Celltrion has elbowed its way into Amgen’s denosumab stronghold, rolling out its dual-brand biosimilar Stoboclo and Osenvelt across the United States just weeks after Sandoz’s own copycats hit pharmacy shelves. 

The drugs are biosimilar versions of Prolia and Xgeva, used to treat osteoporosis and bone complications from cancer, respectively.

The Korean drugmaker received full-label FDA approval in March and cleared a launch path through a January settlement with Amgen, which resolved ongoing patent litigation. The agreement allowed Celltrion to launch as early as June 1 and included the company’s acknowledgment that its biosimilars infringed valid U.S. patents.

Stoboclo and Osenvelt arrive with a 5 percent discount to Amgen’s Prolia and Xgeva, which racked up $6.6 billion worldwide last year, two-thirds of it in the U.S. Celltrion is distributing the drugs directly through its U.S. subsidiary, following the same strategy used for its infliximab, adalimumab and ustekinumab biosimilars.

At launch, Celltrion said it secured supply deals with major hospital systems and is targeting the U.S. “open market,” which represents around 30 percent of denosumab sales and is less influenced by pharmacy benefit managers (PBMs). The company says it is also in active negotiations with the top three PBMs to gain access to Medicare and commercial formularies.

Samsung Bioepis is next in line. The company won FDA approval in February for its denosumab biosimilars Ospomyv and Xbryk, and is preparing to enter the U.S. market now that Amgen’s patent protections have officially expired.

Meanwhile, Celltrion previously captured 6 percent of the open market with its bevacizumab biosimilar Vegzelma and is aiming to replicate that performance in bone disease.