Citations

Abstract Lenalidomide is an orally active immunomodulatory drug effective in the treatment of multiple myeloma. We evaluated the toxicity and efficacy of MPR combination in a phase I/II study. Patients with newly diagnosed symptomatic multiple myeloma who were not candidates or refused stem cell transplantation were eligible. Treatment consisted of M and P on days 1 – 4 and R on days 1 – 21 in a 28 day cycle. All patients received aspirin 325 mg a day. Routine antibacterial prophylaxis was not used. Patients were accrued in cohorts of 3 at dose level 0 (M 5mg/m 2/d P 60 mg/m2/d R 10 mg/d) and level 1 (M 8mg/m2/d P 60 mg/m2/d R 10 mg/d). Patients were followed for at least 2 cycles to assess Dose Limiting Toxicity (DLT). G/GM-CSF use was not allowed in the first 2 cycles unless DLT had occurred. DLT was defined as occurrence of at least grade (G) 4 hematologic toxicity, G3 febrile neutropenia, or G 3 non-hematologic toxicity in the first two cycles. Failure to start the next cycle within 7 days of day 1 due to toxicity also constituted DLT. Results: 7 patients have been accrued (4 at dose level 0 {one patient had to be replaced} and 3 at dose level 1). 4 were males. ECOG performance status was 0 or1 (2 and 4 patients). Median age was 74 yrs, range 72 – 85. Between 3 and 10 cycles (median 4) have been administered at the time of this reporting. The following G3 or higher toxicities were encountered and considered at least possibly related to treatment: 2 patients at level 0 had G3 neutropenia. Of the three patients at dose level 1, there was 1 G4 neutropenia, 1 G4 thrombocytopenia, 1 G3 hyperglycemia and 1 G4 vascular access device related thrombosis. Responses were defined by EBMT/IBMTR criteria. 1 had a complete remission (after 3 cycles), 4 had partial remission (at least 50% reduction in monoclonal protein) and 1 had minimal response (after 3 cycles). Due to 3 DLT’s in dose level 1, dose level 0 was chosen for phase II of the study. Conclusion: M 5 mg/m2, P 60 mg/m2 and R 10 mg combination is well tolerated and appears effective in patients with multiple myeloma. These results are similar to the experience reported by Palumbo et al (Blood2005, 106(11):abst 785) although a stricter definition of DLT was used in our study. Escalation of R dose in combination with M 5 mg/m2, P 60 mg/m2 may be possible and improve responses. Updated data will be presented.

Abstract Abstract 2850 Myelofibrosis (MF), both primary myelofibrosis (PMF) and post essential thrombocytosis/polycythemia vera myelofibrosis (post ET/PV-MF), are chronic myeloproliferative neoplasms characterized by a progressive clinical course that leads to shortened survival. The heterogeneous nature of MF lends itself to a variable clinical course that commonly includes hepatosplenomegaly, constitutional symptoms, and progressive cytopenias. Medical therapy for myelofibrosis has been effective in palliation of common symptoms related to anemia, splenomegaly but allogeneic stem cell transplantation (ASCT) remains the only potentially curative therapeutic modality. The timing of ASCT, choice of conditioning regimen, patient selection and the impact of co-morbidities are critical to optimal use of this modality. We have retrospectively analyzed our experience for patients undergoing ASCT for primary and post ET/PV myelofibrosis at Mayo Clinic across all 3 sites: Scottsdale Arizona; Rochester, Minnesota; and Jacksonville, Florida. Methods: We conducted a retrospective review of all patients from 1992 to 2012 with PMF or post ET/PV-MF who underwent an ASCT at Mayo Clinic. This retrospective review included a waiver of informed consent and was approved by the Mayo Clinic Institutional Review Board. Patients that transformed to the MPN blast phase and individuals who underwent a second transplant for either relapse or graft failure were also included. Overall survival was estimated using Kaplan-Meier. Associations between prognostic factors and overall survival were assessed using Cox regression. Results: Baseline Patient Characteristics: Forty-eight patients (29 male) with a median age of 57 yrs (range 31–73) underwent ASCT. DIPSS-plus risk score was low in 2, intermediate 1 in 2, intermediate 2 in 9 and high in 35 patients. Disease type was PMF in 24, PV-MF in 10, ET-MF in 10, and MPN/MDS overlap in 4 pts. Eight patients evolved to the MPN-blast phase prior to transplant. JAK-2 mutation was positive in 27 patients and negative in 12 patients with JAK-2 status unknown in 9 patients. The median time from PV/ET to MF was 136 months (83–189 months) and from MF diagnosis to transplant was 59 months (3–144 months). All but 2 patients were red cell transfusion dependent prior to transplant (96%). Eight patients underwent splenectomy prior to transplant. Transplantation Characteristics: Patients who underwent ASCT received either myeloablative (MA, 13 pts) or reduced-intensity conditioning (RIC, 35 pts) regimen. The graft was from an unrelated donor in 22 pts and related donor in 26 pts with 44 being matched and 4 being mismatched. The myeloablative regimens included Bu/Cy, TBI/Cy, and Bu/Flu. The RIC regimens included flu/mel, Bu/Flu, FBM, and TBI/Flu. GVHD prophylaxis was with tacrolimus/MTX, CSA/MTX, and tacrolimus/MMF. Nineteen patients received ATG. Infectious disease prophylaxis, CMV monitoring, and additional supportive care measures were according to institutional guidelines. A majority of patients received peripheral blood stem cells with only 1 patient receiving bone marrow as the source of stem cells. Outcomes: The median time to neutrophil engraftment was 17.2 days. Two patients received a second transplant for relapsed disease. The incidence of graft failure was 10%. Graft versus host disease both acute and chronic occurred in 33 patients and 15 patients respectively. Day 100 overall survival was 92% and 2 year survival was 62% (95% CI 45–75%). There were no statistically significant associations between individual prognostic factors (DIPSS-plus classification, age, and HLA match) and survival. Conclusions: The Mayo Clinic national experience of ASCT for MF across our geographically diverse Cancer Center is encouraging. Our centers have transplanted 48 patients over the past 10 years with very favorable outcomes. Our results from a multi center practice are consistent with regards to survival, graft versus host disease, and types of transplants being performed compared to currently available published data from large single location transplant centers. This data helps confirm the prevailing knowledge that ASCT is a useful treatment. Disclosures: Mesa: Incyte: Research Funding; Lilly: Research Funding; Sanofi: Research Funding; NS Pharma: Research Funding; YM Bioscience: Research Funding.

