<jats:title>Abstract</jats:title> <jats:p>Introduction: Translocations involving the MLL gene on chromosome 11q23 result in fusions with ≥10 partner genes that act as drivers in relatively chemotherapy resistant MLL-rearranged (MLLr) leukemias. These chimeric proteins form part of protein complexes that aberrantly upregulate transcription of the leukemogenic HOX and MEIS1 genes. Menin is a key member of the complex and localizes the complex to chromatin. Similarly, in NPM1 mutant (mNPM1) AML, the interaction between wild-type MLL and menin leads to a HOX and MEIS1-mediated leukemogenic transcriptional program. In preclinical models of MLLr and mNPM1 leukemias, inhibition of the interaction between MLL and menin downregulates HOX and MEIS1 transcription and reverses leukemogenesis (Uckelmann 2020; Krivstov 2019). SNDX-5613 (5613) is a potent, selective protein-protein interaction inhibitor of menin being evaluated in the AUGMENT-101 study, a first-in-human (FIH), Ph 1/2 study in pts with R/R acute leukemia. Here, we report the results of the completed, Ph 1 component.</jats:p> <jats:p>Methods: The study includes 2 parallel dose-escalation cohorts: pts not taking (Arm A) or taking (Arm B) strong CYP3A4 inhibitors. An early amendment restricted enrollment to MLLr or mNPM1 leukemias. Dose escalation used a "rolling 6" design with expansion at efficacious doses. 5613 is dosed orally q12h in continuous 28-day cycles. Dose levels evaluated in Arm A were 113 (n=1), 226 (n=6), 276 (n=10), and 339 mg (n=8), and in Arm B 113 (n=16), 163 (n=6), and 226 mg (n=7). Primary objectives of Ph 1 were to determine the safety, MTD, recommended Ph 2 dose (RP2D), and PK profile of 5613. Exploratory endpoints included antileukemic activity and pharmacodynamics of 5613.</jats:p> <jats:p>Results: As of 29Jun2021, 54 pts had received at least 1 dose of 5613; 13 pts remained on treatment. Baseline characteristics are detailed in Table 1. The median age was 49 years; 82% (n=44) of pts had AML; 65% (n=35) had MLLr leukemia, and 19% (n=10) had mNPM1 leukemia. Pts had a median of 3 prior therapies (range, 1-12); 57% and 44% had prior venetoclax or transplant, respectively; 59% of pts had not responded to their most recent line of therapy.</jats:p> <jats:p>5613 exhibited dose-proportional PK, and exposure increased ~2-3-fold when given with a strong CYP3A4 inhibitor. Measurement of target occupancy and gene expression showed that 5613 disrupted menin binding to chromatin and decreased leukemogenic gene expression consistent with the established mechanism of action.</jats:p> <jats:p>The only DLTs were Grade 3 prolonged QTc; all events were clinically asymptomatic. The MTD was 276 mg q12h in Arm A and 163 mg q12h in Arm B; 2 doses in each arm met the protocol-defined criteria (safety, percentage of planned dose intensity, and pharmacokinetic exposure) for a RP2D. The frequency of Grade 3 prolonged QTc at these doses was 8% (3/38). No ventricular arrhythmias were reported, and no pts discontinued 5613 due to a treatment-related event. Other common (&gt;10%) treatment-related AE (TRAE) were nausea (n=12; 22%), vomiting (n=9; 17%), differentiation syndrome (n=8; 15%), and diarrhea (n=6;11%). Grade ≥3 TRAE are shown in Table 2.