Citations

8504 Background: CFZ is a novel proteasome inhibitor of the epoxyketone class that exhibits a high level of proteasome selectivityand demonstrates antitumor activity in bortezomib (BTZ)-resistant MM pts in phase I studies. Methods: PX-171–003-A0 was an open-label, multicenter study that enrolled MM pts who relapsed from >2 prior therapies, failed BTZ and at least 1 immunomodulatory agent [thalidomide (THAL) or lenalidomide (LEN)], and were refractory to last treatment [progressing on or within 60 d of last therapy or <25% response to last therapy]. Pts received CFZ 20 mg/m2 IV d 1, 2, 8, 9, 15 and 16 every 28 d for up to 12 cycles (C). Clinical benefit response (CBR) was defined as MR or better. Results: 46 pts were enrolled, including 78% with progression on or within 60 d of last therapy and 22% with no response to last therapy. 39 pts completed at least 1 C of CFZ, had measurable M-protein, and were evaluable for response. Median prior therapies was 5 (range 2–15). 100% of pts received prior BTZ, 91% prior THAL, 89% prior LEN, and 83% prior stem cell transplant (SCT) and all had failed combinations including anthracyclines (80%) and/or alkylating agents (94%). Pts received a median of 3 C (range 1–12); 13 pts completed ≥6 C. CBR was 26% (10/39 eval pts), including 5 pts achieving PR and 5 pts achieving MR. 5 BTZ-refractory pts achieved MR or PR. Median TTP was 6.2 mo, the median DOR for the MR + PR was 7.4 mo. 8/10 pts achieved response during C1. 16 additional pts achieved SD for at least 6 wks. The most common adverse events were fatigue, anemia, thrombocytopenia, nausea, upper respiratory infection, increased creatinine and diarrhea. Peripheral neuropathy occured in < 10% of pts with 1 Gr 3 in a pt with pre-existing Gr 2. Conclusions: Single-agent CFZ achieved a TTP of > 6 mo in relapsed and refractory MM pts who failed available therapies. 26% of patients had at least an MR and median duration of >7 mo with this steroid- and anthracycline-sparing regimen. CFZ toxicities were manageable and importantly, exacerbation of pre-existing PN was rare. The study has been expanded to enroll an additional 250 pts in this unmet medical need population at an escalated dose, and treatment has been extended beyond a year. [Table: see text]

Abstract We generated eight multiple myeloma cell lines resistant to bortezomib; five acquired PSMB5 mutations. In 1,500 patients such mutations were rare clinically. To better understand disruption of proteasomes on multiple myeloma viability and drug sensitivity, we systematically deleted the major proteasome catalytic subunits. Multiple myeloma cells without PSMB5 were viable. Drug-resistant, PSMB5-mutated cell lines were resensitized to bortezomib by PSMB5 deletion, implying PSMB5 mutation is activating in its drug resistance function. In contrast, PSMB6 knockout was lethal to multiple myeloma cell lines. Depleting PSMB6 prevented splicing of the major catalytic subunits PSMB5, PSMB7, PSMB8, and PSMB10; however, PSMB6 engineered without splicing function or catalytic activity, also restored viability, inferring the contribution of PSMB6 to proteasome structure to be more important than functional activity. Supporting this, bortezomib sensitivity was restored in drug-resistant multiple myeloma cell lines by low level expression of mutated PSMB6 lacking splicing function. Loss of PSMB8 and PSMB9 was neither lethal nor restored bortezomib sensitivity. Significant codependency of PSMB5, PSMB6, and PSMB7 expression was observed. We demonstrated elevated levels of PSMB6 and 7, but not 8 and 9, in some, but not all, serial patient samples exposed to proteasome inhibitors. In summary, we show PSMB6 and PSMB7, but not PSMB5, to be essential for multiple myeloma cell survival, this dependency is structural and that upregulation or activating mutation of PSMB5, 6, and 7 confers proteasome inhibitor resistance, while depletion confers sensitivity. Implications: These findings support modulation of PSMB5, PSMB6, or PSMB7 expression as a new therapeutic strategy.

