⚠ KRYSTEXXA Molecule Patent Ended in April 2026Moderate threat

Amgen (AMGN) — threat to the moat

The patent on KRYSTEXXA's molecule ended in April 2026, leaving a treatment patent to 2040 as the main defence.

KRYSTEXXA's first line of patent defence has already lapsed. Amgen's 10-K lists the United States patent on the KRYSTEXXA polypeptides as expiring on 11 April 20261. What remains is a patent on methods of treatment, including combination treatment, expiring in October 20402.

Horizon patent dates in the United StatesApr 2026KRYSTEXXApolypeptidesMar 2029TEPEZZAantibodies2032TEPEZZAbiologicexclusivityJan 2034TAVNEOSJun 2034UPLIZNAOct 2040KRYSTEXXAtreatmentAmgen Form 10-K FY2025, patent table
The first Horizon patent has already expired.

That is a thinner defence than it sounds. A composition patent stops anyone making the molecule. A method-of-treatment patent stops a copy being sold for the patented use, which a biosimilar maker can sometimes design around by seeking approval only for uses the patent does not cover. KRYSTEXXA is a biologic, so a copy still needs the lengthy biosimilar process; the lapse does not mean a copy is imminent.

Amgen knows what copies do. Its 10-K says that once multiple biosimilar versions of one of its originator products have launched, competition intensifies rapidly, resulting in accelerated net price declines for both the reference and the biosimilar products3. That sentence describes Prolia today.

KRYSTEXXA is small enough that a copy maker may not bother soon: $1,340 million in 20254. But it is growing, $400 million in the second quarter of 20265, and every quarter of growth makes it a more attractive target.

The event to watch is a biosimilar application for pegloticase. Its filing would start a clock of a few years on the one Horizon drug Amgen is growing fastest, and the treatment patent's strength would then be tested in court rather than assumed.

References
  1. ReportedAmgen's 10-K lists the United States patent on the KRYSTEXXA polypeptides as expiring on 11 April 2026.
    Amgen Form 10-K for fiscal 2025 - Item 1 patents, biosimilars and competitors. — FY2025 · publ. 13 February 2026 · source ↗
  2. ReportedWhat remains is a patent on methods of treatment, including combination treatment, expiring in October 2040.
    Amgen Form 10-K for fiscal 2025 - Item 1 patents, biosimilars and competitors. — FY2025 · publ. 13 February 2026 · source ↗
  3. ReportedIts 10-K says that once multiple biosimilar versions of one of its originator products have launched, competition intensifies rapidly, resulting in accelerated net price declines for both the reference and the biosimilar products.
    Amgen Form 10-K for fiscal 2025 - Item 1 patents, biosimilars and competitors. — FY2025 · publ. 13 February 2026 · source ↗
  4. ReportedKRYSTEXXA is small enough that a copy maker may not bother soon: $1,340 million in 2025.
    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 ↗
  5. ReportedBut it is growing, $400 million in the second quarter of 2026, and every quarter of growth makes it a more attractive target.
    Amgen second-quarter 2026 results release, Form 8-K exhibit 99.1 - product sales performance: inflammation, rare disease and established products, and sales by region. — Q2 2026 · publ. 4 August 2026 · source ↗
Sources
Generated September 28, 2026