Aicuris has reported positive findings from its pivotal Phase III trial (PRIOH-I) assessing pritelivir in immunocompromised patients with refractory herpes simplex virus (HSV) infections, both with and without resistance.
The open-label, comparative, controlled global trial assessed pritelivir, a small molecule antiviral targeting the helicase-primase complex of HSV, versus investigator’s choice therapy (ICT).
It enrolled and treated 101 immunocompromised patients with refractory or resistant HSV infection, comprising transplant recipients (both haematopoietic stem-cell and solid organ), individuals with malignancies, autoimmune or inflammatory conditions, and those with HIV infection.
A further 56 patients participated in the non-randomised segment of the study.
Participants were treated with either oral pritelivir (100mg per day following a 400mg loading dose on the initial day) or ICT, which included IV foscarnet, IV or topical cidofovir, or topical imiquimod. Treatment lasted up to 28 days, extendable to 48 days if lesion improvement occurred.
In October 2025, Aicuris confirmed that the study achieved its primary efficacy endpoint and showed a favourable tolerability and safety profile.
Treatment-emergent adverse events (TEAEs) related to drug use were lower with pritelivir than with ICT, reported in 2.0% of pritelivir recipients versus 20% in the ICT group. Common TEAEs included diarrhoea, headache, decreased appetite, nausea, dizziness and vomiting.
Aicuris chief medical officer Cynthia Wat said: “For more than two decades, there has been no innovation in antiviral medicines for HSV, leaving clinicians with limited treatment options for patients who do not respond to existing antivirals. By targeting an essential step in the virus’s replication process, pritelivir offers a novel approach that can overcome current antiviral resistance.
“Together, these results mark a pivotal moment for patients with refractory HSV infections, supporting pritelivir’s potential to redefine the standard of care for patients at high risk of morbidity and mortality. We look forward to bringing it swiftly to those with few effective and well-tolerated alternatives.”
In 2024, Aicuris launched a first-in-human Phase I trial of AIC468, an antisense oligonucleotide designed to combat BK virus (BKV) infections in kidney transplant (KT) recipients.
