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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.

Patients after autologous (autoSCT) and allogeneic stem cell transplantation (alloSCT) are at an increased risk of COVID-19-related morbidity and mortality, compounded by an immune system weakened by the underlying malignancy and prior treatments. Allogeneic transplantation, including stem cell and solid organ transplants, requires intensive immunosuppressive prophylaxis, which may further undermine the development of a protective vaccine-induced anti-viral immunity. Herein, we report on short- and long-term antiviral immune responses in two peri-stem cell transplant recipients and a third patient who received a COVID-19 vaccination after kidney transplantation. Our data indicate that: (1) patients post-alloSCT may be able to mount an anti-COVID-19 immune response; however, a sufficient time interval between transplant and exposure may be of critical importance; (2) alloSCT recipients with preexisting anti-SARS-CoV-2 immunity are at risk for losing protective humoral immunity following transplantation, particularly if the stem-cell donor lacks antiviral immunity, e.g., vaccine-derived immunity; and (3) some post-transplant patients are completely unable to build an immune response to a COVID-19 vaccine, perhaps based on the prophylactic suppression of T cell immunity.

PURPOSE Hematopoietic cell transplantation (HCT) is curative for hematologic disorders, but outcomes are historically inferior when using HLA-mismatched donors. Despite unrelated donor registries listing > 38 million volunteers, 25%-80% of US patients lack an HLA-matched unrelated donor, with significant disparity across ethnic groups. We hypothesized that HCT with a mismatched unrelated donor (MMUD) using post-transplant cyclophosphamide (PTCy), a novel strategy successful in overcoming genetic disparity using mismatched related donors, would be feasible and increase access to HCT. PATIENTS AND METHODS We performed a prospective phase II study of MMUD bone marrow HCT with PTCy for patients with hematologic malignancies. The primary end point was 1-year overall survival (OS), hypothesized to be 65% or better. 80 patients enrolled at 11 US transplant centers (December 2016-March 2019). Following myeloablative or reduced-intensity conditioning–based HCT, patients received PTCy on days +3, +4, with sirolimus and mycophenolate mofetil starting on day +5. We compared outcomes to Center for International Blood and Marrow Transplant Research contemporary controls receiving PTCy. RESULTS Notably, 48% of patients enrolled were ethnic minorities. 39% of pairs were matched for 4-6 out of 8 HLA alleles. The primary end point was met, with 1-year OS of 76% (90% CI, 67.3 to 83.3) in the entire cohort, and 72% and 79% in the myeloablative and reduced-intensity conditioning strata, respectively. Secondary end points related to engraftment and graft-versus-host-disease were reached. Multivariate analysis comparing the study group with other mismatched HCT controls found no significant differences in OS. CONCLUSION Our prospective study demonstrates the feasibility and effectiveness of HCT with an MMUD in the setting of PTCy. Remarkably, nearly half of the study participants belonged to an ethnic minority population, suggesting this approach may significantly expand access to HCT.

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.

