CLI120-001 PHASE1B DOSE ESCALATION STUDY OF RVU120 IN PATIENTS WITH AML OR HIGH RISK MDS SAFETY AND EFFICACY DATA UPDATE

Background: CDK8 and its paralog CDK19 have central roles in maintenance of cancer cell viability and undifferentiated state for a variety of tumor types. (Dannappel et al. 2019;Rzymski et al. 2015;Philip et al. 2018). RVU120 (SEL120), a novel CDK8/CDK19 kinase inhibitor with significant efficacy in preclinical AML models, has shown clinical efficacy in a currently ongoing phase Ib trial in patients with relapsed/refractory (R/R) AML or HR-MDS (NCT04021368). This paper provides update with new available data on disease evaluation from ongoing patients and further enrolment into next cohort level 85 mg. Aims: The primary objective of the study is to determine preliminary safety profile, dose limiting toxicities (DLTs), maximum tolerated dose (MTD) and the recommended phase 2 dose of RVU120 as a single agent. Secondary objectives include PK, antileukemic activity and exploratory PD characterization. Methods: The study comprises at least 7 dose escalating cohorts. The first 3 cohorts followed an accelerated scheme, 1 patient enrolled/cohort from 10 to 50 mg dose levels, from cohort 4 (75 mg) to 7 (100 mg) doses onwards a 3+3 design is followed. Data from each cohort is evaluated by a data review committee (DRC). RVU120 is administered orally every other day, for a total of 7 doses, in a 3-week treatment cycle until disease progression/unacceptable toxicity. Adverse events are graded according to NCI-CTCAE v.5.0. DLTs are assessed at completion of C1. Disease evaluation is performed according to Dohner 2017 and Cheson 2006 response criteria for AML and MDS respectively. PK parameters are calculated by non-compartmental analysis. Pharmacodynamic (PD) activity is assessed by flow cytometry measure of pSTAT5 Ser725 levels, that are highly dependent on the activity of CDK8 and CDK19 in AML/MDS cells. Results: At data cut off of 23rd Feb22, 13 pts have been enrolled, median age 73 years and median 2 previous lines of therapy, ECOG PS 2 in 4 pts, 1 in 7, 0 in 2. No DLTs were observed, all 14 Serious Adverse Events, including 1 COVID19 death and 1 pancreatitis, were not related to study drug (G1 fever, G2 Upper Respiratory Infection, G3: pseudomonas sepsis;urinary tract infection;febrile neutropenia;lung infection, pain, hemoptysis, pleural effusion, G5 pneumonitis, death NOS, pancreatitis). Cohort 1 pt, 10 mg dose level, and cohort 2 pt, 25 mg, showed stable (SD) and progressive disease (PD) respectively at the end of C1. Cohort 3 pt, an 81 YO male HR-MDS, escalated from 50 to 75 mg dose from C7, is SD at C24D13 with Erythroid Hematological Improvement on C5, C7, C10, C18. Cohort 4, 75 mg dose pt, a 62 YO male with AML DNMT3A pos, relapsing after Ven/Dec, achieved CRi at the end of C1 and CR in C7, and progressed at the end of C8. Two out of the remaining 4 pts treated at 75 mg reached SD (1 still ongoing at C3D15 and another died on C3D20 while on SD), 1 pt died of COVID-19 pneumonitis on C1D18, 1 pt with AML secondary to MPN was SD at C2 and progressed on C4. Two pt were treated at 110 mg (cohort 5), 1 not evaluable died for pancreatitis and 1 was SD at the end of C1. 2 pt entered cohort 6, 85 mg, and will be evaluable at the end of March 2022. Summary/Conclusion: Preliminary results from the first 6 cohorts have shown a favorable safety and a predictable PK profile of RVU120. Meaningful PD activity and clinical efficacy were observed at 50 and 75 mg doses. Enrollment is currently ongoing at 85 mg cohort.

