BACKGROUND: Despite improvements in the treatment of "unfit or older" AML patients with the combination of azacitidine (AZA) and venetoclax (VEN), long-term survival for these patients remains poor. Additions to this new regimen may further improve patient outcomes. Overexpression of CD123, the alpha subunit of the IL-3 receptor, is seen in AML blasts. IMGN632 is a CD123-targeting antibody-drug conjugate (ADC) comprised of a high-affinity anti-CD123 antibody coupled to a DNA-alkylating payload of the novel IGN (indolinobenzodiazepine pseudodimer) class. Preclinical data have demonstrated synergy between IMGN632 and AZA and/or VEN, including overcoming AZA/VEN resistance in murine AML models (Kuruvilla ASH 2020), supporting the clinical exploration of these combinations. Doublets of IMGN632 with both AZA and VEN were studied in AML patients and supported testing of the triplet of IMGN632, AZA, and VEN. Here we report the initial safety and anti-leukemia activity findings from this novel triplet.

METHODS: This Phase 1b/2 study was designed to determine the safety, tolerability, and preliminary anti-leukemic activity of IMGN632 combined with AZA and VEN in patients with CD123-positive AML. To date, the triplet combination escalation consists of 5 cohorts of IMGN632 plus AZA and VEN, each agent designated by "C" for IMGN632 dose in mcg/kg, "A" for AZA dose in mg/m2 x7 days, or "V" for VEN # of days at 400mg QD. Four cohorts dosed IMGN632 on Day 7 of each cycle (C15A50V8, C15A50V14, C15A75V21, C45A50V8), and one cohort dosed IMGN632 on Day 1 of each cycle (Day 1 C15A50V14). Responses are determined using modified ELN criteria with a 14-day count recovery window.

RESULTS: At the time of this analysis, preliminary safety data are available for 35 relapsed or refractory (R/R) AML patients. The median age was 69y, 23% had secondary AML, 86% received prior intensive therapies, 37% that were refractory to first line therapy, and 51% had received prior VEN. Twenty-three percent of patients had FLT3 mutations.

The toxicity profile was manageable in this R/R AML population with multiple prior therapies. The most common treatment emergent adverse events (TEAE) all grades [grade 3+ events] seen in >20% of patients were infusion-related reactions (IRR, 37% [3%]), febrile neutropenia (26% [23%]), hypophosphatemia (26% [3%]), dyspnea (26% [6%]), pneumonia (20% [14%]), and fatigue (20% [0%]). One patient in the Day 1 C15A50V14 cohort discontinued IMGN632 due to a TEAE (DLT IRR, resolved). Cytopenias and infections were consistent with those observed with the AZA+VEN regimen in this R/R population. No TLS, VOD, capillary leak or cytokine release were observed. 30-day mortality was 0%.

Efficacy was seen across all cohorts/doses and schedules (efficacy evaluable population, n=29). The objective response rate (ORR) was 55% with a composite complete remission (CCR) rate of 31% (1 CR, 4 CRh, 2 CRp, 2 CRi). Higher intensity cohorts (IMGN632 dose 45 mcg/kg or 14-21 days of VEN) on the Day 7 schedule (n=20) were associated with higher response rates: ORR 75%, CCR rate 40% (Figure 1). At these higher intensity cohorts, in the VEN naïve subset (n=10), ORR/CCR rates were 100%/60%, respectively. Significant activity was also seen in the FLT3 mutant subset (n=7), with ORR/CCR rates of 100%/71%.

CONCLUSION: With a manageable safety profile in this R/R AML population, the novel IMGN632 triplet demonstrated compelling anti-leukemia activity. Ongoing escalation cohorts aim to optimize safety and efficacy of the triplet therapy. Expansion proof-of-concept cohorts are planned in both relapsed and frontline AML patients (NCT04086264). Updated safety, efficacy, and PK data will be presented.

