ALBERT

Description: Background: Autologous stem cell transplantation (ASCT) can be curative for patients (pts) with relapsed/refractory Hodgkin lymphoma (HL) who are sensitive to salvage therapy, particularly for pts who achieve a complete metabolic response (CMR) before ASCT. Pts who fail multiple salvage regimens have inferior outcomes and are generally considered poor candidates for ASCT. Recent studies suggest that anti-PD-1 monoclonal antibodies (mAbs) may restore sensitivity to cytotoxic therapy in HL pts with previously chemorefractory disease. We hypothesized that PD-(L)1 mAb-based salvage therapy may therefore also improve ASCT outcomes for HL pts who had failed salvage therapy. Methods: Medical records were reviewed at 13 US transplant centers to identify pts with a diagnosis of classic HL who failed at least 2 systemic therapies, were treated with a PD-1 or PD-L1 mAb (either alone or in combination) as 3rd line or later therapy, and subsequently underwent ASCT. Results: 44 eligible pts were identified. The median age was 33 (range 19-68). Pts received ABVD (39), AVD (2), brentuximab vedotin (BV) + AVD (1), Stanford V (1), or eBEACOPP (1) as 1st line therapy. 26 pts (59%) were refractory to 1st line treatment and 8 additional pts (18%) relapsed within 12 months. High-risk clinical features were observed frequently at 1st relapse including extranodal involvement (47%), B symptoms (27%), and advanced stage (64%). Pts received PD-(L)1 based treatment after failing 2 lines (32%), 3 lines (57%), or ≥4 lines (11%) of therapy. 32 pts (73%) were refractory to the line of therapy before PD-(L)1, 25 pts (57%) to 2 consecutive lines before PD-(L)1, and 10 pts (22%) to 3 consecutive lines before PD-(L)1. 16 pts (36%) were refractory to ≥2 salvage therapies immediately before PD-(L)1 therapy and 17 (39%) were refractory to all prior treatments. 39 pts (89%) received BV or a BV-based combination before ASCT. 67% were BV-refractory, including 86% of those receiving BV monotherapy. Pts received a median of 6 doses of a PD-(L)1 mAb (range 2-26) either as monotherapy (75%) or as part of a PD-1 based combination (25%). The median time from last dose of PD-(L)1 mAb to ASCT was 54 days (range 12-386). Best response to PD-(L)1-based therapy was CR (53%), PR (33%), SD (12%), or PD (2%). The median number of systemic therapies (including PD-(L)1) before ASCT was 4 (range 3-7) and 12 pts (27%) received intervening salvage therapy between PD-(L)1 treatment and ASCT. Pre-ASCT PET status was CR in 31 pts (70%), PR in 9 (18%), SD in 4 (9%), and PD in 1 (2%). There were no ASCT-related deaths. 2 pts developed BCNU pneumonitis and 1 developed engraftment syndrome. All 3 pts responded to steroids. 14 pts (32%) have received maintenance therapy with BV (4), a PD-1 mAb (8), or BV + PD-1 mAb (2). 4 pts (9%) received consolidative radiation. With a median post-ASCT follow-up of 12.2 months, progression-free survival (PFS) at 1 yr was 91% [95CI 75-97]. Notably, resistance to chemotherapy before PD-(L)1 therapy did not predict worse post-ASCT outcomes (see Table). 1-yr PFS was 90% for pts who were refractory to the 3 lines of therapy before PD-(L)1, 93% for pts refractory to ≥2 salvage therapies immediately before PD-(L)1, and 90% for pts refractory to all prior treatments. Favorable 1-yr PFS was also seen among pts who received PD-(L)1 as 4th or later line therapy (88% vs 100% for pts receiving PD-[L]1 as 3rd line, p=0.17) and among pts who failed to achieve a CMR on pre-ASCT PET (1-yr PFS 81% vs 96% for CMR pts, p=0.34). Lack of response to PD-(L)1 therapy (1-yr PFS 67% vs 96%, p=0.04), receipt of intervening salvage therapy (1-yr PFS 72% vs 100%, p=0.026), and increasing age (HR 1.11, p=0.015) were all significant predictors of inferior PFS. 1-yr overall survival was 100%. Conclusions: This high-risk cohort is heterogenous in terms of number of prior therapies and degree of chemoresistance, but excellent post-ASCT outcomes were observed among even the most heavily pre-treated, chemorefractory subgroups. Outcomes for PD-(L)1 responders were particularly favorable with a 1-yr PFS of 96%, suggesting that response to PD-(L)1 rather than prior chemotherapy may be the more important predictor of post-ASCT outcomes in this pt population. While longer follow-up is required to confirm the durability of these remissions, ASCT can be considered for HL pts responding to PD-(L)1 based salvage therapy, even if they have previously demonstrated a high degree of chemoresistance. Table Disclosures Nieto: Novartis: Research Funding; Astra-Zeneca: Research Funding; Affimed: Research Funding; Affimed: Consultancy. Byrne:Karyopharm: Research Funding. Maddocks:BMS: Research Funding; Novartis: Research Funding; Teva: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; Pharmacyclics: Membership on an entity's Board of Directors or advisory committees, Research Funding; Merck: Research Funding. Svoboda:BMS: Consultancy, Research Funding; Seattle Genetics: Consultancy, Research Funding; Merck: Research Funding; Incyte: Research Funding; Pharmacyclics: Consultancy, Research Funding; AstraZeneca: Consultancy; Celgene: Research Funding; Kyowa: Consultancy; Kite: Consultancy. McGuirk:Juno Therapeutics: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; ArticulateScience LLC: Other: Assistance with manuscript preparation; Pluristem Ltd: Research Funding; Gamida Cell: Research Funding; Kite Pharmaceuticals: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Novartis: Research Funding; Fresenius Biotech: Research Funding; Astellas: Research Funding; Bellicum Pharmaceuticals: Research Funding. Advani:Kyowa Kirin Pharmaceutical Developments, Inc.: Consultancy; Millennium: Research Funding; Janssen: Research Funding; Cell Medica, Ltd: Consultancy; Regeneron: Research Funding; Autolus: Consultancy, Membership on an entity's Board of Directors or advisory committees; AstraZeneca: Consultancy, Membership on an entity's Board of Directors or advisory committees; Stanford University: Employment, Equity Ownership; Agensys: Research Funding; Kura: Research Funding; Pharmacyclics: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Roche/Genentech: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Bayer: Consultancy, Membership