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Although outcomes have improved for patients (pts) with multiple myeloma (MM), relapsed/refractory MM remains associated with short survival and constitutes an unmet medical need. Glucocorticoids (GCs) are an important component of MM therapy; however, resistance is common. In preclinical models, interleukin-6 (IL-6) promotes the proliferation and survival of MM cells in the context of the bone marrow microenvironment and protects these cells from GC-induced apoptosis. Therefore, blocking IL-6 may disrupt resistance and restore sensitivity to GCs. Here, we report the final results from a Phase 2 open-label, non-randomized study that evaluated the safety and efficacy of siltuximab (S), a monoclonal antibody targeting soluble human IL-6, in combination with high-dose dexamethasone (D) in pts with relapsed and relapsed/refractory MM.Pts with measurable, secretory disease who had received at least 2 prior lines of therapy, one of which contained bortezomib, and progressed during or after their last line of treatment were eligible. Other key eligibility criteria included a creatinine clearance ≥20 mL/min, platelets ≥50,000/mm3, and neutrophils ≥1,000/mm3. S was administered 6 mg/kg IV on days 1 and 15 of a 28-day cycle and oral D 40mg once daily, on days 1–4, 9–12, and 17–20 for a max of 4 cycles; days 1–4 for subsequent cycles. The first 14 pts received S alone for the initial 1 to 2 cycles; 10 pts had D added for progressive disease post-Cycle 1 or suboptimal response post-Cycle 2. 39 subsequent pts received S+D concurrently as none of the first 14 pts achieved ≥PR while on S monotherapy. The primary endpoint was overall response rate (ORR, CR+PR) using EBMT criteria. Secondary endpoints were time to progression (TTP), progression-free survival (PFS), overall survival (OS), and incidence of AEs and SAEs.Forty-nine pts received S+D. The median age was 65 yrs (range 43–89) and 43% of pts were female. The median disease duration was 4 yrs (range 0.7–13.2). Pts were heavily pretreated, having received prior bortezomib (100%), steroids (100%), IMIDs (90%), alkylating agents (91%) and ASCT (65%). The median number of prior lines of therapy was 4 (range 2–9); 86% had disease that was refractory to the last prior line. Of the 44 pts with prior D exposure, 32 (73%) were refractory to the last D-containing regimen. The median duration of therapy was 4 cycles (99 days). Of the 47 pts evaluable for response, the ORR by EBMT criteria was 17% (0 CRs, 8 PRs); the ORR + minimal response (MR) rate was 23.4% (N=11). Using IMWG criteria, the ORR + MR rate was 27.7% (9 PRs, 4 MRs). Of the 11 pts with at least MR by EBMT criteria, 5 pts were refractory to the last D-containing regimen and 7 experienced less than MR on a prior D-containing regimen. The median duration of response was 5.9 months (181 days, 95% CI: 147, 365). Three pts had a long-lasting response of 9 months or more. For all 49 pts, the median PFS was 3.7 months (114 days, 95% CI: 84, 148) and median OS was 20.4 months (621 days, 95% CI: 347,984). AEs occurring in ≥25% of pts were thrombocytopenia, fatigue, anemia, abnormal hepatic function, neutropenia, diarrhea, peripheral edema, dyspnea and dizziness. 74% of pts experienced a grade ≥3 AE; the most frequent non-hematologic grade ≥3 AEs were fatigue (8%), abnormal hepatic function (8%), and pneumonia (6%). Grade 4 hematologic toxicities were thrombocytopenia (12%), neutropenia (4%) and anemia (2%). 25% of pts discontinued treatment due to an AE. Twenty (41%) of the 49 pts experienced ≥1 SAE. The most frequently occurring SAEs were pneumonia (8%), thrombocytopenia (6%), septic shock, anemia, and hemolytic anemia (4% each). Five pts died during the study; 3 due to progressive disease, 2 due to infection (nosocomial infection, septic shock).The combination of siltuximab with dexamethasone was well tolerated. Although the ORR was modest in this relapsed/refractory patient population, responses were seen in pts with MM refractory to prior dexamethasone-containing therapy, suggesting that siltuximab may be able to at least partially overcome dexamethasone resistance in some cases. Overall, these results provide a rationale for further studies of siltuximab in combination with dexamethasone-based MM therapy.Voorhees: MedImmune: Consultancy; Pfizer: Research Funding; Centocor Ortho Biotech: Research Funding; Celgene: Research Funding; Merck: Research Funding. Off Label Use: Siltuximab for the treatment of multiple myeloma. Manges:Centocor Ortho Biotech: Research Funding. Sonneveld:Millennium Pharmaceuticals: Consultancy, Research Funding; Celgene: Consultancy, Research Funding; Janssen: Consultancy, Research Funding; Onyx: Consultancy, Research Funding. Jagannath:Merck: Honoraria; Millennium Pharmaceuticals: Honoraria; Johnson and Johnson Pharmaceuticals: Consultancy; Celgene: Consultancy, Honoraria; Centocor Ortho Biotech: Research Funding. Somlo:Onyx: Consultancy; Millennium: Consultancy; Celgene: Consultancy, Speakers Bureau; Centocor Ortho Biotech: Research Funding. Krishnan:Celgene: Speakers Bureau; Millennium Pharmaceuticals: Speakers Bureau; Centocor Ortho Biotech: Research Funding. Lentzsch:Celgene: Consultancy, Research Funding; Onyx: Consultancy; Genzyme: Consultancy; Centocor Ortho Biotech: Research Funding. Frank:Centocor Ortho Biotech: Research Funding. Zweegman:Centocor Ortho Biotech: Research Funding. Wijermans:Centocor Ortho Biotech Research & Development: Research Funding. Rijnbeek:Ortho Biotech Oncology Research and Development: Employment. Qin:Johnson & Johnson Pharmaceutical Research & Development, LLC: Employment. Cornfeld:Ortho Biotech Oncology Research and Development: Employment. Xie:Ortho Biotech Oncology Research & Development: Employment. Thomas:Centocor Ortho Biotech: Research Funding; Millennium Pharmaceuticals: Research Funding; Celgene: Research Funding; Novartis: Research Funding; Immunomedics: Research Funding.

