ALBERT

Description: We explore a novel and spatially extensive dataset obtained from Biogeochemical-Argo (or BGC-Argo) floats, containing 16,796 profiles of the particulate backscattering coefficient at 700nm ( b b p (700)) measured with three different sensors. We focus at the 900-950m depth interval (within the mesopelagic), where we blackfound values to be relatively constant. While we find significant differences between estimates of b b p (700) obtained with different sensors (≈30 % disagreement), the median values in most oceanic regions obtained with blacka single type of sensor are within 50 % of each other and are consistent with measurements of suspended mass conducted in the early 1970's. Deviations from the quasi-constant background value likely indicate times and locations associated with higher particulate export to depth. Indeed, we observe that in productive high latitude regions, a deep seasonal signal is observed, with enhanced values recorded blacka few months after surface spring/summer maximal concentrations. In addition, the deep b b p (700) is highest in regions exhibiting suboxic-anoxic conditions (e.g. Northern Indian Ocean), which have been associated with local particulate production as well as reduced particle flux attenuation.

Description: The Southern Ocean Carbon and Climate Observations and Modeling (SOCCOM) program has begun deploying a large array of biogeochemical sensors on profiling floats in the Southern Ocean. As of February 2016, 86 floats have been deployed. Here the focus is on 56 floats with quality controlled and adjusted data that have been in the water at least 6 months. The floats carry oxygen, nitrate, pH, chlorophyll fluorescence, and optical backscatter sensors. The raw data generated by these sensors can suffer from inaccurate initial calibrations and from sensor drift over time. Procedures to correct the data are defined. The initial accuracy of the adjusted concentrations is assessed by comparing the corrected data to laboratory measurements made on samples collected by a hydrographic cast with a rosette sampler at the float deployment station. The long-term accuracy of the corrected data is compared to the GLODAPv2 data set whenever a float made a profile within 20 km of a GLODAPv2 station. Based on these assessments, the fleet average oxygen data are accurate to 1±1%, nitrate to within 0.5±0.5 µmol kg −1 , and pH to 0.005±0.01, where the error limit is 1 standard deviation of the fleet data. The bio-optical measurements of chlorophyll fluorescence and optical backscatter are used to estimate chlorophyll a and particulate organic carbon concentration. The particulate organic carbon concentrations inferred from optical backscatter appear accurate to with 35 mg C m −3 or 20%, whichever is larger. Factors affecting the accuracy of the estimated chlorophyll a concentrations are evaluated.

Description: The Southern Ocean (SO) ecosystem plays a key role in the carbon cycle by sinking a major part (43%) of the ocean uptake of anthropogenic CO2, and being an important source of nutrients for primary producers. However, undersampling of SO biogeochemical properties limits our understanding of the mechanisms taking place in this remote area. The Southern Ocean Carbon and Climate Observions and Modeling project (SOCCOM) has been deploying a large number of autonomous biogeochemical floats to study the SO (as of December 2016, 74 floats out of 200 have been deployed). SOCCOM floats measurements can be used to extend remote sensing chlorophyll a (chla) and particulate organic carbon (POC) products under the clouds or during the polar night as well as adding the depth dimension to the satellite-based view of the SO. Chlorophyll a concentrations measured by fluorometers embedded on the floats and POC concentrations derived from backscattering coefficients were calibrated with samples collected during the floats' deployment cruise. Float chla and POC were compared with products derived from observations of MODIS and VIIRS sensors. We find the Ocean Color Index (OCI) global algorithm to agree well with the matchups (within 9%, on average, for the Visible Infrared Imaging Radioneter Suite (VIIRS) and 12%, on average, for the Moderate Resolution Imaging Spectroradiometer Aqua (MODIS)). SO specific algorithms estimating chla are offset by ∼45% south of the Sea Ice Extent Front (∼ 60°S). In addition, POC estimates based on floats agree well with NASA's POC algorithm.

Description: Abstract The spring bloom in the Southern Ocean is the rapid‐growth phase of the seasonal cycle in phytoplankton. Many previous studies have characterized the spring bloom using chlorophyll estimates from satellite ocean color observations. Assumptions regarding the chlorophyll‐to‐carbon ratio within phytoplankton and vertical structure of biogeochemical variables lead to uncertainty in satellite‐based estimates of phytoplankton carbon biomass. Here, we revisit the characterizations of the bloom using optical backscatter from biogeochemical floats deployed by the Southern Ocean Carbon and Climate Observations and Modelling (SOCCOM) and Southern Ocean and Climate Field Studies with Innovative Tools (SOCLIM) projects. In particular, by providing a three‐dimensional view of the seasonal cycle, we are able to identify basin‐wide bloom characteristics corresponding to physical features; biomass is low in Ekman downwelling regions north of the Antarctic Circumpolar Current (ACC) region, and high within and south of the ACC.