Inhibition of De Novo Pyrimidine Synthesis Depletes Acute Myleogenous Leukemia Stem Cells (LSCs) Burden and Triggers Apoptosis and Differentiation Associated with Oxidative Stress

Background: De novo nucleotide synthesis is necessary to meet the enormous demand for nucleotides, other macromolecules associated with acute myeloid leukemia (AML) progression 1, 2, 34. Hence, we hypothesized that targeting de novo nucleotide synthesis would lead to the depletion of the nucleotide pool, pyrimidine starvation and increase oxidative stress preferentially in leukemic cells compared to their non-malignant counterparts, impacting proliferative and differentiation pathways. Emvododstat (PTC299) is an inhibitor of dihydroorotate dehydrogenase (DHODH), a rate-limiting enzyme for de novo pyrimidine nucleotide synthesis that is currently in a clinical trial for the treatment of AML. Objectives: The goals of these studies were to understand the emvododstat-mediated effects on leukemia growth, differentiation and impact on Leukemia Stem Cells(LSCs). Comprehensive analyses of mitochondrial function, metabolic signaling in PI3K/AKT pathways, apoptotic signatures, and DNA damage responses were carried out. The rationale for clinical testing emvododstat was confirmed in an AML-PDX model. Results: Emvododstat treatment in cytarabine-resistant AML cells and primary AML blasts induced apoptosis, differentiation, and reduced proliferation, with corresponding decreased in cell number and increases in annexin V- and CD14-positive cells. Indeed, the inhibition of de novo nucleotide synthesis compromises the dynamic metabolic landscape and mitochondrial function, as indicated by alterations in the oxygen consumption rate (OCR) and mitochondrial ROS/membrane potential and corresponding differentiation, apoptosis, and/or inhibition of proliferation of LSCs. These effects can be reversed by the addition of exogenous uridine and orotate. Further immunoblotting and mass cytometry (CyTOF) analyses demonstrated changes in apoptotic and cell signaling proteins (cleaved PARP, cleaved caspase-3) and DNA damage responses (TP53, γH2AX) and PI3/AKT pathway downregulation in response to emvododstat. Importantly, emvododstat treatment reduced leukemic cell burden in a mouse model of AML PDX ( Complex karyotype, mutation in ASXL1, IDH2, NRAS), decreased levels of leukemia stem cells frequency (1 in 522,460 Vs 1 in 3,623,599 in vehicle vs emvododstat treated mice), and improved survival. The median survival 40 days vs. 30 days, P=0.0002 in primary transplantation and 36 days vs 53.5 days, P=0.005 in secondary transpantation in a PDX mouse model of human AML. This corresponded with a reduction in the bone marrow burden of leukemia and increased expression of differentiation markers in mice treated with emvododstat (Fig. 1). These data demonstrate effect of emvododstat on mitochondrial functions. Conclusion: Inhibition of de novo pyrimidine synthesis triggers differentiation, apoptosis, and depletes LSCs in AML models. Emvododstat is a novel dihydroorotate dehydrogenase inhibitor being tested in a clinical trial for the treatment of myeloid malignancies and COVID-19. Keywords: AML, emvododstat, DHODH, apoptosis, differentiation References: 1 Thomas, D. & Majeti, R. Biology and relevance of human acute myeloid leukemia stem cells. Blood 129, 1577-1585, doi:10.1182/blood-2016-10-696054 (2017). 2 Quek, L. et al. Genetically distinct leukemic stem cells in human CD34- acute myeloid leukemia are arrested at a hemopoietic precursor-like stage. The Journal of experimental medicine 213, 1513-1535, doi:10.1084/jem.20151775 (2016). 3 Villa, E., Ali, E. S., Sahu, U. & Ben-Sahra, I. Cancer Cells Tune the Signaling Pathways to Empower de Novo Synthesis of Nucleotides. Cancers (Basel) 11, doi:10.3390/cancers11050688 (2019). 4 DeBerardinis, R. J. & Chandel, N. S. Fundamentals of cancer metabolism. Sci Adv 2, e1600200, doi:10.1126/sciadv.1600200 (2016). [Formula presented] Disclosures: Weetall: PTC therapeutics: Current Employment. Sheedy: PTC therapeutics: Current Employment. Ray: PTC therapeutics: Current Employment. Andreeff: Karyopharm: Research Funding;AstraZeneca: Research Funding;Oxford Biomedica UK: Research Funding;Aptose: Consultancy;Daiich -Sankyo: Consultancy, Research Funding;Syndax: Consultancy;Breast Cancer Research Foundation: Research Funding;Reata, Aptose, Eutropics, SentiBio;Chimerix, Oncolyze: Current holder of individual stocks in a privately-held company;Novartis, Cancer UK;Leukemia & Lymphoma Society (LLS), German Research Council;NCI-RDCRN (Rare Disease Clin Network), CLL Foundation;Novartis: Membership on an entity's Board of Directors or advisory committees;Senti-Bio: Consultancy;Medicxi: Consultancy;ONO Pharmaceuticals: Research Funding;Amgen: Research Funding;Glycomimetics: Consultancy. Borthakur: ArgenX: Membership on an entity's Board of Directors or advisory committees;Protagonist: Consultancy;Astex: Research Funding;University of Texas MD Anderson Cancer Center: Current Employment;Ryvu: Research Funding;Takeda: Membership on an entity's Board of Directors or advisory committees;Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees;GSK: Consultancy.

