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Background: COVID-19 reveals new manifestations not only in the acute phase but also in the long term. The latter is what has been termed as ‘post acute sequelae of SARS-CoV-2 infection’ (PASC) — or “long COVID”— with dyspnea as one of its hallmarks. Cardiopulmonary stress testing (CPET) is increasingly being used to better evaluate such patients. Objective: To compare CPET findings of long COVID patients versus non-COVID patients with undifferentiated dyspnea on exertion seen at Mayo Clinic. Methods: A cohort study was carried out using Mayo Clinic’s exercise testing database. The study group included 77 PASC patients confirmed by a positive antigen or PCR test with no prior history of heart or lung disease. PASC patients were compared to 766 non-COVID patients with unspecified dyspnea without known diagnosis of cardiac or pulmonary disease. ANOVA according to the general linear model and Pearson’s Chi square were used for the bivariate analysis of the quantitative and categorical variables, respectively. Analyses were controlled for age, sex, and beta blocker use as appropriate. Both HR and SBP at rest and peak exercise were significantly different between groups, although the absolute differences were small. Results: Compared with the control group, the post-COVID patients were younger (mean age 47 SD ±14.9 years versus 50.5 SD ±10.1 years) and more likely to be female (70.1% (54 of 77) vs 57.6% (441 of 766)). Although there were many significant differences in the CPET results, the most outstanding were a lower FAC (73 SD ±19.4% vs 85.2 SD ±20.8%) and peak VO2 (22 SD ±6.4 ml/kg/min vs 25.8 SD ±7.37 ml/kg/min) in the study group (p<.0001). Also, CNS changes during CPET were reported at higher rates (19.5% (15 of 77) vs 11.4% (87 of 766)) while dyspnea at lower rates (55.8% (43 of 77) vs 65.7% (503 of 766)) in post-COVID patients (p=0.02). When adjusting for age and sex, weight was significantly higher in the study group (p=0.03) although the absolute difference was modest and BMI remained not significant. PFTs did not suggest any pulmonary abnormalities. Conclusions: We identified a high rate of severe exercise limitation among long COVID patients. Young women may be at higher risk for these complications. Pre-exercise PFTs and absence of objective respiratory limitation during CPET argue against a primary pulmonary cause of the observed limitations, though evaluation of cardiac, autonomic, and muscular impairment is pending. Further studies are warranted to untangle the physiologic abnormalities responsible for these observations.

Computations of heterogeneity dose parameters in GRID therapy remain challenging in many treatment planning systems (TPS). To address this difficulty, we developed reference dose tables for a standard GRID collimator and validate their accuracy. The .decimal Inc. GRID collimator was implemented within the Eclipse TPS. The accuracy of the dose calculation was confirmed in the commissioning process. Representative sets of simulated ellipsoidal tumours ranging from 6–20 cm in diameter at a 3-cm depth; 16-cm ellipsoidal tumours at 3, 6, and 10 cm in depth were studied. All were treated with 6MV photons to a 20 Gy prescription dose at the tumour center. From these, the GRID therapy dosimetric parameters (previously recommended by the Radiosurgery Society white paper) were derived. Differences in D5 through D95 and EUD between different tumour sizes at the same depth were within 5% of the prescription dose. PVDR from profile measurements at the tumour center differed from D10/D90, but D10/D90 variations for the same tumour depths were within 11%. Three approximation equations were developed for calculating EUDs of different prescription doses for three radiosensitivity levels for 3-cm deep tumours. Dosimetric parameters were consistent and predictable across tumour sizes and depths. Our study results support the use of the developed tables as a reference tool for GRID therapy.

Abstract Aims The current definition of post ST-segment elevation myocardial infarction (STEMI) left ventricular (LV) remodelling is purely structural (LV dilatation) and does not consider LV function (ejection fraction, EF), even though it is known to be a predictor of long-term post-STEMI outcome. This study aimed to reclassify LV remodelling after STEMI by integrating LV dilatation and function (LVEF) and to investigate the prognostic implications. Methods and results Data from an ongoing registry of STEMI patients who were treated with primary percutaneous coronary intervention (PCI) were retrospectively evaluated. Four distinct remodelling subgroups were identified: (i) no LV dilatation, no LVEF impairment,(ii) no LV dilatation but LVEF impairment, (iii) LV dilatation but no LVEF impairment, and (iv) LV dilatation and LVEF impairment. The impact of functional LV remodelling on outcomes was analysed. A total of 2346 patients were studied (mean age 60 ± 11 years, 76% men). During a median follow-up of 76 (interquartile range 52 to 107) months, 282 (12%) died, while the composite of death and heart failure hospitalization occurred in 305 (13%) patients. Those with LV remodelling and LVEF impairment had a significantly lower survival rate (P &lt; 0.001) and event-free survival rate (P &lt; 0.001) compared with other functional LV remodelling groups. Conclusions Employing a functional LV post-infarct remodelling classification has the potential to improve risk stratification beyond structural LV remodelling alone. Identification of patients with the worst prognosis by using a functional LV remodelling approach may allow institution of early preventative therapies.