8542 Background: Clonal hematopoiesis of indeterminate potential (CHIP) is defined by the presence of leukemia-associated somatic mutations in clonally expanded hematopoietic stem cells with a VAF of ≥2%. CHIP has been associated with myeloid malignancies and increased all cause mortality largely from atherovascular disease. The prevalence and impact of CHIP in patients with myeloma (MM) is yet to be defined. Aims: Evaluate the prevalence and significance of CHIP in 101 lenalidomide exposed patients with multiple myeloma. Methods: 101 MM patients, the majority exposed to > 2 years of lenalidomide (Len), with stored mononuclear blood samples were identified for Next Generation Sequencing (NGS) using a panel encompassing 42 gene mutations associated with CHIP. Electronic medical records were reviewed and outcomes of secondary malignancy, macrocytosis, thrombosis and mortality were extracted. Results: Thirty of 101patients were found to have CHIP with the most frequent mutations: DNMT3A (12%), TET2 (5%), and TP53 (4%). One third of patients with CHIP had > 1 mutation (37%). At 68 months median follow up over a quarter of patients experienced thrombosis (31%) and 13% developed subsequent malignancy/premalignant condition including myelodysplastic syndrome (3%). There was no significant difference in age, gender, duration of Len prior to NGS testing, thrombosis complication, or survival in those with versus without a CHIP mutation. At last F/U 30% had died, 25% remained on therapy, 27% were on maintenance therapy and 11% were on observation alone. Conclusions: CHIP mutations are common in plasma cell neoplasms, with 30% of patients in this study retrospectively found to have CHIP mutations by NGS testing. CHIP mutations have been associated with cardiovascular events and malignancy development, however no associations were identified in this small study. Limitations to this study include small sample size, retrospective nature and duration of follow up. Further study of this very common finding in MM patients regarding timing of development and subsequent impact of these mutations could help risk stratify and inform therapy selection. [Table: see text]

e19136 Background: Patient reported side effect bother is needed to understand tolerability of cancer drugs. We examined whether increase in side effect bother from baseline to cycle 7 as measured by a single item (GP5) from the FACT-G, “I am bothered by side effects of treatment”, was associated with early treatment discontinuation (ETD) in a multiple myeloma (MM) trial. Methods: Data were drawn from the induction phase of ECOG ACRIN E1A06, a two arm, phase 3 trial conducted in patients with untreated MM. The induction phase occurred over twelve, 28-day cycles. GP5 was assessed at registration and cycle 7. ETD was defined as completion of less than 12 cycles of treatment. We tested whether increase in side effect bother on the GP5 from baseline to cycle 7 was associated with months to ETD in two ways. At each timepoint, GP5 was rated with these response options: “Not at all”, “A little bit”, “Somewhat”, “Quite a bit”, “Very Much”. First, we stratified Kaplan Meier curves by patients with versus without substantially increased side effect burden from registration to cycle 7 on the GP5, defined as an increase of > 2 response categories; Cox regression was used to calculate a hazard ratio. Second, we fit a joint model of the GP5 change trajectory on months to ETD that substituted the estimated slope of a longitudinal logistic regression model into the hazard function of a Cox model. In this model, GP5 was dichotomized as 0 = “Not at all/”A little bit”; 1 = “Somewhat”/ “Quite a bit”/ “Very Much”. Results: 159 patients were followed during induction for a median of 11 months (range: 0.2-16.0). 10 patients (6%) reported a substantial increase on GP5 from registration to cycle 7. After 16 months, these patients had a significantly higher hazard of ETD as estimated by Kaplan Meier methods: 40% experienced ETD vs. 24% of patients without substantial GP5 increase [hazard ratio (HR): 3.08 (95% CI: 1.18-8.02)]. In the joint model, the effect of GP5 on hazard of ETD was larger [HR: 9.56 (95% CI: 2.41-37.82)]. Conclusions: This study found initial evidence that increase in side effect bother as measured by the GP5 predicts ETD and may therefore reflect treatment intolerability in cancer drug trials. The effects found in this study will be tested for replication in additional ECOG-ACRIN trials with diverse designs, treatments, and cancer types. Clinical trial information: NCT00602641 .