Safety and Efficacy of Cusatuzumab in Combination with Venetoclax and Azacitidine (CVA) in Patients with Previously Untreated Acute Myeloid Leukemia (AML) Who Are Not Eligible for Intensive Chemotherapy;An Open-Label, Multicenter, Phase 1b Study

Background: Acute myeloid leukemia (AML) is driven by aberrant leukemic stem cells (LSCs) that initiate and sustain malignancy. To circumvent resistance to therapy, combination therapies with additive mechanisms of action are needed. CD70, a tumor necrosis factor receptor ligand, and its receptor CD27 are expressed on LSCs and AML blasts, but not on hematopoietic stem cells. Cusatuzumab, a high-affinity humanized monoclonal anti-CD70 antibody, kills CD70-expressing cells by Fc domain-mediated effector functions and is a potent inhibitor of CD70-CD27 signaling. Here we report initial results of a study of cusatuzumab in combination with the current standard of care therapy, venetoclax plus azacitidine (CVA), in patients with untreated AML (de novo or secondary) ineligible for intensive chemotherapy due to age ≥75 years or medical comorbidities. Methods: The primary objective of this open label, multicenter, phase 1b study was to assess safety and tolerability of CVA. Key secondary objectives included response rate per ELN 2017 criteria and time to response. Patients received cusatuzumab 10 or 20 mg/kg IV on Day 3 and Day 17, a 3-day ramp-up of venetoclax (100, 200, and 400 mg PO) followed by 400 mg daily dosing, and azacitidine 75 mg/m 2 SC or IV on Days 1-7 of each 28-day cycle. Results: Based on data through Jul 9, 2021, 44 patients enrolled with median age 75 years (range 32-89), 36.4% had secondary AML, 40.9% had an ECOG performance status of 2, and ELN risk was favorable, intermediate and adverse in 18.2%, 20.5% and 61.4%, respectively. All patients received 20 mg/kg cusatuzumab except for 3 patients who received a starting dose of 10 mg/kg with the option to escalate to 20 mg/kg. Of these 3 patients, 1 escalated to 20 mg/kg. At a median follow-up of 29.1 weeks, the median number of treatment cycles was 4.0 (range 1.0-11.0). Grade 3 or above TEAEs were reported in 97.7% of patients;the most common (reported in ≥10%) were neutropenia (68.2%), thrombocytopenia (65.9%), febrile neutropenia (36.4%), anemia (34.1%), leukopenia (29.5%), sepsis (27.3%), and lymphopenia (15.9%). Treatment-emergent serious adverse events (SAEs) were reported in 75% of patients;the most common (reported in at least ≥5%) were febrile neutropenia (27.3%), sepsis (22.7%), COVID-19 (6.8%), and thrombocytopenia (6.8%). Treatment-emergent SAEs of grade ≥3 were reported in 72.7% of the patients. Infusion-related reactions (IRRs) were reported for 11.4% of patients with 2.3% at grade ≥3. Six (13.6%) patients discontinued treatment due to AEs, and 5 (11.4%) TEAEs resulted in death. The mortality rate within 30 days from start of treatment was 4.5%. Table 1 summarizes best response to study treatment. In the intent-to-treat analysis set (n=44) complete remission (CR) rate was 45.5%, while CR + CR with partial hematologic recovery (CRh) + CR with incomplete hematologic recovery (CRi) was 77.3%;MLFS was observed in 11.4% of patients. Of 34 responders (defined as CR, CRi or CRh), 47% were MRD negative by flow cytometry at or after achievement of response. Median time to first response for patients who achieved CR, CRh or CRi was 4.21 (3.0-25.0) weeks. Best response rates in the post-hoc response evaluable analysis set (n=42) that excluded two patients who died before the first disease evaluation were: CR in 47.6%, CR + CRh + CRi in 81.0% and MLFS in 11.9% of patients (Table 1). The majority (97.1%) of responders experienced at least one cycle delay in administration of CVA post response. Conclusions: Cusatuzumab administered in combination with venetoclax and azacitidine to elderly patients with untreated AML was generally well tolerated and demonstrated a safety profile consistent with that previously reported with venetoclax-azacitidine, with the addition of generally manageable IRRs. Response rates support an additive effect of cusatuzumab to the standard of care with potential for improved clinical outcomes. However, further clinical trials are needed for validation of these initial results. HK and GB contributed equally to this publ cation. [Formula presented] Disclosures: Roboz: AstraZeneca: Consultancy;Janssen: Research Funding;Bristol Myers Squibb: Consultancy;Jasper Therapeutics: Consultancy;Agios: Consultancy;Novartis: Consultancy;Amgen: Consultancy;Blueprint Medicines: Consultancy;Janssen: Consultancy;Helsinn: Consultancy;Daiichi Sankyo: Consultancy;Glaxo SmithKline: Consultancy;Celgene: Consultancy;Jazz: Consultancy;MEI Pharma - IDMC Chair: Consultancy;Mesoblast: Consultancy;Actinium: Consultancy;AbbVie: Consultancy;Astex: Consultancy;Bayer: Consultancy;Astellas: Consultancy;Roche/Genentech: Consultancy;Pfizer: Consultancy;Otsuka: Consultancy. Aribi: Seagen: Consultancy. Brandwein: Astellas: Honoraria;Jazz: Honoraria;Amgen: Honoraria;Taiho: Honoraria;BMS/Celgene: Honoraria;Pfizer: Honoraria;Abbvie: Honoraria;University of Alberta: Current Employment. Döhner: Astellas: Consultancy, Honoraria, Research Funding;AstraZeneca: Consultancy, Honoraria;Berlin-Chemie: Consultancy, Honoraria;Amgen: Consultancy, Honoraria, Research Funding;Abbvie: Consultancy, Honoraria, Research Funding;Agios: Consultancy, Honoraria, Research Funding;Celgene: Consultancy, Honoraria, Research Funding;GEMoaB: Consultancy, Honoraria;Helsinn: Consultancy, Honoraria;Janssen: Consultancy, Honoraria;Jazz: Consultancy, Honoraria, Research Funding;Novartis: Consultancy, Honoraria, Research Funding;Oxford Biomedicals: Consultancy, Honoraria;Pfizer: Research Funding;Roche: Consultancy, Honoraria;Gilead: Consultancy, Honoraria;Bristol Myers Squibb: Consultancy, Honoraria, Research Funding;Astex: Consultancy, Honoraria;Ulm University Hospital: Current Employment. Fiedler: Jazz Pharmaceuticals: Consultancy, Other: support for meeting attendance;Abbvie: Consultancy, Honoraria;Morphosys: Consultancy;Celgene: Consultancy;Pfizer: Consultancy, Research Funding;Novartis: Consultancy;ARIAD/Incyte: Consultancy;Amgen: Consultancy, Other: support for meeting attendance, Patents & Royalties, Research Funding;Servier: Consultancy, Other: support for meeting attendance;Daiichi Sankyo: Consultancy, Other: support for meeting attendance;Stemline: Consultancy. Gandini: argenx: Current Employment, Current equity holder in publicly-traded company, Divested equity in a private or publicly-traded company in the past 24 months. Geddes: University of Calgary: Current Employment;Taiho: Consultancy, Membership on an entity's Board of Directors or advisory committees;Jazz: Consultancy, Membership on an entity's Board of Directors or advisory committees;Pfizer: Consultancy, Membership on an entity's Board of Directors or advisory committees;Novartis: Consultancy;BMS: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau;Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees;Amgen: Consultancy;Paladin: Consultancy;Janssen: Research Funding;Geron: Research Funding;Abbvie: Membership on an entity's Board of Directors or advisory committees, Research Funding. Hou: University of Pittsburgh Medical Center Hillman Cancer Centers: Current Employment;AbbVie: Honoraria;AstraZeneca: Honoraria;Karyopharm: Honoraria;Chinese American Hematology Oncology Network: Membership on an entity's Board of Directors or advisory committees. Howes: Janssen R&D, part of Johnson & Johnson: Current Employment;Johnson & Johnson: Current holder of individual stocks in a privately-held company, Current holder of stock options in a privately-held company. Hultberg: argenx: Current Employment, Patents & Royalties. Huselton: University of Rochester: Current Employment. Jacobs: Argenx BV: Current Employment, Current equity holder in publicly-traded company;University of Antwerp: Ended employment in the past 24 months. Kane: Janssen R&D, part of Johnson & Johnson: Current Employment, Current equity holder in publicly-traded company. Lech-Marańda: Takeda: Membership on an entity's Board of Directors or advisory committees;AbbVie: Membership on an entity's Board of Directors r advisory committees;Novartis: Membership on an entity's Board of Directors or advisory committees;Roche: Membership on an entity's Board of Directors or advisory committees;Janssen-Cilag: 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;Gilead: Membership on an entity's Board of Directors or advisory committees, Research Funding. Louwers: argenx: Current Employment, Patents & Royalties: Patents (no royalties). Nottage: Janssen R&D, part of Johnson & Johnson: Current Employment;Johnson & Johnson: Current holder of individual stocks in a privately-held company, Current holder of stock options in a privately-held company. Platzbecker: Novartis: Honoraria;AbbVie: Honoraria;Janssen: Honoraria;Celgene/BMS: Honoraria;Geron: Honoraria;Takeda: Honoraria. Rampal: Pharmaessentia: Consultancy;BMS/Celgene: Consultancy;Abbvie: Consultancy;Sierra Oncology: Consultancy;Incyte: Consultancy, Research Funding;Blueprint: Consultancy;Disc Medicine: Consultancy;Jazz Pharmaceuticals: Consultancy;Constellation: Research Funding;Kartos: Consultancy;Stemline: Consultancy, Research Funding;CTI: Consultancy;Novartis: Consultancy;Memorial Sloan Kettering: Current Employment. Salman: Janssen: Current Employment, Current holder of individual stocks in a