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.