The moment that we (biosimilars enthusiasts) have all been waiting for has finally arrived! Sandoz has    become the first company to disclose filing of a biosimilar application in the United States. On July 24, 2014, Sandoz announced that the FDA had accepted its application for approval of filgrastim (referencing Amgen's Neupogen) via the previously unused biosimilar (aka 351[k]) pathway.

Is it likely to be approved?

Yes! Sandoz has been selling the same filgrastim product in over 40 countries, under the brand name Zarzio, for several years with no major unexpected safety events reported. Oncologists that we have surveyed in Europe who use the drug say it has the same safety and efficacy as Neupogen and it is the most-preferred biosimilar filgrastim. On top of that, Sandoz claims to be the class leader with 30 percent volume share, so there are no red flags about the product from the current market experience.

From a regulatory point of view in the United States, there is still an element of uncertainty; the FDA has not provided product-specific guidance on what it expects in a biosimilar filgrastim dossier (unlike the EMA), but the U.S. agency's general guidance is similar to that of the EMA's and Sandoz will have had several meetings with the FDA throughout its development program. Sandoz has tested the drug in four Phase I trials in healthy volunteers plus a Phase III trial in breast cancer patients receiving myelosuppressive chemotherapy using U.S.-sourced reference product. We assume Sandoz is seeking approval for all five of Neupogen's indications, so perhaps the biggest question mark remains over whether the FDA will permit full indication extrapolation (approving a biosimilar for reference-brand indications that the biosimilar has not been tested in). We continue to believe that this is highly likely given that the mechanism of action of filgrastim is the same across its five approved indications, and because there is a well-defined pharmacodynamic marker for its efficacy.

The only other potential obstacle to market entry would be Neupogen patents. One of the downsides for companies choosing to file through the biosimilar pathway, rather than opting for the full BLA route (351[a]), is that they must submit their entire dossier to the reference sponsor's legal team. They must then embark on a series of meetings designed to resolve any outstanding patent issues in parallel with the FDA's regulatory review. The material patent for Neupogen expired in December 2013, enabling Teva to launch its own filgrastim product, Granix (tbo-filgrastim), via the full BLA pathway in 2013. Assuming that Sandoz has managed to avoid infringing any of Amgen's other patents, we see no reason that Sandoz should not become the first company to launch a biosimilar in the United States in the next 10 to 12 months.

What will it be called?

This is a particularly topical question. Recently, the FDA has been going somewhat off piste with its biologic naming. The prefixes that the FDA has attached to USANs for drugs like Teva's Granix (tbo-filgrastim), Roche's Kadcyla (ado-trastuzumab emtansine), and Sanofi's Zaltrap (ziv-aflibercept), are not endorsed by the WHO (the body that issues INNs), but were adopted by the FDA to avoid prescribing errors. However, it is yet unknown whether the FDA is expecting to use the same prefix system for biosimilars because its long-awaiting biologic nomenclature policy is yet to be published, although it is planned for this year. Therefore, we still do not know what the non-proprietary name will be for Sandoz's filgrastim; we assume that Sandoz will adopt a brand name in the U.S. to aide pharmacovigiliance, perhaps Zarxio which was recently registered as a trademark for the company.

What's the commercial opportunity?

A lot of excitement in the biosimilars industry at the moment is focused on monoclonal antibodies; these really do hold the potential to cause a dramatic shift in the commercial potential of the biosimilars industry given that several multi-billion dollar MAbs will go off patent soon. Filgrastim is not one of these. However, the reference product, Neupogen, generated $1.2B in U.S. revenue last year, which presents a reasonable opportunity for biosimilar competitors. By five years post launch of follow-on filgrastim products, we believe Neupogen could have lost half of its market share.

What's the competition like?

As mentioned, Teva has already launched a filgrastim product (Granix) in the United States. Although this molecule was approved as a biosimilar in Europe and Japan, it was approved via a full BLA in the United States (for historical rather than strategic reasons). Granix's head start on Sandoz's filgrastim, could be dented by a couple of important differences between a biosimilar and full BLA-approved brand.

Firstly, Granix was ineligible for indication extrapolation and therefore is only approved for reducing neutropenia in non-myeloid malignancy patients receiving myelosuppressive chemotherapy. In order for Teva to expand Granix label, the company would need to invest in further clinical trials, impacting the profitability of the drug and potentially its pricing flexibility. We expect Sandoz's filgrastim to have the same label as Neupogen.

Secondly, Medicare reimbursement rules will be more favorable to Sandoz biosimilar filgrastim than Teva's Granix. According to the Average Sales Price +6% rule, the value of reimbursement for a biosimilar will be its average selling price plus 6 percent of the reference brand's price. However, because Granix was not approved via the biosimilar pathway, reimbursement is calculated as the average selling price plus 6 percent of its own price, which is approximately 20 percent less than Neupogen. Hence, the reimbursement value will likely be lower for Granix than the biosimilar, incentivizing use of Sandoz's product.

But the true juggernaut facing both Sandoz's biosimilar filgrastim is Amgen's Neupogen. Decades on the market and tens of billions in historical revenue means not only are multiple generations of physicians familiar with Neupogen, but Amgen may have greater flexibility to price Neupogen defensively than many of the manufacturers of MAbs being targeted by biosimilars companies.

Granix and Neupogen are unlikely to be the only competition that Sandoz will face. Hospira already sells a filgrastim biosimilar (marketed as Nivestim) in Europe and Australia. The company has intimated that it will seek approval in the United States, although a timeline of additional trials, if any, has not been revealed. Apotex, on the other hand, has already completed a U.S. bridging study for its filgrastim biosimilar (Grastofil) that was in-licensed from the Indian company Intas. With at least five companies fighting it out for share of the U.S. filgrastim market, there is likely to be pressure on price, and on developing effective differentiation strategies to convince physicians and payers which filgrastim is best.

When will more biosimilars be filed in the United States?

We expect a small flurry of U.S. biosimilar applications now. The next filing could also be from Sandoz; back in April, the company indicated that it was preparing to file pegfilgrastim for approval in the United States as well. There is an outstanding patent on the reference product, Amgen's Neulasta, but this will expire in October 2015, so by the end of 2015, Sandoz could have two U.S. biosimilars in its portfolio.

Celltrion has also disclosed U.S. filing plans for its infliximab biosimilar, known as Remsima in most markets. This application could be more complicated however; Celltrion has challenged J&J's patents ahead of filing, but assuming this suit is unsuccessful, if Celltrion were to gain FDA approval next year, launch would be delayed until patent expiry in 2018.

The third likely early entrant to the U.S. biosimilar market is Hospira. The company's biosimilar epoetin alfa (Amgen's Epogen / J&J's Procrit) trials have taken longer than expected in the U.S., but an application is now slated for late 2014 or early 2015.

2015 will be a landmark year for the U.S. biosimilars industry!

On August 7, 2014, Kate will be hosting an analyst call entitled Coming to America: Sandoz Files the First Biosimilar in the United States, covering this topic in detail. Contact us for more information on how you can attend.

Kate Keeping is senior director of biosimilars research at Decision Resources Group.

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