GSK3943104

GSK3943104 was an adjuvanted recombinant-protein therapeutic vaccine candidate intended to prevent or delay recurrent genital herpes in adults with HSV-2.

In its randomized Phase 1/2 study, GSK reported that recurrence timing was similar with the two selected vaccine formulations and placebo. The primary Phase 2 efficacy objective was not met, and GSK did not advance the candidate to Phase 3.

The candidate used HSV-2 glycoprotein E and glycoprotein I antigens. Early study groups tested several antigen doses without an adjuvant or with GSK's AS01B or AS01E adjuvant systems. The two formulations selected for Part 2 were labeled HSVTI_F1 and HSVTI_F2; they were formulations within GSK3943104A, not separate programs.

The therapeutic goal was to reduce recurrent HSV-2 genital-herpes episodes. The main efficacy measure asked how long it took until a participant had a PCR-confirmed HSV-2 recurrence after the two-dose series.

TH HSV REC-003, registered as NCT05298254, first compared nine formulations in healthy HSV-2-seronegative adults and then compared two selected adjuvanted formulations with placebo in adults with recurrent HSV-2 genital herpes.

GSK announced the negative primary analysis in September 2024. The study continued follow-up and completed on June 12, 2025. GSK later made a plain-language result summary available. A separate 50-person Japanese Phase 1 formulation study also completed and posted results, but it was not a therapeutic efficacy test.

GSK's result summary says the timing of the first recurrence was similar across the two HSVTI groups and placebo. It concludes that neither selected candidate reduced recurrence risk. The checked public summary does not provide the treatment-effect estimate or confidence interval, so the size and precision of the result cannot be independently described here.

GSK initially said no safety concern was observed. The later summary reported one serious treatment-related episode resembling near-fainting in Part 1, no serious treatment-related side effects in Part 2, and no deaths caused by side effects. These are sponsor reports, not evidence that the candidate was proven broadly safe.

This program generated controlled human efficacy evidence, but that evidence was negative for the tested recurrence objective. Evidence maturity describes the study design and question answered; it does not mean the candidate worked.

The result does not establish that therapeutic vaccination can never work, and it does not explain whether antigen choice, formulation, immune response, or another factor caused the outcome. It establishes a narrower fact: these selected formulations did not meet this Phase 2 objective.

The Phase 1/2 study is completed, but the program is discontinued: GSK removed GSK3943104 from its Phase 2 pipeline and decided not to advance it to Phase 3. Its later result summary said no future studies were planned for this candidate.

A future evidence update would be warranted if GSK posts the full efficacy analysis, publishes a peer-reviewed report, explicitly maps GSK4108771A to this lineage, or names a successor HSV program. None was confirmed by September 1, 2026.