The purpose of this research study is to help us understand whether a diet can help children with Ulcerative Colitis (UC) to feel better without needing to take additional medications. Currently, it is thought that UC causes an imbalance in the good and bad bacteria that live inside our gut. We also know that certain foods can change how these good and bad bacteria live, and possibly contribute to UC symptoms. We think a specific diet could help create a better balance in your gut and help you feel better. This study is trying to figure out if a diet can help treat UC.

The primary objective of this study is to observe the long-term safety of filgotinib in adults who have completed or met protocol specified efficacy discontinuation criteria in a prior Gilead-sponsored filgotinib treatment study in ulcerative colitis (UC).

The objectives of this open-label extension−safety monitoring (OLE-SM) study are as follows: Part 1 (Open-Label Extension; OLE) • To assess the long-term safety and efficacy of etrolizumab in patients eligible for Part 1 (OLE) Part 2 (Safety Monitoring; SM) • Progressive multifocal leukoencephalopathy (PML)

Full Study Title: An Open-Label, 2-Part, Multicenter, Post-marketing Study to Evaluate the Effect of Moderately or Severely Active Ulcerative Colitis or Crohn's Disease on Cytochrome P-450 Enzyme Substrates Compared to Healthy Subjects and the Effect of Vedolizumab Treatment on Cytochrome P-450 Enzyme Substrates in Subjects With Ulcerative Colitis or Crohn's Disease.

This study is designed to find out if having the medical conditions Ulcerative Colitis or Crohn’s Disease affects the way commonly used medications are broken down in the body.

The primary objective of this study is to observe the long-term safety of Filgotinib in adults who have completed or met protocol specified efficacy discontinuation criteria in a prior Gilead-sponsored Filgotinib treatment study in Crohn's disease (CD).