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Background New therapies are needed to manage the increasing incidence, severity, and high rate of recurrence of Clostridium difficile infection. Methods We performed a randomized, double-blind, placebo-controlled study of two neutralizing, fully human monoclonal antibodies against C. difficile toxins A (CDA1) and B (CDB1). The antibodies were administered together as a single infusion, each at a dose of 10 mg per kilogram of body weight, in patients with symptomatic C. difficile infection who were receiving either metronidazole or vancomycin. The primary outcome was laboratory-documented recurrence of infection during the 84 days after the administration of monoclonal antibodies or placebo. Results Among the 200 patients who were enrolled (101 in the antibody group and 99 in the placebo group), the rate of recurrence of C. difficile infection was lower among patients treated with monoclonal antibodies (7% vs. 25%; 95% confidence interval, 7 to 29; P

PurposeNineteen patients with high-risk resected stage III and IV melanoma were immunized with three tumor antigen epitope peptides from gp100, MART-1, and tyrosinase emulsified with adjuvant Montanide ISA 51 and received a fully human anti-cytotoxic T-lymphocyte antigen-4 (anti–CTLA-4) monoclonal antibody MDX-010. Each of three cohorts received escalating doses of antibody with vaccine primarily to evaluate the toxicities and maximum-tolerated dose (MTD) of MDX-010 with vaccine. MDX-010 pharmacokinetics and immune responses were secondary end points.Patients and MethodsPeptide immunizations with MDX-010 were administered every 4 weeks for 6 months and then every 12 weeks for 6 months. A leukapheresis to obtain peripheral-blood mononuclear cells for immune analyses was performed before treatment and after the sixth vaccination. Patients were observed until relapse.ResultsGrade 3 gastrointestinal (GI) toxicity (diarrhea or abdominal pain) was observed in three patients in the highest dose cohort and one in the middle dose cohort who seemed to be autoimmune. That defined the MTD with vaccine on this schedule at 1 mg/kg. Of eight patients with evidence of autoimmunity, three have experienced disease relapse. Of 11 patients without autoimmune symptoms, nine have experienced disease relapse. Significant immune responses were measured by tetramer and enzyme-linked immunospot assays against gp100 and MART-1.ConclusionDose-related autoimmune adverse events, predominantly skin and GI toxicities, were reversible. Patients mounted an antigen-specific immune response to a peptide vaccine when combined with a human anti–CTLA-4 antibody.

3018 Background: Ipilimumab is a fully human monoclonal antibody directed against cytotoxic T-lymphocyte antigen-4 (CTLA-4), a critical suppressor of antitumor immune activity. Previously presented...

9022 Background: Ipilimumab is a fully human monoclonal antibody targeting cytotoxic T-lymphocyte antigen-4 (CTLA-4) that gave durable complete/partial responses [CR/PR] and stable disease [SD]) in...

20004 Background: Ipilimumab is a fully human, anti-CTLA-4 monoclonal antibody that has been associated with complete and partial responses when administered as monotherapy or in combination with a...

