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Background CD19-directed chimeric antigen receptor (CAR) T-cell therapy (CAR-T) has emerged as effective for relapsed/refractory large B-cell lymphoma (R/R LBCL). The neurologic toxicity seen with CAR-T, referred to as immune effector cell–associated neurotoxicity syndrome (ICANS), is poorly understood. To better elucidate the clinical characteristics, treatment outcomes, and correlative biomarkers of ICANS, we review here a single-center analysis of ICANS after CAR T-cell therapy in R/R LBCL. Methods Patients (n = 45) with R/R LBCL treated with axicabtagene ciloleucel (axi-cel) were identified. Data regarding treatment course, clinical outcomes, and correlative studies were collected. Patients were monitored and graded for ICANS via CARTOX-10 scoring and Common Terminology Criteria for Adverse Events (CTCAE) v4.03 criteria, respectively. Results Twenty-five (56%) patients developed ICANS, 18 (72%) of whom had severe (CTCAE grades 3–4) ICANS. Median time to development of ICANS was 5 days (range, 3–11). Elevated pre-infusion (day 0 [D0]) fibrinogen (517 vs 403 mg/dL, upper limit of normal [ULN] 438 mg/dL, P = 0.01) and D0 lactate dehydrogenase (618 vs 506 units/L, ULN 618 units/L, P = 0.04) were associated with ICANS. A larger drop in fibrinogen was associated with ICANS (393 vs 200, P < 0.01). Development of ICANS of any grade had no effect on complete remission (CR), progression-free survival (PFS), or overall survival (OS). Duration and total dose of steroid treatment administered for ICANS did not influence CR, PFS, or OS. Conclusions ICANS after CAR-T with axi-cel for R/R LBCL was seen in about half of patients, the majority of which were high grade. Contrary to previous reports, neither development of ICANS nor its treatment were associated with inferior CR, PFS, or OS. The novel finding of high D0 fibrinogen level can identify patients at higher risk for ICANS.

Although hematopoietic cell transplantation from an HLA-matched unrelated donor is potentially curative for hematologic malignancies, survival is lower for African Americans compared with Caucasians. Because only approximately 20% of African Americans will have an HLA-matched unrelated donor, many of these patients undergo HLA-haploidentical relative or umbilical cord blood transplantation. In this study, we analyzed outcomes after HLA-haploidentical related donor (n = 249) and umbilical cord blood (n = 118) transplantations in African American patients with hematologic malignancy between 2008 and 2016. The predominant disease was acute myelogenous leukemia for recipients of both types of donor grafts. The incidences of grade II-IV and III-IV acute graft-versus-host disease were higher after umbilical cord blood transplantation compared with HLA-haploidentical relative transplantation (56% and 29%, respectively, versus 33% and 11%, respectively; P

Chimeric antigen receptor T-cell(CAR-T) therapy is an increasingly utilized treatment modality with FDA approval for relapsed or refractory(R/R) CD19 positive B-cell Acute Lymphoblastic Leukemia(B-...

Hemophagocytic lymphohistiocytosis (HLH) is a disorder of immune regulation, manifested by fever, pancytopenia, hyperferritiniemia, hypertriglyceridemia, and extensive hemophagocytosis involving the bone marrow and spleen. HLH can occur in adults with an underlying hematopoietic malignancy, or with systemic infections. HLH following hematopoietic stem cell transplantation (HSCT) is unusual, and the diagnosis may be challenging particularly because the diagnostic criteria in the HLH-2004 guidelines overlap with common post-transplant complications such as engraftment syndrome, graft-vs-host disease, and infections. HLH is commonly triggered by viral, bacterial and, less commonly, parasitic infections. Following HSCT, patients with latent Toxoplasma infection may develop systemic disease secondary to reactivation, and rarely this may lead to a HLH physiology, with a very high mortality rate. Herein we describe the successful management of disseminated toxoplasmosis associated with life-threatening HLH using tocilizumab and antimicrobial therapy.

Background: Autologous stem cell transplantation (ASCT) in multiple myeloma (MM) has been shown to improve survival compared to conventional chemotherapy alone. However, the ability to perform ASCT relies, in part, on collecting a sufficient number (#) of CD34+ hematopoietic stem cells (HSCs), typically from peripheral blood. The ideal HSC mobilization regimen would enable collection of optimal #s of HSCs (5-6x10 6 CD34+ cells/kg) within the minimum # of apheresis sessions possible. Yet, despite currently available G-CSF (G) based mobilization regimens and multiple apheresis days, many remain unable to collect optimal #s of HSCs. Motixafortide (M) is a novel CXCR4 inhibitor, with high affinity (IC 50 0.54-4.5 nM) and long receptor occupancy (>48 hours). Methods: In this prospective, phase 3, double blind, placebo controlled, multicenter trial, 122 patients were randomized (2:1) to receive either M+G or placebo (P)+G for HSC mobilization prior to ASCT for MM. All patients received G (10 mcg/kg) on days 1-5 (and 6-8, if needed). Patients received either M (1.25 mg/kg, subcutaneous injection) or P on day 4 (and 6, if needed). Apheresis began day 5, with the primary (PEP) and secondary (SEP) endpoints of collecting ≥6x10 6 CD34+ cells/kg in up to 2 apheresis days or 1 day, respectively. Apheresis continued on days 6-8 if needed. Total CD34+ cells/kg were analyzed on site to determine if patients mobilized to the goal and all samples were subsequently sent for assessment by central laboratory. Patients that did not collect ≥2x10 6 CD34+ cells/kg by day 8 proceeded to rescue mobilization. The # of CD34+ cells infused was determined independently by each investigator according to local practice (minimum ≥2x10 6 CD34+ cells/kg). Analyses of the PEP/SEPs were performed on an intent-to-treat basis. Results: Demographics between the 2 treatment arms were similar. Mobilization with M+G resulted in 92.5% of patients collecting ≥6x10 6 CD34+ cells/kg within 2 apheresis days vs 26.2% with P+G (Odds Ratio (OR) 53.3, 95% CI 14.12-201.33, p Conclusions: A single injection of M on top of G significantly increased the proportion of patients mobilizing ≥6x10 6 CD34+ cells/kg for ASCT (92.5%) vs G (26.2%) in up to 2 apheresis days (p Figure 1 Figure 1. Disclosures Crees: BioLineRx Ltd.: Research Funding. Larson: TORL biotherapeutics: Current holder of individual stocks in a privately-held company; Bioline: Research Funding; Abbvie: Research Funding; BMS: Research Funding; Celgene: Research Funding; GSK: Research Funding; Janssen: Research Funding; Juno: Research Funding; Novartis: Research Funding; Pfizer: Research Funding; Takeda: Research Funding. Illés: Pfizer: Consultancy, Membership on an entity's Board of Directors or advisory committees; Janssen: Consultancy, Membership on an entity's Board of Directors or advisory committees; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees; Takeda: Consultancy, Membership on an entity's Board of Directors or advisory committees; Roche: Consultancy, Membership on an entity's Board of Directors or advisory committees; Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees. Stiff: Incyte: Research Funding; Cellectar: Research Funding; Seagen: Research Funding; Gamida Cell: Research Funding; Cellectar: Research Funding; Actinium: Research Funding; Bristol Myers Squibb: Research Funding; BioLineRX: Research Funding; Macrogenics: Research Funding; CRISPR Therapeutics: Consultancy, Honoraria; Amgen: Research Funding; Janssen: Research Funding; Kite, a Gilead Company: Research Funding; Karyopharm: Consultancy, Honoraria; MorphoSys: Consultancy, Honoraria. Sborov: Janssen: Consultancy, Membership on an entity's Board of Directors or advisory committees; GlaxoSmithKline: Consultancy; Sanofi: Consultancy; SkylineDx: Consultancy. Pereira: Jazz Pharmaceutical: Membership on an entity's Board of Directors or advisory committees. Mikala: Novartis: Consultancy; Takeda: Consultancy; Abbvie: Consultancy; Krka: Consultancy; Janssen: Consultancy; Amgen: Consultancy; Celgene: Consultancy. Holtick: Celgene: Honoraria; Sanofi: Honoraria. Qazilbash: Amgen: Research Funding; Oncopeptides: Other: Advisory Board; Bristol-Myers Squibb: Other: Advisory Board; Biolline: Research Funding; Angiocrine: Research Funding; NexImmune: Research Funding; Janssen: Research Funding. Hardy: American Gene Technologies, International: Membership on an entity's Board of Directors or advisory committees; Kite/Gilead: Membership on an entity's Board of Directors or advisory committees; InCyte: Membership on an entity's Board of Directors or advisory committees. Vainstein: BioLineRx LTD: Current Employment. Sorani: BioLineRx LTD: Current Employment. Gliko-Kabir: BioLineRx Ltd.: Current Employment. Goldstein: BioLineRx Ltd.: Current Employment. Kadosh: BioLineRx Ltd.: Current Employment.

Introduction: CD19 Chimeric Antigen Receptor T-cell (CAR-T) therapy is now a commonly used treatment for relapsed/refractory (R/R) Large B-cell Lymphoma (LBCL). However, predictors of long-term response remain poorly defined. In particular, partial response (PR) at first tumor assessment at Day 28 (D28) is a source of uncertainty both for clinicians and patients. In the pivotal CAR-T trials for LBCL, approximately half of these patients eventually achieved a complete remission (CR), while the other half experienced progressive disease (PD) (Neelapu et al, NEJM 2017). Herein, we present real-world data on 24 patients achieving a PR on D28 by PET/CT imaging following CAR-T therapy for R/R LBCL. We explore whether differences between baseline and D28 PET/CT imaging might predict progression free survival (PFS), overall survival (OS), best overall response rate (B-ORR), or last overall response rate (L-ORR). Methods: Out of 75 patients receiving CAR-T therapy at a single institution, we retrospectively identified and reviewed 24 (32%) as achieving a PR on D28. Two independent radiologists collected baseline (pre-CAR-T therapy) and D28 PET/CT Standard Uptake Value (SUV) max and Total Tumor Metabolic Volume (TMV, in cm 3) using ROVER software. The Intraclass Correlation Coefficients (ICC) as a measure of absolute agreement between two readers was 0.99 for SUV the 0.97 for TMV. There was a strong absolute agreement between the two radiologists. For simplicity of data interpretation and given this concordance we present the results of one reviewer. Univariable Cox regression model was used to calculate PFS and OS. All statistical tests were 2-sided and conducted at the 0.05 level of significance. Results: Of the 24 patients with PR on D28 PET/CT, median follow-up time was 1.9 years with 17 patients (71%) still alive at last follow-up (see Fig 1a). Median age was 51 years-old, 46% were female, 66.7% had stage III/IV disease, all patients had ECOG ≤2, 58% received bridging therapy, and half had ≥3 lines of prior therapy (see Table 1A). Results of the univariable Cox regression model revealed that a lower D28 SUV max (p=0.004), lower TMV at both baseline (p=0.03), and at D28 (p=0.01) may be predictive of better OS. Longer PFS was found with lower D28 SUV max (p=0.002) and lower TMV at both baseline (p=0.01), and D28 (p=0.04). In analysis of B-ORR achieved by PET/CT, half of patients in PR at D28 ultimately achieved a CR (see Table 1B). OS was significantly lower in those with a B-ORR of PR vs CR (p In analysis of outcome by L-ORR by PET/CT, 11 patients were in CR, while 13 had PD (see Table 1C). The median SUV max at baseline was 14 in those in CR vs 15 in PD (NS); at D28 median SUV max was 5 in those with CR vs 6 in PD (NS). The median baseline TMV was 298 in those with CR vs 591 in PD (NS); the median TMV at D28 was 15 in those with CR vs 21 in PD (NS). There was no significant difference in absolute or percent change between baseline and D28 of either SUV max or TMV based on L-ORR. Conclusion: In this analysis of patients in PR at D28 following CD19-directed CAR-T therapy, D28 but not baseline SUV max was significantly higher in those with a B-ORR of PR; and, in our modeling, lower D28 SUV max may predict favorable PFS and OS. Lower TMV, both at baseline and D28, may also be predictive of longer PFS and OS. Collectively, these findings suggest that for patients achieving a PR at D28, the best predictive factor by imaging for ultimately achieving a CR is lower SUV max at D28 and lower TMV at baseline and D28. These characteristics were also associated with longer PFS and OS. These findings indicate that there may be an intrinsic quality to the tumor itself (e.g. FDG-avidity and metabolic volume) that determines the ultimate outcome from a D28 PR. While further study is warranted, we demonstrate that patients with such characteristics should be identified, monitored closely for relapse, and perhaps be considered for further early intervention. Figure 1 Figure 1. Disclosures Hardy: InCyte: Membership on an entity's Board of Directors or advisory committees; Kite/Gilead: Membership on an entity's Board of Directors or advisory committees; American Gene Technologies, International: Membership on an entity's Board of Directors or advisory committees.

