Decitabine/Cedazuridine (INQOVI), an Oral DNA Demethylating Agent, in Subjects With BAP1 Cancer Predisposition Syndrome and Subclinical, Early-Stage Mesothelioma

* INCLUSION CRITERIA: * Participants with history of germline BRCA1-Associated Protein-1 (BAP1) mutations. * Histologically confirmed by NCI LP subclinical, early-stage (Tx-T1) mesotheliomas. * Participants with other early-stage BAP1-associated malignancies in addition to subclinical, early-stage mesotheliomas are eligible for study. * The extent of the disease (Tx by radiographic imaging) must be insufficient to warrant approved front-line therapies (surgery, chemotherapy, immunotherapy) per standard of care (SOC). Participants with cT1 tumors may be eligible for study if they have been offered and have refused front-line SOC treatment. * Age \>= 18 years. * Evaluable disease as confirmed by minimally invasive (videoscopic) assessment (thoracoscopy and/or laparoscopy) performed at screening (within 8 weeks prior to treatment initiation). * Willingness to undergo pre- and post-treatment minimally invasive thoracoscopy and/or laparoscopy to assess treatment response. * Willingness to co-enroll on 20C0106 (Prospective Evaluation of High Resolution Dual Energy Computed Tomographic Imaging, Noninvasive (Liquid) Biopsies, and Minimally Invasive Surgical Surveillance for Early Detection of Mesotheliomas in Patients with BAP1 Tumor Predisposition Syndrome) and/or 06C0014 (Prospective Evaluation of Genetic and Epigenetic Alterations in Patients with Thoracic Malignancies) to enable collection/processing of tumor, blood and normal pleura if applicable per PI. * ECOG performance statu…