Japan IP court rules Amgen's patent claims fall short in clash with Sanofi
By Toko Sekiguchi ( May 20, 2025, 08:51 GMT | Insight) -- Amgen has lost a significant battle in its long‑running patent dispute with Sanofi’s Japanese subsidiary. The Japan Intellectual Property High Court dismissed Amgen’s appeal, ruling that its patents for neutralizing antibodies lack the necessary support and disclosure to reliably reproduce the invention.
Amgen has lost a significant battle in its long‑running patent dispute with Sanofi’s Japanese subsidiary. The Japan Intellectual Property High Court dismissed Amgen’s appeal, ruling that its patents for neutralizing antibodies lack the necessary support and disclosure to reliably reproduce the invention. The decision, delivered on Apr. 16, centers on issues of patent sufficiency and disclosure in the rapidly evolving field of antibody therapeutics targeting a protein crucial for cholesterol regulation. Amgen developed a novel antibody technology intended to treat high cholesterol by targeting PCSK9 — a key protein that interacts with the low-density lipoprotein, or LDL, receptor. The LDL receptor binds and removes so‑called “bad” LDL cholesterol from the bloodstream by regulating its uptake into cells. According to Amgen’s patent, the antibodies in question not only bind to PCSK9 but are also designed to neutralize its interaction with the LDL receptor. Amgen’s two patents, Japan Patent Nos. 5705288 and 5906333, describe a method to create antibodies that can both block and neutralize PCSK9. The company claimed that defendant Sanofi’s drug Praluent infringed on its patents and sued for 1 billion yen. The Tokyo District Court examined the patents, focusing on a key component referred to as an "EGFa mimic antibody," interpreted to mean a specific type of neutralizing antibody capable of recognizing most of the residues on PCSK9. However, the court found that although this antibody was supposed to be part of Amgen’s invention, the patent documents did not explain in sufficient detail how to make it. The district court determined that Amgen’s patents failed to meet the support and enablement requirements, meaning that someone skilled in the art would not be able — based solely on the patent’s description and the common knowledge at the time — to reliably produce the required antibody. Because the patent is defective and should be declared invalid, the court ruled that Amgen cannot enforce its patent rights against Sanofi and dismissed its case. During the ensuing proceedings, multiple rounds of invalidation and cancellation lawsuits were initiated, and although Amgen attempted to correct the deficiencies with additional amendments, its efforts did not overcome the lack of adequate disclosure....
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