Abstract Background: Triplet regimens combining a proteasome inhibitor, an immunomodulatory drug, and a steroid have been shown to be active and well tolerated in previously untreated MM pts. Extended treatment represents an alternative paradigm to induction followed by ASCT in this setting; however, agents for continuous therapy need to be convenient and well tolerated. The investigational agent ixazomib is the first oral proteasome inhibitor to be studied clinically. Phase 1 studies have indicated single-agent activity in relapsed/refractory MM and shown ixazomib to be well tolerated with a manageable safety profile, including limited peripheral neuropathy (PN) (Richardson PG et al, Blood 2014; Kumar SK, et al, Blood 2014). Weekly ixazomib plus lenalidomide-dexamethasone has been investigated in a phase 1/2 study in previously untreated MM pts (NCT01217957); treatment comprised triplet induction therapy followed by single-agent ixazomib maintenance therapy. Results of induction therapy have been previously reported (Kumar SK, et al, ASH 2012). Here we report phase 2 efficacy and safety data in pts receiving ixazomib maintenance. Methods: In phase 2, pts aged ≥18 yrs with measurable disease and no grade ≥2 PN received oral ixazomib 4.0 mg on d 1, 8, 15, lenalidomide 25 mg on d 1–21, and dexamethasone 40 mg on d 1, 8, 15, 22, for up to twelve 28-d induction cycles, followed by maintenance ixazomib on d 1, 8, 15 every 28 d until progression at the dose last tolerated during induction. Transplant-eligible pts could discontinue from study for ASCT after 6 cycles. The primary objective was CR+VGPR rate. Responses were assessed by IMWG criteria. Adverse events (AEs) were graded by NCI-CTCAE v4.02. Results: Fifty pts were enrolled in phase 2; 29 discontinued during induction (cycles 1–12), primarily to undergo ASCT (n=14) or due to AEs (n=6) or pt withdrawal (n=4). Twenty-one pts received ixazomib maintenance therapy (cycle ≥13); 13 (62%) were male, and median age was 68 (range 34–77) years. At data cut-off (June 11, 2014), pts had received a median of 27 treatment cycles (range 15–32), including both induction and maintenance, with a median treatment duration of 26.6 mos (range 13.4–29.6). Mean ixazomib relative dose intensity was 95% and 89% in the induction and maintenance phases, respectively. The mean ixazomib dose administered during maintenance was 3.6 mg weekly. At data cut-off, 11 (52%) pts remained on ixazomib maintenance. Among 49 evaluable phase 2 pts, 44 (90%) achieved ≥PR, including 29 (59%) ≥VGPR. All 21 pts who received ixazomib maintenance had responded to induction therapy. Overall best confirmed/unconfirmed responses in the 21 pts included ≥CR in 11 (52%, of which 4 [19%] were stringent CRs [sCR]), ≥near-CR in 13 (62%), and ≥VGPR in 15 (71%), plus 6 (29%) PR. Responses were rapid and improved during treatment. Median time to first response (≥PR) was 0.99 mos (range 0.92–5.78) and to best response was 7.46 mos (range 1.02–24.74); 33% of pts improved their response during maintenance, including 2 VGPR to near-CR, 3 VGPR to CR, 1 VGPR to sCR, and 1 CR to sCR. At data cut-off, median duration of response was 26.5 mos (range 5.6–26.6+). Among 15 pts achieving ≥VGPR, 5 (33%) had progressed; median duration of ≥VGPR was 23.0 mos (range 3.7–26.1+). All pts were alive after follow-up of 24.6–30.3 mos, including a median follow-up from start of maintenance of 16.9 mos (range 12.9–18.9). Ixazomib maintenance was well tolerated; 15 (71%) pts had drug-related AEs, with only 2 (10%) pts with grade 3 drug-related AEs (hypokalemia, thrombocytopenia) and no grade 4 AEs. The most common (>1 pt) grade 1–2 drug-related AEs were diarrhea (n=8, 38%), nausea, pain in extremity (each n=3, 14%), anemia, and headache (each n=2, 10%). No PN was reported. Serious AEs were reported in 3 (14%) pts during maintenance, including grade 3 acute myocardial infarction, grade 3 pneumonia, and grade 3 orthostatic hypotension; all were considered not related to treatment. Only 1 pt required an ixazomib dose reduction due to an AE (neuralgia). Conclusions: These data indicate that single-agent ixazomib maintenance for up to 1.5 yrs was feasible and generally well tolerated, improved responses following ixazomib-lenalidomide-dexamethasone induction, and contributed to durable responses (median >2 yrs) in previously untreated MM pts not undergoing ASCT. The results support the ongoing phase 3 trial of ixazomib in the maintenance setting (NCT02181413). Disclosures Kumar: Celgene: Consultancy, Research Funding; Millennium: The Takeda Oncology Co.: Consultancy, Research Funding; Onyx Pharmaceuticals: Consultancy, Research Funding; Sanofi-Aventis: Consultancy, Research Funding; Array BioPharma: Consultancy, Research Funding; Janssen: Consultancy, Research Funding; Skyline Diagnostics: Membership on an entity's Board of Directors or advisory committees. Off Label Use: Investigational proteasome inhibitor ixazomib in combination with lenalidomide and dexamethasone and as maintenance therapy for patients with previously untreated multiple myeloma.. Niesvizky:Onyx Pharmaceuticals: Consultancy, Honoraria, Research Funding, Speakers Bureau; Celgene: Consultancy, Honoraria, Research Funding, Speakers Bureau; Millennium: The Takeda Oncology Company: Consultancy, Honoraria, Research Funding, Speakers Bureau. Lonial:Millennium: The Takeda Oncology Company: Consultancy, Research Funding; Celgene: Consultancy, Research Funding; Novartis: Consultancy, Research Funding; Bristol-Myers Squibb: Consultancy, Research Funding; Onyx Pharmaceuticals: Consultancy, Research Funding. Laubach:Novartis: Research Funding; Onyx Pharmaceuticals: Research Funding. Hamadani:Millennium: The Takeda Oncology Company: Research Funding. Stewart:Takeda Pharmaceuticals International