Background Despite prophylaxis, GVHD remains a significant cause of morbidity and nonrelapse mortality after allogeneic hematopoietic cell transplantation (HCT). ITA is a potent, selective Janus kinase (JAK) 1 inhibitor that has been combined safely with steroids in patients (pts) with acute GVHD. We describe results from a proof-of-concept study evaluating ITA + CNI-based regimens for GVHD prophylaxis. Study Design and Methods GRAVITAS-119 (NCT03320642) was a single-arm, open-label study enrolling pts aged ≥18 y undergoing allogeneic HCT using peripheral blood stem cells from 8/8 or 7/8 matched related or unrelated donors for a hematologic malignancy. Eligible pts were candidates for reduced-intensity conditioning with Karnofsky Performance Status ≥70%. Pts were excluded for prior HCT, JAK inhibitor therapy, or active uncontrolled infection. Pts received oral ITA 200 mg once daily (QD) beginning 3 d before HCT + tacrolimus (Tac)/methotrexate (MTX) or cyclosporine A (CSA)/mycophenolate mofetil (MMF) ± antithymocyte globulin (ATG) per institutional practice. ITA dose reduction/interruption was permitted for toxicity. ITA was reduced to 100 mg QD by Day 90 and discontinued by Day 180 unless pts required systemic GVHD treatment (tx), had malignancy relapse or unacceptable toxicity, or withdrew consent. The primary endpoint was Day 28 hematologic recovery (absolute neutrophil count [ANC] ≥500/mm3 for 3 consecutive measurements and platelets [plt] ≥20,000/mm3 with no transfusions in the preceding 3 d). Secondary endpoints included incidence of acute and chronic GVHD, GVHD- and relapse-free survival (GRFS), overall survival, and safety. Results Sixty-five pts were enrolled and treated with ITA + Tac/MTX (n=41; +ATG, n=8; no ATG, n=33) or ITA + CSA/MMF (n=24; +ATG, n=16; no ATG, n=8). Median (range) age was 65 (25-76) y, and 57% were male. The most common underlying malignancies were acute myeloid leukemia (40%) and myelodysplastic syndrome (26%). Disease risk index was classified as low, intermediate, and high in 11%, 66%, and 23% of pts, respectively. Pts received grafts from matched related (51%), matched unrelated (40%), or single-antigen mismatched unrelated (9%) donors. Busulfan/fludarabine (51%) and a fludarabine/melphalan reduced-intensity regimen (18%) were the most common conditioning regimens; 11% of regimens contained total body irradiation. Median (range) exposure to ITA was 140 (10-187) d; 74% received ITA for >90 d. All pts achieved hematologic recovery. Median (range) time to ANC and plt recovery among patients who had count nadir (ANC Conclusions Results from this small open-label trial in a heterogeneous pt population demonstrated that GVHD prophylaxis with ITA + CNI-based regimens was well tolerated and rates of severe acute GVHD were low. 1 pt with MF did not achieve ANC recovery on Day 28. An ITA + Tac + post-transplant cyclophosphamide cohort is currently being investigated in GRAVITAS-119. Disclosures Shah: Cell Vault: Research Funding; Celgene: Consultancy, Honoraria; Miltenyi Biotec: Honoraria, Research Funding; Kite Pharma: Consultancy, Honoraria; Incyte: Consultancy; TG Therapeutics: Consultancy; Verastim: Consultancy; Lily: Consultancy, Honoraria. Chevallier:Incyte Corporation: Honoraria. Rubio:Medac: Consultancy; MSD: Honoraria; Gilead: Honoraria; Neovii: Research Funding; Novartis: Honoraria. Schroeder:Astellas: Other; Dova Pharmaceuticals: Other; FlatIron Inc: Other; GSK: Other; Gilead Sciences Inc: Other; Novo Nordisk: Other; Genentech Inc: Research Funding; Merck: Consultancy, Honoraria, Speakers Bureau; Takeda: Consultancy, Honoraria, Speakers Bureau; Incyte Corporation: Other: served on advisory boards and received honoraria or consultant fees, Research Funding; Cellect Inc: Research Funding; Janssen: Research Funding; Partners Therapeutics: Other; Pfizer: Other; AbbVie: Consultancy, Honoraria, Speakers Bureau; Fortis: Research Funding; Seattle Genetics: Research Funding; Amgen: Other: served on advisory boards and received honoraria or consultant fees, Research Funding; Celgene: Research Funding; PBD Incorporated: Research Funding; Genzyme Sanofi: Other: served on advisory boards and received honoraria or consultant fees, Research Funding. Hardy:Incyte Corporation: Other: Advisory Board Member; Kite/Gilead: Other: Advisory Board Member; American Gene Technologies: Other: DSMB Member. Stiff:Kite, a Gilead Company: Research Funding; Amgen: Research Funding; Gamida Cell: Research Funding; Atara: Research Funding; Unum: Research Funding; Delta-Fly: Research Funding; Macrogenics: Research Funding. Solano:Incyte Corporation: Other: Received fees for an advisory role. Yakoub-Agha:Celgene: Honoraria; Novartis: Honoraria; Gilead/Kite: Honoraria, Other: travel support; Janssen: Honoraria; Jazz Pharmaceuticals: Honoraria. Rowley:AbbVie: Current equity holder in publicly-traded company; FATE Therapeutics: Consultancy. Duarte:Incyte Corporation: Other: Has received speaker and advisor fees. Morariu-Zamfir:Incyte Corporation: Current Employment, Current equity holder in publicly-traded company. Arbushites:Incyte Corporation: Current Employment, Current equity holder in publicly-traded company. Ding:Incyte Corporation: Current Employment, Current equity holder in publicly-traded company. Perales:Miltenyi Biotec: Research Funding; Kite/Gilead: Honoraria, Research Funding; Incyte Corporation: Honoraria, Research Funding; Nektar Therapeutics: Honoraria, Membership on an entity's Board of Directors or advisory committees; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees; Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees; Cidara Therapeutics: Other; Servier: Membership on an entity's Board of Directors or advisory committees, Other; NexImmune: Membership on an entity's Board of Directors or advisory committees; Medigene: Membership on an entity's Board of Directors or advisory committees, Other; Omeros: Honoraria, Membership on an entity's Board of Directors or advisory committees; MolMed: Membership on an entity's Board of Directors or advisory committees; Bellicum: Honoraria, Membership on an entity's Board of Directors or advisory committees; Abbvie: Honoraria, Membership on an entity's Board of Directors or advisory committees; Merck: Consultancy, Honoraria; Bristol Myers Squibb: Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene: Honoraria. OffLabel Disclosure: Itacitinib is a novel JAK1 inhibitor that has not been approved for use in acute GVHD or for any other indication.

Background: Nonmyeloablative (NMA) and reduced-intensity conditioning (RIC) regimens are offered for patients with hematologic malignancies requiring allogeneic stem cell transplantation (HSCT) but are not candidates for myeloablative conditioning (MAC). The intensity of the conditioning regimen (CR) is important and contributes to the ability of HSCT to provide a cure. There is no consensus regarding the best RIC regimen and efficacy is not equal amongst RIC regimens. The combination of 2 days of intravenous Busulfan (total of 6.4 mg/Kg) and Fludarabine (total of 120-160 mg/m2) (Flu/Bu2) has been validated and widely adopted. While this regimen is well tolerated, relapses are common and remain the leading cause of death. Total body irradiation (TBI) has been widely used in the CR and provides the advantage of potent anti-cancer effect, immunosuppression and the ability to reach certain 'sanctuary sites' for chemotherapy (i.e. CNS). The 2 most commonly used TBI levels are 1200 cGy in MAC regimens and 200 cGy in NMA and RIC regimens. We hypothesize that the addition of 400 cGy (200 cGy two fractions per day, 6 hours apart) TBI to Flu/Bu2 will reduce the relapse rate without increasing its toxicity. In this retrospective study, we compared the safety and efficacy of Flu/Bu2/TBI400 with Flu/Bu2 CR amongst a diverse group of hematologic diseases. Methods: From 2006 to 2018, 137 adult patients with different hematological diseases were treated using one of two RIC regimens, either Flu/Bu2/TBI400 or Flu/Bu2 followed by HSCT from HLA-matched related or unrelated donors. The primary endpoint was OS defined as the time from the date of transplant to death from any cause. The secondary endpoints included PFS, relapse rate, cumulative incidence of relapse (CIR), non-relapse mortality (NRM), causes of death, aGVHD, cGVHD and engraftment. PFS was defined as the time from the date of transplant to disease progression as documented by the treating physician, based on pathological, imaging or clinical findings of the individual disease, or death from any cause. NRM was defined as time of death without evidence of progressive disease with relapse or progressive disease as a competing risk event (data not shown in the abstract). Relapse was defined as progression or disease relapse with NRM as a competing risk event. These endpoints were censored at the time of last follow-up. Results: A total of 137 patients were included in this study. 74 patients were treated with Flu/Bu2/TBI400 and 63 patients were treated with Flu/Bu2. The 2 groups were comparable in terms of patient-, disease- and transplant-related characteristics; however, Flu/Bu2/TBI400 patients had a higher HCT-CI score and a lower KPS. CNI-MTX GVHD prophylaxis was used in a higher proportion in Flu/Bu2/TBI400. Most of the Flu/Bu2 transplants occurred from 2006 to 2012. The median age was 62 in both groups and patients had comparable disease type distribution and DRI (Table 1). The median follow-up time was 4.62 years. Flu/Bu2/TBI400 showed improvement of PFS over Flu/Bu2; the 5-year PFS was 50% in the TBI arm vs. 34% in the no-TBI arm (p=0.06 of marginal statistical significance). There was a numerical improvement of OS in favor of the TBI arm but this was not statistically significant; The 5-year OS was 53% with TBI vs. 39% without TBI (p=0.13). Cumulative incidence of relapse was not different between the 2 groups (p=0.29), see figures 1, 2 and 3. There was no difference in aGVHD incidence between the 2 groups (p=0.21). The TBI arm had significantly lower incidence of cGVHD compared to no-TBI arm (29% vs. 54%, p=0.005). Advanced DRI, grade III-IV aGVHD, cGVHD, use of ATG and MUD were associated with worse OS (univariate analysis). The same factors, with the exception of cGVHD, were associated with worse PFS. Multivariable Cox regression model revealed that grade III-IV aGVHD was associated with worse OS (p=0.001) while advanced DRI was associated with marginally inferior OS (p=0.07) (Table 2). Conclusion: This is the largest retrospective study of RIC Flu/Bu2/TBI400 regimen for HSCT with a median follow-up approaching 5 years. Our data suggests that RIC Flu/Bu2/TBI400 is safe and efficacious for different hematological malignancies. When compared to Bu/Flu2 without TBI, Flu/Bu2/TBI400 had lower incidence of cGVHD and showed a strong trend towards improved PFS and OS though not statistically significant at this time. Grade III-IV aGVHD was associated with poor OS in both groups. Disclosures Hardy: Incyte Corporation: Other: Advisory Board Member; Kite/Gilead: Other: Advisory Board Member; American Gene Technologies: Other: DSMB Member.