on an entity's Board of Directors or advisory committees; Forty-Seven: Research Funding; Celmed: 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; Celgene: Research Funding; Takeda: Consultancy, Membership on an entity's Board of Directors or advisory committees; Merck: Research Funding; Seattle Genetics: Consultancy, Research Funding; Infinity Pharma: Research Funding; Gilead Sciences, Inc./Kite Pharma, Inc.: Consultancy, Membership on an entity's Board of Directors or advisory committees. Cohen:Seattle Genetics, Inc.: Consultancy, Research Funding; Bristol-Meyers Squibb Company: Research Funding; Takeda Pharmaceuticals North America, Inc.: Research Funding; Gilead/Kite: Consultancy; LAM Therapeutics: Research Funding; UNUM: Research Funding; Hutchison: Research Funding; Astra Zeneca: Research Funding; ASH: Research Funding; Lymphoma Research Foundation: Research Funding; Genentech, Inc.: Consultancy, Research Funding; Janssen Pharmaceuticals: Consultancy. Frigault:Xenetic: Consultancy; Foundation Medicine: Consultancy; Novartis: Consultancy; Nkarta: Consultancy; Juno/Celgene: Consultancy; Kite/Gilead: Honoraria; Incyte: Consultancy. Chen:Magenta: Consultancy; Takeda: Consultancy; Incyte: Consultancy; Kiadis: Consultancy; Abbvie: Consultancy. Lynch:Johnson Graffe Keay Moniz & Wick LLP: Consultancy; Rhizen Pharmaceuticals S.A: Research Funding; Juno Therapeutics: Research Funding; Takeda Pharmaceuticals: Research Funding; Incyte Corporation: Research Funding; T.G. Therapeutics: Research Funding. Smith:Seattle Genetics: Research Funding; Denovo Biopharma: Research Funding; Ayala (spouse): Research Funding; Merck Sharp & Dohme Corp: Consultancy, Research Funding; Acerta Pharma BV: Research Funding; Incyte Corporation: Research Funding; Ignyta (spouse): Research Funding; Genentech: Research Funding; Bristol-Myers Squibb (spouse): Research Funding; Portola Pharmaceuticals: Research Funding; Pharmacyclics: Research Funding; AstraZeneca: Membership on an entity's Board of Directors or advisory committees, Research Funding. Ho:Jazz Pharmaceuticals: Research Funding; Jazz Pharmaceuticals: Consultancy; Omeros Corporation: Membership on an entity's Board of Directors or advisory committees. Armand:Affimed: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Bristol-Myers Squibb: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Merck: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Sigma Tau: Research Funding; Infinity: Consultancy; Otsuka: Research Funding; Genentech: Research Funding; Pfizer: Consultancy; ADC Therapeutics: Consultancy; Tensha: Research Funding; Roche: Research Funding; Adaptive: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding. Herrera:Merck: Consultancy; BMS: Consultancy; Genentech: Research Funding; Adaptive Biotechnologies: Consultancy; Gilead Sciences: Research Funding; KiTE/Gilead: Consultancy; Genentech: Consultancy; Merck: Research Funding; Astra-Zeneca: Research Funding; Seattle Genetics: Consultancy; BMS: Research Funding; Seattle Genetics: Research Funding.

Description: Introduction Axicabtagene citoleucel (axi-cel) is a recently approved, highly effective treatment for relapsed and refractory aggressive B cell lymphomas. It is complicated by the occurrence of cytokine release syndrome (CRS) in 〉 90% of patients (Neelapu, Locke et al. 2017). CRS is characterized by high fevers and elevation in inflammatory markers such as C-reactive protein (CRP) and ferritin. It can progress to hypotension and end-organ damage. The clinical distinction between CRS and bacterial infections is virtually impossible. Procalcitonin (PCT) is FDA approved to aid in antibiotic management and stopping antibiotics in sepsis. It has been shown in several studies and meta-analyses to reduce antibiotic exposure without affecting mortality, including patients with cancer (Bouadma, Luyt et al. 2010, Schuetz, Chiappa et al. 2011, Sedef, Kose et al. 2015). Methods We sought to evaluate the utility of PCT as an infectious biomarker in patients undergoing commercial treatment with axi-cel. Patient data was collected retrospectively from two institutions and analyzed for clinical and laboratory characteristics, presence of documented infections, and presence and severity of cytokine release syndrome. PCT levels were drawn per the treating team's discretion based on clinical changes (new onset fever, new onset hypotension, requirement of vasopressors, change in level of care). Results A total of 30 patients received axi-cel for relapsed and refractory aggressive B-cell lymphoma and had PCT levels checked during their admission (Table 1). Median age was 61.5 years. Median baseline CRP and ferritin on day of infusion were 22.9 mg/L and 654 ng/mL, respectively. All patients had febrile episodes and evidence of at least grade I CRS by Lee criteria. Median duration of CRS was 6 days. Twenty-two patients (73.3%) had grade 2 or higher CRS. Median maximal temperature was 39.5 0C with a median duration of 5 days. Median number of days till first fever was 1 and median neutrophil count on day of first fever (〉 38 0C) was 1475/mm3. Twenty-seven (90%) of the patients were on levofloxacin prophylaxis. Eight patients (26.7%) had an absolute neutrophil count (ANC) of less than 500/mm3 on the day of first fever. All but one patient (97%) were started on intravenous antibiotics during their admission. None of the patients had positive blood cultures. One patient had C. difficile infection and one patient had invasive sinusitis with mucormycosis. The timing of these infections did not correspond to the diagnosis of these infections. Median PCT was 0.86 ng/mL. Twelve patients (40%) had values below the cut-off for bacterial infections. Two of these patients required vasopressors. Three patients expired (10%). Two had progressive disease and one had an invasive fungal infection. Figure 1 shows one patient (panel A) who had normal PCT during their CRS episode and another who had abnormal ones. Discussion Axi-cel is a novel and promising therapy for treatment of relapsed and refractory aggressive B-cell lymphomas. Therapy is complicated by occurrence of CRS in 94% of patients, which can be fatal if not properly identified and managed. CRS can mimic sepsis and patients