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Background: Modakafusp alfa (previously known as TAK-573) is a first-in-class immunocytokine designed to deliver interferon alpha-2b (IFNα2b) to CD38+ cells. It consists of two attenuated IFNα2b molecules genetically fused to the Fc portion of a humanized, anti-CD38, IgG4 monoclonal antibody (mAb). The specificity for CD38 and reduced IFN receptor binding affinity of the attenuated IFNα2b molecules significantly reduces the potential for off-target binding and toxicity. Furthermore, modakafusp alfa binds to a different epitope on CD38 than the currently approved anti-CD38 therapeutic mAbs, daratumumab and isatuximab. Preclinical evaluation of modakafusp alfa supports activation of type I IFN signaling in CD38+ cells, inducing direct anti-proliferative effects on myeloma cells, as well as direct and indirect immune cell activation. We have previously reported preliminary results from the first 59 patients (pts) in our first-in-human phase 1 trial of modakafusp alfa in pts with relapsed/refractory multiple myeloma (RRMM; NCT03215030), showing responses to single-agent therapy with doses starting at 0.1 mg/kg weekly; thrombocytopenia and neutropenia were dose-limiting toxicities when modakafusp alfa was administered weekly (QW), every 2 weeks (Q2W), and every 3 weeks (Q3W) (Vogl, Blood 2020). Here we report updated results from this trial, focusing on results from an expansion cohort with dosing every 4 weeks (Q4W). Methods: Eligible pts with RRMM who had received at least three previous lines of treatment received modakafusp alfa as a 1- to 4-hour intravenous infusion at 11 dose levels from 0.001 to 6 mg/kg following a 3+3 dose-escalation design. The initial dosing schedule was QW for 8 doses, then Q2W for 8 doses, and then monthly; subsequent cohorts evaluated dosing Q2W, Q3W or Q4W. Expansion cohorts were planned using modakafusp alfa at protocol-defined, biologically active doses that did not exceed the maximum tolerated dose (MTD). Results: As of May 2021, 83 pts had been treated across all planned dosing schedules. With Q4W dosing, the MTD was exceeded at the 6 mg/kg dose due to DLTs: a grade 3 infusion reaction and prolonged thrombocytopenia and neutropenia, which delayed the start of cycle 2 by >14 days. In total, 24 pts were treated with 1.5 mg/kg modakafusp alfa Q4W (5 pts during dose escalation and 19 pts in an expansion cohort). Analyses include data from all 24 pts. The median number of prior lines of therapy received was 6 (range 4-16); 21 pts (88%) were refractory to an anti-CD38 mAb, and 20 (83%) were triple class-refractory (to a proteasome inhibitor, an immunomodulatory drug, and an anti-CD38 mAb). Grade 3 or higher treatment-emergent adverse events (TEAEs) were reported in 18 pts (75%). The most frequent grade 3-4 TEAEs were neutropenia in 12 pts (50%; grade 4 in 6 [25%]), leukopenia in 9 (38%), decreased lymphocyte count in 9 (38%), anemia in 8 (33%), and thrombocytopenia in 8 (33%; grade 4 in 3 [13%]). One pt (4%) had a grade 3 bleeding event and continues on study treatment; 3 pts (13%) had infections (grade 3 in 2 [8%]); and 8 (33%) had infusion reactions (grade 3 in 1 [4%]). The overall response rate (ORR, ≥partial response [PR]) was 42% (complete response [CR], n=2; very good partial response [VGPR], n=5; PR, n=3), and the clinical benefit rate (ORR + minimal response [MR]) was 54% (MR, n=3). Median progression-free survival was 5.7 months (95% confidence interval [CI], 1.9-not reached [NR]), median time to response was 1.9 months (95% CI, 0.95-NR), and median duration of response was 7.4 months (95% CI, 2.3-NR). Among the 21 anti-CD38 mAb-refractory pts, the ORR was 43%, while among the 4 pts who received an anti-CD38 mAb in their most recent line of therapy prior to enrollment, the ORR was 75% (CR, n=1; VGPR, n=2). Correlative studies show evidence of T-cell and natural killer-cell activation, as well as activation of IFN signaling in CD38+ cells, including upregulation of CD38 expression. Conclusion: Modakafusp alfa (TAK-573) is a novel candidate for the treatment of RRMM, which has shown promising anti-myeloma activity in heavily pretreated pts, including anti-CD38 mAb-refractory pts and those who have received an anti-CD38 mAb in their most recent line of