Introduction: Secondary hemophagocytic lymphohistiocytosis (HLH) is an aggressive life-threatening activation of the immune system triggered by an underlying condition. Use of chimeric antigen receptor therapy (CAR-T) to treat relapsed/refractory diffuse large B-cell lymphoma (R/R DLBCL) is associated with cytokine release syndrome (CRS), Immune Effector Cell Associated Neurotoxicity Syndrome (ICANS) and development of secondary HLH. Application of HLH scoring systems such as the H-score or HLH-2004 criteria to identify CAR-T triggered HLH is not validated in this setting. Inability to promptly recognize the development of secondary HLH in CAR-T patients and to distinguish it from CRS may lead to delay in HLH specific therapy and increased mortality. We analyzed the utility of applying the H-score and the HLH-2004 criteria to identify possible patients with HLH post-CAR-T for R/R DLBCL. Methods: A single center retrospective analysis of 75 patients with R/R DLBCL following CAR-T was performed. Using a peak ferritin of 500 mcg/L or higher within 30 days of CAR-T administration, 43 out of 75 patients were identified at risk for HLH. The H-score and HLH-2004 criteria were applied retrospectively. Measurement of NK activity was not available for any patients and soluble IL2 was collected intermittently. The mean H-score was calculated, and two sample t-test performed to evaluate for a difference in the mean H-score between low versus high grade CRS, low versus high grade ICANS, as well as presence versus absence of cytopenias at days 30, 90 and 180. Low grade CRS/ICANS was defined as 1, and high grade as 2 or higher. CRS was graded per Lee 2014 criteria and ICANS per CTCAEv.4. The 43 patients were then subdivided by H-score threshold of 169 into H-score Low (< 169) and H-score High (≥ 169). The threshold of 169 was used given a prior validation study showing optimal sensitivity and specificity for identifying acquired HLH in adult patients with an H-score equal to or higher than 169. Both Progression Free Survival (PFS) and Overall Survival (OS) were defined as time from CAR-T infusion until an event of last follow up. Kaplan-Meier curves were produced to describe the distribution of PFS and OS between two subpopulations of low and high H-Score. Results: Median peak ferritin was 1571.8 mcg/L (range: 375 mcg/L - >50,000 mcg/L, table 1). Median H-score was 135 (range 61 -250). Four patients were treated with HLH directed therapy receiving steroids with either tocilizumab, siltuximab and/or anakinra. Of these 4 patients, only 2 met five HLH-2004 criteria. All 4 patients had H-scores above 169 (209, 211, 228 and 250). Of these 4 patients, one died from complications thought secondary to HLH. Fourteen patients (14/43, 32%) had an H-score >169. Ten patients did not require any HLH directed therapy and had no clinical evidence of HLH. The mean H-score was not different between patients with low vs high grade CRS (148.2 vs 141.8, p=0.7) or low vs high grade ICANS (145.9 vs 142.6, p=0.8). No statistical correlation was seen between H-score and cytopenias at any time point. There was no significant difference in PFS or OS between the H-score low vs high subgroups (p=0.7, p=0.1 respectively, figure 1 and 2). Patients with higher H-score tended to have longer length of hospitalization for CAR-T (Pearson correlation coefficient 0.289). Conclusions: In patients with R/R DLBCL post CAR-T, the use of either the H-score or application of HLH-2004 criteria had low utility in identifying possible HLH in patients who screened in based on peak ferritin within 30 days of CAR-T administration. While apparent differences between the H-score high and low categories may not reach statistical significance due to the small number of patients, our exploratory analysis does not support the use of H-Score to evaluate for HLH post-CAR-T. The immediate post-CAR-T period is characterized by a high inflammatory state, which likely results in high H-scores. Results from our study suggest a need for further characterization of HLH following CAR-T and the role for a CAR-T specific HLH scoring system to distinguish secondary HLH from CAR-T related inflammation in this specific patient population. Disclosures Hardy: American Gene Technologies: Other: DSMB Member; Kite/Gilead: Other: Advisory Board Member; Incyte Corporation: Other: Advisory Board Member.

Background Most patients infected with Epstein-Barr virus (EBV) are asymptomatic, have nonspecific symptoms, or have self-limiting infectious mononucleosis. EBV, however, may result in severe primary disease or cancer. Methods We report EBV diseases associated with GATA2 deficiency at one institution and describe the hematology, virology, and cytokine findings. Results Seven patients with GATA2 deficiency developed severe EBV disease. Three presented with EBV infectious mononucleosis requiring hospitalization, 1 had chronic active EBV disease (B-cell type), 1 had EBV-associated hydroa vacciniforme-like lymphoma with hemophagocytic lymphohistiocytosis, and 2 had EBV-positive smooth muscle tumors. Four of the 7 patients had severe warts and 3 had disseminated nontuberculous mycobacterial infections. All of the patients had low numbers of monocytes, B cells, CD4 T cells, and natural killer cells. All had elevated levels of EBV in the blood; 2 of 3 patients tested had expression of the EBV major immediate-early gene in the blood indicative of active EBV lytic infection. Mean plasma levels of tumor necrosis factor α, interferon γ, and interferon gamma-induced protein 10 were higher in patients with GATA2 deficiency than in controls. Conclusions GATA2 is the first gene associated with EBV hydroa vacciniforme-like lymphoma. GATA2 deficiency should be considered in patients with severe primary EBV infection or EBV-associated cancer, especially in those with disseminated nontuberculous mycobacterial disease and warts.

Adults with relapsed or refractory (R/R) B-cell acute lymphoblastic leukemia (B-ALL) treated with conventional chemotherapy have dismal outcomes. Novel immunotherapies targeting CD19, including the bispecific T-cell engager blinatumomab and chimeric antigen-receptor T (CAR-T) cells, have revolutionized the treatment of R/R B-ALL. Robust response rates to CAR-T cell therapy after blinatumomab have recently been reported, but it is unknown whether blinatumomab can be effective following failure of anti-CD19 CAR-T cell therapy. Herein, we describe a patient with Philadelphia chromosome-positive B-ALL who relapsed after CD19-directed CAR-T therapy, but subsequently responded to the combination of blinatumomab and the tyrosine kinase inhibitor ponatinib, with the achievement of a complete remission lasting 12 months.

Introduction Relapse and graft failure continue to be 2 major problems after allogeneic HSCT. DLI and/or SCB are capable of inducing complete remission in relapsed disease. However, DLI and SCB are associated with significant risks such as graft versus host disease (GVHD) or aplasia. There is a paucity of information regarding DLI/SCB safety, efficacy and toxicity. A better understanding of the risks and benefits of DLI/SCB after HSCT is an important unmet need. Objectives Our objectives are to provide descriptive characteristics of patients receiving DLI or SCB and information regarding the provided cell therapy (CD3+ and/or CD34+ cell dose). We also aim to evaluate relapses, donor chimerism, graft failure, GVHD, DFS and OS after cellular therapy. Methods Retrospective chart review was completed on all patients who received either DLI or SCB at University of Maryland from 2005-2018. Data were analyzed using SPSS v.25.0, SAS v9.4, and R-software v3.5.1. Continuous variables were summarized as median (range), and categorical variables were presented using frequencies (%). Qualitative and quantitative differences between groups were analyzed by the chi-square and the Fisher's exact test for categorical and the Mann Whitney test for continuous variables. The Kaplan-Meier method was used to estimate the OS and GVHD-free survival with the corresponding 95% confidence interval (CI); the log-rank test was used to compare the survival probabilities for different patients' groups. Results A total of 65 patients underwent either DLI or SCB from 2005-2018. Of these, 38 received DLI, and 27 received SCB. Relapsed disease was the most common indication in 78.9% and 61.5% of DLI and SCB, respectively. The average CD3+/kg dose was 5.6 × 10^6 for DLI and 9 × 10^7 for SCB. Average CD34+/kg dose was 3.8 × 10^6 for SCB patients. One-year OS rate was 54.2% for DLI and 37.5% for SCB. Two-year OS rate of OS was 50.3% for DLI and 26.8% for SCB. Remission rates from relapsed disease were 43.4% for DLI and 31.3% for SCB. One-year GVHD-free survival following cell therapy was 51.2% for DLI and 34.4% for SCB. This dropped to 35.3% for DLI and 24.6% for SCB at two years. The differences seen in OS and GVHD between the 2 cohorts were not statistically significant. Conclusion Our overall survival data is favorable compared to recently published data. However, this comes at the expense of GVHD with long-term rates of GVHD-free survival measuring 25-35%. The use of unmanipulated cryopreserved SCB for relapse disease is underreported in the literature. We observed comparable long-term survival and GVHD in both cohorts. Cellular therapy with DLI or SCB remains a viable treatment modality with reasonable long-term outcomes for relapsed/refractory hematologic malignancies after allogeneic HSCT.

Introduction Treatment options for relapsed/refractory (R/R) diffuse large B-cell lymphoma (DLBCL) post-chimeric antigen receptor therapy (CAR-T) are limited. Here, we report the successful treatment of R/R DLBCL with programmed cell death 1 (PD1) inhibition post-allogeneic CAR-T. Case Report A previously healthy 26-year-old Caucasian man developed B-symptoms and cervical lymphadenopathy. Biopsy revealed DLBCL, activated B-cell subtype, double expressor and Ki-67 >80%. PET/CT scan revealed disease above and below the diaphragm. He achieved a partial response (PR) after R-CHOP, progressive disease (PD) after R-ICE, stable disease (SD) after R-ESHAP, and PD one month after autologous CD19-targeted CAR-T with CTL019 (CD3ζ/4-1BB). He then received R-lenalidomide (len) with radiation (24 Gy) to his mediastinal mass achieving a PR, followed by a myeloablative (Cy/TBI-12 Gy) allogeneic stem cell transplant (aSCT) from his 10/10 HLAmatched brother. He achieved 100% donor chimerism 30 days post-aSCT (D+30). Despite persistent full donor chimerism, D+60 PET/CT showed PD with confirmed relapse upon biopsy. Immunosuppression was discontinued, and ibrutinib with len was started, followed by donor lymphocyte infusion (DLI) which led to a mixed response. He then continued on ibrutinib with weekly temsirolimus and received a second DLI achieving a PR, with PD shortly thereafter. He next proceeded to allogeneic CAR-T with axicabtagene-ciloleucel (CD3ζ/CD28), complicated by grade 1 cytokine release syndrome without neurotoxicity. Three weeks post-CAR-T, he developed diplopia due to a cranial nerve palsy. Brain MRI showed new pontine T2 changes. Cerebrospinal fluid (CSF) was negative for lymphoma and infection, but notable for T-cell predominance. One month postCAR-T, PET/CT showed a complete metabolic response (CMR). Repeat brain MRI was unchanged. Two months later, he developed dizziness and intractable nausea, and repeat brain MRI showed a new lesion in the inferior cerebellar vermis, with resolution of previous pontine change. Evaluation of the CSF and peripheral blood revealed no CAR T-cell persistence, and PET/CT confirmed disease relapse in the cerebellum and mediastinum. Patient then received focal radiation (24 Gy) to his cerebellar lesion along with pembrolizumab 200 mg IV every 3 weeks, after which his neurologic symptoms resolved. MRI one day after radiation showed near-complete resolution of enhancing vermis lesion. After 3 cycles of pembrolizumab, PET/CT showed a CMR, with no active disease on brain MRI. Three months into PD1-inhibition therapy, his disease remains in CMR, without GVHD nor treatment-related toxicities. Conclusion This case illustrates the efficacy of allogeneic CAR-T after failure of autologous CAR-T and aSCT. Furthermore, PD1 inhibition can be used safely after allogeneic CAR-T, underscoring the need for prospective clinical studies.

Background: Cytokine release syndrome (CRS) and immune effector cell-associated neurotoxicity syndrome (ICANS) are known complications of chimeric antigen receptor T-cell (CAR-T) therapy. These clinical syndromes develop as a result of CAR-T activation, proliferation, and tumor lysis with resultant cytokine secretion. In prior reports of CD19 CAR-T therapy patients, those who developed ICANS showed evidence of endothelial activation and disruption of the blood-brain barrier as a result of cytokine release while only approximately one-third demonstrated changes on Brain MRI (Gust et al. Cancer Discov 2017). As such, further predictive markers and studies are needed to identify patients at risk for ICANS to allow for expedited management and improved outcomes. Herein we report a single-center analysis exploring glycolytic activity on PET/CT and the association with clinical outcomes for patients with relapsed/refractory diffuse large B-cell lymphoma (R/R DLBCL) after CAR-T therapy. Methods: An organ-based evaluation of uninvolved sites was conducted in R/R DLBCL patients (n=32) who underwent CD19 CAR-T therapy with evaluable PET/CT imaging at baseline immediately prior to CAR-T therapy and at 30 days post-infusion (D+30). All patients in this analysis were treated with axicabtagene ciloleucel as standard of care therapy after 2 or more lines of therapy. Tumor metabolic volume (TMV) and mean standard uptake value (SUVmean) of various organs were quantified using ROVER [Region of interest (ROI) visualization, evolution, and image registration] software (ABX advanced biochemical compounds GmbH, Radeberg, Germany). Statistical analysis was completed using STATA 14 (StataCorp. 2015. Stata Statistical Software: Release 14. College Station, TX: StataCorp LP). All tests were performed after testing the normality distribution assumption. Temporal changes were assessed using paired t-tests, and between-group analyses were completed with two-sample t-tests. Results: SUVmean increased significantly after CAR-T therapy in the following organs (D+30 v baseline pre-CAR-T PET/CT): cerebral cortex (8.23 v 7.09, p=0.036), cerebellum (6.26 v 5.56, p=0.024), basal ganglia (9.22 v 7.61, p=0.005), parotid gland (1.61 v 1.42, p=0.004), liver (2.47 v 2.17, p=0.002), spleen (2.08 v 1.84, p=0.043), and pancreas (1.76 v 1.48, p Conclusion: For patients with R/R DLBCL undergoing CD19 CAR-T therapy, significantly increased CNS glycolytic activity is seen on PET/CT at D+30 post-infusion when compared to baseline. Interestingly, these changes do not correlate with development of ICANS or lymphoma response; however, changes in cortical activity were associated with CRS grade ≥2. Overall, our findings illustrate a functional and radiographic link between cytokine release and subsequent disruption of the blood-brain barrier as quantified by increased cortical glycolysis 30 days post-CAR-T therapy. While findings are limited by small sample size, further validation in a larger data set is warranted. Disclosures Hutnick: Kite/Gilead: Other: Yescarta Speakers Bureau, Speakers Bureau. Badros:Celgene Corporation: Consultancy; Amgen: Consultancy.