Description: Introduction: BCMA is a tumor necrosis factor (TNF) receptor superfamily transmembrane glycoprotein essential for the maturation and survival of plasma cells. CC-93269 is an asymmetric 2-arm humanized IgG TCE that binds bivalently to BCMA and monovalently to CD3ε in a 2+1 format (Seckinger A, et al. Cancer Cell. 2017;31:396-410). The CC-93269-mediated interaction between T cells and BCMA-expressing myeloma cells induces T cell receptor/CD3 crosslinking leading to T cell activation, and release of proinflammatory cytokines and cytolytic enzymes, resulting in myeloma cell death. In preclinical studies with CC-93269 and related molecules, 2+1 BCMA TCEs induced tumor regression in animal models and promoted myeloma cell death in primary pt myeloma cells. Here we report interim results from a phase 1 dose-finding study (CC-93269-MM-001; NCT03486067) evaluating CC-93269 in pts with RRMM. Methods: Eligible pts had RRMM and had received ≥ 3 prior regimens without prior BCMA-directed therapy. In dose escalation, CC-93269 was administered intravenously over 2 hours on Days 1, 8, 15, and 22 for Cycles 1-3; Days 1 and 15 for Cycles 4-6; and on Day 1 for Cycle 7 and beyond, all in 28-day cycles. Dose escalation involved 2 stages: in stage 1, CC-93269 was given in fixed doses; in stage 2, pts received a fixed first dose on Cycle 1 Day 1, followed by intrapatient dose escalation on Cycle 1 Day 8. Primary objectives were to assess the safety and tolerability of CC-93269 and define the maximum tolerated dose (MTD), non-tolerated dose (NTD), and/or recommended phase 2 dose (RP2D). Minimal residual disease (MRD) was assessed after clinical response in pt bone marrow aspirate samples by Next Generation Flow using the EuroFlow panel. MRD negativity was reported only if a minimum sensitivity of 〈 1 tumor cell in 105 nucleated cells was achieved. Results: As of May 24, 2019, 19 pts had received CC-93269. Median age was 64 years (range 51-78), with a median of 6.2 years (range 1.4-13.9) since initial diagnosis. The median number of prior regimens was 6 (range 3-12) and included treatment with autologous stem cell transplantation (73.7%), allogenic stem cell transplantation (10.5%), lenalidomide (100%), pomalidomide (84.2%), bortezomib (100%), carfilzomib (84.2%), and daratumumab (DARA; 94.7%). All pts had MM refractory to their last line of therapy, with 16 (88.9%) refractory to DARA, 17 (89.5%) to their last proteasome inhibitor, and 16 (84.2%) to their last immunomodulatory agent. CC-93269 doses ranged from 0.15 to 10 mg; median duration of treatment was 14.6 weeks (range 1.6-32.0) with pts receiving a median of 4 cycles (range 1-8). Grade 3-4 treatment-emergent adverse events were reported in 15 (78.9%) pts and included 10 (52.6%) pts with neutropenia, 8 (42.1%) with anemia, 5 (26.3%) with infections, and 4 (21.1%) with thrombocytopenia. No pt required dose modifications. Cytokine release syndrome (CRS) was reported in 17 (89.5%) pts, the majority of whom reported a maximum grade 1 (n = 11 [57.9%]) or grade 2 (n = 5 [26.3%]), and occurred most frequently with the first or second dose (n = 22 of 27 events [81.5%]). CRS prophylaxis was implemented with dexamethasone for first dose and dose increases in pts receiving ≥ 6 mg. Of 27 CRS events, 8 (29.6%) were managed with dexamethasone and 10 (37.0%) with tocilizumab. One pt receiving 6 mg CC-93269 as first dose and 10 mg on Cycle 1 Day 8 died on study in the setting of CRS, with a potential infection as a contributing factor. Dose-related pharmacodynamic activity, including peripheral blood immune cell redistribution and transient release of pro- and anti-inflammatory cytokines, was observed in pts. Of the 12 pts treated with ≥ 6 mg CC-93269 in Cycle 1, 10 pts achieved a partial response (PR) or better (overall response rate; 83.3%), including 7 (58.3%) with a very good partial response (VGPR) or