Abstract: Background: Autologous CD19-targeting chimeric antigen receptor T cell (CAR-T) products are approved as standard treatment options for patients (pts) with relapsed diffuse large cell lymphoma (DLBCL), mantle cell lymphoma (MCL), and follicular lymphoma (FL). Their long-term efficacy for DLBCL is ~40% and is unknown for other histologies. Additionally, associated toxicities including cytokine-release syndrome (CRS) and immune effector cell-associated neurotoxicity syndrome (ICANS) remain a challenge. CD20 is a proven target for treatment of B-NHLs/CLL with demonstrated high clinical efficacy of unmodified, radiolabeled, and bispecific antibodies. Therefore, CD20-targeted CAR-T represents a promising adoptive immunotherapy option that could be utilized to treat relapsed/refractory (R/R) B-NHLs and CLL. MB-106 is a fully human 3rd-generation CD20-targeted CAR-T product with both 4-1BB and CD28 costimulatory domains. We present results of our ongoing phase I/II clinical trial investigating safety and efficacy of CD20 CAR-T for high-risk B-NHLs and CLL (NCT03277729). Methods: Pts with R/R CD20+ B-cell malignancies are eligible, including but not limited to DLBCL, FL, MCL, and CLL. Prior treatment with CD19 CAR-T is permitted. Lymphodepletion (LD) consists of cyclophosphamide (Cy) ± fludarabine (Flu). CAR-T cells are administered at one of 4 dose levels (DL): DL1: 3.3x10 5, DL2: 1x10 6, DL3: 3.3x10 6, DL4: 1x10 7 CAR T cells/kg. A continual reassessment method dose escalation design was used to find the maximally tolerated dose. CAR-T is infused in the outpatient setting except for the first pt of each dose cohort (overnight observation). Treatment response is assessed on day 28. CRS and ICANS are graded per ASTCT consensus grading. The study underwent a major cell manufacturing modification after treating 7 pts with no objective responses as previously reported (Shadman, ASH 2020, #1443). This abstract includes pts who were treated under the modified process. Results: Between Dec 2019 and July 2021, 16 pts (12 FL, 2 MCL, 1 CLL, 1 DLBCL) were treated after LD with Cy-Flu and had day 28 assessment. All DLs were reached (see table), with no dose-limiting toxicities to date. CRS occurred in 7 pts (44%): 4 pts with grade (Gr) 1 and 3 with Gr 2. ICANS was observed in 1 pt (6.2%) at Gr 2. There were no Gr 3 or Gr 4 CRS or ICANS. Median time to CRS was 6.5 days (range, 0-12); the 1 ICANS event occurred on day 12. One pt (CLL) developed Gr 3 temporary neuropathic pain which, in the absence of other explanation, was attributed to the CAR-T. No pts had tumor lysis syndrome or Gr 3-4 infections. Thrombocytopenia (Gr 3-4: 19%) and neutropenia (Gr 3-4: 94%) were common but there were no bleeding complications, and the rate of febrile neutropenia was 19%. Overall response (ORR) was 94% (15/16) with complete response (CR) rate of 62% (10/16). In FL pts (n =12), ORR was 92% (11/12) and CR rate was 75% (9/12). Among FL pts who received DL 3 or 4, the CR rate was 86%. The CLL pt had a PET-negative CR and undetectable measurable residual disease in peripheral blood and bone marrow by flow cytometry (10 -4) (uMRD4) on day 28. The pt with DLBCL achieved a partial response (PR) on day 28 and a repeat PET on day ~ 90 showed continued improvement but still indicating a PR. Among pts who achieved a CR, only one pt (FL) relapsed after 9 months. All other CRs are ongoing (range: 3-18 months). CAR-T persistence was lost at day 95 in 1 pt who had progression and proceeded to other anti-lymphoma