treatment. A Q4W dosing schedule of modakafusp alfa is feasible and the optimal dose and potential combinations are being explored. Disclosures Vogl: Takeda: Consultancy, Research Funding; Karyopharm: Consultancy; GSK: Consultancy; Oncopeptides: Consultancy; Janssen: Consultancy; Sanofi: Consultancy; CSL Behring: Consultancy; Active Biotech: Research Funding. Kaufman: Genentech, AbbVie, Janssen: Consultancy, Research Funding; Amgen: Research Funding; Janssen: Honoraria; Roche/Genetech, Tecnopharma: Consultancy, Honoraria; Fortis Therapeutics: Research Funding; Novartis: Research Funding; Incyte, celgene: Consultancy; Sutro, Takeda: Research Funding; Tecnofarma SAS, AbbVie: Honoraria; BMS: Consultancy, Research Funding; Incyte, TG Therapeutics: Membership on an entity's Board of Directors or advisory committees; Heidelberg Pharma: Research Funding. Holstein: Oncopeptides: Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees; Genentech, GSK, Janssen, Secura Bio, Sorrento: Honoraria; Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees. Atrash: AMGEN: Research Funding; Jansen: Research Funding, Speakers Bureau; GSK: Research Funding. Nadeem: Takeda: Membership on an entity's Board of Directors or advisory committees; Adaptive Biotechnologies: Membership on an entity's Board of Directors or advisory committees; GSK: Membership on an entity's Board of Directors or advisory committees; BMS: Membership on an entity's Board of Directors or advisory committees; Karyopharm: Membership on an entity's Board of Directors or advisory committees. Janakiram: Kyowa Kirin Therapeutics: Honoraria; Takeda Pharmaceuticals: Research Funding; FATE Therapeutics: Research Funding; ADC Therapeutics: Research Funding. Suryanarayan: Takeda: Current Employment. Liu: Takeda: Current Employment. Parot: Takeda Pharmaceuticals: Current Employment. OffLabel Disclosure: Modakafusp alfa (TAK-573) is a first-in-class immunocytokine consisting of 2 attenuated interferon alpha-2b molecules genetically fused to an anti-CD38, IgG4 monoclonal antibody. This abstract contains information about investigational use of modakafusp alfa in patients with relapsed/refractory multiple myeloma. Safety and efficacy have not been determined.

Background: TAK-573 is a first-in-class, humanized, anti-CD38, IgG4 monoclonal antibody genetically fused to 2 attenuated interferon alpha-2b (IFNα2b) molecules. The specificity for CD38 and reduced binding affinity of the attenuated IFNα molecules significantly reduces the potential for off-target toxicity. TAK-573 binds to a site on CD38 that is distinct from the binding sites of currently available therapeutic antibodies, and therefore does not compete for binding with daratumumab or isatuximab. Non-clinical studies have shown that TAK-573 has robust anti-tumor activity, including complete responses, in MM xenograft models. Patients and Methods: The first in human phase I trial (NCT03215030) enrolled patients (pts) with relapsed or refractory multiple myeloma (RRMM) after at least 3 previous lines of treatment. Pts received TAK-573 as a 1 to 4-hour IV infusion in 11 dose levels from 0.001 to 3 mg/kg. The initial schedule was weekly for 8 doses, then every 2 weeks for 8 doses, and then monthly. Subsequent cohorts are also exploring dosing once every 2 (Q2), every 3 (Q3) or every 4 weeks (Q4). Peripheral blood (PB) and bone marrow (BM) aspirates were collected before and after TAK-573 dosing. CD38 receptor occupancy (RO) and receptor density (RD) were determined using 9-color flow cytometry. Serum samples were analyzed using the Immuno-Oncology panel of Olink's proximity extension assay platform to measure changes in cytokine and chemokine levels. Whole transcriptome sequencing of bulk RNA was performed to determine the type I interferon (IFN) gene signature induction. Mass cytometry-based immunophenotyping was utilized to characterize changes in immune cell prevalence and activation status of cryopreserved cells from both the PB and BM. Results: As of June 2020, 59 patients had been treated on all schedules. The median number of prior lines of therapy was 7 (range: 3-20); 93% had received at least 1 daratumumab-containing regimen, and 14% had received previous CAR-T cell therapy. Thrombocytopenia was the most frequent TEAE (83%) and was