Is pritelivir available in the USA?: Understanding Its Investigational Status

October 11, 2025 •

3 min read

While herpes simplex virus (HSV) affects a significant portion of the global population, some immunocompromised patients face severe, treatment-resistant infections. This unmet medical need has fueled the development of novel antivirals, leading many to ask: Is pritelivir available in the USA?

Quick Summary

Pritelivir is not yet commercially available in the USA but can be accessed by eligible immunocompromised patients with treatment-resistant herpes via an Expanded Access Program. The drug is currently in pivotal Phase 3 clinical trials, targeting a potential market authorization filing in 2026.

Key Points

Not Commercially Available: Pritelivir is an investigational drug and is not commercially approved or sold in the USA.
Expanded Access Program: Eligible immunocompromised patients with treatment-resistant HSV can access pritelivir via an Expanded Access Program (EAP).
FDA Designations: The U.S. FDA has granted pritelivir both Fast Track (2017) and Breakthrough Therapy (2020) designations to speed up its review.
Novel Mechanism: Unlike standard antivirals, pritelivir works by inhibiting the viral helicase-primase complex, offering a new way to combat HSV.
Advanced Clinical Stage: A pivotal Phase 3 trial for immunocompromised patients with treatment-resistant HSV has completed enrollment, with results expected to support a future regulatory filing.
Addresses Unmet Need: Pritelivir is being developed specifically for immunocompromised patients whose infections have become resistant to or intolerant of existing treatments like acyclovir and foscarnet.

Pritelivir is an antiviral drug under investigation for the treatment of herpes simplex virus (HSV) infections. It is particularly relevant for immunocompromised individuals who experience infections resistant to current treatments. While it shows promise, pritelivir is not currently available for commercial use in the United States.

Pritelivir's Current Availability in the USA

Pritelivir is an investigational drug and has not received marketing approval from the U.S. Food and Drug Administration (FDA). Therefore, it is not available for prescription or purchase in the USA.

Access Through Expanded Access Programs

Certain immunocompromised patients with treatment-resistant HSV may be able to access pritelivir through an Expanded Access Program (EAP). This program allows access to investigational drugs for patients with serious conditions who have exhausted other treatment options and cannot participate in clinical trials. The EAP for pritelivir is designed to help eligible patients with treatment-resistant HSV-1 or HSV-2 who are immunocompromised. Information on accessing the EAP is available, sometimes through collaborations with partners like myTomorrows.

Pritelivir's Unique Pharmacology and FDA Journey

Pritelivir is a helicase-primase inhibitor, representing a new class of antiviral drugs. This differs from existing nucleoside analog (NA) antivirals, which target viral DNA polymerase.

Mechanism of Action: Targeting Helicase-Primase

Pritelivir's mechanism involves directly inhibiting the viral helicase-primase complex, essential for viral DNA replication. This unique action means it can be effective against HSV strains that are resistant to nucleoside analogs. It is active against both HSV-1 and HSV-2.

FDA Designations and Clinical Trials

The FDA has recognized pritelivir's potential by granting it Fast Track Designation in 2017 and Breakthrough Therapy Designation in 2020. These designations aim to expedite the development and review of drugs addressing unmet medical needs. Pritelivir is currently in pivotal Phase 3 clinical trials. The enrollment for a key Phase 3 trial (PRIOH-1) in immunocompromised patients with acyclovir-resistant mucocutaneous HSV was completed in July 2025. The results of this trial are expected to support a marketing authorization filing, potentially in 2026.

Comparison with Standard Antiviral Therapies

Pritelivir offers potential advantages compared to currently available treatments for herpes:


Feature	Pritelivir	Acyclovir/Valacyclovir	Foscarnet
Mechanism of Action	Inhibits viral helicase-primase	Inhibits viral DNA polymerase	Inhibits viral DNA polymerase
Targeted Patient Population	Primarily immunocompromised with treatment-resistant HSV	Immunocompetent and immunocompromised patients	Immunocompromised patients with acyclovir-resistant strains
Route of Administration	Oral tablet	Oral tablet	Intravenous (IV)
Resistance Profile	Active against nucleoside analog-resistant strains	Can lose effectiveness due to resistance mutations	Can also face resistance; often used for acyclovir-resistant cases
Toxicity Profile	Favorable safety and tolerability shown in trials	Generally well-tolerated, but can have side effects	Significant toxicity, particularly nephrotoxicity

Conclusion

To answer is pritelivir available in the USA?, the answer is currently no, for commercial sale. It is an investigational drug with a novel mechanism of action, particularly promising for immunocompromised patients with treatment-resistant HSV. Pritelivir has received FDA Fast Track and Breakthrough Therapy designations. While not yet approved, eligible patients may access it through an Expanded Access Program. The completion of the pivotal Phase 3 trial is a significant step towards a potential marketing authorization filing in 2026. Access at this time is limited to those with the greatest medical need. Further information can be found on ClinicalTrials.gov.

Frequently Asked Questions

No, pritelivir cannot be obtained with a standard prescription in the USA. It is an investigational drug that has not yet received commercial marketing approval from the FDA.

An Expanded Access Program (EAP) allows for the use of an investigational drug outside of a clinical trial. It is reserved for patients with serious conditions who have exhausted all other treatment options and cannot participate in a clinical trial.

The Expanded Access Program for pritelivir is available to eligible immunocompromised subjects with treatment-resistant HSV type 1 or 2, who do not have access to clinical trial options.

Unlike older medications like acyclovir, which inhibit viral DNA polymerase, pritelivir is a helicase-primase inhibitor. This novel mechanism targets a different enzyme complex, allowing it to be effective against drug-resistant strains.

Pritelivir has been granted Fast Track and Breakthrough Therapy designations by the FDA. It is currently in a pivotal Phase 3 clinical trial, which is a necessary step before a new drug application can be filed for potential approval.

Commercial availability depends on a successful Phase 3 trial and subsequent FDA approval. The manufacturer, AiCuris, completed enrollment for its pivotal trial in July 2025 and aims to file for marketing authorization in 2026, though timelines can vary.

Yes, due to its unique mechanism of action, pritelivir has shown activity against HSV strains that are resistant to standard nucleoside analog drugs like acyclovir.