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Background SEA-CD40 is an investigational, non-fucosylated, humanized monoclonal IgG1 antibody that activates CD40, an immune-activating tumor necrosis factor receptor superfamily member. SEA-CD40 exhibits enhanced binding to activating FcγRIIIa, possibly enabling greater immune stimulation than other CD40 agonists. A first-in-human phase 1 trial was conducted to examine safety, pharmacokinetics, and pharmacodynamics of SEA-CD40 monotherapy in patients with advanced solid tumors and lymphoma. Methods SEA-CD40 was administered intravenously to patients with solid tumors or lymphoma in 21-day cycles with standard 3+3 dose escalation at 0.6, 3, 10, 30, 45, and 60 µg/kg. An intensified dosing regimen was also studied. The primary objectives of the study were to evaluate the safety and tolerability and identify the maximum tolerated dose of SEA-CD40. Secondary objectives included evaluation of the pharmacokinetic parameters, antitherapeutic antibodies, pharmacodynamic effects and biomarker response, and antitumor activity. Results A total of 67 patients received SEA-CD40 including 56 patients with solid tumors and 11 patients with lymphoma. A manageable safety profile was observed, with predominant adverse events of infusion/hypersensitivity reactions (IHRs) reported in 73% of patients. IHRs were primarily ≤grade 2 with an incidence associated with infusion rate. To mitigate IHRs, a standardized infusion approach was implemented with routine premedication and a slowed infusion rate. SEA-CD40 infusion resulted in potent immune activation, illustrated by dose dependent cytokine induction with associated activation and trafficking of innate and adaptive immune cells. Results suggested that doses of 10–30 µg/kg may result in optimal immune activation. SEA-CD40 monotherapy exhibited evidence of antitumor activity, with a partial response in a patient with basal cell carcinoma and a complete response in a patient with follicular lymphoma. Conclusions SEA-CD40 was tolerable as monotherapy and induced potent dose dependent immune cell activation and trafficking consistent with immune activation. Evidence of monotherapy antitumor activity was observed in patients with solid tumors and lymphoma. Further evaluation of SEA-CD40 is warranted, potentially as a component of a combination regimen. Trial registration number NCT02376699.

TPS7586 Background: EO2463 is a therapeutic vaccine designed to activate existing commensal bacteria-specific memory T cells that cross-react with B cell markers in order to drive anti-tumor immune activity against B-cell malignancies. The four microbial-derived, synthetically produced peptides contained in EO2463 (OMP72, OMP64, OMP65, and OMP66), correspond to cytotoxic CD8 T cell HLA-A2 restricted epitopes, and exhibit molecular mimicry with the B cell markers CD20, CD22, CD37, and CD268 (BAFF-receptor), respectively. In pre-clinical models, these peptides can generate strong immune responses and specifically stimulate cross-reactive cytotoxic CD8 T cells to recognize the chosen B cell targets. EO2463 also contains a CD4 helper peptide referred to as universal cancer peptide 2, derived from the human telomerase reverse transcriptase catalytic subunit. The present study is a first-in-human clinical trial of this microbiome-derived peptide therapeutic cancer vaccine approach in patients with follicular lymphoma (FL) and marginal zone lymphoma (MZL). Methods: This four-cohort phase 1/2 trial will investigate EO2463 monotherapy, and combinations of EO2463/lenalidomide (EL), EO2463/rituximab (ER), and EO2463/lenalidomide/rituximab (ER2), for treatment of patients with FL and MZL. Cohort 1 is a safety lead-in dose-finding in patients with relapsed/refractory (RR) disease, with a 3-by-3 design to establish the recommended phase 2 dose (RP2D) for EO2463 monotherapy and to confirm the safety of the RP2D for combination schedules of EL, and ER2. After the recommended EO2463 monotherapy dose is established, cohorts 2, 3, and 4 will open to accrual. Cohort 2 will investigate EO2463 monotherapy in patients with newly diagnosed FL/MZL who are not in need of treatment; cohort 3 will investigate EO2463 monotherapy, followed by ER in patients with limited tumor burden who need treatment, and cohort 4 will further investigate EL, followed by ER2 in the RR setting. EO2463 will be administered SC 4 times at 2-week intervals, followed by continued booster administrations every 4 weeks for 9 (Cohorts 2 and 3) or 12 (Cohorts 1 and 4) months. Inclusion/exclusion criteria, and the design and schedule of the intense immune and safety monitoring will be presented. The safety lead-in dose-finding is currently ongoing, and no safety concerns have been observed thus far. Clinical trial information: NCT04669171.

