⚠ EVENITY's Antibody Patent Ended in April 2026Moderate threat

Amgen (AMGN) — threat to the moat

EVENITY's antibody patent expired in April 2026, leaving formulation and treatment patents to defend a $2.1 billion drug.

EVENITY is growing into a thinner patent position than its sales suggest. Amgen's 10-K lists the United States patent on the EVENITY antibodies as expiring on 25 April 20261. What remains are a formulation patent to May 2031 and a treatment patent to April 20332.

EVENITY patent dates in the United StatesApr 2026antibodiesMay 2031formulationApr 2033methods of treatmentAmgen Form 10-K FY2025, patent table
The molecule patent has already gone.

Biologics also carry regulatory exclusivity in America, which prevents a biosimilar from being approved for a period after the original's approval, so the lapse of the antibody patent does not open the market at once. But the defence has moved from the molecule to how it is made up and used, which a biosimilar maker can challenge.

Amgen knows the pattern from the other side. Its own bone drug Prolia lost its RANKL antibody patents in February 2025 in the United States3, and by the second quarter of 2026 its sales were down 32% as multiple biosimilars launched globally with more biosimilars expected4. EVENITY sold $2,100 million in 20255, which makes it a worthwhile target.

The profit is also split. UCB shares commercialization profits and losses equally6, so Amgen's economic exposure is half the sales line, and so is its loss if copies arrive.

The date to watch is the first biosimilar application for romosozumab. When one is filed, the formulation and treatment patents will be tested in litigation, and EVENITY's growth of 38% in the second quarter of 20267 will begin to count down toward the same cliff Prolia is now falling from.

References
  1. ReportedAmgen's 10-K lists the United States patent on the EVENITY antibodies as expiring on 25 April 2026.
    Amgen Form 10-K for fiscal 2025 - Item 1 patents, biosimilars and competitors. — FY2025 · publ. 13 February 2026 · source ↗
  2. ReportedWhat remains are a formulation patent to May 2031 and a treatment patent to April 2033.
    Amgen Form 10-K for fiscal 2025 - Item 1 patents, biosimilars and competitors. — FY2025 · publ. 13 February 2026 · source ↗
  3. ReportedIts own bone drug Prolia lost its RANKL antibody patents in February 2025 in the United States, and by the second quarter of 2026 its sales were down 32% as multiple biosimilars launched globally with more biosimilars expected.
    Amgen Form 10-K for fiscal 2025 - Item 1 patents, biosimilars and competitors. — FY2025 · publ. 13 February 2026 · source ↗
  4. ReportedIts own bone drug Prolia lost its RANKL antibody patents in February 2025 in the United States, and by the second quarter of 2026 its sales were down 32% as multiple biosimilars launched globally with more biosimilars expected.
    Amgen second-quarter 2026 results release, Form 8-K exhibit 99.1 - product sales performance: Repatha, EVENITY, Prolia and XGEVA. — Q2 2026 · publ. 4 August 2026 · source ↗
  5. ReportedEVENITY sold $2,100 million in 2025, which makes it a worthwhile target.
    Amgen fourth-quarter and full-year 2025 results release, Form 8-K exhibit 99.1 - product sales for 2024-2025, non-GAAP EPS and 2026 guidance. — FY2025 · publ. 3 February 2026 · source ↗
  6. ReportedUCB shares commercialization profits and losses equally, so Amgen's economic exposure is half the sales line, and so is its loss if copies arrive.
    Amgen Form 10-K for fiscal 2025 - Item 1 business: products, collaborations, staff and pipeline. — FY2025 · publ. 13 February 2026 · source ↗
  7. ReportedWhen one is filed, the formulation and treatment patents will be tested in litigation, and EVENITY's growth of 38% in the second quarter of 2026 will begin to count down toward the same cliff Prolia is now falling from.
    Amgen second-quarter 2026 results release, Form 8-K exhibit 99.1 - product sales performance: Repatha, EVENITY, Prolia and XGEVA. — Q2 2026 · publ. 4 August 2026 · source ↗
Sources
Generated September 28, 2026