- Email: [email protected]
51 Murine mesothelioma treatment with peritumoral injections of CpG alone or combined with CD40 ligand
Friday, October 20, 2006 / Workshop: Immunology and immunotherapy of mesothelioma Conclusion: These results highlight the general importance of targeting the tumor stroma to prevent the escape of variant cancer cells.
50
Antibody-based treatment for mesothelioma: Clinical trials and laboratory studies
R. Hassan, J. Zhang, I. Pastan. National Cancer Institute, Bethesda, USA Monoclonal antibodies are now being widely used to treat patients with solid tumors. Our work has focused on developing antibody based therapies for mesothelioma by targeting the tumor antigen mesothelin. The limited expression of mesothelin on normal mesothelial cells and high expression in mesotheliomas makes it an attractive candidate for targeted therapy. We are currently conducting clinical trials of two agents, SS1P and MORAb009, that target mesothelin. SS1P is a recombinat immunotoxin, developed in our laboratory, that consists of an anti-mesothelin Fv linked to a truncated Pseudomonas exotoxin. Based on pre-clinical activity in animal models, a phase I clinical trial of SS1P was initiated and has just been completed. Thirty-four patients, including 21 patients with mesothelioma, were treated on this study. SS1P showed encouraging anti-tumor activity including minor tumor responses in 4 patients, stable disease in 19 patients and resolution of ascites in some patients. The dose limiting toxicity was pleuritis that was reversible. Recent studies in our laboratory show marked synergy between SS1P and gemcitabine against mesothelin-expressing tumor xenografts in athymic nude mice. Based on these studies, a phase II clinical trial of SS1P plus gemcitabine is being initiated. The second agent we are studying in the clinic is MORAb-009, a humanized anti-mesothelin monoclonal antibody. MORAb-009 was developed as a collaboration between our group and Morphotek Inc. In-vitro studies have shown MORAb-009 to be very effective in mediating ADCC and inhibiting cell adhesion. In xenograft models, MORAb-009 has anti-tumor activity as a single agent which is markedly enhanced when combined with chemotherapy. A phase I dose-escalation study of MORAb-009 is ongoing. Our studies show the potential value of antibody-based therapies targeting mesothelin for the treatment of mesothelioma. Clinical trials of SS1P and MORAb-009 in combination with chemotherapy will help to fully elucidate the role of these agents in mesothelioma.
51
Murine mesothelioma treatment with peritumoral injections of CpG alone or combined with CD40 ligand
R.S. Kornbluth, S. Barzee, V. Snarsky, C. Toppin, B. Tran, G.W. Stone. University of California at San Diego, La Jolla, USA Mesothelioma can be modeled in mice using asbestos-induced tumor cells such as AB1. Based on the ability of CD40 stimulation to activate dendritic cells and promote CD8+ T cell responses, previous studies have examined CD40 stimulation as a therapeutic modality for mesothelioma. TLR agonists such as CpG oligodeoxynucleotides (TLR9 stimulus) and polyinosinic-polycytidylic acid (poly(I:C), TLR3 stimulus) are other immunostimulatory agents with antitumor potential. The present study tested CD40 stimulation using a plasmid encoding a multimeric soluble form of CD40L produced as a fusion protein with pulmonary surfactant protein D (pSP-D-CD40L). Established AB1 tumors were injected with pSP-D-CD40L but no significant antitumor effects were found. However, the injection of CpG, either alone or in combination with pSP-D-CD40L and poly(I:C), strongly suppressed tumor growth and often led to long-term tumor-free survival. The effect of CpG could not be replicated by combining pSP-D-CD40L with a plasmid for interferon-gamma. The regressing tumors responding to a triple combination of pSP-D-CD40L + CpG + poly(I:C) contained an increased number of CD8+ T cells and a marked increase in F4/80+ macrophages. While these data did not show an effect of pSP-D-CD40L against AB1 tumors, this mesothelioma model confirms that CpG is a promising tumor immunotherapy agent.
