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FDA Approval: Interchangeability of Celltrion's Biosimilars

On October 29, 2025, the U.S. Food and Drug Administration (FDA) officially granted interchangeability designations to two biosimilars by Celltrion, Inc.: STOBOCLO® and OSENVELT® (both denosumab-bmwo). This significant step means that both biosimilars can be substituted for their reference counterparts, PROLIA® and XGEVA® respectively, without needing to consult the prescriber, provided state laws allow.

Enhancing Accessibility

The designation comes as part of a broader initiative to improve patient access to essential medicines and to increase provider choice when treating conditions such as osteoporosis and cancer-related bone loss. Thomas Nusbickel, Chief Commercial Officer at Celltrion USA, emphasized the importance of this designation: "Today's IC designations reinforce confidence in STOBOCLO and OSENVELT among physicians and pharmacists, facilitating a more seamless switch from the reference products to our denosumab biosimilars."

This move aligns with the growing need for affordable treatment options in the healthcare system, particularly for patients dealing with serious skeletal diseases.

Clinical Evidence and Safety

The FDA's decision was supported by comprehensive clinical data, including pharmacokinetics, efficacy, safety, and an immunogenicity study focused on postmenopausal women diagnosed with osteoporosis. Phase III trials showcased the therapeutic equivalence of these biosimilars compared to their reference drugs.

Celltrion's biosimilars became available in the U.S. market in July 2025, with STOBOCLO coming in a 60 mg/mL injection form and OSENVELT available in a 120 mg/1.7 mL (70 mg/mL) injection. The interchangeability designation enhances the potential for patients to receive treatment that fits their needs while also providing financial relief to the healthcare system.

Indications for Use

STOBOCLO is indicated for several conditions, including:

• - Treatment of postmenopausal women at high risk for osteoporosis-related fractures.
• - Increasing bone mass in men with osteoporosis at risk for fracture, as well as in men receiving androgen deprivation therapy for nonmetastatic prostate cancer.
• - Managing glucocorticoid-induced osteoporosis in high-risk patients.
• - Increasing bone mass in women undergoing adjuvant aromatase inhibitor therapy for breast cancer.

For OSENVELT, the indications include:

• - Prevention of skeletal-related events in multiple myeloma and in patients with bone metastases from solid tumors.
• - Treatment of adults and skeletally mature adolescents with unresectable giant cell tumors of bone.
• - Management of hypercalcemia of malignancy that is unresponsive to bisphosphonate therapy.

Safety Alerts

While these biosimilars represent significant advancements, potential users should be aware of safety information associated with them. Severe hypocalcemia can occur, particularly in patients with advanced kidney disease and other specific conditions. Regular monitoring and preventive measures are recommended to manage potential side effects effectively.

Conclusion

The introduction of the interchangeability designation for Celltrion's biosimilars STOBOCLO and OSENVELT marks a key development in improving treatment options for patients suffering from osteoporosis and related conditions. This advancement not only enhances accessibility to vital treatments but also signifies a commitment to ensuring that more patients can receive the reliable and affordable care they deserve. As healthcare continues to evolve, such steps take us closer to achieving better health outcomes for all.