An especially thorny issue for panelists and the FDA was the design of the phase IV trial, which is a double-blind, placebo-controlled, multi-center international trial comparing OCA with placebo for PBC. This trial has already begun to enroll patients and will continue to recruit for a total of 2 years; follow-up will continue for 6 years with quarterly visits. Historical control data from a global PBC database are also available for analysis.
Panelist Dr. Timothy Lipman, emeritus chief of the GI-hepatology-nutrition center at the Department of Veterans Affairs Medical Center in Washington, said, “As a clinician who is very interested in clinical study methodology, I am concerned about possible bias. And the use of historical control data is a nonstarter,” since the study quality would suffer. “Changes in protocol as a study goes on are always problematic,” so the FDA’s request for feedback on how to tinker with study design was a concern.
But the biggest concern voiced by Dr. Lipman and others on the committee, including FDA representatives, was the huge barrier to enrollment that’s presented by a placebo-controlled study for a drug that has already been approved. “This is always a major issue for the FDA in approving drugs under accelerated approval,” acknowledged Dr. Amy Egan, deputy director of the FDA’s office of drug evaluation III, office of new drugs. The anticipation of difficulty in enrolling is one reason the historical control arm is held in reserve, she said. Intercept’s vice president for clinical development Dr. Leigh MacConell concurred, saying of the discussions with the FDA about study design, “It was a very difficult conversation, because we agree with your assessment regarding the feasibility” of the study.
The FDA noted remaining issues requiring ongoing study of OCA for PBC. Among these is the need to confirm the clinical benefit of OCA across the full spectrum of severity of PBC, from early stage to advanced disease. “FDA would also like to evaluate additional data on use of OCA as monotherapy,” said Dr. Lara Dimick-Santos, cross-discipline team leader at the FDA.
The course of PBC is variable; it affects women approximately 10 times more frequently than men. Occurring in approximately 1 in 1,000 women over the age of 40, its prevalence is thought to be increasing. PBC is usually asymptomatic for some time; when symptoms occur, fatigue and pruritis are the most common. Concomitant autoimmune diseases are common and an earlier age at diagnosis is often associated with a worse disease course. A significant number of those affected by PBC will progress to death or liver transplantation.
Intercept Pharmaceuticals is also studying OCA for use in other liver conditions, including nonalcoholic steatohepatitis (NASH).
All committee members submitted information to the FDA regarding conflicts of interest. The FDA usually follows the recommendations of its advisory panels.
*Changes were made to this story on April 8, 2016.
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