How filgotinib works
It is a selective JAK1 (Janus kinase 1) inhibitor. JAK1 is an enzyme with an essential role in the promotion of biologic responses induced by a subset of cytokine receptors, proteins that lead to inflammation.
Filgotinib has shown efficacy in moderate-to-severe CD. Different doses of the investigational drug have been shown to inhibit interleukin-producing T-helper cells. Interleukins are cytokines produced by T cells that promote the growth of different immune cells.
Filgotinib in clinical trials
Although it has shown a rapid onset of action in clinical studies of people with CD and rheumatoid arthritis, its safety and effectiveness have not been officially established.
A Phase 2 study called FITZROY (NCT02048618) assessed the effectiveness and safety of filgotinib in 174 participants with active CD and evidence of mucosal ulceration.
Participants received either 200 mg of filgotinib once daily, or placebo for 10 weeks. The primary objective was clinical remission, defined by a CD activity index (CDAI) of less than 150 at week 10. After the tenth week, participants received either 100 or 200 mg of filgotinib, according to their response, or placebo, for 10 weeks more.
From the group of 128 participants who received 200 mg of filgotinib, 60 (47 percent) achieved clinical remission at week 10, compared to 10 out of 44 participants who received placebo (23 percent), with an acceptable safety profile.
The majority of serious adverse events were related to the worsening of CD.
An efficacy and safety study (NCT03077412) in the treatment of perianal fistulizing CD has just started recruiting participants. The primary objective of this Phase 2 study is to evaluate the efficacy of filgotinib compared to placebo in establishing combined fistula response after 24 weeks of treatment. The estimated study completion date is June 2019.
Another Phase 2 study that is recruiting participants will assess the safety and effectiveness of filgotinib in the treatment of small bowel CD. The primary objective measure is the proportion of participants who achieve clinical remission at week 24. The estimated study completion date is April 2019.
A Phase 3 study (NCT02914561) will assess the safety of filgotinib during induction and maintenance treatment of moderately to severely active CD. The primary objective measures include the proportion of participants who achieve clinical remission and endoscopic response at week 10 for the induction study, or at week 58 for the maintenance study. Secondary objectives include measures such as the proportion of participants who achieve clinical remission and/or endoscopic response at week 10 and 58, for the induction or maintenance study, respectively, and the plasma concentrations of filgotinib and its metabolites. The estimated study completion date is December 2019.
A second Phase 3 study (NCT02914600) the objective of which is to observe the long-term safety of filgotinib in people who have completed or discontinued prior studies, also is recruiting participants. The primary outcome measures include the overall safety profile of filgotinib as measured by the percentage of participants who experience adverse events and abnormal clinical laboratory tests up to 144 weeks plus 30 days. This study is estimated to be completed by 2022.
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