Co.: Research Funding; Sanofi: Consultancy; Array BioPharma: Consultancy; Bristol Myers Squibb: Consultancy; Celgene: Consultancy; Novartis: Consultancy. Hari:Celgene: Consultancy, Honoraria, Research Funding; Onyx: Consultancy, Honoraria, Research Funding; Millennium: The Takeda Oncology Co.: Consultancy, Honoraria, Research Funding; Spectrum: Consultancy, Honoraria, Research Funding; Sanofi: Research Funding. Vescio:Celgene: Speakers Bureau; Millennium: The Takeda Oncology Co.: Speakers Bureau; Onyx Pharmaceuticals: Speakers Bureau. Kaufman:Millennium: The Takeda Oncology Co.: Consultancy, Honoraria; Celgene: Consultancy, Honoraria, Research Funding; Novartis: Consultancy, Honoraria, Research Funding; Onyx: Consultancy, Honoraria, Research Funding; Janssen: Consultancy, Honoraria; Spectrum: Consultancy, Honoraria; Merck: Research Funding. Berg:Takeda Pharmaceuticals International Co.: Employment. Liao:Takeda Pharmaceuticals International Co.: Employment. Hui:Takeda Pharmaceuticals International Co.: Employment. Richardson:Millennium: The Takeda Oncology Co.: Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees.

Abstract Abstract 2965 Background: Alkylating agents have been the mainstay of multiple myeloma (MM) therapy for decades and despite introduction of several new therapies, it continues to play a significant role in its management as part of various drug combinations. While melphalan has been the most commonly used alkylator in MM, recent studies have suggested significant activity for bendamustine, a bifunctional alkylator. The combination of lenalidomide and melphalan has been associated with high response rates in relapse and newly diagnosed MM. Based on these promising results we designed a trial to evaluate the maximally tolerated dose of lenalidomide and bendamustine when used in combination as well as the efficacy of the combination in relapsed disease. Patients and Methods: Patients with relapsed MM and measurable disease were enrolled on this phase 1/2 trial provided they had not more than 4 prior lines of therapy for MM, had adequate performance status and organ and hematological function. Patients refractory to lenalidomide were allowed to enroll. The primary objectives were to (i) to determine the MTD of bendamustine and lenalidomide in combination with dexamethasone in subjects with relapsed MM (phase 1) and (ii) to evaluate the confirmed response rate of bendamustine in combination with lenalidomide and dexamethasone in patients with relapsed MM (phase 2). Bendamustine (B) was administered on days 1 and 2 of a 28-day cycle at doses of 50–100 mg/m2. Lenalidomide (R) was given days 1–21 at doses of 15–25 mg daily. Dexamethasone (D) was administered at 40 mg weekly. Dose escalation was done using a 3+3 design and MTD was defined as one dose level below that resulted in >=2 DLTS among 6 patients. The primary end point for this trial was the proportion of patients with confirmed hematologic response (sCR, CR, VGPR, or PR) over the first 6 cycles of treatment. Results: A total of 72 patients were accrued to this study from March 2010 to May 2012: 21 patients in phase 1 and 51 in phase 2. The 6 patients from the MTD dose level of phase 1 were also included in phase 2. The median age of all 72 patients was 62.1 (range, 40–86) and 57% were male. Majority (75%) of patients had previously been exposed to lenalidomide and 69% had prior exposure to bortezomib. Median # of prior therapies was 3 (range, 1–5) and 74% of patients had a prior autologous stem cell transplant. Patients have received a median of 4 cycles (range, 1–25), with 27 patients still continuing on active treatment. Disease progression led to study discontinuation in 22 (49%) and adverse events were the reason for discontinuation in 14 (31%). In phase I, two DLTs (Grade (Gr) 2 neuropathy and Gr 4 neutropenia) were seen at the highest dose level (100 mg/m2 B, 25 mg R), and the MTD was determined as 75 mg/m2 of B given days 1 and 2 and 25 mg of R days 1–21, along with D 40 mg weekly. Overall patients, 12/21 (57%) had a PR or better. In phase 2, 17 (40%) confirmed responses (>=PR) were seen among the 43 patients evaluable for response (received at least 6 cycles of treatment or have gone off study prior to 6 cycles); including 9 (21%) VGPR and 8 (19%) PR. An additional 5 patients had a minor response. Over all dose levels, a gr 3 or higher adverse event at least possibly attributed to the study was seen in 75% of patients. The most common toxicities were all hematological (thrombocytopenia and leukopenia), and most common non-hematological toxicity was infection. Prolonged time to recovery of blood counts was seen in a few patients, but majority of patients were able to tolerate the regimen with adequate dose reductions. Conclusion: The recommended dose of the combination for further studies is bendamustine at 75 mg/m2 days 1 and 2, lenalidomide 25 mg daily on days 1–21 and dexamethasone days 1, 8, 15, 22; with cycles repeated every 28 days. The regimen is well tolerated with hematological toxicity being the most common and manageable with dose reductions. The regimen is effective with high response rates and durable responses seen. Updated results with response rates and time to event analyses will be available for the entire cohort at the time of meeting. Disclosures: Kumar: Merck: Consultancy, Honoraria; Celgene: Research Funding; Millennium: Research Funding; Novartis: Research Funding; Cephalon: Research Funding; Genzyme: Research Funding. Krishnan:celgene: Consultancy, Speakers Bureau. Zimmerman:Celgene: Honoraria; Millennium: Honoraria; Novartis: Expert Testimony, Expert Testimony Other. Vij:Teva: Speakers Bureau; Celgene: Honoraria, Research Funding, Speakers Bureau; Millennium: Speakers Bureau; Onyx: Honoraria, Research Funding.

