Fibroblast Activation Protein Inhibitor

Seventy (N=70) patients with suspected pleural mesothelioma (PM) lesions referred to pleural biopsy will be recruited, and undergo an additional FAPI PET/CT at primary staging. The FAPI PET/CT results will be compared to conventional imaging (including FDG PET/CT). The diagnostic accuracy will be determined with histopathology as reference standard. For patients undergoing anticancer treatment (chemotherapy, immunotherapy, other treatment), an additional FAPI PET/CT and an additional FDG PET/CT will be conducted after the study subjects have completed 2-3 series of anticancer treatment. The feasabilitiy of FAPI PET/CT in response evaluation will be investigated. All study specific analyzes will be blinded and will not influence the patient management / treatment.

Fibroblast-activation protein (FAP) is a type Ⅱ transmembrane serine protease and is overexpressed in cancer-associated fibroblasts (CAFs). CAFs are the predominant component in the stroma of epithelial neoplasms. FAP can be detected in various of malignant neoplasms and is associated to tumor cell migration, invasion, and angiogenesis. Recently, a novel molecular probe, gallium 68-labelled FAP inhibitor (68Ga-FAPI), has been developed and used for visualization of tumor stroma by targeting FAP. Recent studies show favorable diagnosis efficiency in a variety of tumors, especially in gastrointestinal cancer, but the previous studies were all small-sample data or case reports. Therefore, further large-size research is necessary to confirm the advantages of 68Ga-FAPI in various of malignant tumors.

Rationale: The diagnosis and pathogenesis of long COVID remains unknown. We have previously shown that \[68Ga\]FAPI Positron Emission Tomography-Computed Tomography (PET/CT) imaging shows potential for diagnosis and molecular understanding of this syndrome. We have previously shown that fibroblast activation protein (FAP) can be imaged in the lung, muscle and nasopharynx of long COVID patients (with dyspnea and fatigue). However, these preliminary data are derived from a selective group of patients with long COVID after critical COVID-19. We aim to explore the generalizability of these findings in patients with long COVID with dyspnea and fatigue, irrespective of the severity of their acute SARS-CoV-2 infection. Primary objective: To assess if pulmonary fibroblast activity, measured by \[68Ga\]FAPI-46 PET/CT, is higher in patients with current long COVID dyspnea and fatigue compared to patients with resolved complaints. Study design: This is a ZonMw funded single centre prospective observational cohort study of long COVID-19 patients with dyspnea and fatigue. Study population: We will recruit 60 adult long COVID patients (aged \>20 years) of which 30 have complaints of dyspnea and fatigue and compare them to 30 patients with resolved complaints and healthy controls. Main study parameters/endpoints: The primary endpoint is FAP expression in the lung measured by \[68Ga\]FAPI-46 PET/CT. Secondary endpoints are the expression of FAP in other tissues (muscle) and the relation between FAP and inflammation and remodelling biomarkers in various biological samples (e.g. serum/nasal epithelium). Study procedures: In a single visit day the following data and samples will be collected: questionnaires, a lung function test, 6-minute walking test, blood samples, nose swabs, \[68Ga\]FAPI PET/CT scan and HRCT scan. When increased \[68Ga\]FAPI uptake is measured in the muscles a muscle biopsy will be performed as well.

The main objectives are: (i) to identify candidate fibrotic cellular pathways in UC patients treated with a JAK inhibitor filgotinib), and (ii) to detect and monitor in vivo fibrosis in UC patients using FAPi-PET/CT imaging

This is a phase II clinical trial to evaluate the capability of 68Ga-labeled targeted covalent radiopharmaceutical (TCR) fibroblast activation protein inhibitor (FAPI) PET/CT to guide the surgical treatment of medullary thyroid carcinoma (MTC). The surgical extent of MTC is determined based on the lesion range revealed by 68Ga-TCR-FAPI PET/CT, with the main endpoint being 1-month post-surgical calcitonin level.