are frequently placed on broad-spectrum intravenous antibiotics, inducing risk for multi-drug resistant organisms and C. difficile infections. Unlike ferritin and CRP, PCT is typically only elevated in settings of bacterial infections, trauma and surgery and is FDA approved to be utilized in a treatment algorithm for earlier discontinuation of antibiotics in septic patients. It has not been studied in CRS. PCT was checked per the treating team's discretion and the trend was not followed for most of these patients. We herein hypothesize that PCT does not follow the same kinetics of other inflammatory markers frequently interrogated and may serve as a way to distinguish infection from CRS in this population, where 100% of patients experienced CRS and fevers, but 40% had normal PCT levels. The utility of PCT in antibiotic stewardship and the cut-off of 0.5 ng/mL should be further explored to guide antibiotic use in this population. Disclosures Jacobson: Pfizer: Consultancy; Kite: Consultancy; Humanigen: Consultancy; Novartis: Consultancy; Precision Bioscience: Consultancy; Bayer: Consultancy. Abramson:Merck: Consultancy; Juno Therapeutics: Consultancy; Celgene: Consultancy; Humanigen: Consultancy; Seattle Genetics: Consultancy; Gilead: Consultancy; Amgen: Consultancy; Novartis: Consultancy; Bayer: Consultancy; Karyopharm: Consultancy; Verastem: Consultancy. Kline:Merck: Honoraria, Research Funding; iTeos: Research Funding. Cohen:BioInvent: Consultancy; Janssen: Research Funding; Infinity Pharmaceuticals: Consultancy, Membership on an entity's Board of Directors or advisory committees; Infinity Pharmaceuticals: Consultancy, Membership on an entity's Board of Directors or advisory committees; Seattle Genetics: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees; AbbVie: 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; Bristol-Myers Squibb: Research Funding; Bristol-Myers Squibb: Research Funding; AbbVie: Consultancy, Membership on an entity's Board of Directors or advisory committees; Millennium: Consultancy, Membership on an entity's Board of Directors or advisory committees; Janssen: Research Funding; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Millennium: Consultancy, Membership on an entity's Board of Directors or advisory committees; Pharmacyclics: Consultancy, Membership on an entity's Board of Directors or advisory committees; Takeda: Research Funding; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; BioInvent: Consultancy; Seattle Genetics: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Pharmacyclics: Consultancy, Membership on an entity's Board of Directors or advisory committees; Takeda: Research Funding. Gopal:Teva: Research Funding; Asana: Consultancy; Brim: Consultancy; Aptevo: Consultancy; Merck: Research Funding; Janssen: Consultancy, Research Funding; Spectrum: Research Funding; Takeda: Research Funding; BMS: Research Funding; Pfizer: Research Funding; Seattle Genetics: Consultancy, Research Funding; Gilead: Consultancy, Research Funding; Incyte: Consultancy. Acharya:Teva: Honoraria; Juno Therapeutics: Research Funding. Jaglowski:Novartis Pharmaceuticals Corporation: Consultancy, Research Funding; Juno: Consultancy; Kite Pharma: Consultancy, Research Funding.

Description: Background: Targeting BCMA (B-cell maturation factor) with chimeric antigen receptor (CAR) T cells has shown great success in the treatment of multiple myeloma (MM), but is limited by heterogeneous antigen expression and imminent antigen escape of tumor cells. Combinatorial antigen targeting may help address these challenges. Taking the naturally occurring receptor-ligand pairs as a model, we designed monomeric and trimeric APRIL- (A proliferation-inducing ligand) based CARs targeting BCMA and TACI (transmembrane activator and CAML interactor) simultaneously. Methods: The following 2nd generation CARs were designed to target BCMA and TACI concurrently: membrane-tethered truncated APRIL monomer ("APRIL-CAR") and three truncated and fused APRIL monomers ("TriPRIL-CAR"). A single chain variable fragment-based anti(α)-BCMA CAR served as control. CAR multimerization and binding affinity to BCMA and TACI were characterized. In vitro effector function was compared by cytotoxic potency, activation (CD69), degranulation (CD107a), cytokine production and proliferation in response to target antigens. In vivo anti-tumor efficiency was assessed in a xenograft mouse model of MM. Results: CAR T cell manufacturing of all three constructs was accomplished successfully (transduction efficiency 46-78%) from three different donors. Western blot analysis of CARs showed multimerized forms of the TriPRIL and α-BCMA CAR, while only the monomeric form of the APRIL CAR was detected. Binding affinity to soluble BCMA and TACI was higher for the TriPRIL CAR compared to the APRIL CAR. Evaluating the cytotoxic potential, activation and degranulation kinetics as well as long-term proliferation against a panel of BCMA and/or TACI positive target cells, the TriPRIL CAR T cells outperformed the APRIL CAR T cells. All three CAR constructs demonstrated robust antigen-specific production of Th1-type cytokines, like Il-2, IFNƔ, GM-CSF and TNFα. Next, we performed an in vivo stress test, engrafting NSG mice with high tumor burden of MM.1s myeloma cells. The TriPRIL and α-BCMA CAR T cells were able to eradicate the tumors while the APRIL CAR T cells only led to a stabilization of tumor burden. In vivo studies with a mixed antigen population aiming at modeling heterogeneous antigen expression and antigen escape are ongoing. Conclusion: Our APRIL-based chimeric antigen receptors were able to redirect T cell cytotoxicity to both BCMA and TACI positive tumor cells. Since both these receptors are consistently up-regulated on malignant plasma cells this is an attractive method to target MM. Furthermore, we found that using a trimeric form of APRIL rather than monomeric form as the CAR binding domain increased recognition of MM antigens in vitro and in vivo. Disclosures Maus: crispr therapeutics: Consultancy, Research Funding; adaptimmune: Consultancy; novartis: Consultancy; kite therapeutics: Consultancy, Research Funding; windmil therapeutics: Consultancy; agentus: Consultancy, Research Funding.