treatment; 2 other patients lost CAR-T engraftment by day 181 and 201 with B cell recovery. All other patients continue to have detectable CAR-T cells as of last follow-up (max 13 months post-infusion). Conclusion: Treatment with MB-106 shows a favorable safety profile with no Gr 3 or Gr 4 CRS or ICANS. In addition, we observed a high rate of ORR and CR with ongoing CRs and high rate of CAR-T persistence. Enrollment is currently ongoing; data will be updated at the time of presentation. Figure 1 Figure 1. Disclosures Shadman: Mustang Bio, Celgene, Bristol Myers Squibb, Pharmacyclics, Gilead, Genentech, Abbvie, TG Therapeutics, Beigene, AstraZeneca, Sunesis, Atara Biotherapeutics, GenMab: Research Funding; Abbvie, Genentech, AstraZeneca, Sound Biologics, Pharmacyclics, Beigene, Bristol Myers Squibb, Morphosys, TG Therapeutics, Innate Pharma, Kite Pharma, Adaptive Biotechnologies, Epizyme, Eli Lilly, Adaptimmune , Mustang Bio and Atara Biotherapeutics: Consultancy. Yeung: Merck,Celgene: Consultancy. Ujjani: ACDT: Honoraria; Gilead: Honoraria; TG Therapeutics: Honoraria; Janssen: Consultancy; Epizyme: Consultancy, Membership on an entity's Board of Directors or advisory committees; Atara Bio: Consultancy; Loxo: Research Funding; Adaptive Biotechnologies: Research Funding; Kite, a Gilead Company: Honoraria; AstraZeneca: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; AbbVie: Consultancy, Research Funding; Pharmacyclics: Consultancy, Research Funding. Dezube: Mustang Bio: Current Employment, Current holder of individual stocks in a privately-held company. Poh: Acrotech: Honoraria; Incyte: Research Funding; Morphosys: Consultancy. Chapuis: Karkinos Therapeutics: Other: Ownership; Lonza: Other: Intellectual Property; Cullian: Other: Intellectual Property; TScan Therapeutics, Inc.: Consultancy, Other: Ownership; SignalOne Bio: Consultancy, Other: Ownership; Bluebird bio: Other: Intellectual Property; Juno therapeutics: Other: Intellectual Property; Adapyive Biotechnologies Corporation: Other: Ownership/Intellectual Property; Pfizer: Other: Intellectual Property; Affini-T: Other: Ownership; Ridgeline: Consultancy; BioNTech: Consultancy. Green: Seagen Inc.: Research Funding; bristol myers squibb: Membership on an entity's Board of Directors or advisory committees, Patents & Royalties, Research Funding; Cellectar Biosciences: Research Funding; GSK: Membership on an entity's Board of Directors or advisory committees; Janssen Biotech: Membership on an entity's Board of Directors or advisory committees, Research Funding; Juno Therapeutics: Patents & Royalties, Research Funding; Legend Biotech: Consultancy; Neoleukin Therapeutics: Membership on an entity's Board of Directors or advisory committees; Seattle Genetics: Membership on an entity's Board of Directors or advisory committees, Research Funding; SpringWorks Therapeutics: Research Funding. Cowan: Abbvie: Consultancy, Research Funding; Harpoon: Research Funding; Janssen: Consultancy, Research Funding; Sanofi Aventis: Consultancy, Research Funding; Bristol Myers Squibb: Research Funding; Nektar: Research Funding; GSK: Consultancy; Secura Bio: Consultancy; Cellectar: Consultancy. Cassaday: Amgen: Consultancy, Research Funding; Servier: Research Funding; Vanda Pharmaceuticals: Research Funding; Pfizer: Consultancy, Research Funding; Kite/Gilead: Consultancy, Honoraria, Research Funding; Pepromene Bio: Membership on an entity's Board of Directors or advisory committees; Merck: Research Funding. Kiem: Homology Medicines: Consultancy; VOR