Abstract: Allogeneic hematopoietic cell transplantation (HCT) is a curative therapy for hematological malignancies for which graft-versus-host disease (GVHD) remains a major complication. The use of donor T-regulatory cells (Tregs) to prevent GVHD appears promising, including in our previous evaluation of an engineered graft product (T-reg graft) consisting of the timed, sequential infusion of CD34+ hematopoietic stem cells and high-purity Tregs followed by conventional T cells. However, whether immunosuppressive prophylaxis can be removed from this protocol remains unclear. We report the results of the first stage of an open-label single-center phase 2 study (NCT01660607) investigating T-reg graft in myeloablative HCT of HLA-matched and 9/10-matched recipients. Twenty-four patients were randomized to receive T-reg graft alone (n = 12) or T-reg graft plus single-agent GVHD prophylaxis (n = 12) to determine whether T-reg graft alone was noninferior in preventing acute GVHD. All patients developed full-donor myeloid chimerism. Patients with T-reg graft alone vs with prophylaxis had incidences of grade 3 to 4 acute GVHD of 58% vs 8% (P = .005) and grade 3 to 4 of 17% vs 0% (P = .149), respectively. The incidence of moderate-to-severe chronic GVHD was 28% in the T-reg graft alone arm vs 0% with prophylaxis (P = .056). Among patients with T-reg graft and prophylaxis, CD4+ T-cell–to–Treg ratios were reduced after transplantation, gene expression profiles showed reduced CD4+ proliferation, and the achievement of full-donor T-cell chimerism was delayed. This study indicates that T-reg graft with single-agent tacrolimus is preferred over T-reg graft alone for the prevention of acute GVHD. This trial was registered at www.clinicaltrials.gov as #NCT01660607.

Abstract: Background: Autologous stem cell transplantation (ASCT) is a curative therapy for a significant proportion of patients with relapsed/refractory (R/R) classic Hodgkin lymphoma (cHL). We previously developed a conditioning regimen for R/R cHL patients undergoing ASCT incorporating gemcitabine and vinorelbine (GN-BVC), which enabled a reduction in the BCNU dose and toxicity without compromising efficacy (BBMT 2010;16:1145-54). Since this publication, several novel agents have been approved for treatment of R/R cHL including brentuximab vedotin (BV) and the immune checkpoint inhibitors (ICIs), which may be changing outcomes and toxicities following ASCT. We sought to determine whether post-ASCT outcomes have improved for R/R cHL in the era of novel agents, and to evaluate how BV and the ICIs have impacted toxicities after ASCT in a large cohort of patients treated with the same conditioning regimen. Methods: We conducted a single-center, retrospective analysis of outcomes for a large cohort of patients with R/R cHL who underwent ASCT using GN-BVC conditioning at Stanford University from 2001-2017 (n=268). We divided the cohort into two treatment eras: Era A: 2001-2009 (n=137) and Era B (increasing use of novel agents): 2010-2017 (n=131). We used Kaplan-Meier and Cox models to compare overall survival (OS), progression-free survival (PFS), and post-progression survival (PPS) between treatment eras. We also compared outcomes between patients who underwent ASCT in complete remission (CR, n=126) or with a partial response (PR, n=142). For patients treated in era B, we compared outcomes and toxicity profiles for patients treated with standard platinum-based salvage regimens (n=102) to those who received BV-based salvage regimens prior to ASCT (n=29). Results: Patients who underwent ASCT in era B had improved OS compared to those transplanted in era A (4-year OS: 87.8% vs 77.9%, HR 0.51, 95% CI 0.28-0.91, p=0.022), but PFS did not differ significantly between treatment eras (4-year PFS: 70.2% vs 62.7%, HR 0.78, 95% CI 0.52-1.2, p=0.24, Figure 1). For patients who relapsed after ASCT, PPS was significantly higher for those transplanted in era B compared to era A (84.7% vs 62.8% at 2 years, HR 0.47, 95% CI 0.23-0.98, p=0.045). Overall, patients who underwent ASCT in CR compared to those with a PR had significantly improved OS (88.3% vs 78.3% at 4 years, HR 0.50, 95% CI 0.29-0.88, p=0.016) and PFS (78.4% vs 55.1% at 4 years, HR 0.44, 95% CI 0.28-0.67, p=0.00016). Among patients who relapsed, those in era B who received novel agents (BV and/or an ICI) at any point in