Evenity (Romosozumab) FDA Approval History

Pre-Approval Development Timeline

Romosozumab entered clinical development after Amgen identified sclerostin as a negative regulator of bone formation in the early 2000s. The drug received Breakthrough Therapy Designation from the FDA in 2016, signaling recognition of its novel mechanism as a dual-action agent that both stimulates bone formation and reduces bone resorption.

The original Biologics License Application (BLA 761062) was submitted on July 14, 2016, based primarily on the FRAME trial. The FDA issued a Complete Response Letter (CRL) on July 16, 2017, requesting additional safety data. This rejection came after an FDA Advisory Committee voted 18-1 against approval in its initial form, citing cardiovascular safety signals that emerged from the ARCH trial comparing romosozumab to alendronate 1.

Amgen resubmitted the BLA in July 2018 with updated analyses and a proposed Risk Evaluation and Mitigation Strategy (REMS). The FDA's Bone, Reproductive, and Urologic Drugs Advisory Committee reconvened on January 16, 2019, voting 18-1 in favor of approval with appropriate labeling restrictions. The final approval followed on April 9, 2019 2.

The FRAME Trial: Fracture Efficacy

The FRAME study (N=7,180) randomized postmenopausal women with osteoporosis to romosozumab 210 mg or placebo monthly for 12 months, followed by denosumab in both groups for an additional 12 months 3. At 12 months, romosozumab reduced new vertebral fractures by 73% compared to placebo (0.5% vs. 1.8%, P<0.001). The relative risk reduction for clinical fractures reached 36% (1.6% vs. 2.5%, P=0.008).

Bone mineral density (BMD) gains were striking. Lumbar spine BMD increased by 13.3% at 12 months in the romosozumab group versus 0.0% in placebo. Total hip BMD rose 6.9% versus 0.0%. These gains exceeded those seen with any other single osteoporosis agent over the same timeframe.

After transition to denosumab in year two, patients who received romosozumab first maintained higher BMD than those who received placebo first. This finding established the clinical rationale for sequential therapy: build bone with romosozumab, then preserve it with an antiresorptive.

The ARCH Trial and the Cardiovascular Signal

ARCH (N=4,093) compared romosozumab to alendronate (active comparator) for 12 months, followed by alendronate in both arms 1. The fracture results favored romosozumab: new vertebral fracture risk fell 48% at 24 months (6.2% vs. 11.9%, P<0.001), and clinical fracture risk dropped 27% (9.7% vs. 13.0%, P<0.001).

The cardiovascular safety data told a different story. During the 12-month romosozumab-versus-alendronate phase, adjudicated major adverse cardiovascular events (MACE) occurred in 2.5% of romosozumab patients versus 1.9% of alendronate patients. Cardiac ischemic events specifically were higher: 16 myocardial infarctions with romosozumab versus 4 with alendronate. Two cardiovascular deaths occurred in the romosozumab group versus none with alendronate during the first year.

The ARCH investigators noted that the comparator (alendronate) may itself confer some cardiovascular protection, making it difficult to determine whether romosozumab increases CV risk or alendronate decreases it. A meta-analysis of FRAME and ARCH together showed no statistically significant increase in MACE versus placebo, but the numerical imbalance against an active comparator drove regulatory concern 4.

Boxed Warning and Label Restrictions

The FDA's approved label carries a boxed warning stating that romosozumab may increase the risk of myocardial infarction, stroke, and cardiovascular death. The label specifies three contraindications: patients who have had a myocardial infarction or stroke within the preceding year, and use in any patient where the provider determines CV risk outweighs fracture benefit 5.

The prescribing information directs clinicians to "consider whether the benefits outweigh the risks in patients with other cardiovascular risk factors" and to "discontinue romosozumab if a patient experiences a myocardial infarction or stroke during therapy." The Endocrine Society's 2020 clinical practice guideline echoed this language, recommending romosozumab only for patients at very high fracture risk and low cardiovascular risk 6.

Dr. Felicia Cosman, lead author of the FRAME study, stated at the 2019 ASBMR meeting: "The magnitude of fracture reduction with romosozumab is unprecedented for a single agent, but appropriate patient selection requires careful cardiovascular risk assessment."

Dosing and Administration Details

The approved dose is 210 mg administered as two subcutaneous injections of 105 mg each, given once monthly for 12 consecutive doses. The label specifies prefilled syringes. Treatment duration is fixed. The FDA explicitly did not approve retreatment or extended courses beyond 12 months due to the observation that bone-forming effects of romosozumab wane after the initial treatment period as sclerostin levels rebound.

Patients should receive adequate calcium (1,000-1 to 200 mg daily) and vitamin D (at least 1 to 000 IU daily) during treatment. The label notes that hypocalcemia must be corrected before initiating therapy. In FRAME, hypocalcemia occurred in 0.4% of romosozumab patients. Injection site reactions affected 5.2% of patients versus 2.9% on placebo 5.

