The majority of US and European physicians are wary of using a biosimilar medicine for an indication for which supporting clinical data are lacking, according to new research.

Physicians' attitudes towards "indication extrapolation" - where a biosimilar (generic biologic product) needs only to show similarity in a Phase III study for one indication for the product to be granted approval for other indications for which the original branded product is used - vary from country to country, according to the study, which is published by business information firm Decision Resources.

The authors found that French physicians have the most conservative views concerning indication extrapolation, compared to their colleagues in Germany and the US.

Moreover, the authors found that, out of the specialists which they surveyed, rheumatologists, nephrologists and gastroenterologists in particular told them that indication extrapolation should not be permitted, or should be done carefully, because of minute differences between the biosimilar and the branded original product which might be clinically significant.

'It's not surprising to see that rheumatologists, nephrologists and gastroenterologists we surveyed are wary of indication extrapolation, as these specialists have expressed a moderately conservative approach to biosimilars," commented Edward Wydysh, an analyst at Decision Resources.

"To meet physician expectations, biosimilar manufacturers will most likely need to conduct clinical trials in several indications, which may be cost-prohibitive for a smaller company to enter the market," he went on.

"If a biosimilar manufacturer with fewer resources wants to compete with an original biologic in more indications, it should focus on therapeutic areas and drug classes that surveyed physicians find most acceptable for extrapolation, for instance granulocyte colony stimulating factors (G-CSFs) in oncology," Dr Wydysh suggested.

It is estimated that more than 40 biosimilars are currently in development, and that the first branded biologics to face competition from the new generics will be those used in the treatment of cancer and rheumatoid arthritis.

- Earlier this month, Decision Resources also published research showing that US payers are likely to require more clinical information than what might be accepted by the Food and Drug Administration (FDA) for approvals.  

The study reported that FDA approval of biosimilar versions of monoclonal antibodies (MAbs) for oncology indications would only go a part of the way towards satisfying payers' concerns about bioequivalence, and suggested that manufacturers developing biosimilar MAbs would have to invest in clinical trials lasting at least one year in order to be able to allay the majority of payers' concerns.