Moderna ends its therapeutic HSV vaccine program (mRNA-1608)
Published:
Trade press reported on 20 November 2025 that Moderna will not advance mRNA-1608, its therapeutic HSV-2 vaccine candidate, to Phase 3, discontinuing the program as part of a company-wide pipeline cut. We have not yet confirmed this against a Moderna release or filing. Its Phase 1/2 trial had completed in April 2025 with encouraging interim data; the available reporting frames the decision as strategic rather than a reported safety or efficacy failure.
On 20 November 2025, trade publications (BioSpace and Fierce Biotech) reported that Moderna would not advance mRNA-1608 to Phase 3, ending development of its therapeutic HSV-2 vaccine candidate as part of a broader pipeline cut. We have not been able to check this against a Moderna press release or securities filing, so it rests on those news reports.
Two distinctions are worth holding onto. First, the program’s Phase 1/2 trial had completed (in April 2025), and its interim data — presented at IDWeek 2025 — were encouraging: the vaccine was generally well tolerated and produced immune responses, with an exploratory hint of fewer recurrences. Second, the reporting frames the decision as strategic — a portfolio choice — rather than a reported safety or efficacy failure. A discontinued program is not the same as a failed one, and neither is the same as a proven one. See the candidate page for the full sourced record.