Figure 1
Figure 1.
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Disclosures

Daver: Trillium: Consultancy, Research Funding; Daiichi Sankyo: Consultancy, Research Funding; Sevier: Consultancy, Research Funding; Glycomimetics: Research Funding; ImmunoGen: Consultancy, Research Funding; Astellas: Consultancy, Research Funding; Genentech: Consultancy, Research Funding; Bristol Myers Squibb: Consultancy, Research Funding; Novimmune: Research Funding; Gilead Sciences, Inc.: Consultancy, Research Funding; Hanmi: Research Funding; Amgen: Consultancy, Research Funding; Abbvie: Consultancy, Research Funding; FATE Therapeutics: Research Funding; Trovagene: Consultancy, Research Funding; Novartis: Consultancy; Pfizer: Consultancy, Research Funding; Jazz Pharmaceuticals: Consultancy, Other: Data Monitoring Committee member; Dava Oncology (Arog): Consultancy; Celgene: Consultancy; Syndax: Consultancy; Shattuck Labs: Consultancy; Agios: Consultancy; Kite Pharmaceuticals: Consultancy; SOBI: Consultancy; STAR Therapeutics: Consultancy; Karyopharm: Research Funding; Newave: Research Funding. Aribi: Seagen: Consultancy. Montesinos: Teva: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Incyte: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Sanofi: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Karyopharm: Membership on an entity's Board of Directors or advisory committees, Research Funding; Pfizer: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Daiichi Sankyo: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Glycomimetics: Consultancy; Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Tolero Pharmaceutical: Consultancy; Janssen: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Stemline/Menarini: Consultancy; Forma Therapeutics: Consultancy; Novartis: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Agios: Consultancy; AbbVie: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Astellas Pharma, Inc.: Consultancy, Honoraria, Other: Advisory board, Research Funding, Speakers Bureau. Roboz: Astex: Consultancy; Jazz: Consultancy; Glaxo SmithKline: Consultancy; Mesoblast: Consultancy; Blueprint Medicines: Consultancy; AstraZeneca: Consultancy; Bayer: Consultancy; Daiichi Sankyo: Consultancy; Amgen: Consultancy; MEI Pharma - IDMC Chair: Consultancy; Astellas: Consultancy; Agios: Consultancy; Actinium: Consultancy; AbbVie: Consultancy; Janssen: Research Funding; Jasper Therapeutics: Consultancy; Celgene: Consultancy; Helsinn: Consultancy; Janssen: Consultancy; Bristol Myers Squibb: Consultancy; Novartis: Consultancy; Otsuka: Consultancy; Pfizer: Consultancy; Roche/Genentech: Consultancy. Wang: Jazz Pharmaceuticals: Consultancy, Honoraria, Other: Advisory Board; BMS/Celgene: Membership on an entity's Board of Directors or advisory committees; Pfizer: Consultancy, Honoraria, Other: Advisory Board, Speakers Bureau; Astellas: Consultancy, Membership on an entity's Board of Directors or advisory committees; Stemline Therapeutics: Consultancy, Honoraria, Other: Advisory board, Speakers Bureau; Kura Oncology: Consultancy, Honoraria, Other: Advisory board, steering committee, Speakers Bureau; AbbVie: Consultancy, Membership on an entity's Board of Directors or advisory committees; Mana Therapeutics: Consultancy, Honoraria; GlaxoSmithKline: Consultancy, Honoraria, Other: Advisory Board; Novartis: Consultancy, Honoraria, Other: Advisory Board; Kite Pharmaceuticals: Consultancy, Honoraria, Other: Advisory Board; Genentech: Membership on an entity's Board of Directors or advisory committees; Takeda: Consultancy, Honoraria, Other: Advisory board; DAVA Oncology: Consultancy, 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. Walter: Agios Pharmaceuticals, Inc.: Consultancy, Research Funding; Amgen, Inc.: Consultancy, Research Funding; Amphivena Therapeutics, Inc.: Current equity holder in publicly-traded company; Aptevo Therapeutics, Inc.: Consultancy, Research Funding; Arog Pharmaceuticals, Inc.: Research Funding; Astellas Pharma US, Inc.: Consultancy; BioLineRx, Ltd.: Consultancy, Research Funding; Boston Biomedical, Inc.: Consultancy; Bristol Myers Squibb, Inc.: Consultancy; Celgene, Inc.: Consultancy, Research Funding; Genentech, Inc.: Consultancy; GlaxoSmithKline, Inc.: Consultancy; ImmunoGen, Inc.: Research Funding; Janssen Global Services, LLC: Consultancy; Janssen Research & Development, Inc.: Research Funding; Jazz Pharmaceuticals, Inc.: Consultancy, Research Funding; Kite Pharma, Inc.: Consultancy; Kronos Bio, Inc.: Consultancy; Kura Oncology, Inc.: Research Funding; Macrogenics, Inc.: Research Funding; New Link Genetics: Consultancy; Pfizer, Inc.: Consultancy, Research Funding; Race Oncology Ltd.: Consultancy; Selvita: Research Funding; Stemline Therapeutics, Inc.: Research Funding. Jeyakumar: Jazz: Research Funding; Pfizer: Research Funding. DeAngelo: Abbvie: Research Funding; Blueprint Medicines Corporation: Consultancy; Incyte Corporation: Consultancy; Forty-Seven: Consultancy; Autolus: Consultancy; Agios: Consultancy; Amgen: Consultancy; GlycoMimetics: Research Funding; Shire: Consultancy; Takeda: Consultancy; Novartis: Consultancy, Research Funding; Pfizer: Consultancy; Jazz: Consultancy. Erba: Celgene: Membership on an entity's Board of Directors or advisory committees; AbbVie, Agios, Amgen, Astellas Pharma, Celgene, Daiichi Sankyo, Glycomimetics, ImmunoGen, Incyte, Jazz Pharmaceuticals, MacroGenics, Novartis, and Pfizer: Consultancy; Glycomimetics: Membership on an entity's Board of Directors or advisory committees; Covance (AbbVie): Other: Independent Review Committee ; AbbVie, Agios, Celgene, Incyte, Jazz Pharmaceuticals, and Novartis: Speakers Bureau; AbbVie, Daiichi Sankyo, Forma, ImmunoGen, Jazz Pharmaceuticals, MacroGenics, Novartis, and PTC: Research Funding. Advani: Abbvie: Research Funding; Immunogen: Research Funding; Seattle Genetics: Membership on an entity's Board of Directors or advisory committees, Research Funding; Pfizer: Honoraria, Research Funding; OBI: Research Funding; Glycomimetics: Membership on an entity's Board of Directors or advisory committees, Research Funding; Macrogenics: Research Funding; Amgen: Membership on an entity's Board of Directors or advisory committees, Research Funding; Kite Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees, Research Funding. Martinelli: Celgene /BMS: Consultancy, Speakers Bureau; Stemline Therapeutics: Consultancy; Roche: Consultancy; Jazz Pharmaceuticals: Consultancy; Pfizer: Consultancy, Speakers Bureau; Abbvie: Consultancy; Daichii Sankyo: Consultancy; Incyte: Consultancy; Astellas: Consultancy, Speakers Bureau. Gastaud: PFIZER: Consultancy; CELGENE/BMS: Consultancy; ABBVIE: Consultancy; GSK: Consultancy. Altman: Biosight: Membership on an entity's Board of Directors or advisory committees, Other: reimbursement for travel, Research Funding; ImmunoGen: Research Funding; Kartos Therapeutics: Research Funding; Kura Oncology: Membership on an entity's Board of Directors or advisory committees, Research Funding; Fujifilm: Research Funding; Glycomimetics: Other: data monitoring committee; Loxo: Research Funding; Celgene: Research Funding; Boehringer Ingelheim: Research Funding; Astellas: Honoraria, Research Funding; Aptos: Research Funding; Aprea: Research Funding; Amgen: Research Funding; Abbvie: Honoraria, Research Funding; ALX Oncology Inc.: Research Funding; Syros: Membership on an entity's Board of Directors or advisory committees. de la Fuente: Incyte: Consultancy, Speakers Bureau; Abbie: Consultancy, Speakers Bureau; Novartis: Research Funding; BMS: Consultancy, Speakers Bureau. Gaidano: Incyte: Membership on an entity's Board of Directors or advisory committees; Beigene: Membership on an entity's Board of Directors or advisory committees; Astrazeneca: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Abbvie: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Janssen: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Curti: Jazz Pharma: Membership on an entity's Board of Directors or advisory committees; Pfizer: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees; Abbvie: Membership on an entity's Board of Directors or advisory committees. Boissel: PFIZER: Consultancy, Honoraria; Novartis: Consultancy, Honoraria, Research Funding; Amgen: Consultancy, Honoraria, Research Funding; CELGENE: Honoraria; Bristol-Myers Squibb: Honoraria, Research Funding; SANOFI: Honoraria; Servier: Consultancy, Honoraria; Incyte: Honoraria; JAZZ Pharma: Honoraria, Research Funding. Recher: Pfizer: Honoraria, Membership on an entity's