7560 Background: Axicabtagene Ciloleucel (Axi-cel), an anti-CD19 CART cell therapy, achieved 58% complete response (CR) rate, in patients with relapsed refractory (r/r) LBCL on the ZUMA-1 study (Neelapu, NEJM 2017). Early response assessment (PET-CT) at day 30 is a common clinical practice. Patients with partial response (PR) at day 30 pose a therapeutic dilemma. ZUMA-1 analysis showed 1/3rd PR patients would convert to a CR. No biomarkers exist to predict eventual response. We report comprehensive PET-CT biomarker analysis on patients with PR at day 30 treated with Axi-cel for r/r LBCL. Methods: Ten patients with PR based on PET-CT imaging at day 30 were retrospectively assessed. Day 30 PET-CT was compared to baseline and a day 90 PET-CT. Global burden of disease of each patient at every time-point were quantified using Total Tumor Glycolysis (TTG) methodology as the imaging biomarker. Using adaptive-thresholding method, each lesion on FDG PET image was segmented and the following parameters were quantified: metabolic-volume (MV), SUVmax, SUVpeak, Partial-Volume-Corrected SUVmean and five other imaging biomarkers. To evaluate the effect of baseline and early imaging biomarkers to predict the subsequent burden of disease multiple regression analysis was performed (STATA 15). Results: Day 90 PET-CT assessment revealed, 4 patients had progressive disease (PD), 4 had CR, and 2 had PR. TTG of patients with PD at day 90 was 900 vs. 29 in patients with non-PD (CR, PR). The Global-SUVmean of the patients with PD at day 90 was 725 vs. 86 in patient with non-PD. Regression analysis showed early-TTG as a significant predictor of subsequent-TTG (beta-coefficient = 1.26 (0.39-2.13); P-value = 0.02; adjusted-R-squared = 0.97), while the baseline-TTG didn’t have any effect on subsequent-TTG (P-value = 0.3). Additionally, the regression analysis didn’t show any significant predictive value in SUVmean and SUVmax of baseline and day 30 scans to predict subsequent burden of disease (TTG or Global-SUVmean) with P-values > 0.8. Conclusions: Early post-axi-cel TTG, rather than baseline, can predict subsequent response to treatment. None of the SUV indices, commonly used in daily practice, were predictive of eventual response.

Introduction Toxoplasmosis is a well-known intracellular protozoan parasite with seroprevalence varying geographically. Relatively asymptomatic in healthy individuals, it's reactivation can be a devastating opportunistic infection in HSCT patients with rare documentation of associated HLH. Case A 25-year-old woman with Hodgkin lymphoma, refractory to multiple chemotherapies, autologous transplant and Nivolumab, who underwent haploidentical HSCT, was admitted on day +33 with persistent high-grade fevers. Blood counts were unremarkable, except for eosinophilia. She received broad spectrum antibiotics. PET/CT on day +36 demonstrated resolution of metabolic activity in multiple lymph nodes, but revealed ‘revved-up' bone marrow(Image 1). CT-chest (day +41) demonstrated widespread centrilobular nodules. Blood, urine, enteric cultures, HIV, Histoplasma studies, and respiratory viral panel PCR were negative. Pre-transplant serologies noted a positive toxoplasma IgG. Toxoplasma DNA was detected in blood on day +41; she received clindamycin, pyrimethamine, and atovaquone due to sulfa allergy but successfully underwent rapid sulfa desensitization. She developed progressive pancytopenia and hypoxemia (day +43) requiring intubation in the ICU. Ferritin was >50,000 ng/mL, and triglycerides 931 mg/dL. Bone marrow biopsy showed activated macrophages and hemophagocytosis (Image 2). She met 6/8 criteria described in HLH-2004 trial. She received dexamethasone and tocilizumab for HLH, leading to prompt reversal of HLH physiology within 72 hours of HLH-directed therapy initiation. She was extubated on day +48. She was discharged on sulfadiazine and pyrimethamine (day +60) with almost normal ferritin levels and transfusion-independency. Discussion HLH is characterized by cytopenias, extreme systemic inflammatory response, and high mortality. HLH can be triggered by infections, such as toxoplasmosis. Disseminated toxoplasmosis has a high mortality itself (>60 % treated, and 99% untreated), and HSCT recipients appear to have the highest risk. Early detection and treatment of the underlying infection is essential. Novel drugs, such as Tocilizumab, should be prospectively studied in HLH. In conclusion, HLH after HSCT should be suspected in cases of unexplained inflammatory response and cytopenias after successful engraftment; secondary causes must be explored and promptly treated.

New treatments are needed for B-cell malignancies persisting after allogeneic hematopoietic stem cell transplantation (alloHSCT). We conducted a clinical trial of allogeneic T cells genetically modified to express a chimeric antigen receptor (CAR) targeting the B-cell antigen CD19. T cells for genetic modification were obtained from each patient's alloHSCT donor. All patients had malignancy that persisted after alloHSCT and standard donor lymphocyte infusions (DLIs). Patients did not receive chemotherapy prior to the CAR T-cell infusions and were not lymphocyte depleted at the time of the infusions. The 10 treated patients received a single infusion of allogeneic anti-CD19-CAR T cells. Three patients had regressions of their malignancies. One patient with chronic lymphocytic leukemia (CLL) obtained an ongoing complete remission after treatment with allogeneic anti-CD19-CAR T cells, another CLL patient had tumor lysis syndrome as his leukemia dramatically regressed, and a patient with mantle cell lymphoma obtained an ongoing partial remission. None of the 10 patients developed graft-versus-host disease (GVHD). Toxicities included transient hypotension and fever. We detected cells containing the anti-CD19-CAR gene in the blood of 8 of 10 patients. These results show for the first time that donor-derived allogeneic anti-CD19-CAR T cells can cause regression of B-cell malignancies resistant to standard DLIs without causing GVHD.

Major clinical response to nivolumab in relapsed/refractory Hodgkin lymphoma after allogeneic stem cell transplantation

A 25-year-old female with a history of Ewing sarcoma presented with leukopenia (920/μL), neutropenia (180/μL), thrombocytopenia (147,000/μL) and macrocytic anemia (hemoglobin 12.2 g/dL, mean corpuscular volume (MCV) 90.3 fL). Metastatic Ewing sarcoma of the right gluteal muscle with pulmonary metastases had been diagnosed 7 years previously. Prior treatment had included chemotherapy, radiation therapy, and allogeneic hematopoietic stem cell transplantation (alloHSCT).

Background: Chimeric antigen receptor T-cell (CAR-T) therapy is an FDA-approved therapy for relapsed or refractory diffuse large B-cell lymphoma (DLBCL) and acute lymphoblastic leukemia (ALL). A common side effect of CAR-T therapy is cytokine release syndrome (CRS), and its severity ranges from mild to severe, and occasionally resulting in death. Patients at particularly high risk for severe CRS may benefit from earlier supportive care and rescue therapies, such as tocilizumab. Although the median onset of CRS has been reported as two days, no existing prognostic tools adequately assist the bedside clinician with triaging which patients will decompensate and warrant escalation of care. For example, biomarkers such as CRP and ferritin are ineffective in predicting CRS severity. Evaluation of the sublingual microcirculation of patients receiving CAR-T therapy may serve as a valuable surveillance tool. The sublingual microcirculation (defined as blood vessels Methods: Video images are collected in real time. Prior to interpretation, all video clips were assessed for quality based on the current microcirculation consensus document. Each acceptable clip was then analyzed by using two point-of-care (POC) scoring systems: 1) the microvascular flow index (MFI) and 2) the point-of-care microcirculation (POEM) score. The MFI is determined by dividing the video monitor into four equal quadrants and grading the overall flow of each quadrant with a score from 0-3 (0 = no flow; 1 = intermittent flow; 2 = sluggish flow; 3 = normal flow). The POEM score utilizes an ordinal 1-5 scale (1 = critically impaired; 2 = impaired; 3 = normal with marked heterogeneity; 4 = normal with mild heterogeneity; 5 = normal) that is a composite of four measurements assessing flow impairment and heterogeneity. For each enrolled patient, a baseline measurement was made immediately prior to CAR-T cell infusion with follow up measurements occurring every six hours beginning at hour 18 after cell infusion until hour 72. After hour 72, measurements were made daily until they were deemed no longer at risk for CRS. Results: At this time there is mature data on 7 patients. All patients received Axicabtagene Ciloleucel- a CD19 directed CAR-T cell therapy (Yescarta, Kite Pharma). All patients had normal baseline microcirculation (MFI > 2.6, POEM=5) and normal or near-normal microcirculation at the end of the study period. No patients developed severe CRS (grade 3 and above). Three patients developed grade 2 CRS that required tocilizumab. Patients #1 and #2 both had significant microcirculatory impairments ≥12 hours prior to developing symptoms severe enough to warrant tocilizumab. Patient #3 had normal microcirculation through the first four days of therapy and developed hypotension on day six. We captured a subtle change from a normal MFI and POEM score to mild impairment with both scoring algorithms on day five, one day prior to clinical manifestations of decompensation. For logistical reasons, subsequent data were unable to be obtained. MFI and POEM scores for all patients are listed below in Table 1. The remaining four patients developed grade 1 CRS with associated mild microcirculatory changes. Conclusions: In this pilot study, POC microcirculatory assessments were successfully used to monitor patients undergoing CAR-T therapy. Patients with more severe CRS manifested lower MFI and POEM scores and maintained their nadir longer than those with milder CRS. Our data suggest that CAR-T patients developing CRS manifest early signs of sublingual microcirculatory dysfunction. Moreover, these microcirculatory defects present prior to the development of standard clinical abnormalities, such as macrocirculatory derangements. While further investigation is ongoing, this tool could be used for earlier identification of patients at risk for CRS in order to deliver earlier appropriate therapies, and ultimately to improve patient outcomes. Disclosures No relevant conflicts of interest to declare.

Background: A graft-versus-lymphoma effect against diffuse large B-cell lymphoma (DLBCL) is inferred by sustained relapse-free survival after allogeneic stem-cell transplantation; however, there are limited data on a direct graft-versus-lymphoma effect against DLBCL following immunotherapeutic intervention by either withdrawal of immunosuppression or donor lymphocyte infusion (DLI). Materials and methods: An analysis was carried out to determine whether a direct graft-versus-lymphoma effect exists against DLBCL. The analysis was restricted to patients with DLBCL, who were either not in complete remission at day +100 after allogeneic stem-cell transplantation or subsequently relapsed beyond this time point. Results: Fifteen patients were identified as either not in complete remission (n = 13) at their day +100 evaluation or subsequently relapsed (n = 2) and were assessed for subsequent responses after withdrawal of immunosuppression or DLI. Eleven patients were treated with either withdrawal of immunosuppression (n = 10) or a DLI (n = 1) alone; four patients received chemotherapy with DLI to reduce tumor bulk. Nine (60%) patients subsequently responded (complete = 8, partial = 1). Six responses occurred after withdrawal of immunosuppression alone. Six patients are alive (range 42–83+ months) in complete remission without further treatment. Conclusion: The demonstration of sustained complete remission following immunotherapeutic intervention provides direct evidence of a graft-versus-lymphoma effect against DLBCL.

Monoclonal B-cell lymphocytosis (MBL) is a recently described laboratory finding in otherwise healthy individuals. In MBL, a light chain-restricted, clonal B-cell population, often with a chronic lymphocytic leukaemia (CLL) phenotype, is identified by flow cytometry. Although the prognostic significance remains unclear, there is an increased incidence in ageing populations and those with a family history of CLL. During the past decade of MBL study, three families have come to our attention in which prospective sibling haematopoietic stem cell donors were found to have an MBL. These families raise complex bioethical issues with regard to disclosure of research data, eligibility for clinical trials and potential donor transfer of MBL. These issues are explored in this report. Identification of MBL among prospective sibling transplant donors will become a common occurrence in transplant practice as transplantation is increasingly offered to older individuals and those with CLL.