privately-held company, Current holder of stock options in a privately-held company. Shah: Janssen R&D, part of Johnson & Johnson: Current Employment. Stuart: Clinical Drug Development Consultants LLC: Current Employment;Argenx: Consultancy;Cleave Therapeutics: Consultancy;Triphase Accelerator Corp: Consultancy;IgM Biosciences: Consultancy;Revolution Medicines: Consultancy;Jiya Corp:Consultancy;Geron Corp: Current holder of individual stocks in a privately-held company. Subklewe: Janssen: Consultancy;Pfizer: Consultancy, Speakers Bureau;Takeda: Speakers Bureau;Klinikum der Universität München: Current Employment;MorphoSys: Research Funding;Novartis: Consultancy, Research Funding, Speakers Bureau;Roche: Research Funding;Seattle Genetics: Consultancy, Research Funding;Miltenyi: Research Funding;Gilead: Consultancy, Research Funding, Speakers Bureau;Amgen: Consultancy, Research Funding, Speakers Bureau;BMS/Celgene: Consultancy, Research Funding, Speakers Bureau. Sumbul: argenx: Current Employment. Wang: Takeda: Consultancy, Honoraria, Other: Advisory board;Jazz Pharmaceuticals: Consultancy, Honoraria, Other: Advisory Board;Astellas: Consultancy, Membership on an entity's Board of Directors or advisory committees;Stemline Therapeutics: Consultancy, Honoraria, Other: Advisory board, Speakers Bureau;AbbVie: Consultancy, Membership on an entity's Board of Directors or advisory committees;Kite Pharmaceuticals: Consultancy, Honoraria, Other: Advisory Board;GlaxoSmithKline: Consultancy, Honoraria, Other: Advisory Board;Genentech: Membership on an entity's Board of Directors or advisory committees;BMS/Celgene: Membership on an entity's Board of Directors or advisory committees;DAVA Oncology: Consultancy, Speakers Bureau;Kura Oncology: Consultancy, Honoraria, Other: Advisory board, steering committee, Speakers Bureau;Novartis: Consultancy, Honoraria, Other: Advisory Board;Mana Therapeutics: Consultancy, Honoraria;Pfizer: Consultancy, Honoraria, Other: Advisory Board, Speakers Bureau;Rafael Pharmaceuticals: Other: Data safety monitoring committee;Gilead: Consultancy, Honoraria, Other: Advisory board;Daiichi Sankyo: Consultancy, Honoraria, Other: Advisory board;PTC Therapeutics: Consultancy, Honoraria, Other: Advisory board;Genentech: Consultancy;MacroGenics: Consultancy. Wierzbowska: Jazz: Research Funding;Pfizer: Honoraria;Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees;Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees;Astellas: Honoraria, Membership on an entity's Board of Directors or advisory comm ttees;Abbvie: Honoraria, Membership on an entity's Board of Directors or advisory committees;BMS: Honoraria. Yao: Statagize LLC: Current Employment;Puma Biotechnology, Inc.: Ended employment in the past 24 months;Argenx: Consultancy. Yee: Astex: Membership on an entity's Board of Directors or advisory committees, Research Funding;Janssen: Research Funding;TaiHo: Membership on an entity's Board of Directors or advisory committees;Otsuka: Membership on an entity's Board of Directors or advisory committees;Onconova: Research Funding;Pfizer: Membership on an entity's Board of Directors or advisory committees;Tolero: Research Funding;Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding;Paladin: Membership on an entity's Board of Directors or advisory committees;MedImmune: Research Funding;AbbVie: Honoraria;Bristol-Myers Squibb/Celgene: Membership on an entity's Board of Directors or advisory committees;Shattuck Labs: Membership on an entity's Board of Directors or advisory committees;Forma Therapeutics: Research Funding;Takeda: Membership on an entity's Board of Directors or advisory committees;Geron: Research Funding;Genentech: Research Funding;F. Hoffmann La Roche: Membership on an entity's Board of Directors or advisory committees, Research Funding;Jazz: Research Funding. Kantarjian: Immunogen: Research Funding;Astra Zeneca: Honoraria;KAHR Medical Ltd: Honoraria;Astellas Health: Honoraria;Pfizer: Honoraria, Research Funding;NOVA Research: Honoraria;Ascentage: Research Funding;Precision Biosciences: Honoraria;Novartis: Honoraria, Research Funding;Aptitude Health: Honoraria;Ipsen Pharmaceuticals: Honoraria;Jazz: Research Funding;Daiichi-Sankyo: Research Funding;BMS: Research Funding;Amgen: Honoraria, Research Funding;AbbVie: Honoraria, Research Funding;Taiho Pharmaceutical Canada: Honoraria. Borthakur: Protagonist: Consultancy;Ryvu: Research Funding;Astex: Research Funding;GSK: Consultancy;Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees;Takeda: Membership on an entity's Board of Directors or advisory committees;University of Texas MD Anderson Cancer Center: Current Employment;ArgenX: Membership on an entity's Board of Directors or advisory committees.