Abstract Background: Outcomes in multiple myeloma (MM) have improved significantly over the years but disparities in outcomes exist among MM patients (pts) belonging to different racial subgroups. Previous studies have explored healthcare access and utilization disparities for pts of different races as potential causes, but genomic differences, which could alter disease biology and clinical behavior, have not been studied. We utilized the MMRF CoMMpass database, which prospectively captures clinical and molecular characteristics of MM patients to explore race-based differences at the genomic level. Methods: The publically available CoMMpass trial database (data release version IA8) was utilized. Pts with race category of White (total n=698) and non-White (total n=223, comprising 129 Blacks, 19 Asians and 45 others) were analyzed for genomics including cytogenetics (fluorescent in situ hybridization; FISH), tumor diploidy (conventional karyotyping), gene expression profiling (GEP), gene copy number variations (CNV), gene single nucleotide variations (SNV) and genomic translocations analysis focused on genes from the FoundationOne Heme panel¨ (402 genes). GEP was considered significantly different between categories for more than or equal to a 2-fold change for a given gene (p<0.05). Categorical variables for FISH probes and diploidy status were compared by Chi-square or Fischer exact test, wherever applicable. Results: GEP clustering analysis uncovered 67 genes differentially expressed between Whites vs. non-Whites (Fig 1A). Baseline cytogenetics aberrations between both race cohorts showed statistically insignificant differences. Multiple cytogenetic abnormalities were seen most commonly in both race groups (~31%) with the distribution of others (in descending order) as such: Del13 > No abnormalities > t(11;14) > 1q amplification > Del17p or p53 > t(4;14) > Del1p > t(14;16) > t(14;20). Aneuploidy status showed insignificant differences between race groups with ~34% of patients from both groups having no aneuploidy. SNV data was present for 90% of Whites and 57% of non-Whites. Overall, 84% of genes had>1 SNV (84%), 2% translocations only and 14% had neither SNVs or translocations. SNVs were classified as Non-specific Non-Synonymous coding (NNSCs), Splice-site (SS) or Tier 1 (T1, codon deletion, insertion, frame-shift, etc.). A total of 880 NNSCs SNVs were observed: 670 in Whites across 227 genes, 210 in non-Whites across 120 genes. In whites, 57% of NNSC SNVs consisted of transition-type mutations and 43% as transversions. In non-Whites, transition mutations comprised 64% of all NNSC SNVs and transversions in the remaining 36%. A total of 38 SS SNVs were observed, 30 in Whites and 8 in non-Whites observed in 25 and 6 genes, respectively. In Whites, 57% of SS SNVs were transition type and remaining 43% were transversion. In non-Whites, an equal % of SS transition and transversion mutations were noted. A total of 240 T1 SNVs were noted; 182 in Whites seen in 82 genes; 58 in non-Whites seen 6 genes. In both Whites and non-Whites, frameshifts (41% in Whites, 47% in non-Whites) and stop-gained (46% in Whites, 45% in non-Whites) SNVs were most common. A total of 17 genes with>10 distinct SNVs were identified in Whites; 5 genes in non-Whites and 4 genes commonly seen in both cohorts (Fig 1B). In Whites, 17 genes were found to have translocations (intrachromosomal TRAF3 and PIK3R2 most common); in non-Whites, 5 genes had translocations (intrachromosomal CIC and EMSY most common). CNV analysis demonstrated 21 genes that were significantly altered with either copy number gain or loss between Whites vs. non-Whites (Fig 1C). Conclusions: We present the first race-based comprehensive genomic analysis utilizing the public interface of the CoMMpass trial. We discovered genomic differences between Whites and non-Whites at several levels including GEP, SNV and CNV, but not at the level of cytogenetics, which are in fact the most commonly performed clinical genomic analysis. Correlation of these variations with MM pt outcomes would be invaluable in understanding disease biology and hopefully mitigating some of the outcome disparities by pt race. As the database grows and becomes more enriched, separate analyses for Blacks, Asians and Hispanics would be attempted. Acknowledgments: We would like to thank the MMRF, Ms. Mary Derome and Dr. Jonathan Keats for providing scientific overview and technical support. Disclosures Fonseca: Millennium, a Takeda Company: Consultancy; Millennium, a Takeda Company: Consultancy; AMGEN: Consultancy; AMGEN: Consultancy; Patent: Patents & Royalties: Prognostication of MM based on genetic categorization of FISH of the disease; Patent: Patents & Royalties: Prognostication of MM based on genetic categorization of FISH of the disease; Patent Pending: Patents & Royalties: The use of calcium isotopes as biomarkers for bone metabolisms; Patent Pending: Patents & Royalties: The use of calcium isotopes as biomarkers for bone metabolisms; Celgene: Consultancy; BMS: Consultancy; Bayer: Consultancy; Novartis: Consultancy; Sanofi: Consultancy; Celgene: Consultancy; Janssen: Consultancy; Millennium, a Takeda Company: Consultancy; BMS: Consultancy; AMGEN: Consultancy; Bayer: Consultancy; Patent: Patents & Royalties: Prognostication of MM based on genetic categorization of FISH of the disease; Novartis: Consultancy; Patent Pending: Patents & Royalties: The use of calcium isotopes as biomarkers for bone metabolisms; Sanofi: Consultancy; Janssen: Consultancy; Millennium, a Takeda Company: Consultancy; AMGEN: Consultancy; Patent: Patents & Royalties: Prognostication of MM based on genetic categorization of FISH of the disease; Patent Pending: Patents & Royalties: The use of calcium isotopes as biomarkers for bone metabolisms. Ailawadhi:Takeda Oncology: Consultancy; Amgen Inc: Consultancy; Novartis: Consultancy; Pharmacyclics: Consultancy.

