Stewart, Keith

Abstract Table 1. Samples to p53 deletions p 53 deletion FISH aCGH FISH and aCGH MGUS 142 - - SMM 108 - - Newly diagnosed MM - 182 - Relapsed/refractory MM 62 156 19 HMCLs - 48 - Total 312 386 19 Background: Inactivation of p53 by mutation or allelic loss is a rare event in multiple myeloma (MM) at the time of disease diagnosis and believed to be more common in the late stages of the disease. Here we defined the prevalence of p53 deletions in monoclonal gammopathy of undetermined significance (MGUS), smoldering multiple myeloma (SMM), newly diagnosed MM, relapsed MM and human myeloma cell lines (HMCLs). Indirect mechanisms of p53 inactivation such as amplification of MDM2, or deletion of CDKN2A (p14ARF) were also investigated. Patients and Methods: A total of 631 MM samples and 48 HMCLs were analyzed for p53 abnormalities (Table 1) and compared with a cohort of plasma cell leukemia (PCL) previously published by us. Interphase fluorescence in situ hybridization (FISH) and highresolution array-based comparative genomic hybridization (aCGH) were used to detect p53 deletions. MDM2 amplification and p14ARF loss were evaluated by aCGH. Overall survival (OS) was estimated through Kaplan Meier method. Results: The prevalence of p53 deletions was 1.4%, 3.7%, 8.9%, 20% and 87.5% in MGUS, SMM, newly diagnosed MM, relapsed MM and HMCLs respectively (Figure 1). Of interest patients in first relapse showed a p53 deletion prevalence of 18% in comparison with 33% for patients in second relapse or more. We obtained p53 deletion status in 8 patients noted to have deletion at the time of relapse and in whom we had previous samples stored. In 7 of 8 cases deletions had been acquired (absent in the previous samples). The median OS for relapsed MM patients with or without p53 deletion were 4.2 months and 37.8 months respectively (p <0.001). MDM 2 amplification and p14ARF loss was detected in 0.4% and 2% of new diagnosed MM, 0.6% and 5.1% of relapsed MM and 2% and 29% of HMCLs respectively. Discussion: Emergence of p53 deletion/mutations denotes progression genetic events in MM. Importantly we show for the first time the overriding importance of p53 deletions as prognostic markers in relapsed MM. A molecular staging system that is based on the presence of p53 inactivation may be more powerful than classifying patients based on the loss of p53. Other abnormalities involving p53 pathway regulators like MDM2 gain and p14ARF loss are infrequent events in MM, even in advanced disease. Figure 1. Prevalence of p53 deletions Figure 1. Prevalence of p53 deletions

Abstract Background: The combination of lenalidomide and dexamethasone (Rev/Dex) has been shown to be a highly effective therapy for multiple myeloma (MM). Over half of the patients with newly diagnosed MM achieve a complete response with prolonged therapy. More recently, a phase III trial demonstrated improved survival with use of lenalidomide and low dose dexamethasone with one year survival in excess of 90%. We report the initial results from a phase II trial combining lenalidomide and low dose dexamethasone with cyclophosphamide (CRd) as initial therapy of newly diagnosed MM. Methods: The trial was initiated in July 2006 and completed the target accrual of 33 patients by July 2007. The treatment protocol consisted of lenalidomide given orally at a dose of 25 mg daily on days 1–21 of a 28-day cycle. Dexamethasone (dex) was given orally at a dose of 40 mg on days 1, 8, 15, and 22 of each cycle. Cyclophosphamide at a dose of 300 mg/m2 was given on days 1, 8, and 15 of each cycle. Patients also received an aspirin once daily as thromboprophylaxis. Response was defined as a decrease in serum monoclonal (M) protein by 50% or higher and a decrease in urine M protein by at least 90% or to a level less than 200 mg/24 hours, confirmed at least 4 weeks apart. Results: The median age was 63 years (range, 44–79). Eight patients (24%) had ISS stage III disease. At this time, 19 of the 33 patients are evaluable for confirmed responses (i.e., off-study or completed at least 4 cycles of therapy). Of these, 2 achieved VGPR and 13 had a partial response giving an overall response rate of 79%. The response rate was affected by 5 of 19 patients who went off study within three cycles due to toxicities [interstitial nephritis (1 pt), multiple