Project Summary/Abstract Small-cell lung cancer (SCLC) is an aggressive and deadly cancer. Over 2/3 of SCLC are diagnosed at later stages, where patients are expected to survive for only 8-12 months with 5-year survival rates less than 7%. Smoking increases the risk of developing SCLC by up to 100-fold. While annual lung cancer screening using low-dose computed tomography (LDCT) can screen for other lung cancers, this modality is ineffective for detecting SCLC at earlier stages, where interventions can increase 5-year survival rates to >54%. SCLC can induce an autoimmune response, and our labs have shown a combined panel of 4 autoantibodies (AutoAb) can successfully identify SCLC tumors up to a year prior to diagnosis, proving the utility of these markers to identify and validate early SCLC in multiple sample sets. This fellowship proposal aims to develop antibody- based positron emission tomography (immunoPET) probes against these markers as a secondary screening method, allowing for earlier detection than is capable with current LDCT. Aim 1 explores the contribution of post-translational modifications (e.g., glycosylation, isoaspartylation, and citrullination) that are upregulated in cancer, including SCLC, to neopitopes recognized by these AutoAb, which may allow for more targeted theranostics. Aim 2 will develop additional monoclonal antibodies (mAb) against candidate SCLC AutoAb biomarkers to allow for a broad targeting of AutoAb differentially expressed in patient plasma. In Aim 3, these mAb will be conjugated to an infrared fluorophore, that will be used as a proof of concept for immuno-imaging of tumors in a murine model of SCLC using in vivo fluorescence and ex vivo immuno-fluorescence. The most promising 1-2 markers/mAb will then be developed into zirconium-89 conjugated immunoPET probes. Thus, it is envisioned that SCLC patients will be identified with an AutoAb blood test with tumor confirmation/localization with immunoPET tracers against SCLC AutoAb markers. This ultimately combines the sub-picomolar sensitivity of PET and sub-millimeter spatial resolution of CT with the high affinity and specificity of antibodies, allowing for detection of smaller, and thus less advanced, tumors that allow for earlier and more effective therapeutic interventions. Given the recalcitrant nature of SCLC and the difficulty of its identification via conventional CT, this proposed research aligns well the NCI’s scientific priority to detect and diagnose cancer when treatment is most effective. This fellowship training will allow the applicant to build upon existing cancer research skills, gaining complementary experience in 1) identifying post-translational modifications and the roles these play in neoantigen formation, 2) generating plasmids/recombinant proteins and development of mAbs, 3) mouse models of SCLC, 4) antibody-based PET tracers, 5) in vivo small animal translational imaging (luciferase, fluorescence, and PET), and 6) other professional devel...