Background: Mature B-NHL, including Burkitt lymphoma (BL) and primary mediastinal large B cell lymphoma (PMBL) express CD20+/CD79b+ and have an excellent prognosis, however, subset of patients relapse secondary to chemoimmunotherapy resistant disease and have a dismal prognosis (≤ 20% 5 yr. EFS, Cairo et al. Blood. 2007; Gerrard/Cairo et al., Blood, 2013, Goldman/Cairo et al. Leukemia, 2013). PV has been demonstrated to possess significant preclinical activity against indolent CD79b+NHL (Polson et. al.Can. Res.2009). We previously observed that obinutuzumab (Anti-CD20 mAb) significantly enhanced cell death and increased overall survival against BL (Awasthi/Cairo et al., BJH 2015) in xenografted NSG mice. However, additive/synergistic effects of PV with obinutuzumab against mature PMBL/BL are unknown. Objective: To determine the efficacy of the PV or obinutuzumab/RTX alone or in combination against PMBL and rituximab (RTX) sensitive/resistant BL cell lines. Methods: Raji4RH (provided by M. Barth, MD, Roswell Park Cancer Institute) and Raji/ Karpas1106P (ATCC, USA) were cultured in RPMI. Tumor cells were incubated with PV, and/or anti-CD79b, MMAE (generously supplied by Genentech Inc.) with obinutuzumab /rituximab (100ug/ml) for 4 hr with NK cells at 10:1 E: T ratio and cytotoxicity was determined by DELFIA cytotoxicity assay. Six to 8 week old female NSG (NOD.Cg-Prkdcscid Il2rgtm1Wjl/SzJ), were divided into 5 groups: PBS, isotype control, PV, antiCD79B mAb and MMAE (5mg/kg). Mice were xenografted with intravenous injections of Luc+ BL and PMBL cells and tumor burden was monitored by IVIS spectrum system. Results: OS of mice receiving PV alone was significantly increased compared to antiCD79b or isotype control in Raji (35.5 vs.17 vs.19.5 days, p=0.0001, 0.0003), Raji4RH (50 vs.18 vs.18.5 days, p=0.0001, 0.0001) and Karpas1106P (150 vs 89 vs 64 days, p=0.03, 0.003), respectively. Obinutuzumab+NK, rituximab+NK compared to PV+NK cells significantly enhanced cell lysis in Raji, 65.9±2.4% vs. 38.9±5.4% vs. 44.24±8.1% (p=0.001 & p=0.001), Raji4RH, 52.8±9.4% vs. 16.04±7.2% vs.47.0±8.2% (p=0.03 & p=NS) and Karpas1106P, 66.10±5.3% vs.48.2±3.9% vs. 61.6±10.06% (p=0.004 & NS), respectively. PV+ obinutuzumab+NK, significantly improved cytotoxicity compared to PV+ rituximab+NK in Raji, 93.6±6.1% vs 79.9±5.3% (p=0.007), Raji4RH, 78.07±2.05% vs 63.5±0.16% (p=0.004) and Karpas1106P, 88.3±6.3 %vs.73.03±3.03% (p=0.003), respectively. Conclusion: Our preliminary data indicates that PV significantly increased survival in BL and PMBL NSG xenografts compared to anti-CD79b Ab alone. Furthermore, PV in combination with obinutuzumab significantly enhances cytotoxicity in BL and PMBL compared to obinutuzumab or PV alone. Citation Format: Aradhana Awasthi Tiwari, Dina Edani, Christeen Azmy, Janet Ayello, Christian Klein, Mitchell S. Cairo. Enhanced in vitro/in vivo cytotoxicity against Burkitt lymphoma/primary mediastinal large B cell lymphoma by polatuzumab vedotin (hu- anti-CD79b-vc-MMAE, PV) alone or in combination with obinutuzumab [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1788.