</jats:p> <jats:p>In the 45 pts with MLLr or mNPM1 leukemias, responses were seen in both Arms A and B and at multiple dose levels. The composite CR (CRc: CR+CRh+CRp+CRi/MLFS) rate was 44% (20/45 pts) (Table 3). Among pts with MLLr leukemia, the CRc rate was 49% (17/35 pts) and in pts with mNPM1 leukemia, the CRc rate was 30% (3/10 pts); 14/20 (70%) pts with CRc achieved MRD negativity assessed locally by flow cytometry or PCR. Of 22 pts who received prior transplant, 10 (45%) achieved CRc. The CR/CRh rate was 22% (10/45) in pts with MLLr or mNPM1 leukemia. Median time to CR/CRh was 2 months (mo). With a median follow-up of 3.2 mo, the median duration of response (DoR) for patients achieving a CR/CRh was 5.2 mo. Responding patients were censored at the time they discontinued the study to proceed to an allogeneic stem cell transplant (n=6). Consistent with the proposed preclinical mechanism of menin inhibition, the 9 patients with wild-type MLL and NPM1 did not respond to 5613.</jats:p> <jats:p>Conclusion: In this FIH Ph 1 study, SNDX-5613 demonstrates an acceptable safety profile and promising antileukemic activity in pts with heavily pretreated R/R MLLr and mNPM1 acute leukemia. Two dose levels in each arm met the prespecified criteria for RP2D. Ph 2 expansion includes cohorts of pts with MLLr AML, MLLr ALL, and mNPM1 AML.</jats:p> <jats:p>Figure 1 Figure 1.</jats:p> <jats:p /> <jats:sec> <jats:title>Disclosures</jats:title> <jats:p>Stein: Foghorn Therapeutics: Consultancy; Blueprint Medicines: Consultancy; Gilead Sciences, Inc.: Consultancy; Abbvie: Consultancy; Janssen Pharmaceuticals: Consultancy; Genentech: Consultancy; Jazz Pharmaceuticals: Consultancy; Bristol Myers Squibb: Consultancy; Celgene: Consultancy; PinotBio: Consultancy; Daiichi Sankyo: Consultancy; Astellas: Consultancy; Novartis: Consultancy; Agios Pharmaceuticals, Inc: Consultancy; Syros Pharmaceuticals, Inc.: Consultancy; Syndax Pharmaceuticals: Consultancy. Stone: Syndax: Membership on an entity's Board of Directors or advisory committees; Syntrix/ACI: Membership on an entity's Board of Directors or advisory committees; GlaxoSmithKline: Consultancy; Innate: Consultancy; Janssen: Consultancy; Gemoab: Membership on an entity's Board of Directors or advisory committees; Foghorn Therapeutics: Consultancy; Elevate Bio: Membership on an entity's Board of Directors or advisory committees; Bristol Myers Squibb: Consultancy; Boston Pharmaceuticals: Consultancy; BerGen Bio: Membership on an entity's Board of Directors or advisory committees; Astellas: Membership on an entity's Board of Directors or advisory committees; Arog: Consultancy, Research Funding; Jazz: Consultancy; Onconova: Consultancy; AbbVie: Consultancy; Novartis: Consultancy, Research Funding; Syros: Membership on an entity's Board of Directors or advisory committees; Aprea: Consultancy; Amgen: Membership on an entity's Board of Directors or advisory committees; Actinium: Membership on an entity's Board of Directors or advisory committees; Takeda: Consultancy; Agios: Consultancy, Research Funding; Celgene: Consultancy; Macrogenics: Consultancy. Arellano: KITE Pharma, Inc: Consultancy; Syndax Pharmaceuticals, Inc: Consultancy. Rosen: Syndax: Current Employment. Meyers: Syndax Pharmaceuticals, Inc: Current Employment, Current equity holder in publicly-traded company, Current holder of individual stocks in a privately-held company, Patents & Royalties; Nuvalent: Consultancy, Membership on an entity's Board of Directors or advisory committees. Huang: Syndax: Current Employment, Current equity holder in publicly-traded company, Current holder of stock options in a privately-held company; Serapta: Ended employment in the past 24 months. Smith: Syndax: Consultancy; Tempest: Current holder of stock options in a privately-held company; Athira: Current holder of stock options in a privately-held company. Bagley: Syndax: Current Employment, Current equity holder in publicly-traded company, Current holder of stock options in a