better and 4 (33.3%) with a stringent complete response (sCR) (Table); 9 (75.0%) pts achieved MRD negativity. The median time to response was 4.2 weeks (range 4.0-13.1), and 10 of 10 responses were ongoing with follow-up ranging from 2.1 to 4.7 months. The NTD, MTD, and RP2D have not yet been reached. Conclusions: CC-93269, a 2+1 BCMA TCE, shows a manageable safety profile and promising efficacy, including MRD-negative sCRs, in pts with heavily pretreated RRMM. The study continues to enroll in the dose escalation phase. Updated safety and efficacy data will be presented at the meeting. Disclosures Costa: Fujimoto Pharmaceutical Corporation Japan: Other: Advisor; Karyopharm: Consultancy; Abbvie: Consultancy; Sanofi: Consultancy, Honoraria, Speakers Bureau; GSK: Consultancy, Honoraria, Research Funding; Celgene: Consultancy, Honoraria, Research Funding; Amgen: Consultancy, Honoraria, Research Funding, Speakers Bureau; Janssen: Research Funding, Speakers Bureau. Wong:Genentech: Research Funding; Janssen: Research Funding; Celgene Corporation: Research Funding; Fortis: Research Funding; Juno: Research Funding. Bermúdez:MSD: Consultancy, Speakers Bureau; Amgen: Consultancy, Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees; Fresenius: Consultancy, Membership on an entity's Board of Directors or advisory committees; Celgene Corporation: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. de la Rubia:AMGEN: Consultancy; Celgene Corporation: Consultancy; AbbVie: Consultancy; Takeda: Consultancy; Janssen: Consultancy. Mateos:Pharmamar: Membership on an entity's Board of Directors or advisory committees; Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees; Adaptive: Honoraria; EDO: Membership on an entity's Board of Directors or advisory committees; GSK: Membership on an entity's Board of Directors or advisory committees; Abbvie: Membership on an entity's Board of Directors or advisory committees; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees; Amgen: Honoraria, Membership on an entity's Board of Directors or advisory committees. Ocio:BMS: Honoraria; Sanofi: Research Funding; Mundipharma: Research Funding; Takeda: Consultancy, Honoraria; Seattle Genetics: Consultancy; Celgene: Consultancy, Honoraria, Research Funding; Array Pharmaceuticals: Research Funding; Pharmamar: Consultancy; Novartis: Consultancy, Honoraria; AbbVie: Consultancy; Amgen: Consultancy, Honoraria, Research Funding; Janssen: Consultancy, Honoraria. Rodríguez-Otero:Celgene Corporation: Consultancy, Honoraria, Speakers Bureau; Janssen: Consultancy, Honoraria; Takeda: Consultancy; BMS: Honoraria; Kite Pharma: Consultancy. San-Miguel:Amgen, Bristol-Myers Squibb, Celgene, Janssen, MSD, Novartis, Roche, Sanofi, and Takeda: Consultancy, Honoraria. Li:Celgene Corporation: Employment, Equity Ownership. Sarmiento:Celgene Corporation: Employment. Lardelli:Celgene Corporation: Employment, Equity Ownership. Gaudy:Celgene Corporation: Employment, Equity Ownership. Boss:Celgene Corporation: Employment, Equity Ownership. Kelly:Celgene Corporation: Employment. Burgess:University of California: Other: Volunteer clinical faculty, without salary, Patents & Royalties: Patent - T315A and F317I mutations of BCR-ABL kinase domain; Celgene Corporation: Employment, Equity Ownership, Patents & Royalties: Patent - CD47 antibodies and methods of use thereof. Hege:Celgene Corporation: Employment, Equity Ownership, Patents & Royalties; Arcus Biosciences: Membership on an entity's Board of Directors or advisory committees; Society for Immunotherapy of Cancer: Membership on an entity's Board of Directors or advisory committees; Mersana Therapuetics: Membership on an entity's Board of Directors or advisory committees. Bensinger:Amgen, Celgene: Other: Personal Fees, Research Funding, Speakers Bureau; Takeda, Janssen: Speakers Bureau; Sanofi, Seattle Genetics, Merck, Karyopharm: Other: Grant.

