Inclusion Criteria:  Participants with FSGS/TR-MCD who have completed the treatment phase from an interventional clinical study with GFB-887. Participants who were discontinued for rising proteinuria from a GFB-887 interventional study may be considered for enrollment following consultation with the Medical Monitor. Participants who enrolled in any other interventional study during the time between completion of the prior GFB-887 interventional study and this study may be considered for enrollment following consultation with the Medical Monitor.  Exclusion Criteria:  Participant is unable to take oral medications Participant has an unstable medical condition based on medical history, physical examination, laboratory tests, ECGs, vital signs or is otherwise unstable in the judgement of the Investigator which would pose a risk to the participant or interfere with study evaluation, procedures, or completion Evidence of significant hypersensitivity, intolerance, or allergy to any component of investigational product GFB-887