Abstract Introduction. In comparison toCLL, single agent clinical efficacy of venetoclax (a Bcl-2 inhibitor; Bcl-2i) in multiple myeloma (MM) has been modest (ORR of ~12%; Kumar et al ASCO 2016). Clinical experience to date unequivocally directs towards a combination strategy in MM for venetoclax. Our prior work has demonstrated that interaction between tumor and stromal cells upregulates phospho-Bcl-2 (pBcl-2, more stable than Bcl-2) which undermines activity of Bcl-2i. We also noted that this can be overcome using agents such as lenalidomide, which can impair the protective effect of stromal cells. Our goal in this investigation was to determine if the antitumor effect of lenalidomide/dexamethasone (Ld) regimen can be further optimized through leveraging the Bcl-2 targeting properties of venetoclax thereby sensitizing MM cells to enhanced lethality. Given the known effects of Ld on activating host immune effector cells, we hypothesized that immune mediated cytotoxicity (engaged by Ld) can be further enhanced through concurrent treatment with venetoclax. Data presented here provides preclinical rationale and proof-of-principle for clinical development of Bcl-2i in combination with Ld. Methodology. Malignant plasma cell cancer models (MM1.S, BCWM.1, KMS11) and stromal cell line (HS5) were used. Bcl-2 and pBcl-2 were determined by flow cytometry. Drug cytotoxicity was determined by MTS assay and/orAnnexin-V/PI staining. SCID mice were used for xenograft studies. Bcl-2 inhibitors (venetoclax; Bcl-2 specific inhibitor, AT-101; pan Bcl-2 inhibitor) as well asLd were purchased from commercial sources. Results. Tumor cell lines were treated with Bcl-2i for 24hrs and showed significant loss of viability (51 - 68%) and induction of apoptosis (~40%) in vitro. To replicate microenvironment conditions, we co-cultured tumor and stromal cells for 48hrs followed by treatment with Bcl-2i (1uM). Under these conditions, we noted a significant reduction in apoptosis (~50%) in Bcl-2i-treated cells indicating the protective effect of the stroma (Fig.1a). Under similar settings, we examined Bcl-2 species in tumor cells +/- stromal cells. The ratio of pBcl-2:Bcl-2 in tumor cells without stromal contact was 0.7, whereas, the ratio increased to 1.8 when tumor and stromal cells were cocultured suggesting increased pBcl-2 as a protective mechanism (Fig.1b,c). We then investigated the potential of Ld (1uM) +/- Bcl-2i to downregulate pBcl-2:Bcl-2 and whether this correlated with increased tumor lethality. While solo Bcl-2i treatment of tumor + stromal cells downregulated pBcl-2 and Bcl-2 (ratio 1.5), a marked reduction was noted in Ld + Bcl-2i treated tumor cells (ratio of 0.3). And this correlated with enhanced tumor cell apoptosis; analogous to that observed in tumor cells without stroma (Fig.1a and c). As these experiments indicated the triple combination to overcome protective effects of the stroma through decreasing bioavailability of pBcl-2 in vitro, we next validated these observations in a xenograft model. MM1.S cells were subcutaneously implanted in SCID mice with local tumor growth monitored by caliper measurement and systemic dissemination measured by Human-Ig lambda levels. DMSO-treated mice demonstrated tumors averaging ~410mm3 by Day 24 post-tumor implantation, whereas mice treated with Bcl-2i (35mg/kg QD, oral gavage) or Ld alone (Len 10mg/kg QD; Dex 0.5mg/kg QD, IP injection) showed tumors ~330mm3. In Ld + Bcl-2i- treated mice, tumor size was ~250mm3- significantly lower than DMSO (p<0.001) or Bcl-2i orLd group mice (p<0.054) (Fig.1d). A similar trend was seen when systemic Human-Ig-lambda was measured (Fig.1e). Notably, mice tolerated the triple combination treatment well; with no significant weight loss or other toxicities noted. Conclusions. Regulation of the Bcl-2 pathway is an important approach for controlling tumor cell proliferation; most recently validated with the approval of venetoclax for treatment of CLL. Herein we demonstrateLd as an attractive partner regimen to enhance the effects of not only Bcl-2i but also that ofLd in MM. Ongoing work is investigating the combination ofLd + venetoclax and preliminary in vitro results in venetoclax-insensitive MM cells (IC50 >5uM) show significant apoptosis induction with combination therapy (Fig.1f). Altogether our studies provide the rationale for clinical evaluation of this combination platform (Len/Dex + Bcl-2i). Disclosures Ailawadhi: Pharmacyclics: Consultancy; Novartis: Consultancy; Amgen Inc: Consultancy; Takeda Oncology: Consultancy.