Abstract 3971

Niesvizky: Celgene: Consultancy, Research Funding, Speakers Bureau; Millennium Pharmaceuticals, Inc.: Consultancy, Research Funding, Speakers Bureau; Proteolix: Consultancy, Research Funding. Flinn:Millennium Pharmaceuticals, Inc.: Membership on an entity's Board of Directors or advisory committees, Research Funding. Rifkin:Millennium Pharmaceuticals, Inc: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Celgene: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Amgen: Speakers Bureau; Cephalon: Speakers Bureau. Gabrail:Millennium Pharmaceuticals, Inc: Research Funding. Phooshkooru:Millennium Pharmaceuticals, Inc: Consultancy, Honoraria. Charu:Millennium Pharmaceuticals, Inc: Consultancy, Honoraria, Research Funding. Corzo:Millennium Pharmaceuticals, Inc.: Employment. Neuwirth:Millennium Pharmaceuticals, Inc: Employment.

Abstract 129

Background: CNTO 328 is an anti-interleukin (IL)-6 chimeric monoclonal antibody demonstrated to have anti-myeloma activities in vitro. Because IL-6 signaling augments the anti-apoptotic heat shock protein response, a potential resistance mechanism for bortezomib, downregulation of IL-6 signaling may enhance bortezomib’s anti-myeloma activity. Pre-clinical studies have shown that this combination had an additive to synergistic effect in inducing apoptosis in IL-6-dependent and independent multiple myeloma cell lines. Methods: In this open-label, safety lead-in cohort of a pivotal phase II trial, bortezomib naïve patients with relapsed/refractory multiple myeloma received CNTO 328 at 6mg/kg IV every 2 weeks in combination with 1.3 mg/m2 bortezomib IV on days 1, 4, 8, and 11 every 3 weeks. Patients received a maximum of 4, 6-week treatment cycles, after which bortezomib was reduced to 4, once weekly doses in a 5-week maintenance cycle. Dexamethasone was added to the regimen at disease progression. Results: Twenty-one patients (median age 66, range 39–85) were treated with bortezomib + CNTO 328. The median number of prior lines of therapy was 2 (range 1–3); the median duration since diagnosis was 3.5 years (range 1–10). Eleven patients had received prior autologous stem cell transplantation; 8 patients had received prior IMiDs. Baseline β2M levels of >3.5mg/L were reported in 13 patients; median CRP was 2.21 mg/L (range 0.4 – 86.1). Utilizing EBMT criteria, 12 patients (57%) achieved either a complete response (CR) or partial response (PR): 3 CR, 9 PR (including 2 very good partial response [>90% reduction] and 1 unconfirmed due to discontinuation for renal insufficiency). Thirteen of twenty-one patients discontinued treatment: 5 due to disease progression, 7 adverse events (AEs), and 1 withdrawal of consent. The other 8 remain on treatment. The median number of CNTO 328 administrations was 11 (range 2–38). Median time to disease progression/death was 280 days (range 36–540+). Grade 3 and higher hematologic toxicity was common: neutropenia (15/21); thrombocytopenia (8/21); lymphopenia (6/21); leukopenia (5/21). Grade 3 and higher hematologic AEs considered to be possibly related to CNTO 328 included neutropenia (10/21), leukopenia (3/21), lymphopenia (2/21) and thrombocytopenia (1/21). Grade 3 and higher infections were reported in 5 patients (urinary tract, bacterial, and campylobacter infection, pneumococcal sepsis, and pneumonia, 1 case each, among which the urinary tract and campylobacter infections were considered to be possibly CNTO 328-related). Other common CNTO 328-related AEs (>15%) of any grade included diarrhea (5/21), fatigue (5/21), and hypercholesterolemia (4/21). No patients died during treatment. Dexamethasone was added to the treatment regimen for only 4/21 patients, and no conclusions regarding this treatment modification can be drawn at present. Conclusion: Treatment with CNTO 328 combined with bortezomib is a promising new regimen for the treatment of relapsed/refractory multiple myeloma. Enrollment in a larger phase 2 randomized trial with bortezomib and either CNTO 328 or placebo is now ongoing to explore its full potential.

