Feasibility Study of MET-4: Evaluating Fecal Microbiome Effects in Immunotherapy Patients

Inclusion Criteria: * Signed written and voluntary informed consent * Age \>=18 years, male or female * Histologically or cytological documented locally-advanced or metastatic solid malignancy which is incurable. * Group A: Is already on treatment with monotherapy anti-PD-1 or PD-L1 immune checkpoint inhibitor, not in the context of a therapeutic clinical trial. Group B: Is intended to start on treatment with monotherapy anti-PD-1 or PD-L1 immune checkpoint inhibitors as considered appropriate by treatment physician, and not in the context of a therapeutic clinical trial. Group C: Is already on treatment with monotherapy anti-PD-1 or PD-L1 immune checkpoint inhibitor, not in the context of a therapeutic clinical trial with first unconfirmed PD on evaluation scan per investigator's assessment. * Be willing to provide 10-15 unstained slides of archival tissue sample. Subjects who decline or have not sufficient archived tissue samples may still enroll if all other criteria are eligible. * Be willing and able to provide stool and blood specimen for analyses at protocol specified time points. * Have measurable disease based on RECIST 1.1 * Performance status of 0-2 on the Eastern Cooperative Oncology Group (ECOG) performance scale. * Prior therapy with any immunotherapy allowed. * Not pregnant for females of child bearing potential as indicated by negative serum or urine pregnancy test within 72 hours of study start. Exclusion Criteria: * Subjects unable to swallow orally ad…