Description: Chimeric antigen receptor (CAR) T cells have emerged as a promising class of cell-based immunotherapy in refractory malignancies. Neurotoxicity represents a common and potentially life-threatening adverse effect of CAR T cells, and clinical experience is limited. Here, we describe the clinical presentation and management of 25 adult patients who presented with neurotoxic syndromes after CAR T-cell therapy at the Massachusetts General Hospital. This cohort includes 24 patients treated with CD19-directed CAR T cells for non-Hodgkin lymphoma (n = 23) and acute lymphoblastic leukemia (n = 1), and 1 patient treated with α-fetoprotein–directed CAR T cells for hepatocellular carcinoma (n = 1). Twelve of the 25 patients (48%) developed grade 1-2 neurotoxicity and 13 patients (52%) presented with grade 3-4 neurotoxicity. We found that lower platelet counts at time of CAR T-cell infusion were associated with more severe neurotoxicity (P = .030). Cytokine release syndrome occurred in 24 of 25 patients (96%). Serum levels of ferritin peaked with onset of neurologic symptoms, and higher ferritin levels were associated with higher neurotoxicity grade. Grade 3-4 neurotoxicity correlated negatively with overall survival (OS) (P = .013). Median OS of the entire cohort was 54.7 weeks. Eight patients (32%) with grade 3-4 neurotoxicity were deceased at database closure, whereas none died with neurotoxicity grade 1-2. High pretreatment lactate dehydrogenase was frequently encountered in lymphoma patients with grade 3-4 neurotoxicity and correlated negatively with progression-free survival (P = .048). We did not find evidence that steroid use ≥7 days altered the patient’s outcome when compared with

Description: Introduction: CD19 CAR T cells lead to durable responses in 40% of r/r aggressive B cell NHL patients. We performed a multicenter retrospective study of axicabtagene ciloleucel given in a real world setting where eligibility/management considerations may diverge from clinical trials. We evaluate efficacy and safety, and patient/disease factors associated with response and toxicity. Methods: Patient and treatment characteristics were summarized descriptively. Response and toxicity were reported with 95% exact binomial CIs. CyTOF was performed on frozen PBMCs using 38 metal-tagged mAbs. Multiplex IF was performed on FFPE tissue with standard, primary Abs sequentially, paired with a unique fluorochrome per published protocols. Standard IHC was done on FFPE whole tissue. Results: In total, 76 patients, median age 64, were included (Table 1). The majority had an ECOG PS ≤ 2. Twenty-one percent of patients had double/triple hit cytogenetics. Nearly half had an IPI ≥3 at treatment. Nearly 1/3 had a prior autologous transplant, 25% had prior ibrutinib, and 11% had prior lenalidomide. Twelve percent had bulky disease and 36% received bridging therapy following pheresis. Seventy-three patients were evaluable for response (Table 2). At 4m median f/u, best ORR and CRR was 64% and 41% among those treated. Six patients had 6m f/u, all PRs at 1m: 3 converted to CR and 3 had PD. Eleven patients (13%) were pheresed but not treated due to PD (6), infection (2), or non-conforming cells (3). By ITT analysis, the ORR and CRR were 57% and 36%. OS at 4m among those treated was 84%; PFS will be calculated with longer f/u. In univariate analysis, PS, tumor bulk, IPI, baseline CRP and prior ibrutinib were significantly associated with lack of response (Table 3). There was no association between response and double/triple hit cytogenetics, grade 3+ CRS or NT, or the use of tocilizumab/steroids. Among treated patients, 96% experienced CRS; in 17% this was ≥ grade 3. Two patients died from CRS (3%). Median time to onset was 1d; median duration was 6d (0-14d). NT was seen in 76% of patients; in 38% this was ≥ grade 3. One case of NT was fatal. Median time to onset was 5d; median duration was 8d (0-34d). Tocilizumab and steroids were given to 67% and 78% of patients. ICU care occurred in 30% of patients. Eleven treated patients have died: 6 from PD and 5 from toxicity. In univariate analysis, peak ferritin was associated with grade 3+ CRS and NT; peak ALC was associated with grade 3+ CRS, and peak CRP and prior autologous transplant were associated with grade 3+ NT (Table 4). Three of 4 patients who had a biopsy with CD19 staining after relapse were positive (Fig 1). All 3 patients with PDL1+ tumors were refractory to CAR T cell therapy. Multiplex IF and IHC were performed on 2 primary refractory patients at progression (Fig 1). One was CD19-/PDL1+; multiplex IF showed an abundance of CAR+ T-cells (Fig 1A,B). The second was CD19+/PDL1- and multiplex IF showed no CAR+ T-cells (Fig 1C,D). CyTOF analysis of PBMCs at