Description: Background: Loss of immune surveillance, mediated through immune checkpoint (ICP) interactions, is thought to be a key step in the development of cancers including AML and HR-MDS. AZA is a standard therapy for pts with AML who are unfit for IC and for pts with HR-MDS. AZA can promote immune recognition of tumor cells and potentially increase expression of ICP molecules, which can mediate resistance to AZA. As myeloid cell lines and samples from pts treated with hypomethylating agents demonstrated up-regulation of PD-L1 expression, blockade of the PD-L1 ICP with durva in combination with AZA may enhance antitumor activity and improve clinical outcomes. Here, we report the final results from a large phase 2 study evaluating the efficacy and safety of AZA+durva vs. AZA alone in pts with HR-MDS or AML (NCT02775903). Methods: This randomized, open-label, international, multicenter study enrolled untreated pts in 2 cohorts: 1) MDS (aged ≥18 years; IPSS-R intermediate, high, and very high) and 2) older AML pts (aged ≥65 years) who were ineligible for IC. All pts had ECOG performance status 0-2 and were separately randomized (1:1) to receive SC AZA 75 mg/m2 Days 1-7 and durva 1500 mg IV on Day 1 Q4W (Arm A) or AZA alone (Arm B) and stratified according to cytogenetic risk (MDS, very good/good/intermediate vs. poor/very poor; AML, intermediate vs. poor). Treatment was planned to continue until progression or unacceptable toxicity. Disease status was evaluated every third treatment cycle. Primary MDS endpoints included overall response rate (ORR, defined as complete remission [CR], marrow [m]CR, partial response [PR], or hematologic improvement [HI]) based on IWG 2006 response criteria, while for AML ORR was defined as CR or CR with incomplete blood recovery (CRi) based on modified IWG 2003 response criteria. Secondary endpoints included PFS, OS, and safety. Peripheral blood samples were collected to assess changes in DNA methylation using the EPIC methylation array (Illumina). Bone marrow (BM) aspirates were obtained for quantitation of PD-L1 surface expression by flow cytometry and values are reported as molecules of equivalent soluble fluorochrome. Results: A total of 213 pts, 84 with MDS (each arm, n=42) and 129 with AML (Arm A, n=64; Arm B, n=65) were randomized. As of October 31, 2018, 32 pts (MDS, n=14; AML, n=18) continued to receive trial treatment while 181 (MDS, n=70; AML, n=111) had discontinued. Baseline demographics and disease characteristics were generally balanced across treatment groups in both cohorts. Median number of treatment cycles for AML Arm A vs. B, 6.5 vs. 6.7; for MDS Arm A vs. B, 7.9 vs. 7.0. No statistically significant differences in ORR between treatment arms were observed in either cohort (Tables 1 and 2). In MDS Arm A vs. B, median OS was 11.6 vs. 16.7 months (mo) and PFS was 8.7 vs. 8.6 mo. In the AML cohort, median OS was 13.0 vs. 14.4 mo and PFS was 8.1 vs. 7.2 mo. Caution should be used when interpreting results because 〉50% of patients were censored. The most frequent TEAEs (≥15%) were hematologic and GI toxicity. In the MDS and AML cohorts, 7 and 17, respectively, immune-mediated AEs were observed; all were treated and resolved. AZA induced similar trends in global hypomethylation, along with focal hypomethylation of PD-L1 and PD-L2 gene loci, at the end of treatment cycle 1 in all treatment groups and cohorts. Mean PD-L1 surface expression in BM immune cells at baseline was highest in monocytes (MDS=1,425; AML=1,536), followed by granulocytes (MDS=550; AML=758) and myeloid blasts (MDS=532; AML=735). Increased surface expression of PD-L1, but not PD-L2, was observed at the end of treatment cycle 3 on BM granulocytes and monocytes from MDS pts and on BM monocytes from AML pts, but no increase was detected on myeloid blasts. Conclusions: To our knowledge, this is the first large randomized trial of AZA with or without ICP blockade in older unfit AML and HR-MDS pts reported to date. No clinically meaningful difference in efficacy was observed between treatments for either cohort. No new safety signals or potential overlapping risks were identified with the combination. While the hypomethylating activity of AZA on PD-L1 gene was confirmed, no treatment-mediated induction of PD-L1 surface expression was observed on myeloid blasts. Disclosures Zeidan: Acceleron Pharma: Consultancy, Honoraria, Research Funding; Celgene Corporation: Consultancy, Honoraria, Research Funding; Abbvie: Consultancy, Honoraria, Research Funding; Otsuka: Consultancy, Honoraria, Research Funding; Pfizer: Consultancy, Honoraria, Research