Board of Directors or advisory committees; Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Macrogenics: Honoraria, Membership on an entity's Board of Directors or advisory committees; MaatPharma: Research Funding; Jazz: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Janssen: Honoraria; Incyte: Honoraria; Daiichi Sankyo: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; BMS/Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Astellas: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Amgen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Roche: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees; Agios: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; AbbVie: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding. Schliemann: Philogen S.p.A.: Consultancy, Honoraria, Research Funding; Abbvie: Consultancy, Other: travel grants; Astellas: Consultancy; AstraZeneca: Consultancy; Boehringer-Ingelheim: Research Funding; BMS: Consultancy, Other: travel grants; Jazz Pharmaceuticals: Consultancy, Research Funding; Novartis: Consultancy; Roche: Consultancy; Pfizer: Consultancy. Konopleva: Cellectis: Other: grant support; Calithera: Other: grant support, Research Funding; F. Hoffmann-La Roche: Consultancy, Honoraria, Other: grant support; Forty Seven: Other: grant support, Research Funding; Agios: Other: grant support, Research Funding; Ablynx: Other: grant support, Research Funding; Genentech: Consultancy, Honoraria, Other: grant support, Research Funding; KisoJi: Research Funding; Ascentage: Other: grant support, Research Funding; Eli Lilly: Patents & Royalties: intellectual property rights, Research Funding; Reata Pharmaceuticals: Current holder of stock options in a privately-held company, Patents & Royalties: intellectual property rights; Novartis: Other: research funding pending, Patents & Royalties: intellectual property rights; AstraZeneca: Other: grant support, Research Funding; Rafael Pharmaceuticals: Other: grant support, Research Funding; Sanofi: Other: grant support, Research Funding; Stemline Therapeutics: Research Funding; AbbVie: Consultancy, Honoraria, Other: Grant Support, Research Funding. Sallman: Takeda: Consultancy; AbbVie: Membership on an entity's Board of Directors or advisory committees; Agios: Membership on an entity's Board of Directors or advisory committees; Aprea: Membership on an entity's Board of Directors or advisory committees, Research Funding; Bristol-Myers Squibb: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Shattuck Labs: Membership on an entity's Board of Directors or advisory committees; Incyte: Speakers Bureau; Kite: Membership on an entity's Board of Directors or advisory committees; Syndax: Membership on an entity's Board of Directors or advisory committees; Intellia: Membership on an entity's Board of Directors or advisory committees; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees; Magenta: Consultancy. Marcucci: Novartis: Other: Speaker and advisory scientific board meetings; Agios: Other: Speaker and advisory scientific board meetings; Abbvie: Other: Speaker and advisory scientific board meetings. Kantarjian: KAHR Medical Ltd: Honoraria; Ipsen Pharmaceuticals: Honoraria; Immunogen: Research Funding; Jazz: Research Funding; Ascentage: Research Funding; Novartis: Honoraria, Research Funding; Amgen: Honoraria, Research Funding; NOVA Research: Honoraria; Pfizer: Honoraria, Research Funding; AbbVie: Honoraria, Research Funding; BMS: Research Funding; Daiichi-Sankyo: Research Funding; Astra Zeneca: Honoraria; Aptitude Health: Honoraria; Astellas Health: Honoraria; Taiho Pharmaceutical Canada: Honoraria; Precision Biosciences: Honoraria. Malcolm: Immunogen: Current Employment. Zweidler-McKay: ImmunoGen: Current Employment. Sweet: Astellas: Consultancy, Membership on an entity's Board of Directors or advisory committees; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees; Gilead: Membership on an entity's Board of Directors or advisory committees; AROG: Membership on an entity's Board of Directors or advisory committees; Bristol Meyers Squibb: Honoraria, Membership on an entity's Board of Directors or advisory committees.

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2021
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