Kurzfassung: Introduction: Patients (pts) with higher-risk myelodysplastic syndromes (MDS) are typically treated with azacitidine (Aza). Venetoclax (Ven) is a selective, potent, oral BCL-2 inhibitor that has demonstrated synergy with Aza in preclinical studies of myeloid malignancies. Higher-risk MDS is associated with mutations in genes involved in RNA splicing, epigenetic regulation, transcription, and cellular signaling. Assessing the dynamics of genetic variants during treatment of higher-risk MDS enables understanding of the molecular determinants of response. This phase 1b study (NCT02942290) evaluates Ven + Aza for treatment-naïve higher-risk MDS, and we report efficacy among mutationally defined subgroups as well as the depth of molecular response. Methods: Pts (≥18 years) with higher-risk MDS enrolled in the study had International Prognostic Scoring System intermediate-2 or high-risk MDS, bone marrow (BM) blasts & lt;20% at baseline, and ECOG ≤2 performance status. Aza 75 mg/m 2 was administered on Days (d) 1-7 of each 28-d cycle. The Ven RP2D was 400 mg x 14 d of each 28-d cycle. Primary objectives were to assess the Ven+Aza safety profile and to establish the RP2D. Key secondary objectives were to assess the overall response rate (ORR), defined as complete remission (CR), marrow CR and partial remission (PR), and overall survival. Analyses were carried out on all pts who received ≥1 dose of study drug and efficacy was evaluated per IWG 2006 response criteria. Molecular responses were quantified by mutation analysis of baseline and serial BM aspirate (BMA) or peripheral blood (PB) samples collected at protocol-specified time points. Mutations were identified in BMA using Archer VariantPlex Myeloid 75-gene panel [limit of detection (LOD) 5%; time points: pre-treatment (n=43), on-treatment (n=32), and treatment completion visit (TCV) (n=25)] or TruSight Myeloid 54-gene Sequencing Panel in PB [LOD 2%; time points: pre-treatment (n=21), on-treatment (n=19), and TCV (n=8)] to assess molecular dynamics during Ven + Aza treatment. Molecular responses were only compared within the same tissue type. Results: At the Dec 15, 2020 cutoff, 78 pts had received Ven+Aza, including 51 who received Ven at the RP2D of 400 mg x 14 d, with median follow up time of 23 mos (range 0.1-44.2). Median age was 70 years (range 26-87); 72% male; and 91% had excess BM blasts ( & gt;5 to ≤10%, n=21; & gt;10 to ≤20%, n=49; & gt;20%, n=1). For the entire population, mORR was 80% (CR 40% and mCR 40%; no PR). 42% with mCR also had hematologic improvement [HI]. Screening mutational profiling was performed on 46/51 pts who received the RP2D of Ven + Aza. The most common mutations were TP53 (26%), ASXL1 (24%), U2AF1 (17%), and RUNX1 (15%), consistent with a higher-risk MDS population. Clinical responses (CR + mCR) were observed across the mutational spectrum, including in pts with poor prognostic mutations in TP53 (83%), ASXL1 (82%), and RUNX1 (71%). Sixty-four pts treated with Ven + Aza (all Ven dosing cohorts) had paired BMA or PB pre-treatment and on-treatment and/or end of study samples available for serial analysis at the Dec 15, 2020 data cutoff. Ven + Aza resulted in robust and rapid molecular responses across the mutational spectrum. Pts who achieved CR at the time of serial sample acquisition had more significant reduction of variant allele frequencies (VAFs) (n=18 pts, mean VAF pre-treatment = 38.3; mean VAF at CR = 11.8) compared to pts who achieved stable disease or HI (n=11 pts, mean VAF pre-treatment = 29.8; mean VAF at SD or HI = 24.0) or progressive disease (n=10 pts, mean VAF pre-treatment = 27.4; mean VAF at PD = 26.9). Reductions of VAFs below the LOD were observed across the mutational spectrum, including in genes that are considered poor prognostic in higher-risk MDS (e.g., TP53, ASXL1 and RUNX1), demonstrating the broad molecular activity of Ven + Aza (Figure). Finally, molecular responses were observed quickly, with VAF reductions below the LOD observed as early