Tysabri (natalizumab)

Frequently asked

Common questions about Tysabri's patent landscape

When will biosimilars enter the market for Tysabri?

Tysabri's foundational composition patent already expired (Jun 20, 2023), so the cliff window is open. The cliff closes May 31, 2036 when the last US lifecycle patent falls. Whether biosimilars have actually entered depends on the strength of secondary patents (formulations, methods of use, manufacturing) and whether settlements were reached — the Humira precedent saw biosimilars enter ~7 years past composition expiry under licensing agreements with AbbVie.

What's the difference between "cliff opens" and "cliff closes"?

Cliff opens (Jun 20, 2023) marks Tysabri's foundational composition patent expiry — the earliest theoretical date for biosimilar entry. Cliff closes (May 31, 2036) is when the last US patent in the thicket finally falls — after which the market has no patent-based barriers. The gap between these two dates is the lifecycle-extension window: secondary patents (formulations, methods of use, manufacturing) that can block biosimilars even after the composition patent has expired.

Why is Tysabri in the Purple Book?

Tysabri is regulated via the FDA biologic license application (BLA) pathway and listed in the FDA Purple Book (biologics). Biologics are not required to list patents with the FDA — the Purple Book does not include patent listings. The patents shown here are curated by TheraRadar via Google Patents BigQuery search of the sponsor (Biogen Inc.) and mechanism keywords, not pulled from an FDA list.

What's a patent family and why does it matter?

A patent family is a group of patent applications and grants worldwide that share the same priority filing (the earliest invention disclosure). One US patent often expands to 20–40+ filings across different jurisdictions — each grant in a different country protecting the same underlying invention. Tysabri has 19 families that resolve to 342 international documents across 36 countries. Families matter because biosimilar entry requires clearing patent barriers in each market separately — a US biosimilar launch is independent of EU or Japan launches.

How were these Tysabri patents identified?

Tysabri is a biologic, and the FDA's Purple Book does not include patent listings. TheraRadar identified these 32 patents via Google Patents BigQuery search using the sponsor (Biogen Inc.) plus mechanism-specific keywords. This is a curated thicket, not an authoritative FDA list. We then expand each patent to its full international family using the BigQuery patent family graph. Coverage is best-effort and may not capture every patent the sponsor holds.

What does the "Multiplier" stat mean?

The multiplier shows how many international patent documents exist for every US patent in Tysabri's thicket — calculated as 342 international documents ÷ 32 US patents = 11×. A high multiplier (>10×) indicates an aggressive global filing strategy — the sponsor has filed in many countries to maximize geographic protection. A low multiplier suggests the patent estate is US-centric, with limited international protection.