grade 3 toxicities including infection (1 pt) atrial fibrillation and infection (1 pt)] or alternative treatment [no response and possible renal toxicity (1 pt) and progression at 4 cycles (1 pt)]. Overall, hematological toxicity was the most common with grade 4 toxicity seen in 6 patients (20%). Non-hematological grade 3 or higher toxicities included fatigue (4 pts), thrombosis (3 pts) and renal failure (2 pts). One patient with thrombosis came off study for other toxicities, and the other two continued on study with anticoagulation. Thirteen patients (43%) had dose reductions of both cyclophosphamide and lenalidomide, most commonly due to hematological toxicity. So far, 12 patients have gone off study, 6 went to stem cell transplant, 3 due to adverse events, 1 due to disease progression and 2 patients went to alternate treatment. Conclusions: CRd has excellent activity in newly diagnosed myeloma with an estimated overall response rate of 79%. Response evaluation of the entire 33 patients will be presented at the meeting. We believe that the initial use of a 300 mg/m2 dose of cyclophosphamide resulted in 5 of the first 19 pts experiencing early toxicity and withdrawal. As a result, an expansion of the current trial is evaluating lower doses of cyclophosphamide (300 mg fixed dose). Full analysis of this study will be needed to determine if CRd can improve outcome compared to Rd.

Abstract Introduction. The NCIC CTG is conducting phase II testing to establish the tolerability and estimate the efficacy of combining lenalidomide (L) + melphalan (M) over multiple cycles for previously untreated patients with multiple myeloma who are ineligible for stem cell transplantation. We report the data from the preliminary safety phase of this trial. Methods. The MY.11 trial was initially designed as a randomized phase II test of M 9 mg/m2 given on days 1–4 (M9) plus either L 10 mg (L10) or 20 mg given on days 1–21 of a 28 day cycle. Primary prophylaxis with G-CSF was not included, but use of G-CSF for established neutropenia was permitted; our intent was to determine dose levels that could be given independently of G-CSF. A dose attenuation schedule was developed for neutropenia and/or thrombocytopenia that was severe and occurred during the administration of L or was persistent and caused a delay in the next treatment cycle. A hematologic dose limiting toxicity (H-DLT) was defined as the need for 2 dose attenuations of L or 1 dose attenuation of M. Prior to the randomized phase of the trial, a safety run-in phase testing M9+L10 in 6 patients was planned; closure of this arm was to occur if, during the first 3 treatment cycles, there were ≥ 3 H-DLTs or any non-hematologic serious adverse event (SAE) judged to be treatment related. Four of the planned 6 patients were entered; during their first 3 treatment cycles, each experienced a H-DLT and one died from sepsis. The study was therefore amended with the intent to conduct a randomized phase II test of M 4 mg/m2 days 1–4 plus L 15 mg days 1–21 (M4L15) and M 6 mg/m2 days 1–4 plus L 10 mg days 1–21 (M6L10). Prior to the randomized phase of testing, each regimen was tested in non-randomized safety run-ins that included 6 patients per arm. The same parameters as above for study arm closure were applied. If the M6L10 arm was closed, the trial would proceed to test M 5 mg/m2 days 1–4 and L 10 mg days 1–21 (M5L10). Results. Six patients were enrolled to M4L15: during their first 3 treatment cycles, 4 patients experienced H-DLTs related to severe or persistent grade 3–4 neutropenia and one other patient experienced an SAE related to hallucinations and multiple constitutional complaints. This arm was therefore closed to accrual. Six patients were enrolled to M6L10: during their first 3 treatment cycles, 3 patients experienced H-DLTs related to severe or persistent grade 3–4 neutropenia. One of these patients was hospitalized with pulmonary edema and another with febrile neutropenia. This arm was therefore closed and the MY.11 trial amended to proceed as a single-arm phase II testing M5L10. Conclusion. Although M + L holds promise as an effective combination for previously untreated myeloma patients, the regimen is associated with considerable myelosuppression. The efficacy of the combination when given at tolerable doses remains to be established.

