The Food and Drug Administration’s Arthritis Advisory Committee, together with an added complement of dermatologists and gastroenterologists, unanimously recommended during meetings on July 12 and 13 that the agency license a biosimilar Humira (adalimumab) that is made by Amgen and a biosimilar Enbrel (etanercept) that is made by Sandoz for many of the same indications held by the reference drugs.
The FDA advisory panel that endorsed biosimilar Humira recommended the agent’s approval in a 26-0 vote for many, but not all of the indications currently assigned to Humira itself: rheumatoid arthritis, psoriatic arthritis, ankylosing spondylitis, juvenile idiopathic arthritis in patients at least 4 years old, plaque psoriasis, adult Crohn’s disease, and adult ulcerative colitis.
A slightly different group of 20 advisory panel members (without any gastroenterologists) voted 20-0 in favor of the FDA granting biosimilar Enbrel all five of the indications now held by Enbrel: rheumatoid arthritis, psoriatic arthritis, ankylosing spondylitis, juvenile idiopathic arthritis, and plaque psoriasis.
The biosimilar Humira and the biosimilar Enbrel are, respectively, the third and fourth candidate biosimilars to emerge from the FDA’s development program and receive advisory committee scrutiny and support. The first agent through the process, biosimilar filgrastim (Zarxio) received FDA approval in 2015 and is available in the United States. Although the second biosimilar through the process, the tumor necrosis factor inhibitor Inflectra that is biosimilar Remicade (infliximab), received FDA approval in April of this year, it has not yet become available for sale, although a spokeswoman for the company that will market it, Pfizer, said that the company expects to start U.S. sales of Inflectra before the end of 2016.
While the Arthritis Advisory Committee ended each of its daylong deliberations for each of the two candidate biosimilars with unanimous support, the panelists’ discussions among themselves and with FDA staffers reflected some uncertainty with the biosimilar concept, especially during the first day when they focused on biosimilar Humira. The major sticking point revolved around the regulatory pathway to approval first established by the Biologics Price Competition and Innovation Act of 2009 and subsequently refined by the FDA that allows a candidate biosimilar to establish its biosimilarity primarily though the results of analytical studies that establish that the candidate molecule is highly similar to the reference molecule. This approval scheme uses clinical trials in a confirmatory role to establish biosimilarity rather than as the linchpin of approval.
It also means that the FDA can grant clinical indications to the biosimilar drug based not on the results from clinical trials, but based entirely on what have already been demonstrated as safe and effective clinical applications for the reference drug. For example, the biosimilar Humira underwent testing in two clinical studies showing similar efficacy and safety as Humira in patients with rheumatoid arthritis and in patients with plaque psoriasis, but received endorsements based on extrapolations for an additional five indications. Biosimilar Enbrel was compared with Enbrel in patients with plaque psoriasis only and still received extrapolated indications for the additional four rheumatologic conditions.
“This is a new level of extrapolation, across indications,” noted Sarah E. Streett, MD, a gastroenterologist at Stanford (Calif.) University, one of several panelists who initially voiced uncertainty about the concept.
But FDA staffer Nikolay P. Nikolov, MD, who led the agency’s presentation, assured the panelists that the concept of extrapolation was at the heart of biosimilar development and regulatory assessment.
“We have confidence from the data that the two molecules [the reference drug and biosimilar drug] are so similar that we can rely on the safety and efficacy of the reference product. The premise of our approach to biosimilars is that this is not a new molecule that we know nothing about.”
The other uncertainty about biosimilar Humira and biosimilar Enbrel that raised concerns of many panelists were the prospects for nonmedical switching once these drugs reach the market. Nonmedical switching refers to when an insurance company or pharmacy benefit manager substitutes a biosimilar for a reference drug without approval from or even the knowledge of the prescribing physician or the patient. Many of the people who spoke during the public forum period on both days of hearings voiced their concerns about this prospect.
“Nonmedical switching is a major concern of clinicians and policy makers, and we need greater clarification from the FDA,” said committee chair Daniel H. Solomon, MD, a rheumatologist and professor of medicine at Harvard Medical School in Boston.
“I see a remarkable disconnect between the public’s concerns [about nonmedical switching] and the charge to the committee. These are essential issues that need a forum to be aired out,” said panelist Steven F. Solga, MD, chief of gastroenterology at St. Luke’s Hospital in Bethlehem, Pa.