The systemic toxicity associated with immunoconjugates in radio- and chemo- immunotherapy may be reduced significantly by the dual selectivity provided by monoclonal antibody (Mab)-photosensitizer (PS) conjugates. Selectivity is provided by localization of PS on target cells with Mabs and by the spatial control of illumination. The goal of this proposal is to synthesize purified and wellcharacterized Mab-PS conjugates for the selective photodestruction of human ovarian carcinoma cells. However, the broader significance of this research may be that the successful site-specific synthesis of well-characterized conjugates will be more generally useful in a variety of investigational areas where photodestruction or detection of selected cell populations is desired. An anti-ovarian carcinoma Nab OC125 will be used and a long wavelength absorbing chlorin e6 derivative CMA will be the PS. Synthesis of conjugates using CMA-bearing polyglutamic acid (PGA) reacted site-specifically at the Mab carbohydrate functionality is proposed. The site-specific reaction is affected by functionalizing the PGA with hydrazine. Purification and physico-, bio- and photochemical characterization of conjugates is planned. Physicochemically, conjugates will be characterized as to their PS substitution ratios, size, charge and solubility by spectroscopic, chromatographic and electrophoretic techniques. Biochemically, immunoreactivity (binding affinity and number of binding sites), specificity, cellular localization and effects of internalization will be investigated. Photochemically, absorption characteristics, photostability and relative singlet oxygen quantum yields will be determined for the conjugates and free CMA. In vitro phototoxicity to target and non-target cells will be investigated. Finally, experiments to investigate in vivo photosensitization in tumor modulation studies will be conducted. An ascites murine model mimicking human ovarian carcinoma will be used. Dark toxicity and biodistribution will be investigated. Collaborative experiments on light delivery and dosimetry are planned. It is believed that a comprehensive investigation of photoimmunoconjugates will optimize their potential as photochemotherapeutic and photodiagnostic agents.

National Institute of Health (NIH)
National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS)
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Radiation Study Section (RAD)
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Massachusetts General Hospital
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