Background: Natural killer (NK) cell allo-reactivity in haploidentical allogeneic hematopoietic cell transplantation (HCT) is associated with lower relapse without greater graft-versus-host disease (GVHD). Dimorphisms of the MHC class I chain-related gene A (MICA) alleles can influence NK cell triggering and T cell modulation. Studies evaluating donorrecipient MICA incompatibilities on outcomes after matched unrelated donor HCT show conflicting results, but its significance is unknown in haploidentical HCT. We hypothesized donor-recipient MICA incompatibilities may influence outcomes in haploidentical HCT. Methods: We conducted a single center, retrospective analysis of all haploidentical HCT for hematologic malignancies in which MICA data was available. Outcomes were compared between those with and without donor-recipient MICA matches with Cox analysis or Fine and Gray regression. A secondary analysis examined dimorphisms at the MICA-129 position, which has been categorized as weak (valine/valine: V/V), mixed (methionine/valine: V/M), or strong (methionine/methionine: M/M) receptor binding affinity. Results: From 2014 -2016, 38 patients underwent a haploidentical HCT, with 14 in the MICA matched cohort and 24 in the MICA mismatched cohort with no significant differences in baseline characteristics. Diagnoses included acute myeloid (N = 17) and lymphoblastic leukemia (N = 7), myelodysplastic syndromes (N = 4), and others (N = 10). Median age at HCT was 51 years (range, 7-72), with 79% Caucasian. Myeloablative HCT was performed in 53% of patients and 55% had a bone marrow graft source. Most patients received tacrolimus and mycophenolate with post-transplant cyclophosphamide as GVHD prophylaxis. There were no differences in HLA disparities between the two groups (P = .64). There was a trend towards greater acute GVHD in the MICA mismatched cohort (HR 3.06, P = .07) ( Figure 1). The MICA mismatched group also had a trend towards a lower risk of relapse mortality (HR .28, P = .06) ( Figure 2). There was no significant difference in relapse-free survival (HR .62, P = .32), nonrelapse mortality (HR 1.52, P = .63), or overall survival (HR .56, P = .24). The most common cause of death was relapse. In secondary analysis examining the MICA-129 genotype, patients with a V/V donor had higher risk of chronic GVHD (P = .006), though sample size was limited to 4 patients. No other outcome differences were seen relative to MICA-129 genotype. Conclusion: We conclude that donor-recipient MICA incompatibility may be associated with a higher incidence of acute GVHD after haploidentical HCT consistent with previous

primary hepatic rhabdomyosarcoma is rare, making decisions regarding locoregional management with resection and/or conventional radiation difficult. We present a novel treatment approach for a pediatric patient diagnosed with rhabdomyosarcoma diffusely involving the liver. this patient underwent treatment with yttrium-90 (Y-90) microspheres followed by external beam radiation therapy (eBrt) to residual disease, interdigitated with systemic chemotherapy. Initial post-radiation imaging showed significant response to treatment, and she experienced minimal acute toxicities and no long-term toxicities. she developed recurrent pet-avid disease 23 months after Y-90 treatment, necessitating further local and continued systemic therapies. We report on the tumor control following Y-90 and eBrt treatment.

Background: Mature B-NHL, including Burkitt lymphoma and primary mediastinal large B cell lymphoma express CD79b+ and have an excellent prognosis with chemo-immunotherapy (Cairo et al Blood, 2007, Gerrard/Cairo et al. Blood, 2013). However, a subset of patients with relapsed/refractory mature B-NHL has chemoimmunotherapy resistant disease a dismal prognosis (≤ 10% 5 years, EFS) (Cairo et al. JCO, 2012). The antibody drug conjugates (Polatuzumab Vedotin, PV) has demonstrated significant preclinical activity against indolent CD79b+NHL (Polson et al.Can. Res. 2009). More recently PV has been safe and well tolerated in adult with CD79b refractory CLL (Palanca-Wessels et al. Lancet Oncol, 2014) but its preclinical activity against mature B-NHL (BL/PMBL) is unknown. Objective: To determine the efficacy of the PV against CD79b+ PMBL and rituximab (RTX) sensitive/resistant BL tumor cell lines in-vitro and in-vivo. Design/Methods: Raji/Raji4RH (BL, provided by M. Barth, Roswell Park Cancer Institute) and Karpas1106P and MedB-1(PMBL) were cultured in 10-20% RPMI. Tumor cells were incubated with hu anti-CD79b-vc-MMAE, and/or anti-CD79b, MMAE or huIgG1 (generously supplied by Genentech Inc.) for 24 hrs. Cell death was evaluated by staining with annexin V/7AAD and analyzed by flow cytometry, n=3. Six to 8 week old female NSG (NOD.Cg-Prkdcscid Il2rgtm1Wjl/SzJ), were divided into 5 groups: PBS only (control), isotype control (IgG), PV (5mg/kg), anti-CD79b mAb (5 mg/kg) and MMAE (5 mg/kg). Mice were xenografted with intravenous injections of Luc+ Raji/Raji4RH and Karpas1106P cells as we have previously demonstrated (Awasthi/Cairo et al, BJH, 2015). Mice were treated twice a week for 6 weeks. Tumor burden was monitored by IVIS spectrum system. Results: Anti-CD79b-vc-MMAE compared to anti-CD79b Ab or IgG1 Ab alone (10µg/ml, 24hrs), significantly enhanced cell death in Raji, 47.2±1.3% vs 29.1±6.0% vs. 28.2±4.3%, (p=0.0008 and p=0.00006), Raji4RH, 29.8±9.1% vs 25.4±3.9% vs. 18.0±8.2% (p=NS and p=0.03), Karpas1106P, 46.8±5.3% vs 33.8±3.5% vs. 26.2±0.4% (p=0.02 and 0.006) and MedB-1, 47.4±2.2% vs 27.6±2.4% vs. 23.9±1.7% (p=0.002 and 0.0001), respectively. Further, median survival time in mice receiving 5 mg/kg of PV was significantly increased when compared to mice receiving 5 mg/kg of anti-CD79b Ab or isotype control in Raji, Raji4RH and Karpas1106P (35.5 vs.17 vs. 19.5 days, p=0.0001, 0.0003, 50 vs. 18 vs. 18.5 days and 150 vs 89 vs 64 days, p=0.03 ,0.003, respectively) Conclusions: Our preliminary data indicates that PV significantly enhances cell death in RTX sensitive/ resistant BL and PMBL compared to CD79b Ab or isotype control. Furthermore, PV significantly increased survival in BL and PMBL NSG xenografts Citation Format: Aradhana A. Tiwari, Janet Ayello, Christeen Azmy, Carmella van de Ven, Mitchell S. Cairo. Polatuzumab vedotin significantly enhances in vitro cell death and overall survival against CD79b+ Burkitt lymphoma (BL)/primary mediastinal large B-cell lymphoma (PMBL) NSG xenograft mice [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2656. doi:10.1158/1538-7445.AM2017-2656

Background: EBV latent proteins (LMP-1/2) increase the chemoresistance in Burkitt Lymphoma (BL) cells by constitutively activating the CD40 receptor. It has also been demonstrated that B- cell lymphoma resistant to rituximab is a result of LMP-1 induced miR-155 expression and survival mediated by AKT phosphorylation (Hong et al.Gene Ther, 2012). EBV peptides delivered by a virus carrier (Tobacco mosaic virus;TMV) has the potential to boost immunity and stimulate potent T cell responses against EBV-associated antigens and induce a virus specific T cell response against EBV infected malignant cells (Miles/Cairo et al. BJH,2012, Kemnade/McCormick et al. Vaccine, 2014).We previously observed that obinutuzumab (Anti-CD20 mAb) significantly enhanced cell death and increased overall survival against BL (Awasthi/Cairo et al. BJH, 2015) in xenografted NSG mice. However, synergistic effects of obinutuzumab in-combination with LMP1/2-peptide vaccine against mature-B-NHL are unknown. Objective: To determine the efficacy of peptide specific cytotoxic T-lymphocytes (CTL) or the EBV vaccine alone/ in-combination with obinutuzumab against mature-B-NHL Methods: Raji4RH (provided by M. Barth, MD, Roswell Park Cancer Institute) and Raji cells (ATCC, USA) were cultured in 10% RPMI. Tumor cells were incubated with TMV-RIED IgG (LMP2) with obinutuzumab (100ug/ml) for 4 hrs with NK cells. Cytotoxicity was determined by DELFIA cytotoxicity assay at 10:1 E:T ratio. Further, to generate LMP1/LMP2 peptide specific cytotoxic T cells (CTL), mature dendritic cells were pulsated with TMV-conjugated LMP1/LMP2 peptides for 24 hrs. PBMC isolated T cells were mixed with APC (LMPs-mature -DCs) at 1:20 ratio for activation and maturation. LMP-peptide specific CTLs were investigated in-vitro for cytotoxicity efficacy against BL cell lines. Results: LMP1 and LMP2 peptide were successfully conjugated with TMV. TMV conjugated and purified serum vaccine was tested against BL cell lines. Conjugated serum vaccine (LMP2-(RIED-TMV) +obinutuzumab+NK, compared to obinutuzumab+NK or vaccine+NK alone significantly enhanced in-vitro cytotoxicity 62.67±7.82% vs. 53.66±6.43% vs. 50.8±5.2% (p=0.04 and 0.02), respectively against BL (Raji). Furthermore, cytotoxicity of CTL (LMP1-MSD-TMV) or (LMP2-TYG-TMV) cells were significantly enhanced compare to IL2 treated T cells only, 58.5±8.6% or 48.56±15.18% vs. 21.42±13.3% in Raji (P=0.01, 0.02), and 57.8±7.9% or 45.52±19.4% vs. 14.48±4.2% in Raji4RH (P=0.003, 0.002), respectively. Conclusion: Our preliminary data indicates that LMP1 (MSD-TMV) and LMP2 (TYG-TMV) successfully conjugated with TMV and TMV-conjugated peptide specific CTL cells significantly enhanced cytotoxicity against BL cell lines compared to T cells only. Citation Format: Aradhana Awasthi Tiwari, Alison McCormick, Dina Edani, Aaron Newman, Christeen Azmy, Janet Ayello, Christian Klein, Mitchell S. Cairo. EBV peptide-derived vaccine significantly enhanced in vitro cytotoxicity against EBV-positive B-cell lymphoma (EBV-BL) treatment using TMV-based delivery system [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2565.