Lupin, Zydus Life shares slide up to 7.5% after US Court blocks generic version of Myrbetriq over patent infringement

Shares of Indian pharmaceutical majors Lupin Ltd. and Zydus Lifesciences Ltd. declined sharply on April 16 after a US Federal Court ruled in favour of Astellas Pharma in a key patent litigation case. The ruling blocks the two companies from selling their generic versions of Mirabegron, the bioequivalent of Astellas' overactive bladder drug, Myrbetriq, in the United States — dealing a serious blow to their US market ambitions and triggering investor concerns.

According to the judgment, the Delaware District Court upheld the validity of Astellas Pharma’s Patent 780 and dismissed the invalidity arguments presented by Lupin and Zydus. Astellas had sued both companies for allegedly infringing on its patent by planning to market generic versions of Myrbetriq. The court concluded that neither Lupin nor Zydus had sufficiently demonstrated the patent's invalidity due to lack of enablement, written description, or indefiniteness.

The court order added that infringement and damages will be addressed in a consolidated jury trial in 2026. Both Indian firms have filed a ‘Motion to Clarify’ in an effort to bring additional validity arguments, but those too will be litigated only during the next phase.

Lupin and Zydus Face Setback in US Market Strategy

The ruling is being seen as a material negative for both Lupin and Zydus, especially since they were among the first to launch 25 mg versions of the drug in the US and had plans to roll out the 50 mg dosage soon. Analysts noted that this outcome could potentially lead to financial penalties, recalls of existing stock, and blocked access to a high-value product in the US pharma market.

Lupin had launched its generic version after obtaining USFDA approval, but the approval has now been effectively overridden by the US court’s ruling in favour of Astellas’ patent enforcement. Myrbetriq, a prescription treatment for overactive bladder and neurogenic detrusor overactivity, is one of Astellas’ key products globally.

Stock Price Reaction and Performance Trend

The stock market reacted swiftly to the court’s verdict. Zydus Life dropped as much as 7.5 percent intraday to ₹818.65, while Lupin fell nearly 4 percent to a low of ₹1,930. In terms of recent performance, Zydus has declined 5.5 percent in the past year, with April alone accounting for a 7 percent drop after a marginal 1 percent gain in March. The stock had already shed 9.6 percent in February and 0.15 percent in January.

Lupin, on the other hand, has had a stronger yearly run, gaining 25 percent in the past 12 months. However, the stock has lost 4.5 percent so far in April, reversing part of its 6.5 percent gain from March. It also witnessed declines of 8.5 percent in February and 11.7 percent in January.

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