Background: cGMP MANP (M-atrial natriuretic peptide) is a best-in-class activator of the pGC-A (particulate guanylyl cyclase A) receptor. Furosemide increases the effectiveness of antihypertensive agents, but activates renin-angiotensin-aldosterone system. We aimed to investigate for the first time cardiorenal and neurohumoral actions of MANP in a genetic model of hypertension in spontaneously hypertensive rats. We also assessed how MANP would potentiate the blood pressure (BP)–lowering actions of furosemide while reducing the production of aldosterone. Methods: Spontaneously hypertensive rats (N=60) were randomized in vehicle, MANP, furosemide, or MANP+furosemide groups. Furosemide (1, 5, 10 mg/kg) was given as a single bolus which in MANP+furosemide groups was followed by a 60-minute infusion of MANP. Results: BP was reduced in MANP300 (300 pmol/[kg·min]) and MANP600 (600 pmol/[kg·min]) groups ( P <0.05) and was accompanied by significant increase in plasma cyclic guanosine monophosphate. Furosemide alone reduced BP but less compared with MANP with no change in plasma cyclic guanosine monophosphate. MANP+furosemide resulted in the greatest BP reduction and significant increase in plasma cyclic guanosine monophosphate in Fs5+MANP300, Fs10+MANP300, and Fs10+MANP600. Plasma aldosterone increased in furosemide groups, which was significantly attenuated in MANP+furosemide groups. Natriuresis and diuresis increased in all treated groups ( P <0.05) with no significant differences between furosemide and furosemide+MANP. In vitro, MANP increased cyclic guanosine monophosphate level in human vascular cells. Conclusions: We provide novel evidence that MANP potentiates the BP-lowering actions of furosemide, suppresses the activation of renin-angiotensin-aldosterone system, and preserves renal function. These data are highly relevant to clinical needs in the treatment of hypertension and heart failure.

AbstractPreclinical data demonstrated that combining an anti–programmed cell death 1 (PD-1) inhibitor with a cyclin-dependent kinase 9 (CDK9) inhibitor provided enhanced antitumor activity with no significant toxicities, suggesting this combination may be a potential therapeutic option. The multicohort, phase 1 KEYNOTE-155 study evaluated the safety and antitumor activity of the PD-1 inhibitor pembrolizumab plus the CDK9 inhibitor dinaciclib in patients with relapsed or refractory (rr) chronic lymphocytic leukemia (CLL), diffuse large B-cell lymphoma (DLBCL) and multiple myeloma (MM). Patients enrolled were ≥18 years of age with a confirmed diagnosis of CLL, DLBCL, or MM. The study included 2 phases: a dose-evaluation phase to determine dose-limiting toxicities and a signal-detection phase. Patients received pembrolizumab 200 mg every 3 weeks plus dinaciclib 7 mg/m2 on day 1 and 10 mg/m2 on day 8 of cycle 1 and 14 mg/m2 on days 1 and 8 of cycles 2 and later. Primary endpoint was safety, and a key secondary endpoint was objective response rate (ORR). Seventy-two patients were enrolled and received ≥1 dose of study treatment (CLL, n = 17; DLBCL, n = 38; MM, n = 17). Pembrolizumab plus dinaciclib was generally well tolerated and produced no unexpected toxicities. The ORRs were 29.4% (5/17, rrCLL), 21.1% (8/38, rrDLBCL), and 0% (0/17, rrMM), respectively. At data cutoff, all 72 patients had discontinued treatment, 38 (52.8%) because of progressive disease. These findings demonstrate activity with combination pembrolizumab plus dinaciclib and suggest that a careful and comprehensive approach to explore anti–PD-1 and CDK9 inhibitor combinations is warranted. This trial was registered at www.clinicaltrials.gov as NCT02684617.