as end of Cycle 1, consistent with the mechanism of action of Ven directly activating the mitochondrial apoptotic pathway in cells. Conclusions: Pts with higher-risk MDS treated with Ven + Aza had rapid, durable responses and high remission rates. Pts across key mutational profiles achieved meaningful clinical and molecular responses, supporting an all-comers approach. Updated data will be presented, which will provide more follow up time and durability of responses among mutational subsets. Figure 1 Figure 1. Disclosures Garcia: Genentech: Research Funding; Takeda: Consultancy, Membership on an entity's Board of Directors or advisory committees; Astellas: Consultancy, Membership on an entity's Board of Directors or advisory committees; AbbVie: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; AstraZeneca: Research Funding; Prelude: Research Funding; Pfizer: Research Funding. Wei: Novartis, Celgene, AbbVie, Servier, AstraZeneca, and Amgen: Research Funding; Novartis, Janssen, Amgen, Roche, Pfizer, Abbvie, Servier, BMS, Macrogenics, Agios, Gilead: Membership on an entity's Board of Directors or advisory committees; Astellas: Honoraria. Jacoby: Abbvie: Research Funding; Jazz: Research Funding. Fong: Amgen, BMS: Speakers Bureau; AbbVie, Amgen, Novartis, Pfizer, Astellas: Honoraria; Amgen: Research Funding. Borate: Jazz Pharma: Research Funding; Blueprint Medicine: Membership on an entity's Board of Directors or advisory committees; Astellas: Membership on an entity's Board of Directors or advisory committees; Pfizer: Membership on an entity's Board of Directors or advisory committees, Research Funding; AbbVie: Membership on an entity's Board of Directors or advisory committees, Research Funding; Genentech: Membership on an entity's Board of Directors or advisory committees, Other: Advisory Board; Novartis: Membership on an entity's Board of Directors or advisory committees, Research Funding; Takeda: Membership on an entity's Board of Directors or advisory committees; Daiichi-Sankyo: Membership on an entity's Board of Directors or advisory committees; incyte: Membership on an entity's Board of Directors or advisory committees, Research Funding; Rampal: Membership on an entity's Board of Directors or advisory committees; Galecto, Inc.: Consultancy; Promedior: Consultancy. Cunningham: AbbVie, Amgen, Astex, Celgene, Janssen, Novartis, Principia Biopharma, Rigel: Research Funding. Odenike: Celgene, Incyte, AstraZeneca, Astex, NS Pharma, AbbVie, Gilead, Janssen, Oncotherapy, Agios, CTI/Baxalta, Aprea: Research Funding; AbbVie, Celgene, Impact Biomedicines, Novartis, Taiho Oncology, Takeda: Consultancy. Jurcic: AbbVie, BMS/Celgene, Novartis: Consultancy; AbbVie, Arog Pharmaceuticals, Astellas, BMS/Celgene, Forma Therapeutics, Genentech, Gilead Sciences, PTC Therapeutics, Syros Pharmaceuticals: Research Funding. Nowak: Pharmaxis: Current holder of individual stocks in a privately-held company, Research Funding; AbbVie: Other: Investigator on funded clinical trial; Affimed: Research Funding; Tolero Pharma, Pharmaxis, Apogenix: Research Funding; Celgene: Honoraria; Takeda: Honoraria. Platzbecker: Janssen: Honoraria; Celgene/BMS: Honoraria; Geron: Honoraria; AbbVie: Honoraria; Novartis: Honoraria; Takeda: Honoraria. Dunshee: Genentech/Roche: Current Employment, Current equity holder in publicly-traded company. Zhou: AbbVie: Current Employment, Current holder of stock options in a privately-held company. Hoffman: AbbVie: Current Employment, Current holder of stock options in a privately-held company. Sun: AbbVie: Current Employment. Popovic: AbbVie: Current Employment, Current equity holder in publicly-traded company. Ainsworth: AbbVie: Current Employment, Current holder of stock options in a privately-held company. Naqvi: Genentech/Roche: Current Employment, Current holder of stock options in a privately-held company. Kye: AbbVie: Current Employment, Other: May hold equity. Hogdal: AbbVie: Current Employment, Current holder of stock options in a privately-held company.

