FDA Approves ENFLONSIA Patent Extension Timeline Quietly
Published Date: 4/3/2026
Notice
Summary
The FDA has set the official review period for ENFLONSIA, a human biological product, so its patent holder can apply for extra patent time. This affects the company behind ENFLONSIA and anyone interested in patent rules. If you think the dates are wrong or want to challenge the company’s review speed, you have until June 2 or September 30, 2026, to speak up—potentially impacting patent length and market exclusivity.
Analyzed Economic Effects
4 provisions identified: 4 benefits, 0 costs, 0 mixed.
FDA Sets ENFLONSIA Review Period
The FDA determined ENFLONSIA’s regulatory review period is 2,956 days in total: 2,713 days in the testing phase and 243 days in the approval phase. This determination establishes the maximum potential length of any patent extension tied to that regulatory review period.
Applicant Seeks 955 Days Extension
Merck Sharp & Dohme LLC submitted an application to the USPTO seeking 955 days of patent term extension for U.S. Patent No. 9,963,500 related to ENFLONSIA. The USPTO will apply statutory limits when calculating any actual extension.
Key Dates That Shape Extension
FDA verified these dates for ENFLONSIA: the investigational exemption became effective May 8, 2017; the biologics license application was submitted October 10, 2024; and the application was approved June 9, 2025. Those specific dates are used to calculate the testing phase (May 8, 2017 to October 10, 2024) and the approval phase (October 10, 2024 to June 9, 2025) of the regulatory review period.
Deadlines To Comment or Petition
Anyone who believes the published dates are incorrect may submit comments asking for a redetermination by June 2, 2026. Any interested person may petition FDA about whether the applicant acted with due diligence during the regulatory review period by September 30, 2026.
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Key Dates
Department and Agencies
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