FDA Approves Stoboclo and Osenvelt as Biosimilars for Some Cancers

The U.S. Food and Drug Administration (FDA) has approved two new biosimilars as reference products for Prolia (denosumab) and XGEVA® (denosumab): Stoboclo (denosumab-bmwo) and Osenvelt (denosumab-bmwo), respectively, for all approved indications, according to a news release from Celltrion, Inc.

The American Cancer Society defines a biosimilar as a lower-cost alternative to a specific medication, including drugs used in cancer treatment. While biosimilars are not exact replicas of the original drug, they are highly similar and must meet FDA requirements to ensure they are just as safe and effective as the brand-name biologic, according to the organization’s website. By offering these alternatives, biosimilars help expand patient access to essential therapies and lower overall treatment costs.

The indications for these two biosimilars include treating postmenopausal women with osteoporosis at high risk of fracture, increasing bone mass in men with osteoporosis or men receiving hormone therapy for nonmetastatic prostate cancer, managing glucocorticoid-induced osteoporosis in men and women at high fracture risk, and increasing bone mass in women on aromatase inhibitors for breast cancer who are at high fracture risk.

This designation from the FDA means that Stoboclo and Osenvelt can be substituted at the pharmacy for the original medicines without needing to check with the prescriber first, depending on state rules, according to the news release.

"Today's interchangeability designations reinforce confidence in Stoboclo and Osenvelt among physicians and pharmacists, facilitating a more seamless switch from the reference products to our denosumab biosimilars,” Thomas Nusbickel, chief commercial officer at Celltrion USA, said in the news release. "Building on our strong heritage in biosimilars, Celltrion remains committed to offering more affordable and much-needed treatment options to patients living with skeletal diseases, creating greater potential to deliver savings to patients and the U.S. healthcare system."

The FDA based the interchangeability designations for Stoboclo and Osenvelt on strong phase 3 clinical research in postmenopausal women with osteoporosis, showing these medicines work like the original version and have similar effects on the body, safety and immune response.

Available in the U.S. since July 2025, Stoboclo and Osenvelt are injectable medicines. Stoboclo comes in a 60 milligrams per milliliter (mg/mL) dose, while Osenvelt is offered as a 120 mg/1.7 mL (70 mg/mL) dose.

The FDA recently proposed guidance that could make the process easier for biosimilars to be considered interchangeable. Instead of requiring extra studies, companies may be able to use the same data already included in their biologics license application. Previously, biosimilars needed switching studies to earn this status.

What is Stoboclo, and How Does it Work?

Stoboclo is a type of medicine called a RANKL inhibitor, similar to Prolia. The FDA approved Stoboclo 60 mg/mL injection based on strong data showing it works the same as Prolia. In the U.S., Stoboclo is approved for several uses: treating postmenopausal women and men with osteoporosis who are at high risk for fractures, treating glucocorticoid-induced osteoporosis in men and women at high risk for fractures, increasing bone mass in men receiving hormone therapy for nonmetastatic prostate cancer, and increasing bone mass in women receiving aromatase inhibitors for breast cancer who are at high risk for fractures.

How Safe is Stoboclo?

For postmenopausal osteoporosis, side effects reported in more than 5% of patients included back pain, pain in the arms or legs, high cholesterol, muscle or joint pain and urinary tract inflammation. Pancreatitis was also reported in clinical trials.

For men with osteoporosis, common side effects included back pain, joint pain and nasal or throat inflammation.

For glucocorticoid-induced osteoporosis, reported in more than 3% of patients, side effects included back pain, high blood pressure, bronchitis and headache.

For bone loss caused by hormone therapy for cancer, reported in 10% or more of patients, side effects included joint pain and back pain. Pain in the arms or legs and muscle or joint pain were also seen in clinical trials.

Reference

1. “U.S. FDA grants interchangeability designation to Celltrion's denosumab biosimilars, STOBOCLO® (denosumab-bmwo) and OSENVELT® (denosumab-bmwo).” Celltrion. News Release. Oct 30.
2. “Biosimilar Medicines,” by the American Cancer Society. https://www.cancer.org/cancer/managing-cancer/treatment-types/biosimilar-drugs.html

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