Quick Facts
| CAS Number | 59277-89-3 |
|---|---|
| Molecular Formula | C8H11N5O3 |
| Molecular Weight | 225.20 |
| Pharmacopoeia | USP, EP, CP |
| Packaging | 25 KG/DRUM |
Product Overview
Acyclovir was discovered in 1974 by a research team led by Gertrude B. Elion and Howard Schaeffer at Burroughs Wellcome (now part of GSK). The discovery was the culmination of a rational drug design program that began with the observation that herpes simplex virus (HSV) encodes its own thymidine kinase (TK) — an enzyme that could be exploited as a selective drug target. Schaeffer synthesized acyclovir as part of a series of acyclic nucleoside analogues, and Elion's team demonstrated that the compound is phosphorylated by viral TK 3,000-fold more efficiently than by host enzymes, producing the first truly selective antiviral drug. Elion, along with George Hitchings, received the 1988 Nobel Prize in Physiology or Medicine for this and related discoveries.
Acyclovir works through a three-step activation cascade: viral TK performs the first phosphorylation to acyclovir monophosphate, then host guanylate kinase and other cellular kinases produce the active triphosphate form. The triphosphate competitively inhibits viral DNA polymerase and, because it lacks a 3'-hydroxyl group, acts as a chain terminator when incorporated into viral DNA. This mechanism is dependent on viral TK activity, meaning acyclovir is inactive against latent virus in neurons and against TK-deficient viral strains — a limitation that informs clinical treatment strategies.
Acyclovir's impact extends far beyond HSV. It is effective against varicella-zoster virus (chickenpox and shingles) and has activity against Epstein-Barr virus, though less potently. The compound's major clinical limitation — poor oral bioavailability of only 15-20% — led to the development of valacyclovir, the L-valine ester prodrug launched by GSK in 1995. Despite this, generic acyclovir remains the most widely prescribed antiviral API globally, available in oral tablets, topical creams (5%), ophthalmic ointments (3%), and intravenous formulations.
As of mid-2026, the global acyclovir API market continues to grow, driven by high HSV-1 seroprevalence (estimated at 67% of the global population under 50 per WHO), expanding access to antiviral therapy in emerging markets, and increasing off-label use for conditions linked to viral reactivation. China accounts for a substantial share of global acyclovir API production, with manufacturing concentrated in Zhejiang and Jiangsu provinces. KingWish supplies GMP-certified acyclovir meeting USP, EP, and CP standards.
Quality Specifications
| Assay (HPLC, anhydrous) | 98.0% - 101.0% (USP/EP) |
|---|---|
| Guanine (major impurity) | ≤ 0.7% |
| Total Impurities | ≤ 1.0% (individual unspecified ≤ 0.1%) |
| Water Content (KF) | ≤ 0.5% |
| Heavy Metals | ≤ 10 ppm |
| Residual Solvents | Compliant with ICH Q3C; DMF ≤ 880 ppm |
| GMP Status | Manufactured under ICH Q7 GMP conditions |
Applications
- Herpes simplex treatment: Gold standard antiviral API for HSV-1 (cold sores) and HSV-2 (genital herpes). Oral, topical, and IV formulations.
- Varicella-zoster therapy: First-line treatment for chickenpox and shingles (herpes zoster), reducing lesion duration and acute pain severity.
- Topical antiviral creams: 5% acyclovir cream for recurrent herpes labialis. Effective against primary and recurrent mucocutaneous HSV infections.
- Ophthalmic preparations: 3% acyclovir ophthalmic ointment for herpes simplex keratitis and ocular HSV infections.
Sourcing Acyclovir: Key Checks
Documentation
Request CoA with HPLC impurity profile — guanine is the critical marker. Verify residual solvent data, particularly DMF content, against ICH Q3C limits. For US/EU markets, confirm DMF or CEP filing status.
Red Flags
Elevated guanine above 0.7% indicates incomplete synthesis or degradation. Polypeptide-related impurities from incomplete deprotection. Suppliers unable to provide batch-specific HPLC chromatograms before order placement.
Packaging & Logistics
Standard: 25 KG/DRUM with double PE liner. Store at room temperature (15-25 degrees Celsius), protected from light and moisture. Standard lead time 4-8 weeks depending on documentation requirements.
Market Context
Global acyclovir API market growing steadily, driven by ~3.7 billion people (67% of global population) carrying HSV-1 and expanding antiviral access in emerging markets. China is the dominant API producer. Patent expiry of valacyclovir drives continued demand for the parent compound.