treatment exhibited higher OS compared to historical controls in era A (4-year OS: 72.2% vs 53.1%) but were statistically different only at the p=0.083 level which is above the p=0.05 significance threshold. Of the patients who underwent ASCT in era B (n=131), 102 (78%) received standard platinum-based salvage regimens (e.g. ICE or DHAP) and 29 (22%) received BV-based salvage regimens prior to ASCT, including 11 patients (8%) who received both BV and an ICI pre-ASCT. Outcomes were excellent for patients who received BV-based salvage regimens pre-ASCT (4-year OS 97% and PFS 76%) but were not statistically different compared to patients who received platinum-based regimens (4-year OS 86% and PFS 69%; p=0.56 and p=0.76, respectively). Pneumonitis requiring corticosteroids occurred in 8% of patients treated in era B, including 10% of patients receiving BV-based salvage regimens pre-ASCT and 7% of patients receiving standard platinum-based regimens. One patient who received BV and nivolumab pre-ASCT died from grade 5 pneumonitis. Conclusions: In this cohort of R/R cHL patients who underwent ASCT using the same conditioning regimen, OS was significantly higher for patients transplanted within the past decade. A potential survival benefit was observed among patients who relapsed post-ASCT, likely reflecting the more widespread use of BV and ICIs in the post-ASCT setting. Patients who received BV-based salvage regimens pre-ASCT had excellent outcomes without an apparent increase in toxicity, but the small number of patients limits comparisons to standard platinum-based regimens. Further studies are needed to better define the optimal sequencing of novel agents and ASCT in the treatment of R/R cHL in the modern era. Figure 1 Disclosures Sica: Physician's Education Resources (PER): Honoraria. Advani:Celgene: Research Funding; Takeda: Consultancy, Membership on an entity's Board of Directors or advisory committees; Cell Medica, Ltd: Consultancy; Kyowa Kirin Pharmaceutical Developments, Inc.: Consultancy; Regeneron: Research Funding; Celmed: Consultancy, Membership on an entity's Board of Directors or advisory committees; Stanford University: Employment, Equity Ownership; Seattle Genetics: Consultancy, Research Funding; Agensys: Research Funding; AstraZeneca: Consultancy, Membership on an entity's Board of Directors or advisory committees; Autolus: Consultancy, Membership on an entity's Board of Directors or advisory committees; Bayer: Consultancy, Membership on an entity's Board of Directors or advisory committees; Bristol-Myers Squibb: Membership on an entity's Board of Directors or advisory committees, Research Funding; Kura: Research Funding; Merck: Research Funding; Infinity Pharma: Research Funding; Roche/Genentech: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Gilead Sciences, Inc./Kite Pharma, Inc.: Consultancy, Membership on an entity's Board of Directors or advisory committees; Janssen: Research Funding; Forty-Seven: Research Funding; Pharmacyclics: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Millennium: Research Funding. Miklos:AlloGene: Membership on an entity's Board of Directors or advisory committees; Precision Bioscience: Membership on an entity's Board of Directors or advisory committees; Miltenyi Biotech: Membership on an entity's Board of Directors or advisory committees; Becton Dickinson: Research Funding; Novartis: Membership on an entity's Board of Directors or advisory committees, Research Funding; Adaptive Biotechnologies: Membership on an entity's Board of Directors or advisory committees; BMS: Membership on an entity's Board of Directors or advisory committees; Kite-Gilead: Membership on an entity's Board of Directors or advisory committees, Research Funding; Juno: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees. Muffly:Pfizer: Consultancy; Adaptive: Research Funding; KITE: Consultancy. Rezvani:Kaleido: Membership on an entity's Board of Directors or advisory committees, Other: one-time compensation from advisory boards; Nohla Therapeutics: Membership on an entity's Board of Directors or advisory committees, Other: one-time compensation from advisory boards; AbbVie: Other: Principal investigator ; U.S. Department of Justice: Other: Expert medical witness; Johnson & Johnson: Employment, Other: Brother is employed. Shizuru:Forty Seven Inc: Equity Ownership, Patents & Royalties.