Background and Objectives: The development and severity of colonic diverticulosis and non-alcoholic fatty liver disease (NAFLD) has been associated with several components of metabolic syndrome (MetS). Therefore, this study aimed to evaluate a possible connection between NAFLD, colonic diverticulosis, and MetS. Materials and Methods: This retrospective study included patients diagnosed with diverticulosis between January 2017 and December 2019. Data regarding the patient demographics, Diverticular Inflammation and Complication Assessment (DICA) score and category, disease localization, hepatic steatosis, blood pressure, comprehensive metabolic panel, need for colonic surgery, and co-morbidities were collected from medical records. Results: A total of 407 patients with a median age of 68 years (range, 34–89 years) were included (male: 53.81%). The majority was diagnosed with left-sided diverticulosis (n = 367, 90.17%) and an uncomplicated disease course (DICA category 1, n = 347, 85.3%). Concomitant hepatic steatosis was detected in 47.42% (n = 193) of patients. The systolic blood pressure, triglycerides, total cholesterol, C-reactive protein (CRP), and fasting glucose were higher in the NAFLD group (p < 0.001, p < 0.001, p < 0.001, p < 0.001, and p < 0.001, respectively). A higher prevalence of hypertension (HTA), type 2 diabetes mellitus (T2DM), and hypothyroidism was noted in the same group of patients (p < 0.001, p < 0.001, and p = 0.008, respectively). High-density lipoprotein cholesterol was lower in patients with more severe forms of diverticulosis (DICA category 2 and 3), while CRP levels were significantly higher (p = 0.006 and p = 0.015, respectively). HTA and NAFLD were more common in patients with more severe forms of colonic diverticulosis (p = 0.016 and p = 0.025, respectively). Using a multivariate logistic regression, the DICA score, CRP, total cholesterol, HTA, and hypothyroidism were identified as discriminating factors for the presence of hepatic steatosis. Conclusion: Components of metabolic dysregulation were prominent in patients diagnosed with colonic diverticulosis and concomitant hepatic steatosis. HTA, T2DM, and hypothyroidism were more frequently observed in this group. Hepatic steatosis was more commonly detected in more severe forms of colonic diverticulosis.

Abstract Introduction POEMS syndrome is a rare disease associated with a plasma cell dyscrasia with limited information regarding the role of ASCT. Small single institution series have demonstrated deep and durable responses after ASCT along with neurological improvement. Despite these benefits, ASCT is thought to have higher treatment related morbidity and mortality, limiting its use. We describe the outcomes from an international multicenter database of patients with POEMS syndrome undergoing ASCT. Methods We performed a retrospective analysis using the Center for International Blood and Marrow Transplant Research (CIBMTR) database to evaluate the outcomes of patients undergoing ASCT for POEMS syndrome. Standard descriptive methods were used to report patient characteristics. Univariate and multivariate analysis were performed to identify predicators for non-relapse mortality (NRM), relapse, progression-free and overall survival (PFS, OS). NRM was compared between POEMS and multiple myeloma (MM) patients who underwent ASCT during the same time period. Results Between 2008-2018, 331 pts with POEMS syndrome who underwent ASCT were identified. The median age was 51 years, with 66% males. Racial distribution was 65% Caucasians, 19% African American, 5% other, and 10% missing. Pre-transplant characteristics included 70% patients had Karnofsky score &lt;90, and 50% had HCT-CI ≥ 3, reflecting underlying disease severity and symptoms. The most common comorbidity was pulmonary (52%). Only 14% of patients were in very good partial response or better at the time of ASCT and 72 (22%) patients underwent ASCT without prior treatment. The median time from diagnosis to ASCT was 7 months and 74% underwent ASCT within 12 months of diagnosis. The most common mobilization strategy was GCSF +/- plerixafor in 50% of pts and 87% of pts received conditioning with 200mg/m2 of Melphalan. The median follow up was 48 (range 3-137) months. At day 100, NRM was 0.9 % (95% CI: 0.2-2.2%). At 4 years, NRM was 4.9% (95% CI: 2.6-7.9%), relapse 15.4% (95% CI 11.3-20.1%), PFS 79.7% (95% CI 74.5-84.3%) and OS 92% (95% CI 89.2-95.6%). Subsequent neoplasms were seen in 16 (5%) with 4 myeloid malignancy and 12 solid tumors. On multivariate analysis, age ≥ 60 years was associated with greater hazards of mortality, HR 2.6 (95% CI 1.2-5.6), p 0.01. The figure shows the comparable NRM between POEMS and MM (p 0.31). Conclusions: We report outcomes of the largest ASCT series of POEMS patients. Despite a high HCT-CI and low functional status among patients with POEMS syndrome, no difference in NRM was seen when compared to MM. Post-transplant outcomes were excellent and support single center data on the role of ASCT in this rare disease. Figure 1 Figure 1. Disclosures Kansagra: Oncopeptides: Membership on an entity's Board of Directors or advisory committees; Takeda: Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees; Sanofi: