Adibelivir

Adibelivir, formerly called IM-250, is an investigational small-molecule HSV antiviral whose oral program entered the Phase 2a part of a study in adults with recurrent genital HSV-2 in June 2026.

Early human studies have been completed, but no public human efficacy result or complete Phase 1 results report was identified in the checked sources through September 4, 2026.

Animal and laboratory studies reported activity against HSV-1 and HSV-2, including effects on measured reactivation outcomes in animals, but they do not show that adibelivir cures HSV, eliminates latent infection in people, or prevents transmission.

Adibelivir blocks the HSV helicase-primase complex, part of the machinery the virus uses to copy its DNA.

The checked cell and animal studies included HSV-1 and HSV-2, while the patient study identified for this packet is limited to adults with recurrent genital HSV-2.

The program now has two distinct development paths: Innovative Molecules retained the oral and other non-licensed formulations, while Alfasigma licensed only the parenteral formulation for HSV encephalitis.

The oral IM-202 study is testing whether adibelivir can reduce the rate of genital HSV shedding, meaning how often HSV is detected in genital samples, in adults with recurrent genital HSV-2.

The study also plans to measure lesions, the amount of detected virus, shedding without symptoms, pharmacokinetics, and safety, but these planned outcomes are not results.

For the parenteral formulation, the companies described a separate goal of developing adibelivir for HSV encephalitis.

The first-in-human IM-101 study gave single oral doses to healthy adults, began in April 2023, completed in May 2024, and reported 18 participants.

Two later healthy-volunteer studies, IM-102 and IM-103, ended in 2025 and examined multiple dosing and the effect of food on a single dose.

In January 2026, Innovative Molecules said those three studies and the Phase 1b part of IM-202 were complete and that the combined clinical profile supported advancing the oral program.

The company reported the first participant dosed in the Phase 2a part of IM-202 on June 25, 2026, and the official European registry still listed the integrated Phase 1b/2a study as recruiting on September 4, 2026.

The only peer-reviewed human measurements identified were pharmacokinetic data from two IM-101 participants in a paper focused on validating an analytical assay.

The checked abstract for that narrow report does not provide the whole trial's participant flow, safety results, dose-response analysis, or complete pharmacokinetic findings.

In guinea-pig genital HSV-2 and mouse ocular HSV-1 models, researchers reported reductions in measured recurrence, shedding, or reactivation competence after IM-250 treatment, while latent viral genomes remained detectable.

A separate cross-species animal study reported nervous-tissue exposure nearer plasma levels than for several compared helicase-primase inhibitors under the tested conditions.

A 2026 cell-culture study reported activity against more than 50 HSV-1 and HSV-2 clinical isolates and laboratory strains, including nucleoside-resistant strains, as well as synergy with several antivirals in vitro.

The most defensible evidence-maturity label is early human evidence: adibelivir has reached human safety and pharmacokinetic studies, and a controlled patient study is under way, but no public human efficacy result has been identified.

The animal nervous-system and reactivation findings provide preclinical context for the program, but they do not establish a human effect on latent HSV or HSV encephalitis.

The in-vitro resistance and combination findings also do not establish that adibelivir will benefit patients with drug-resistant HSV or that combining it with another antiviral is clinically useful.

As of September 4, 2026, no marketing approval or expanded-access record was identified in the checked routes, so adibelivir remained an investigational program rather than an available HSV treatment.

The active clinical stage is the oral Phase 2a path for recurrent genital HSV-2, with IM-202 recruiting on September 4, 2026.

Alfasigma and Innovative Molecules reported that the separately licensed parenteral formulation had authorization to enter Phase 1 for HSV encephalitis, but the checked record did not establish that a parenteral human trial had begun.

The next result that could change the oral program's evidence maturity is a completed, publicly reported IM-202 analysis, especially its controlled genital-shedding result and accompanying safety data.

For the parenteral path, the next concrete milestone would be an identified registered and initiated Phase 1 trial rather than another statement of authorization or intent.