IX 207-887 neither affects the adherence of human monocytes nor markedly inhibits IL-1 or IL-2-induced thymocyte proliferation. In the chondrocyte test no IL-1 antagonistic activity of IX 207-887 can be observed.IX 207-887 is a novel antiarthritic agent which inhibits the release of interleukin-1 (IL-1) from human monocytes and mouse peritoneal macrophages. In all test systems IX 207-887 significantly reduces both biologically active and immunoreactive IL-1 in culture media, whereas the levels of IL-1 in homogenates or lysates are either unaffected or only marginally reduced.