Abstract Objectives To summarize cases submitted to the 2019 Society for Hematopathology/European Association for Haematopathology Workshop under the category of myeloid/lymphoid neoplasms with eosinophilia and PDGFRA, PDGFRB, or FGFR1 or with PCM1-JAK2 rearrangements, focusing on recent updates and relevant practice findings. Methods The cases were summarized according to their respective gene rearrangement to illustrate the spectrum of clinical, laboratory, and histopathology manifestations and to explore the appropriate molecular genetic tests. Results Disease presentations were heterogeneous, including myeloproliferative neoplasms (MPNs), myelodysplastic syndromes (MDSs), MDS/MPN, acute myeloid leukemia, acute B- or T-lymphoblastic lymphoma/acute lymphoblastic lymphoma (ALL/LBL), or mixed-lineage neoplasms. Frequent extramedullary involvement occurred. Eosinophilia was common but not invariably present. With the advancement of RNA sequencing, cryptic rearrangements were recognized in genes other than PDGFRA. Additional somatic mutations were more frequent in the FGFR1-rearranged cases. Cases with B-ALL presentations differed from Philadelphia-like B-ALL by the presence of an underlying MPN. Cases with FLT3 and ABL1 rearrangements could be potential candidates for future inclusion in this category. Conclusions Accurate diagnosis and classification of this category of myeloid/lymphoid neoplasms has important therapeutic implications. With the large number of submitted cases, we expand our understanding of these rare neoplasms and improve our ability to diagnose these genetically defined disorders.

Abstract Background: Southwest Oncology Group (SWOG) S0016 was a phase III randomized study that compared safety and efficacy of cyclophosphamide, doxorubicin, vincristine, prednisone and rituximab (CHOP-R) with CHOP followed by consolidation with (131) iodine-tositumomab radioimmunotherapy (CHOP-RIT) for previously untreated follicular lymphoma (FL) patients. As reported previously, the study demonstrated excellent outcomes in both arms with 2-year progression-free survival (PFS) of 76% and 80% and 2-year overall-survival (OS) of 97% and 93% in the CHOP-R and CHOP-RIT arms, respectively. (Press. et al. JCO, 2012) We now report the long term outcome of patients who were treated on the S0016 study. Methods: Between 2001 and 2008, 531 previously untreated advanced follicular lymphoma patients were randomized to receive either 6 cycles of CHOP every 3 weeks with 6 doses of rituximab (CHOP-R) or 6 cycles of CHOP every 3 weeks followed by RIT. Patients with advanced-stage disease (bulky stage II, III or IV) with any pathologic grade (1, 2 or 3) were eligible. Results: Patients on CHOP-R (n=264) and CHOP-RIT (n=267) arms had balanced baseline characteristics including age (median 54.5 vs. 53.4 years), presence of B symptoms (29% vs. 26%), pathologic grade 3 (8% vs. 9%), "high" FLIPI risk group (22% vs. 26%), stage IV disease (59% vs. 63%), elevated β2M (53% vs. 55%), bone marrow involvement (56% vs. 55%) and bulky disease (24% vs. 26%). Objective remissions were documented in 226 of 267 eligible patients treated with CHOP-R (85%) and in 226 of 264 patients with CHOP-RIT (86%). Complete remission (CR) rate was 40% in the CHOP-R and 45% in the CHOP-RIT arm. Neutropenia was the most common adverse event (AE) in both arms (48% vs. 51%). Rate of grade 3-5 AEs were not different except for thrombocytopenia which was more common in the CHOP-RIT group (18% vs. 2%). After a median follow-up of 9.6 years (range 0.1 - 14.4 years), the estimated 10-year PFS was 42% (95% CI: 35.6%, 48.5%) in the CHOP-R arm and 57% (95% CI: 50.5%, 63.2%) in the CHOP-RIT arm (p-value = 0.01). 