ALBERT

Description: Key Points A high frequency of RAS/RAF mutations and recurrent mutations in PDGFRA and JAK3 were found in relapsed multiple myeloma patients. Patients with NRAS, but not KRAS, mutation exhibited significantly reduced sensitivity to bortezomib but not high-dose dexamethasone.

Description: Abstract 1377 Background: MM is a plasma cell malignancy that remains generally incurable; however, there is significant inter-patient variation in the clinical course of MM and in survival, which is thought to relate, at least in part, to the biological heterogeneity of patients' tumors. At the molecular level, MM is sub-classified by chromosomal translocations, genetic mutations, and risk classifiers that integrate gene expression. Some of these genetic abnormalities have established associations with disease outcome in MM; for example, hyperdiploid patients have a better disease prognosis compared with non-hyperdiploid patients, and patients with a deletion of the p53 locus on chromosome 17 exhibit very poor clinical outcomes compared with patients who do not have this deletion. A better understanding of the molecular diversity of MM will likely inform therapeutic decision making and also identify additional intracellular targets for future drug development. A recent whole genome sequencing study of 38 MM patients described several somatic mutations that had not previously been described in MM or other cancers (Chapman et al, Nature 2011), as well as mutations in known cancer genes that had either not previously been reported in MM (BRAF), or that were observed at a higher frequency in MM than previously reported (KRAS, NRAS). The present study was conducted to confirm the prevalence of mutations in a panel of established cancer genes in tumor samples from patients with relapsed or refractory MM. Methods: Bone marrow aspirates were collected from 133 patients who participated in phase 2 (SUMMIT, CREST) and 3 (APEX) clinical studies of bortezomib for relapsed or refractory MM. Tumor DNA was amplified and screened for mutations in a panel of cancer genes using the MassARRAY®/Sequenom mass spectrometry-based methodology. This custom panel evaluates 514 known mutations in 43 distinct oncogenes and tumor suppressor genes. Mutations were identified with standard software and subsequently verified via manual inspection. Results: The most common mutations observed in MM tumor samples were in KRAS (n=32 [24.1%], 95% CI: 17.0–31.3) and NRAS (n=26 [19.5%], 95% CI: 12.8–26.3); for both genes, mutations in codon 61 were more common (47% and 85% for KRAS and NRAS, respectively) than mutations in codon 13, as previously described for MM (Chng et al, Leukemia 2008). Mutations in BRAF were detected in three patient samples (2.3%, 95% CI: 0–4.8). For all three genes, the mutation rate in this patient population was similar to that reported by Chapman et al (26.3%, 23.7%, and 4% for KRAS, NRAS, and BRAF, respectively). The frequency of mutations in KRAS and NRAS was similar in patients who had received one or more than one prior line of therapy, suggesting that these mutations arise early in the pathogenesis of MM and are not driven by treatment-exerted selection pressures. KRAS, NRAS, and BRAF mutations were mutually exclusive, consistent with their described biological roles in modulating a common signaling pathway. These data suggest that the RAS/RAF pathway is activated by mutation in 45.9% (95% CI: 37.0–54.3) of patients with relapsed or refractory MM. Mutations in a number of other genes, including PIK3CA, TP53, MET, PDGFRA, and JAK3 were detected in at least two patient tumor samples; several of these genes have not previously been reported to be mutated in MM. Conclusions: These data confirm the high prevalence of activating mutations in genes of the RAS/RAF pathway in patients with relapsed or refractory MM, and begin to shed light on additional mutations that may co-operate with or act independently of this key cellular signaling axis. Data on the co-occurrence of these mutations in patients with MM, and their association with clinical outcomes, will be presented. Disclosures: Mulligan: Millennium Pharmaceuticals, Inc.: Employment. Lichter:Millennium Pharmaceuticals, Inc: Employment. Di Bacco:Millennium Pharmaceuticals, Inc: Employment. Blakemore:Millennium Pharmaceuticals, Inc: Employment; Takeda Pharmaceuticals: Equity Ownership. Berger:Millennium Pharmaceuticals, Inc: Employment. Koenig:Millennium Pharmaceuticals, Inc: Employment. Bernard:Millennium Pharmaceuticals, Inc: Employment. Trepicchio:Millennium Pharmaceuticals, Inc: Employment. Li:Millennium Pharmaceuticals, Inc: Employment. Lonial:Bristol-Myers Squibb: Consultancy; Novartis: Consultancy; Celgene: Consultancy; Millennium Pharmaceuticals, Inc.: Consultancy; Onyx: Consultancy; Merck: Consultancy. Richardson:Millennium Pharmaceuticals, Inc.: Consultancy; Johnson & Johnson: Consultancy; Celgene: Consultancy. Anderson:Merck: Consultancy; Onyx: Consultancy; Novartis: Consultancy; Celgene: Consultancy; Millennium Pharmaceuticals, Inc.: Consultancy; Bristol-Myers Squibb: Consultancy; Actelion: Equity Ownership, Membership on an entity's Board of Directors or advisory committees. Sonneveld:Janssen: Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding; Millennium Pharmaceuticals, Inc.: Membership on an entity's Board of Directors or advisory committees, Research Funding; Onyx: Membership on an entity's Board of Directors or advisory committees, Research Funding. San Miguel:Celgene: 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; Millennium Pharmaceuticals, Inc: Honoraria, Membership on an entity's Board of Directors or advisory committees; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees. Esseltine:Millennium Pharmaceuticals, Inc.: Employment; Johnson & Johnson: Equity Ownership. Schu:Millennium Pharmaceuticals, Inc.: Employment.

Description: Background 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.