Browsing by Author "Khanna, Vidhi Devendra"

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    Antibodies In Cancer Therapy: New Targets, Applications And Combination Strategies
    (2019-07) Khanna, Vidhi Devendra
    Over the last decade, antibodies have become an important component in the arsenal of cancer therapeutics. Their high-specificity, low-off target effects, desirable pharmacokinetics and high success rate are a few of the many attributes that make them amenable for development as drugs. The work presented here explores the targeting, mechanisms and use of antibody-based cancer therapy. In the first chapter, we used a phage display-based cell panning procedure to develop two fully humanized antibodies, Tw1S4_6 and Tw1S4_AM6, that bind specifically to HSPG2/perlecan, a protein found to be overexpressed on tumor cells. Immunohistochemistry studies revealed high HSPG2 expression across various tumor sub-types including melanoma, bladder cancer, glioblastoma and ovarian cancer. There was significant correlation between high HSPG2 expression and poor survival in triple negative breast cancer, bladder and ovarian cancers. The data presented here points towards the relevance of HSPG2 as a novel target for not only triple negative breast cancer but other malignancies as well. Based on its over-expression in different solid tumors, we evaluated HSPG2 as a therapeutic target in the second chapter. We observed significant tumor growth inhibition with Tw1S4_AM6 in the triple negative MDA-MB-231-LM2 breast cancer xenograft model. This efficacy was reduced in NSG mice, suggesting NK cell-mediated antibody dependent cellular cytotoxicity (ADCC) as a potential mechanism of action. In vitro studies using human PBMCs confirmed induction of ADCC with anti-HSPG2 antibodies. In addition, conjugation of Tw1S4_AM6 on the surface of polymeric nanoparticles enabled increased tumor cell uptake of nanoparticles, suggesting Tw1S4_AM6 could be valuable as a targeting ligand for drug delivery systems. There is a significant interest in designing therapeutic agents that can enhance ADCC and thereby improve clinical responses with approved antibodies. We have developed a suite of highly substituted imidazoquinolines, which activate TLR 7 and/or 8 and induce significantly higher levels of cytokines compared to the FDA-approved TLR7 agonist, imiquimod. In the third chapter, we evaluated our series of TLR7/8 agonists for their ability to improve ADCC. Our studies show that the second generation TLR 7/8 agonists induce robust pro-inflammatory cytokine secretion and activate NK cells. These agonists also enhanced ADCC in vitro. Finally, we found that these agonists significantly improved the anticancer efficacy of two monoclonal antibodies in vivo. Thus, the work presented here encompasses the three critical aspects of antibody therapeutics: identifying the target, understanding their mechanisms, and leveraging these mechanisms to improve their efficacy.
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    Antibody Conjugated Nanoparticles for Targeting Metastatic Triple Negative Breast Cancer
    (2016-09) Khanna, Vidhi Devendra
    Early detection and the availability of new treatments have improved the survival rates of patients presenting with local or regional breast cancer to as high as 99% and 85%, respectively. On the contrary, patients with metastatic disease have a dismal 5-year survival rate of 17%.1 Thus, there is an urgent need for treatment strategies directed towards metastasis. Our lab has developed antibodies (Clone 6 and AM6) capable of recognizing tumor cells that have undergone epithelial-to-mesenchymal transition (EMT), a key step in the generation of circulating tumor cells and metastasis. The goal of the current study was to determine whether we use these antibodies as targeting ligands for directing anticancer drug-loaded polymeric nanoparticles to metastatic triple negative breast cancer cells as a novel therapeutic option. Polymeric PLGA nanoparticles loaded with paclitaxel, a chemotherapeutic agent, were functionalized with the antibodies using thiol-maleimide chemistry. We optimized the conjugation reaction in order to achieve maximal cell uptake of nanoparticles without compromising antibody binding. In vitro studies were carried out in an MDA-MB-231 derivative cell line with enhanced lung metastatic potential as well as a melanoma metastatic cell line M12. Clone 6 nanoparticles and AM6 nanoparticles showed significant improvement in cellular uptake as well as retention. A competition experiment confirmed target-mediated uptake of nanoparticles. Cytotoxicity studies showed improved cell kill using Clone 6 nanoparticles and AM6 nanoparticles. Based on these promising in vitro results, we are currently carrying out in vivo studies in mice. The development of a targeted drug delivery system for the treatment of metastatic triple negative breast cancer can significantly enhance the survival rate for patients who often times have a life-expectancy of less than one year.2