Biopharma: Consultancy; Ensoma Inc.: Consultancy, Current holder of individual stocks in a privately-held company. Gauthier: Janssen: Membership on an entity's Board of Directors or advisory committees; Multerra Bio: Consultancy; Legend Biotech: Membership on an entity's Board of Directors or advisory committees; Larvol: Consultancy; JMP: Consultancy; Eusapharma: Consultancy. Turtle: T-CURX: Other: Scientific Advisory Board; Century Therapeutics: Consultancy, Other: Scientific Advisory Board; Arsenal Bio: Current holder of stock options in a privately-held company, Other: Scientific Advisory Board; Eureka Therapeutics: Current holder of stock options in a privately-held company, Other: Scientific Advisory Board; Nektar Therapeutics: Consultancy, Research Funding; Precision Biosciences: Current holder of stock options in a privately-held company, Other: Scientific Advisory Board; Caribou Biosciences: Consultancy, Current holder of stock options in a privately-held company, Other: Scientific Advisory Board; Juno Therapeutics/BMS: Patents & Royalties: Right to receive royalties from Fred Hutch for patents licensed to Juno Therapeutics, Research Funding; AstraZeneca: Consultancy, Research Funding; Myeloid Therapeutics: Current holder of stock options in a privately-held company, Other: Scientific Advisory Board; Asher Bio: Consultancy; Amgen: Consultancy; PACT Pharma: Consultancy; TCR2 Therapeutics: Research Funding; Allogene: Consultancy. Lynch: TG Therapeutics: Research Funding; Bayer: Research Funding; Incyte: Research Funding; Juno Therapetics: Research Funding; Morphosys: Consultancy; Genentech: Research Funding; SeaGen: Research Funding; Cyteir: Research Funding. Smith: Portola Pharmaceuticals: Research Funding; Acerta Pharma BV: Research Funding; ADC Therapeutics: Consultancy; Incyte Corporation: Research Funding; AstraZeneca: Consultancy, Research Funding; Incyte: Consultancy; Ayala (spouse): Research Funding; Merck Sharp & Dohme Corp: Research Funding; Bristol Myers Squibb (spouse): Research Funding; De Novo Biopharma: Research Funding; Ignyta (spouse): Research Funding; KITE pharm: Consultancy; Millenium/Takeda: Consultancy; Bayer: Research Funding; Karyopharm: Consultancy; Beigene: Consultancy, Research Funding; Genentech: Research Funding. Gopal: Gilead: Consultancy, Honoraria, Research Funding; Genetech: Consultancy, Honoraria, Research Funding; SeaGen: Consultancy, Honoraria, Research Funding; Astra-Zeneca: Research Funding; Bristol Meyers Squibb: Research Funding; Agios: Research Funding; MorphoSys: Honoraria; IGM Biosciences: Research Funding; ADC Therapeutics: Consultancy, Honoraria; Acrotech: Consultancy, Honoraria; Karyopharm: Consultancy, Honoraria; Merck: Consultancy, Honoraria, Research Funding; Kite: Consultancy, Honoraria; Servier: Consultancy, Honoraria; Nurix Inc: Consultancy, Honoraria; Takeda: Research Funding; Teva: Research Funding; I-Mab bio: Consultancy, Honoraria, Research Funding; Epizyme: Consultancy, Honoraria; Incyte: Honoraria; Beigene: Consultancy, Honoraria; Janssen: Consultancy, Honoraria, Research Funding; Cellectar: Consultancy, Honoraria. Maloney: BioLineRx, Juno, Celgene, Kite, a Gilead Company, Gilead, Novartis, and Pharmacyclics: Honoraria; A2 Biotherapeutics: Consultancy; Kite, a Gilead Company, Juno, and Celgene: Research Funding; Juno: Patents & Royalties; A2 Biotherapeutics: Divested equity in a private or publicly-traded company in the past 24 months. Till: Mustang Bio: Consultancy, Patents & Royalties, Research Funding.