serial timepoints was performed on 6 patients (4 CRs, 1 PD, 1 PD after CR)(Fig 2, Table 5). Peak CAR T cell levels were seen at day 7 in all patients with increased expression of PD1, 41BB, and Ki67, as well as CC3 indicating apoptosis, followed by a reduction in CAR T cells by day 14. Immune subsets that associate with response will be evaluated and reported. Results from additional patients and longer f/u will be presented. Conclusion: Retrospective analysis of a multicenter cohort treated in the real world with axi-cel reveals important distinctions from ZUMA-1. The ORR and CR rate are lower than the 82% and 54% reported on ZUMA-1. This may reflect inclusion of sicker patients with a poorer PS, and/or with different histologies (ie transformation from non-FL). Outcomes were significantly worse in high risk lymphomas, reflected by IPI, PS, tumor bulk, and baseline CRP. Rates of CRS and NT were similar to ZUMA-1, but toxicity was not associated with tumor bulk or response. It was associated with higher peak inflammatory markers and ALC, which may reflect peak CAR T cell levels, as shown previously. Progression biopsies highlight 3 potential resistance mechanisms: loss of target antigen, an inhibitory tumor/TME, and lack of CAR T cell tumor infiltration. Immunomodulatory molecules on CAR T cells that may affect their activity and survival are upregulated early. This suggests that unique combination approaches are necessary for specific patients/tumors. Disclosures Jacobson: Precision Bioscience: Consultancy; Kite: Consultancy; Pfizer: Consultancy; Bayer: Consultancy; Humanigen: Consultancy; Novartis: Consultancy. Rodig:Merck: Research Funding; Affimed: Research Funding; Bristol Myers Squibb: Research Funding; KITE: Research Funding. Maus:novartis: Consultancy; agentus: Consultancy, Research Funding; crispr therapeutics: Consultancy, Research Funding; kite therapeutics: Consultancy, Research Funding; windmil therapeutics: Consultancy; adaptimmune: Consultancy. Chen:Incyte: Consultancy, Membership on an entity's Board of Directors or advisory committees; Magenta Therapeutics: Consultancy; REGiMMUNE: Consultancy; Takeda Pharmaceuticals: Consultancy. Abramson:Verastem: Consultancy; Amgen: Consultancy; Merck: Consultancy; Karyopharm: Consultancy; Humanigen: Consultancy; Bayer: Consultancy; Gilead: Consultancy; Celgene: Consultancy; Seattle Genetics: Consultancy; Novartis: Consultancy; Juno Therapeutics: Consultancy. Kline:iTeos: Research Funding; Merck: Honoraria, Research Funding. Cohen:Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees; AbbVie: Consultancy, Membership on an entity's Board of Directors or advisory committees; Infinity Pharmaceuticals: Consultancy, Membership on an entity's Board of Directors or advisory committees; Infinity Pharmaceuticals: Consultancy, Membership on an entity's Board of Directors or advisory committees; Seattle Genetics: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Janssen: Research Funding; Bristol-Myers Squibb: Research Funding; Bristol-Myers Squibb: Research Funding; Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees; Janssen: Research Funding; Millennium: Consultancy, Membership on an entity's Board of Directors or advisory committees; Millennium: 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, Research Funding; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Pharmacyclics: Consultancy, Membership on an entity's Board of Directors or advisory committees; Takeda: Research Funding; Pharmacyclics: Consultancy, Membership on an entity's Board of Directors or advisory committees; BioInvent: Consultancy; Seattle Genetics: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Takeda: Research Funding; BioInvent: Consultancy. Jaglowski:Novartis Pharmaceuticals Corporation: Consultancy, Research Funding; Kite Pharma: Consultancy, Research Funding; Juno: Consultancy. Smith:Merck Sharp and Dohme Corp.: Consultancy, Research Funding; Acerta Pharma BV: Research Funding; Pharmacyclics: Research Funding; Genentech: Research Funding; Incyte Corporation: Research Funding; Portola Pharmaceuticals: Research Funding; Seattle Genetics: Research Funding. Maloney:Janssen Scientific Affairs: Honoraria; Seattle Genetics: Honoraria; Juno Therapeutics: Research Funding; Roche/Genentech: Honoraria; GlaxoSmithKline: Research Funding. Gopal:Spectrum: Research Funding; Seattle Genetics: Consultancy, Research Funding; Merck: Research Funding; Janssen: Consultancy, Research Funding; Takeda: Research Funding; Gilead: Consultancy, Research Funding; Pfizer: Research Funding; BMS: Research Funding; Brim: Consultancy; Teva: Research Funding; Aptevo: Consultancy; Incyte: Consultancy; Asana: Consultancy. Acharya:Teva: Honoraria; Juno Therapeutics: Research Funding.