Introduction: Patients with hematologic malignancies are at an increased risk of morbidity and mortality from COVID-19 disease (Vijenthira, Blood 2020). This is likely a result of combination of immunodeficiency conferred by the disease and the therapeutics. The immunogenicity of the COVID-19 vaccines in patients with exposure to CD19 directed Chimeric Antigen Receptor (CAR)-T cell therapy is not established. CD19 CAR-T cell therapies cause B-cell aplasia, which in turn can affect humoral immune response against novel antigens. Herein, we present results from our prospectively conducted clinical study to evaluate immune responses against mRNA based COVID-19 vaccines in patients with lymphoma who have received CD19 directed CAR-T cell therapy. Methods: All patients and healthy controls were enrolled in a prospective clinical study evaluating immune responses against commercial COVID-19 RNA vaccines in patients with hematologic malignancies. Plasma samples were generated from heparinized peripheral blood of 4 heathy controls (HCs) receiving the same vaccines and 19 B cell lymphoma patients treated with CD19 CAR- T cells. Samples from ~4 weeks post second dose of the vaccine (d56) were available for 14 CAR-T patients, for 5 CAR-T patients samples were available from ~4 weeks after the first dose (d28). Plasma samples were analyzed in an enzyme-linked immunosorbent assay (ELISA) using different full-length recombinant SARS-CoV-2 proteins and control proteins. Neutralizing activity was measured using the cPass Neutralization Antibody Detection Kit (GenScript Biotech). Results: Results from 4 healthy controls and 19 patients (12 males and 7 females) with lymphoma are reported. Median age for the lymphoma patients is 65 years. Eleven patients had large B cell lymphoma, 5 had follicular lymphoma and 3 had mantle cell lymphoma as primary diagnoses. Seventeen patients had advance stage disease (III/IV stage) and had received a median of 3 prior lines of therapy. All patients received CD19 directed CAR-T cell therapy. Ten patients received Moderna vaccine and 9 received Pfizer vaccine. Median time between CAR-T infusion and first COVID-19 vaccine was 258 days. While the peripheral blood plasma from 3/4 HCs already showed substantial SARS-CoV-2 neutralizing activity at ~4 weeks after the first dose of COVID-19 mRNA vaccine, none of the 5 CD19 CAR-T patients analyzed evidenced any antibody-mediated neutralizing activity in their blood at the same point in time (Figure 1A). Around 4 weeks after receiving the second dose of the vaccine, all 4 HCs tested evidenced complete or almost complete neutralizing activity (Figure 1B). In marked contrast, only 1 out of 14 CAR-T patients analyzed evidenced any relevant antibody-mediated SARS-CoV-2 neutralizing activity in their blood (Figure 1B). Interestingly, when we asked whether a globally insufficient antibody-mediated immunity was the underlying cause of the lack of a response to the COVID-19 vaccine in our CAR-T patients, we found that that was clearly not the case since anti-Flu, -TT, and -EBV responses were equivalent to the ones observed in HCs (Figure 2A). However, while at ~4 weeks post second dose of the vaccine the HCs showed marked antibody titers against all the viral spike proteins including their "delta" variants (Figure 2B), that was not the case for our CAR-T patients. The vast majority of our CAR-T patients did not evidence IgG antibody responses against any of the SARS-CoV-2 proteins analyzed such as S1, S1 delta, RBD, RBD delta, or S2 (Figure 2B). Conclusion: In this prospectively conducted clinical study, 18 of 19 patients with lymphoma who have received CD19 CAR-T therapy had poor immunogenicity against mRNA based COVID-19 vaccines as measured by neutralization assays and antibody titers. The antibody titers against B.1.617.2 (delta variant, S1 and RBD protein) were also demonstrably poor. The antibody response to common pathogens (flu, EBV, TT) were preserved, suggesting impaired immune response against novel antigens. Long-term follow-up of this study is ongoing. APR and DJ contributed equally Figure 1 Figure 1. Disclosures Dahiya: Kite, a Gilead Company: Consultancy; Atara Biotherapeutics: Consultancy; BMS: Consultancy; Jazz Pharmaceuticals: Research Funding; Miltenyi Biotech: Research Funding. Hardy: American Gene Technologies, International: Membership on an entity's Board of Directors or advisory committees; 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.