Abstract: Purpose: Evaluate the safety, pharmacokinetic profile, pharmacodynamic effects, and antitumor activity of the first-in-class investigational NEDD8-activating enzyme (NAE) inhibitor pevonedistat (TAK-924/MLN4924) in patients with relapsed/refractory lymphoma or multiple myeloma. Experimental Design: Patients with relapsed/refractory myeloma (n = 17) or lymphoma (n = 27) received intravenous pevonedistat 25 to 147 mg/m2 on days 1, 2, 8, 9 (schedule A; n = 27) or 100 to 261 mg/m2 on days 1, 4, 8, 11 (schedule B; n = 17) of 21-day cycles. Results: Maximum tolerated doses were 110 mg/m2 (schedule A) and 196 mg/m2 (schedule B). Dose-limiting toxicities included febrile neutropenia, transaminase elevations, muscle cramps (schedule A), and thrombocytopenia (schedule B). Common adverse events included fatigue and nausea. Common grade ≥3 events were anemia (19%; schedule A), and neutropenia and pneumonia (12%; schedule B). Clinically significant myelosuppression was uncommon. There were no treatment-related deaths. Pevonedistat pharmacokinetics exhibited a biphasic disposition phase and approximate dose-proportional increases in systemic exposure. Consistent with the short mean elimination half-life of approximately 8.5 hours, little-to-no drug accumulation in plasma was seen after multiple dosing. Pharmacodynamic evidence of NAE inhibition included increased skin levels of CDT-1 and NRF-2 (substrates of NAE-dependent ubiquitin ligases), and increased NRF-2-regulated gene transcript levels in whole blood. Pevonedistat–NEDD8 adduct was detected in bone marrow aspirates, indicating pevonedistat target engagement in the bone marrow compartment. Three lymphoma patients had partial responses; 30 patients achieved stable disease. Conclusions: Pevonedistat demonstrated anticipated pharmacodynamic effects in the clinical setting, a tolerable safety profile, and some preliminary evidence that may be suggestive of the potential for activity in relapsed/refractory lymphoma. Clin Cancer Res; 22(1); 34–43. ©2015 AACR.

Abstract: This trial was conducted to determine the dose‐limiting toxicities ( DLT s) and maximum tolerated dose ( MTD ) of the first in class NEDD 8‐activating enzyme ( NAE ) inhibitor, pevonedistat, and to investigate pevonedistat pharmacokinetics and pharmacodynamics in patients with acute myeloid leukaemia ( AML ) and myelodysplastic syndromes ( MDS ). Pevonedistat was administered via a 60‐min intravenous infusion on days 1, 3 and 5 (schedule A, n  = 27), or days 1, 4, 8 and 11 (schedule B, n  = 26) every 21‐days. Dose escalation proceeded using a standard ‘3 + 3’ design. Responses were assessed according to published guidelines. The MTD for schedules A and B were 59 and 83 mg/m 2 , respectively. On schedule A, hepatotoxicity was dose limiting. Multi‐organ failure ( MOF ) was dose limiting on schedule B. The overall complete ( CR ) and partial ( PR ) response rate in patients treated at or below the MTD was 17% (4/23, 2 CR s, 2 PR s) for schedule A and 10% (2/19, 2 PR s) for schedule B. Pevonedistat plasma concentrations peaked after infusion followed by elimination in a biphasic pattern. Pharmacodynamic studies of biological correlates of NAE inhibition demonstrated target‐specific activity of pevonedistat. In conclusion, administration of the first‐in‐class agent, pevonedistat, was feasible in patients with MDS and AML and modest clinical activity was observed.

Abstract: Abstract 2801 Background: MLN4924 is an investigational inhibitor of Nedd8-activating enzyme (NAE), which plays an essential role in regulating the activity of the cullin-RING E3 ligases (CRLs). NAE controls the neddylation cascade that results in Nedd8 conjugation to the CRLs, which is required for ligase activity. NAE inhibition thus inhibits ubiquitination and proteasomal degradation of CRL substrates, which include proteins involved in cell-cycle regulation (p27), signal transduction (pIκBα), DNA replication (Cdt-1), stress response (Nrf-2), and other processes important to tumor cell growth and survival. In lymphoma cells, NAE inhibition with MLN4924 has been shown to result in apoptosis either through increased Cdt-1 levels, S-phase accumulation, and DNA re-replication, or via pIκBα stabilization and consequent NF-κB pathway inhibition. In vivo, MLN4924 treatment resulted in tumor growth inhibition and regressions in lymphoma xenograft models. This phase 1 dose-escalation study is the first investigation of MLN4924 in multiple myeloma (MM) and lymphoma patients. We have previously reported (Shah et al, ASH 2009) that the maximum tolerated dose (MTD) of MLN4924 on Schedule A of this study (days 1, 2, 8, and 