Abstract From a high throughput RNAi screen of the human druggable genome targeting the KMS11 cell line, we identified the suppression of the vacuolar H+- ATPase (V-ATPase) family as cytotoxic to myeloma cells. In the screen, two oligos against each gene for the V-ATPase subunits ATP6V1A and ATP6V1B1 resulted in suppression of cell growth (50% and 60% inhibition of cell viability respectively). We further confirmed this result using both lentiviral shRNA knockdown and two small molecule inhibitors specific for V-ATPase. Silencing of ATP6V1A by lentiviral shRNA knock-down in KMS11 and in OPM1 myeloma cell lines caused 75–80% reduction of cell viability at 5 days post infection (measured by MTT assay). Consistent with this result, the V-ATPase specific inhibitors, bafilomycin A1 and REATA 203, both inhibited the growth of a genetically heterogeneous and standardized panel of 14 human myeloma cell lines in vitro with an IC50 ranging from 2.2 – 8.9 nM (mean 5.25 nM) for bafilomycin A1 and 46–1594 nM (mean 542.5 nM)) for REATA 203. We further demonstrated that patient samples (n=10) were sensitive to 20nM bafilomycin A1 which induced a mean of 58% of MM cells to undergo apoptosis (range 10% to 93%) after 24 hours of treatment. Similar to bafilomycin A1, treatment of primary patient-derived MM cells with 500 nM REATA 203 for 72 hours resulted in a mean 69% apoptosis (range 24% to 97%). In contrast, non-myeloma cells (the CD138- fractions of the bone marrow samples) were less sensitive - mean 9% apoptosis (range from 0% to 34%) under the same treatment conditions. Of high interest, however, unlike most drugs we have studied in pre-clinical myeloma models, the cytotoxicity induced by bafilomycin A1 in MM cell lines is abrogated by co-culture with patient bone marrow stromal cells but is not affected by IL-6 or IGF-1 treatment. Dexamethasone- or melphalan-resistant MM cell lines were also highly sensitive to both bafilomycin A1 and REATA 203. In a xenographic JJN3 mouse model, bafilomycin A1 suppresses and delays growth of tumor in a dose-dependent fashion. Gene expression analysis of normal-donor bone marrow plasma cells (n=19), primary tumor samples from MM patients (n=107) and normal somatic tissues demonstrates ubiquitous expression of most subunits of V-ATPase, however, some subunits are preferentially expressed in myeloma cells compared with normal plasma cells, including ATP6V1F (84% vs. 11%), ATP6V1E1 (29% vs. 5%), ATP6V1G2 (17% vs. 0%) and ATP6V0E 2 (36% vs. 16%). In conclusion, our data indicate that vacuolar H+-ATPase inhibitors are of interest as potential therapeutics for MM.

Abstract Bortezomib and related proteasome inhibitors have profound pre-clinical and clinical activity in Multiple Myeloma (MM). However, the critical molecular target(s) modulated by proteosome inhibition remains unknown. The overall response rate to bortezomib in relapsed and refractory MM patients is consistently 35%–50%, suggesting specific molecular targets or resistance mechanisms are inherent in patients. None of the known effects of bortezomib has been shown to correlate with clinical responses in patients or to explain the unique sensitivity of MM (as opposed to other malignancies) to these reagents. Therefore, in this study, we have conducted a small interfering RNA (siRNA) screen of the druggable genome in human myeloma cells to identify genes that modulate sensitivity to bortezomib. KMS11 human myeloma cells were reverse transfected with 13,984 synthetic short interfering RNAs (siRNA) against each of 6992 druggable targets (2 siRNA/gene with a single-siRNA per well/384 well format). At 24 hours post transfection, bortezomib was added at IC10, 30, 60 and 90. Cell viability was measured by ATP-dependent luminescence assay 72 hours post drug treatment. The resulting data from primary screening was evaluated for multiple quality control metrics and found to exceed all expected performance parameters with >99% global transfection efficiency, <0.25 CV values across the dataset with minimal plate-to-plate and set-to-set variation observed. From analysis of the primary screening data, a core panel of 320 (4.6% of druggable targets in library) bortezomib sensitizers were identified. 187 (58%) of these were further confirmed in a secondary screening experiment by multiple (2 to 4) independent siRNA. Among these 187 genes (2.6% of the genes investigated), some known targets, such as proteasome subunits are evident. Other genes belonging to the same functional gene families (e.g. TNF receptor family, Ras family, kinases, oncogenes and transporter proteins) or functioning within the same network of signal transduction (e.g. NF-kB, Wnt and estrogen receptor pathways) are evident. Our primary screen also identified genes that attenuate bortezomib-induced cytotoxicity. Members in this group include genes implicated in the negative regulation of cell proliferation and survival, such as NF-kB inhibitors, JNK pathway activators, tumor suppressors, apoptosis inducers and phosphatases. These studies enable dissection of the molecular mechanism of bortezomib in myeloma cells and may serve to point to biomarkers for response prediction and novel chemotherapeutic combination therapies.