Combined Ibrutinib and Venetoclax for First-Line Treatment of Patients with Chronic Lymphocytic Leukemia (CLL): Focus on Long-Term MRD Results

Background: Ibrutinib (IBR) and venetoclax (VEN) combination is a highly effective therapy for patients (pts) with CLL (Jain, NEJM 2019;Wierda, ASH 2020;Kater, EHA 2021). We previously reported results of the first-line cohort of a phase II trial of combined IBR and VEN for high-risk pts with CLL (Jain, NEJM 2019;Jain, JAMA Oncology 2021). Here we report updated data for these pts with focus on MRD. Methods: Pts with previously untreated CLL meeting IWCLL treatment criteria were enrolled. All pts had at least one high-risk feature: del(17p), mutated TP53, del(11q), unmutated IGHV, or age ≥65 years (yrs). Pts received IBR 420 mg daily for 3 cycles followed by addition of VEN (weekly dose-escalation to 400mg daily). Combined therapy was given for 24 cycles (28 days/cycle). Pts with bone marrow (BM) undetectable MRD (U-MRD) (flow cytometry;sensitivity 10 -4) at 24 cycles of combined therapy discontinued both VEN and IBR;MRD+ pts continued IBR. A trial amendment allowed an additional 12 cycles of combined VEN and ibrutinib for pts who remained BM MRD+ after Cycle 24. Response assessments were performed using BM and CT imaging studies (2008 IWCLL criteria). U-MRD was defined as <0.01%;low MRD+ 0.01% to <1%;high MRD+ ≥1%. Progression-free survival (PFS) was assessed as the time from the start of study drug to CLL progression, Richter transformation, or death from any cause. Blood MRD was monitored every 6 months in pts off treatment or on ibrutinib monotherapy beyond 24 cycles of combined treatment. Results: A total of 80 pts were enrolled. Baseline characteristics are shown in Table 1. The median follow-up was 44.1 months. Five pts came off study during 1 st 3 cycles of IBR monotherapy;75 pts initiated VEN. We previously reported that after 12 cycles of the combination, 45/80 (56%) achieved BM U-MRD remission;24/80 (30%) were BM MRD-positive (low MRD+, n=19;high MRD+, n=5). After 24 cycles of the combination, 53/80 (66%) achieved BM U-MRD remission;14/80 (17%) were BM MRD+ (low MRD+, n=13;high MRD+, n=1). Overall, 60/80 (75%) achieved BM U-MRD as the best response. Updated PFS is provided in Figure 1. Of the 53 pts who were BM U-MRD at the end of cycle 24 of the combination, 52 pts had a subsequent blood MRD assessment done in follow-up (1 missed due to COVID-19);51/53 discontinued all therapy, 2 pts continued IBR per treatment physician discretion. With a median time of 18.4 months post Cycle 24, 8 pts had recurrence of blood MRD (defined as MRD ≥ 0.01% in 2 consecutive visits) in follow-up with 1 pt with CLL progression. The sole pt with CLL progression had mutated IGHV with del(11q) and NOTCH1 mutation. The pt had delayed achievement of BM U-MRD with the pt achieving U-MRD for the first time at the end of Cycle 24 of combined therapy. She was noted to have disease progression 22 months off therapy;BTK or PLCG2 mutation were not detected and the patient is currently in clinical remission on acalabrutinib. The time to MRD conversion for these 53 pts is shown in Figure 2. There were 14 pts who were BM MRD+ at the end of cycle 24 of the combination (low MRD+, n=13;high MRD+, n=1). The only pt with high-MRD+ at end of cycle 24 was noted to have Richter transformation at that time. The remaining 13 pts (all low MRD+ in BM, range 0.01-0.56%) continued IBR monotherapy. With a recent trial amendment, MRD+ pts after Cycle 24 could get 12 additional cycles of venetoclax;9/13 pts have resumed VEN. 6/9 pts have achieved U-MRD remission. 2 pts had Richter transformation and 3 pts have died (Jain, JAMA Oncology 2021). Conclusions: We report long term follow-up of combined IBR and VEN in first-line CLL. Remissions were durable with some pts having recurrence of blood MRD in follow-up, which may be an early indicator of relapse. In a small subset of the pts with BM MRD+ disease at 24 cycles of combined therapy, additional VEN appears to lead to U-MRD remission in majority of the pts. Whether this will lead to improved long-term PFS remains to be determined. [Formula presented] Disclosures: Jain: TG Therapeutics: Honoraria;Beigene: Honoraria;Janssen: Honoraria;Fate Therapeutics: Research Funding;Aprea Therapeutics: Research Funding;Precision Biosciences: Honoraria, Research Funding;Incyte: Research Funding;Adaptive Biotechnologies: Honoraria, Research Funding;Cellectis: Honoraria, Research Funding;ADC Therapeutics: Honoraria, Research Funding;Servier: Honoraria, Research Funding;Pfizer: Research Funding;Bristol Myers Squibb: Honoraria, Research Funding;AstraZeneca: Honoraria, Research Funding;Genentech: Honoraria, Research Funding;AbbVie: Honoraria, Research Funding;Pharmacyclics: Research Funding. Thompson: AbbVie: Other: Institution: Advisory/Consultancy, Honoraria, Research Grant/Funding;Amgen: Other: Institution: Honoraria, Research Grant/Funding;Genentech: Other: Institution: Advisory/Consultancy, Honoraria, Research