9 of 21-day cycles) was 110 mg/m2, with dose-limiting toxicities (DLTs) including muscle cramps and febrile neutropenia. Analyses of peripheral blood mononuclear cells and skin biopsies indicated MLN4924 exerted the predicted pharmacodynamic (PD) effects in peripheral blood and skin, including inhibition of neddylated cullins and induction of pIκBα, Cdt-1, and Nrf-2. Two additional schedules of MLN4924 administration are now being investigated with the aim of increasing tolerability and the deliverable dose. Methods: Patients aged ≥18 years with ECOG performance status 0–2 and relapsed and/or refractory MM or lymphoma, including any B- or T-cell non-Hodgkin's lymphoma (NHL) and Hodgkin lymphoma (HL), following ≥2 prior lines of therapy were eligible. Primary objectives were to determine the MTD and safety profile of MLN4924 on the different dosing schedules, describe the pharmacokinetics (PK) and PD of MLN4924 in blood, and investigate PD effects in skin and tumor. Secondary objectives included evaluation of disease response. Patients received MLN4924 via a 60-minute intravenous infusion on either days 1, 4, 8, and 11 (Schedule B) or days 1 and 8 (Schedule C) of 21-day cycles for up to 12 months. Doses of 25–147 mg/m2 were investigated on Schedule A; for Schedules B and C, dose escalation started at the MTD of Schedule A, 110 mg/m2, and proceeded in 1.33-fold increments using a Bayesian continual reassessment method based on the occurrence of DLTs in cycle 1. The MTD was defined as the dose level closest to that predicted to result in a DLT rate of 25%. Adverse events (AEs) were graded using National Cancer Institute Common Terminology Criteria for Adverse Events version 3.0. Results: To date, 7 patients (5 male, median age 60 years [range 48–68]) have been enrolled to Schedule B, 2 each at 110, 147, and 196, and 1 at 261 mg/m2; 2 have MM and 5 lymphoma (2 diffuse large B-cell lymphoma [DLBCL] , 1 small lymphocytic lymphoma, 1 mantle cell lymphoma [MCL], 1 nodular sclerosis HL). Patients have received a median of 3 cycles (range 2–5) to date. A total of 7 patients (all male, median age 49 years [range 45–66] ) have been enrolled to Schedule C, 2 each at 110 and 147, and 3 at 196 mg/m2; 4 have MM and 3 lymphoma (1 follicular lymphoma [FL], 1 MCL, 1 nodular sclerosis HL). Median number of cycles received is 4 (range 1–7). No DLTs and no grade ≥3 AEs have been reported on either schedule to date. On Schedule B, only grade 1 dyspnea and myalgia (both n=2) have been reported in 〉 1 patient, with grade 1 diarrhea (n=3), constipation, fatigue, and nausea (each n=2) reported on Schedule C. PK data for the 110 mg/m2 cohorts of Schedules B and C are consistent with the lack of significant accumulation of MLN4924 in plasma shown on Schedule A. One patient with HL on Schedule A achieved a partial response; no responses have been reported to date on Schedules B and C though some heavily treated patients have demonstrated stable disease for 5 or more cycles (1 FL, 7 cycles; 1 DLBCL, 5 cycles; 1 MM, 5 cycles). Conclusion: Enrollment and dose escalation are proceeding on Schedules B and C (at doses above Schedule A MTD) to determine the MTD on each schedule; updated clinical data will be presented, together with data on the PK and PD of MLN4924, on these dosing schedules. Disclosures: Shah: Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Millennium Pharmaceuticals, Inc.: Research Funding. Off Label Use: Investigational agent in clinical development for the treatment of multiple myeloma and lymphoma. O'Connor:Millennium Pharmaceuticals, Inc.: Membership on an entity's Board of Directors or advisory committees, Research Funding. Jakubowiak:Millennium Pharmaceuticals, Inc.: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene: Consultancy, Honoraria; Centocor Ortho Biotech: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Exelixis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Bristol-Myers Squibb: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees. Smith:Millennium Pharmaceuticals, Inc.: Honoraria, Research Funding, Speakers Bureau. Orlowski:Celgene: Consultancy, Research Funding; Millennium Pharmaceuticals, Inc.: Consultancy, Research Funding. Mulligan:Millennium Pharmaceuticals: Employment. Smith:Millennium Pharmaceuticals, Inc.: Employment. Pickard:Millennium Pharmaceuticals, Inc.: Employment. Dezube:Millennium Pharmaceuticals: Employment, Equity Ownership. Lonial:Millennium Pharmaceuticals, Inc.: Consultancy, Research Funding; Celgene: Consultancy, Research Funding; BMS: Consultancy, Research Funding; Novartis: Consultancy, Research Funding; Onyx: Consultancy, Research Funding.