Introduction:Chimeric antigen receptor T-cell (CAR-T) therapy has become an important treatment modality for patients with relapsed/refractory (R/R) large B-cell lymphoma (LBCL). However, many of these patients have aggressive disease and require a form of bridging therapy (BT) for disease control during CAR-T manufacturing. There is limited data in the literature on the most appropriate form of BT and the impact of BT on clinical outcomes. Methods:We retrospectively analyzed data on 75 patients that received CAR-T therapy at our institution. BT was defined as therapy administered between apheresis and CAR-T infusion. 52 patients received bridging therapy (BT) and 23 did not receive BT (NBT). BT included 10 high dose (HD) steroids, 28 chemotherapy-based regimen (CT), and 14 radiation therapy (RT). CT included cytotoxic chemotherapy, immunotherapy, and targeted therapy. IRB approval was obtained for this study. Statistical analysis was conducted with SAS v9.4. Univariate analysis Cox proportional hazard model was used and p-values for response rate were generated from Fisher's exact test. The methods of generalized linear model and logistic regression were used to associate the toxicity grades and cytopenias with BT, respectively. Results:Many patient and disease characteristics between BT and NBT groups were similar, with minor, non-statistically significant differences (See Fig. 1a). Although while the incidence of stage III/IV patients in the BT and NBT group was comparable (p=0.79), in subgroup analysis, there were significantly more stage III/IV patients in the CT subgroup and NBT than in the RT and HD steroids subgroups (p=0.03). There was a higher incidence of bulky disease (≥10cm) in the BT and all BT subgroups versus (vs) NBT, although this was not significant (p=0.58 and p=0.92). The number of prior lines of therapy was comparable between the BT and NBT groups (p=0.99). However, in subgroup analysis there were significantly more patients in the CT subgroup and NBT that received ≥4 lines of therapy compared with RT and HD steroids subgroups (p=0.02). There was no significant difference in overall response rate (ORR) at last follow up between BT vs NBT and BT subgroups vs NBT with approximately 50% being in complete remission in all cases (p=0.48 and p=0.54). Progression free survival (PFS) and overall survival (OS) were similar in the BT vs NBT (one-year rates of 67% vs 64% and 83% vs 75%, respectively) and this was not statistically significant (p=0.52 and 0.89), see Fig. 1b and 1c. In subgroup analysis PFS was comparable in the BT subgroups (CT 69% and HD steroids 68%) vs NBT group (67%) while RT was lower (51%), although this was not statistically significant (p=0.54). In subgroup analysis OS was slightly worse in the BT subgroups (CT 77%, RT 76%, and HD steroids 72%) vs NBT group (83%) although was not statistically significant (p=0.93). The development of cytokine release syndrome (CRS) was comparable in the BT vs NBT group and in BT subgroups vs NBT (p=0.18 and p=0.53). The median grade of immune effector cell-associated neurotoxicity syndrome (ICANS) was higher in BT than NBT (grade 2 vs 0) and trended towards statistical significance (p=0.09). The development of cytopenias at day +180 following CAR-T therapy was significantly higher in BT (50%) vs NBT (13.3%) and was statistically significant (p= 0.038). Subgroup analysis also showed significantly increased cytopenias at day +180 in CT (58.3%) and RT (57.1%) subgroups (p= 0.04). Conclusion:In our single-institution experience, BT prior to CAR-T therapy is feasible and may preserve CAR-T candidacy in patients with rapidly progressive LBCL. BT does not appear to significantly affect ORR, PFS, and OS. The incidence of CRS was comparable, although there was a higher incidence of ICANS in BT, which trended towards significance, and could be contributed to higher tumor bulk in the BT group. BT patients receiving CT and RT for BT were more likely to experience prolonged cytopenias, likely due to the myelosuppressive impact of BT and previous lines of chemo-immunotherapy agents. In conclusion, in high-risk patients with advanced and/or aggressive disease, BT may provide disease stabilization to CAR-T with a similar toxicity profile compared to NBT patients, although BT patients are more likely to experience prolonged cytopenias after CAR-T therapy. Disclosures Kansagra: Alnylam Pharmaceuticals, Bristol Myers Squibb /Celgene, GlaxoSmithKline, Janssen, Pharmacyclics, Takeda Pharmaceuticals, Pfizer, Karyopharm Therpeutics:Other: Advisory Board.Hardy:Incyte Corporation:Other: Advisory Board Member;American Gene Technologies:Other: DSMB Member;Kite/Gilead:Other: Advisory Board Member.

