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# Regulatory Review Period for Merck’s Prevymis
- URL: https://www.fdaweb.com/regulatory-review-period-for-mercks-prevymis-2/
- Published: 2022-11-14T12:00:00.000Z
- Updated: 2026-09-14T18:06:18.000Z
- Author: David McFarland
- Tags: FDA Policy/General, #legacy-id-D5153191

*Federal Register* notice: FDA has determined for patent term extension purposes the regulatory review period for Merck’s Prevymis (letermovir) intravenous solution, indicated for prophylaxis of cytomegalovirus (CMV) infections and disease in adult CMV-seropositive recipients of an allogeneic hematopoietic stem cell transplant. The regulatory review period is 3,157 days, of which 2,911 days occurred during the testing phase and 246 days during the approval phase. To view the notice, click [here](https://www.govinfo.gov/content/pkg/FR-2022-11-14/pdf/2022-24719.pdf?ref=fdaweb.com).