Kurzfassung: Background: Novel strategies are needed to improve upon the 60% cure rate of upfront R-CHOP in advanced DLBCL. Single-agent immune checkpoint inhibition (ICI) has limited efficacy in heavily pre-treated DLBCL (response rate & lt;10%, Ansell JCO 2019), potentially due to residual immunocompromise from prior therapy. Frontline ICI, given when host immunity is relatively intact, may improve these outcomes. Concurrent ICI with R-CHOP is safe (Smith BJH 2020) but corticosteroid-related immunosuppression may negate ICI efficacy. These factors, along with evidence that ICI sensitises non-Hodgkin lymphoma to subsequent chemotherapy (Carreau BJH 2020), support a sequential treatment strategy. Avelumab (Av) is an anti-PDL1 monoclonal antibody with antibody dependent cell cytotoxicity (ADCC) activity which acts synergistically with rituximab (R) in vitro. We report the results of a phase II single arm study assessing safety of 1st line sequential AvR induction, R-CHOP & Av maintenance for DLBCL. Methods: Patients aged ≥18 years, ECOG 0-2 with untreated stage II-IV DLBCL and no active autoimmune disease were treated with AvR induction x2 cycles q2-weekly (Av 10mg/kg IV + R 375mg/m2 IV), followed by R-CHOP21 x 6 cycles then Av 10mg/kg x 6 cycles q2-weekly if in complete metabolic response (CMR) post R-CHOP. The primary endpoint was the rate of grade 3/4 immune-related adverse events (irAE). Secondary endpoints included overall response rate (ORR), failure free survival (FFS), overall survival (OS) and overall toxicity. Response was determined centrally by PET-CT (Lugano 2014 criteria). CMR rates by PET-CT post AvR induction and post C2 R-CHOP were exploratory endpoints. Genomic analysis was performed including next generation sequencing (NGS) based sequence variant detection, copy number analysis and structural variant detection. Results: 28 pts were enrolled from Dec 2017 to Oct 2019. Key baseline characteristics included median age 54 yrs (range 20-79); stage III/IV disease 68%; elevated LDH 61%; IPI ≥2 25%. Histology included 21 DLBCL NOS (75%; 14 GCB, 7 non-GCB by Hans algorithm), 6 primary mediastinal B-cell lymphoma (PMBCL; 21%) and 1 EBV positive DLBCL (4%). The study met its pre-specified primary endpoint of G3/4 irAE & lt;30%. Grade 3/4 irAEs included hepatitis (n=1) and rash (n=2). G1/2 irAEs occurred in 71% (20/28) as follows: rash 53%, liver dysfunction 26%, hyper/hypothyroidism 29% and diarrhoea 21%. 79% had G3/4 toxicity, predominantly haematological, related to RCHOP with febrile neutropenia/infection in 28% of pts. ORR post R-CHOP was 89% (all CR) (Figure 1). The ORR to 2 cycles of induction AvR was 60%, including 6 CMR (21%) across all diagnostic/histologic subgroups (n=1 PMBCL, n=2 non-GCB DLBCL, n=3 GCB DLBCL; Figures 1 and 2). Six pts (21%) progressed during AvR induction (with 1 pt completing only 1 x AvR cycle); all subsequently responded to R-CHOP. With a median follow-up of 16 months, 1-year FFS was 76% and OS 89%. Treatment was discontinued early in 5 pts; 2 during R-CHOP due to progressive disease and 3 during Av maintenance (n=1 immune hepatitis; n=1 pulmonary embolism initially reported as pneumonitis; n=1 progressive disease). Alterations in the CD274/PDCDLG2 locus were identified by NGS in 3 of 27 evaluable pts (n=2 PMBCL, n=1 EBV+ DLBCL). Full genomic analysis to identify factors associated with response will be presented. Conclusion: Sequential AvR induction, R-CHOP and Av maintenance in pts with newly diagnosed DLBCL is feasible with a manageable toxicity profile and a high CR rate. Responses to AvR alone were higher than expected based on the relapsed/refractory population and may suggest superior efficacy of ICI in the frontline setting. These results support ongoing sequential studies of immune priming with PD1/PDL1 inhibition prior to R-CHOP in DLBCL. Acknowledgements: Merck KgA for avelumab plus funding. Tour de Cure Scott Canning Early Career Grant (E Hawkes) and Wilson Centre for Lymphoma Genomics for biomarker testing. Disclosures Hawkes: Astra Zeneca: Membership on an entity's Board of Directors or advisory committees, Research Funding; Gilead: Membership on an entity's Board of Directors or advisory committees; Roche: Membership on an entity's Board of Directors or advisory committees, Other: Travel, Research Funding, Speakers Bureau; BMS celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Janssen-Cilag: Membership on an entity's Board of Directors or advisory committees, Other: Travel, Speakers Bureau; Merck Sharpe & Dohme: Membership on an entity's Board of Directors or advisory committees, Research Funding; takeda: Speakers Bureau; Merck KgA: Research Funding. Chong:Merck Serono: Research Funding; Bristol-Myers Squibb: Research Funding; Hutchison Medipharma: Research Funding; Bayer: Research Funding; Pharmacyclics LLC, an AbbVie Company: Research Funding; Servier: Research Funding; Isofol: Research Funding. Blombery:Novartis: Consultancy; Janssen: Honoraria; Amgen: Consultancy; Invivoscribe: Honoraria. Barraclough:Roche: Other: Conference sponsorship. Keane:Celgene: Honoraria, Other: Travel; BMS: Research Funding; Roche: Honoraria, Other: Travel, Speakers Bureau; MSD Oncology: Honoraria, Other: Travel; Gilead: Honoraria, Other: Travel, Speakers Bureau. Fong:Pfizer: Honoraria; Astellas: Honoraria; Amgen: Honoraria, Research Funding, Speakers Bureau; Novartis: Honoraria; AbbVie: Honoraria. Manos:Bristol-Myers Squibb: Other: Conference sponsorship. OffLabel Disclosure: Avelumab is an anti-PDL1 monoclonal antibody. Inhibition of the PD1/PDL1 pathway stimulates anti-tumour immunity.