Abstract: BACKGROUND: CD22 is expressed on the majority of B-cell malignancies. Autologous CAR T-cells targeting CD22 (CAR22) have yielded objective response rates (ORR) of 70-90% in pediatric patients with relapsed/refractory (R/R) B-cell acute lymphoblastic leukemia (ALL), including those who had previously failed CD19-directed CAR T-cell (CAR19) therapy. Based on these encouraging results, we evaluated CAR22 in adult patients with R/R ALL and for the first time in patients with R/R large B-cell lymphoma (LBCL), including those who had failed prior autologous CAR19 therapy. METHODS: This single-institution phase I dose escalation clinical trial (NCT04088890) is evaluating a CAR construct incorporating the m971 CD22 single chain variable fragments and 41BB/CD3z endodomains integrated within autologous T-cells via lentiviral transduction. After lymphodepletion with fludarabine and cyclophosphamide, patients were infused with fresh or cryopreserved CAR T-cells after a 7- to 11-day closed manufacturing process utilizing the CliniMACS Prodigy device (Miltenyi). The current cohort includes patients treated at dose level 1 (DL1), which was 1x106 CAR+ cells/kg. Primary objectives assessed the ability to successfully manufacture CAR22 and safety. Overall response rate (ORR) at 28 days post-infusion (D28) was a secondary objective. RESULTS: Three patients with LBCL have been enrolled with a median age of 53 years (range, 51-57) and a median of 6 (range, 5-8) prior lines of therapy. All three patients received prior CAR19 and had refractory disease to second-line or later therapy (n=3); had not undergone autologous hematopoietic stem cell transplantation (HSCT) (n=3); had MYC and BCL2 gene rearrangements (double-hit lymphoma; n=2); had high tumor burden (SPD & gt;50 cm2; n=2); had a history of primary refractory disease (n=1); or had never achieved CR to any therapy (n=1). Six patients with ALL have been enrolled with a median age of 43.5 years (range, 23-62) and a median of 6 (range, 4-8) prior lines of therapy. All six patients received prior allogeneic HSCT and had Ph-positive disease (n=3); had central nervous system (CNS) involvement (n=3); had extramedullary disease (n=2); had high disease burden (BM blasts & gt;5%; n=2); had received prior CD19-directed therapy (n=5); or had received prior CD22-directed therapy (n=3). Successful manufacturing of cells at DL1 was achieved in all patients. All patients (LBCL n=3, ALL n=6) reached day 28 and are included in the safety and response analysis presented here; updated results will be presented at the meeting. Eight patients (88.9%) experienced cytokine release syndrome (CRS); all were Grade 1-2. There were no cases of immune effector cell-associated neurotoxicity syndrome (ICANS). No differences in toxicities were seen across the patient age spectrum and no Grade 5 toxicities occurred following CAR22 infusion. In LBCL, all patients achieved a response at D28 (ORR=100%; CR, n=1, PR, n=2). Both patients with a D28 PR improved to CR by day 90 and 180. All patients remain in CR, with a median follow-up of 8.4 months (range, 6-9.3). In ALL, all patients achieved a CR at D28 (ORR=100%; MRD-, n=5, MRD+, n=1). After a median follow up of 5.1 months (range, 1-8.2), three patients relapsed at 2.5, 4, and 5.5 months after infusion; one patient died while undergoing subsequent therapy 7.3 months post-infusion. CD22 expression by flow cytometry was downregulated or absent in two patients after relapse. Peak CAR expansion as detected by peripheral blood flow cytometry reached a median level of 90.1 (LBCL; range, 85.4-350) and 43.4 (ALL; range, 0.9-399.6) CAR+ cells/µL between D14 and D21. In two LBCL patients with progression following CAR19, CAR22 levels were 11.7 and 55.9 fold higher than prior CAR19 levels at peak expansion. CONCLUSIONS: Infusion of CD22-targeting CAR T-cells in R/R LBCL and ALL is safe and well tolerated. Manufacturing of CAR22 was uniformly successful. To date, 3 of 3 heavily treated adult patients with LBCL whose disease relapsed after prior CAR19 have each achieved CR durable to at least 6 months. All adult ALL patients have achieved CR following CAR22, with some early relapses observed. Accrual is ongoing. Disclosures Negrin: Amgen: Consultancy; Biosource: Current equity holder in private company; UpToDate: Honoraria; KUUR Therapeutics: Consultancy; Magenta Therapeutics: Consultancy, Current equity holder in publicly-traded company; BioEclipse Therapeutics: Current equity holder in private company. Rezvani:Pharmacyclics: Research Funding. Shiraz:ORCA BioSystems: Research Funding; Kite, a Gilead Company: Research Funding. Sidana:Janssen: Consultancy. Mackall:BMS: Consultancy; Allogene: Current equity holder in publicly-traded company; Apricity Health: Consultancy, Current equity holder in private company; Nektar Therapeutics: Consultancy; NeoImmune Tech: Consultancy; Lyell Immunopharma: Consultancy, Current equity holder in private company. Miklos:Kite-Gilead: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other: Travel support, Research Funding; Adaptive Biotech: Consultancy, Other: Travel support, Research Funding; Allogene Therapeutics Inc.: Research Funding; Juno-Celgene-Bristol-Myers Squibb: Consultancy, Other: Travel support, Research Funding; Novartis: Consultancy, Other: Travel support, Research Funding; Pharmacyclics: Consultancy, Other: Travel support, Patents & Royalties, Research Funding; Janssen: Consultancy, Other: Travel support; Miltenyi Biotec: Research Funding. Muffly:Amgen: Consultancy; Adaptive: Research Funding; Servier: Research Funding. OffLabel Disclosure: CD22-directed CAR T-cell Therapy for the treatment of adults with relapsed/refractory LBCL and B-ALL