Membership on an entity's Board of Directors or advisory committees; BMS: Membership on an entity's Board of Directors or advisory committees; Alynylam: Membership on an entity's Board of Directors or advisory committees; Cota Health: Membership on an entity's Board of Directors or advisory committees; GSK: Membership on an entity's Board of Directors or advisory committees; Karyopharm: Membership on an entity's Board of Directors or advisory committees; Pharmacyclics: Membership on an entity's Board of Directors or advisory committees; Pfizer: Membership on an entity's Board of Directors or advisory committees. Dispenzieri: Alnylam: Research Funding; Pfizer: Research Funding; Sorrento Therapeutics: Consultancy; Takeda: Research Funding; Oncopeptides: Consultancy; Janssen: Consultancy, Research Funding. Kumar: Abbvie: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Merck: Research Funding; BMS: Consultancy, Research Funding; Oncopeptides: Consultancy; Beigene: Consultancy; KITE: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Roche-Genentech: Consultancy, Research Funding; Astra-Zeneca: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Antengene: Consultancy, Honoraria; Novartis: Research Funding; Bluebird Bio: Consultancy; Celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding; Amgen: Consultancy, Research Funding; Carsgen: Research Funding; Janssen: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Tenebio: Research Funding; Takeda: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Adaptive: Membership on an entity's Board of Directors or advisory committees, Research Funding; Sanofi: Research Funding. Qazilbash: Bristol-Myers Squibb: Other: Advisory Board; NexImmune: Research Funding; Janssen: Research Funding; Biolline: Research Funding; Oncopeptides: Other: Advisory Board; Angiocrine: Research Funding; Amgen: Research Funding. Shah: GSK: Consultancy; Karyopharm: Consultancy; Oncopeptides: Consultancy; Indapta Therapeutics: Consultancy; Janssen: Research Funding; Nektar: Research Funding; Bluebird Bio: Research Funding; Teneobio: Research Funding; CareDx: Consultancy; BMS/Celgene: Research Funding; Sanofi: Consultancy; Sutro Biopharma: Research Funding; CSL Behring: Consultancy; Poseida: Research Funding; Precision Biosciences: Research Funding; Amgen: Consultancy; Kite: Consultancy. D'Souza: Sanofi, Takeda, Teneobio, CAELUM, Prothena: Research Funding; Imbrium, Pfizer, BMS: Membership on an entity's Board of Directors or advisory committees; Janssen, Prothena: Consultancy.

Abstract Introduction: Idecabtagene vicleucel (ide-cel, bb2121) is the first chimeric antigen receptor (CAR) T cell therapy approved for the treatment of relapsed or refractory multiple myeloma after four or more prior lines of therapy, including an immunomodulatory agent, a proteasome inhibitor, and an anti-CD38 monoclonal antibody. bb21217 is a B-cell maturation antigen (BCMA) directed CAR T cell therapy which uses the same CAR molecule as ide-cel, with the addition of a PI3K inhibitor (bb007) during ex vivo culture to enrich the drug product (DP) for memory-like T cells and decrease the proportion of highly differentiated or senescent T cells. We hypothesize that DPs enriched for memory like CAR T cells will persist and function longer than non-enriched DPs and this increased persistence will positively influence duration of response (DOR). We previously demonstrated patients with sustained response are more likely to have drug product enriched for naïve gene signatures and depleted of effector gene signatures compared to patients without a sustained response. Methods: CRB-402 (NCT03274219) is a multi-center phase 1 trial of bb21217 in RRMM patients who received ≥3 prior lines of antimyeloma therapy, including a proteasome inhibitor and an immunomodulatory agent, or are double-refractory to both classes. In expansion, patients were required to have prior exposure to an anti-CD38 antibody and were required to be refractory to their last line of therapy. Patients underwent lymphodepletion with fludarabine (30 mg/m 2) and cyclophosphamide (300 mg/m 2) daily for 3 days, then received a single infusion of bb21217 at 150, 300 or 450 x 10 6 CAR+ T cells. The primary outcome measure is incidence of adverse events (AEs), including dose-limiting toxicities (DLTs). Additional outcome measures include overall response rate and DOR by IMWG Uniform Response Criteria. Exploratory analyses include correlation of outcome with the molecular characteristics of materials collected temporally through the treatment course, including PBMCs at apheresis, CAR+ T cells from drug product and CAR+ T cells collected from patients around the time of peak expansion. Results: Asof Feb 16, 2021, 72 patients received bb21217, 12 at 150, 14 at 300 and 46 at 450 x 10 6 CAR+ T cells; median follow up for all patients is 9.0 (&lt;1-36) months (M). Patients had a median of 6 (3-17) prior lines of therapy with 49/72 (68%) triple refractory. Cytokine release syndrome (CRS) developed in 54/72 (75%) patients and was predominately G1/2 (51 pts), with 1 G3 event and 2 deaths (previously reported). Median time to first onset of CRS was 2 days (1-20); tocilizumab (38 pts) + corticosteroids (12 pts) was used to manage CRS. Eleven (15%) patients developed neurotoxicity [8 G1/G2, 2 G3, 1 G4] with median time to first onset of 7 (2-24) days. Response was assessed per investigator for 72 patients treated with bb21217 (Table). CAR+ T cells remained detectable in 30/37 (81%) patients and 9/15 (60%) patients at 6 and 12 M respectively, post bb21217 infusion. Of the 15 patients evaluable for MRD with ≥CR, 14 (93%) were MRD negative at 10 -5 by NGS. Analysis of peripheral blood samples collected 15 days post bb21217 infusion demonstrated patients with higher than the median number of CD8+ CAR+ T cells expressing CD27 and CD28 had significantly longer DOR (p=0.0024), compared to patients with lower than the median values. This suggests less differentiated, more proliferative CAR+ T cells at peak expansion are associated with prolonged disease response (median DOR in high vs low: 27.2M (95% CI; 16.8, NE) vs 9.4M (95% CI; 5.1, NE). Conclusions: Adverse events are consistent with known toxicities of CAR T cell therapies. Efficacy results are encouraging with a median DOR estimate of 17M, CR rate continues to mature. Patients with higher levels of proliferative, less differentiated memory like CAR+ T cells at peak expansion are more likely to experience prolonged DOR, continuing to support the hypothesis that the memory like T cell phenotype associated with bb21217 results in prolonged DOR. Figure 1 Figure 1. Disclosures Raje: Caribou: Other; Janssen: Other; bluebird bio: Other; Amgen: Other; Celgene: Other; BMS: Other. Shah: Poseida: Research Funding; Precision Biosciences: Research Funding; Sanofi: Consultancy; Sutro Biopharma: Research Funding; Karyopharm: Consultancy; Janssen: Research Funding; Oncopeptides: Consultancy; Kite: Consultancy; Nektar: Research Funding; Indapta Therapeutics: Consultancy; GSK: Consultancy; CSL Behring: Consultancy; CareDx: Consultancy; BMS/Celgene: Research Funding; Bluebird Bio: Research Funding; Amgen: Consultancy; Teneobio: Research Funding. Kaufman: BMS: Consultancy, Research Funding; Tecnofarma SAS, AbbVie: Honoraria; Incyte, celgene: Consultancy; Janssen: Honoraria; Incyte, TG Therapeutics: Membership on an entity's Board of Directors or advisory committees; Heidelberg Pharma: Research Funding; Amgen: Research Funding; Fortis Therapeutics: Research Funding; Novartis: Research Funding; Roche/Genetech, Tecnopharma: Consultancy, Honoraria; Sutro, Takeda: Research Funding; Genentech, AbbVie, Janssen: Consultancy, Research Funding. Siegel: Celularity: Membership on an entity's Board of Directors or advisory committees; GlaxoSmithKline: Honoraria, Speakers Bureau; Takeda: Honoraria; Bristol Myers Squibb: Honoraria, Speakers Bureau; Amgen Inc.: Honoraria; Karyopharm: Honoraria; Janssen: Honoraria, Speakers Bureau. Munshi: Janssen: Consultancy; Bristol-Myers Squibb: Consultancy; Legend: Consultancy; Adaptive Biotechnology: Consultancy; Amgen: Consultancy; Takeda: Consultancy; Abbvie: Consultancy; Novartis: Consultancy; Celgene: Consultancy; Oncopep: Consultancy, Current equity holder in publicly-traded company, Other: scientific founder, Patents & Royalties; Karyopharm: Consultancy; Pfizer: Consultancy. Rosenblatt: Parexel: Consultancy; Karyopharm: Membership on an entity's Board of Directors or advisory committees; Imaging Endpoints: Consultancy; Attivare: Consultancy; Wolters Kluwer Health Inc: Consultancy, Patents & Royalties. Lin: Sorrento: Consultancy; Takeda: Research Funding; Juno: Consultancy; Celgene: Consultancy, Research Funding; Merck: Research Funding; Vineti: Consultancy; Legend: Consultancy; Bluebird Bio: Consultancy, Research Funding; Novartis: Consultancy; Gamida Cell: Consultancy; Kite, a Gilead Company: Consultancy, Research Funding; Janssen: Consultancy, Research Funding. Jakubowiak: BMS: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; Abbvie: Membership on an entity's Board of Directors or advisory committees; Gracell: Membership on an entity's Board of Directors or advisory committees; GSK: Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees; Karyopharm: Membership on an entity's Board of Directors or advisory committees; Amgen: Membership on an entity's Board of Directors or advisory committees; Sanofi: Membership on an entity's Board of Directors or advisory committees. Timm: bluebird bio: Current Employment. Yeri: bluebird bio: Current Employment. Martin: Bristol Myers Squibb: Current Employment, Current equity holder in publicly-traded company. Campbell: Bristol Myers Squibb: Current Employment, Current holder of individual stocks in a privately-held company. Finney: bluebird bio: Current Employment, Current equity holder in publicly-traded company. Truppel-Hartmann: bluebird bio: Current Employment. Petrocca: blue bird bio: Ended employment in the past 24 months. Berdeja: Abbvie, Acetylon, Amgen: Research Funding; Celularity, CRISPR Therapeutics: Research Funding; Bluebird bio, BMS, Celgene, CRISPR Therapeutics, Janssen, Kite Pharma, Legend Biotech, SecuraBio, Takeda: Consultancy; EMD Sorono, Genentech: Research Funding; GSK, Ichnos Sciences, Incyte: Research Funding; Lilly, Novartis: Research Funding; Poseida, Sanofi, Teva: Research Funding.

