Eisai Co. Ltd. and Merck & Co. have successfully defended a critical patent for their blockbuster cancer drug Lenvima, securing protection against generic competition until 2036. Judge Christine P. O'Hearn of the US District Court for the District of New Jersey ruled that Eisai presented sufficient evidence that US Patent No. 11,186,547 describes the invention clearly and in adequate detail, defeating Shilpa Medicare Ltd.'s invalidity arguments.
Patent Protection Extends Market Exclusivity
The protected patent covers a purified form of Lenvima's active ingredient, lenvatinib mesylate, and manufacturing methods. This victory effectively blocks Shilpa's generic version from receiving FDA approval until the patent expires in February 2036, providing Eisai and Merck with extended market exclusivity for their multikinase inhibitor.
While the lawsuit also claimed infringement of another patent (No. 10,407,393), the court did not uphold the validity of that patent. However, the successful defense of the primary patent represents what Eisai called "a major step forward in maximising the value of Lenvima for patients based on the intellectual property of the company."
Significant Revenue Impact
Lenvima represents a substantial revenue source for both pharmaceutical giants. MSD reported more than $1 billion in alliance revenues from Lenvima last year, while Eisai recorded JPY 328.5 billion (approximately $2.26 billion) in global sales during its last financial year ended March 31st, with $1.51 billion coming specifically from the US market.
The drug has achieved remarkable reach since its launch a decade ago, having been administered to more than half a million patients worldwide. Lenvima is currently approved by the FDA for use as a monotherapy in thyroid, kidney, and liver cancers.
Strategic Partnership and Clinical Applications
The patent victory protects a drug that emerged from a significant strategic alliance. MSD licensed rights to Lenvima in 2018 through a deal valued at nearly $6 billion, specifically aimed at developing the drug as a combination partner with its blockbuster cancer immunotherapy Keytruda (pembrolizumab).
This partnership has proven highly successful in clinical practice. Lenvima is now used alongside Keytruda as a widely adopted first-line therapy for kidney cancer and serves as a second-line treatment for certain forms of endometrial cancer. The companies continue developing the combination for additional indications, including oesophageal and liver cancers.
Ongoing Generic Challenges
The Shilpa case represents just one front in Eisai's broader defense against generic competition. The company previously reached a settlement with Sun Pharmaceutical, another generic manufacturer that had filed for Lenvima approval. Under that agreement, Sun committed not to launch its generic version before July 1, 2030, unless Eisai's patent protection is overturned in other legal proceedings.
Eisai has also initiated lawsuits against two additional generic manufacturers, Dr Reddy's Laboratories and Torrent Pharma, seeking to prevent the launch of their respective lenvatinib products. While Shilpa retains the right to appeal the recent court decision, the current ruling strengthens Eisai's position in these ongoing patent disputes.