Abstract: Background: Nonmyeloablative total lymphoid irradiation and antithymocyte globulin (TLI-ATG) conditioning is associated with a low risk of graft-versus-host disease (GVHD) and non-relapse mortality (NRM) while retaining graft-versus-tumor activity across a range of lymphoid and myeloid malignancies. Prior studies of TLI-ATG conditioning have been limited by the relatively small sample size and short duration of follow up. Herein we report mature data from a large, single-institution cohort of patients with lymphoid and myeloid malignancies who underwent allogeneic transplantation using TLI-ATG conditioning. Methods: Patients: We included all consecutively transplanted patients at Stanford University Hospital from December 2001 through December 2016 who underwent allogeneic hematopoietic cell transplantation (HCT) using TLI-ATG conditioning for lymphoid or myeloid malignancies. All patients received G-CSF-mobilized peripheral blood hematopoietic cells and cyclosporine and mycophenolate mofetil for GVHD prophylaxis. Statistical analysis: The data were analyzed as of December 31, 2017, allowing for a minimum follow up of 1 year for all patients. For time-to-event analyses, the Kaplan-Meier method was used to estimate overall survival (OS), progression-free survival (PFS), and the cumulative incidence of acute and chronic GVHD and NRM. An exploratory analysis was done to identify factors associated with mortality and relapse. Log-rank tests were used to calculate differences between groups. Results: Patient characteristics: 613 patients underwent allogeneic HCT with TLI-ATG conditioning at a median age of 60 years (range 21-78 years) with a median follow up of 5.1 years (range 1.0-15.3 years). Diagnoses included acute myeloid leukemia (AML, N=194), myelodysplastic syndrome (MDS, N=93), myelofibrosis (N=10), chronic myeloid leukemia (N=12), acute lymphoblastic leukemia (N=11), chronic lymphocytic leukemia (CLL, N=83), non-Hodgkin lymphoma (NHL, N=175), and Hodgkin lymphoma (HL, N=35). 44% of patients had HLA-matched related, 41% had HLA-matched unrelated, and 15% had HLA-mismatched unrelated donors. 34% of patients had a comorbidity index ≥3, and 34% of patients had a disease risk index (DRI) of high or very high. 55% of lymphoma patients had failure of prior autologous HCT. Safety and tolerability: Patient outcomes are shown in Figure 1. Among all 613 patients, the cumulative incidences of acute GVHD grade 2-4 and grade 3-4 at day +100 were 11% and 4%, respectively, and the cumulative incidence of extensive chronic GVHD was 21% at 1 year. NRM was 7% at 1 year, and was consistently low across high-risk subgroups including older adults ≥65 years old (9% at 1 year), patients with a comorbidity index ≥3 (9% at 1 year), and patients lacking an HLA-matched related donor (10% at 1 year). 49% of patients remained outpatient without hospitalization during the first 100 days post-transplant. Long-term outcomes: For the five most common diagnoses, the 4-year OS and PFS estimates were 41% and 32% for AML, 31% and 23% for MDS, 66% and 42% for CLL, 67% and 46% for NHL, and 79% and 46% for HL, respectively. Factors associated with mortality included a high or very high DRI (HR 2.11, 95% CI 1.65-2.69, p 〈 0.0001), age ≥65 years (HR 1.81, 95% CI 1.38-2.38, p 〈 0.0001), comorbidity index ≥3 (HR 1.47, 95% CI 1.15-1.87, p=0.002), and lack of an HLA-matched related donor (HR 1.27, 95% CI 1.02-1.57, p=0.034). Factors associated with disease relapse included a high or very high DRI (HR 1.75, 95% CI 1.38-2.23, p 〈 0.0001) and mixed chimerism, defined as 〈 95% donor CD3+ cells by day +90 (HR 1.50, 95% CI 1.20-1.89, p=0.0004). A reduced risk of relapse was observed in patients who developed chronic GVHD (HR 0.52, 95% CI 0.41-0.66, p 〈 0.0001) or acute GVHD (HR 0.66, 95% CI 0.47-0.92, p=0.034). Conclusions: TLI-ATG conditioning was well tolerated with a low risk of GVHD and NRM even among high-risk subgroups, including septuagenarians, patients with multiple comorbidities, and patients lacking an HLA-matched related donor. Nearly half of all patients remained outpatient during the first 100 days post-transplant. Long-term OS and PFS were seen across a range of hematologic malignancies, with particularly favorable outcomes for lymphoma patients, most of whom had failure of prior autologous HCT. Mixed chimerism correlates with the risk of relapse, and efforts are underway to augment donor chimerism and reduce relapse rates. Figure 1. Figure 1. Disclosures Miklos: Kite - Gilead: Consultancy, Research Funding; Pharmacyclics - Abbot: Consultancy, Research Funding; Novartis: Consultancy, Research Funding; Janssen: Consultancy, Research Funding; Adaptive Biotechnologies: Consultancy, Research Funding; Genentech: Research Funding. Muffly:Adaptive Biotechnologies: Research Funding; Shire Pharmaceuticals: Research Funding.