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: CD34+ hematopoietic stem and progenitor cell (HSPC) dose during hematopoietic cell transplantation (HCT) remains one of the most reliable clinical parameters to predict quality of engraftment. A minimum HSPC dose of 2-2.5x10 6 CD34+ cells/kg is considered necessary for reliable engraftment, while optimal doses of 5-6x10 6 CD34+ cells/kg are associated with faster engraftment, as well as fewer transfusions, infections, and antibiotic days. CXCR4 inhibition significantly improves the number (#) of CD34+ HSPCs mobilized for HCT, when added to G-CSF (G). Motixafortide (M), a novel CXCR4 antagonist, is a potent mobilizer of HSPCs recently evaluated in the phase 3, double blind, placebo controlled, multicenter GENESIS Trial as a mobilizing agent prior to autologous HCT (ASCT) in multiple myeloma (MM). Methods: Patients received G (10 mcg/kg) on days 1-5 (and days 6-8, if needed). On day 4 (and day 6, if needed), patients received either M (1.25 mg/kg) or placebo (P). Apheresis began day 5, with up to 4 days of apheresis if needed. The primary and secondary endpoints were collection of ³6x10 6 CD34+ cells/kg in up to 2 days of apheresis or 1 day, respectively. The # of CD34+ cells/kg infused was determined independently by each investigator according to local practice, but a minimum of ³2x10 6 CD34+ cells/kg was required. A post-hoc analysis was performed pooling data from both arms to evaluate time to platelet engraftment (TPE) (≥20x10 9/L without transfusions x7 days) and neutrophil engraftment (TNE) (ANC ≥0.5x10 9/L x3 days) based on total # of CD34+ cells/kg and # of specific CD34+ HSPC subsets infused. CD34+ HSPC immunophenotyping was performed via multicolor fluorescence-activated cell sorting (FACS). TPE/TNE was analyzed using Kaplan-Meier curves and Cox proportional hazards model. Results: 114 MM patients underwent apheresis, ASCT and were evaluable (M+G N=77; P+G N=37). M+G mobilization yielded a median of 10.8x10 6 CD34+ cells/kg collected in 1 apheresis vs 2.3x10 6 CD34+ cells/kg with P+G (p75 th percentile) of combined CD34+ HSC, MPP, CMP and GMP subsets was associated with faster TPE of 12 days vs 19 days with lower #s of these subsets (p=0.003) (Figure 2A). Furthermore, higher #s (>75 th percentile) of GMPs was individually associated with faster TPE of 13 days vs 19 days with lower GMP cell doses (p=0.0116) (Figure 2C). TNE was not impacted by increasing doses of total CD34+ HSPCs or any specific CD34+ HSPC subset (all p>0.05) (Figures 1B, 2B and 2D). Conclusions: M+G mobilization enabled significantly more CD34+ cells to be collected in 1 apheresis (median 10.8x10 6 CD34+ cells/kg) vs P+G (2.3x10 6 CD34+ cells/kg), as well as 3.5-5.6 fold higher #s of HSCs, MPPs, CMPs and GMPs (all p-values Figure 1 Figure 1. Disclosures Crees: BioLineRx Ltd.: Research Funding. Retting: BioLineRx Ltd.: Research Funding. Larson: TORL biotherapeutics: Current holder of individual stocks in a privately-held company; Abbvie, Bioline, BMS, Celgene, GSK, Janssen, Juno, Novartis, Pfizer, Takeda: Research Funding. Illes: Novartis, Janssen, Pfizer, Roche: Other: Travel, Accommodations, Expenses; Takeda, Seattle Genetics: Research Funding; Janssen, Celgene, Novartis, Pfizer, Takeda, Roche: Consultancy. Stiff: CRISPR: Consultancy; Gamida-Cell, Atara, Amgen, Incyte, Takeda, Macrogenetics, Eisai: Research Funding. Sborov: SkylineDx: Consultancy; GlaxoSmithKline: Consultancy; Sanofi: Consultancy; Janssen: Consultancy, Membership on an entity's Board of Directors or advisory committees. Pereira: Jazz Pharmaceutical: Membership on an entity's Board of Directors or advisory committees. Mikala: Abbvie: Consultancy; Amgen: Consultancy; Celgene: Consultancy; Janssen: Consultancy; Krka: Consultancy; Novartis: Consultancy; Takeda: Consultancy. Holtick: Sanofi: Honoraria; Celgene: Honoraria. Qazilbash: Janssen: Research Funding; Oncopeptides: Other: Advisory Board; Biolline: Research Funding; Bristol-Myers Squibb: Other: Advisory Board; NexImmune: Research Funding; Amgen: Research Funding; Angiocrine: Research Funding. Hardy: 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; InCyte: Membership on an entity's Board of Directors or advisory committees. Sorani: BioLineRx LTD: Current Employment. Shemesh-Darvish: BioLineRx LTD: Current Employment. Vainstein: BioLineRx LTD: Current Employment; Enlivex: Consultancy. Kadosh: StatExcellence: Current holder of individual stocks in a privately-held company; BioLineRx: Honoraria.