Purpose: We hypothesized that lymphoid-selective host conditioning and subsequent adoptive transfer of sirolimus-resistant allogeneic T cells (T-Rapa), when combined with high-dose sirolimus drug therapy in vivo, would safely achieve antitumor effects while avoiding GVHD. Experimental Design: Patients (n = 10) with metastatic renal cell carcinoma (RCC) were accrued because this disease is relatively refractory to high-dose conditioning yet may respond to high-dose sirolimus. A 21-day outpatient regimen of weekly pentostatin (P; 4 mg/m2/dose) combined with daily, dose-adjusted cyclophosphamide (C; ≤200 mg/d) was designed to deplete and suppress host T cells. After PC conditioning, patients received matched sibling, T-cell–replete peripheral blood stem cell allografts, and high-dose sirolimus (serum trough target, 20–30 ng/mL). To augment graft-versus-tumor (GVT) effects, multiple T-Rapa donor lymphocyte infusions (DLI) were administered (days 0, 14, and 45 posttransplant), and sirolimus was discontinued early (day 60 posttransplant). Results: PC conditioning depleted host T cells without neutropenia or infection and facilitated donor engraftment (10 of 10 cases). High-dose sirolimus therapy inhibited multiple T-Rapa DLI, as evidenced by stable mixed donor/host chimerism. No antitumor responses were detected by RECIST criteria and no significant classical acute GVHD was observed. Conclusions: Immune-selective PC conditioning represents a new approach to safely achieve alloengraftment without neutropenia. However, allogeneic T cells generated ex vivo in sirolimus are not resistant to the tolerance-inducing effects of in vivo sirolimus drug therapy, thereby cautioning against use of this intervention in patients with refractory cancer. Clin Cancer Res; 21(19); 4312–20. ©2015 AACR.

Despite recent therapeutic advances, multiple myeloma (MM) remains largely incurable. Herein we report results of a phase I/II trial to evaluate the safety and activity of autologous T-cells engineered to express an affinity-enhanced T-cell receptor (TCR) recognizing a naturally processed peptide shared by the cancer-testis antigens NY-ESO-1 and LAGE-1. Twenty patients with antigen-positive MM received an average 2.4×109 engineered T cells two days after autologous stem cell transplant (ASCT). Infusions were well-tolerated without clinically apparent cytokine release syndrome, despite high IL-6 levels. Engineered T-cells expanded, persisted, trafficked to marrow and exhibited a cytotoxic phenotype. Persistence of engineered T cells in blood was inversely associated with NY-ESO-1 levels in the marrow. Disease progression was associated with loss of T cell persistence or antigen escape, consistent with the expected mechanism of action of the transferred T cells. Encouraging clinical responses were observed in 16 of 20 patients (80%) with advanced disease, with a median progression free survival of 19.1 months. NY-ESO-1/LAGE-1 TCR-engineered T-cells were safe, trafficked to marrow and showed extended persistence that correlated with clinical activity against antigen-positive myeloma.

TPS3096 Background: Non-small cell lung cancer (NSCLC) accounts for 84% of lung cancer. Survival has recently been impacted by molecularly targeted therapies and checkpoint inhibitors (CPI), and the promising CPI results implicate a role for the immune system in NSCLC. 10-40% of NSCLC express NY-ESO-1 or MAGE-A10 cancer/testis antigens. These studies will evaluate the safety and antitumor activity of genetically engineered affinity enhanced TCRs (NY-ESO-1c259T or MAGE-A10c796T) directed towards a NYESO-1 or MAGE-A10 derived peptides complexed with HLA-A*02. In addition, correlative studies to evaluate persistence, phenotype, functionality of engineered T cells, mechanisms of resistance and antigen spreading will be performed. Methods: Patients (pt) are screened (NCT02636855) to identify those who have the relevant HLA-A*02 alleles and NY-ESO-1 or MAGE-A10 tumor expression. For entry into either treatment protocol, pt must have Stage IIIb or IV NSCLC, have failed at least one platinum-containing regimen (may have received CPIs), have measurable disease, ECOG 0-1, adequate organ function, and be without brain metastases, history of severe autoimmune disease or current uncontrolled illness. Following apheresis, T cells are isolated and expanded with CD3/CD28 beads, transduced with a lentiviral vector containing the NY-ESO-1c259T or MAGE-A10c795 TCR, and infused into the pt following lymphodepleting chemotherapy with fludarabine and cyclophosphamide. The NY-ESO-1c259T study is a 10 pt study utilizing a dose of 1-6 x 109 transduced T cells. The MAGE-A10c796T first-in-human study is a modified 3+3 design in up to 28 pt with escalating doses of 0.1, 1.0 and 1-6 x 109 transduced T cells, with staggered treatments to allow for safety review; dose escalation will be guided by the DLT observed and by safety review committee guidance. Response to treatment will be assessed by RECIST v1.1 at weeks 4, 8, 16, 24, every 3 months (for 2 yr) and every 6 months until disease progression. Clinical trial information: NCT02588612/NCT02592577.

Rationale Despite the responsiveness of metastatic breast cancer (MBC) to available therapies, the prognosis for patients with MBC that fails to respond or progresses after first-line therapy for metastatic disease is poor and points to the need for new treatments in this clinical setting. High-dose chemotherapy with autologous stem cell rescue has achieved disappointing results when compared with conventional therapy. In contrast, immunotherapy using allogeneic hematopoietic stem cell transplantation (alloHSCT), which has achieved some success in the treatment of other solid tumors (eg, renal cell carcinoma), might offer a new therapeutic approach for advanced-stage MBC. Indeed, initial reports of efficacy using a full, myeloablative transplantation were encouraging.1,2 Pitfalls to the tolerability of alloHSCT include the intensity of high-dose preparative regimens, which are particularly challenging for patients who have received extensive chemotherapy for metastatic disease, and the development of graft-versus-host disease (GVHD). The development of less toxic preparative regimens, based on the observation that much of the therapeutic effect of allogeneic transplantation is mediated by the donor immune system (graft-versus-tumor [GVT] effects) rather than the cytotoxic chemotherapy that was traditionally given, has resulted in a more favorable therapeutic index.3

In the National Cancer Institute's Second Workshop on the Biology, Prevention, and Treatment of Relapse after Hematopoietic Stem Cell Transplantation, the Scientific/Educational Session on the Biology of Relapse discussed recent advances in understanding some of the host-, disease-, and transplantation-related contributions to relapse, emphasizing concepts with potential therapeutic implications. Relapse after hematopoietic stem cell transplantation (HSCT) represents tumor escape, from the cytotoxic effects of the conditioning regimen and from immunologic control mediated by reconstituted lymphocyte populations. Factors influencing the biology of the therapeutic graft-versus-malignancy (GVM) effect—and relapse—include conditioning regimen effects on lymphocyte populations and homeostasis, immunologic niches, and the tumor microenvironment; reconstitution of lymphocyte populations and establishment of functional immune competence; and genetic heterogeneity within the malignancy defining potential for clonal escape. Recent developments in T cell and natural killer cell homeostasis and reconstitution are reviewed, with implications for prevention and treatment of relapse, as is the application of modern genome sequencing to defining the biologic basis of GVM, clonal escape, and relapse after HSCT.

Immune escape from graft-versus-tumor (GVT) contributes to relapse after allogeneic stem cell transplantation (SCT). High-dose radiation (XRT) mobilizes a tumor-specific immune response following direct damage to the tumor and microenvironment. Radiation's abscopal effect is also immune mediated. We hypothesized that local radiation of relapsed tumor would rekindle a GVT effect and yield abscopal tumor responses. We tested the safety and systemic effects of single-fraction XRT followed by donor lymphocyte infusion (DLI) in patients with lymphoid malignancy and refractory relapse after SCT. Eligible subjects (Table) had tumor progression following donor engraftment, withdrawal of immune suppression and/or DLI, and XRT-amenable tumor. Subjects received 8 Gy XRT to 1 or more tumors; all but 1 (with chronic GVHD) received DLI 24 hours later. Clinical monitoring included marrow function, GVHD, XRT toxicity and tumor response. Correlative monitoring for systemic immunologic and GVT effects included FDG-PET imaging, serial peripheral blood sampling, and biopsy of radiated and nonirradiated tumor. Immune effects were characterized by flow cytometry and gene expression analysis. Local XRT toxicity of Grade 3 or less presented as expected in all subjects. Grade 4 neutropenia (2) was transient and GCSF-responsive; GVHD flare was not observed. Unexpected toxicity was observed in 1 subject who developed Grade 4 diffuse alveolar hemorrhage and Grade 3 cardiomyopathy that responded to therapy. Sustained response in radiated sites was observed in 6 of 8 evaluable subjects (nonevaluable: 1 MM bony lesion; 1 subject received further Rx). RECIST responses outside the radiation field included 2 PR and 5 SD. 2 subjects with SD had regression after initial tumor flare. 3 of 4 regressions were transient, with progression by 6 months; 3 subjects demonstrated progression. A single subject who received radiation alone demonstrated systemic tumor response as well as improvement in chronic GVHD (sclerotic skin). By FDG-PET, all subjects' radiated tumors showed substantially decreased uptake at D28; SUV changes were variable at D7. Changes in non-XRT tumors demonstrated far greater variability, even within single subjects. Consistent with systemic immune activation resulting from radiation-DLI therapy, within 1 week, peripheral blood T cell proliferation (%Ki-67+) increased significantly in CD4 and CD8 T cells, as well as FoxP3+ Tregs (Wilcoxon paired nonparametric analyses; p =.004, .004 and .01, respectively). A trend (p=.078) toward increased frequency of Th1 effector CD4 cells (T-bet+CD28-) was also observed. Comparison of gene expression in nonirradiated (abscopal) tumor in 4 patients collected pre and 1 month post XRT was consistent with an IFN-mediated response to cell damage. Genes were upregulated for receptors for nuclear materials released by damaged cells (TLR2, TLR4, CLEC4E), high- and low- affinity FcgR (FCGR1A and FCGR2A) used for phagocytosis, and an annexin receptor for phagocytic cells (FPR2). The inflammasome component genes NLRP3 and CASP1 were upregulated, as was IFIT1, a Type 1 IFN inducible gene. After SCT, XRT results in local tumor regression; abscopal responses were also observed, with systemic immune responses suggested by T cell proliferation in the peripheral blood and upregulation of tissue damage receptors and IFN-inducible genes in nonirradiated tumor. Systemic tumor responses were delayed, with peak regression occurring 3-4 months after XRT, consistent with an immune-mediated effect. GVHD was not observed; significant, reversible pulmonary and marrow toxicities were infrequent. Transient abscopal responses in these DLI-refractory patients suggest plausible synergy between radiation and allogeneic GVT effects. Further investigation into posttransplant immunomodulatory radiation is warranted. Funding: Intramural NCI/CCR and NCI Contract No. HHSN261200800001E Table 1. DX Age/Sex Years Post-Allo XRT Site Donor / DLI CD3 Dose (10e6) XRT Response NonXRT Response NonXRT Response Duration CLL 65/M 2.3 B Neck, L Groin URD/1 -90% -69% 2M HL 36/M 2.8 B Axillae MRD/10 -6% +51% CLL 64/M 1.4 R Axilla URD/1 -82% -19% 3M HL 37/M 7.0 R Axilla MRD/10 -69% +2% 4M MM 60/F 6.9 R Ileum MRD/10 NE PD - HL 25/F 1.2 Lumbar 3-5 URD/1 7% -69% 3M HL 37/F 5.8 R Neck MRD/10 -100% -30% 3M HL 27/M 2.7 L Pelvis MRD/10 NE NE - MCL 57/M 3.1 L Groin URD/1 -100% +28% HL 28/M 1.8 L Neck MRD/None -73% -9% 3M Disclosures No relevant conflicts of interest to declare.

Background: P is used in combination with G-CSF to improve the mobilization of peripheral blood hematopoietic stem cells in poor mobilizers. Limited data are available in regard to effects of P on post-transplant outcomes in comparison with non-P chemomobilized patients. Methods: In this retrospective study, we compare the engraftment and the outcomes of 34 patients mobilized with P + G-CSF or just-in-time rescue P in combination with chemotherapy and G-CSF to 143 patients (control group) mobilized with G-CSF with or without chemotherapy in lymphoma and myeloma patients who underwent ASCT between February 2012 and April 2014 at the University of Maryland Greenebaum Cancer Center. Post-transplantation outcomes including infections, hematologic recovery, relapse, progression and survival were recorded. Results: The median number of collected of CD34+ cells/Kg was 5.9 x 10(6) in the P group and 12.3 x 10(6) in the control group (p=0.0002). Median time to neutrophil engraftment (>0.5 × 10(9) /L) was comparable between the 2 groups: 12 days for the P group and 11 for the control group (p=0.28). There was a trend toward a shorter time to platelet engraftment (>20 × 10(9) /L) in the control (12 days) compared to the P group (14 days) (p=0.056). Progression-free survival at 1 year after (ASCT) was 88.2% in the P group and 81.8% in the control group. There was no difference in the overall survival of both groups (p=0.62) Conclusions: Short and long-term engraftment and outcomes after ASCT seem to be comparable in lymphoma and myeloma patients receiving plerixafor compared to chemomobilized patients without plerixafor. This observation support the use of plerixafor + G-CSF or just-in-time rescue P in patients who mobilize poorly without P. Figure 1. Figure 1. Disclosures No relevant conflicts of interest to declare.