Abstract: Activation of the platelet-derived growth factor (PDGF) and c-kit receptors has been proposed as important in mediating the growth of AIDS-related Kaposi's sarcoma (KS). We investigated the response of KS to the PDGF receptor (PDGFR)/c-kit inhibitor, imatinib mesylate, and investigated the effect of this therapy on critical signal transduction intermediates. Patients and Methods Ten male patients with AIDS-related cutaneous KS, which progressed despite chemotherapy and/or highly active antiretroviral therapy, received imatinib mesylate administered orally, 300 mg twice daily. Clinical response was determined by serial tumor measurements. To determine biologic and histologic response, skin lesion biopsies were obtained at baseline and following 4 weeks of therapy. Results Five of 10 participants had a partial response by tumor measurements. Biopsies after 4 weeks of therapy demonstrated histologic regression in four of six patients. Four patients' tumor biopsies were assessable for immunohistochemistry end points pre- and post-therapy. These demonstrated inhibition of PDGFR and its downstream effector, extracellular receptor kinase, which is a member of the mitogen-activated protein kinase family. The most common adverse event was diarrhea, which led to dose reduction in six patients. Conclusion Imatinib mesylate administered orally twice daily for AIDS-related KS results in clinical and histologic regression of cutaneous KS lesions within 4 weeks. These promising results demonstrate that inhibition of the c-kit and/or PDGF receptors may represent an effective strategy for treating KS.

Abstract: NEDD8-activating enzyme (NAE) regulates the NEDD8 conjugation pathway, and is required for activity of the cullin-RING E3 ligases (CRLs). CRLs control proteasomal degradation of several substrates involved in cell-cycle regulation, signal transduction, DNA replication and stress response including proteins important for survival of AML cells. MLN4924, a first-in-class NAE inhibitor, has shown antitumor activity in preclinical AML models. This study evaluated safety and tolerability of MLN4924 given on multiple dosing schedules. A maximum tolerated dose (MTD) of 59 mg/m2 given on days 1, 3 and 5 of a 21-day cycle (schedule A) was previously reported (Erba et al, EHA 2011); complete responses were observed in 4/27 patients for this schedule (most common AE: diarrhea [44%], most common Gr ≥3 AE: febrile neutropenia [33%] ). Here we report on two additional schedules. Methods Adults with AML or MDS and good performance status received MLN4924 as a 60-min IV infusion on one of two schedules for up to 1 year or until disease progression. Schedule B patients received escalating doses of MLN4924 on days 1, 4, 8 and 11 every 21 days. Schedule E patients received a fixed dose of MLN4924 on days 1, 3 and 5 every 21 days. Adverse events (AEs) and responses were graded according to published guidelines. Serial blood samples were obtained during cycle 1 for pharmacokinetic (PK) and pharmacodynamic analyses. Results On schedule B: 26 patients were enrolled (77% male), median age was 70.5 yrs, 23 had AML and 3 had MDS (2 had advanced disease with marrow blasts exceeding 10%). Patients received MLN4924 at 83 (n=19), 110 (n=4), and 147 mg/m2 (n=3). On Schedule E: 16 patients (69% male) received 50 mg/m2 MLN4924, median age was 70.5 yrs, 14 AML and 2 MDS (1 with advanced disease). Three patients on schedule B had dose-limiting toxicities (DLTs): 1 patient at 110 mg/m2; orthostatic hypotension (Gr 3); 2 patients at 147 mg/m2; cardiac failure (Gr 4; n=1), fatal lactic acidosis, hypotension, gastrointestinal necrosis, acute renal failure and myocardial ischemia (each Gr 4; n=1). On schedule E, 2 patients had DLTs: morbilliform rash (Gr 3; n=1); and increased aspartate/alanine aminotransferases (Gr 2/3; n=1). Most common all-grade and Gr ≥3 AEs are shown in the table. The MTD for Schedule