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 Despite international unrelated donor (URD) registries listing >36 million volunteer donors, 25-80% of U.S. patients lack an HLA-matched (8/8 alleles) URD, with greater disparities in access for ethnic minorities. We hypothesized that hematopoietic cell transplantation (HCT) with a mismatched unrelated donor (MMUD) using post-transplant cyclophosphamide (PTCY), a strategy successful in overcoming genetic disparity in related haplo-identical donor HCT (haplo HCT) would be associated with similar outcomes to haplo HCT and expand access to HCT. Selecting a MMUD may have benefits over a haplo donor, such as removing risk associated with donor specific antibodies, and allowing for preferential selection of other favorable donor factors, such as younger age. Methods The NMDP/BTM performed a prospective phase II study of MMUD bone marrow (BM) HCT with PTCY for patients with hematologic malignancies, with the primary hypothesis that 1-year overall survival (OS) would be 65% or greater. Patients with a suitable HLA matched sibling or URD were excluded. Matching for 4-7/8 at HLA-A, -B, -C, and -DRB1 was permitted. 80 patients enrolled (40 myeloablative conditioning (MAC) - using cyclophosphamide/TBI (n=6), busulfan/cyclophosphamide (n=3) or fludarabine/ busulfan (n=31); 40 reduced intensity conditioning (RIC) - using fludarabine/cyclophosphamide/TBI) at 11 U.S. transplant centers between Dec 2016 and March 2019. Patients received a fresh BM graft, PTCY on days +3, +4, with sirolimus/mycophenolate mofetil starting on day +5. Regimen intensity was at the center's discretion. We compared outcomes to three groups of contemporaneous controls, all receiving PTCY, whose data was collected by CIBMTR: MMUD using peripheral blood stem cells (PBSC) (n=143), and haplo using BM (n=398) or PBSC (n=1191). All analyses used standard stepwise Cox regression modeling, performed separately for MAC and RIC cohorts. The main variable of interest was the donor/graft type (all groups compared to the trial cohort of MMUD BM). Statistical significance is p=0.05. Results The study achieved its primary endpoint with 1-year OS of 76% (90% CI: 67.3-83.3) in the entire cohort; survival and GVHD-/relapse-free survival (GRFS, defined in table 1) were 72% and 37% in the MAC cohort and 79% and 53% in the RIC cohort, respectively. Additional study outcomes are shown in Table 1. Median patient age was 49 years old (yo) (range: 18-66, MAC) and 60 yo (range: 23-70, RIC). HCT were performed for acute leukemia (n=58), MDS (n=2), lymphoma (n=17) and CLL (n=3). Disease risk index was low (n=11), intermediate (n=63), high (n=13) or very high (n=4). KPS was Conclusion Our prospective study demonstrated that outcomes using MMUD in the setting of PTCY are similar to those obtained using a haplo donor. Approximately half of the study participants were ethnic minorities, a figure consistent with expectations based on donor availability within registries, but exceeding expectations in accrual to a prospective study. These results support the feasibility of using volunteer MMUDs to expand access to HCT, especially for ethnically diverse patients. Next steps include expanding the MMUD PTCY approach to incorporate PBSC as a graft source and prospectively studying questions related to selection based on donor characteristics and additional GVHD prophylaxis agents. Disclosures Shaw: Orca Bio: Consultancy. Khimani:Bristol Myers Squibb-Moffitt-Alliance: Research Funding. Shah:Cell Vault: Research Funding; Celgene: Consultancy, Honoraria; Verastim: Consultancy; Lily: Consultancy, Honoraria; TG Therapeutics: Consultancy; Incyte: Consultancy; Miltenyi Biotec: Honoraria, Research Funding; Kite Pharma: Consultancy, Honoraria. Farhadfar:CSL Behring: Research Funding; Incyte pharmaceutical: Other: Member of GVHD advisory forum. Hardy:Kite/Gilead: Other: Advisory Board Member; Incyte Corporation: Other: Advisory Board Member; American Gene Technologies: Other: DSMB Member. Perales:Medigene: Membership on an entity's Board of Directors or advisory committees, Other; NexImmune: Membership on an entity's Board of Directors or advisory committees; Servier: Membership on an entity's Board of Directors or advisory committees, Other; 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; Takeda: 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; Nektar Therapeutics: Honoraria, Membership on an entity's Board of Directors or advisory committees; Merck: Consultancy, Honoraria; Kite/Gilead: Honoraria, Research Funding; Miltenyi Biotec: Research Funding; Incyte Corporation: Honoraria, Research Funding; MolMed: Membership on an entity's Board of Directors or advisory committees; Bristol Myers Squibb: Honoraria, Membership on an entity's Board of Directors or advisory committees; Omeros: Honoraria, Membership on an entity's Board of Directors or advisory committees; Cidara Therapeutics: Other; Celgene: Honoraria. Komanduri:Kite/Gilead: 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; Adaptimmune: Membership on an entity's Board of Directors or advisory committees; Atara: Consultancy, Membership on an entity's Board of Directors or advisory committees; Celgene: Consultancy; Takeda: Consultancy; Kiadis: Consultancy. Luznik:Merck: Research Funding, Speakers Bureau; AbbVie: Consultancy; WindMil Therapeutics: Patents & Royalties: Patent holder; Genentech: Research Funding. Pidala:Syndax: Consultancy, Membership on an entity's Board of Directors or advisory committees; CTI Biopharma: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Amgen: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Research Funding; Takeda: Research Funding; Janssen: Research Funding; Johnson and Johnson: Research Funding; Pharmacyclics: Research Funding; Abbvie: Research Funding; BMS: Research Funding. Devine:Magenta Therapeutics: Consultancy. Bolanos-Meade:Incyte: Other: DSMB Fees.