Abstract Background: Chemoimmunotherapy is considered standard initial therapy for follicular lymphoma (FL) with high tumor burden (HTB). Obinutuzumab and Bendamustine (OB) with maintenance Obinutuzumab (mO) is considered a standard therapy for the frontline treatment of HTB FL (GALLIUM, Marcus et al, NEJM 2017). Venetoclax (VEN), an oral BCL2 inhibitor, is an attractive target in FL given the high BCL2 expression; though single agent activity has been disappointing (Davids et al. JCO 2017). BCL2 inhibition is thought to be synergistic with chemotherapy. Thus, the PrE0403 study evaluated the OB-VEN combination in frontline HTB FL. Here we present end of induction (EOI) outcomes. Methods: The primary objective of this Phase II study was to estimate the complete remission (CR) rate at EOI. Potential participants must have had a histologically confirmed diagnosis of FL grade 1, 2, or 3a with HTB defined by GELF or high risk defined by FLIPI-1 criteria. They must have had adequate performance status and organ function. Notably, creatinine clearance must have been ≥50 mL/min. Participants must have not had prior treatment for FL. Eligible participants were treated with Bendamustine IV 90 mg/m2 Day (D) 1 & 2, Obinutuzumab IV 100 mg D1, 900 mg D2, 1000 mg D8 and D15 of Cycle (C) 1 then D1 of each cycle, and VEN 800 mg orally daily D1-10 every 28 days for 6 total cycles. Due to a high rate of laboratory tumor lysis syndrome (TLS) during C1 in the first 21 patients, VEN was removed from C1 and given in C2-6 only. Participants with a CR at EOI were treated with mO IV 1000 mg D1 every 8 weeks for 2 years. Those with a partial response (PR) or stable disease (SD) were treated with mO as well as VEN 800 mg orally daily for 2 years. Pneumocystis jiroveci Pneumonia (PJP) and antiviral prophylaxis was required as was G-CSF support. Response was assessed via Lugano Criteria at EOI including PET/CT and bone marrow assessment. Adverse Events (AEs) were evaluated using CTCAE v5.0. To be considered promising, OB-VEN should improve the null hypothesis CR rate of 50% (OB) to 65%. With an 85% power and a one sided 15% type I error, 56 participants would be needed with an estimated 51 eligible. Support for the study was from Genentech, Member of the Roche Group. Results A total of 56 participants were enrolled and treated between 12/2017 and 11/2020; baseline characteristics are listed in Table 1. TLS was closely monitored in C1 and 8/21 participants developed TLS when VEN was administered in C1; 0/35 when it was not. However, monitoring for TLS in C1 became less stringent when VEN was not administered. Treatment related Grade ≥3 toxicities occurred in 47/56 participants (83.9%) with serious adverse events in 31 of 56 (55.5%). Atypical infections were seen; there was one treatment related death on study due to cytomegalovirus (CMV) encephalitis as well as PJP pneumonia which occurred after induction C6. Enrollment was temporarily suspended and CMV monitoring was implemented with no further occurrences. Another participant receiving mO later developed BK virus nephropathy following mO C6 and now requires ongoing hemodialysis. Another was diagnosed with Respiratory Syncytial Virus pneumonia 30 days after C6 and later PJP pneumonia after C2 of mO. Common (incidence &gt;10%) AEs during induction are listed in Table 2. 45 of 56 (80.4%) participants were able to receive all 6 cycles of OB-VEN. CR was seen in 41 of 56 participants (73.2%, 2 sided 95% Confidence Interval (CI) 59.7-84.2%) at the EOI. 30 participants (53.5%) went onto maintenance. With a median follow up of 20.9 months, estimated 2 year Overall Survival (OS) and Progression-Free Survival (PFS) (90% CI) is 94.4% (82.4-98.3%) and 85.8% (68.8-93.9%) respectively. Conclusions This Phase II study of OB-VEN in untreated HTB FL showed high CR rate and met its primary endpoint with early signs of prolonged PFS. Laboratory TLS was identified but it was unclear if attributed solely to VEN, as baseline laboratory TLS rate for OB is unknown. The rate of Grade ≥3 AE of 83.9% (compared to 69% for OB in GALLIUM, Hiddeman JCO 2018) and the observation of opportunistic infections including CMV encephalitis, PJP pneumonia and BK nephropathy, suggests the combination is highly immunosuppressive. Therefore, while the study met its primary outcome, the combination of OB-VEN at 800 mg for 10 days, plus mO, does not have an acceptable risk/benefit profile. Participants will continue to be followed for efficacy and safety during the maintenance phase. Figure 1 Figure 1. Disclosures