Kurzfassung: Abstract 3631 Introduction: Despite improvements in clinical outcome with intensification of induction and consolidation chemotherapy, the majority of patients with AML will ultimately relapse. At first relapse, the European Prognostic Index (EPI) stratifies outcome according to relapse-free interval, karyotype, age and prior allogeneic stem cell transplant (Breems et al, JCO 2005; 1969). Recently, FLT3-ITD has also emerged as a predictor of poor outcome in relapsed patients (Chevallier et al, Leukemia 2011; 939). The purpose of this study was to define predictors of outcome in patients with AML treated at first relapse with FLAG-Amsacrine (Fludarabine 30mg/m2/day days 1–5; Cytarabine 2g/m2/day days 1–5; G-CSF 300mcg/day days 1–6; Amsacrine 100mg/m2/day days 1–3), particularly in the context of FLT3-ITD status and prior high-dose ara-C (HiDAC) exposure. Methods: Patients treated at The Alfred, Box Hill, and Geelong hospitals with FLAG-Amsacrine between 2002 and 2011 were retrospectively identified. Statistical analysis of clinical outcomes related to toxicity, response and survival was performed with SPSS™ and GraphPad Prism™. Results: 56 patients with AML in first relapse (28 male, 28 female), median age 50.5 years (range 18–70), received FLAG-Amsacrine as salvage therapy. The patient characteristics are summarised in Table 1. 48 patients had a history of prior HiDAC-exposure and 11 (19.7%) were known to be FLT3-ITD positive. The median time to neutrophil and platelet recovery in those attaining CR was 28.5 and 32 days respectively. 42-day treatment related mortality was 12.5%. The overall CR/CRi rate after FLAG-Amsacrine was 61% with 27% refractory to treatment. Median EFS (censored at the time of subsequent allograft) and OS from treatment commencement was 6.7 and 10.6 months respectively (median follow up 6.5 months; range 1–55 months). As most patients with AML receive HiDAC at some stage during induction or consolidation, analysis of outcomes according to the EPI score in those with prior HiDAC exposure was performed. A statistically significant difference in OS was not observed between intermediate and poor risk EPI groups (41 vs 42% 1yr OS respectively; p=0.74) (Figure 1). An analysis of each EPI risk determinant showed that a relapse-free interval (RFI) of less than 6 months was the most important factor influencing overall survival (4 vs 17 months, p=0.03). In patients with early relapse (RFI 〈 6 months) treated with FLAG-Amsacrine, survival was dismal, even in those not previously exposed to HiDAC (Figure 2). Adverse risk karyotype (p=0.22), prior allograft (p=0.92) and age 〉 60 (p=0.91) did not negatively impact on OS after FLAG-Amsacrine. There was no significant difference in the CR/CRi rate (60 vs 62.5%, p=1.0), EFS (p=0.33) or OS (p=0.81) of patients who had received FLAG-Amsacrine following prior HiDAC based therapy compared with those who had not received HiDAC. A significant difference in OS was not observed in relation to FLT3-ITD status (p=0.86; Figure 3). 22 patients went on to allogeneic stem cell transplantation with a median time to allograft of 83.5 days (range 29–340 days). Patients who received an allograft had longer median OS (not reached vs 4 months, p=0.01). 16 patients remain in continuous CR, with a median remission duration of 13 months (range 3–45 months). Conclusion: FLAG-Amsacrine is a tolerable and effective salvage regimen for AML in first relapse and represents an effective bridge to transplantation. Alternative investigational approaches should be considered for patients with very short duration of first remission, where outcomes after FLAG-Amsacrine were poor, even in the absence of prior HiDAC-based therapy. Disclosures: No relevant conflicts of interest to declare.