FDA Approves Enoby and Xtrenbo Biosimilars for Bone Health and Cancer Care

The U.S. Food and Drug Administration (FDA) has approved two new biosimilars for denosumab-qbde: Enoby (denosumab-qbde) and Xtrenbo (denosumab-qbde), according to a news release from Gedeon Richter Plc. (“Richter”) and Hikma Pharmaceuticals Plc. These medicines reference the therapeutics Prolia and Xgeva and are designed to provide patients with safe and effective alternatives at potentially lower costs.

According to the American Cancer Society, a biosimilar is a lower-cost alternative to a specific drug, such as therapies used in cancer treatment. Although biosimilars are not identical copies of the original medication, they are highly comparable and must meet FDA standards to confirm that they are equally safe and effective as the brand-name biologic, improving access to important therapies and reducing overall treatment costs.

“We are proud to be able to bring these biosimilar options to healthcare providers and patients, improving affordability and access to these important therapies,” said Dr. Bill Larkins, president of Hikma Injectables, in the news release. “We will use our strong and well-established commercial capabilities to bring these products to patients.”

Enoby is approved for patients receiving hormone-based therapies for breast or prostate cancer, which can weaken bones over time. By targeting a protein called RANKL, Enoby helps reduce bone loss, making bones stronger and lowering the chance of fractures.

Xtrenbo is approved for patients with cancer that has spread to the bones, as these patients are at increased risk for skeletal complications. This includes people with solid tumors, multiple myeloma, or those with rare conditions such as giant cell tumor of the bone. Xtrenbo is also used to manage hypercalcemia of malignancy, a serious condition where cancer causes dangerously high calcium levels in the blood that do not respond to other therapies.

How Do the Enoby and Xtrenbo Biosimilars Work?

Both Enoby and Xtrenbo contain denosumab, a monoclonal antibody that works by blocking RANKL, a protein that triggers cells called osteoclasts to break down bone. By inhibiting this interaction, denosumab preserves bone density, reduces bone resorption and helps protect against painful or dangerous bone complications.

Enoby is administered as a subcutaneous (under the skin) injection every six months. To maximize bone protection, patients are advised to take daily calcium and vitamin D supplements alongside treatment.

Xtrenbo, also given as a subcutaneous injection, is typically administered every four weeks. In some conditions, patients may receive additional doses during the first month of treatment. As with Enoby, calcium and vitamin D supplementation is used to lower the risk of low calcium levels in the blood.

What Safety Information Should Patients Know About Enoby and Xtrenbo?

Enoby carries an FDA boxed warning label about severe hypocalcemia (low calcium levels), especially in patients with advanced kidney disease. For those with chronic kidney disease, healthcare providers will check for mineral and bone disorders before starting therapy and monitor calcium closely during treatment.

Both Enoby and Xtrenbo may cause side effects. The most common include back pain, muscle or joint pain, infections, skin rashes and gastrointestinal symptoms. Rarer side effects include osteonecrosis of the jaw, which can lead to delayed healing after dental work and atypical femoral fractures. Patients should notify their healthcare team if they experience thigh or groin pain, jaw problems or signs of infection such as fever, swelling or redness.

Pregnancy should be avoided during therapy and for at least five months after the last dose, as denosumab may harm an unborn baby. Patients considering treatment should discuss family planning with their doctors.

Expanding Patient Access to the Enoby and Xtrenbo Biosimilars

The approvals of Enoby and Xtrenbo represent a step forward in making bone-strengthening and cancer-supportive therapies more affordable and accessible, according to the news release.

For individuals living with advanced cancers that affect the skeleton or rare bone tumors, these biosimilars provide new treatment choices backed by the FDA’s review process. By offering similar quality, Enoby and Xtrenbo may help more patients access essential therapies without compromise, the news release concludes.

“The approvals of Enoby and Xtrenbo represent a significant milestone accomplishment for Richter, as our first FDA approved biosimilars. They are a testimony to Richter’s ambition in providing affordable biosimilar access in important therapies to patients across the globe and establishing Richter as a high-quality biosimilar developer and manufacturer.” Dr. Erik Bogsch, head of Biotechnology Business Unit at Richter, concluded.

References

1. “Hikma and Richter receive FDA approval for denosumab biosimilars EnobyTM (denosumab- qbde) and XtrenboTM (denosumab- qbde) referencing Prolia® and Xgeva® respectively,” by Gedeon Richter Plc. (“Richter”) and Hikma Pharmaceuticals Plc. News release; Oct. 1, 2025.
2. “Biosimilar Medicines,” by the American Cancer Society. https://www.cancer.org/cancer/managing-cancer/treatment-types/biosimilar-drugs.html

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