Portell: Acerta/AstraZeneca: Research Funding; SeaGen: Research Funding; Pharmacyclics: Honoraria; Xencor: Research Funding; Aptitude Health: Honoraria; BeiGene: Honoraria, Research Funding; Abbvie: Research Funding; TG Therapeutics: Honoraria, Research Funding; Kite: Honoraria, Research Funding; Merck: Honoraria, Research Funding; Morphosys: Honoraria; Targeted Oncology: Honoraria; Genentech: Research Funding; VelosBio: Research Funding. Nowakowski: MorphoSys: Consultancy; Incyte: Consultancy; Kymera Therapeutics: Consultancy; TG Therapeutics: Consultancy; Blueprint Medicines: Consultancy; Nanostrings: Research Funding; Roche: Consultancy, Research Funding; Genentech: Consultancy, Research Funding; Celgene/Bristol Myers Squibb: Consultancy, Research Funding; Zai Labolatory: Consultancy; Daiichi Sankyo: Consultancy; Bantham Pharmaceutical: Consultancy; Curis: Consultancy; Karyopharm Therapeutics: Consultancy; Selvita: Consultancy; Ryvu Therapeutics: Consultancy; Kyte Pharma: Consultancy. Cohen: Janssen, Adicet, Astra Zeneca, Genentech, Aptitude Health, Cellectar, Kite/Gilead, Loxo, BeiGene, Adaptive: Consultancy; Genentech, BMS/Celgene, LAM, BioINvent, LOXO, Astra Zeneca, Novartis, M2Gen, Takeda: Research Funding. Kahl: AbbVie, Acerta, ADCT, AstraZeneca, BeiGene, Genentech: Research Funding; AbbVie, Adaptive, ADCT, AstraZeneca, Bayer, BeiGene, Bristol-Myers Squibb, Celgene, Genentech, Incyte, Janssen, Karyopharm, Kite, MEI, Pharmacyclics, Roche, TG Therapeutics, and Teva: Consultancy. OffLabel Disclosure: Venetoclax is not approved for follicular lymphoma or in combination with bendamustine and obinutuzumab

Abstract Background Prognosis is poor for patients (pts) with relapsed/refractory multiple myeloma (RRMM; median overall survival: &lt;1 year), indicating a clear need to identify agents with novel mechanisms of action. B-cell maturation antigen (BCMA) has recently emerged as a novel treatment target for MM due to its highly selective expression in plasma cells. TNB-383B, a BCMA x CD3 T-cell engaging bispecific antibody, was designed to overcome the toxicity limitations of existing BCMA therapies and has demonstrated promising results in an ongoing first-in-human phase 1 study in pts with RRMM (Rodriguez C, et al. Blood 2020;136[suppl 1]:43-44). Herein, we report the updated efficacy and safety outcomes of this phase 1 study. Methods This multicenter, phase 1, open-label, dose-escalation/expansion study (NCT03933735) enrolled pts with RRMM (≥3 prior lines of therapy that included a proteasome inhibitor, an immunomodulatory drug, and an anti-CD38 monoclonal antibody), estimated glomerular filtration rate ≥30 mL/min as calculated by the Modification of Diet in Renal Disease formula, and ECOG performance status ≤2. Prior BCMA-targeted therapy is prohibited. Primary objectives include safety/tolerability, pharmacokinetics (PK), and determination of recommended phase 2 dose (RP2D); secondary objectives include assessment of clinical activity (per IMWG criteria 2016). TNB-383B is administered intravenously over 1-2 hours every 3 weeks (Q3W) with the first dose administered inpatient. The study uses a 3+3 design with backfilling for dose and permits intrapatient dose escalation to highest safe dose. Dose expansion was initiated on selection of RP2D. Pts are treated until progression, unacceptable toxicity, or other discontinuation criteria are met. The efficacy-evaluable population includes all pts who received at least 1 dose of TNB-383B and have at least 1 postdose assessment. The safety population includes all pts who received at least 1 dose of study drug; adverse events (AEs) are graded according to NCI CTCAE v5.0. Results As of 10 May 2021, 103 pts (dose escalation, n=73; dose expansion, n=30) have been treated with TNB-383B (0.025-120 mg). The RP2D of 60 mg Q3W was selected on the basis of tolerability, safety, PK, and clinical activity. Pt demographics and baseline characteristics are summarized in Table 1. Three dose-limiting toxicities were reported in dose escalation (platelet count decreased: grade [Gr] 4, 60 mg; cytokine release syndrome [CRS]: Gr 3, 90 mg and 120 mg); none were reported as serious. Treatment-related AEs (TRAEs) were reported in 79 (77%) pts, with Gr ≥3 and serious AEs occurring in 33 (32%) and 23 (22%) pts, respectively. The most common TRAEs (Table 2) include CRS (n=54, 52%), neutropenia (n=18, 17%), and fatigue (n=14, 14%). At the RP2D (n=39), the Gr ≥3 CRS rate was 3% (n=1). Onset of CRS typically occurred on the same or next day following the first dose and