Phase I study of the CD40 agonist antibody CP-870,893 combined with carboplatin and paclitaxel in patients with advanced solid tumors.

CD40 is a cell-surface molecule that critically regulates immune responses. CP-870,893 is a fully human, CD40-specific agonist monoclonal antibody (mAb) exerting clinical antineoplastic activity. Here, the safety of CP-870,893 combined with carboplatin and paclitaxel was assessed in a Phase I study. Patients with advanced solid tumors received standard doses of paclitaxel and carboplatin on day 1 followed by either 0.1 mg/Kg or 0.2 mg/Kg CP-870,893 on day 3 (Schedule A) or day 8 (Schedule B), repeated every 21 d. The primary objective was to determine safety and maximum-tolerated dose (MTD) of CP-870,893. Secondary objectives included the evaluation of antitumor responses, pharmacokinetics and immune modulation. Thirty-two patients were treated with CP-870,893, 16 patients on each schedule. Two dose-limiting toxicities were observed (grade 3 cytokine release and transient ischemic attack), each at the 0.2 mg/Kg dose level, which was estimated to be the MTD. The most common treatment-related adverse event was fatigue (81%). Of 30 evaluable patients, 6 (20%) exhibited partial responses constituting best responses as defined by RECIST. Following CP-870,893 infusion, the peripheral blood manifested an acute depletion of B cells associated with upregulation of immune co-stimulatory molecules. T-cell numbers did not change significantly from baseline, but transient tumor-specific T-cell responses were observed in a small number of evaluable patients. The CD40 agonist mAb CP-870,893, given on either of two schedules in combination with paclitaxel and carboplatin, was safe for patients affected with advanced solid tumors. Biological and clinical responses were observed, providing a rationale for Phase II studies.

CD25 blockade depletes and selectively reprograms regulatory T cells in concert with immunotherapy in cancer patients.

Regulatory T cells (T(regs)) are key mediators of immune tolerance and feature prominently in cancer. Depletion of CD25(+) FoxP3(+) T(regs) in vivo may promote T cell cancer immunosurveillance, but no strategy to do so in humans while preserving immunity and preventing autoimmunity has been validated. We evaluated the Food and Drug Administration-approved CD25-blocking monoclonal antibody daclizumab with regard to human T(reg) survival and function. In vitro, daclizumab did not mediate antibody-dependent or complement-mediated cytotoxicity but rather resulted in the down-regulation of FoxP3 selectively among CD25(high) CD45RA(neg) T(regs). Moreover, daclizumab-treated CD45RA(neg) T(regs) lost suppressive function and regained the ability to produce interferon-γ, consistent with reprogramming. To understand the impact of daclizumab on T(regs) in vivo, we performed a clinical trial of daclizumab in combination with an experimental cancer vaccine in patients with metastatic breast cancer. Daclizumab administration led to a marked and prolonged decrease in T(regs) in patients. Robust CD8 and CD4 T cell priming and boosting to all vaccine antigens were observed in the absence of autoimmunity. We conclude that CD25 blockade depletes and selectively reprograms T(regs) in concert with active immune therapy in cancer patients. These results suggest a mechanism to target cancer-associated T(regs) while avoiding autoimmunity.

Tremelimumab in combination with exemestane in patients with advanced breast cancer and treatment-associated modulation of inducible costimulator expression on patient T cells.

PURPOSE: Tremelimumab is a fully human monoclonal antibody specific for CTL-associated antigen 4 (CTLA4) with single-agent activity in certain tumors but has not been evaluated in patients with breast cancer. EXPERIMENTAL DESIGN: In a phase 1 study, 26 patients with advanced, hormone-responsive breast cancer received tremelimumab (3-10 mg/kg) every 28 days or every 90 days plus exemestane 25 mg daily. The objectives were to determine safety and the maximum tolerated dose (MTD) of tremelimumab with exemestane and, secondarily, to assess tumor response, pharmacokinetics, and immune pharmacodynamics. RESULTS: Most treatment-related adverse events were mild to moderate with the most common being diarrhea (46% of patients), pruritus (42%), constipation (23%), and fatigue (23%). Dose-limiting toxicities were transient serum transaminase elevations (one patient) and diarrhea (four patients). The MTD of tremelimumab with exemestane was 6 mg/kg every 90 days. Among 13 patients treated at the MTD, none developed grade 3 or 4 treatment-related diarrhea. No pharmacokinetic interaction was observed between tremelimumab and exemestane. The best overall response was stable disease for >or=12 weeks in 11 patients (42%). Treatment was associated in most patients with increased peripheral CD4+ and CD8+ T cells expressing inducible costimulator (ICOS) and a marked increase in the ratio of ICOS+ T cells to FoxP3+ regulatory T cells. CONCLUSIONS: Tremelimumab plus exemestane is tolerable in patients with hormone-responsive advanced breast cancer. Treatment is associated with increased ICOS+ T cells, which likely signals immune activation secondary to CTL-associated antigen 4 blockade.