In human HL-60 promyelocytic leukemia cells, diazepinylbenzoic acid derivatives can exhibit either antagonistic or synergistic effects on the differentiation-inducing activities of natural or synthetic retinoids, the activity depending largely on the nature of the substituents on the diazepine ring. Thus, a benzolog of the retinoid antagonist LE135 (6), 4-(13 H-10, 11, 12, 13-tetrahydro-10, 10, 13, 13, 15-pentamethyldinaphtho [2, 3-b][1, 2-e] diazepin-7-yl) ...