Bexarotene selectively binds and activates retinoid X receptor subtypes (RXRα, RXRβ, RXRγ). RXRs can form heterodimers with various receptor partners such as retinoic acid receptors (RARs), vitamin D receptor, thyroid receptor, and peroxisome proliferator activator receptors (PPARs). Once activated, these receptors function as transcription factors that regulate the expression of genes that control cellular differentiation and proliferation. Bexarotene inhibits the growth in vitro of some tumor cell lines of hematopoietic and squamous cell origin. It also induces tumor regression in vivo in some animal models. The exact mechanism of action of bexarotene in the treatment of cutaneous T-cell lymphoma (CTCL) is unknown.

Targretin® (bexarotene) gel 1% is indicated for the topical treatment of cutaneous lesions in patients with CTCL (Stage IA and IB) who have refractory or persistent disease after other therapies or who have not tolerated other therapies.

Targretin® gel should be initially applied once every other day for the first week. The application frequency should be increased at weekly intervals to once daily, then twice daily, then three times daily and finally four times daily according to individual lesion tolerance. (See Full Prescribing Information.)

The safety of Targretin® gel has been assessed in clinical studies of 117 patients with CTCL who received Targretin® gel for up to 172 weeks. In the multicenter open label study, 50 patients with CTCL received Targretin® gel for up to 98 weeks. The mean duration of therapy for these 50 patients was 199 days. The most common adverse events reported with an incidence at the application site of at least 10% in patients with CTCL were rash, pruritus, skin disorder, and pain. (See Full Prescribing Information.)

Targretin® gel 1% is contraindicated in patients with a known hypersensitivity to bexarotene or other components of the product. Pregnancy: Category X. (See Full Prescribing Information.)

Pregnancy: Category X. See CONTRAINDICATIONS. General: Targretin® gel should be used with caution in patients with a known hypersensitivity to other retinoids. No clinical instances of cross-reactivity have been noted. Vitamin A Supplementation: In clinical studies, patients were advised to limit vitamin A intake to ≤15,000 IU/day. Because of the relationship of bexarotene to vitamin A, patients should be advised to limit vitamin A supplements to avoid potential additive toxic effects. Photosensitivity: Retinoids as a class have been associated with photosensitivity. In vitro assays indicate that bexarotene is a potential photosensitizing agent. There were no reports of photosensitivity in patients in the clinical studies. Patients should be advised to minimize exposure to sunlight and artificial ultraviolet light during the use of Targretin gel.