all pts recovered using tocilizumab or standard supportive care measures. Treatment-emergent AEs (TEAEs) of infusion-related reactions were reported in 8 (8%) pts and infections occurred in 29 (28%) pts; pneumonia (n=5, 5%) and upper respiratory tract infection (n=4, 4%) were the most common. Five deaths from TEAEs were reported; all were unrelated to study drug. Forty-two (40%) pts discontinued treatment due to disease progression. In the dose-escalation cohorts of ≥40 mg Q3W (n=24), the objective response rate (ORR) was 79% (19/24), with a very good partial response or better (≥VGPR) rate of 63% (15/24), and a complete response (CR) rate of 29% (7/24) at the data cutoff date; these pts have the longest follow-up (ie, mature data) with median time on study of 6.1 months (Figure 1). At doses ≥40 mg in the combined dose-escalation and -expansion cohorts (n=44), the observed ORR, ≥VGPR, and CR rates were 64% (28/44), 43% (19/44), and 16% (7/44), respectively; these pts have shorter follow-up (ie, immature data) with median time on study of 3.1 months. Twenty-nine (66%) of the 44 pts administered ≥40 mg were triple-class refractory and reported an ORR of 55% (16/29). Conclusions TNB-383B in pts with RRMM is well tolerated with an ORR of 79% observed at doses ≥40 mg in the dose-escalation cohorts. Despite having a shorter follow-up period, this trend was also observed at doses ≥40 mg in the combined dose-escalation/expansion cohorts (ORR: 64%). Enrollment into the dose-expansion arm is ongoing; updated data will be presented at the meeting. Figure 1 Figure 1. Disclosures Kumar: Novartis: Research Funding; Carsgen: Research Funding; KITE: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Takeda: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Astra-Zeneca: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Merck: Research Funding; Roche-Genentech: Consultancy, Research Funding; Bluebird Bio: Consultancy; Janssen: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding; Amgen: Consultancy, Research Funding; Beigene: Consultancy; Oncopeptides: Consultancy; Antengene: Consultancy, Honoraria; Tenebio: Research Funding; BMS: Consultancy, Research Funding; Abbvie: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Adaptive: Membership on an entity's Board of Directors or advisory committees, Research Funding; Sanofi: Research Funding. D'Souza: Imbrium, Pfizer, BMS: Membership on an entity's Board of Directors or advisory committees; Sanofi, Takeda, Teneobio, CAELUM, Prothena: Research Funding; Janssen, Prothena: Consultancy. Shah: Oncopeptides: Consultancy; Nektar: Research Funding; Poseida: Research Funding; Janssen: Research Funding; Indapta Therapeutics: Consultancy; GSK: Consultancy; CareDx: Consultancy; BMS/Celgene: Research Funding; Bluebird Bio: Research Funding; CSL Behring: Consultancy; Teneobio: Research Funding; Kite: Consultancy; Sutro Biopharma: Research Funding; Karyopharm: Consultancy; Amgen: Consultancy; Precision Biosciences: Research Funding; Sanofi: Consultancy. Rodriguez: Takeda: Consultancy, Speakers Bureau; Karyopharm: Consultancy, Speakers Bureau; Janssen: Consultancy, Speakers Bureau; BMS: Consultancy, Speakers Bureau; Oncopeptides: Consultancy, Honoraria; Amgen: Consultancy, Speakers Bureau. Voorhees: AbbVie Inc, Bristol-Myers Squibb Company; Consulting Agreement: GlaxoSmithKline, Novartis, Oncopeptides: Other: Advisory Committee; Bristol-Myers Squibb Company.: Other: Data Safety & Monitoring. Bueno: AbbVie: Current Employment, Current equity holder in publicly-traded company. Buelow: Teneobio, Inc.: Current Employment, Current holder of stock options in a privately-held company. Freise: Abbvie, Inc.: Current Employment, Current equity holder in publicly-traded company, Current holder of individual stocks in a privately-held company. Yue: Abbvie, Inc.: Current Employment, Current equity holder in publicly-traded company, Current holder of individual stocks in a privately-held company. Pothacamury: AbbVie: Current Employment, Current equity holder in publicly-traded company, Current holder of individual stocks in a privately-held company. Polepally: Abbvie, Inc.: Current Employment, Current equity holder in publicly-traded company, Current holder of individual stocks in a privately-held company. Vij: BMS: Research Funding; Takeda: Honoraria, Research Funding; Sanofi: Honoraria, Research Funding; BMS: Honoraria; GSK: Honoraria; Oncopeptides: Honoraria; Karyopharm: Honoraria; CareDx: Honoraria; Legend: Honoraria; Biegene: Honoraria; Adaptive: Honoraria; Harpoon: Honoraria.