52
Dendritic cell-based immunotherapy for malignant pleural mesothelioma
J. Hegmans, A. Hemmes, J. Aerts, H. Hoogsteden, B. Lambrecht. Erasmus MC, Rotterdam, Netherlands Background: Exploiting the immunostimulatory capacities of dendritic cells (DC’s) holds great promise for cancer immunotherapy. DC’s are extremely potent antigen presenting cells specialized for inducing activation and proliferation of CD8+ cytotoxic T-lymphocytes and other lymphocytes. DCs can now be generated in large amounts in vitro, in the absence of the suppressing tumor microenvironment, and subsequently injected in a mature state to induce anti-tumor responses. We studied the possibility to harness the potency and specificity of DCs in a murine mesothelioma model. Based on these studies, a phase I clinical trial was initiated to define the safety and toxicity of tumor lysate-pulsed DCs injected in patients with mesothelioma.
S13
Methods: In a preclinical study, the impact of antigen source, DC maturation status, and timing of administration on outcome was studied. In the subsequent phase I clinical study, patients are treated with chemotherapy followed by three vaccinations of autologous tumor lysate-loaded monocyte-derived DCs. Secondary end-points include immune responses by skin delayed type hypersensitivity reactions. Read-out parameters are the side effects, immune responses, anti-tumor responses and survival of this DC-based immunotherapy both in vivo and in vitro. Results: Mice receiving tumor lysate-pulsed DCs before tumor challenge were protected for months. DCs given after tumor challenge had the capacity to slow down tumor growth although tumor load played an important role in survival. The first mesothelioma patients treated with DC vaccinations showed minimal side effects (self-limited fever/mild local reactions) and induction of immune responses (both in skin test and blood analysis) could be measured. Conclusions: We have demonstrated in a murine model that immunotherapy using dendritic cells is effective against mesothelioma even when tumorassociated antigens remain undefined. First results from our phase I clinical trail indicate that DC-based immunotherapy is safe and feasible for mesothelioma patients.
53
Identifying and targeting a spectrum of internalizing cell surface antigens expressed by mesothelioma
B. Liu 1 , F. An 1 , S. Bidlingmaier 1 , S. Wilson 1 , V.C. Broaddus 1 , S.L. Nishimura 1 , D.C. Drummond 2 . 1 University of California at San Francisco, San Francisco, USA; 2 Hermes Background: Due to relatively easy accessibility to extracellularly administered targeting molecules, tumor-specific cell surface antigens are invaluable for therapeutic development. The molecular compositions of the tumor cell surface, however, are highly complex. Relevant antigens include post-translational modifications that may not be readily predicted from studies of genomic copy number or mRNA levels. Because monoclonal antibodies (mAbs) recognize a wide range of antigenic determinants with high affinity and specificity, and are able to discern subtle differences in antigen structure and conformation, they can be used to identify tumor cell surface epitopes. Isolating these epitopes enables the antibodies to achieve specific binding to neoplastic cells, an ability which could be utilized in applications such as induction of antibody dependent cell cytotoxicity (ADCC) or inhibition of signaling pathways involved in tumor cell migration, growth and survival. In addition, antibodies targeting internalizing tumor epitopes could be exploited to achieve specific intracellular delivery of chemotherapeutic drugs. Methods & Results: We have taken a functional approach to address the problem of identifying mesothelioma-specific cell surface antigens. By selecting a naïve human antibody phage display library directly on the surface of live mesothelioma cells, we have identified a panel of internalizing single chain antibodies that specifically target mesothelioma cells. When conjugated to liposomes encapsulating small molecules, these antibodies delivered payload specifically to mesothelioma cells but not to control cells including immortalized normal human mesothelial cells. Most importantly, these antibodies recognized mesothelioma cells in situ in actual cases (epithelioid, sarcomatoid, and mixed types) by immunohistochemistry study, and therefore defined a panel of clinically relevant tumor antigens. Conclusions: The ability to deliver payload intracellularly and to recognize mesothelioma cells in situ make these antibodies attractive candidates for the development of targeted therapy. Further therapeutic and diagnostic development will be aided by the identification of corresponding tumor antigens.