Grade ≥3 in 28 (47%) pts. Prolonged thrombocytopenia was a dose limiting toxicity (DLT) in 7 pts, but was not associated with clinical bleeding, and 9 pts required platelet transfusions. Neutropenia was reported as a TEAE in 54% of pts (Grade ≥3 in 49% pts), and was a DLT in 4 patients, including one pt who had febrile neutropenia. The maximum tolerated dose for the initial schedule was 0.1 mg/kg, and evaluation of other schedules is ongoing. Myeloma responses have been observed starting at doses of 0.1 mg/kg on the initial schedule, 0.4 mg/kg q2 weeks, and 1.5 mg/kg q4 weeks (as shown in Table 1). Single administration of TAK-573 resulted in a dose dependent increase in CD38 RO of PB-derived immune cells, with saturation of CD38 RO 4 hours after the end of infusion (EOI) at doses ≥ 0.2 mg/kg. The duration of saturation was dose dependent, with doses ≥ 0.75 mg/kg TAK-573 saturating CD38 RO through 24 hours. CD38 RO in BM samples showed similar results, with added variability due to the timing of sample collection and individual patients' tumor burden. At all dose levels, TAK-573 administration resulted in increases in the type I IFN gene signature 24 hours after the dose. As CD38 is an IFN-stimulated gene, TAK-573 treatment resulted in CD38 RD increases, most notably on NK cells but also on other CD38 positive cells, including MM cells within the BM. BM MM cells also showed decreases in complement-inhibitory proteins CD55 and CD59 after TAK-573 treatment. Circulating levels of IFN-associated chemokines (IFNγ, CXCL10, MCP-1 and IL-15) also increased, with maximal induction 4 hours after EOI. CD69 expression, a marker of early activation, increased on BM CD8+ T cells in 7 of 9 patients analyzed; the CD8+ T-cells for 3 of those 7 patients also showed increases in IFNγ positivity, indicating that TAK-573 treatment can increase the cytolytic potential of CD8+ T-cells in the BM of a subset of patients. Conclusion: TAK-573 is a clinically and pharmacologically active molecule that mediates IFNAR pathway modulation and leads to myeloma responses. Additional biomarker data is being collected to further refine the MOA, which will inform the recommended phase 2 dose, optimal schedule of administration, and rational development of TAK-573. Disclosures Vogl: Active Biotech: Consultancy, Research Funding; Takeda: Consultancy; Karyopharm: Consultancy; Celgene: Consultancy; Janssen: Consultancy; Oncopeptides: Consultancy; MorphoSys: Consultancy. Kaufman:Takeda: Consultancy, Honoraria; Incyte: Consultancy, Membership on an entity's Board of Directors or advisory committees; Pharmacyclics: Membership on an entity's Board of Directors or advisory committees; Bristol-Myers Squibb: Consultancy, Honoraria; Celgene: Consultancy, Honoraria; TG Therapeutics: Consultancy, Membership on an entity's Board of Directors or advisory committees; Karyopharm: Membership on an entity's Board of Directors or advisory committees; Sanofi/Genyzme: Consultancy, Honoraria; Janssen: Consultancy, Honoraria; Tecnopharma: Consultancy, Honoraria; Amgen: Consultancy, Honoraria; AbbVie: Consultancy. Holstein:GSK: Consultancy; Celgene: Consultancy; Sorrento: Consultancy; Sanofi: Consultancy; Oncopeptides: Consultancy, Research Funding; Takeda: Consultancy; Adaptive Biotechnologies: Consultancy; Genentech: Consultancy. Nadeem:Takeda: Membership on an entity's Board of Directors or advisory committees; Janssen: Consultancy; Sanofi: Consultancy, Membership on an entity's Board of Directors or advisory committees; Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees. Suryanarayan:Millennium Pharmaceuticals, Inc., Cambridge, MA, USA, a wholly owned subsidiary of Takeda Pharmaceutical Company Limited: Current Employment. Collins:Millennium Pharmaceuticals, Inc., Cambridge, MA, USA, a wholly owned subsidiary of Takeda Pharmaceutical Company Limited: Current Employment. Parot:Millennium Pharmaceuticals, Inc., Cambridge, MA, USA, a wholly owned subsidiary of Takeda Pharmaceutical Company Limited: Current Employment. Chaudhry:Sanofi: Consultancy, Membership on an entity's Board of Directors or advisory committees. OffLabel Disclosure: TAK-573 is a first-in-class, humanized, anti-CD38, IgG4 monoclonal antibody genetically fused to 2 attenuated interferon alpha-2b (IFNα2b) molecules