Background Despite increasing donor options for allogeneic transplantation, including matched/mismatched related donors, matched unrelated donors and cord blood units, a proportion of patients do not find a donor. This is especially relevant in patients from racial/ethnic minorities. Post-transplant cyclophosphamide (PTCY) has successfully overcome barriers related to HLA-mismatching in the related donor setting. We hypothesized that transplantation with a mismatched unrelated donor (MMUD) using PTCY would be feasible and associated with high engraftment and acceptable GVHD incidence. Methods We performed a prospective Phase II study of MMUD bone marrow (BM) transplantation with PTCY for patients with hematologic malignancies. Patients with a suitable HLA matched related or URD were excluded. Patients received a fresh BM graft, followed by PTCY on days +3, +4, Sirolimus/MMF starting on Day+5. Matching for 4-7/8 at HLA-A, -B, -C, and –DRB1 was permitted. We enrolled 80 patients (40 full intensity conditioning [FIC]; 40 reduced intensity conditioning [RIC]) at 11 transplant centers in the U.S. between Dec 2016 and March 2019. Regimen intensity was at the center's discretion. Results Characteristics are shown in Table 1. Importantly, 48% of patients were non-white/Hispanic, 55% had an HCT-CI >2 and 34% had a KPS of 1 HLA allele, 59% were under 30. Overall survival and non-relapse mortality at 100 days were 92% and 5% in the FIC arm, and 90% and 7.5% in the RIC arm (Table 2). Neutrophil recovery was 98% in both arms, with no primary graft failure in the FIC arm, and 7.5% in the RIC arm. Peripheral blood donor chimerism was >75% at all timepoints. Acute GVHD grade III-IV at day 100 was relatively high at 25% in the FIC arm but very low at 2.6% in the RIC arm. Viral reactivations were high (Table 3). Conclusion These early (day 100) results of our prospective study show high rates of engraftment with acceptable rates of GVHD in recipients of MMUD transplantation with PTCY, despite a high degree of HLA mismatch. An important finding is that ethnic minorities represent almost 50% of the study population, showing that this approach expands access to patients in need of potentially curative therapy. BK and HHV-6 virus reactivation/infection were common, the clinical significance of which requires further study. Understanding the risks for and impact of graft failure and acute GVHD is being studied as follow up continues.

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.

In the Second Annual National Cancer Institute's Workshop on the Biology, Prevention, and Treatment of Relapse after Hematopoietic Stem Cell Transplantation, the Scientific/Educational Session on the Prevention and Treatment of Relapse after Allogeneic Transplantation highlighted progress in developing new therapeutic approaches since the first relapse workshop. Recent insights that might provide a basis for the development of novel, practical clinical trials were emphasized, including utilization of newer agents, optimization of donor lymphocyte infusion (DLI), and investigation of novel cellular therapies. Dr. de Lima discussed pre-emptive and maintenance strategies to prevent relapse after transplantation, for example, recent promising results suggestive of enhanced graft-versus-tumor activity with hypomethylating agents. Dr. Schmid provided an overview of adjunctive strategies to improve cell therapy for relapse, including cytoreduction before DLI, combination of targeted agents with DLI, and considerations in use of second transplantations. Dr. Porter addressed strategies to enhance T cell function, including ex vivo activated T cells and T cell engineering, and immunomodulatory approaches to enhance T cell function in vivo, including exogenous cytokines and modulation of costimulatory pathways.

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.

