial response (PR), and minimal residual disease (MRD) levels at the end of each course. Results Of 19 children enrolled on T2008-002, 6 were enrolled at Dose Level (DL) 1 (NEL 325 mg/m2, CPM 330 mg/m2), 7 at DL2 (NEL 650 mg/m2, CPM 330 mg/m2), and 6 at DL3 (NEL 650 mg/m2, CPM 440 mg/m2). Two potential DLTs led to subject removal during course 1, but were later reversed upon committee review and those subjects replaced. 17 patients were evaluable for DLT and response. Confirmed DLTs occurred in 2 patients: 1 at DL2 (grade 2 (Gr2) motor neuropathy and Gr3 sensory neuropathy) and 1 at DL3 (Gr3 sensory neuropathy). Other ³ Gr3 non-hematologic adverse events are listed in the Table. Of 9 T-ALL patients evaluable for response, there were 2 CRs,1 CRp and 1 CR in the bone marrow/PR in an extramedullary site, with responses at all dose levels, for a response rate of 44% in the T-ALL cohort; at the RP2D, 2/4 evaluable T-ALL patients had a response. Of 8 T-LL patients evaluable for response, there were 2 CRs (1 each at DL1 and DL2), for an overall T-LL response rate of 25%. Eight patients received a second course of NECTAR; 9 subsequently underwent HSCT. MRD levels were available for 2 responding T-ALL patients, with 0.027% and 0.07% blasts after Course 1 and 0.07% and 〈 0.001% blasts after Course 2.TableGrade ³3 Non-Hematologic Adverse Events Occurring in 〉 5% of SubjectsToxicity (CTC3.0)Grade ³ 3 Anorexia3 (16%)Aspartate aminotransferase increased2 (11%)Diarrhoea NOS2 (11%)Febrile neutropenia6 (32%)Hyperkalemia2 (11%)Hypoalbuminaemia3 (16%)Hypocalcaemia4 (21%)Hypokalemia8 (42%)Hypotension NOS2 (11%)Nausea3 (16%)Pleural effusion3 (16%)Vomiting NOS2 (11%)Pain-Other2 (11%) Conclusions The recommended phase 2 doses (RP2D) for NECTAR are NEL 650 mg/m2, CPM 440 mg/m2 and ETOP 100 mg/m2, each given daily for 5 days. The activity and toxicity seen in this phase I dose escalation cohort compare favorably with established reinduction regimens in relapsed T-ALL/LL. An ongoing cohort expansion at the RP2D will better define the activity of NECTAR in first relapse of T-ALL and T-LL. Acknowledgments: Glaxo-Smith-Kline; Higgins Family Foundation; Women's Auxiliary Millennium Chair in Haematology/Oncology Disclosures Whitlock: Glaxo-Smith-Kline: Research Funding. Off Label Use: Nelarabine, cyclophosphamide and etoposide for relapsed T-ALL/T-LL are off-label drug uses.. Zwaan:GSK: Research Funding. Gore:GSK: Research Funding.