Background Spleen tyrosine kinase (SYK) is a nonreceptor cytoplasmic protein kinase and a key mediator of immunoreceptor signaling that has been shown to play an important role in the pathogenesis of both B-cell and myeloid malignancies. SYK has also been shown to directly bind and activate FMS-like tyrosine kinase 3 (FLT-3), a Class III receptor tyrosine kinase that is commonly mutated in approximately 30% of pts with AML (Puissant et al. Cancer Cell 2014;25:226-42). TAK-659 is an investigational, reversible, and potent dual inhibitor of SYK and FLT-3. Preclinical studies with TAK-659 have demonstrated growth inhibition of cell lines and xenograft tumor models of B-cell lymphoma or AML origin. Moreover, TAK-659 has exhibited antitumor activity in lymphoma pts in an ongoing clinical trial (Petrich et al. Blood 2015;126:2693). The primary objectives of the phase 1b dose-finding portion of this study are to evaluate the safety, tolerability, and maximum tolerated dose (MTD)/recommended phase 2 dose (RP2D) of TAK-659, as well as preliminary efficacy in the phase 2 expansion study. Secondary objectives include evaluation of TAK-659 pharmacokinetics (PK) in this pt population. Methods During dose escalation using a 3x3 schema, adult pts with R/R AML received oral TAK-659 daily (QD) in 28-d cycles (C) starting with a dose of 60 mg. Adverse events (AEs) were assessed per NCI-CTCAE v4.03. Response per IWG criteria for AML was assessed between d22 and d28 of C1, C2, and C4. Blood samples for plasma pharmacokinetic (PK) assessments were collected pre-dose and at multiple times post-dose on d1 and d15 of C1. The pharmacodynamic effect of TAK-659 was assessed at multiple time points by measuring the phosphorylation of ribosomal protein S6 (pS6) in peripheral AML blasts using flow cytometry. FLT-3 mutation status (wild type [FLT-3-WT], FLT-3-ITD, or point mutation [FLT-3-D835Y]) was assessed using a PCR-based assay at a central laboratory. The effect of TAK-659 treatment on FLT-3-ITD phosphorylation was evaluated using a plasma inhibitory assay (PIA) as previously described (Levis et al. Blood 2006;108:3477-83). Results At data cut-off (June 9, 2016), 15 pts had been enrolled at TAK-659 QD 60 mg (n=4), 100 mg (n=7), or 120 mg (n=4). No dose-limiting toxicity per protocol has been observed. Dose escalation is currently ongoing at 160 mg QD. In the safety population (n=13), median age was 67 yrs (range 25-86), 69% of pts were male, and 38% had received ≥4 prior lines of therapy. Baseline mutation data was available for 12 pts: 6 pts were FLT-3-WT, 3 pts had FLT-3-ITD, 1 pt had FLT-3-D835Y, and 2 pts had concurrent FLT-3-ITD/D835Y mutations. In the safety population, all-grade drug-related AEs occurred in 12 (92%) pts overall; the most common were elevated AST (31%), ALT (23%), and amylase levels (23%). Grade ≥3 drug-related AEs occurred in 7 (54%) pts including: increased ALT, AST, and amylase levels, cataract, positive fungal test, macular fibrosis, pancreatitis, pneumocystis jirovecii pneumonia, rash, and fungal sinusitis (each 1pt). Blood LDH levels were increased in almost all pts (significance unknown). Three pts discontinued TAK-659 due to AEs and 3 pts died on study; none of these events were considered related to the study drug. Preliminary plasma PK of TAK-659 (n=11, 60-100 mg) was characterized by rapid absorption (median Tmax of 2 hours), moderate variability in steady-state exposures (42% coefficient of variation for C1 d15 dose-normalized AUCtau), and mean accumulation of 2.1-fold after repeated QD dosing for 15 days. Of 9 pts evaluated to date, pS6 was detected at baseline and reduced after dosing in 4 pts (2 FLT-3-ITD; 2 FLT-3-WT). At 60 mg and 100 mg TAK-659, up to 70% inhibition of FLT-3-ITD phosphorylation was observed as assessed by PIA. Early signs of clinical activity were observed, with decreases in peripheral blood myeloblasts observed in some pts. Assessment is ongoing and preliminary efficacy data will be presented. Conclusions TAK-659 has a unique mechanism of action with dual inhibition of SYK and FLT-3. Dose escalation to determine the MTD/RP2D is ongoing. TAK-659 exhibits an acceptable PK profile in R/R AML pts, supporting continuous oral QD dosing. Disclosures Kaplan: Seattle Genetics: Research Funding; Janssen: Research