Description: Introduction: Anti-PD-1 monoclonal antibodies (mAbs) are highly active in relapsed/refractory classical Hodgkin lymphoma (cHL), but most patients (pts) will still relapse. Given this, allogeneic stem cell transplantation (alloHSCT) remains an important option for pts after PD-1 blockade, as it offers the possibility of cure. Prior reports have suggested that alloHSCT after PD-1 mAbs may be associated with severe immune-related complications including acute graft-versus-host disease (GVHD), veno-occlusive disease (VOD) and cytokine release/febrile non-infectious syndrome (CRS). Prior studies of alloHSCT after PD-1 blockade in cHL have been limited by the small number of pts and short follow-up, preventing an accurate assessment of long-term outcomes and complications, risk factors for early toxicity, and the impact of transplant strategies such as choice of GVHD prophylaxis. We therefore assembled a large retrospective international cohort of cHL pts who underwent alloHSCT after PD-(L)1 blockade to better answer these questions, including an assessment of the impact of post-transplant cyclophosphamide (PTCy) on efficacy and toxicity. Methods: Medical records and databases were reviewed at 26 European and United States transplant centers to identify pts with cHL who underwent an alloHSCT any time after receiving a PD-1 or PD-L1 mAb. Response assessment was performed by local investigators according to Lugano 2014 criteria. Overall survival (OS), progression-free survival (PFS), cumulative incidence (CumInc) of relapse (CIR), non-relapse mortality (NRM), acute (a) and chronic (c) GVHD were estimated, as was the association between baseline variables and these outcomes. Results: Between 2014 and 2019, 150 pts were identified who underwent alloHSCT after a median of 10 (range, 1-74) doses of nivolumab (n=118), pembrolizumab (n=31), or avelumab (n=1). The median age was 31 (range 17-68) and pts had received a median of 4 (range, 2-11) lines of therapy prior to PD-(L)1 blockade. 138 pts (92%) had failed BV and 111 (74%) autologous HSCT. The best overall response to PD-(L)1 mAbs was CR for 62 pts (41%), PR for 55 (37%), SD for 17 (11%), PD for 15 (10%) and unknown for 1 (1%). Median time from last dose of PD-(L)1 mAb to alloHSCT was 80 days (range, 17-756) with 70 pts (47%) receiving intervening systemic therapy. At alloHSCT, 90 pts were in CR (60%), 45 in PR (30%), 5 in SD (3%), and 10 in PD (7%). Donors were haploidentical (n=71, 47%), matched sibling (n=29, 19%), matched unrelated (n=39, 26%), mismatched unrelated (n=7, 5%), cord blood (n=2, 1%), or unknown (n=2, 1%). Stem cell source was bone marrow (n=38, 25%), peripheral blood (n=110, 73%), or cord blood (n=2, 1%). GVHD prophylaxis included PTCy in 88 pts (59%) (69/71 (97%) with haploidentical donors; 19/79 (24%) with other donors). With a median post-alloHSCT follow-up for survivors of 23.8 months (range, 1-67), the 2y OS and PFS were 79% (95CI 71-86%) and 65% (95CI 55-73%), respectively, while the 2y CumIncs of relapse and NRM were 21% (95CI 13-29%) and 14%, (95CI, 8-22%), respectively (Fig. 1A-B). 27 pts have died, 3 due to disease and 24 to NRM, including aGVHD (n=7) and VOD (n=2). Veno-occlusive disease (VOD) occurred in 5 pts (day 100 CumInc 4%) and 29 pts (19%) developed CRS (grade 1 n=16; grade 2 n=7; grade 3 n=4; grade 4 n=2). The 6-month CumIncs of grade 2-4, grade 3-4 and grade 4 aGVHD were 39%, 16% and 8%, respectively. Hyperacute GVHD (onset ≤ 14 days after alloHSCT) occurred in 4% of pts and was fatal in 2 pts. The 2y CumInc of cGVHD was 45%. Neither receipt of 〉 10 doses (median) of anti-PD-(L)1 mAb nor undergoing alloHSCT ≤80 days (median) after last dose of PD-(L)1 mAb were associated with PFS or OS. However, pts with a shorter time to transplant (≤80 days) appeared to have a higher risk of severe (grade 3-4) aGVHD (6m CumInc 24% vs 9%, p=0.006). Recipients of PTCy in this cohort had lower 2y CumIncs of cGVHD (34% vs 58%, p=0.01) and relapse (12% vs 31%, p=0.02), superior 2y PFS (76% vs 54%, p=0.015), and similar rates of severe aGVHD (15% vs 18%, p=0.5), 2y NRM (12% vs 16%, p=0.5), and 2y OS (82% vs 78%, p=0.6). Conclusions: With extended follow-up of a large international cohort, our results argue that alloSCT performed after PD-(L)1 mAbs is a feasible strategy associated with an excellent PFS and a very low CIR for this disease. The use of PT-Cy appears to be associated with improved outcomes and may at present represent the optimal transplant strategy in this pt population. Figure Disclosures Corradini: kite: Honoraria; Abbvie: Honoraria; Servier: Honoraria; Sanofi: Honoraria; Takeda: Honoraria; Roche: Honoraria; Novartis: Honoraria; KiowaKirin: Honoraria; Janssen: Honoraria; Gilead: Honoraria; Daiichi Sankyo: Honoraria; Celgene: Honoraria; Amgen: Honoraria. Ho:Jazz Pharmaceuticals: Research Funding; Jazz Pharmaceuticals: Consultancy; Omeros Corporation: Membership on an entity's Board of Directors or advisory committees. Jaglowski:Kite: Consultancy, Other: advisory board, Research Funding; Novartis: Consultancy, Other: advisory board, Research Funding; Juno: Consultancy, Other: advisory board; Unum Therapeutics Inc.: Research Funding. Herrera:Adaptive Biotechnologies: Consultancy; Bristol-Myers Squibb: Consultancy, Research Funding; Gilead Sciences: Consultancy, Research Funding; Seattle Genetics: Consultancy, Research Funding; AstraZeneca: Research Funding; Merck: Consultancy, Research Funding; Genentech, Inc.: Consultancy, Research Funding; Pharmacyclics: Research Funding; Immune Design: Research Funding; Kite Pharma: Consultancy, Research Funding. Blaise:Jazz Pharmaceuticals: Honoraria; Sanofi: Honoraria; Pierre Fabre medicaments: Honoraria; Molmed: Consultancy, Honoraria. Hamadani:Pharmacyclics: Consultancy; Sanofi Genzyme: Research Funding, Speakers Bureau; Merck: Research Funding; Otsuka: Research Funding; Janssen: Consultancy; Medimmune: Consultancy, Research Funding; ADC Therapeutics: Consultancy, Research Funding; Takeda: Research Funding; Celgene: Consultancy. Ansell:LAM Therapeutics: Research Funding; Affimed: Research Funding; Affimed: Research Funding; Trillium: Research Funding; Trillium: Research Funding; Seattle Genetics: