The Same, But Different: Biosimilars May Rival Name-Brand Cancer Treatments

Biosimilars are likely to rival name-brand treatments for breast and other cancers, and the competition could drive prices down.
What’s new about the recently approved medication Zarxio? Nothing — and everything.

Zarxio (filgrastim-sndz) is an injectable medication that produces a vital effect; it stimulates bone marrow, increases white blood cell production and thus helps patients taking chemotherapy for breast or other cancers to fight off infection. It is also a breakthrough cancer medication for a very unusual reason: There’s absolutely nothing new about what Zarxio does or how it does it.

Zarxio mimics an older treatment called Neupogen (filgrastim), but unlike generic versions of typical name-brand drugs, it’s not 100 percent identical to Neupogen. That’s because Neupogen isn’t a traditional medicine that can be synthesized in any properly equipped lab or factory. It’s a genetically modified strain of E. coli bacteria that comes from a particular culture owned by a particular company. Zarxio is a different strain of modified E. coli — one that can still be distinguished from the original even though it has undergone such similar modifications that it also produces human granulocyte colony-stimulating factor and performs like Neupogen in trials.

Zarxio, therefore, is a breakthrough because it acts the same as Neupogen without actually being the same. Zarxio was the first so-called “biosimilar” approved for sale in the U.S., and it’s still the only such medication used in cancer treatment, but that’s probably about to change. Many of the most important cancer medications developed in the past 20 years are monoclonal antibodies that are just losing patent protection. Like Neupogen, they are complicated biological drugs that are developed in ways that cannot be copied precisely, so would-be competitors have created biosimilar rivals that are nearly ready for use. The difficulty of reproducing medications that are harvested rather than synthesized has led the U.S. Food and Drug Administration (FDA) to require more proof of safety and efficacy from biosimilars than generics. The generic approval process typically requires nothing more than chemical analysis. The biosimilar approval process requires most candidates to undergo chemical analysis and trials in both animals and humans.

Still, many companies are spending the money to develop and test biosimilar cancer medications. Amgen has already filed for permission to sell a biosimilar of Avastin (bevacizumab), an antibody drug that disables blood vessels needed to support a tumor and is approved for use in metastatic HER2-negative breast cancer in Europe and several other cancer types, including some gynecologic diseases, as well as some lung, colon and brain cancers. Both Amgen and Mylan have completed what they believe to be the last trials needed to receive approval for two different biosimilars of Herceptin (trastuzumab), another antibody that treats HER2-positive breast cancer. Novartis believes it has finished testing a biosimilar to Rituxan (rituximab), which is used to treat non-Hodgkin lymphomas. And a smaller company called Sorrento Therapeutics has announced results of phase 3 trials on a biosimilar of Erbitux (cetuximab), which treats squamous cell carcinoma of the head and neck, as well as certain colorectal cancers.

Evidence from Europe, which implemented a comparable biosimilar approval process a decade ago, suggests the FDA’s rules will ensure American patients that biosimilars are both as safe and as effective as the treatments they imitate. That said, neither the biosimilar trial process nor any biosimilar’s brief time on any market here in America provides the sort of overwhelming performance data that’s available for original medications.

How much will doctors and patients trust an approval process that deems biosimilars as effective as originals against all tumor types for which they’re approved, after comparing them against just one tumor type in trials?

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