51% of responders on the CHOP-R arm and 38% of responders on the CHOP-RIT arm have relapsed (p-value= 0.01). The estimated 2-year relapse-free survival was 76% for CHOP-R patients and 81% for CHOP-RIT patients (p-value=0.15). There were 48 deaths in the CHOP+R arm and 59 deaths in the CHOP-RIT arm with an estimated 10-year OS of 82% (95% CI: 76.3%, 86.4%) with CHOP-R and 77% (95% CI: 70.5%, 81.4%) with CHOP-RIT (p-value = 0.18). (Figure-1) During the follow-up, 41 patients (15.4%) in the CHOP-R arm and 37 patients (14%) in the CHOP-RIT arm developed secondary malignancies. MDS/AML were more common in the CHOP-RIT arm (11 patients; 4.2%) compared to CHOP-R arm (5 patients; 1.9%) with a relative risk of 2.2 (95% CI: 0.8-6.3) (P-value 0.12). Conclusion: With almost 10 years of follow-up, patients with FL treated on protocol S0016 show outstanding survival in both CHOP-R and CHOP-RIT arms, and represent the best published long-term outcomes to date in this disease. Indeed, almost half of patients enrolled still remain progression-free, confirming registry experiences. While CHOP-RIT provided significantly longer PFS and lower relapse rate compared to CHOP-R in our study, the OS rate was not different between 2 arms due in part to higher incidence of fatal MDS/AML in the CHOP-RIT group, emphasizing the importance of long-term follow-up, and calling into question the validity of PFS as a surrogate for OS in this setting. Given these outstanding outcomes, we believe chemoimmunotherapy should remain the standard induction approach for patients with high-risk FL until long-term follow-up of alternative approaches demonstrates superiority. Support: NIH/NCI grants CA180888, CA180819, CA180821 and in part by GlaxoSmithKline Disclosures Shadman: Emergent: Research Funding; Acerta: Research Funding; Gilead: Honoraria, Research Funding; Pharmacyclics: Honoraria, Research Funding. Rimsza:NCI/NIH: Patents & Royalties: L.M. Rimsza is a co-inventor on a provisional patent, owned by the NCI of the NIH, using Nanostring technology for determining cell of origin in DLBCL.. Gopal:Paid Consultancy- Gilead, Janssen, Seattle Genetics, Spectrum, Research funding- Gilead, Janssen, Pfizer, BMS, Merck, Teva, Takeda, Spectrum, Seattle Genetics: Consultancy, Honoraria, Research Funding. Maloney:Juno Therapeutics: Research Funding; Genentech/Roche: Honoraria. Cheson:Gilead: Research Funding; Pharmacyclics: Membership on an entity's Board of Directors or advisory committees, Research Funding; Acerta: Membership on an entity's Board of Directors or advisory committees, Research Funding. Smith:Amgen: Other: Educational lecture to sales force; TGTX: Consultancy; Celgene: Consultancy; Pharmacyclics: Consultancy; Genentech: Consultancy, Other: on a DSMB for two trials ; Portola: Consultancy; Juno: Consultancy; Gilead: Consultancy; AbbVie: Consultancy. Fisher:Seattle Genetics: Consultancy; Gilead: Consultancy; Johnson and Johnson: Consultancy. Friedberg:Bayer: Other: Data Safety Monitoring Committee. Press:Roche / Genentech: Consultancy, Research Funding.