Funding; Medimmune/AstraZeneca: Research Funding; Boehringer-Ingelheim: Consultancy, Honoraria, Research Funding; Trovagene: Consultancy, Honoraria, Research Funding; Incyte: Consultancy, Honoraria, Research Funding; Takeda: Consultancy, Honoraria, Research Funding; ADC Therapeutics: Research Funding; Jazz: Honoraria; Ariad: Honoraria; Agios: Honoraria; Novartis: Honoraria; Astellas: Honoraria; Daiichi Sankyo: Honoraria; Cardinal Health: Honoraria; Seattle Genetics: Honoraria; BeyondSpring: Honoraria. Voso:Novartis: Speakers Bureau; Celgene: Research Funding, Speakers Bureau. Taussig:Celgene: Research Funding. Boss:Celgene Corporation: Employment, Equity Ownership. Copeland:Celgene Corporation: Employment, Equity Ownership. Gray:Celgene Corporation: Employment, Equity Ownership. Previtali:Celgene Corporation: Employment, Equity Ownership. O'Connor:Celgene Corporation: Employment, Equity Ownership. Rose:Celgene Corporation: Employment, Equity Ownership. Beach:Celgene Corporation: Employment, Equity Ownership. OffLabel Disclosure: Durvalumab is a PD-L1 blocking antibody indicated for the treatment of patients with 1) locally advanced or metastatic urothelial carcinoma who have disease progression during or following platinum-containing chemotherapy, or who have disease progression within 12 months of neoadjuvant or adjuvant treatment with platinum-containing chemotherapy, or 2) unresectable, stage 3 NSCLC whose disease has not progressed following concurrent platinum-based chemotherapy and radiation therapy.

Description: Recent retrospective studies demonstrated similar overall survival (OS) and relapse rate after allogeneic HCT using matched unrelated or haplo-identical donors. However, differences in graft versus host disease (GVHD) prevention protocols using ATG or PTCY may have influenced the results. In addition, there is little knowledge about immune reconstitution after PTCY compared to ATG. We examined the outcomes of 73 consecutive patients who received allogeneic HCT from 5/2015 to 4/2019 (39 Haplo, 34 MUD). Patient's Characteristics shown in table-1. The two groups matched except for donor age, CD34 dose infused and race. Conditioning regimens shown in table-1. MUD recipients received GVHD prophylaxis with Tacrolimus/ Mycophenolate (Tacro/MMF) in addition to ATG (24 Patients) or PTCY (10 Patients) while Haploidentical patient received Tacro/MMF with PTCY. A panel of immune reconstitution markers collected at day 100 post- transplant for CD3, CD4, CD8, Activated T cell ( HLA- DR3+ CD3+)and NK cells ( CD56+) was obtained for 29 MUD and 28 Haploidentical recipients. We observed pronounced proliferation and recovery in all T cell subsets in Haploidentical patients compared to MUD patients at day 100 as shown in Fig-1. This robust T cell recovery in Haploidentical transplant patients with PTCY was statistically significant for CD3, CD4 and CD8. When Immune reconstitution for Haploidentical patients compared to MUD patients who received PTCY, it maintained its robust effect on T cell proliferation (Fig-2) although it did not reach statistical significance. The overall survival at one-year with median duration of follow up of 22.6 months was 61.5% and 82.3% for Haploidentical and MUD recipients respectively; P=0.14. There were 15 deaths during the first year in the Haploidentical patients (3 = relapse, 5 = severe cytokine release syndrome (CRS), 1=Veno-occlusive disease, 3= infection, 2=GVHD and 1 = primary graft failure). In contrast there were only six deaths in MUD patients (2= relapse, 3= GVHD and 1= infection). There was no deaths in MUD PTCY patients in the first year. There was no primary graft failure in either arm, however secondary graft failure occurred in 2 Haploidentical and 1 MUD patients. Median time to engraftment was 18 days for Haploidentical (range, 12-57) and 11.6 days for MUD (range, 10-18). Acute GVHD grade 2-4 developed in 35% in MUD and 23% in Haploidentical patients. Conclusions: We found robust early immune recovery after Haploidentical HCT compared to MUD HCT. The degree of HLA mismatch with Haploidentical HCT and antigen presentation may have contributed to pronounced T cell proliferation as the same effects was not observed in MUD HCT with PTCY. Despite the early recovery of T cells after Haploidentical HCT the overall survival did not exceed the overall survival with MUD HCT. Severe CRS contributed to the increased mortality seen in Haploidentical HCT patients. Further strategies are needed to decrease treatment related mortality with Haploidentical HCT. Disclosures No relevant conflicts of interest to declare.