Abstract Background: Donor cell chimerisms are tested at frequent intervals after allogeneic hematopoietic stem cell transplantation (alloHSCT). However, the predictive value of this testing in patients with myelofibrosis (MF) is not well-defined. In this study, our primary objective is to evaluate the correlation of day 30 and day 100 donor cell chimerism and overall survival (OS) in patients (pts) who undergo alloHSCT for MF. Methods: Charts were reviewed for pts who underwent alloHSCT for MF at Mayo Clinic in Arizona, Minnesota and Florida between January 2005 and December 2015. Patients who died within 30 days of alloHSCT were excluded. Chimerism studies were evaluated in the peripheral blood for CD3 and CD33 fractions at day +30 (D30) and day +100 (D100). Cut-off value of 100% and less than 100% was used because of limited variability below 100%. Standard statistical methods were used to compare continuous and categorical variables. The Kaplan-Meier method was used to provide survival curves. Results: Baseline characteristics: Sixty three consecutive patients who underwent alloHSCT for MF since January 2005 until December 2015, and had D30 and/or D100 chimerism studies available were included in the study. Of these, 24 (38%) were female. Median age at diagnosis was 56 years (range, 19 - 73 years) and median age at AHSCT was 58 years (range, 19 - 73 years). Dynamic International Prognostic Scoring System-Plus (DIPSS-Plus) risk category at the time of alloHSCT was high in 31 (49%), intermediate-2 in 30 (48%) and intermediate-1 in 2 (3%) pts. JAK2 V617F mutation status was available in 61 pts and was positive in 35 (57%) pts. Nineteen (30%) pts had been treated with a JAK2 inhibitor prior to alloHSCT. Fifty-two (83%) pts had at least grade-2 fibrosis in bone marrow at the time of HCT. Transplantation: Median time from diagnosis to AHSCT was 12.9 months (range, 2.3 - 248.2 months). Fifty-five (87%) received a reduced intensity conditioning (RIC) regimen while 8 (13%) received myeloablative conditioning regimen. Of these 55 pts, RIC regimens used were busulfan fludarabine based regimen in 15 (27%), fludarabine melphalan based regimen in 18 (33%) and fludarabine melphalan carmustine in 22 (40%) pts. Donor source was matched related in 30 (48 %), matched unrelated in 28 (44%), single-antigen mismatched related in 4 (6%) and mismatched unrelated in 1 (2%). Peripheral blood stem cells were used in all AHSCTs. Outcomes: Median follow-up was 24.4 months (range, 1.5 - 83.6 months). Amongst pts who had <100% donor chimerism at D30 in CD33 fraction, 2 had 90%, 1 had 80% and 2 had zero% donor chimerism. At D100, 1 pt had 95%, 1 had 90%, 1 had 60%, 2 had 5% and 1 had zero% donor chimerism. Eighteen out of 57 (32%) pts who had 100% donor chimerism in CD33 fraction at D30 had died at the time of analysis compared to 4 out of 5 (80%) patients with less than 100% (p=0.03). Eight out of 38 pts (21%) who had 100% donor chimerism in CD33 fraction at D100 died versus 3 out of 6 (50%) with less than 100% (p=0.12). There was no significant survival effect of CD3 chimerism (p values=0.68, 0.59). Of the 23 deaths that had occurred at the time of analysis, cause of death was disease progression or relapse in 8 (35%), graft versus host disease in 6 (26%), transplant related (sepsis / engraftment failure) in 5 (22%) and unrelated causes in 4 (17%). Survival analysis: As depicted in the Kaplan Meier curve (figure 1), median overall survival (OS) for pts with 100% donor chimerism in CD33 fraction at day 30 was not reached while for <100% donor chimerism was 16 months (p=0.04). Survival at 3 years for patients with 100% CD33 donor chimerism at D30 was 65% while it was 40% for pts with less than 100%. Also, survival at 3 years for patients with 100% CD33 donor chimerism at day 100 was 75% compared to 50% for patients with less than 100%. Conclusions: In our study, 100% donor chimerism in CD33 fraction is associated with improved survival after alloHSCT for MF compared to pts with less than 100%. Further understanding regarding the reason for this relationship is critical. Larger studies to replicate these results would be imperative to validate these findings. Disclosures Mesa: Incyte: Research Funding; Ariad: Consultancy; Promedior: Research Funding; Novartis: Consultancy; Celgene: Research Funding; Gilead: Research Funding; CTI Biopharma: Research Funding; Galena: Consultancy.