Abstract Background: The pivotal phase 3 ECHELON-1 study demonstrated superior efficacy of brentuximab vedotin plus doxorubicin, vinblastine and dacarbazine (A+AVD) versus doxorubicin, bleomycin, vinblastine and dacarbazine (ABVD) in patients with previously untreated advanced stage classical Hodgkin lymphoma (cHL) with a 2-year modified progression-free survival (mPFS) of 82.1% in the A+AVD group versus 77.2% in the ABVD group (Hazard Ratio=0.77; 95% confidence interval [CI] 0.60, 0.98; p=0.04). PN is a known toxicity associated with anti-mitotic agents, including vinblastine and the MMAE component of brentuximab vedotin. In the ECHELON-1 study, the incidence of any-grade PN events was 67% (442 of 662 patients) and 43% (286 of 659 patients) in the A+AVD and ABVD arms, respectively; the incidence of grade ≥3 PN was 11% and 2%, respectively. At the time of the initial analysis, 67% of A+AVD-treated patients had either resolution (43%) or improvement (24%) of PN events. A total of the 92% of ongoing PN events were grade 1 (64%) or grade 2 (29%). Here, we report rates of PN resolution and improvement in patients participating in the ECHELON-1 study after long-term follow-up. Methods: Patients with Stage III or IV cHL were randomized 1:1 to receive up to six cycles of A+AVD (n=664) or ABVD (n=670). Pre-existing PN was an exclusion factor at study entry. Peripheral neuropathy was determined on the basis of a standardized MedDRA query; patients who developed PN were monitored throughout the study and those with ongoing PN at end of treatment were followed for resolution or improvement during the post-treatment follow-up period; follow-up visits were scheduled for every 12 weeks ±1 week until 36 months, then every 6 months until study closure. PN resolution was defined as completely resolved and improvement was defined as improved by ≥1 grade from worst grade as of the latest assessment. Results: At the time of the primary analysis, 51% (226/442) and 61% (174/286) of patients in the A+AVD and ABVD arms, respectively, had resolution or improvement of PN events at EOT. Upon continued follow-up (~10 additional months) for approximately 30 months (range 0-78.5) after end of treatment, 76% (335/442) of patients with PN in the A+AVD arm had either complete resolution (59%, 260/442) or improvement (17%, 75/442) of their PN events compared with 82% (234/286) with either resolution (72%) or improvement (10%) in the ABVD arm. In the A+AVD arm, 90% of ongoing PN cases (n=182) were grade 1/2; grade 1=58% (n=106), grade 2=32% (n=58). Residual grade 3 PN was reported in 9% (n=17) of patients (1 patient with grade 4 PN died before resolution). In the ABVD arm, residual PN (n=81) was grade 1 (65%; n=53), grade 2 (30%; n=24), and grade 3 (5%; n=4). For the subset of patients with PN that had not resolved by end of treatment, the median time to resolution of all PN events from AE start date was 28 weeks for A+AVD and 14 weeks for ABVD, the median time to improvement of PN was 39 weeks for A+AVD and 18.5 weeks for ABVD. Conclusions: After approximately 2.5 years of continued follow-up, PN continues to resolve and improve for patients who were treated with A+AVD or ABVD in the ECHELON-1 study. In both study arms, the majority of ongoing PN cases are grade 1 or grade 2. Further follow-up is ongoing. Disclosures Radford: Celgene: Research Funding; ADC Therapeutics: Consultancy, Research Funding; Seattle Genetics: Consultancy, Speakers Bureau; GlaxoSmithKline: Equity Ownership; Takeda: Consultancy, Research Funding, Speakers Bureau; Pfizer: Research Funding; BMS: Consultancy, Speakers Bureau; Novartis: Consultancy, Speakers Bureau; AstraZeneca: Equity Ownership. Connors:Takeda: Research Funding; Seattle Genetics: Honoraria, Research Funding; Roche Canada: Research Funding; Genentech: Research Funding; Cephalon: Research Funding; Bristol Myers-Squibb: Research Funding; Janssen: Research Funding; Bayer Healthcare: Research Funding; NanoString Technologies: Patents & Royalties: Named Inventor on a patent licensed to NanoString Technologies, Research Funding; Merck: Research Funding; F Hoffmann-La Roche: Research Funding; Amgen: Research Funding; Lilly: Research Funding. Younes:Astra Zeneca: Research Funding; J&J: Research Funding; Curis: Research Funding; BMS: Honoraria, Research Funding; Bayer: Honoraria; Takeda: Honoraria; Sanofi: Honoraria; Roche: Honoraria, Research Funding; Janssen: Honoraria, Research Funding; Merck: Honoraria; Seattle Genetics: Honoraria; Celgene: Honoraria; Incyte: Honoraria; Abbvie: Honoraria; Novartis: Research Funding; Pharmacyclics: Research Funding; Genentech: Research Funding. Gallamini:Takeda: Consultancy, Speakers Bureau. Ansell:Affimed: Research Funding; Merck & Co: Research Funding; Regeneron: Research Funding; LAM Therapeutics: Research Funding; Trillium: Research Funding; Pfizer: Research Funding; Takeda: Research Funding; Bristol-Myers Squibb: Research Funding; Celldex: Research Funding; Seattle Genetics: Research Funding. Gopal:Aptevo: Consultancy; Janssen: Consultancy, Research Funding; Merck: Research Funding; Gilead: Consultancy, Research Funding; Brim: Consultancy; Spectrum: Research Funding; Takeda: Research Funding; BMS: Research Funding; Pfizer: Research Funding; Seattle Genetics: Consultancy, Research Funding; Incyte: Consultancy; Teva: Research Funding; Asana: Consultancy. Flinn:Trillium: Research Funding; Calithera: Research Funding; Forma: Research Funding; Portola: Research Funding; Verastem: Research Funding; Janssen: Research Funding; Infinity: Research Funding; Genentech: Research Funding; Forty Seven: Research Funding; Constellation: Research Funding; Merck: Research Funding; Curis: Research Funding; Takeda: Research Funding; Pharmacyclics: Research Funding; Seattle Genetics: Research Funding; Incyte: Research Funding; ArQule: Research Funding; Verastem: Consultancy, Research Funding; Celgene: Research Funding; Agios: Research Funding; Novartis: Research Funding; Gilead: Research Funding; Pfizer: Research Funding; TG Therapeutics: Research Funding; Kite: Research Funding; BeiGene: Research Funding. Pettengell:CTI: Honoraria; Pfizer: Honoraria; Roche: Honoraria; Servier: Honoraria; Takeda: Honoraria. Dlugosz-Danecka:Servier: Consultancy; Roche: Consultancy. Engley:Seattle Genetics: Employment. Fenton:Seattle Genetics, Inc.: Employment, Equity Ownership. Liu:Millennium Pharmaceuticals Inc., a wholly owned subsidiary of Takeda Pharmaceutical Company Limited: Employment. Purevjal:Millennium Pharmaceuticals, Inc., Cambridge, MA, USA, a wholly owned subsidiary of Takeda Pharmaceutical Company Limited: Employment. Miao:Millennium Pharmaceuticals Inc., a wholly owned subsidiary of Takeda Pharmaceutical Company Limited: Employment. Gautam:Millennium Pharmaceuticals, Inc., Cambridge, MA, USA, a wholly owned subsidiary of Takeda Pharmaceutical Company Limited: Employment. Kuruvilla:Janssen: Consultancy, Honoraria, Research Funding; Princess Margaret Cancer Foundation: Research Funding; BMS: Consultancy, Honoraria; Abbvie: Consultancy; Karyopharm: Honoraria; Celgene: Honoraria; Seattle Genetics: Consultancy, Honoraria; Lundbeck: Honoraria; Merck: Consultancy, Honoraria; Amgen: Honoraria; Roche: Consultancy, Honoraria, Research Funding; Gilead: Consultancy, Honoraria; Leukemia and Lymphoma Society Canada: Research Funding.