Description: Multiple studies have examined the impact of the intensity of conditioning regimens on myeloablation and the risk of relapse after HCT. In contrast to adoptive cell transfer and Chimeric-Antigen Receptor (CAR) T-Cell therapy, there is limited, if any knowledge that has addressed the impact of intensity of lymphodepletion on relapse after HID HCT. We hypothesize that enhanced lympho-depletion would create an enhanced host immunogenic microenvironment that would foster potent donor T cell expansion and alloreactivity after T-cell replete peripheral blood HID HCT.1,2 We utilized an intensified lympho-depleting conditioning regimen with Fludarabine (Flu) 150 mg/m2, Melphalan (Mel) 140 mg/m2 and Cyclophosphamide (CY) 29 mg/m2 prior to T-cell replete peripheral blood HID HCT to treat 15 consecutive patients with high risk hematological malignancies between July 2015 and June 2017. The intensity of lymphodepletion was confirmed in 12 evaluable patients at day (0) by complete absence of lymphocytes in peripheral smear. In contrast, myeloid elements were detected in 7/12 patients suggesting more intense lympho-depletion than myeloablation. All Patients received graft versus host disease prophylaxis with Tacrolimus/Mycophenolate starting at day +5 and Cyclophosphamide 50 mg/Kg on day +3 & +4. Mycophenolate continued for 30 days and Tacrolimus stopped at Day 180 without taper. Patient characteristics are shown in Table 1. More than half the patients (n=8 Pts) had relapsed/refractory or progressive disease at time of transplant. The median duration of follow up for survivors is 29 months (range 13-37). Chimerism studies were performed at day +30 and +100 post-transplant by variable number tandem repeat PCR analysis of peripheral blood (PB) and bone marrow (BM). All patients engrafted and achieved 100% Chimerism in BM and PB ( CD3, CD33 & CD56) by day 100 except for 1 patient who died at day +25 prior to engraftment. Median time to neutrophil engraftment was 21 days (range 12-57). All patients with refractory/relapsed disease achieved complete remission post-transplant except for 1 patient who died from transplant complications prior to engraftment. The day 100, 1 year & 2 year overall survival was 93%, 73% & 66% respectively. We observed very low cumulative incidence of relapse of 7% at day 100, 1 and 2 years post-HCT (only 1/15 patients). Treatment related mortality (TRM) was 6%, 20% and 27% at day 100, 1 and 2 years respectively (4/15 patients). Severe Cytokine Release Syndrome (CRS), grade 4 by Lee Criteria occurred in 4 patients, all of them have died at day 25, 258, 288 and 540 post HCT. Three of the four patients with severe CRS had refractory relapsed disease at time of HCT. Grade II-IV acute GVHD developed in 4/15 patients (27%), 2 of whom had grade III-IV by day +180. Chronic extensive GVHD developed in 7 patients (46%), which required definitive therapy (Prednisone/Rituximab/Extracorporeal Photopheresis). At 2 years post HCT, only 1/7 patients remain with extensive chronic GVHD requiring active treatment, 3 patients have quiescent disease and 3 patients have died. Post -transplant immune reconstitution panels were obtained at day 60, 120, 180 and 1 year in 14, 13, 13 and 10 evaluable patients respectively as shown in Fig 1. We observed early recovery in all T-cell subsets at day 60 with activated T cells (CD3+, HLA-Dr+) being most pronounced. While the early proliferation in activated T cells declined through the first-year post transplant, NK cells and CD4 maintained their early recovery through the first year. There was initial decline in the number of B cells at day 120 which gradually recovered by 1 year. Conclusion: Enhanced lymphodepletion prior to peripheral blood HID HCT may enhance early T cell proliferation alloreactivity and immune reconstitution. There was low relapse rate at the expense of high TRM in patients who developed grade IV CRS. Future strategies directed at decreasing disease burden prior to lympho-depletion and improved management of severe CRS in high risk patients are needed to harness the benefits of the observed low relapse rate. 1. Beavis et al, Reprogramming the tumor microenvironment to enhance adoptive cellular therapy. Semin Immunol. 2016 Feb;28(1):64-72. 2. Lu X, Ding ZC, Cao Y, Liu C, Habtetsion T, Yu M, Lemos H, Mellor AL, et al. Alkylating agent melphalan augments the efficacy of adoptive immunotherapy using tumor-specific CD4+ T cells.J Immunol. 2015 Feb 15;194(4):2011-21. Disclosures No relevant conflicts of interest to declare.

