Double Win With FDA’s Green Light Towards Two New Denosumab Biosimilars

The U.S. Food and Drug Administration (FDA) has approved Celltrion’s Steoboclo and Osenvelt for all indications of the reference products Prolia and Xgeva, respectively. This approval represents the third denosumab biosimilar, further increasing access to affordable biologics for osteoporosis and bone metastases treatment. Denosumab is a monoclonal antibody that targets the RANKL protein, which plays a crucial role in bone breakdown. By inhibiting RANKL, it helps prevent bone loss, increases bone density, and lowers the risk of fractures in patients.

Stobloco and Osenvelt Approved for Osteoporosis Treatment, Bone Fracture Prevention, and Bone Metastases Management

Regulators typically approve these products under two distinct names, each linked to a specific indication. Stobloco corresponds to Prolia, which is prescribed for osteoporosis patients. Osenvelt, on the other hand, references Xgeva, used to treat and prevent bone fractures in patients at higher risk due to bone metastases.

Doctors prescribe Stobloco for postmenopausal women with osteoporosis at high fracture risk. It also increases bone mass in men with osteoporosis at high fracture risk and in those receiving androgen deprivation therapy for nonmetastatic prostate cancer. Additionally, it treats glucocorticoid-induced osteoporosis in men and women at high fracture risk, and helps increase bone mass in women at high fracture risk undergoing adjuvant aromatase inhibitor therapy for breast cancer.

Doctors use Osenvelt to prevent skeletal-related events in patients with multiple myeloma and bone metastases from solid tumors. It also treats adults and skeletally mature adolescents with unresectable giant cell tumors of bone or where surgery could cause severe morbidity. Additionally, it addresses hypercalcemia of malignancy that is resistant to bisphosphonate therapy.

“The approval of STOBOCLO and OSENVELT is another step forward in our efforts to deliver cost-effective and high-quality treatments that address critical unmet needs in osteoporosis-related fracture as well as cancer-related skeletal events,” said Thomas Nusbickel, Chief Commercial Officer at Celltrion USA. “Patients deserve therapeutic options that have the potential to make real impacts on their care and their lives. We are committed to continuous innovation to meet these goals leveraging our experience and successful track record with biosimilar and novel biologics.”

FDA Approval Supported by Phase III Trial Data Showing Equivalent Efficacy and Safety of CT-P41

Strong clinical evidence, including Phase III trials in postmenopausal women with osteoporosis, supports the FDA approval. These studies assessed the efficacy, pharmacodynamics (PD), pharmacokinetics (PK), safety, and immunogenicity of CT-P41 compared to reference denosumab. Results showed that CT-P41 had equivalent efficacy and PD, with similar PK, safety, and immunogenicity profiles.

A study of 440 postmenopausal women with osteoporosis found that CT-P41 and US-sourced denosumab were equally effective in improving lumbar spine bone mineral density (BMD) at week 52. Both treatments also led to similar improvements in hip and femoral neck BMD, fracture rates, and quality of life scores.

Safety profiles were comparable, with a low incidence of antidrug antibodies and serious adverse events. However, some limitations included smaller sample sizes in certain groups and external disruptions affecting patient visits and dosing. Despite these challenges, the findings support CT-P41 as a safe and effective alternative to US-sourced denosumab.

The approval follows nearly a year after the first denosumab biosimilar received regulatory clearance. Wyost and Jubbonti (denosumab-bddz) were approved in March 2024, while Ospomyv and Obodence (denosumab-dssb) received approval in February 2025. Additionally, the European Commission granted approval for Stobloco and Osenvelt in late February 2025.

Jean-Yves Reginster, MD, PhD, director of the WHO Collaborating Centre for Epidemiology of Musculoskeletal Health and Aging, said in a statement, “Biosimilars have expanded into new therapeutic areas such as immunology, oncology and ophthalmology as they continue to offer significant cost-saving potential while expanding patient access. A denosumab product with a clinically proven track record in quality and safety is a valuable addition for my patients.”

First-ever Denosumab Biosimilar Approved After Thorough Physicochemical Tests & Biological Assays

The approval follows nearly a year after the first denosumab biosimilar received regulatory clearance. Wyost and Jubbonti (denosumab-bddz) were approved in March 2024, while Ospomyv and Obodence (denosumab-dssb) received approval in February 2025. Additionally, the European Commission granted approval for Stobloco and Osenvelt in late February 2025.

After a comprehensive review of scientific evidence, the FDA determined that Jubbonti and Wyost were highly similar to Prolia and Xgeva, with no clinically meaningful differences. The review included extensive physicochemical tests and biological assays, comparing multiple manufacturing lots of each product. These comparisons confirmed that Jubbonti and Wyost matched Prolia and Xgeva in structural and functional features, which are critical to safety and efficacy. 

Clinical studies further supported the approval, with a pharmacokinetic study showing similar drug exposure after a single subcutaneous injection, and a study in postmenopausal women with osteoporosis confirming comparable efficacy, safety, and immunogenicity. These findings led to the approval of Jubbonti and Wyost as interchangeable biosimilars.

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Denisse Sandoval