50
Antibody-based treatment for mesothelioma: Clinical trials and laboratory studies
R. Hassan, J. Zhang, I. Pastan. National Cancer Institute, Bethesda, USA Monoclonal antibodies are now being widely used to treat patients with solid tumors. Our work has focused on developing antibody based therapies for mesothelioma by targeting the tumor antigen mesothelin. The limited expression of mesothelin on normal mesothelial cells and high expression in mesotheliomas makes it an attractive candidate for targeted therapy. We are currently conducting clinical trials of two agents, SS1P and MORAb009, that target mesothelin. SS1P is a recombinat immunotoxin, developed in our laboratory, that consists of an anti-mesothelin Fv linked to a truncated Pseudomonas exotoxin. Based on pre-clinical activity in animal models, a phase I clinical trial of SS1P was initiated and has just been completed. Thirty-four patients, including 21 patients with mesothelioma, were treated on this study. SS1P showed encouraging anti-tumor activity including minor tumor responses in 4 patients, stable disease in 19 patients and resolution of ascites in some patients. The dose limiting toxicity was pleuritis that was reversible. Recent studies in our laboratory show marked synergy between SS1P and gemcitabine against mesothelin-expressing tumor xenografts in athymic nude mice. Based on these studies, a phase II clinical trial of SS1P plus gemcitabine is being initiated. The second agent we are studying in the clinic is MORAb-009, a humanized anti-mesothelin monoclonal antibody. MORAb-009 was developed as a collaboration between our group and Morphotek Inc. In-vitro studies have shown MORAb-009 to be very effective in mediating ADCC and inhibiting cell adhesion. In xenograft models, MORAb-009 has anti-tumor activity as a single agent which is markedly enhanced when combined with chemotherapy. A phase I dose-escalation study of MORAb-009 is ongoing. Our studies show the potential value of antibody-based therapies targeting mesothelin for the treatment of mesothelioma. Clinical trials of SS1P and MORAb-009 in combination with chemotherapy will help to fully elucidate the role of these agents in mesothelioma.
51
Murine mesothelioma treatment with peritumoral injections of CpG alone or combined with CD40 ligand
R.S. Kornbluth, S. Barzee, V. Snarsky, C. Toppin, B. Tran, G.W. Stone. University of California at San Diego, La Jolla, USA Mesothelioma can be modeled in mice using asbestos-induced tumor cells such as AB1. Based on the ability of CD40 stimulation to activate dendritic cells and promote CD8+ T cell responses, previous studies have examined CD40 stimulation as a therapeutic modality for mesothelioma. TLR agonists such as CpG oligodeoxynucleotides (TLR9 stimulus) and polyinosinic-polycytidylic acid (poly(I:C), TLR3 stimulus) are other immunostimulatory agents with antitumor potential. The present study tested CD40 stimulation using a plasmid encoding a multimeric soluble form of CD40L produced as a fusion protein with pulmonary surfactant protein D (pSP-D-CD40L). Established AB1 tumors were injected with pSP-D-CD40L but no significant antitumor effects were found. However, the injection of CpG, either alone or in combination with pSP-D-CD40L and poly(I:C), strongly suppressed tumor growth and often led to long-term tumor-free survival. The effect of CpG could not be replicated by combining pSP-D-CD40L with a plasmid for interferon-gamma. The regressing tumors responding to a triple combination of pSP-D-CD40L + CpG + poly(I:C) contained an increased number of CD8+ T cells and a marked increase in F4/80+ macrophages. While these data did not show an effect of pSP-D-CD40L against AB1 tumors, this mesothelioma model confirms that CpG is a promising tumor immunotherapy agent.