BACKGROUND: Several recent studies have linked the interactions of programmed death 1 (PD-1) receptor and its ligand (PD-L1) to immunologic control of MM. Expression of PD-L1 on myeloma cells and the abundance of PD-1 on various bone marrow microenvironment components contribute to tumor-mediated immune suppression. We hypothesized that pembrolizumab, a PD-1-blocking antibody, will activate myeloma specific cytotoxic T cells that can be enhanced by pomalidomide in RRMM patients to induce clinical responses. METHODS: In this ongoing single arm, phase II study, 24 patients with RRMM received 28-day cycles of pembrolizumab (at a dose of 200 mg IV) every 2 weeks (in a run off phase, first 6 patients received 200 mg IV every 4 weeks) plus pomalidomide (4 mg daily x 21 days) and dexamethasone 40 mg weekly. Study objectives were measurements of safety and efficacy and assessment of the PD-1 and PD-L1 protein expression in bone marrow samples. RESULTS: The median age was 65 years (range: 41-75); 35% were African American and 71% were men. Of the 24 patients, 75% had prior autologous transplantation and 96% were refractory to last therapy. All patients had received both IMids and Proteosome inhibitors; 75% were double refractory to both IMids and Proteosome inhibitors and additional 21% were refractory to lenalidomide alone. Patients had received a median of 3 lines of prior therapy (range: 1-6). The median time from MM diagnosis to study entry was 4 years (range: 1.2-15). All patients had abnormal cytogenetics: most common were 1q+ (72%) and high-risk FISH (40%) [del 17p, t(4:14) and/or t(14:16)]. There were no infusion-related reactions. Hematologic toxicities (≥ grade 3) were neutropenia (29%), lymphopenia (17%) and thrombocytopenia (8%). Non-hematologic adverse events included (Grade ≤2; ≥3): fatigue (n=12; 1), constipation (n=10; 0), dyspnea (n=9; 2), itching (n=6; 0), muscle spasms (n=6; 0), infection (n=4; 3), hyperglycemia (n=5; 0), edema (n= 4; 0), fever (n=3; 0), palpitation (n=2; 1), rash (n=3; 1) and hypotension (n=3; 0). Events of clinical significance, autoimmune mediated, included hypothyroidism (n=2), transaminitis (n=2), and pneumonitis (n=1). Four patients had pomalidomide dose reductions due to rash, neutropenia, palpitations and fatigue. Two patients died; one after cycle 1 (progressive disease) and one during cycle 2 (sepsis). Objective responses (modified IMWG criteria) were observed in 11 of 22 evaluable patients (50%) including: near complete response (n=3), very good partial response (n=2), partial response (n=6); additionally, 3 patients had minimal response, 6 had stable disease and 2 progressed. At a median follow up of 16 weeks; 17 of 22 patients continued on the study. Reasons for discontinuation included disease progression (n= 4) and protocol violation (n=1). Analysis of pretreatment and post-treatment tumor specimens for PD-1 and PD-L1 is in progress. CONCLUSIONS: Pembrolizumab in combination with pomalidomide and dexamethasone has promising therapeutic activity and an acceptable safety profile in heavily treated RRMM patients. ClinicalTrials.gov number, NCT02289222. Disclosures Off Label Use: Pembrolizumab.

Background: The incidence of MM is 2 to 3 fold higher in blacks than in whites; they present at a younger age and have better overall survival. The biological bases for these disparities remain unclear. Outcome of MM is linked to cytogenetic and molecular changes, both primary (hyperdiploidy and heavy chain (IgH) translocations) and secondary (rearrangements of MYC, activating mutations of NRAS, KRAS or BRAF, and deletions of 17p). Methods: Cytogenomic alterations in consecutive MM patients were assessed using integration of metaphase chromosome analysis by GTG-banding and interphase fluorescence in situ hybridization (iFISH) in CD138-positive cells isolated from fresh BM samples using a protocol of magnetic-activated cell sorting. Changes evaluated included monosomy 13/del(13q), monosomy 17/del(17p), gain of 1q21, and rearrangements of the IGH gene including t(4;14), t(11;14) and t(14;16). Results: Samples from 218 consecutive MM patients were analyzed (Table 1). 108 were from black and 110 were from white patients. Median age for blacks was 59 years (range: 36 - 82) and for whites, 63 years (range: 39 - 83) (p=0.008). Fewer black men than whites were observed (46.3% versus 64.6%, p=0.007). Overall, blacks had fewer abnormal karyotypes compared to whites (18.1% versus 31.8%; p=0.02). Black patients had a lower frequency of non-hyperdiploid karyotypes (8.5% versus 20.6%; p=0.01) and had a trend toward lower frequencies of rearrangements of IGH (30.8% versus 43.5%; p=0.055) than white patients. Most notably, they had significantly lower frequencies of monosomy 17/del(17p) (5.6% versus 18.5%; p=0.003) and monosomy 13/del(13q) (28.9% versus 46.3%; p=0.008). After stratification by age (Figure 1), younger patients showed significantly higher frequencies of the monosomy 17/del(17p) abnormality (p=0.001) and the t(4;14) (p=0.04) than older patients, with the difference more significant in white patients. The associations among molecular cytogenetic abnormalities (Figure 2) showed a different association pattern for black and white patients. White patients with t(11;14) were more likely to have monosomy 13/del(13q) (p=0.003) and gain of 1q21 (p=0.02), while this association was not observed in black patients. Conclusion: Black MM patients had significantly different cytogenetic profiles detected by iFISH on CD-138 selected malignant cells, compared to whites. Black MM patients had a more favorable profile, including lower frequencies of non-hyperdiploid karyotype and of IGH rearrangements. This study supports a biological basis for previously described outcome disparities between black and white patients with MM. Further studies will focus on identifying specific molecular targets and their impact on therapy and on overall outcome. Table 1. Demographics and cytogenetic abnormalities of the MM patients Demographics Black White P-value# Total, n 108 110 Gender, n (%) =0.007* Male 50 (46.30%) 71 (64.55%) Female 58 (53.70%) 39 (35.45%) Age (median) 59 63 =0.008* Chromosome (karyotype) =0.022* Normal 86 (81.90%) 73 (68.22%) Abnormal 19 (18.10%) 34 (31.78%) Hyperdiploidy 8 (7.6%) 8 (7.4%) Non-hyperdiploidy 9 (8.5%) 22 (20.6%) =0.013* 11;14 translocation 2 (1.9%) 4 (3.7%) FISH abnormality -13/del(13q) 31 (28.97%) 50 (46.30%) =0.008* Gain of 1q21 35 (32.71%) 47 (43.52%) =0.103 -17/del(17p) 6 (5.61%) 20 (18.52%) =0.003* IGH rearrangements 33 (30.84%) 47 (43.52%) =0.055^ t(4;14) 7 (6.54%) 13 (12.38%) =0.146 t(11;14) 15 (20.55%) 15 (19.48%) =0.870 t(14;16) 2 (3.85%) 6 (10.71%) =0.175 others 16 (14.95%) 15 (13.89%) =0.824 *means statistical significant (p-value < 0.05), where ^ means marginal significant (0.05 < p-value < 0.10). #p-values come from the Cochran-Mantel-Haenszel tests for categorical variables, and t tests for continuous variables. Associations among eight molecular cytogenetic abnormalities. Each solid black line indicates one abnormality is statistically significantly associated with another abnormality. Figure 1. Distributions of cytogenetic abnormalities by age and race Figure 1. Distributions of cytogenetic abnormalities by age and race Figure 2. Relationship of various cytogenetic abnormalities in the MM patients Figure 2. Relationship of various cytogenetic abnormalities in the MM patients Disclosures No relevant conflicts of interest to declare.

Inflammatory breast cancer (IBC) is a rare clinicopathologic entity with a poor prognosis, lagging far behind any other form of nonmetastatic breast cancer. Since the advent of systemic chemotherapy over 35 years ago, only minimal progress has been made in long-term outcome. Although multiple randomized trials of high-dose chemotherapy and autologous progenitor cell transplantation (ASCT) for the treatment of breast cancer have yielded disappointing results, these data are not necessarily relevant to IBC, a distinct clinical and pathologic entity. Therefore, the optimal multimodality therapy for IBC is not well established, and remains unsatisfactory. We treated 21 women with nonmetastatic IBC with a multimodality strategy including high-dose melphalan (Mel)/etoposide and ASCT. The treatment was overall tolerated with acceptable morbidity, and no post-ASCT 100-day mortality. With a median potential follow-up of approximately 8 years, the estimated progression-free survival (PFS), event-free survival (EFS), and overall survival (OS) at 6 years from on-study date are: 67%, 55%, and 69%, respectively. These results from a small phase II study are among the most promising of mature outcome data for IBC. They strongly suggest, along with results of several already published phase II trials, that ASCT could play a significant role in the first line treatment of IBC.

Proceedings: AACR 106th Annual Meeting 2015; April 18-22, 2015; Philadelphia, PA Adoptive immunotherapy for cancer has been limited by a lack of antigen specificity, low levels of target expression, and failure to break self-tolerance. We hypothesized that infusion of genetically modified tumor-specific T cells following autologous stem cell transplant (ASCT) may overcome these barriers for multiple myeloma (MM). To test this, we conducted a phase I/II clinical trial ([NCT01352286][1]) in which T cells engineered with an HLA-A*0201 restricted, affinity-enhanced TCR recognizing NY-ESO-1 / LAGE-1 peptides (NY-ESOc259-T), were infused in the setting of profound lymphodepletion that accompanies high-dose chemotherapy given with ASCT. HLA-A*0201 MM patients eligible for ASCT, with antigen positive tumor were enrolled. NY-ESOc259-T was manufactured in a 10 day process using anti-CD3/CD28 microbeads and lentiviral vector, and was administered two days following ASCT. IMWG criteria were used to assess response at day 100 with the addition of a near complete response category (nCR) due to the common occurrence of oligoclonal banding observed following rapid post-ASCT immune reconstitution. Blood and marrow samples were taken at multiple timepoints for serum cytokine analysis, NY-ESOc259-T persistence and trafficking, multiparameter flow analysis to examine the phenotype and function of NY-ESOc259-T, and tumor biomarker analysis. 25 of 29 enrolled patients were infused. A mean of 2.8 × 109 engineered cells were administered (range 8.3 × 108-4.2 × 109), and the average transduction efficiency was 33% (range 30%-45%). Patients tended to have advanced disease (64% chromosomal abnormalities, and 24% prior ASCT). At 3 months, 67% (16/24) and 58% (14/24) of patients were in VGPR and nCR or better, respectively. Infusions were well-tolerated and no cytokine release syndrome was reported. NY-ESOc259-T persisted at 6 months in all but one patient, and in a subset of patients at 2 years; marrow infiltration was consistently observed from day 7 through day 180. NY-ESOc259-T initially displayed a dominant activated effector phenotype which converted towards a dominant effector memory phenotype by 1 year post infusion, in a pattern that mirrored clinical responses. Persisting cells demonstrated a polyfunctional response (IFN-γ and TNF-α) with a cytotoxic (CD107a and granzyme B) signature without overexpression of exhaustion markers (PD-1, LAG-3, and TIM-3). Tumor biomarker analysis is ongoing. MM relapse occurred in 13/25 patients. This data show that NY-ESOc259-T cells exhibit robust trafficking and expansion, durable persistence without exhaustion, and follow a natural immune expansion and contraction pattern consistent with an antigen-driven mechanism of action. Relapse correlated with a loss of persistence or tumor antigen escape, suggesting that targeting multiple antigens and maintenance infusions may increase durable remissions. Citation Format: Aaron Rapoport, Edward Stadtmauer, Luca Melchiori, Ryan Wong, Eduardo Davila, Gwendolyn Binder-Scholl, Tom Holdich, Dan Vogl, Brendan Weiss, Jeffrey Finkelstein, Simon Lacey, Sarah Bond, Marylene Fortin, Yoav Peretz, Joanna Brewer, Alan Bennett, Andrew Gerry, Nick Pumphrey, Helen Tayton-Martin, Lilliam Ribeiro, Ashraf Badros, Saul Yanovich, Nancy Hardy, Jean Yared, Naseem Kerr, Sunita Philip, Sandra Wesphal, Bruce L. Levine, Carl June, Michael Kalos, Bent Jakobsen. NY-ESO T cells administered post ASCT for MM exhibit extended functionality without exhaustion in a natural pattern of effector and memory programming. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4701. doi:10.1158/1538-7445.AM2015-4701 [1]: /lookup/external-ref?link_type=CLINTRIALGOV&access_num=NCT01352286&atom=%2Fcanres%2F75%2F15_Supplement%2F4701.atom

The curative potential of allogeneic hematopoietic stem cell transplantation in treating cancer is derived in large part from the donor immune system reacting against host or tumor cell antigens to generate a graft-vs-tumor (GVT) effect. Whereas early animal models suggested this allogeneic immune response, evidence for its role in human transplantation was not realized until the late 1970s and early 1980s, when the association between graft-vs-host disease and tumor response became clear. In this chapter, the animal and human data that established the GVT effect as the major therapeutic component of allogeneic hematopoietic stem cell transplantation are reviewed, and ongoing efforts to understand and build on GVT as a therapeutic modality for other tumor types are described. The current thinking on the biology of the effectors and modulators of GVT are discussed. The progress that has been made in clinical application of immunotherapy in the autologous setting and of solid tumor therapy in the allogeneic setting is reviewed. Finally, the potential for continued advances in the efficacy and safety of immunotherapy for cancer is explored, as reflected in recent and ongoing efforts to apply the growing understanding of alloreactivity toward fulfillment of the potential for targeted antitumor therapies.