privately-held company; Radius Health: Ended employment in the past 24 months. Thirman: AbbVie: Consultancy, Other: TRAVEL, ACCOMMODATIONS, EXPENSES (paid by any for-profit health care company), Research Funding; Adaptive Biotechnologies: Consultancy; AstraZeneca: Consultancy; Celgene: Consultancy, Other: TRAVEL, ACCOMMODATIONS, EXPENSES (paid by any for-profit health care company); Pharmacyclics: Consultancy, Other: TRAVEL, ACCOMMODATIONS, EXPENSES (paid by any for-profit health care company); Merck: Research Funding; Syndax: Research Funding; TG Therapeutics: Research Funding. Patel: Ignyta: Research Funding; Incyte: Research Funding; Jacobio: Research Funding; Janssen: Membership on an entity's Board of Directors or advisory committees, Research Funding; Jounce Therapeutics: Research Funding; Klus Pharma: Research Funding; Kymab: Research Funding; Loxo Oncology: Research Funding; LSK Biopartners: Research Funding; Lycera: Research Funding; Mabspace: Research Funding; Macrogenics: Research Funding; Merck: Research Funding; Millennium Pharmaceuticals: Research Funding; Mirati Therapeutics: Research Funding; ModernaTX: Research Funding; ORIC Pharmaceuticals: Research Funding; Pfizer: Membership on an entity's Board of Directors or advisory committees, Research Funding; Phoenix Molecular Designs: Research Funding; Placon Therapeutics: Research Funding; Portola Pharmaceuticals: Research Funding; Prelude Therapeutics: Research Funding; Qilu Puget Sound Biotherapeutics: Research Funding; Revolution Medicines: Research Funding; Ribon Therapeutics: Research Funding; Seven and Eight Biopharmaceuticals: Research Funding; Syndax: Research Funding; Synthorx: Research Funding; Stemline Therapeutics: Research Funding; Taiho: Research Funding; Takeda: Research Funding; Tesaro: Research Funding; TopAlliance: Research Funding; Vedanta: Research Funding; Verastem: Research Funding; Vigeo: Research Funding; Xencor: Research Funding; Exelixis: Membership on an entity's Board of Directors or advisory committees; Bayer: Membership on an entity's Board of Directors or advisory committees; Pharmacyclics: Membership on an entity's Board of Directors or advisory committees; Abbvie: Membership on an entity's Board of Directors or advisory committees; Alexion, AstraZeneca Rare Disease: Other: Study investigator; Hutchinson MediPharma: Research Funding; Hengrui: Research Funding; H3 Biomedicine: Research Funding; Gilead: Research Funding; GlaxoSmithKline: Research Funding; Genentech/Roche: Membership on an entity's Board of Directors or advisory committees, Research Funding; Forma Therapeutics: Research Funding; Evelo Biosciences: Research Funding; Eli Lilly: Research Funding; EMD Serono: Membership on an entity's Board of Directors or advisory committees, Research Funding; Effector Therapeutics: Research Funding; Daiichi Sankyo: Research Funding; Cyteir Therapeutics: Research Funding; Curis: Research Funding; Clovis: Research Funding; Ciclomed: Research Funding; Checkpoint Therapeutics: Research Funding; Calithera: Research Funding; Boehringer Ingelheim: Research Funding; Celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding; BioNTech: Research Funding; Bicycle Therapeutics: Research Funding; AstraZeneca: Research Funding; Artios Pharma: Research Funding; Aileron Therapeutics: Research Funding; Agenus: Research Funding; ADC Therapeutics: Research Funding; Acerta Pharma: Research Funding; Florida Cancer Specialists: Research Funding. Issa: Syndax Pharmaceuticals: Research Funding; Novartis: Consultancy, Research Funding; Kura Oncology: Consultancy, Research Funding.</jats:p> </jats:sec>