Description: The outcomes after Haploidentical HCT with Fludarabine (Flu)/Cyclophosphamide (Cy)/TBI and PTCY as pioneered by the Hopkins group have been associated with higher risk of relapse and delayed immune reconstitution. Multiple groups have explored the potential benefits of more intensive conditioning regimens with or without TBI. However, none of these regimens to our knowledge has exploited the immunogenic properties of pre-transplant low dose Cy while avoiding the immune-suppressive effect of TBI. Additionally, there is limited knowledge regarding immune reconstitution post haploidentical HCT with the use of mobilized peripheral blood stem cells. Accordingly, we designed a protocol modification of the Hopkins regimen by replacing TBI with Melphalan (Mel) without adding Thiotepa in contrast to the MD Anderson regimen (Ciurea et al). We hypothesized that the immunogenic properties of pre-transplant low dose Cy along with the immunomodulatory effects of Mel would enhance early post-transplant engraftment and early peripheral T cell recovery through enhanced cytokine release and antigen alloreactivity We examined the clinical outcomes and immune reconstitution recovery of 12 consecutive haploidentical HCT patients with high-risk hematological malignancies. Patient and graft characteristics are as shown in table-1. The conditioning regimen was low dose Cy 14.5 mg/m2 on day -6 & day -5, Flu 30 mg/m2 on days -6 to Days -2 and Mel 70 mg/m2 on day -3 & -2. Graft versus host disease prophylaxis (GVHD) was PTCY 50 mg/Kg on day +3 and day +4 along with Tacrolimus and Mycophenolate starting at day +5 as previously described by the Hopkins group. An immune reconstitution panel of absolute lymphocyte count (ALC), CD3, CD4, CD8, Activated T cell (CD3-HLA Dr + T cells) & NK cell (CD56/16) was performed by 4 color flow-cytometry on days +60, +120 and +180 post HCT. Chimerism studies were performed at day +30 and +100 post HCT by variable number tandem repeat PCR analysis of peripheral blood & bone marrow. All of the patients were treated according to an institutional protocol and records were reviewed retrospectively after IRB approval. All patients engrafted with a median time to engraftment of 17 days (range 12-23). Chimerism studies revealed enhanced engraftment with 100% donor in bone marrow (unsorted) and peripheral blood (CD3, CD33 & CD 56) at day +30 in all 12 patients. All patients with active disease at time of transplant (5 Pts) achieved complete remission at day +30 evaluation. Post HCT immune recovery is shown in table 2. There was significant early recovery at day + 60 of the median ALC and all T cell subsets. This recovery was most pronounced in activated T cells. While we have observed a progressive reduction in the median number of early activated T cells at day 120 & 180, the number of helper T cells (CD4) and NK cells (CD56/16) did not decline (Figure 1). With a median duration of follow up of 261 days (range 62-390), the overall survival at day 100 and projected one year survival is 96% and 81% respectively. Only one of 12 patients had relapsed. Acute GVHD grade 2-4 developed in six of 12 patients, two of whom were grade 3-4. Chronic GVHD developed in four patients (1 serositis, 1 pericardial effusion and 2 nephrotic range proteinuria). Cytokine storm developed in 5/12 patients after stem cell infusion and resolved after PTCY. BK cystitis developed in four patients but continuous bladder irrigation was only required in two patients. All cases of BK cystitis were transient and resolved with supportive measures. CMV reactivation occurred in 9/12 patients; no CMV disease or CMV mortality was observed. Aspergillus antigen positivity in serum occurred in 4 /12 but only two developed clinical fungal infection. Conclusion: In this limited series of patients with high- risk hematological malignancies who underwent haploidentical HCT with low dose Cy/Flu/Mel and PTCY, the regimen was well tolerated and resulted in effective disease control. The regimen has also demonstrated enhanced early engraftment and robust immune recovery in comparison to other studies, table 3. However, it is not clear if this enhanced immune recovery is related to the conditioning regimen modification or the use of mobilized stem cells. The results are intriguing and need further confirmation. Disclosures No relevant conflicts of interest to declare.

