Pritelivir Shows Superior Efficacy Over Foscarnet in Phase II Trial for Resistant HSV Infections
核心洞察
Aicuris (搜索)'s pritelivir demonstrated 93.3% healing rates versus 57.1% for foscarnet in immunocompromised patients with acyclovir-resistant HSV infections.
The oral antiviral showed significantly better safety profile with only 8.7% drug-related adverse events compared to 71.4% for foscarnet.
Phase III trial results indicate pritelivir met primary endpoints with statistical superiority over standard-of-care therapies, with FDA submission planned for 2026.
Dr. Camille Kotton from Massachusetts General Hospital presented compelling Phase II data at IDWeek 2025 demonstrating that Aicuris (搜索)'s pritelivir significantly outperformed foscarnet in treating acyclovir-refractory herpes simplex virus (搜索) (HSV) infections in immunocompromised patients. The PRIOH-1 trial results, presented at the joint annual meeting held October 19-21 in Atlanta, Georgia, showed pritelivir achieved a 36.2% treatment difference over the current standard of care.
Phase II Trial Results Show Clear Efficacy Advantage
The randomized PRIOH-1 Phase II trial enrolled immunocompromised adults, including HIV patients, hematopoietic cell transplant recipients, solid organ transplant recipients, and those with chronic glucocorticoid use. In Part A of the study, 14 out of 15 patients (93.3%; 95% CI, 68.1–99.8) achieved healed lesions with pritelivir treatment compared to four out of seven patients (57.1%; 95% CI, 18.4–90.1) receiving foscarnet, representing a treatment difference of 36.2% (95% CI, 10.1–74.1).
Part B evaluated pritelivir in a more heavily treatment-refractory population through a non-randomized single arm design. Among patients who were acyclovir or foscarnet-refractory/resistant or foscarnet-intolerant, five out of eight pritelivir-treated patients (62.5%; 95% CI, 24.5–91.5) achieved healed lesions.
Superior Safety Profile Addresses Key Limitation
The safety data revealed a stark contrast between treatments. Only two out of 23 pritelivir-treated patients (8.7%) experienced drug-related treatment emergent adverse events, compared to five out of seven foscarnet-treated patients (71.4%). This represents a significant improvement over foscarnet, which has been the mainstay treatment since the 1990s but is considerably nephrotoxic and requires intravenous administration.
Foscarnet currently achieves clinical improvement in only about half of patients with refractory and resistant HSV infections. The resulting painful lesions can severely impact quality of life and lead to potentially fatal complications including encephalitis (搜索), pneumonitis (搜索), and hepatitis (搜索).
Novel Mechanism Addresses Growing Clinical Need
Pritelivir is a small molecule with a novel mechanism of action that has demonstrated activity against nucleoside analogue and foscarnet-resistant HSV-1 (搜索) and HSV-2 (搜索) isolates in vitro. The drug offers significant practical advantages with oral bioavailability, a 60-day half-life enabling once-daily dosing, and no clinically relevant drug-drug interactions.
The US Food and Drug Administration (搜索) has granted pritelivir breakthrough therapy designation, recognizing its potential to address critical unmet medical needs. The management of HSV infections among immunocompromised patients has become increasingly challenging as this population has grown substantially due to improved cancer treatments and other medical advances.
Regulatory Timeline and Market Outlook
A Phase III pivotal trial in refractory HSV-infected immunocompromised patients is currently underway, with initial results indicating that pritelivir met the primary endpoint, achieving highly statistically significant superiority over standard-of-care therapies. Topline data are anticipated in early 2026.
Aicuris (搜索) has announced preparations to submit a new drug application to the FDA in 2026. The company anticipates an expanding target patient population as the percentage of the global immunocompromised population continues to increase.
The drug is positioned to provide HSV-infected immunocompromised patients with safer, more convenient, and more effective symptom management, potentially resulting in substantial quality-of-life improvements for this vulnerable population.