Abstract Background: We have previously reported on ethnic disparities in outcomes of multiple myeloma (MM) pts (pts) and shown that Hispanics have the shortest median overall survival (OS) and myeloma-specific survival (MMS) while Asians have the longest. Ethnic minorities are increasing in number in the United States (US) and have been historically underrepresented in population databases with limited follow up since the introduction of novel agents for MM. We did an updated analysis with longer follow up for ethnic minorities to explore the changes in outcomes by race and also explored MM incidence rates, not reported previously. Methods: Surveillance Epidemiology and End Results (SEER) 13 Registry data (1973-2013) for adult pts (>18 yr) with confirmed diagnosis of MM was utilized. To avoid bias of under representation of ethnic minorities, analysis was restricted to pts diagnosed in 1992 or later. Years of diagnosis were 1992-1995 (pre-stem cell transplant; SCT), 1996-2002 (after SCT but before novel therapeutics) and 2003-2013 (after introduction of novel therapeutics). Cases that received a diagnosis at death certificate/autopsy, without follow-up records, lacking documentation on age at diagnosis, sex, or race/ethnicity were excluded. Cox proportional hazards models were used to evaluate association between patient characteristics and survival. All statistical tests utilized the SAS software (v9.4) and were two-sided with a significance level of 0.05. Results: The final analysis included 68431 MM pts (37300 males; 55%, 31131 females; 45%). Age-group cohorts included: 18-44 yr (2519; 4%), 45-54 yr (8131; 12%), 55-64 yr (15416; 23%), 65-74 yr (20214; 30%), and ≥75 yr (22151; 32%). Mutually exclusive racial subgroups included: non-Hispanic White (NHW; 44618, 65%), non-Hispanic African-American (AA; 13164, 19%), non-Hispanic Asian/Pacific Islanders (API; 3570, 5%), Hispanic (H; 6759, 10%) and Native American (NA; 320, 0.5%). Trends in age-specific incidence rates were similar for all races but except the 20-24 yr group, were highest for AA and lowest for API. (Figure 1) Survival analysis showed that females had a better median OS (3.4 vs 3 yr; p<0.001) and MMS (4.7 vs 4.4 yr; p<0.001) than males. Age was an independent predictor of OS (p<0.001) with the median OS changing from 7.3 yr in 18-44 to 1.9 yr in ≥75 age group. Similar results were seen for age groups and MMS as well (p<0.001). During the three pre-specified time periods for year of diagnosis, both the median OS and MMS progressively improved (P<0.001) suggesting improved outcomes secondary to treatment advancements. H and AA had the worst median OS (3.1 yr) as compared to NHW and API (3.3 yr) (p<0.001) and H had the worst median MMS (4.3 yr) while API had the best (5.1 yr) (p<0.001). Survival analyses were performed for ≥75 age group separately since it was the largest and traditionally with worst outcomes. The difference in median OS by gender was still significant (p<0.001) but less pronounced (1.8 vs 1.9 yr) and was not significant for MMS (p=0.33). Due to less SCT utilization, no incremental OS or MMS benefit was seen prior to advent of novel agents but since 2003 the ≥75 group did have a small benefit for OS (2 vs 1.6 yr, p<0.001) and MMS (3 vs 2.3 yr, p<0.001). Race no longer predicted for a statistically significant OS difference (p=0.52) while for MMS, H continued to have the worst (2.5 yr) and NA the best (3.8 yr) outcome (p<0.001). 5-year relative survival rates (RSR) over time showed an incremental improvement in recent years for all racial groups except API ≥70 yr (Figure 2) with generally an increased incremental benefit for the <70 yr age group than the elderly. For majority of races no incremental benefit was seen in 5-yr RSR for ≥70 yr pts between 1992-1995 and 1996-2003 but improvement was seen in 2004-2013. Conclusions: In a fast changing US demographic mix, significant disparities for MM incidence and outcomes exist by race/ethnicity. As compared to our previous analyses, new trends have emerged with Whites having an improved median OS than AA while H continue to have the worst MMS and API the best. Differences in median OS among races are no longer significant in elderly pts. A modest benefit in OS is being seen for elderly pts since the advent of novel therapeutics. Studies of ethnic disparities are important for evaluating management needs of specific patient populations as well as optimal triaging of healthcare resources. Figure 1 Figure 1. Figure 2 Figure 2. Disclosures Kelly: Novartis: Consultancy, Speakers Bureau; Amgen: Consultancy, Membership on an entity's Board of Directors or advisory committees; Pharmacyclics: Consultancy, Speakers Bureau. Ailawadhi:Pharmacyclics: Consultancy; Novartis: Consultancy; Amgen Inc: Consultancy; Takeda Oncology: Consultancy.

Abstract Background: Pomalidomide has demonstrated excellent activity in patients with relapsed, lenalidomide refractory, multiple myeloma (MM). Between November 2007 and March 2012, we enrolled 285 patients with relapsed MM on 5 sequential phase 2 trials; patients received pomalidomide at 2mg or 4 mg daily with weekly dexamethasone (Pom/dex). The approved dose of pomalidomide is 4 mg for 21 of 28 days. We wished to compare efficacy, tolerability and long-term outcomes between cohorts treated with 2 mg or 4mg daily continuously and 4mg daily for 21/28 days. Methods: After excluding two ineligible patients, 283 patients with lenalidomide refractory, relapsed MM from 5 sequential cohorts were analyzed. These patients were divided into 3 groups: Group1 received Pom 2mg for 28/28 day cycle (N= 69), Group 2 received Pom 4 mg for 28/28 day cycle (N= 95) and Group 3 received Pom 4mg for 21/28 day cycle (N= 119). All patients received oral dexamethasone given 40 mg daily on days 1, 8, 15, and 22. Response was assessed by the IMWG Uniform Response criteria. All patients received aspirin 325 mg daily for DVT prophylaxis or full dose anticoagulation. Results: The median age was 63 years (32-85); 35% were female. The median time from diagnosis was 53 months and the median number of prior regimens was 4. 