Pritelivir
Pritelivir is an investigational oral HSV antiviral that has completed Phase 3. Its developer reports that the FDA is reviewing an application for people with weakened immune systems whose HSV sores have not responded to available treatment.
- Developer / organization
- AiCuris Anti-infective Cures AG · Asahi Kasei Corporation · Veloxis Pharmaceuticals
- Intervention type
- Small-molecule antiviral
Current status
Evidence, regulatory review, and access are separate questions.
- Phase 3 study
- Completed
- Primary result
- PositiveComplete lesion healing by day 28
- Regulatory status
- Priority ReviewFDA review reported by AiCuris
- Availability
- Not FDA-approvedNot generally available
- Sources checked
- HSVHQ reviewed sources through this date.
What this means right now
The Phase 3 trial's primary result was positive: more participants receiving pritelivir had complete lesion healing by day 28 than participants receiving a treatment selected by the study investigator.
This is meaningful late-stage evidence for an uncommon, difficult-to-treat clinical setting. It does not establish routine treatment for otherwise healthy people with recurrent genital herpes. As of September 1, 2026, pritelivir was not FDA-approved or generally available.
A restricted expanded-access program was listed for narrowly eligible immunocompromised patients. Expanded access allows a doctor to request an investigational drug outside a trial under specific conditions; it is not ordinary prescription availability.
What is pritelivir?
Pritelivir, also known by the development identifier AIC316, blocks the HSV helicase-primase complex: viral machinery HSV needs to make copies of itself. It acts at a different step from nucleoside-analogue antivirals such as acyclovir.
The current program focuses on refractory mucocutaneous HSV-1 or HSV-2 in immunocompromised people. In plain language, that means HSV sores on the skin or moist body surfaces in people with weakened immune systems, where the infection has not responded to treatment. Earlier trials studied recurrent genital HSV-2 in otherwise healthy adults, but those studies do not broaden the use covered by the submitted application.
What Phase 3 tested
PRIOH-1 asked whether oral pritelivir could produce complete lesion healing more often than investigator-selected therapy. The comparison treatment was chosen for each participant from foscarnet, cidofovir, or imiquimod. This reflected the difficult clinical setting, but it also meant that pritelivir was not compared with one uniform control treatment.
What did Phase 3 find?
PRIOH-1 was an open-label Phase 3 study, meaning participants and investigators knew which treatment was given. The full study enrolled 158 people across randomized and nonrandomized parts. The pivotal randomized Part C included 101 participants: 51 received pritelivir and 50 received investigator-selected therapy.
The study began in 2017 and was completed in November 2025. The primary comparison measured complete healing of all lesions by day 28.
Complete lesion healing by day 28
Statistical detail: Adjusted difference 28.4 percentage points (95% CI 9.6–47.3; p=0.0047).
This was the trial's primary endpoint. It measured lesion healing in a narrowly defined population, not transmission or cure.
Other reported findings
AiCuris later reported complete healing by day 42 in 82.4% of participants who continued pritelivir and 42.0% of those who continued investigator-selected therapy. This was a sponsor-reported secondary result, and the public release did not provide the full analysis population or all missing-data details.
Drug-related adverse events were reported in 11 of 51 pritelivir recipients and 27 of 50 comparison recipients. Events attributed to treatment led to discontinuation in 1 of 51 and 10 of 50, respectively. These are comparative trial observations, not proof that pritelivir is generally safer: the study was open label, the comparison treatments differed, and the public safety report remains abbreviated.
What this result tells us
Within the specific Phase 3 population, more participants assigned to pritelivir had complete lesion healing by day 28 than participants assigned to investigator-selected therapy. That is large confirmatory human evidence for the measured outcome in this setting.
The result matters because it comes from a randomized late-stage comparison in people with few treatment options. Its meaning remains narrow: lesion healing over 28 days in immunocompromised people with refractory infection.
What it doesn't tell us
Approval and availability
AiCuris reported that the FDA accepted its US application for Priority Review. Priority Review uses a shorter FDA review goal; it is not approval and does not predict what the FDA will decide.
As of September 1, 2026, no approval action or final US label had been identified, and pritelivir was not generally available. A restricted expanded-access protocol was listed for narrowly eligible immunocompromised patients with treatment-resistant HSV who could not enter the trial and lacked an approved treatment option.