In experimental models, ex vivo induced T-cell rapamycin resistance occurred independent of T helper 1 (Th1)/T helper 2 (Th2) differentiation and yielded allogeneic CD4+ T cells of increased in vivo efficacy that facilitated engraftment and permitted graft-versus-tumor effects while minimizing graft-versus-host disease (GVHD). To translate these findings, we performed a phase 2 multicenter clinical trial of rapamycin-resistant donor CD4+ Th2/Th1 (T-Rapa) cells after allogeneic-matched sibling donor hematopoietic cell transplantation (HCT) for therapy of refractory hematologic malignancy. T-Rapa cell products, which expressed a balanced Th2/Th1 phenotype, were administered as a preemptive donor lymphocyte infusion at day 14 post-HCT. After T-Rapa cell infusion, mixed donor/host chimerism rapidly converted, and there was preferential immune reconstitution with donor CD4+ Th2 and Th1 cells relative to regulatory T cells and CD8+ T cells. The cumulative incidence probability of acute GVHD was 20% and 40% at days 100 and 180 post-HCT, respectively. There was no transplant-related mortality. Eighteen of 40 patients (45%) remain in sustained complete remission (range of follow-up: 42-84 months). These results demonstrate the safety of this low-intensity transplant approach and the feasibility of subsequent randomized studies to compare T-Rapa cell-based therapy with standard transplantation regimens. This trial was registered at www.cancer.gov/clinicaltrials as #NCT 00077480.

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).

Donor lymphocyte infusion (DLI), a standard relapse treatment after allogeneic stem cell transplantation (AlloSCT), has limited efficacy and often triggers GVHD. We hypothesized that after AlloSCT tumor-infiltrating donor lymphocytes could be costimulated ex vivo to preferentially activate/expand antitumor effectors. We tested the feasibility and safety of costimulated, tumor-derived donor lymphocyte (TDL) infusion in a phase 1 trial. Tumor was resected from 8 patients with B-cell malignancy progression post-AlloSCT; tumor cell suspensions were costimulated with anti-CD3/anti-CD28 Ab-coated magnetic beads and cultured to generate TDL products for each patient. Costimulation yielded increased proportions of T-bet+FoxP3− type 1 effector donor T cells. A median of 2.04 × 107 TDL/kg was infused; TDLs were well tolerated, notably without GVHD. Two transient positron emission tomography (PET) responses and 2 mixed responses were observed in these refractory tumors. TDL are a feasible, tolerable, and novel donor cell therapy alternative for relapse after AlloSCT. This trial is registered at clinicaltrials.gov as no. NCT00445666.

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.

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.

Purpose: Metastatic breast cancer (MBC) response to allogeneic lymphocytes requires donor T-cell engraftment and is limited by graft-versus-host disease (GVHD). In mice, type-II–polarized T cells promote engraftment and modulate GVHD, whereas type-I–polarized T cells mediate more potent graft-versus-tumor (GVT) effects. This phase I translational study evaluated adoptive transfer of ex vivo costimulated type-I/type-II (T1/T2) donor T cells with T-cell–depleted (TCD) allogeneic stem cell transplantation (AlloSCT) for MBC. Experimental Design: Patients had received anthracycline, taxane, and antibody therapies, and been treated for metastatic disease and a human leukocyte antigen (HLA)-identical–sibling donor. Donor lymphocytes were costimulated ex vivo with anti-CD3/anti-CD28 antibody–coated magnetic beads in interleukin (IL)-2/IL-4–supplemented media. Patients received reduced intensity conditioning, donor stem cells and T1/T2 cells, and monitoring for toxicity, engraftment, GVHD, and tumor response; results were compared with historical controls, identically treated except for T1/T2 product infusions. Results: Mixed type-I/type-II CD4+ T cells predominated in T1/T2 products. Nine patients received T1/T2 cells at dose level 1 (5 × 106 cells/kg). T-cell donor chimerism reached 100% by a median of 28 days. Seven (78%) developed acute GVHD. At day +28, five patients had partial responses (56%) and none had MBC progression; thereafter, two patients had continued responses. Donor T-cell engraftment and tumor responses appeared faster than in historical controls, but GVHD rates were similar and responders progressed early, often following treatment of acute GVHD. Conclusion: Allogeneic T1/T2 cells were safely infused with TCD-AlloSCT, appeared to promote donor engraftment, and may have contributed to transient early tumor responses. Clin Cancer Res; 17(21); 6878–87. ©2011 AACR.