e19132 Background: The Functional Assessment of Cancer Therapy–General has an item about patient tolerability of treatment: “I am bothered by side effects of treatment” (GP5). We examined the predictive value of this single item for early treatment discontinuation in clinical trials. Methods: GP5 level prior to protocol therapy (rated using a 5-point Likert scale) and treatment start/end dates and off treatment reason data at each treatment phase were drawn from five phase III clinical trials conducted by ECOG-ACRIN. In the present analysis, GP5 was dichotomized as 0 = “Not at all”/“A little bit” and 1 = “Somewhat”/“Quite a bit”/“Very Much”. Early treatment discontinuation was defined either as receiving less than protocol specified cycles of treatment when maximum cycles specified in the protocol (E1A06 induction, E1912 induction, E1609 induction, E1105 induction, E5103 adjuvant), analyzed using logistic regression via odds ratio [OR]), or treatment cessation for reasons other than progressive disease or death when treatment continued until progression or intolerability (E1A06 maintenance, E1912 maintenance, E1609 maintenance, E1105 maintenance), analyzed using Cox proportional hazard model via hazard ratio [HR]. Results: GP5 prior to treatment was significantly associated with early discontinuation of E1A06 maintenance, E1609 maintenance, E1912 maintenance, and E1912 induction. No significant association was found for other therapies examined in the study. Conclusions: High GP5 level prior to treatment is associated with higher likelihood of early treatment discontinuation in patients who have received previous treatment. The limited predictive value of GP5 for treatment naïve patients is more limited, serial on-treatment assessment should be considered in this setting. Clinical trial information: NCT00602641 . [Table: see text]

Abstract The identification of the t(4;14) translocation in Multiple Myeloma (MM) provided the first indication that fibroblast growth factor 3 (FGFR3) could act as an oncogene. Several studies have assessed the potential of FGFR3 as a drug target and have shown that inhibition of FGFRs using tyrosine kinase inhibitors induces cell death of FGFR3 expressing MM cells. To clarify the signaling pathways implicated in FGFR3 dependent myeloma, we assessed gene expression changes associated with treatment of MM cell lines with three known small molecule FGFR inhibitors, PD173074, SU5402 and a third novel compound using Human U133_Plus2 arrays. In addition to describing the unique pharmacogenomic signals of each drug in myeloma, 845 differentially expressed genes, common to all three FGFR3 inhibitors, were identified. Cell cycle, DNA replication and ATP binding proteins were the most common (47%) functional classes of genes effected. Further validation and refinement of this gene list was conducted using FGFR3 siRNA inhibition and FGF ligand induction. 120 genes were altered between FGFR3 RNAi and scrambled control and 892 were induced by FGF ligand. Ten genes were commonly identified as significantly regulated by all 4 FGFR3 inhibitors and induced in the opposing direction by ligand. Of these macrophage inflammatory protein (MIP)-1alpha, and dual specific phosphatase 6 (DUSP6) were positively regulative while ANXA9, CR2, AL531683, ZNF589, AW274468, FRMD3, LTB and WDR42A were negatively regulated by FGFR3 signaling. Validating our findings, a feedback loop between FGFR/ERK/MAP kinase activation and DUSP6 has previously been described in the literature. MIP-1alpha however was the most significantly altered (12 fold) on array, and MIP-1alpha regulation in response to FGFR3 pathway stimulation was confirmed by flow cytometry and Western blot. Mining of publicly available array datasets on 174 MM patients significantly associated MIP1-alpha with FGFR3 expression (p=0.01). Of note down-regulation of MIP-1alpha was not observed following FGFR3 inhibition in MM cells with RAS mutations. Based on these, and previous findings, we hypothesized that MIP-1alpha was regulated by the FGFR3/ERK/MAP kinase pathway. Indeed, inhibition of ERK in FGFR inhibitor resistant cells with RAS mutations also led to down regulation of MIP-1alpha. Because of the recognized role of MIP1-alpha (CCL3) in survival and proliferation of MM cells and in MM bone disease, our observations raise the possibility that pharmacological inhibition of MIP-1 alpha may hold therapeutic promise in t(4;14) MM and may serve as a biomarker for successful FGFR3 or RAS signaling inhibition.

