ASCO 2016

Trial of proposed trastuzumab biosimilar, MYL-1401O vs Herceptin

Dr Hope Rugo - University of California, San Francisco, USA

I spoke today about a randomised double blind phase III trial called the HERITAGE study that evaluated a proposed trastuzumab biosimilar compared to the reference product branded trastuzumab or Herceptin.

Can you explain just briefly what biosimilars are?

Biosimilars are complex biologic agents different from the traditional small chemicals that are the generics we’re used to seeing on the market that don’t have to go through complicated testing to assure a similarity. Biosimilars are defined as larger molecular weight complicated agents and the regulatory agencies have set up guidelines in order to try and establish equivalency, understanding that patents will run out and we need to have different options. It’s also the hope that having additional options will reduce the cost of these agents and make them more accessible worldwide since, although the biologics are highly effective and, for trastuzumab, have improved survival in early and late stage breast cancer, they’re very expensive and so therefore are not accessible by many people in the world.

I suppose the next step would be to ask what kind of results you’ve seen in the biosimilars in application.

This particular trial randomised women who had untreated metastatic HER2 positive breast cancer to receive a taxane chemotherapy, either docetaxel or paclitaxel, in combination with either the proposed trastuzumab biosimilar or Herceptin. Patients were treated for eight cycles and as long as they had stable or responding disease you could drop the chemotherapy drug to avoid excessive toxicity and continue the antibody alone until progressive disease. What we reported today in the press conference was the overall response rates which were, by regulatory guidance, the endpoint that we were to look for to establish equivalency. The FDA looked for a ratio of overall response rate from the proposed biosimilar to the branded product and the EMEA, the European regulatory agency, looked for a difference. Both of those factors fell within the established equivalency guidelines. We also looked at safety and the safety was equivalent. We looked at cardiac function, which was also equivalent, and we looked at immunogenicity and pharmacokinetics, which were equivalent.

It sounds like these are all very good ideas generally then?

Yes, it does appear that this proposed trastuzumab biosimilar has met the regulatory requirements for equivalency or similarity. Of course the data will now be submitted for regulatory review to see what happens.

You mentioned the cost briefly, how would you see things shaping up for biosimilars approaching the generic alternative to the brand marketed, for example the named Herceptin?

I don’t really have any idea how the cost will compare and I think it’s been the subject of great speculation and we’ll all follow it with interest.