B was determined as 83 mg/m2. On schedules B/E, 3/2 patients received ≥4 cycles, 0/4 remain on treatment; discontinuations were due to progressive disease (11/10), AEs (8/0), and other reasons (7/2) respectively. In 17 patients treated at 83 mg/m2 on schedule B and 16 patients on schedule E, individual PK profiles showed a biphasic disposition phase following completion of the first infusion. MLN4924 plasma concentrations were detectable 24–48 hours (schedule B) and 24 hours (schedule E) post dosing. Schedule B geometric mean (%CV) Cmax was 1255 ng/mL (25.1%), AUC24hr was 3936 ng•h/mL (22.6%); schedule E values were Cmax of 669 ng/mL (24.4%) and AUC24hr of 2614 ng•h/mL (21.4%). Observed increases in mean Cmax and AUC24hr were dose-proportional between 50 and 83 mg/m2 after single dosing. Pharmacodynamic data demonstrated evidence of target and pathway inhibition for all patients on both schedules. On schedule B, of 20 response-evaluable patients (18 AML, 2 MDS), 2 (11%) AML patients had partial responses (PR), 13 (72%) had stable disease. On schedule E, of 12 response-evaluable patients (11 AML, 1 MDS), 1 (8%) AML patient had a PR, 7 (59%) maintained stable disease and the MDS patient (8%) had a response. Conclusions Both schedules appeared to be generally well tolerated and NAE inhibition with MLN4924 resulted in clinical activity in highly refractory/multiply relapsed patients. Based on safety and observed clinical activity across schedules, the recommended phase 2 dose for single agent MLN4924 in AML/MDS is 50 mg/m2 given on days 1, 3 and 5 of a 21-day cycle. A study of MLN4924 with azacitidine in treatment-naïve AML patients older than 60 years is ongoing (NCT01814826). Disclosures: Off Label Use: Investigational agent MLN4924 for the treatment of patients with AML and high-grade or low-grade MDS. Hua:Millennium: The Takeda Oncology Company: Employment. Blakemore:Millennium: The Takeda Oncology Company: Employment. Faessel:Millennium: The Takeda Oncology Company: Employment. Dezube:Millennium: The Takeda Oncology Company: Employment. Medeiros:Millennium: The Takeda Oncology Company: Research Funding.

Abstract: Purpose: To determine the dose-limiting toxicities (DLTs) and maximum tolerated dose (MTD) of the investigational NEDD8-activating enzyme (NAE) inhibitor pevonedistat (TAK-924/MLN4924) and to investigate pevonedistat pharmacokinetics and pharmacodynamics in patients with advanced nonhematologic malignancies. Experimental Design: Pevonedistat was administered via 60-minute intravenous infusion on days 1 to 5 (schedule A, n = 12), or days 1, 3, and 5 (schedules B, n = 17, and C, n = 19) of 21-day cycles. Schedule B included oral dexamethasone 8 mg before each pevonedistat dose. Dose escalation proceeded using a Bayesian continual reassessment method. Tumor response was assessed by RECIST 1.0. Results: Schedule A MTD was 50 mg/m2; based on the severity of observed hepatotoxicity, this schedule was discontinued. Schedules B and C MTDs were 50 and 67 mg/m2, respectively. DLTs on both these schedules included hyperbilirubinemia and elevated aspartate aminotransferase. There were no grade ≥3 treatment-related serious adverse events reported on schedules B or C. Twenty-three (74%) evaluable patients on schedules B and C had stable disease. Intermittent dexamethasone use did not significantly influence pevonedistat pharmacokinetics. NAE inhibition by pevonedistat was demonstrated in multiple tumor types via IHC detection of pevonedistat-NEDD8 adduct and accumulation of Cullin-RING ligase substrates CDT1 and NRF2 in tumor biopsies. Conclusions: Pevonedistat was generally well tolerated on a day 1, 3, 5 schedule every 3 weeks with an MTD between 50 mg/m2 and 67 mg/m2. DLTs were predominantly hepatic enzyme elevations. Pharmacodynamic studies demonstrated that pevonedistat inhibited NAE in tumors. Clinical trials are ongoing. Clin Cancer Res; 22(4); 847–57. ©2015 AACR.