127 (46%) had high-risk molecular markers. Prior therapies (% received) included lenalidomide (100%), thalidomide (46%), bortezomib (78%), autologous stem cell transplant (71%), and allogeneic transplant (4%). The median follow-up is 16.4 months (3.2-64.4). Forty eight percent are alive and 26% remain progression free; 15 patients are continuing to receive treatment. Frequency of AEs by groups are shown in Table 1. The most notable difference is grade 3+ neutropenia seen in 39% of group 1 and 56% and 57% of groups 2 and 3. Confirmed responses of PR or better were seen in 29% (group1), 35% (group2) and 24% (group3). Median duration of response (DOR) was 14.1 months (group1), 14.5 months (group2) and 10.2 months (group3). Median PFS was 5.5 months (group1), 6.9 months (group2) and 4.3 months (group3). Although the dose level cohorts were sequential rather than randomized, we compared OS between the dose levels in an exploratory manner. There was no significant difference in OS between dose levels (p=0.26). Median overall survival (OS) was 16.6 months (group1), 21.9 months (group2) and 16.0 months (group3). Conclusions: Pom/dex is active and well tolerated even in heavily pretreated patients Responses are durable. Response rates and overall toxicity are similar between the 2 mg and 4 mg doses. Neutropenia is more common in those receiving doses of 4mg daily or for 21/28 days compared to those receiving 2 mg daily. Table 1. All Grades Grade 3+ 2mg 28 Day 4mg 28 Day 4mg 21 Day 2mg 28 Day 4mg 28 Day 4mg 21 Day Anemia 68% 58% 74% 14% 15% 27% Lymphopenia 22% 51% 11% 16% 32% 8% Neutropenia 71% 82% 77% 39% 57% 56% Thrombocytopenia 51% 61% 63% 10% 9% 23% Leukopenia 59% 77% 72% 26% 38% 39% Pneumonia 7% 11% 12% 6% 7% 11% Fatigue 51% 65% 60% 9% 5% 8% Neuropathy 28% 32% 28% 0% 3% 0% Elevated Blood Glucose 10% 21% 8% 4% 6% 3% Pneumonitis 3% 2% 3% 3% 1% 1% VTE (Thrombosis) 3% 3% 3% 1% 3% 3% Secondary Malignancy 0% 2% 1% 0% 2% 1% Figure1. Kaplan Meier Overall Survival Curves Figure1. Kaplan Meier Overall Survival Curves Disclosures Lacy: Celgene: Research Funding. Fonseca:Medtronic, Otsuka, Celgene, Genzyme, BMS, Lilly, Onyx, Binding Site, Millennium, AMGEN: Consultancy, patent for the prognostication of MM based on genetic categorization of the disease. He also has sponsored research from Cylene and Onyx Other, Research Funding. Bergsagel:Novartis: Research Funding; Constellation Pharmaceutical: Research Funding; OncoEthix: Research Funding; MundiPharma: Research Funding. Stewart:Novartis: Consultancy; Celgene: Consultancy; Bristol Myers Squibb: Consultancy; Array BioPharma: Consultancy; Sanofi: Consultancy; Takeda Pharmaceuticals International Co.: Research Funding. Reeder:Millennium, Celgene, Novartis: Research Funding. Mikhael:Onyx: Research Funding; Celgene: Research Funding; Sanofi: Research Funding; Novartis: Research Funding.

Abstract Background Chronic lymphocytic leukemia (CLL) is characterized by the accumulation of clonal B cells in the peripheral blood, bone marrow, lymph nodes, and spleen. This is due to a combined effect of deferred apoptosis with slow, but persistent proliferation of malignant cells. In CLL, tumor-sustaining homeostasis is critically maintained by the ubiquitin proteasome system. The proteasome mediates degradation of various transcription factors such as TP53 as well as upholding a balance between the anti and pro apoptotic proteins of the BCL2 family. Previous studies have demonstrated that the clinical course of the disease is negatively associated with malfunctioning apoptotic pathways that result in increased levels of BCL2. Thus, identification and correction of defects that affect programmed cell death offer therapeutic vantage to reset and engage cell death pathways in CLL. Aim Examination of the anti-CLL properties of the investigational agent MLN2238 (Millennium Pharmaceuticals, Inc., Cambridge, MA) and its ability to inhibit the proteasomal machinery; induce CLL cell death and downregulate BCL2. MLN2238 activity was also investigated in conjunction with anti-CLL therapies such as fludarabine and dexamethasone along with the BH3 mimetic BCL2 inhibitor, AT-101 (Ascenta Pharmaceuticals, Malvern, PA). Methods CLL cells with >90% CD19+ tumor population were obtained from 28 patients with a confirmed diagnosis of CLL. Proteasomal activity was measured using synthetic fluorogenic peptide substrates. Apoptosis was measured by annexin-v/PI staining, and mitochondrial membrane permeability (MOMP) was assessed using TMRM followed by flow cytometry. Protein profiles were ascertained by western blot. Results MLN2238 inhibited the chymotrypsin-like proteasomal activity by more than 90% (p<0.005) in all patient samples without altering PSMB5 protein levels. Moderate to minimal inhibitory effect on caspase-like and trypsin-like proteasomal activities, respectively, was also noted. CLL cells showed a concentration dependent decrease in viability in response to treatment with MLN2238 at an IC50 of 50 nM. MLN2238 treated cells underwent apoptosis in a dose dependent manner with a median dose effect (cell death) observed in 42% of cells at 25 nM (range 10% - 54%) and 60% of cells at a 50 nM concentration (range, 25% - 73%). PARP-1 and caspase-3 cleavage along with an increase in MOMP was also noted after CLL cells were treated with MLN2238; however, apoptosis was only partially blocked by the pan-caspase inhibitor z-VAD.fmk. BCL2 downregulation was dose-dependent and was observed as early as 12 hours. We sought to determine whether directly disrupting BCL2 function with AT-101 could enhance the anti-CLL effects of MLN2238. When used at sub-IC50 concentrations, AT1-10 synergized with MLN2238 to induce CLL cell death. Synergy was also observed when MLN2238 was paired with the cytotoxic agent fludarabine, whereas the combination of MLN2238 and dexamethasone resulted in additive anti-CLL activity. Conclusion While PI have made an important impact in various B cell cancers, their role in CLL has not been well established. We investigated preclinically, a novel PI and noted that targeting the proteasome with MLN2238 resulted in lethal events in CLL cells, which were further enhanced by disruption of the BCL2 prosurvival pathway. Moreover, proteasome disruption sensitized CLL cells to the cytotoxic effect of fludarabine, an important therapeutic in CLL. These data provides the mechanistic basis for evaluation of MLN2238 in CLL through rationale design of drug combination strategies based on CLL biology. We would like to acknowledge the Leukemia and Lymphoma Society (A.C.-K. is a Leukemia and Lymphoma Scholar in Clinical Research) for their ongoing support. We are also grateful to Mary Ella Mahoney Davidson (Millennium Pharmaceuticals) for providing logistical support. Disclosures: Foran: Celgene: Research Funding.