Research Funding; Mayo Clinic Rochester: Employment; Mayo Clinic Rochester: Employment; Bristol-Myers Squibb: Research Funding; Affimed: Research Funding; Mayo Clinic Rochester: Employment; Seattle Genetics: Research Funding; Seattle Genetics: Research Funding; Affimed: Research Funding; LAM Therapeutics: Research Funding; Mayo Clinic Rochester: Employment; Seattle Genetics: Research Funding; LAM Therapeutics: Research Funding; Bristol-Myers Squibb: Research Funding; Mayo Clinic Rochester: Employment; Affimed: Research Funding; Trillium: Research Funding; Trillium: Research Funding; Bristol-Myers Squibb: Research Funding; Regeneron: Research Funding; Affimed: Research Funding; Mayo Clinic Rochester: Employment; Bristol-Myers Squibb: Research Funding; Regeneron: Research Funding; Regeneron: Research Funding; Regeneron: Research Funding; Seattle Genetics: Research Funding; Regeneron: Research Funding; Bristol-Myers Squibb: Research Funding; Seattle Genetics: Research Funding; Seattle Genetics: Research Funding; Seattle Genetics: Research Funding; LAM Therapeutics: Research Funding; Regeneron: Research Funding; Affimed: Research Funding; Regeneron: Research Funding; Bristol-Myers Squibb: Research Funding; Trillium: Research Funding; LAM Therapeutics: Research Funding; Bristol-Myers Squibb: Research Funding; Mayo Clinic Rochester: Employment; Mayo Clinic Rochester: Employment; Regeneron: Research Funding; Trillium: Research Funding; Bristol-Myers Squibb: Research Funding; Mayo Clinic Rochester: Employment; LAM Therapeutics: Research Funding; LAM Therapeutics: Research Funding; LAM Therapeutics: Research Funding; Regeneron: Research Funding; LAM Therapeutics: Research Funding; Trillium: Research Funding; Trillium: Research Funding; Affimed: Research Funding; Bristol-Myers Squibb: Research Funding; Seattle Genetics: Research Funding; Trillium: Research Funding; Affimed: Research Funding. Nieto:Astra-Zeneca: Research Funding; Affimed: Consultancy; Affimed: Research Funding; Novartis: Research Funding. Feldman:Celgene: Honoraria, Research Funding, Speakers Bureau; Seattle Genetics: Consultancy, Honoraria, Other: Travel expenses, Speakers Bureau; Pfizer: Research Funding; AbbVie: Honoraria, Other: Travel expenses, Speakers Bureau; Portola Pharma: Research Funding; Kite Pharma: Honoraria, Other: Travel expenses, Speakers Bureau; Janssen: Honoraria, Speakers Bureau; Pharmacyclics: Honoraria, Other: Travel expenses, Speakers Bureau; Kyowa Hakko Kirin: Research Funding; Eisai: Research Funding; Bayer: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Amgen: Research Funding; Cell Medica: Research Funding; Roche: Research Funding; Corvus: Research Funding; Viracta: Research Funding; Trillium: Research Funding; Roche: Research Funding; Takeda: Honoraria, Speakers Bureau. McGuirk:ArticulateScience LLC: Other: Assistance with manuscript preparation; Bellicum Pharmaceuticals: Research Funding; Kite Pharmaceuticals: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Gamida Cell: Research Funding; Pluristem Ltd: Research Funding; Juno Therapeutics: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Astellas: Research Funding; Novartis: Research Funding; Fresenius Biotech: Research Funding. Mohty:Jazz Pharmaceuticals: Honoraria, Research Funding. Stamatoulas Bastard:Celgene: Honoraria; Takeda: Consultancy. Houot:Bristol Myers Squibb: Honoraria; Merck Sharp Dohme: Honoraria. Manson:Bristol Myers Squibb: Honoraria. Orvain:Incyte: Honoraria; Novartis: Honoraria; Jazz Pharmaceuticals: Other: Travel & accommodations; Pfizer: Other: Travel & accommodations. Bouabdallah:Roche: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Takeda: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Frigault:Novartis: Consultancy; Kite/Gilead: Honoraria; Nkarta: Consultancy; Incyte: Consultancy; Juno/Celgene: Consultancy; Foundation Medicine: Consultancy; Xenetic: Consultancy. Chen:Takeda: Consultancy; Kiadis: Consultancy; Magenta: Consultancy; Abbvie: Consultancy; Incyte: Consultancy. Lynch:T.G. Therapeutics: Research Funding; Rhizen Pharmaceuticals S.A: Research Funding; Takeda Pharmaceuticals: Research Funding; Juno Therapeutics: Research Funding; Incyte Corporation: Research Funding; Johnson Graffe Keay Moniz & Wick LLP: Consultancy. Smith:AstraZeneca: Membership on an entity's Board of Directors or advisory committees, Research Funding; Merck Sharp & Dohme Corp: Consultancy, Research Funding; Acerta Pharma BV: Research Funding; Portola Pharmaceuticals: Research Funding; Pharmacyclics: Research Funding; Bristol-Myers Squibb (spouse): Research Funding; Denovo Biopharma: Research Funding; Genentech: Research Funding; Ignyta (spouse): Research Funding; Incyte Corporation: Research Funding; Ayala (spouse): Research Funding; Seattle Genetics: Research Funding. Byrne:Karyopharm: Research Funding. Cohen:Hutchison: Research Funding; Astra Zeneca: Research Funding; Janssen Pharmaceuticals: Consultancy; Seattle Genetics, Inc.: Consultancy, Research Funding; Bristol-Meyers Squibb Company: Research Funding; Takeda Pharmaceuticals North America, Inc.: Research Funding; Gilead/Kite: Consultancy; Genentech, Inc.: Consultancy, Research Funding; UNUM: Research Funding; ASH: Research Funding; LAM Therapeutics: Research Funding; Lymphoma Research Foundation: Research Funding. Svoboda:AstraZeneca: Consultancy; Celgene: Research Funding; Incyte: Research Funding; Pharmacyclics: Consultancy, Research Funding; Kyowa: Consultancy; Merck: Research Funding; BMS: Consultancy, Research Funding; Seattle Genetics: Consultancy, Research Funding. Santoro:Bayer: Consultancy, Speakers Bureau; MSD: Speakers Bureau; Arqule: Consultancy, Speakers Bureau; Pfizer: Consultancy, Speakers Bureau; AstraZeneca: Speakers Bureau; Gilead: Consultancy, Speakers Bureau; Servier: Consultancy, Speakers Bureau; Takeda: Speakers Bureau; BMS: Speakers Bureau; Roche: Speakers Bureau; Abb-Vie: Speakers Bureau; Amgen: Speakers Bureau; Celgene: Speakers Bureau; Novartis: Speakers Bureau; BMS: Consultancy; Lilly: Speakers Bureau; Sandoz: Speakers Bureau; Eisai: Consultancy, Speakers Bureau. Armand:Sigma Tau: Research Funding; Otsuka: Research Funding; Pfizer: Consultancy; ADC Therapeutics: Consultancy; Tensha: