Abstract: The present invention pertains to the provision of trimeric binding units which bind to trimeric cytokines. In particular there is provided a trimeric polypeptide comprising a trimerising domain and three monomers with binding members capable of binding a trimeric cytokine. Preferably, the trimeric binding units bind in a manner such that upon binding, all receptor binding sites of the trimeric cytokine are substantially blocked, and hence the potential biological activity of the trimeric cytokine is suppressed. In one aspect the invention relates to trimeric binders capable of binding to trimeric cytokines of the Tumor necrosis factor ligand superfamily, such as TNF, TRAIL, RANKL, TWEAK, APRIL and BAFF.