17502 Background: CHIR-258 is an orally active small molecule receptor tyrosine kinase (RTK) inhibitor which has potent activity against multiple RTKs involved in tumor growth and angiogenesis (IC50 ≤13 nM for FGFR, VEGFR, PDGFR, C-KIT, and FLT3). Approximately 15% of newly diagnosed MM patients harbor a t(4;14) translocation, which results in ectopic expression of FGFR3 and MMSET and is associated with poor treatment outcome [0]and reduced survival. CHIR-258 inhibits proliferation and induces apoptosis in FGFR3-expressing MM tumor xenografts as well as FGFR3-expressing primary MM cells (Trudel et al, Blood 2005). CHIR-258 was synergistic with dexamethasone (dex) in vitro. Methods: CHIR-258 was administered once daily in a dose-escalating phase 1 study to patients with relapsed/refractory MM. Drug tolerability and safety, pharmacokinetics (PK) and pharmacodynamics (PD) were assessed. Results: as of December 2005, 9 total pts have been treated (50, 100, and 200mg qd cohorts) [6M, 3F; median age: 58 (range: 44–68), median of 3 prior therapies(range:1–7)]. Prior tx: 9/9 pts-thalidomide; 8/9 -Velcade; 8/9-transplant; 8/9- had progressed through dex. 4 of 9 pts treated were FGFR3+ and 4 pts remain on study (3 are FGFR3+). No CR or PR have been observed; stable disease has been noted. CHIR-258 has been generally well tolerated, and most drug related AEs were CTC grade 1 or 2, including: headache, dysgeusia, fatigue and anorexia. No neuropathy. One DLT has been observed to date: neutropenia (200mg cohort). Five pts had dex added to CHIR-258 of which 3 are ongoing (all FGFR3+). FGFR3+ pts receiving dex and CHIR-258 have a greater decline in urine and serum paraproteins (pp) vs CHIR-258 alone. Plasma exposure and Cmax increased proportionally across the doses. Conclusions: CHIR-258 is a novel inhibitor of RTKs involved in MM growth and proliferation. FGFR3+ pts have a more marked reduction in pp than FGFR3- pts. CHIR-258 has generally been well tolerated and further accrual continues. [Table: see text]

8003 Background: Carfilzomib is a novel, irreversible tetrapeptide proteasome inhibitor derived from the natural product epoxomicin. Carfilzomib was well tolerated in preclinical animal studies when administered on a two-week cycle, QDx5; proteasome inhibition one hour after dosing at the MTD was >80%. Two Phase I dose-escalation studies are ongoing, aimed at determining the safety, tolerability, and biological response to carfilzomib. Methods: Carfilzomib was administered according to two different dose-intensive schedules. In PX-171–001, carfilzomib was administered on a two week cycle, QDx5 with nine days rest; in PX-171–002, carfilzomib was administered on a four week cycle, QDx2 weekly for three weeks with 12 days rest. Eligible patients have multiple myeloma (MM), Non-Hodgkin's Lymphoma (NHL), Hodgkin's Disease (HD), or Waldenström's Macroglobulinemia (WM). Results: Thus far, a total of 54 subjects have been enrolled. Although the maximum tolerated dose (MTD) has not yet been identified on either study, responses seen on both protocols have established 11 and 15 mg/m2 as the minimal effective doses (MEDs) on PX-171–001 and 002, respectively. Of 3 patients with MM or WM treated on the 001 protocol, one MM patient has had a Partial Response (PR) and one WM patient had a Minimal Response (MR). Of 8 patients with MM treated on the 002 protocol, 3 patients have had PRs. 6 additional patients have had Stable Disease lasting longer than 6 months and symptomatic improvement has been seen in patients on both protocols. 11 subjects remain on study with stable disease or better. Proteasome inhibition in whole blood at the highest dose levels exceeded 80% one hour after the first dose. Carfilzomib has been well tolerated at doses at and above the MED thus far. There has been no incidence of painful peripheral neuropathy on either study. No dose-limiting toxicities (DLTs) have occurred on PX-171–001; one DLT (Gr 4 anemia and thrombocytopenia) was observed at 27 mg/m2 on PX-171–002. Conclusions: Thus far, intensive dosing with carfilzomib is well-tolerated at proteasome inhibition levels of more than 80%. Five responses have been observed, and several subjects have achieved long lasting SD and/or symptomatic improvement. No significant financial relationships to disclose.

