It may not have been immediately obvious but Novartis’ Q2 results contained an important piece of previously unknown information.

The results came out this morning and revealed that the FDA rejected its copycat version of the Neulasta drug, made by Amgen. The biosimilar, which was made by Novartis’ Sandoz unit, applied for the same license as the Amgen drug, writes Ben Adams for Fierce Biotech.

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Novartis application rejected by U.S. regulators

Neulasta is a long-acting granulocyte colony stimulating factor. It is used to boost white blood cells in cancer patients that are going through chemotherapy treatment and is one of the top-selling products made by Amgen.

The drug has around $5 billion in sales, and much of that comes from the United States. The FDA accepted Novartis’ biosim application for the drug last November, but the company’s Q2 results reveal that it has now been rejected.

Novartis said: “Sandoz received a complete response letter from the FDA for biosimilar pegfilgrastim candidate (Neulasta). We are working with the agency to address remaining questions.” The brief update provided no further details.

Wider biosim industry could be impacted

Not only does the news come as a blow to Novartis, but it could impact other biosim manufacturers. For a while it had seemed that the regulatory environment had become more predictable, but this latest decision introduces a great degree of uncertainty once more.

In 2016 there have been multiple issues involving patent disputes as each company tries to block the other. In July FDA advisory committees approved new, separate biosimilars from both Novartis and Amgen, and a final decision is expected by the end of the year.

However complete response letters have been sent to other companies such as Pfizer’s Hospira unit. The FDA rejected Hospira’s biosim version of Epugen, Amgen’s kidney disease drug, last year. Both companies have been asked to provide more data before resubmitting their application later this summer.

European regulators approved biosim drug in February

In 2015 the first biosim approval in the United States was granted to Novartis for its copy of Amgen’s Neupogen, another chemotherapy side effects drug. At this stage it is not clear what the Sandoz issues concern, be it worries over manufacturing or clinical trials.

Sandoz previously released a statement when the FDA accepted its application. The unit said that three clinical trials had been carried out on the biosimilar. The first was a pharmacokinetic and pharmacodynamic study in volunteers of full health and two comparative efficacy and safety studies in patients with breast cancer (PROTECT 1 and 2).

It said these “demonstrate that the proposed biosimilar is highly similar to the reference product.” In February the biosim drug was approved by the European Medicines Agency.

Novartis CMO and head of drug development, Vasant Narasimhan, spoke during the Q2 call. “We received the complete response letter from FDA at the end of June. And we have worked closely with the agency throughout this program and are continuing to work with the agency to determine how best answer their questions,” he said, without going into further detail.

The news is encouraging for Amgen, which has seen its drugs subjected to various biosim applications. Even if the Novartis biosim is eventually accepted, the recent rejection means that Amgen gets to keep the bounty from Neulasta to itself for at leat a while longer.