Abstract: Nonmyeloablative total lymphoid irradiation and antithymocyte globulin (TLI-ATG) conditioning is protective against graft-versus-host disease (GVHD), while retaining graft-versus-tumor activity across various hematologic malignancies. We report our comprehensive experience using TLI-ATG conditioning in 612 patients with hematologic malignancies who underwent allogeneic transplantation at Stanford University from 2001 to 2016. All patients received granulocyte colony-stimulating factor–mobilized peripheral blood grafts and cyclosporine and mycophenolate mofetil for GVHD prophylaxis. The median age was 60 years (range, 21-78), with a median follow-up of 6.0 years (range, 1.0-16.4). Common diagnoses included acute myeloid leukemia (AML; n = 193), myelodysplastic syndrome (MDS; n = 94), chronic lymphocytic leukemia (CLL; n = 80), non-Hodgkin lymphoma (NHL; n = 175), and Hodgkin lymphoma (HL; n = 35). Thirty-four percent of patients had a comorbidity index ≥3, 30% had a high to very high disease risk index, and 56% received unrelated donor grafts, including 15% with HLA-mismatched donors. Ninety-eight percent underwent transplant in the outpatient setting, and 57% were never hospitalized from days 0 through 100. The 1-year rates of nonrelapse mortality (NRM), grade II-IV acute GVHD, and extensive chronic GVHD were 9%, 14%, and 22%, respectively. The 4-year estimates for overall and progression-free survival were 42% and 32% for AML, 30% and 21% for MDS, 67% and 43% for CLL, 68% and 45% for NHL, and 78% and 49% for HL. Mixed chimerism correlated with the risk of relapse. TLI-ATG conditioning was well tolerated, with low rates of GVHD and NRM. Durable remissions were observed across hematologic malignancies, with particularly favorable outcomes for heavily pretreated lymphomas. Several efforts are underway to augment donor chimerism and reduce relapse rates while maintaining the favorable safety and tolerability profile of this regimen.

Abstract: The treatment landscape of relapsed/refractory (R/R) classic Hodgkin lymphoma (cHL) has evolved significantly over the past decade following the approval of brentuximab vedotin (BV) and the programmed death-1 (PD-1) inhibitors. We evaluated how outcomes and practice patterns have changed for R/R cHL patients who underwent autologous hematopoietic cell transplantation (AHCT) at our institution from 2011-2020 (N=183) compared to 2001-2010 (N=159) and evaluated prognostic factors for progression-free survival (PFS) and overall survival (OS) in both eras. OS was superior in the modern era (4-year estimates 89.1% vs 79.0%, HR 0.53, 95% CI 0.33-0.85, p=0.011) with a trend towards lower non-relapse mortality beyond 2 years post-transplant. Among patients who progressed after AHCT, 4-year post-progression survival increased from 43.3% to 71.4% in the modern era, reflecting increasing use of BV and the PD-1 inhibitors. In multivariable analysis for patients transplanted in the modern era, age ³45 years, primary refractory disease, and lack of complete remission pre-AHCT were associated with inferior PFS, while receipt of a PD-1 inhibitor-based regimen pre-AHCT was associated with superior PFS (HR 0.21, 95% CI 0.05-0.80, p=0.030). Extranodal disease at relapse was associated with inferior OS (HR 3.12, 95% CI 1.25-7.77, p=0.014). Our study demonstrates improved survival for R/R cHL after AHCT in the modern era attributed to more effective salvage regimens allowing for better disease control pre-AHCT and improved outcomes for patients who progressed after AHCT. Excellent outcomes were observed with PD-1 inhibitor-based salvage regimens pre-AHCT and support a randomized trial evaluating immunotherapy in the second line setting.