471 Lymphoma progression remains an obstacle after allogeneic HCT, particularly after non-myeloablative conditioning in patients with high-risk histology (non-indolent; Kahl et al; Blood, 2007) and chemotherapy refractory disease (Bishop et al; Cancer, 2010). In murine models, rapamycin-resistant T cells favorably modulated the balance between GVHD, graft rejection, and GVT effects. To translate this, we conducted a multi-center phase II trial (NCT0074490) of T-Rapa cells infused as a pre-emptive DLI after low-intensity allogeneic HCT; here, we report overall outcome of patients with high-risk lymphoma diagnoses, many of whom were chemotherapy refractory. T-Rapa cells were manufactured by ex vivo culture of donor CD4+ T cells using CD3/CD28 co-stimulation and IL-4, IL-2, and rapamycin for 12-days (T-Rapa12) or 6-days (T-Rapa6), and administered (2.5 × 107 cells/kg) at d14 post-HCT. Both populations of T-Rapa cells expressed a mixed Th2/Th1 phenotype with minimal T-Reg content. Patients (n=42) received outpatient-intensity chemotherapy (typically, EPOCH-FR) until CD4 count was < 200 cells/μl, and then received an HLA-matched sibling mobilized allograft and GVHD prophylaxis of cyclosporine plus short-course sirolimus (to d14 post-HCT); conditioning consisted of fludarabine (120 mg/m2) and cyclophosphamide (1200 mg/m2). Table I details the high-risk diagnoses, pre-treatment history (median of 4 prior regimens), remission status at time of HCT (7/42 [17%] in CR), and presence of chemotherapy refractory disease (stable or progressive disease to prior therapy: 23/42 pts, 55%). T-Rapa cell infusion was relatively safe, with no engraftment syndrome or d100 TRM; incidences of grade II-IV acute, late acute, and classical chronic GVHD were 17%, 34%, and 36%, respectively. Initial mixed donor/host chimerism converted to predominate donor chimerism after T-Rapa cell DLI (Table I). Overall median survival probability at 24 months post-HCT is 85.7% for patients with chemotherapy sensitive disease vs. 39.1% for patients with chemotherapy refractory disease ([Fig. 1][1]; p=0.0008). All deaths were due to progressive disease except for 2 infection-related deaths at days 162 and 359 post-HCT; all surviving patients are in CR. Survival was not statistically significantly influenced by DLI type (T-Rapa12 vs. T-Rapa6) or histology-type (NHL vs. HD). Pre-emptive DLI using donor T-Rapa cells after low-intensity conditioning is safe and very effective in patients with high-risk lymphoma diagnoses and chemotherapy sensitive disease; for such patients, future randomized trials should compare low-intensity T-Rapa cell therapy to other transplantation regimens. For patients with high-risk lymphoma diagnoses and chemotherapy-refractory disease, we are evaluating a modification to the current platform that incorporates high-dose sirolimus therapy. | Patient Characteristics | Chimerism Results[c][2] | CD3 | CD15 | |:----------------------------------:| ----------------------- | ---------------------- | ------------------ | ----------- | | Number of Patients | n = 42 | Day 14 post-HCT | 57 (12-97) | 46 (8-94) | | Age (median, range) | 44 (23-68) | Day 28 post-HCT | 77 (37-100) | 76 (29-98) | | Sex (male/female) | (26/16) | | | | | # of Prior Therapies (mean, range) | 4 (1-6) | Day 100 post-HCT | 89 (51-100) | 93 (35-100) | | Histology[a][3] | n=26 total (62%) | Survival Results[d][4] | 24 Mo. Surv. Prob. | | NHL Category | n=12 | ChemoSens/T-R12 | 78.6% (n=7) | | DLBCL | n=5 | ChemoSens/T-R6 | 85.7% (n=12) | | DLBCL-tr | n=2 | ChemoRefr/T-R12 | 41.7% (n=11) | | DLBCL-EBV | n=3 | ChemoRefr/T-R6 | 36.4% (n=12) | | PlasmacytoidDC | n=3 | All NHL | 57.4% (n=26) | | T Cell | n=16 total (38%) | All HD/Grey Zone | 68.8% (n=16) | | HD Category | n=12 | | | | HD | n=4 | | | | Grey Zone | | | | | Chemo. Response[b][5] | 23/42 (55%) | | | | Refractory (SD/PD) | 19/42 (45%) | | | | Sensitive (PR/CR) | | | | | Complete Remission | 7/42 (17%) | | | | At Time of HCT | | | | * DLBCL, diffuse large B cell lymphoma; DLBCL-tr, transformed; DLBCL-EBV, Epstein Barr Virus related; Plasmacytoid DC, dendritic cell; HD, Hodgkins Disease; SD, stable disease; PD, progressive disease; PR/CR is partial or complete response. * [↵][6]a Grey Zone Lymphoma and Hodgkins Disease were pooled for statistical analyses. * [↵][7]b Chemotherapyresponse, as determined after last regimen prior to study entry. * [↵][8]c Chimerism determined by VNTR-PCR at days 14, 28, and 100 post-HCT (mean and range of values shown); CD3, T cell chimerism; CD15, myeloid cell chimerism. * [↵][9]d Survival by Kaplan-Meier analysis; 24 month median survival probability values shown; T-R12 and T-R6 indicates recipient of T-Rapa cells manufactured for 12 days vs. 6 days. Table I ![Figure][10] Disclosures: Levine: TxCell: Consultancy, Membership on an entity's Board of Directors or advisory committees; University of Pennsylvania: financial interest due to intellectual property and patents in the field of cell and gene therapy. Conflict of interest is managed in accordance with University of Pennsylvania policy and oversight, financial interest due to intellectual property and patents in the field of cell and gene therapy. Conflict of interest is managed in accordance with University of Pennsylvania policy and oversight Patents & Royalties. June: Novartis: Research Funding, institution owned patents have been licensed by Novartis, institution owned patents have been licensed by Novartis Patents & Royalties. Mato: Celgene, Milennium, Genentech, Seattle Genetics: Speakers Bureau. [1]: #F1 [2]: #fn-4 [3]: #fn-2 [4]: #fn-5 [5]: #fn-3 [6]: #xref-fn-2-1 [7]: #xref-fn-3-1 [8]: #xref-fn-4-1 [9]: #xref-fn-5-1 [10]: pending:yes

Abstract 683 Donor lymphocyte infusion (DLI) is the primary treatment for relapse after allogeneic hematopoietic stem cell transplantation (allotransplant), but is effective in less than half of patients and is associated with significant graft-vs-host disease (GVHD). Furthermore, DLI is not available for cord-blood or many unrelated-donor recipients. We theorized that tumor from patients relapsing post-allotransplant would contain infiltrating donor T- lymphocytes with tumor-specificity. If such cells had been “primed”, but inadequately costimulated for tumor cell killing, costimulation ex-vivo could generate a donor lymphocyte product with increased graft-vs-tumor (GVT) potency. Preclinical feasibility was demonstrated in tumor biopsies from patients with tumor progression after allotransplant. Ex-vivo CD3/CD28 costimulation of tumor-infiltrating lymphocytes with antibody-coated magnetic beads yielded donor products, predominently consisting of effector T-cells; tumor specimens of greater than 1 cm reliably produced donor T cell expansions that would permit clinically relevant cell dosing. Based on these preclinical results, we conducted a Phase 1 study of tumor-derived donor lymphocyte (TDL) therapy in allotransplant recipients with B-lymphoid tumor progression despite full-donor T cell chimerism and DLI, or for which DLI was not available. The primary objectives of (1) feasibility of ex-vivo costimulation of lymphocytes from surgically harvested tumor to generate a TDL product and (2) safety of TDL infusion (TDLI) in patients with relapse after allotransplant were met within the first 7 of 15 planned subjects. All 7 patients had chemotherapy-refractory relapse after allotransplant (diffuse large-B cell lymphoma (DLBCL) = 2; Hodgkin's Lymphoma (HL) = 4; chronic lymphocytic leukemia (CLL) = 1). Tumor was surgically resected. Lymphocytes were released from tumor tissue through mechanical dispersion and cultured with CD3/CD28 antibody-coated magnetic beads in media supplemented with IL-2 (100 IU/ml) for a median of 12 days (range: 7– 42 days). T cells comprised from 0.5 – 63.4% of tumor cell suspensions (culture inocula) and 82 – 99% of expanded products (22- to 144-fold expansion). PCR-based chimerism assessment of products demonstrated that the TDL were of donor origin (median 99% donor). During TDL expansion, markers of activation and effector function increased (CD4: CD40L; CD8: CD137, perforin, NKG2D). Percentages of FoxP3+ Treg cells declined and TBet+ Th1/Tc1 effectors increased in the costimulated TDL product. Expression of CD27 and CD28 has been associated with long-term persistence of infused effector T cells; although these markers declined in culture, expression was retained in a significant proportion of cells from the 5 products that were cultured for less than 14 days. TDL products meeting release criteria for tumor contamination ( Disclosures: June: N/A: Inventor, Government-held Patent.

Abstract 3451 Relapse is the major cause of treatment failure and death following reduced-intensity (RI) allogeneic hematopoietic stem cell transplantation (HSCT) for non-Hodgkin's lymphoma (NHL), yet there are no reports that focus specifically on the natural history of relapse in this patient population. We assessed relapse risks and outcomes on 120 consecutive patients (median age = 52 years; range, 28–71 years) with NHL (indolent = 43; aggressive = 77) who all received a T-cell replete allograft from HLA-matched siblings following a reduced-intensity conditioning regimen (fludarabine/cyclophosphamide). All patients were assessed for disease status at 1, 3, 6, 12, 18, 24 months post-transplant, and annually thereafter or as clinically indicated. Median event-free survival (EFS) from transplant date for all 120 patients was 11.3 months (range, 0.5–105.5+ months) with a 5-year EFS = 35%. Median EFS (months) was assessed for the following pre-transplant characteristics: chemo-resistant vs. chemo-sensitive = 3.3 vs. 39.1, p = 0.0001; pre-transplant disease status - CR vs. PR vs. SD vs. PD = not reached (NR) vs. NR vs. 11.2 vs. 1.7, p Disclosures: No relevant conflicts of interest to declare.