Abstract Combination of carfilzomib with dexamethasone (Kd) is approved for use in relapsed and/or refractory multiple myeloma (RRMM), with carfilzomib administered twice weekly at 56 mg/m 2 (Kd56 BIW) or once weekly at 70 mg/m 2 (Kd70 QW). Post hoc cross‐trial comparisons were performed to compare efficacy and safety profiles of Kd70 QW vs Kd56 BIW dosing schedules using data from three trials of patients with RRMM: A.R.R.O.W., CHAMPION‐1, and ENDEAVOR. To select for comparable patient populations, side‐by‐side efficacy and safety comparisons were performed in subgroups of patients with 2‐3 prior lines of therapy who were not refractory to bortezomib. The overall response rate (ORR) was 69.9% (95% confidence interval [CI], 61.7‐77.2) for Kd70 QW and 72.4% (95% CI, 65.9‐78.2) for Kd56 BIW. Median progression‐free survival (PFS) was 12.1 months (95% CI, 8.4‐14.3) for Kd70 QW and 14.5 months (95% CI, 10.2—not evaluable) for Kd56 BIW. Frequency of grade ≥ 3 adverse events (AEs) was 67.6% for Kd70 QW and 85.3% for Kd56 BIW. Regression analyses (adjusting for prognostic factors) of all patients in the trials who received Kd70 QW vs Kd56 BIW estimated a PFS hazard ratio of 0.91 (95% CI, 0.69‐1.19; P = .47) and an ORR odds ratio of 1.12 (95% CI, 0.74‐1.69; P = .61). These results suggest that Kd70 QW has a comparable efficacy profile compared with Kd56 BIW and represents a convenient and well‐tolerated treatment for patients with RRMM.

Abstract Background: Single autologous stem cell transplant (ASCT) is considered the standard of care for younger multiple myeloma (MM) patients (pts). However, it is not curative and virtually all patients will ultimately relapse. As more options, such as biological therapy, are available to treat relapsed disease, the role of a second ASCT as salvage therapy is unclear. Method: Retrospective review of all MM pts who received a 2nd ASCT as salvage therapy at Princess Margaret Hospital. Results: Between February 1997 and June 2007, 61 MM pts received a second ASCT for relapsed MM at our institution. Median age was 56 yrs (range 35–71) at second transplant. 37 pts (61%) were male. Immunoglobulin subtype included IgG (36), IgA (14), light chain (6), nonsecretory (3), IgM(1) and IgD (1). Transplant conditioning regimen for first transplant was high dose melphalan (MEL) 140–200 mg/m2 in 51, MEL/etoposide(E)/TBI in 4, and MELl/TBI in 2. 2nd ASCT conditioning consisted of MEL + TBI +/− E in 2, MEL alone in 58 and Busulfan/Cyclophosphomide in 1. The median time from diagnosis to first transplant was 9.7 months (2.0–74.2). The median time to relapse after the first transplant was 32.6 months (9.7–85.6), with a median interval between transplants of 45.1 months (19.7– 115). Two transplant-related deaths occurred (3%). Response to first transplant was 4 CR (8%), 34 PR (68%), 2 MR (4%) and 10 SD (20%). Nineteen pts went on to maintenance therapy between transplants. Response to second transplant was 4 CR (8%), 41 PR (80%), 5 SD (10%) and 1 PD (2%). Median progression-free survival (PFS) was 15.8 months (0–63.8) while median overall survival (OS) was 4.2 years (0–7.0) after 2nd ASCT. The relationship between progression-free interval after 1st ASCT and the outcome of the 2nd ASCT is summarized Table 1. Patients can be stratified into two groups, those with a disease free interval of less than or greater than 24 months. The use of maintenance therapy did not differ between the two groups, 6 (40%) in patients with PFS ≤24 months and 13 (28%) in patients with PFS >24 months. Conclusions: 