Last reviewed 2026-04-20 · How we verify

Foscavir (FOSCARNET)

Foscarnet works by directly inhibiting viral DNA polymerase, preventing the replication of viral DNA.

Foscarnet (Foscavir), marketed by Clinigen Healthcare, is a direct inhibitor of viral DNA polymerase primarily indicated for CMV Retinitis in AIDS patients. Its key strength lies in its unique mechanism of action, which differentiates it from nucleoside analogs like acyclovir and ganciclovir, offering an alternative for patients who develop resistance to these drugs. The primary risk is the impending patent expiry in 2028, which could lead to increased competition from generics and potentially erode market share.

At a glance

Mechanism of action

Mechanism of Action. Foscarnet exerts its antiviral activity by selective inhibition at the pyrophosphate binding site on virus-specific DNA polymerases at concentrations that do not affect cellular DNA polymerases. Foscarnet does not require activation (phosphorylation) by thymidine kinase or other kinases.

Approved indications

• CMV Retinitis in AIDS Patients
• CMV Retinitis Relapse
• Acyclovir-Resistant Mucocutaneous HSV Infections

Boxed warnings

• WARNING RENAL IMPAIRMENT IS THE MAJOR TOXICITY OF FOSCARNET SODIUM INJECTION. FREQUENT MONITORING OF SERUM CREATININE, WITH DOSE ADJUSTMENT FOR CHANGES IN RENAL FUNCTION, AND ADEQUATE HYDRATION WITH ADMINISTRATION OF FOSCARNET SODIUM INJECTION IS IMPERATIVE. (See ADMINISTRATION section; Hydration .) SEIZURES, RELATED TO ALTERATIONS IN PLASMA MINERALS AND ELECTROLYTES, HAVE BEEN ASSOCIATED WITH FOSCARNET SODIUM INJECTION TREATMENT. THEREFORE, PATIENTS MUST BE CAREFULLY MONITORED FOR SUCH CHANGES AND THEIR POTENTIAL SEQUELAE. MINERAL AND ELECTROLYTE SUPPLEMENTATION MAY BE REQUIRED. FOSCARNET SODIUM INJECTION IS INDICATED FOR USE ONLY IN IMMUNOCOMPROMISED PATIENTS WITH CMV RETINITIS AND MUCOCUTANEOUS ACYCLOVIR-RESISTANT HSV INFECTIONS. (See INDICATIONS section).

Common side effects

• Fever
• Abnormal Renal Function
• Nausea
• Vomiting
• Anemia
• Headache
• Diarrhea
• Seizures
• Death
• Marrow Suppression
• Fatigue
• Rigors

Drug interactions

• intravenous pentamidine
• aminoglycosides, amphotericin B, cyclosporine, acyclovir, methotrexate, tacrolimus
• loop diuretics
• ritonavir, saquinavir
• Class IA antiarrhythmic agents (e.g., quinidine, procainamide), Class III antiarrhythmic agents (e.g., dofetilide, amiodarone, sotalol), phenothiazines, tricyclic antidepressants, certain macrolides and fluoroquinolones

Key clinical trials

• Letermovir Prophylaxis in Children With EBV-Positive T/NK-Cell Lymphoproliferative Disease and Refractory/Relapsed EBV-Associated Hemophagocytic Lymphohistiocytosis (NA)
• A Study of Maribavir in Chinese Adults With Cytomegalovirus (CMV) Infections (PHASE3)
• Infection Prophylaxis and Management in Treating Cytomegalovirus (CMV) Infection in Patients With Hematologic Malignancies Previously Treated With Donor Stem Cell Transplant
• Pharmacokinetics of Drugs Administered to Children
• Trial on Efficacy and Safety of Pritelivir Tablets for Treatment of Acyclovir-resistant Mucocutaneous HSV (Herpes Simplex Virus) Infections in Immunocompromised Subjects (PHASE3)
• A Study of LIVTENCITY (Maribavir) in Adults With Cytomegalovirus (CMV) Infection After Transplantation in South Korea
• Efficacy and Safety of Cytotect®CP, Hyperimmune Anti-CMV IVIg as CMV Prophylaxis in Patients Developing Acute Grade II-IV GVHD After Allogeneic Hematopoietic Cell Transplantation. (PHASE2)
• CMV-CTL for the Treatment of CMV Infection After HSCT (PHASE4)

Primary sources

Every claim on this page is sourced from regulatory or scientific primary sources. See our editorial policy for full methodology.

Competitive intelligence

For the full competitive landscape — auto-detected comparators, recent regulatory actions across the set, upcoming PDUFA, patent timeline, sponsor landscape:

• Foscavir CI brief — competitive landscape report
• Foscavir updates RSS · CI watch RSS
• Clinigen Hlthcare portfolio CI