Allograft T cell depletion (TCD) reduces acute graft-vs. host disease (aGVHD) after myeloablative hematopoietic stem cell transplantation (HSCT). Lower incidences of aGVHD reported after reduced-intensity stem cell transplantation (RIST) may reflect delayed donor T cell engraftment. We compared the incidence of aGVHD following RIST with TCD (19 patients (pts) vs. T cell replete (TCR) allografts (20 pts)(Table). There was no difference in the incidence aGVHD, occurring in 71% of TCD recipients (median onset Day 47) and 70% of TCR recipients (median onset Day 25). After TCD, 100% of those who engrafted prior to any DLI developed aGVHD compared with 56% of those who engrafted after DLI, including two pts who developed “late-acute” aGVHD after Day 100, upon completion of donor T cell engraftment. T cell engraftment after TCD was uneven: engraftment kinetics were associated with residual host circulating CD8+ T cell counts after immune depletion; and aGVHD did not occur in the setting of mixed T cell chimerism (Figure). These observations demonstrate that aGVHD can occur with very low doses (105/kg) of allograft T cells after RIST. Protection from aGVHD conferred by mixed T cell chimerism may be lost with full donor T cell engraftment. With limited donor T cell numbers, host T cells appear to determine kinetics of engraftment and of aGVHD after RIST. Figure: 1. Post-induction circulating CD8+ T cell counts in TCD recipients with delayed donor T cell engraftment. 2. After TCD, all subjects who developed aGVHD did so at or after the establishment of T cell full donor T cell chimerism, and occasionally prior to any DLI. Shaded triangle represents the theoretical area in which values would fall if subjects developed aGVHD prior to complete donor T cell engraftment. Arrows: DLI. | Protocol | TCD | TCR | |:---------------------------------------------------------------------------------------------------------------------------------------------------------------- | ----------------------- | ---------------------- | | Flu/Cy: Fludarabine and cyclophosphamide; EPOCH-F: Etoposide, doxorubicin, vincristine, cyclophosphamide, prednisone and fludarabine; FDC: Full donor chimerism. | | | Median (range) | Median (range) | | Recipient Age | 43 years (32 – 56) | 44 (19 – 67) | | CMV Risk | 14/19 | 16/20 | | Pretransplant Immune Depletion | Flu/Cy | EPOCH-F | | Conditioning Regimen | Flu/Cy | Flu/Cy | | Pre-conditioning Host Cell Counts: | | | CD3 | 86 (1 – 701) | 140 (21 – 441) | | CD4, p=0.017 | 44 (1 – 156) | 71 (12 – 191) | | CD8 | 34 (0 – 555) | 55 (2 – 309) | | NK | 58 (0 – 376) | 88 (3 – 467) | | Day 0 CD3 Cell Count | 1 (1 – 6) | 5 (0 – 42) | | Allograft CD34+ cells/kg | 7.75 x 106 (5.1 – 12.9) | 7.68 x 106 (4.6–18.4) | | Allograft CD3+ cells/kg | 1.0 x 105 (preset) | 3.63 x 108 (1.5 – 8.3) | | Donor T cell engraftment | Day +70 (14 – 180) | 14 (14 – 100) | Patient and Transplant Characteristics and Outcomes ![Figure][1] Figure [1]: pending:yes

Relapse of hematologic malignancy is a major problem after allogeneic hematopoietic stem cell transplantation (alloHSCT), with limited treatment options of proven benefit other than donor lymphocyte infusions (DLI). Additionally, toxicity from treatment with cytotoxic chemotherapy after alloHSCT may differ from conventional treatments, and could include graft-versus-host disease, allograft failure, or increased risk of infection. We retrospectively reviewed treatment outcomes of 25 patients who received cytotoxic chemotherapy as treatment for relapsed hematologic malignancies after reduced-intensity, matched-sibling donor alloHSCT. Combination therapies included: EPOCH+/− rituximab (n=12 patients); “7&3” AML induction (ida/ara-c) (n=2); FLAG (n=2); asparaginase/6-MP/vincristine (n=1); R-ICE (n=1); MIME (n=1); BVP (n=1); and bortezomib/doxorubicin/dexamethasone (n=1). Single-agent therapies included: bortezomib (n=6); gemcitabine (n=4), vinorelbine (n=3); vincristine (n=1); methotrexate (n=1); and intrathecal methotrexate and/or cytarabine (n=5). A total of 133 cycles or doses were administered, of which 20 were supported with donor stem cell boosts, and another 9 were followed by nonmobilized DLI. There were 52 Grade 3 or higher toxicity episodes recorded, most commonly: neutropenia (10 episodes); infection with neutropenia (5 episodes); thrombocytopenia (6 episodes); and anemia (3 episodes). There were 12 episodes of CMV reactivation in 8 of 15 patients at risk, including 2 cases of pneumonitis and 1 case of colitis. GVHD flares were considered definitely chemotherapy-induced (2), possibly chemotherapy-induced (7), and unlikely chemotherapy-induced (2). Unusual events after treatment included culture-negative sepsis-like illness after bortezomib (n=2), secondary (11q23) AML of donor origin after one cycle of EPOCH (n=1) and diffuse alveolar hemorrhage after EPOCH (n=1). Seven patients achieved CR with therapy for post-transplant relapse, including three durable remissions. Four patients achieved PR and seven achieved disease stabilization. Median survival after starting cytotoxic therapy was 263 days. Timing of relapse appeared to be associated with survival, with median overall survival of 95 days for patients requiring therapy before Day 100 vs. 508 days for patients after Day 100 (p=0.0008). Treatment of relapse with cytotoxic chemotherapy after alloSCT is feasible and can result in durable remissions in a minority of patients. However, administration of cytotoxic therapy after alloHSCT requires monitoring and support for hematologic toxicities, GVHD and CMV reactivation; selected patients may benefit from prophylactic stem cell boosts or immune suppression. Survival after Cytotoxic Therapy for Relapse after alloHSCT Survival after Cytotoxic Therapy for Relapse after alloHSCT

6546 Background: Despite being the most common non-Hodgkin’s lymphoma, there have been no specific reports on the use of reduced-intensity (RI) allogeneic stem cell transplantation (alloSCT) to treat patients (pts) with diffuse large B-cell lymphomas (DBCL). This may be due to a lack of definitive evidence for a therapeutic graft-versus-lymphoma (GVL) effect against DLBC. We undertook a retrospective analysis to assess clinical outcomes and evidence of a GVL effect in DLBC pts undergoing RI alloSCT. Methods: The analysis was limited to 18 pts with primary refractory (n = 6) or relapsed (n = 12) DLBC. The median age was 43 years (range: 31–61); median number of previous treatments was 3 (range: 2–9). Nine (50%) pts had undergone autologous transplantation. Three (16%) pts were determined to have chemo-sensitive disease to last treatment prior to RI alloSCT. All pts received a RI conditioning regimen consisting of fludarabine (30 mg/m2/d × 4d) and cyclophosphamide (1200 mg/m2/d × 4d) followed by a T-cell replete allograft from HLA-matched siblings. Results: Median potential follow-up from transplant is 43 months. Seven (39%) pts developed grade II-IV acute GVHD. Response at day +100 post-transplant was as follows: complete response (CR/CRu) = 5; partial response = 5; progressive disease = 8. Nine of 17 (53%) evaluable pts developed chronic GVHD. Median progression-free survival (PFS) was 4.8 months; however, PFS after 9 months post-transplant was 31% with 5 pts in continuous CR/CRu > 12 months post-transplant. Among 14 pts who were not in CR/CRu (n = 12) or progressed after achieving a CR/CRu (n = 2) at day +100 post-transplant, 8 (57%) subsequently achieved a CR/CRu after removal of immune suppression and/or donor lymphocyte infusion (DLI) ± chemotherapy. Seven of these 8 pts remain in continuous (median = 34 months; range: 6–55+) CR/CRu without further treatment. Median survival for all 18 pts was 19 months with survival probability of 40% plateauing at 25 months post-transplant. Conclusions: The clinical observations of sustained CR/CRu after withdrawal of immune suppression and DLI suggest that a GVL effect exists against DLBC. RI alloSCT should be considered as a treatment option for pts with primary refractory and relapsed DLBC. No significant financial relationships to disclose.

Treatment of refractory or recurrent malignancy with donor lymphocyte infusion (DLI) after allogeneic hematopoietic stem cell transplantation (alloHSCT) is often not curative, with graft-vs-tumor (GVT) effects frequently accompanied by graft-versus-host disease (GVHD), requiring immune suppression that compromises efficacy. After alloHSCT, chimeric T lymphocytes infiltrating residual tumor (chimeric TIL) may provide enhanced antigen specificity and maintain tumor-specific homing. Compared with DLI, they may have a better GVT effect with less GVHD. Based on the success of autologous TIL therapy for melanoma, we tested the hypothesis that enhanced GVT with limited GVHD could be achieved through administration of ex-vivo activated chimeric TIL after alloHSCT. Preclinical TIL production carried out on several tumor types from non-transplanted patients demonstrated effective T cell isolation, expansion and activation using anti-CD3/CD28 bead co-stimulation, yielding a 10- to 30-fold expansion of CD3+ cells. Clinical evaluation of chimeric TIL therapy was initiated with a 51 year-old woman for metastatic breast cancer whose disease progressed after a T cell-depleted reduced-intensity alloHSCT with delayed DLI from a 6/6 HLA-matched sibling donor and subsequent conventional therapy plus DLI. Two weeks after administration of unmanipulated DLI, two thoracic metastases were surgically removed. T cells were liberated from 9.4 cm of tumor using enzymatic digestion and mechanical dispersion, lymphocyte-enriched by density gradient separation, and expanded for 14 days through co-stimulation with anti-CD3/CD28-coated magnetic beads (3:1 bead-to-total nucleated cell ratio) and media containing IL-2 (100 or 1000 IU/mL). This process yielded 42.5 x 106 cells, 33% expressing CD3, and generated 14.7 x 109 chimeric TIL, 85% expressing CD3 (a 3.1-log T cell expansion). There was no tumor contamination of the T cell product by immunohistochemistry. Flow cytometry demonstrated that the CD4/CD8 T cell ratio increased from 1.3 to 1.9 after expansion. Three infusions of the chimeric TIL product were given in a dose-escalating manner (5, 25 and 100 x 106 CD3+ cells/kg). A fourth infusion was given in conjunction with low-dose IL-2 (6mu SQ per day x 3D). CT scan performed after each infusion monitored disease response, with progressive disease the indication for the next dose administration. No infusion-related or delayed toxicities were observed, except for rigors following IL-2 administration. The patient shows no evidence of GVHD, even after the highest dose of 108 allogeneic T cells. Evaluation of the remaining thoracic lesion demonstrated progressive disease after the first two chimeric TIL dose-levels, transient disease stability one month after the third dose-level, and stable disease one month after the fourth dose with IL-2. This is the first clinical report of the application of chimeric TIL and represents a novel approach for developing new forms of adoptive immunotherapy in the setting of alloHSCT.

Allogeneic hematopoietic stem cells (HSC) generally engraft rapidly and completely after myeloablative conditioning. However, with reduced-intensity conditioning (RIC), mixed chimerism and graft failure are more common. Host immune status and HSC number are factors known to affect engraftment after reduced-intensity stem cell transplantation (RIST). In addition, donor T cells within the allograft may also influencethe kinetics of donor engraftment after RIST. To evaluate this, we performed a controlled comparison of engraftment outcomes among 3 groups undergoing RIST, varying by ex vivo T cell depletion (TCD) or in vivo depletion of activated T cells with methotrexate (MTX) to prevent graft-versus-host disease (GVHD). Group I (n = 50) received T cell replete (TCR) peripheral blood stem cells (PBSC) with cyclosporine (CSA) alone for GVHD prophylaxis. Group II (n = 17) received ex vivo TCD PBSC (positive/negative selection with T cell add-back to uniform dose of 1 x 105 CD3+ cells/kg) with CSA alone for GVHD prophylaxis. Group III (n = 31) received TCR PBSC with CSA plus MTX (5 mg/m2 IV x 4 doses) for GVHD prophylaxis. The 3 groups were similarly immunosuppressed from prior therapy before RIST (median absolute lymphocyte counts 330/μL, 260/μL, and 307/μL for Groups I, II, and III, respectively), and received an identical RIC regimen (fludarabine/cyclophosphamide) plus comparable numbers of filgrastim-mobilized PBSC from HLA-matched sibling donors (median 7.9 x 106, 7.6 x 106, and 6.8 x 106 CD34+ cells/kg, respectively; median 3.6 x 108, 1.0 x 105, and 3.2 x 108 CD3+ cells/kg, respectively). Hematopoietic recovery was slowest in Group III, consistent with the myelosuppressive effects of MTX (Table). A greater proportion of patients in Group I achieved complete donor chimerism (≥ 95%) by day +28 than in Groups II or III (P < 0.025), and at day +100, mixed donor chimerism persisted more often in Groups II and III than in Group I patients (P < 0.01). Correspondingly, early (< day +42) occurrence of grade 3–4 acute GVHD, before initiation of planned sequential donor lymphocyte infusions (DLI) in Group II, was more frequent in Group I than in either Groups II or III (p=0.08). Table: Hematopoietic Recovery, Engraftment, and GVHD Group Days to ANC > 500, median (range) Days to plt > 100, median (range) Donor chimerism ≥ 95% Early acute GVHD, grades 3–4 Day +28 Day +100 I 9 (7–13) 15.5 (12-42) 37/44 (84%) 36/38 (95%) 9/50 (18%) II 9 (7–10) 17.5 (11–40) 8/17 (47%) 9/14 (65%) 0/17 (0%) III 14 (7–21) 21.5 (12–85) 23/31 (74%) 21/31 (68%) 2/31 (6%) Thus, the deletion of T cells by either ex vivo TCD or in vivo MTX administration measurably alters the kinetics and degree of donor T cell engraftment after RIST. These observations provide evidence that donor T cells are an independent factor affecting engraftment of allogeneic HSC after RIST by compensating for incomplete host immune ablation. These data also support the hypothesis that a graft-versus-host effect plays a significant role in engraftment after RIST. Manipulation of donor T cells through graft engineering techniques may be a useful strategy to enhance engraftment in the setting of RIST.