52
Dendritic cell-based immunotherapy for malignant pleural mesothelioma
J. Hegmans, A. Hemmes, J. Aerts, H. Hoogsteden, B. Lambrecht. Erasmus MC, Rotterdam, Netherlands Background: Exploiting the immunostimulatory capacities of dendritic cells (DC’s) holds great promise for cancer immunotherapy. DC’s are extremely potent antigen presenting cells specialized for inducing activation and proliferation of CD8+ cytotoxic T-lymphocytes and other lymphocytes. DCs can now be generated in large amounts in vitro, in the absence of the suppressing tumor microenvironment, and subsequently injected in a mature state to induce anti-tumor responses. We studied the possibility to harness the potency and specificity of DCs in a murine mesothelioma model. Based on these studies, a phase I clinical trial was initiated to define the safety and toxicity of tumor lysate-pulsed DCs injected in patients with mesothelioma.
S13
Methods: In a preclinical study, the impact of antigen source, DC maturation status, and timing of administration on outcome was studied. In the subsequent phase I clinical study, patients are treated with chemotherapy followed by three vaccinations of autologous tumor lysate-loaded monocyte-derived DCs. Secondary end-points include immune responses by skin delayed type hypersensitivity reactions. Read-out parameters are the side effects, immune responses, anti-tumor responses and survival of this DC-based immunotherapy both in vivo and in vitro. Results: Mice receiving tumor lysate-pulsed DCs before tumor challenge were protected for months. DCs given after tumor challenge had the capacity to slow down tumor growth although tumor load played an important role in survival. The first mesothelioma patients treated with DC vaccinations showed minimal side effects (self-limited fever/mild local reactions) and induction of immune responses (both in skin test and blood analysis) could be measured. Conclusions: We have demonstrated in a murine model that immunotherapy using dendritic cells is effective against mesothelioma even when tumorassociated antigens remain undefined. First results from our phase I clinical trail indicate that DC-based immunotherapy is safe and feasible for mesothelioma patients.
53
Identifying and targeting a spectrum of internalizing cell surface antigens expressed by mesothelioma
B. Liu 1 , F. An 1 , S. Bidlingmaier 1 , S. Wilson 1 , V.C. Broaddus 1 , S.L. Nishimura 1 , D.C. Drummond 2 . 1 University of California at San Francisco, San Francisco, USA; 2 Hermes Background: Due to relatively easy accessibility to extracellularly administered targeting molecules, tumor-specific cell surface antigens are invaluable for therapeutic development. The molecular compositions of the tumor cell surface, however, are highly complex. Relevant antigens include post-translational modifications that may not be readily predicted from studies of genomic copy number or mRNA levels. Because monoclonal antibodies (mAbs) recognize a wide range of antigenic determinants with high affinity and specificity, and are able to discern subtle differences in antigen structure and conformation, they can be used to identify tumor cell surface epitopes. Isolating these epitopes enables the antibodies to achieve specific binding to neoplastic cells, an ability which could be utilized in applications such as induction of antibody dependent cell cytotoxicity (ADCC) or inhibition of signaling pathways involved in tumor cell migration, growth and survival. In addition, antibodies targeting internalizing tumor epitopes could be exploited to achieve specific intracellular delivery of chemotherapeutic drugs. Methods & Results: We have taken a functional approach to address the problem of identifying mesothelioma-specific cell surface antigens. By selecting a naïve human antibody phage display library directly on the surface of live mesothelioma cells, we have identified a panel of internalizing single chain antibodies that specifically target mesothelioma cells. When conjugated to liposomes encapsulating small molecules, these antibodies delivered payload specifically to mesothelioma cells but not to control cells including immortalized normal human mesothelial cells. Most importantly, these antibodies recognized mesothelioma cells in situ in actual cases (epithelioid, sarcomatoid, and mixed types) by immunohistochemistry study, and therefore defined a panel of clinically relevant tumor antigens. Conclusions: The ability to deliver payload intracellularly and to recognize mesothelioma cells in situ make these antibodies attractive candidates for the development of targeted therapy. Further therapeutic and diagnostic development will be aided by the identification of corresponding tumor antigens.