Funding. Morris:Boehringer-Ingelheim: Speakers Bureau. Altman:Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees; Syros: Honoraria, Membership on an entity's Board of Directors or advisory committees; BMS: Honoraria, Membership on an entity's Board of Directors or advisory committees; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees. Wise-Draper:Merck: Research Funding. Collins:Millennium Pharmaceuticals Inc., Cambridge, MA, USA, a wholly owned subsidiary of Takeda Pharmaceutical Company Limited: Employment. Kannan:Millennium Pharmaceuticals Inc., Cambridge, MA, USA, a wholly owned subsidiary of Takeda Pharmaceutical Company Limited: Employment. Wang:Millennium Pharmaceuticals Inc., Cambridge, MA, USA, a wholly owned subsidiary of Takeda Pharmaceutical Company Limited: Employment. Faucette:Millennium Pharmaceuticals Inc., Cambridge, MA, USA, a wholly owned subsidiary of Takeda Pharmaceutical Company Limited: Employment. Lee:Millennium Pharmaceuticals Inc., Cambridge, MA, USA, a wholly owned subsidiary of Takeda Pharmaceutical Company Limited: Employment. Shou:Millennium Pharmaceuticals Inc., Cambridge, MA, USA, a wholly owned subsidiary of Takeda Pharmaceutical Company Limited: Employment. Levis:Millennium: Consultancy, Research Funding; Astellas: Consultancy, Honoraria, Research Funding; Novartis: Consultancy, Honoraria, Research Funding; Daiichi-Sankyo: Consultancy, Honoraria.

In order to more precisely understand the effects of MEK1/2 inhibition on cell cycle progression, cellular imaging and biochemical assays were coupled with mathematical modeling. The MEK/ERK signaling cascade modulates multiple outcomes relevant to cancer therapy including cell growth, proliferation, differentiation and apoptosis. Moreover, MEK/ERK signaling regulates transitions between the G1, S and G2 cell cycle phases, and mediates the response to DNA damage induced by a wide variety of DNA damaging agents. Inhibition of the MEK/ERK pathway represents a promising approach for the treatment of cancer. A number of small-molecule inhibitors are currently in clinical trials, including TAK-733, a novel, investigational, selective, non ATP competitive, allosteric inhibitor of MAP kinase-ERK kinase (MEK) activity. MEK inhibition is often described to invoke a complete arrest at the G1-S cell cycle transition leading to a rapid cessation of cell growth. In order to assess this, the kinetics of cell cycle progression using continuous quantitative techniques in several different cell types was examined. Time-lapse microscopy studies and confluence analyses using an IncuCyte system demonstrated that cells treated with TAK-733 continue to divide over a period of five days, albeit at a slower rate than the DMSO treated cells. These observations were corroborated with flow cytometry using CFSE, a fluorescent cytoplasmic dye whose rate of decay is a measure of the cell division rate, and with immunofluorescence microscopy using the G2/M marker cyclin B. This continued cell cycling in the presence of TAK-733 was demonstrated to occur with abnormal cell cycle progression times and abnormal DNA content profiles, suggesting altered rates of passage through S and G2/M phase. A mathematical model was constructed to quantitatively describe how MEK inhibition is affecting the passage of the cell population through the cell cycle. When the model is fitted to the experimentally observed data, it inferred the rate of entrance and exit from each phase of the cell cycle under both control and treatment conditions. The model simultaneously captured both the observed accumulation in G0/G1 as well as the observed progression through the cell cycle during treatment. Interestingly, it was able to explain both of these results without invoking a complete G1 arrest. Instead it showed that the rate of exit from G1 is reduced upon inhibition. These findings were supported by time-lapse microscopy observations which were not used in fitting the model. This reassessment of the canonical view of cell-cycle progression defects following MEK1/2 inhibition by means of the mathematical modeling approach described here may provide key differentiation opportunities in the rational development of TAK-733 and other MEK1/2 inhibitors. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr B136.