Imiquimod

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Cat Number

API0232224

CAS Number

99011-02-6

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CAS Number

99011-02-6

EINECS

618-567-3

Storage

Store at room temperature

Synonyms

Aldara; 1-(2-methylpropyl)-1H-imidazo[4,5-c]quinolin-4-amine; Zyclara; 1-isobutyl-1H-imidazo[4,5-c]quinolin-4-amine; R-837; 4-Amino-1-isobutyl-1H-imidazo(4,5-c)quinoline

Molecular Formula

C14H16N4

Molecular Weight

240.3

Smiles

CC(C)CN1C=NC2=C1C3=CC=CC=C3N=C2N

Appearance

White to off-white crystalline powder

Melting Point

292-294°C

Boiling Point

456.7±48.0°C at 760 mmHg (Predicted)

Relative Density

1.28±0.1 (Predicted)

General Description

Imiquimod is a synthetic imidazoquinoline with an isobutyl group, belonging to the class of immune response modifiers. Its chemical structure is 1-(2-methylpropyl)-1H-imidazo[4,5-c]quinolin-4-amine. The molecule is a small-molecule toll-like receptor 7 (TLR7) agonist.

Mechanism of Action

Imiquimod acts as a selective agonist for toll-like receptor 7 (TLR7), activating the innate immune system. This leads to the secretion of cytokines, including interferon-alpha (IFN-α), interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-α), which stimulate a Th1-type immune response. The drug also induces the production of natural killer (NK) cells and cytotoxic T lymphocytes, leading to the destruction of tumor cells and virus-infected cells.

Application

Imiquimod is indicated for the topical treatment of actinic keratosis, superficial basal cell carcinoma, and external genital warts (condyloma acuminata). It is also used for the treatment of molluscum contagiosum and for the management of cutaneous metastases of malignant melanoma. The drug is effective in reducing the size and number of lesions.

Imiquimod reduced brain cyst numbers in Toxoplasma gondii-infected mice and rendered remaining cysts non-infectious. Post-establishment of chronic toxoplasmosis, Imiquimod delayed or aborted reactivation. Mechanistically, it upregulated TLR7, 11, and 12 during bradyzoite-to-tachyzoite conversion, activating MyD88 and inducing immune control of reactivated foci.

Fig. 1 Imiquimod exhibits a potent effect on chronic toxoplasmosis. (Hamie M, et al., 2021)

References

Hamie M, et al. Imiquimod Targets Toxoplasmosis Through Modulating Host Toll-Like Receptor-MyD88 Signaling. Front Immunol. 2021;12:629917.

Multispectral immunofluorescence analysis of pretreatment biopsies from the PITVIN trial (38 patients with vulvar HSIL treated with imiquimod) revealed that complete responders (quick and slow) had higher intraepithelial CD3+CD8‑ (CD4+) T helper cells, CD4+FoxP3+ regulatory T cells, and CD14+ inflammatory myeloid cells, and lower CD33+ immature cells compared to non‑responders. Complete responders showed a coordinated infiltration of CD4+, CD8+, and CD14+ cells. These immune cell signatures may predict imiquimod response.

Fig. 2 Correlation between the absolute infiltration of T cells and myeloid cells in the epithelium and stroma in complete responders (CR) and non-responders (NR). (Muntinga CLP, et al., 2025)

References

Muntinga CLP, et al. Pre-existing infiltration with T cells and CD14+ myeloid cells is associated with treatment response to imiquimod in primary and recurrent vulvar high-grade squamous intraepithelial lesions. J Immunother Cancer. 2025;13(10):e012666.

Does Imiquimod require protection from light during storage?

Yes, it is photosensitive. Light exposure can cause photodegradation of the imidazoquinoline ring. Store in light-resistant containers, preferably original opaque packaging.

What is the recommended storage temperature for Imiquimod?

Store at controlled room temperature (15-25°C). Avoid excessive heat above 30°C, which can soften the powder and accelerate oxidative degradation.

Is Imiquimod stable in topical cream formulations?

Yes, when formulated with preservatives and protected from light.

How is the impurity imiquimod N-oxide (an oxidative degradation product) monitored?

This degradation product is quantified using a stability-indicating HPLC method, ensuring it remains within pharmacopoeial limits.