Determination of Regulatory Review Period for Purposes of Patent Extension; ENFLONSIA
AI-generated summary for informational purposes only. Not legal advice. See the original source for the authoritative text.
The FDA has calculated the regulatory review period for the biologic product ENFLONSIA (clesrovimab-cfor), developed by Merck Sharp & Dohme LLC. This monoclonal antibody is approved for the prevention of RSV lower respiratory tract disease in neonates and infants entering their first RSV season. The total regulatory review period is 2,956 days, consisting of a 2,713-day testing phase that began on May 8, 2017, and a 243-day approval phase that ran from October 10, 2024, to June 9, 2025. This determination sets the maximum possible patent term extension for U.S. Patent No. 9,963,500. The applicant is seeking 955 days of extension. Comments challenging the dates must be submitted by June 2, 2026, and due-diligence petitions by September 30, 2026.
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Key Changes
- Total regulatory review period determined as 2,956 days
- Testing phase: 2,713 days starting May 8, 2017 (IND effective date)
- Approval phase: 243 days from October 10, 2024 (BLA submission) to June 9, 2025 (approval date)
+ 3 more changes with Pro
Obligations
What this law requires
Submit comments challenging the accuracy of published dates regarding the regulatory review period for ENFLONSIA to FDA by June 2, 2026, via regulations.gov or written submission to Dockets Management Staff
Include Docket No. FDA-2025-E-3626 in all submissions regarding the ENFLONSIA regulatory review period determination
Submit electronic comments through regulations.gov by 11:59 p.m. Eastern Time on June 2, 2026, or submit written/paper comments to Dockets Management Staff by the same date for timely consideration
Ensure comments submitted to regulations.gov do not contain confidential information such as medical information, Social Security numbers, or confidential business information, as such comments will be made publicly available
Submit confidential information only as written/paper submissions in two copies, with one copy clearly marked 'THIS DOCUMENT CONTAINS CONFIDENTIAL INFORMATION' to Dockets Management Staff