Data extrapolation hit the headlines last week when AbbVie CEO Richard Gonzalez said his firm was factoring the regulatory practice into its strategy ahead of the upcoming US review of Remsima (infliximab), Celltrion’s version of J&J’s Remicade.
If the Celltrion biosimilar is approved for the same indications as Remicade it will also compete with AbbVie’s rheumatoid arthritis treatment Humira (adalimumab) Gonzalez said, adding that in such circumstances the firm would expect to see “extrapolation in all the major markets.”
Extrapolation essential
Extrapolation is a main reason that biosimilars cost less than originators according to Dr. Steinar Madsen, Medical Director at the Norwegian Medicines Agency, who told us he strongly supports the practice as long as it is based on sound scientific evidence.
“Extrapolation is an essential element for biosimilars,” Madsen said, adding that "when developing a biosimilar, you essentially can save money and time by doing fewer clinical studies, as compared to the originator.
“Usually, this [data extrapolation] is not very controversial, considering that the mechanism of action is usually well known,” he continued, adding that while “there is in most cases no reason to believe that the originator and biosimilar will behave differently, extrapolation must be justified on relevant scientific evidence in all cases.”
US FDA’s views
But application of data extrapolation is not uniform. Celltrion’s infliximab biosimilar, for example, was cleared as a treatment for inflammatory bowel disease in Europe based on the principle, but not in Canada.
The US FDA uses data extrapolation, or at least it has done with the only biosimilar approved to date.
“Zarxio [Sandoz’s version of Amgen’s Neupogen (filgastrim)] was approved for all indications of the reference product at the time,” Sreejit Mohan, a spokesman for the Novartis offshoot, told us.
“Amgen has since secured one more indication which is not on the Zarxio label.
“The decision for granting extrapolation depends on the totality of evidence that is submitted.”
Pfizer’s CRL
Hospira’s Retacrit, a potential biosimilar to Amgen’s Epogen (epoetin alfa), was submitted for review in the US last year for all indications of the reference product.
The product was knocked back in November when the FDA issued a Complete Response Letter.
However, a spokesman from Hospira’s owner Pfizer told us “confidence in the process of extrapolation reduces or eliminates the need for duplicative clinical studies for the biosimilar in multiple indications.”
He added: “The ability to extrapolate is appropriate if justified on sound scientific principles and the totality of data, including mode of action, analytical and clinical trial data.”