Abstract GX15-070 is a small-molecule antagonist of the BH3-binding groove of the Bcl-2 family of proteins and can thus induce apoptosis by inhibiting the interaction between pro- and anti-apoptotic proteins. In addition, GX15-070 activates a cellular pathway, which leads to the activation of the pro-apoptotic BH3-only protein Bim, a natural cellular inhibitor of anti-apoptotic members. Together, the direct inhibition of anti-apoptotic Bcl-2 family proteins and the activation of pro-apoptotic Bim by GX15-070 can sensitize tumor cells to apoptosis. Bcl-2 family members, particularly Bcl-XL and Mcl-1 have been implicated in the survival of myeloma cells and may be responsible, in part, for drug resistance. Consequently, GX15-070 was tested against the MMRC 12 validation cell line panel, a panel of 12 standardized and annotated human myeloma cell lines (HMCLs). Western blots preformed on 8 HMCLs confirmed expression of Bcl-2, Mcl-1 and/or Bcl-XL. Basal levels of Bcl-2 and MCl-1 were relatively similar across all HMCLs studied whereas levels of Bcl-XL were variable GX15-070 inhibited the viability of all 12 myeloma cell lines as determined by MTT assay. The mean IC50 was 215 nM; range (6.4-678nM) and sensitivity did not correlate with level of Bcl-2, MCL-1 or Bcl-XL expression. On the other hand cytotoxicity to normal human blood lymphocytes, stroma and bone marrow CFUs was not observed at concentrations which were effectively cytotoxic to HMCL. Time course experiments demonstrate that apoptosis and cleavage of caspase 3 began by 12 hours and continued to increase over a 96 hour period. Co-culture with human bone marrow stroma cells (BMSCs) failed to protect HMCL from GX15-070 induced cytotoxicity. Similarly, potent MM growth factors, Interleukin 6 (IL-6) and Insulin like growth factor (IGF)-1 did not confer resistance to GX15-070. Of interest, overexpression of Bcl-2 has been shown to attenuate PS-341-induced cell death (Mitisades); however, the combination of PS-341 and GX15-070 did not reveal synergistic interaction in preliminary results. Studies looking at other drug combinations are planned. Finally, GX15-070 produced cytotoxic responses in the first primary myeloma sample tested with further testing ongoing. Mouse xenograft studies are also ongoing and will be presented. These studies indicate extensive pre-clinical activity of GX15-070 in multiple myeloma and set the stage for planned Phase II clinical trials.