Grant/Funding;Adaptive Biotechnologies: Other: Institution: Advisory/Consultancy, Honoraria, Research Grant/Funding, Expert Testimony;Pharmacyclics: Other: Institution: Advisory/Consultancy, Honoraria, Research Grant/Funding;Janssen: Consultancy, Honoraria;Gilead: Other: Institution: Advisory/Consultancy, Honoraria. Ferrajoli: BeiGene: Other: Advisory Board, Research Funding;Janssen: Other: Advisory Board;AstraZeneca: Other: Advisory Board, Research Funding. Burger: Novartis: Other: Travel/Accommodations/Expenses, Speakers Bureau;TG Therapeutics: Other: Travel/Accommodations/Expenses, Research Funding, Speakers Bureau;Janssen: Consultancy, Other: Travel/Accommodations/Expenses, Speakers Bureau;Beigene: Research Funding, Speakers Bureau;Pharmacyclics LLC: Consultancy, Other: Travel/Accommodations/Expenses, Research Funding, Speakers Bureau;Gilead: Consultancy, Other: Travel/Accommodations/Expenses, Research Funding, Speakers Bureau;AstraZeneca: Consultancy. Borthakur: GSK: Consultancy;ArgenX: Membership on an entity's Board of Directors or advisory committees;University of Texas MD Anderson Cancer Center: Current Employment;Protagonist: Consultancy;Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees;Astex: Research Funding;Ryvu: Research Funding;Takeda: Membership on an entity's Board of Directors or advisory committees. Takahashi: Symbio Pharmaceuticals: Consultancy, Membership on an entity's Board of Directors or advisory committees;Novartis: Consultancy;Celgene/BMS: Consultancy;GSK: Consultancy. Sasaki: Daiichi-Sankyo: Membership on an entity's Board of Directors or advisory committees;Pfizer: Membership on an entity's Board of Directors or advisory committees;Novartis: Consultancy, Research Funding. Kadia: Cellonkos: Other;Aglos: Consultancy;Dalichi Sankyo: Consultancy;AbbVie: Consultancy, Other: Grant/research support;BMS: Other: Grant/research support;Amgen: Other: Grant/research support;Cure: Speakers Bureau;Jazz: Consultancy;Genentech: Consultancy, Other: Grant/research support;Liberum: Consultancy;Novartis: Consultancy;Pfizer: Consultancy, Other;Pulmotech: Other;Sanofi-Aventis: Consultancy;AstraZeneca: Other;Astellas: Other;Genfleet: Other;Ascentage: Other. Konopleva: Sanofi: Other: grant support, Research Funding;Cellectis: Other: grant support;Calithera: Other: grant support, Research Funding;KisoJi: Research Funding;Agios: Other: grant support, Research Funding;Ascentage: Other: grant support, Research Funding;AbbVie: Consultancy, Honoraria, Other: Grant Support, Research Funding;Ablynx: Other: grant support, Research Funding;Stemline Therapeutics: Research Funding;Eli Lilly: Patents & Royalties: intellectual property rights, Research Funding;AstraZeneca: Other: grant support, Research Funding;Rafael Pharmaceuticals: Other: grant support, Research Funding;Genentech: Consultancy, Honoraria, Other: grant support, Research Funding;F. Hoffmann-La Roche: Consultancy, Honoraria, Other: grant support;Forty Seven: Other: grant support, Research Funding;Novartis: Other: research funding pending, Patents & Royalties: intellectual property rights;Reata Pharmaceuticals: Current holder of stock options in a privately-held company, Patents & Royalties: intellectual property rights. Alvarado: BerGenBio: Research Funding;Jazz Pharmaceuticals: Research Funding;Astex Pharmaceuticals: Research Funding;Sun Pharma: Consultancy, Research Funding;MEI Pharma: Research Funding;FibroGen: Research Funding;Daiichi-Sankyo: Research Funding;CytomX Therapeutics: Consultancy. Yilmaz: Pfizer: Research Funding;Daiichi-Sankyo: Research Funding. DiNardo: Notable Labs: Current holder of stock options in a privately-held company, Membership on an entity's Board of Directors or advisory committees;Novartis: Honoraria;Takeda: Honoraria;Celgene, a Bristol Myers Squibb company: Honoraria, Research Funding;Forma: Honoraria, Research Funding;AbbVie: Consultancy, Research Funding;GlaxoSmithKline: Membership on an entity's Board of Directors or advisory committees;Bristol Myers Squibb: Honoraria, Research Funding;ImmuneOnc: Honoraria, Research Funding;Agios/Servier: Consultancy, Honoraria, Research Funding;Foghorn: Honoraria, Research Funding. Bose: Kartos Therapeutics: Honoraria, Research Funding;Sierra Oncology: Honoraria;Novartis: Honoraria;Constellation Pharmaceuticals: Research Funding;NS Pharma: Research Funding;Celgene Corporation: Honoraria, Research Funding;Blueprint Medicines: Honoraria, Research Funding;Pfizer: Research Funding;Promedior: Research Funding;Astellas: Research Funding;Incyte Corporation: Honoraria, Research Funding;BMS: Honoraria, Research Funding;CTI BioPharma: Honoraria, Research Funding. Pemmaraju: Blueprint Medicines: Consultancy;LFB Biotechnologies: Consultancy;Novartis Pharmaceuticals: Consultancy, Other: Research Support, Research Funding;ASCO Leukemia Advisory Panel: Membership on an entity's Board of Directors or advisory committees;Dan's House of Hope: Membership on an entity's Board of Directors or advisorycommittees;Roche Diagnostics: Consultancy;MustangBio: Consultancy, Other;Affymetrix: Consultancy, Research Funding;Samus: Other, Research Funding;ImmunoGen, Inc: Consultancy;ASH Communications Committee: Membership on an entity's Board of Directors or advisory committees;Aptitude Health: Consultancy;Plexxicon: Other, Research Funding;Springer Science + Business Media: Other;Protagonist Therapeutics, Inc.: Consultancy;HemOnc Times/Oncology Times: Membership on an entity's Board of Directors or advisory committees;Clearview Healthcare Partners: Consultancy;Abbvie Pharmaceuticals: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other, Research Funding;CareDx, Inc.: Consultancy;Sager Strong Foundation: Other;Daiichi Sankyo, Inc.: Other, Research Funding;Incyte: Consultancy;Stemline Therapeutics, Inc.: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other, Research Funding;Bristol-Myers Squibb Co.: Consultancy;DAVA Oncology: Consultancy;Pacylex Pharmaceuticals: Consultancy;Celgene Corporation: Consultancy;Cellectis S.A. ADR: Other, Research Funding. Jabbour: Amgen, AbbVie, Spectrum, BMS, Takeda, Pfizer, Adaptive, Genentech: Research Funding. Wang: Stemline Therapeutics: Honoraria. Kantarjian: Taiho Pharmaceutical Canada: Honoraria;Precision Biosciences: Honoraria;Immunogen: Research Funding;Daiichi-Sankyo: Research Funding;Jazz: Research Funding;BMS: Research Funding;AbbVie: Honoraria, Research Funding;Pfizer: Honoraria, Research Funding;Novartis: Honoraria, Research Funding;NOVA Research: Honoraria;KAHR Medical Ltd: Honoraria;Ipsen Pharmaceuticals: Honoraria;Astra Zeneca: Honoraria;Astellas Health: Honoraria;Aptitude Health: Honoraria;Amgen: Honoraria, Research Funding;Ascentage: Research Funding. Wierda: Juno Therapeutics: Research Funding;AstraZeneca: Research Funding;Xencor: Research Funding;Janssen: Research Funding;Loxo Oncology, Inc.: Research Funding;Cyclacel: Research Funding;Oncternal Therapeutics, Inc.: Research Funding;Miragen: Research Funding;KITE Pharma: Research Funding;Sunesis: Research Funding;Gilead Sciences: Research Funding;Acerta Pharma Inc.: Rese rch Funding;Pharmacyclics LLC, an AbbVie Company: Research Funding;Karyopharm: Research Funding;Genentech: Research Funding;GSK/Novartis: Research Funding;Genzyme Corporation: Consultancy;AbbVie: Research Funding. OffLabel Disclosure: The combination of ibrutinib and venetoclax is not FDA approved

Phase II study of the IDH2- inhibitor enasidenib in patients with high-risk IDH2-mutated myelodysplastic syndromes (MDS)

Background: Isocitrate dehydrogenase 2 (IDH2) mutations occur in 5% of patients (pts) with MDS. Enasidenib (ENA) is a selective oral inhibitor of the mutant IDH2 enzyme with single-agent activity in relapsed/refractory acute myeloid leukemia (AML). We report the results of the open label phase II study designed to evaluate the efficacy and tolerability of ENA, as monotherapy or in combination with azacitidine (AZA) in pts with higher-risk IDH2-mutated MDS (NCT03383575). Methods: Pts with higher-risk [Revised International Prognostic Scoring System risk > 3 or high molecular risk (HMR)] MDS/CMML or LB AML naïve to hypomethylating agents (HMA) received ENA100 mg orally daily for 28 d of each 28-d cycle + AZA 75 mg/m2 IV or SC on d 1-7 of each cycle (ENA+AZA), and pts with refractory or progressive MDS to prior HMA therapy received ENA alone (ENA), in 28-d cycles until unacceptable toxicity, relapse, transformation to AML, or progression. The primary endpoint was overall response rate (ORR) [complete remission (CR), marrow CR (mCR), partial remission (PR) and hematologic improvement (HI)]. Other endpoints include safety, and survival outcomes. Results: 48 pts received ENA+AZA (n = 26) or ENA (n = 22). The median age was 73 yrs (range, 46-83). Most pts (72%) had HMR: ASXL1 (39%), and RUNX1 (17%). Median number Tx cycles was 4 (2-32) in the ENA+AZA, and 7 (1-23) in the ENA arm. Common Tx-related grade 3-4 AEs in the ENA+AZA arm were neutropenia (64%), thrombocytopenia (28%), and anemia (8%);these occurred in 10%, 0%, and 5%, in the ENA arm. Grade 3-4 infections occurred in 32% (ENA+AZA) and 14% (ENA). IDH differentiation syndrome occurred in 3 pts (12%) in the ENA+AZA and 5 pts (24%) in the ENA arm. Two deaths occurred during the initial 60 d, both unrelated to study and due to COVID. In response-evaluable pts (n=46), ORR was 84% (n = 21/25;24% CR + 8% PR+44% mCR+ 8% HI] in the treatment naïve ENA+AZA and 43% (n = 9/21;24% CR+5%PR+5% mCR+10% HI) in the HMA failure ENA arm (Table). Most common reason for Tx discontinuation was disease progression (ENA+AZA 20%, ENA 33%).5 pts (20%) received HCT in the ENA+AZA and 1 (5%) in the ENA arm. 7 pts in the ENA+AZA and 5 in the ENA arm were ongoing at data cutoff (Dec 31, 2020). After a median follow up of 12.6 mo, median OS was 32.2 mo in the ENA+AZA and 21.3 mo in the ENA arm. Conclusions: ENA is well tolerated and shows promising efficacy in IDH2-mutated higher risk MDS. Follow up and accrual is ongoing to better define duration and biomarkers of response.