Research Funding; Affimed: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Roche: Research Funding; Adaptive: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Bristol-Myers Squibb: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Merck: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Infinity: Consultancy; Genentech: Research Funding. Zinzani:Roche: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Portola: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Celgene: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Immune Design: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Sandoz: Membership on an entity's Board of Directors or advisory committees; Servier: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; BMS: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Janssen-Cilag: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Gilead: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Celltrion: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Sanofi: Consultancy; Eusapharma: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Verastem: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; MSD: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Kyowa Kirin: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; TG Therapeutics: Honoraria, Speakers Bureau. Carlo-Stella:Servier: Consultancy, Honoraria, Other: Travel, accommodations; Genenta Science srl: Consultancy; Boehringer Ingelheim: Consultancy; F. Hoffmann-La Roche Ltd: Honoraria, Other: Travel, accommodations, Research Funding; Novartis: Consultancy, Research Funding; ADC Therapeutics: Consultancy, Other: Travel, accommodations, Research Funding; Sanofi: Consultancy, Research Funding; Rhizen Pharmaceuticals: Research Funding; Celgene: Research Funding; Amgen: Honoraria; AstraZeneca: Honoraria; Janssen Oncology: Honoraria; MSD: Honoraria; BMS: Honoraria; Janssen: Other: Travel, accommodations; Takeda: Other: Travel, accommodations.

Description: Key Points ICOS-based CARs program bipolar TH17/TH1 cells with augmented effector function and in vivo persistence. The expression of selected CAR endodomains can program T cells for their subsequent differentiation fates and effector functions.

Description: Background: CAR-T cells have led to a revolution in the treatment of advanced hematologic malignancies. Since these cells target antigens that are expressed on the cellular surface, it is imperative that there is near ubiquitous tumor expression with minimal expression vital human tissues. Finding targets with these characteristics in myeloid malignancies has been challenging. Typical markers expressed on the surface of AML are also expressed on essential innate immune effector cells (e.g. neutrophils) which, if targeted, could lead to prolonged absence of this immune arm, which is not survivable or replaceable. Current approaches rely on the use of CAR-T cells against common myeloid targets (e.g. CD123, CD33) as an ablative strategy with a planned allogeneic stem cell transplant rescue to eradicate the CAR-T cells afterwards. These solutions have resulted in significant toxicity with several deaths resulting from CD123-targeted CAR-T cells. Another approach has involved gene editing donor progenitor cells to delete CD33, repopulation of the marrow with these CD33 negative cells, and then treatment with CD33-targeted CAR-T cells. (Kim, Cell 2018). However, this approach is challenging, costly, and genomic editing of stem cells remains a concern. CD70 is an immune checkpoint found on antigen presenting cells and activated T cells. Multiple studies have shown a strong degree of expression on AML blasts and leukemic stem cells, with minimal normal tissue expression (Perna, Cell 2017, Riether J Exp Med 2017). A Phase 1 study of a CD70 targeted antibody drug conjugate in combination with azacitidine (which has been shown to increase CD70 expression on leukemic stem cells) for untreated AML patients has shown impressive results (Blood 2018 132:2680, Blood 2017 130:2652). Based on these findings, we explored CD70-targeting CARs for the treatment of AML. Methods: Based on our success with a trimeric ligand-based CAR of another TNFα family member, APRIL, for multiple myeloma (Schmidt Blood 2018 132:2059), we generated monomeric and trimeric second-generation ligand-based CAR constructs to target CD70 on AML. In vitro effector function was compared by cytotoxic potency and cytokine production. In vivo anti-tumor efficiency was assessed in a xenograft mouse model of AML. Effect of surface CD70 expression on AML cell lines after co-culture with azacitidine was assessed. Results: CAR T cell manufacturing of both constructs was accomplished successfully (transduction efficiency 70-93%) from three different healthy donors with no apparent fratricide. CD70 CARs were efficacious in in vitro cytotoxicity assays targeting an AML cell line Molm13. Unexpectedly, monomeric CD70 targeted CAR-T cells were superior to trimeric in cytotoxicity assays and, thus, were carried forward for in vivo assays. Next, we treated NSG mice that had been engrafted with Molm13 and demonstrated a substantial dose-dependent therapeutic effect with prolonged survival of CAR treated mice compared to those treated with untransduced T-cells (UTD). Treated mice demonstrated a CAR-T robust expansion in the peripheral blood assessed by flow cytometry that was commensurate with individual animal treatment responses. Bone marrow from these mice revealed substantially reduced CD70 in all groups. Preliminary in vitro co-culture of AML cells with azacitidine showed increased CD70 expression. Conclusion: CD70 based CAR-T targeting of AML is effective in vitro and in vivo. Combination treatment with azacitidine may increase target antigen expression and lead to synergistic activity and represents a viable therapeutic strategy that warrants further investigation. Treatment of AML engrafted NSG mice with CD70 CAR-T cells in conjunction with azacitidine is ongoing. Disclosures Frigault: Xenetic: Consultancy; Novartis: Consultancy; Juno/Celgene: Consultancy; Foundation Medicine: Consultancy; Incyte: Consultancy; Nkarta: Consultancy; Kite/Gilead: Honoraria. Maus:INFO PENDING: Other: INFO PENDING.