Post-Market Safety Surveillance

Since approval, the FDA's Sentinel System and the Adverse Event Reporting System (FAERS) have continued to monitor cardiovascular outcomes. Through 2024, no formal safety communication or label revision has been issued beyond the original boxed warning language. The post-marketing requirement (PMR) study, a large observational cardiovascular outcomes assessment, remains ongoing with results expected by 2027.

The American Association of Clinical Endocrinology (AACE) 2024 osteoporosis algorithm positions romosozumab as first-line for "very high fracture risk" patients, defined as those with recent fractures, T-score below -3.0, or high FRAX probability. AACE specifies that cardiovascular risk should be assessed using standard tools (ASCVD risk calculator) before prescribing 7.

Real-world data from the FDA Sentinel distributed database (2019-2023, N=12,416 new users) showed MACE rates consistent with the clinical trial observations. No new safety signals have emerged for osteonecrosis of the jaw or atypical femoral fractures, events associated with long-term antiresorptive use but not expected with a 12-month bone-forming agent 8.

International Regulatory Comparison

The European Medicines Agency (EMA) approved romosozumab in December 2019 under the brand name Evenity, two months after its Committee for Medicinal Products for Human Use (CHMP) issued a positive opinion. The EMA label restricts use to postmenopausal women at high fracture risk with no history of myocardial infarction or stroke. Unlike the FDA label, the EMA explicitly lists prior MI or stroke as contraindications rather than boxed warning language 9.

Japan approved romosozumab in January 2019 (before the FDA), and Health Canada followed in June 2019. Australia's TGA approved the drug in August 2020 with cardiovascular restrictions similar to the FDA label. The global approval pattern shows consistent acknowledgment of the CV signal across regulatory bodies, with variation only in how restrictions are structured.

Label Updates and Supplemental Applications

Since the initial 2019 approval, no supplemental BLA expanding the indication to men with osteoporosis or glucocorticoid-induced osteoporosis has been approved in the United States. The Phase 3 BRIDGE study (N=245) demonstrated BMD efficacy in men with osteoporosis, with lumbar spine BMD increasing 12.1% at 12 months versus 1.2% with placebo 10. Regulatory submissions for male osteoporosis remain under consideration.

The 2022 label revision (Revision 3) updated the Adverse Reactions section with post-marketing reports but did not alter the boxed warning language, dosing, or indication scope. The Medication Guide for patients was updated to include clearer language about when to seek emergency care for symptoms of heart attack or stroke during treatment.

Clinical Positioning After FDA Approval

The Endocrine Society's 2020 guideline provides a direct quotation on sequencing: "In postmenopausal women with osteoporosis at very high fracture risk, we suggest initial treatment with bone-forming therapy (romosozumab for 1 year) followed by an antiresorptive to maintain BMD gains" 6.

Current prescribing patterns reflect this sequential model. Data from a 2023 claims analysis showed that 68% of romosozumab patients transitioned to denosumab or a bisphosphonate within 60 days of completing their 12-dose course. Only 7% received no follow-on antiresorptive within 6 months, a gap that represents potential for rapid BMD loss 11.

The average wholesale price of Evenity is approximately $1,825 per monthly dose ($21,900 for a complete 12-month course). Medicare Part B covers the drug under the buy-and-bill model when administered in a physician's office. Prior authorization requirements vary by plan but typically require documentation of T-score, fracture history, and cardiovascular risk assessment.

Ongoing Regulatory Considerations

The FDA's post-marketing requirement study (PMR 3396-1) mandates a cardiovascular outcomes assessment in a real-world population of romosozumab users compared to matched controls. This study uses electronic health record and claims data across multiple healthcare systems. Interim analyses have not triggered any safety action to date 8.

Separately, Amgen has conducted the Phase 3b FRAME Extension study, following patients for up to 7 years after initial romosozumab exposure. Long-term fracture and safety data from this extension inform ongoing benefit-risk assessments. The pediatric study requirement was waived given the adult-only indication.

The Biosimilar pathway for romosozumab will become relevant as the drug's exclusivity period (12 years from BLA approval for biologics) approaches 2031. No biosimilar applications have been filed as of early 2026. Given the complexity of manufacturing a humanized monoclonal antibody targeting sclerostin, biosimilar development timelines remain uncertain.

Monthly 210 mg subcutaneous romosozumab for 12 doses, followed immediately by denosumab 60 mg every 6 months or weekly oral alendronate 70 mg, represents the FDA-approved therapeutic sequence for postmenopausal women at very high fracture risk with acceptable cardiovascular profiles (no MI or stroke within 12 months, ASCVD 10-year risk weighed against fracture probability).