8523 Background: Ipilimumab, a fully human monoclonal antibody that blocks cytotoxic T-lymphocyte antigen-4 (CTLA-4), enhances antitumor immune responses resulting in durable objective responses. In this study we examined the efficacy and safety of different ipilimumab preparations and regimens in patients with unresectable metastatic melanoma. Methods: In this study (MDX010–15), 34 patients received either 2.8 or 5 mg/kg transfectoma- or 3 mg/kg hybridoma-derived ipilimumab on days 1, 57 and 85. Additionally, 30 patients received single doses of 7.5 (6 pts), 10 (7 pts), 15 (6 pts) or 20 mg/kg (11 pts) transfectoma-derived ipilimumab. Once single doses up to 20 mg/kg were found to be well tolerated, 24 additional patients were given up to 4 doses of 10 mg/kg ipilimumab on days 1, 22, 43 and 64. Complete or partial responses (CR, PR), stable disease (SD) and adverse events (AEs) were monitored. Results: 1 CR, 3 PRs and 10 durable SDs were confirmed in 88 treated patients at the time of analysis. ORs were durable (∼29+, 34, 38+ and 39+ weeks [w]) and ongoing in 3 patients at study completion. PR in 1 patient was observed after ∼18.5w and developed to an ongoing CR at ∼51w. In another, SD for ∼16w preceded a ∼30w+ PR. Durable SD ranged from ∼21 to 79+w and is ongoing in 4 patients. Patients with OR or SD had immune-related AEs including rash, pruritis (G1/2), diarrhea (G1/2/3) or colitis (G2). AEs were severe in 27 patients, and considered ipilimumab-related (mostly G3/G4 colitis and diarrhea) in 9 (10% of all treated patients). Conclusions: Preliminary results suggest ipilimumab is generally safe and well tolerated. Late-onset ORs can occur, sometimes preceded by months of SD. ORs and SDs tend to be durable. Drug-related AEs of an immune nature are probably related to the biologic effects of ipilimumab, and are similar to those reported previously. No obvious dose relationship to AEs has been seen to date. [Table: see text]

8525 Background: Ipilimumab, a fully human monoclonal antibody that blocks cytotoxic T-lymphocyte antigen-4 (CTLA-4), enhances immune responses to tumor-associated antigens resulting in durable objective responses (OR). This abstract describes the kinetics of response after ipilimumab treatment. Methods: 5 studies (2 complete; 3 ongoing) in 269 treated patients with stage III/IV melanoma were reviewed and analyzed to determine the kinetics and duration of response after ipilimumab. Patients received ipilimumab alone or with dacarbazine, IL-2 or gp100 peptide vaccine. Ipilimumab doses ranged from 0.3–10mg/kg/dose (single or multiple). Complete and partial response (CR, PR), stable and progressive disease (SD, PD) were evaluated. Results: 41 patients (15%) had a confirmed OR at analysis. CR and PR was of late onset in some patients and occurred from ∼10–106 and ∼5–62 weeks (w) post-treatment initiation, respectively. In 28 patients onset of CR or PR occurred after >∼12w of treatment. PD preceded OR (without additional therapy) in 4 patients. In 2 patients, PD measured at ∼6w post-treatment initiation was followed by a PR at ∼12w. In 1 patient the PR changed to a CR at ∼24w and lasted for ∼188w+; the other patient maintained a PR for ∼17w. In the other 2 patients, PD at ∼12w was followed by SD at ∼17–20w and a PR after ∼30 and 62w; PRs in both patients lasted for ∼17 and 40w+, respectively. Duration of OR ranged from ∼6–187w+; ORs are ongoing in 25 patients. Late onset occurred irrespective of dose, regimen and therapeutic partner. Conclusions: Preliminary results suggest that ORs with ipilimumab may be later in onset and more durable than with traditional chemotherapy and may occur after progression. This late onset of effect likely reflects the immune-related mechanism of action of ipilimumab, and suggests that continued treatment/observation may be beneficial despite initial PD or SD. Acknowledgement: Dr. S. Rosenberg [Table: see text]

7525 Background: CTLA-4 is a negative regulator of cytotoxic T cell responses and may contribute to tumor escape from immune surveillance. MDX-010 is an IgG1κ fully human monoclonal antibody that blocks CTLA-4 function and is being studied in patients with metastatic melanoma and other malignancies. The current Phase II study was conducted to determine the safety and efficacy of MDX-010 when given alone or in combination with dacarbazine in chemotherapy and vaccine naive patients with unresectable metastatic melanoma. Dacarbazine is an FDA approved agent for metastatic melanoma with an approximate 10% objective response rate (ORR) but no demonstrable survival benefit. Long-term follow-up data on response duration and median progression-free survival for this Phase II study is now reported. Methods: Patients were randomized to receive MDX-010 at 3 mg/kg monthly x 4 (arm A; n=37) or MDX-010 in combination with dacarbazine 250 mg/m2 for 5 days monthly x 4 (arm B; n=35). Clinical response was measured by RECI...