Abstract Abstract 283 Background: Hodgkin lymphoma (HL) is characterized by the presence of CD30-positive Hodgkin Reed-Sternberg cells. The antibody-drug conjugate (ADC) brentuximab vedotin (SGN-35) delivers the highly potent antimicrotubule agent monomethyl auristatin E (MMAE) to CD30-positive malignant cells by binding specifically to CD30 on the cell surface and releasing MMAE inside the cell via lysosomal degradation. Binding of MMAE to tubulin disrupts the microtubule network within the cell, induces cell cycle arrest, and results in apoptotic death of the CD30-expressing tumor cell. In a previous phase 1 study with brentuximab vedotin dosing every third week, 11 of 12 patients (92%) treated at the maximum tolerated dose of 1.8 mg/kg had tumor reductions and 6 of 12 patients (50%) achieved an objective response (complete remission [CR] + partial remission [PR]). Methods: A pivotal, phase 2, single-arm, multicenter study was conducted to evaluate the efficacy and safety of brentuximab vedotin in patients with relapsed or refractory HL post autologous stem cell transplant (ASCT). Brentuximab vedotin 1.8 mg/kg was administered every 3 weeks as a 30-minute outpatient IV infusion for up to 16 cycles of treatment. The primary endpoint was the overall objective response rate (ORR) as assessed by an independent review facility according to the Revised Response Criteria for Malignant Lymphoma (Cheson 2007). Results: A total of 102 patients with relapsed or refractory HL were treated at 26 study centers. Median age was 31 years (range 15–77) and approximately half of the patients were female (53%). Eastern Cooperative Oncology Group (ECOG) performance status at baseline was 0 (41%) or 1 (59%). All patients had previously received an ASCT and the median number of prior chemotherapy regimens was 4 (range 1–13). More than 70% of the patients had primary refractory disease, defined as failure to achieve a CR or progression within 3 months of completing frontline therapy. In addition, 39% of patients had lymphoma that was refractory to the most recent salvage therapy excluding ASCT. The median duration of brentuximab vedotin treatment on this study was 27 weeks (range 3–54) and the median number of cycles was 9 (range 1–16). The most common (>15%) treatment-related adverse events (AEs) of any grade were peripheral sensory neuropathy (43%), fatigue (40%), nausea (35%), neutropenia (19%), diarrhea (18%), and pyrexia (16%); most events were Grade 1 or 2. Grade 3 treatment-related AEs reported in >1 patient were neutropenia (14%), peripheral sensory neuropathy (5%), thrombocytopenia and hyperglycemia (3% each), and fatigue (2%). The only Grade 4 treatment-related events were neutropenia (4%), and thrombocytopenia, abdominal pain, and pulmonary embolism (1% each). No related Grade 5 events were observed. 18 patients discontinued treatment due to an AE. Consistent with findings from the phase 1 study, 97 patients (95%) had a reduction in tumor size per investigator assessment. Of the 35 patients who had B symptoms at baseline, 29 (83%) experienced resolution of these symptoms. The median time to B symptom resolution was 3 weeks (range <1–16 weeks). To date, 5 patients have received an allogeneic stem cell transplant as their first therapy after discontinuing treatment in the study; all of these patients remain in follow up. Per protocol, no interim analyses were planned for the primary endpoint of ORR by independent review. Independent assessment of ORR is being conducted and final efficacy results will be presented at the meeting. Conclusions: Brentuximab vedotin was associated with manageable adverse events and, based on investigator assessment, demonstrated encouraging activity in heavily pretreated patients with relapsed or refractory HL. Tumor shrinkage was observed in 95% of patients and the B symptom resolution rate was 83%. Final results of the independent assessment of ORR, as well as duration of response, progression-free survival, and updated safety data, will be presented at the meeting. Disclosures: Chen: Seattle Genetics, Inc.: Research Funding. Off Label Use: This clinical trial uses the investigational drug, brentuximab vedotin (SGN-35). Gopal:Seattle Genetics, Inc.: Research Funding. Smith:Seattle Genetics, Inc.: Research Funding. Ansell:Seattle Genetics, Inc.: Research Funding. Rosenblatt:Seattle Genetics, Inc.: Research Funding. Klasa:Seattle Genetics, Inc.: Research Funding. Connors:Seattle Genetics, Inc.: Research Funding. Engert:Seattle Genetics, Inc.: Membership on an entity's Board of Directors or advisory committees, Research Funding. Larsen:Seattle Genetics, Inc.: Employment, Equity Ownership. Kennedy:Seattle Genetics, Inc.: Employment, Equity Ownership. Sievers:Seattle Genetics, Inc.: Employment, Equity Ownership. Younes:Seattle Genetics, Inc.: Honoraria, Research Funding; Genentech: Honoraria, Research Funding; Novartis: Honoraria, Research Funding; SBIO: Honoraria, Research Funding.