7-Chloro-5-(4-hydroxyphenyl)-1-methyl-3-(naphthalen-2-ylmethyl)-4,5-dihydro-1H-benzo[b][1,4]diazepin-2(3H)-one (Bz-423), a benzodiazepine, suppresses keratinocyte proliferation and has antipsoriatic activity in the human skin-severe, combined immunodeficient mouse transplant model.

7-Chloro-5-(4-hydroxyphenyl)-1-methyl-3-(naphthalen-2-ylmethyl)-4,5-dihydro-1H-benzo[b][1,4]diazepin-2(3H)-one (Bz-423) is a benzodiazepine that has cytotoxic and cytostatic activity against a variety of cells in vivo and in vitro. In the present study, we demonstrate that Bz-423 (formulated for topical delivery) reduces epidermal hyperplasia in human psoriatic skin after transplantation to severe, combined immunodeficient (scid) mice. Bz-423 also suppresses the hyperplasia that develops in nonpsoriatic human skin as a consequence of transplantation to scid mice. Proliferation of human epidermal keratinocytes in monolayer culture was suppressed by Bz-423 at concentrations of 0.5 to 2.0 muM (noncytotoxic concentrations). Keratinocyte growth inhibition was accompanied by increased oxidant generation in Bz-423-treated cells, and treatment with vitamin E along with Bz-423 reversed the growth inhibition. Growth inhibition was accompanied by a redistribution of beta-catenin from a cytoplasmic pool to the cell membrane and by reduced levels of c-myc and cyclin D1 (two molecules associated with Wnt pathway signaling). Several analogs of Bz-423 were examined for antiproliferative activity against human epidermal keratinocytes and human dermal fibroblasts in monolayer culture. Each of the analogs tested suppressed growth of both cell types, but in all cases, keratinocytes were more sensitive than fibroblasts. Two of the compounds were found to suppress epidermal hyperplasia induced with all-trans retinoic acid in organ cultures of human skin. Taken together, these data show that Bz-423 and certain analogs produce biological responses in skin cells in vitro and in vivo that are consistent with therapeutic goals for treating psoriasis or epidermal hyperplasia resulting from other causes.