German healthcare major Aicuris Anti-infective Cures AG has reported positive results from a pivotal Phase 3 trial showing its experimental antiviral pritelivir significantly outperformed standard therapies in immunocompromised patients with difficult-to-treat herpes simplex virus infections.
The PRIOH-1 study met its primary endpoint, delivering statistically significant and clinically meaningful improvements in lesion healing while reducing treatment-related side effects, the company said.
Pritelivir, an oral antiviral that targets the herpes virus helicase-primase complex, achieved a 62.7% lesion-healing rate, compared with 34.0% for investigator’s choice therapy.
The adjusted treatment difference was 28.4%. Patients receiving pritelivir also experienced markedly fewer drug-related treatment-emergent adverse events, including kidney and electrolyte complications, with discontinuations occurring in just 2.0% of patients versus 20% in the control arm.
“These patients represent one of the most fragile populations we treat, and current options are often toxic, ineffective, or both,” said Genovefa Papanicolaou, Clinical Director of Infectious Disease Service at Memorial Sloan Kettering Cancer Center.
“Current therapeutic options for hematopoietic cell transplant patients with refractory or resistant herpes simplex viral infection are limited by poor response rates, significant toxicities, and the burden of daily intravenous infusions in a healthcare setting,” she said.
"Pritelivir addresses a critical unmet medical need for an oral agent offering statistically superior and clinically meaningful lesion healing with fewer side effects. It has the potential to significantly improve both clinical outcomes and quality of life for these vulnerable patients.”
The safety profile also favored pritelivir, with the most common adverse events — headache, diarrhea, nausea, decreased appetite, vomiting and dizziness — occurring at rates of 5% or higher, but with fewer serious or treatment-limiting effects than existing therapies.
Aicuris executives framed the data as a long-awaited breakthrough in a field that has seen little progress for decades.
“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,” said Cynthia Wat, Chief Medical Officer of Aicuris.
“By targeting an essential step in the virus’s replication process, pritelivir offers a novel approach that can overcome current antiviral resistance,” she added.
“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.”
If confirmed in regulatory review, pritelivir could become the first new antiviral option in decades for immunocompromised patients battling refractory or drug-resistant HSV — a population with few viable treatments and high clinical risk.