Abstract Activation of NFkB has been noted in late B-cell malignancies, but no genetic basis for this activation has been shown except for rare mutations of the NFkB pathway in lymphoma and none have been described in MM. Bortezomib, highly tumoricidal in a subset of MM patients, inhibits NFkB suggesting it’s role as a therapeutic target. Here we show for the first time the critical importance of mutations that dysregulate this potential survival pathway in human myeloma cell lines (HMCL) and new diagnosis MM patients. We performed high-density oligonucleotide array CGH (Agilent 44k) on CD138+ selected MM cells from 68 patients and 42 unique HMCL. Initially we focused on small loci, bi-allelically deleted, as markers for inactivation of potential tumor suppressor genes. We next developed FISH probes for the identified loci to confirm the bi-allelic deletions seen by aCGH. We next sequenced all samples with monoallelic deletions, and additional unselected patients, and identified additional inactivating mutations. Multiple novel tumor suppressor genes (TSG) were identified and validated, whose loss of function (both in patients and HMCL) leads to activation of the non-canonical NFkB pathway including: TRAF2 (9q34), TRAF3 (14q32), BIRC2/BIRC3 (11q22) and CYLD (16q12). Functional studies showed that HMCL with deletion or mutations in these genes have markedly increased NFkB2 p52/p100 ratios relative to other HMCL (and for BIRC2/BIRC3 relative to an isogenic line that retains one copy of BIRC2/BIRC3), indicating genetic activation of the non-canonical NFkB pathway. Reintroduction of deleted TSG into HMCL inhibited cell growth and resulted in cell death (see data on abstract by J. Keats et al). We next focused our analysis (of combined aCGH and GEP data) on positive regulators of this pathway. Rare IgH translocations of NIK have recently been identified in MM. By aCGH we identified amplification and rearrangements of NIK. We identified dysregulated expression of TNF family receptors that activate the non-canonical pathway: CD40 (translocation), TACI (amplification) and LTBR. All of the HMCL with these mutations also showed increased NFkB2 p52/p100 ratios, consistent with activation of the non-canonical NFkB. These mutations correlate with a gene expression profile of NFkB activation that is detected in one half of patients. In summary, we have determined for the first time the genetic basis for constitutive NFkB activation - present in 19/42 HMCL, and we estimate in at least one quarter of newly diagnosed patients (approximately one half of those with evidence of NFkB activation by GEP). We propose a mechanism in which positive (TACI, CD40, LTBR) and negative regulators (TRAF2, TRAF3, BIRC2/BIRC3, CYLD) of the pathway converge on NIK to mediate the processing of NFKB2 p100 to p52. The preponderance of genetic evidence suggests that drugs that target the non-canonical NFkB pathway, will be most effective in treating the 50% of MM patients with NFkB activation.

Abstract Waldenström’s macroglobulinemia (WM) is an incurable low-grade lymphoproliferative disorder characterized by bone marrow (BM) infiltration of a clonal population of small B-lymphocytes, plasmacytoid lymphocytes and plasma cells that secrete monoclonal IgM antibody. Because it is difficult to obtain tumor metaphases for karyotype studies, few recurrent chromosomal abnormalities have been reported and the genetic basis of the disease remains poorly defined. Therefore, we performed a comprehensive high-resolution study to identify genomic abnormalities involved in WM pathogenesis. Fifty-seven WM patients were analyzed using a combination of array-based comparative genomic hybridization (aCGH)(N=42); gene expression profiling (GEP)(N=22), DNA sequencing (N=24) and cIgM-FISH (N=57). Agilent 244A and Affymetrix U133 platforms were used in the aCGH and GEP experiments, respectively. An NF-κB index was calculated from GEP data, as a surrogate marker of NF-κB transcription activity. NFKB2 sub cellular localization was determined by immunofluorescence staining. Overall, 83% of samples have aCGH defined chromosomal abnormalities, with a median of 3 abnormalities per patient (range 0 to 27). We identified 16 recurrent regions of copy number change found in &gt;5% (3 or more patients); 10 deleted and 6 amplified regions. The most common abnormality was the entire or partial deletion of 6q, identified in 40% of cases. Four nonoverlapped minimal deleted regions were identified on 6q (MDR1 to MDR4), each of them being present in at least 14 of 17 patients