Interchangeability key to US biosimilars market says expert

By Gareth Macdonald

- Last updated on GMT

US FDA developing bulletproof guideline says Woodcock
US FDA developing bulletproof guideline says Woodcock

Related tags Food and drug administration

Interchangeability can create long-lasting price competition in the nascent US biosimilars market according to a Berkeley health policy expert. 

The launch of the Neupogen (filgrastim) copycat Zarxio (filgrastim-sndz) this month established the US biosimilars market, but it is unlikely to have defined it.

Sandoz’s drug was approved as biosimilar to rather than ‘interchangeable’ with Amgen’s white blood cell booster and it is the latter classification that will drive market dynamics says Francis Megerlin from the Berkeley Center for Health Technology.

Patients treated with interchangeable products are not captive of a given brand. As a consequence, and according to states law that govern substitution, there could be a long-lasting competition for chronic treatments​” he told

Megerlin suggested interchangeable biosimilars may provide insurers with the opportunity to drive down prices.

Insurers have an interest to enter and negotiate prices in the most competitive corridor, which would be defined according to the number of products competing, and by state laws that govern substitution​.”

Megerlin – who set out predictions for the US biosimilar market in an oft-cited 2013 paper​ – said quantifying the impact interchangeable biosimilars will have on prices is difficult, particularly as the concept is unique to the US market.


The US FDA can designate a biosimilar product as interchangeable​ if a sponsor can prove it is “expected to produce the same clinical result as the reference product in any given patient​” and that switching between the two is safe.

However, as yet the US Agency has not defined how a sponsor must go about generating such proof, although it is working on guidance.

Speaking at a Senate Subcommittee meeting yesterday, CDER director Janet Woodcock said the FDA is keen to get the “science right​” and make it "bulletproof​" in response to a grilling about why no guidelines had been developed in the five years since the BPCI Act became law​.

Market-to-market variation

Even if interchangeability considerations are set aside, it is hard to estimate how much cheaper a biosimilar will be than its reference drug as the prices vary market-to-market.

Pfizer’s unit Hospira​ was contracted by France’s Assistance Publique to supply its version of Merck & Co’s Remicade (infliximab) at a 45% discount to the originator. However, in Norway the same drug sells for 69% less than the Merck original.

In the US, Zarxio sells for 15% less than the Amgen innovator.

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