Background: CNTO 328 is an anti-interleukin (IL)-6 chimeric monoclonal antibody demonstrated to have anti-myeloma activities in vitro. Because IL-6 signaling augments the anti-apoptotic heat shock protein response, a potential resistance mechanism for bortezomib, downregulation of IL-6 signaling may enhance bortezomib's anti-myeloma activity. Pre-clinical studies have shown that this combination had an additive to synergistic effect in inducing apoptosis in IL-6-dependent and independent multiple myeloma cell lines.

Background: Bortezomib represents a significant advance in the treatment of relapsed/refractory myeloma, but its efficacy is limited by a number of resistance mechanisms including activation of the anti-apoptotic heat shock protein (HSP) and stress response pathways. CNTO 328 is an anti-IL-6 chimeric monoclonal antibody shown to have anti - myeloma activities in vitro. Because IL-6 signaling augments the HSP response, downregulation of IL-6 signaling may enhance bortezomib’s clinical anti-myeloma activity. Pre-clinical studies demonstrated that this combination had an additive to synergistic effect in inducing apoptosis in IL-6-dependent and independent multiple myeloma cell lines (Voorhees et al., 2007, in press). Methods: In this safety lead-in cohort of a pivotal trial (clinicaltrials.gov), CNTO 328, 6 mg/kg, was administered by IV every 2 weeks in combination with bortezomib, 1.3 mg/m2, given by IV on days 1, 4, 8, and 11 every 3 weeks. Pateints received a maximum of four, 6-week treatment cycles, after which the bortezomib schedule was reduced to four, once weekly doses in a 5-week maintenance cycle. When disease progression was documented, oral dexamethasone was added at 20 mg and given on the day of, and day after each bortezomib infusion, for a maximum of two cycles. All later cycles included 20 mg dexamethasone given only on the day of bortezomib administration. Results: Preliminary results from the first 6 patients are available. Pateint characteristics included median age of 68 years; B2M > 3.0 mg/L, (n = 4 pateints); CRP > 3.0 mg/L (3); a median of 2 prior regimens (range 1 – 3), and prior bone marrow or peripheral blood stem cell transplantation in three patients. Using the EBMT response criteria, three patients achieved confirmed partial responses (PRs). Additionally, two patients had unconfirmed PRs. One patient discontinued prior to confirmation, while a follow up assessment for the other patient is pending. The median number of cycles administered was 3. Two of the patients ended treatment prematurely, 1 due to disease progression and 1 due to adverse events. The remaining 4 patients continue on study. Grade 3/4 adverse events (AEs) considered possibly related to CNTO 328 and bortezomib include neutropenia (2 patients), leukopenia (1), lymphopenia (1), and bloody diarrhea (1). Conclusion: Treatment with anti-IL-6 CNTO 328 in combination with bortezomib has been evaluated for safety and efficacy in the first 6 patients of an ongoing pivotal trial for the treatment of relapsed or refractory multiple myeloma. Initial activity observed with this combination is encouraging, and enrollment is continuing to explore its full potential.

Background: Bortezomib represents a significant advance in the treatment of relapsed/refractory myeloma, but its efficacy is limited by a number of resistance mechanisms including activation of the anti-apoptotic heat shock protein (HSP) and stress response pathways. CNTO 328 is an anti-IL-6 chimeric monoclonal antibody shown to have anti - myeloma activities in vitro. Because IL-6 signaling augments the HSP response, downregulation of IL-6 signaling may enhance bortezomib's clinical anti-myeloma activity. Pre-clinical studies demonstrated that this combination had an additive to synergistic effect in inducing apoptosis in IL-6-dependent and independent multiple myeloma cell lines (Voorhees et al., 2007, in press).