AiCuris remains the named sponsor. Asahi Kasei acquired AiCuris in April 2026 and said it planned to develop the business through its Veloxis subsidiary; the checked record did not establish a sponsor transfer.
What happens next?
The next reported milestone was the FDA's target action period in the fourth quarter of 2026, after the sources for this page were last checked on September 1. It is a review target, not an approval or launch forecast.
The record should be updated when the FDA acts or when fuller Phase 3 results become public. Until then, the approval decision, final label, broader availability, and complete benefit-risk assessment remain unresolved in the checked public evidence.
Detailed evidence
Study design, earlier trials, development history, source provenance, and review metadata follow below.
Program record
- Organizations
- AiCuris Anti-infective Cures AG (Developer (current), Originator (current), Sponsor (current))Asahi Kasei Corporation (Owner (current))Veloxis Pharmaceuticals (Developer (planned))
- Goal
- Treat HSV
- Approach
- Oral helicase-primase inhibitor for refractory mucocutaneous HSV infection in immunocompromised people
- Intended HSV scope
- HSV-1 + HSV-2
- Human evidence scope
- HSV-1 + HSV-2
- Studied indication / setting
- Refractory HSV
- Current stage
- Regulatory review
Large confirmatory evidence
This describes the strongest research evidence in the sources HSVHQ reviewed. Development stage, regulatory review, and availability are shown separately.
Timeline
Priority Review reported
AiCuris reported that FDA accepted the pritelivir NDA for Priority Review.
Why it matters: Moves the program into regulatory review but is not approval.
PRIOH-1 completed
The Phase 3 study reached actual completion.
Why it matters: Closes pivotal study follow-up before regulatory submission.
Technical record
Study details
Participants in randomized Part C received a 400 mg pritelivir loading dose followed by 100 mg once daily, or an investigator-selected treatment of intravenous foscarnet, intravenous or topical cidofovir, or topical imiquimod. Treatment lasted up to 28 days and could continue to 42 days if lesions were improving.
AiCuris also reported a median time to undetectable HSV of 9 days with pritelivir and 21 days with investigator-selected therapy, with p=0.0581. HSVHQ does not describe that comparison as statistically significant. The result remains sponsor-reported without a full public analysis.
Earlier randomized studies in otherwise healthy people with recurrent genital HSV-2 reported reduced viral shedding with pritelivir versus placebo and, over a 28-day period, versus valacyclovir. Viral shedding means HSV was detected in genital samples; it is not the same as measuring transmission to a partner.
The valacyclovir comparison ended early after an FDA clinical hold prompted by findings in a chronic monkey toxicity study. Later clinical development resumed and reached the completed Phase 3 program, but the checked public record did not contain a full regulatory account of how the earlier issue was resolved.
NCT03073967
Completed- Registry
- ClinicalTrials.gov
- Phase
- Phase 3
- Enrollment
- 158
- Results
- Not posted
Started May 8, 2017 · Completed November 11, 2025
Evidence and sources
Trial registries document study plans and status. Journal articles and conference abstracts report scientific findings. Company reports are listed separately because they come from organizations with a stake in the program.
- Effect of Pritelivir Compared With Valacyclovir on Genital HSV-2 Shedding
Anna Wald; Burkhard Timmler; colleagues · JAMA
DOI 10.1001/jama.2016.18189 · NCT01658826
- Helicase–Primase Inhibitor Pritelivir for HSV-2 Infection
Anna Wald; Lawrence Corey; colleagues · New England Journal of Medicine
DOI 10.1056/NEJMoa1301150 · NCT01047540
- PRIOH-1 Phase 3 study record
ClinicalTrials.gov · AiCuris
NCT03073967
- Pritelivir expanded-access intermediate-size treatment protocol
ClinicalTrials.gov · AiCuris
NCT05844436
- Pritelivir Demonstrated Superior Efficacy Compared to Investigator’s Choice Treatment for Refractory Herpes Simplex Virus Infections
Genovefa Papanicolaou; Roy Chemaly; colleagues · Transplantation and Cellular Therapy
DOI 10.1016/j.jtct.2026.02.038 · NCT03073967
- AiCuris Receives FDA Priority Review for Pritelivir NDA and Presents New Phase 3 Data at ESCMID 2026
AiCuris · AiCuris
NCT03073967
- Asahi Kasei completes acquisition of AiCuris
Asahi Kasei · Asahi Kasei