The Pharmacology of a Novel Topical Retinoid, BMY 30123: Comparison with Tretinoin

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Abstract
Preclinical studies pertaining to the pharmacology and toxicology of BMY 30123 (4-acetamidophenyl retinoate) are reported. BMY 30123 is a novel compound which has topical retinoid activity. This compound exhibits lower toxicity, both local and systemic, than other clinically used topical retinoids such as tretinoin (all-trans retinoic acid) in animal models. BMY 30123 is effective in a number of retinoid sensitive skin models including the rhino mouse utriculi reduction assay, the mouse epidermal hyperplasia model and in the suppression of DNA synthesis in mouse skin stimulated with phorbol ester. BMY 30123 was equipotent with tretinoin in these topical models. In the rhino mouse model the ED30 values for BMY 30123 and tretinoin were 0·037 and 0·015 Mm, respectively. In addition, BMY 30123 was active in the UVB-induced photodamaged mouse model, another retinoid sensitive model. One of the problems associated with topically applied tretinoin is local irritation. Therefore, for topical therapy to be optimal, it is important to reduce or minimize local irritation. Repeated applications of BMY 30123 to rabbit skin resulted in low skin irritation. The first perceptible signs of skin irritation produced by BMY 30123 occurred at a dose 10 times higher than that observed for tretinoin. BMY 30123 also exhibits low retinoid activity after oral or i.p. administration in mice and produced no signs of hypervitaminosis A-related toxicity at twenty times the no effect dose of tretinoin. Because retinoids are effective modulators of epidermal growth and differentiation, this compound should be useful for the treatment of cutaneous disorders that exhibit altered epidermal differentiation such as acne, psoriasis, ichthyosis and epithelial tumours. While BMY 30123 and tretinoin are shown here to be equipotent in animal efficacy models, the low skin irritation activity gives BMY 30123, at a minimum, a 10-fold enhancement in the therapeutic index relative to tretinoin and suggests that retinoid efficacy and skin irritation are separable phenomena.