The overall goal of our program is to develop more effective therapies for patients with thoracic cancers. This work falls under two main categories: 1. Exploiting mesothelin for cancer therapy in mesothelioma. 2. Immunotherapy and other approaches to treat lung cancer and thymic cancers. 1. Exploiting mesothelin for mesothelioma therapy and related translational research Our current studies are focused on using immunotherapy directed against the tumor differentiation antigen mesothelin, which is expressed on normal mesothelial cells lining the pleura, pericardium and peritoneum but is highly expressed in several human tumors especially mesothelioma, ovarian cancer, lung cancer and pancreatic adenocarcinomas. This differential expression of mesothelin makes it an attractive candidate for tumor specific therapy. Our efforts are now focused on exploiting it for mesothelioma therapy using different approaches. These include anti mesothelin immunotoxins (LMB-100), an anti-mesothelin drug conjugate (BAY 94-9343) and a mesothelin vaccine (CRS-207). LMB-100 is an immunotoxin consisting of the anti-mesothelin Fv linked to a truncated form of the potent bacterial toxin, Pseudomonas exotoxin A, which has been de-immunized to decrease its antigenicity. We have recently completed the phase I trial of LMB-100 and established its safety and maximum tolerated dose. Currently we are conducting a phase II study in patients with mesothelioma in combination with immune checkpoint inhibitor Pembrolizumab. We have recently completed a phase I clinical trial to determine the safety and MTD of the anti-mesothelin antibody drug conjugate BAY 94-9343, which consists of a humanized anti-mesothelin monoclonal antibody linked to the maytansinoid DM4 and a phase I study of the same in combination with chemotherapy. We have also conducted a Phase I clinical trial with mesothelin expressing live, attenuated Listeria monocytogenes (CRS207) along with chemotherapy, and have seen improved OS in patients with malignant pleural mesothelioma. Currently my laboratory is studying germline mutations in DNA repair genes that could predispose to mesothelioma and influence clinical outcome. We have shown that germline mutations in DNA repair genes increases sensitivity to platinum therapy and improves overall survival in patients with pleural mesothelioma. In the laboratory, we have focused on developing in-vitro and in-vivo models of human mesothelioma. We have established several early passage tumor cell lines from ascites and pleural fluid of patients. We have evaluated the morphological and genetic characteristics of these cell lines and are using them to study in-vitro drug sensitivity. Currently we are evaluating the sensitivity of these patient derived mesothelioma cell lines to PARP inhibitors (Olaparib and Talazoparib) and a DNA alkylating agent, Temozolomide with respect to their genetic background. Additionally, we have established a humanized mesothelioma xenograft tumor model with patient derived tumor cells and human PBMCs from healthy donor for in-vivo studies. As the development of Graft Versus Host Disease (GVHD) in the PBMC-humanized mouse model limits assessment of duration of anti-tumor efficacy, we have developed a syngeneic immunocompetent mouse model. Because the immunotoxin LMB-100 can target human mesothelin specifically, we established a human mesothelin expressing immunocompetent syngeneic mouse tumor model by transfecting PD-L1 positive mouse lung adenocarcinoma cell line with a hMSLN expressing vector encoding the membrane bound fragment of hMSLN. These cell lines were used to develop tumor. We have studied the effect of LMB-100 in combination with anti-PD1 antibody in both the models and have seen tumor regression. These models are essential to evaluate novel therapeutic agents for mesothelioma and for the mechanistic studies of anti-tumor efficacy. Other ongoing laboratory studies are focused on understanding the mesothelioma tumor immune micro-environment and changes following treatment with anti-mesothelin targeted agents. 2. Immunotherapy to treat thymic cancer and lung cancers. Thymic Cancers: Thymoma is a rare tumor characterized by infiltration of lymphocytes making them uniquely suitable for immune-checkpoint inhibition. Thymoma patients are currently being treated on a phase I clinical trial of the anti-PD-L1 monoclonal antibody MSB0010718C. We have seen remarkable anti-tumor activity in these patients that has been accompanied by side-effect profile unique to thymoma patients. In addition, we are conducting a Phase II study of sunitinib in thymic carcinomas. Lung Cancer: We are currently conducting clinical trial of the anti-PD-L1 monoclonal antibody MSB0010718C in patients with lung adenocarcinoma who have failed prior therapies. Our laboratory has recently shown that about 25% of patients with metastatic lung adenocarcinoma highly express mesothelin. Mesothelin expression in these tumors is highly associated with KRAS mutations and wild type EGFR status and is, independently, associated with poor prognosis. Our hypothesis is that patients with K-RAS mutant lung cancer can benefit from mesothelin directed therapies. Clinical trials of mesothelin directed therapies for treating lung cancer are about to open. Our laboratory is also studying the role of immune checkpoints in malignant mesothelioma so that drugs targeting this pathway can be exploited for treating mesothelioma.
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