2nd ASCT is a feasible and safe salvage therapy in patients with relapsed MM. 2nd ASCT is effective in providing a median progression free survival of 1.25 years and median overall survival of 4.2 years after 2nd ASCT - results that compare favourably with other salvage approaches. Patients with a longer disease free interval after 1st ASCT experience a better progression free survival and overall survival after 2nd ASCT. It is reasonable, therefore, to consider a 2nd ASCT if the time to progression is greater than 2 years after first ASCT. Outcomes Based on Time to Progression Post 1st ASCT PFS post 1st ASCT # of pts median PFS post 2nd ASCT PFS post 2nd ASCT1 Median OS post 2nd ASCT OS post 2nd ASCT2 1 p< 0.005, 2 p< 0.05 ≤24 months 15 12.7 months 1 year: 46% 3.5 years 1 year: 85% 2 year: 11% 2 years: 76% 3 years 0% 3 years: 63% 4 years: 31% > 24 months 46 19.8 months 1 year: 74% 5.9 years 1 year: 91% 2 year: 45% 2 years: 82% 3 year: 31% 3 years: 65% 4 years: 55%

Abstract Introduction: Carfilzomib (CFZ) is a structurally- and mechanistically-novel proteasome inhibitor (PI) of the peptide epoxyketone class that exhibits a high level of selectivity for the unique N-terminal threonine active sites within the proteasome. CFZ is similar to bortezomib (BTZ; VELCADE®), in that it is a potent inhibitor of the chymotrypsin-like activity, but unlike BTZ, CFZ has shown minimal cross-reactivity with the other catalytic sites within the proteasome or across other protease classes. Preclinical human tumor xenograft models indicate that consecutive day (D1, D2) dosing resulting in 48 hours of proteasome suppression was superior to split dosing (D1, D4). Methods: This phase 1 sequential dose escalation trial tested an intensive proteasome inhibition schedule with CFZ administered as an intravenous push (IVP) daily (QD) for 5 consecutive days on a 14 day cycle. The doses administered ranged from 1.2 mg/m2 to 20 mg/m2. Multiple myeloma (MM), non-Hodgkin’s lymphoma (NHL) that included mantle cell lymphoma (MCL), Hodgkin’s disease (HD), or Waldenström’s macroglobulinemia (WM) were eligible if they had relapsed after 2 or more prior therapies. Results: A total of 29 subjects have been treated. The minimal effective dose (MED) was 11 mg/m2. A maximum of 80% proteasome inhibition was achieved in peripheral blood and mononuclear cells at ≥15 mg/m2. Five responses have occurred in 14 patients (6 MM, 3 MCL, 1 WM, 4 NHL) enrolled at ≥ the MED: 1 MM partial response (PR), 2 MM minimal responses (MR), 1 WM MR and one macroscopic CR in a patient with gastrointestinal MCL. Responses occurred in patients whose disease had failed therapy with BTZ, immunomodulatory agents, and stem cell transplant. Four NHL patients have had stable disease and remained on treatment for up to 7 months. Dose limiting toxicity reported at 20 mg/m2 included febrile neutropenia (reversible) and grade 4 thrombocytopenia. Grade 3 (25%) or grade 4 events (8%) were primarily hematologic events. Most withdrawals occurred due to the inconvenience of frequent visits, or progressive disease. Conclusions: This study demonstrates that intensive CFZ dosing leading to sustained proteasome inhibition is well tolerated. The selectivity of the epoxyketone class of PI may promote a favorable safety profile. Furthermore, antitumor responses in heavily pretreated patients suggest non-cross resistant activity. Phase 2 trials in MM and solid tumors are proceeding with an alternate IV schedule. An oral agent suitable for frequent dosing schedules is under development.