Description: B-cell maturation antigen (BCMA), a member of the TNF receptor superfamily, serves as the cell surface receptor for B-cell activating factor (BAFF). Upon binding of BAFF to BCMA, an intracellular signaling cascade is initiated resulting in upregulation of JNK pathway signaling events and NFkB mediated transcription. The canonical expression pattern of BCMA begins on germinal center B-cells and becomes maximally expressed on mature cells such as plasma cells. Given the high degree of expression of BCMA on multiple myeloma (MM) cells, the malignant counterpart to plasma cells, it has become a target of interest for CAR T and antibody mediated modalities such as antibody drug conjugates and bispecific molecules. Recent clinical data from clinical trials employing BCMA targeted CAR T cells or T cell engager (TCE) antibodies have demonstrated significant responses in heavily pretreated myeloma patients with overall response rates ranging from 70% to 80%. As BCMA is known to be expressed in earlier B-cell lineages, we sought to explore the expression of BCMA in non-Hodgkin lymphoma (NHL) and its sensitivity to CC-93269, a 2+1 TCE currently being clinically investigated in MM. NHL is a heterogeneous collection of lymphomas that can be classified into two major subgroups; aggressive lymphomas of which diffuse large B-cell (DLBCL) is the most prevalent subtype and indolent lymphomas of which follicular lymphoma is the largest constituent. We first sought to directly quantitate cell surface expression of BCMA utilizing a flow cytometry system based on a logarithmic dilution of phycoerythrin beads of a known quantity. In a panel of 43 NHL cell lines, we determined that BCMA expression ranged from 43 to 17,048 molecules per cell (median, 420). An isogenic pair of K562 that is null for BCMA expression and K562 constitutively overexpressing BCMA (K562-BCMA) (15,866 molecules/cell) served as negative and positive controls, respectively. Additionally, the MM cell line H929 was profiled to serve as an additional control with a BCMA expression level of 7,065 molecules/cell. Next, utilizing quantitative PCR we found that relative BCMA mRNA expression in the lymphoma cell lines ranged from 0.001 to 0.17-fold when normalized to the H929 MM cell line. Furthermore, we were able to determine that in the lymphoma cells there is a poor correlation between protein expression (mean fluorescent intensity) and mRNA expression (r2, 0.33). We next examined if there was any correlation between BCMA surface expression and T-cell mediated cytotoxicity after administration of CC-93269 in a co-culture assay. We selected 11 DLBCL cell lines with a surface expression ranging from 45 molecules to 17,000 molecules per cells and incubated them in a co-culture system with a defined 1:5 target:effector ratio with CC-93269 (0-200 ng/ml) for five days. Significant apoptosis as measured by annexin V and ToPro-3 staining of CFSE positive target cells was observed in 10 of the 11 cell lines profiled with an IC50 of 0.1 to 38 ng/ml for CC-93269. As controls, the K562 isogenic pair were also profiled with the K562-BCMA cell line exhibiting an IC50 of 0.5 ng/ml and no activity observed against the parental K562 cell line. Additionally, a bispecific antibody where the two binding domains for BCMA was altered to target HEL (hen egg lysozyme) demonstrated no activity against any of the cell lines profiled at a defined dose of 200 ng/ml. No association between CC-93269 activity and BCMA expression or cell of origin was found. To determine the expression of BCMA in primary DLBCL biopsy samples, we developed a novel monoclonal BCMA immunohistochemistry antibody (clone: G12). The antibody and IHC staining protocol were validated to have good on-target specificity in both cell lines and tissues, including MM and DLBCL biopsies, with a range of stain intensity (1-3+) observed in both the golgi and on the plasma membrane. A proof of concept study on a cohort of 110 commercial DLBCL samples is currently underway. Cumulatively, our data demonstrate that BCMA is expressed on the cell surface of a broad panel of NHL cell lines and in primary DLBCL lymph node biopsies. Additionally, the expression levels of BCMA in these preclinical cell line models was sufficient to elicit significant CC-93269 mediated cytotoxicity. These data highlight the potential for the treatment of DLBCL patients with a 2+1 T-cell engager targeting BCMA. Disclosures Hagner: Celgene Corporation: Employment, Equity Ownership, Patents & Royalties. Waldman:Celgene: Employment, Equity Ownership, Patents & Royalties. Gray:Celgene: Employment, Equity Ownership. Yura:Celgene: Employment, Equity Ownership. Hersey:Celgene: Employment, Equity Ownership. Chan:Celgene: Employment, Equity Ownership. Zhang:Celgene: Employment, Equity Ownership. Boss:Celgene Corporation: Employment, Equity Ownership. Gandhi:Celgene Corporation: Employment, Equity Ownership, Patents & Royalties.