with the abnormality. Gain of 6p was the second most common abnormality (17%) and its presence was always concomitant with 6q loss. Other recurrent deletions were 13q14 (10%) and 7q22, 8p, 11q22-q23, 11q23-q24 and 17p11-p13 (7% each). Copy gains were identified as partial or entire gains of chromosomes 18 (17%), 4 (12%) and 3 (10%), 8q (10%) and Xq27.1-q28 (10%). Three patients had either homozygous deletions or LOH with mutations affecting both alleles of TRAF3 on 14q32. TRAF3 inactivation was correlated with an increased NF-kB transcriptional signature and it was associated with activation of the non-canonical NFkB pathway. Additionally, we identified the inactivation of TNFAIP3, another negative regulator of the NF-kB pathways, in one of 24 patients. Finally, interstitial deletions identified in 4 patients at 13q14 identified a 1.1 Mb MDR, including MIRN15A and MIRN16-1. These findings confirm that focal 13q14 deletion is not restrict to B-CLL and that the MIRN15A/MIRN16-1 abnormalities might be common to several indolent B-cell diseases. Overall, we identified TRAF3 and TNFAIP3 inactivation in 5.3% and 2.4%, respectively. To our knowledge, this is the first study showing the inactivation of bona fide tumor suppressor genes in WM patients. Furthermore, these genes are negative regulators of NF-kB signaling pathway, highlighting its biologic importance in sustaining and limiting growth in WM. Mutational activation of this pathway, which is normally activated by ligand-receptor interactions within the BM microenvironment, suggest a therapeutic role for inhibitors of NF-KB pathway activation in the treatment of WM.

Abstract Introduction: The NCIC CTG previously reported the results of a dose-finding trial testing the combination of Melphalan (M) and Lenalidomide (L) in previously untreated patients with multiple myeloma who were ineligible for stem cell transplantation because of older age and/or comorbidity (White, Blood2007; 110: 63a). Using a 28-day schedule, M (dose indicated as mg/m2/day given on days 1–4) and L (dose indicated in mg/day given on days 1–21) was associated with excess toxicity with the regimens M9L10, M4L15 and M6L10. We concluded that phase II testing of M5L10 was warranted and now report the results of this testing. Methods: Previously untreated symptomatic and consenting patients with tissue-confirmed plasmacytosis and a measurable M-protein were eligible provided that they had acceptable hematologic and biochemical laboratory parameters and no precluding comorbidities. Planned treatment consisted of M 5 mg/m2 days 1–4 and L 10 mg days 1–21, given every 28 days for 12 cycles. As our intent was to determine dose levels that could be given independently of G-CSF, primary prophylaxis with G-CSF was not included but use of G-CSF for established neutropenia was permitted. A hematologic dose limiting toxicity (H-DLT) was defined as the need for 2 dose attenuations of L or 1 dose attenuation of M occurring within the first 3 treatment cycles. Responses to treatment were classified using 1998 EBMT criteria and assessed after 2 and 6 cycles of therapy. Results: The intended sample size was 41 patients; 35 patients (1 ineligible) were enrolled before the study was closed due to observing a frequency of DLTs that surpassed predefined boundaries. Of the 34 eligible patients, median age was 73.4 yrs and ISS was stage I = 13, stage II = 11 and stage III = 10. Prior to study closure, 27 patients were evaluable for DLT; 7 (26%) did not experience a DLT. Among the remaining 20 (74%) patients, non-hematologic (N=2) and hematologic (N=18) DLTs requiring dose attenuations were seen within the first 3 treatment cycles; the H-DLTs included severe or prolonged neutropenia (N=11), thrombocytopenia (N=2) or both (N=5). One fatal serious adverse event was observed, this was due to a stroke. The other non-hematologic DLT was a cranial nerve III palsy which subsequently resolved. Responses after 2 cycles were evaluable in 21 patients and included partial response (PR) = 11, minimal response = 6, no change = 2 and progressive disease (PD) = 2. For those patients without PD after 2 cycles, responses after 6 cycles were evaluable in 8 and included PR = 6, stable response = 1 and PD = 1. Conclusion: Although M + L is an active combination for previously untreated myeloma patients, the regimen is associated with considerable myelosuppression. Without the routine use of GCSF, the doses used in the MY.11 study were not tolerable. Inability to use planned doses may have compromised the efficacy of the combination.