Amgen Settles Patent Dispute with Celltrion, Paving Way for Denosumab Biosimilars

Amgen has reached a settlement with South Korean pharmaceutical company Celltrion, resolving patent litigation and potentially accelerating the launch of biosimilar versions of Amgen's blockbuster bone drugs Prolia and Xgeva (denosumab). This agreement, announced late last week, marks the second such settlement following a similar accord between Amgen and Sandoz in spring 2023.

Settlement Details and Market Implications

Under the terms of the settlement, Celltrion acknowledged the validity of Amgen's denosumab patents in the United States and admitted that its biosimilar candidates would infringe upon these patents. In exchange, Celltrion has secured the right to launch its biosimilar versions, Stoboclo and Osenvelt, as early as June 1, 2025.

This development comes on the heels of Sandoz's FDA approval for its own denosumab biosimilars, Jubbonti and Wyost, in March 2023. Sandoz is poised to introduce these products to the U.S. market on May 31, 2025, or potentially earlier under certain conditions, as per their agreement with Amgen.

The impending arrival of multiple biosimilars is set to reshape the competitive landscape for denosumab products, which have been significant revenue drivers for Amgen. In the first three quarters of 2024, Prolia generated $2.1 billion in U.S. sales, while Xgeva contributed approximately $1.1 billion.

Regulatory Landscape and Competitive Positioning

While Sandoz has already secured FDA approval for its biosimilars, Celltrion's regulatory status in the U.S. remains pending. The company submitted its biosimilar application to the FDA in November 2023, according to reports from Business Korea. However, Celltrion's products have already received regulatory endorsements in the European Union and Korea.

The denosumab biosimilar market is becoming increasingly crowded, with several other pharmaceutical companies vying for a share. Organon, Teva, Fresenius Kabi, and Samsung Bioepis have all filed applications for Prolia and Xgeva biosimilars with the FDA. Amgen has responded by initiating patent infringement lawsuits against some of these companies, including Samsung Bioepis and Fresenius Kabi.

Market Strategies and Future Outlook

As the February 2025 expiration of a key U.S. patent for denosumab approaches, companies are positioning themselves for market entry. Sandoz's biosimilars, Jubbonti and Wyost, hold a unique advantage as the first FDA-approved interchangeable biosimilars for Prolia and Xgeva. This designation allows pharmacists to substitute these products for the reference drugs without prescriber approval, similar to the process for small-molecule generics.

Celltrion, while currently lacking FDA approval, may leverage its existing partnership with Costco to gain a competitive edge upon market entry. The company's Humira biosimilar was previously added to Costco's Member Prescription Program, a drug discount initiative for eligible Costco members and their dependents.

As the denosumab patent cliff approaches, the pharmaceutical industry is bracing for significant changes in the osteoporosis and oncology treatment landscapes. The introduction of multiple biosimilars is expected to increase patient access to these important therapies while potentially reducing healthcare costs.