 However the structural features of the NTD are undetermined due to a high degree of flexibility in its conformation.Both biochemical and circular dichroism spectroscopy analysis suggest that AR NTD is highly disordered under native conditions, making it a difficult target for drug discovery.In 2008 there were reports of a chlorinated peptide, sintokamide A, isolated from marine sponges that effectively inhibits AR N-terminal domain-activated reporter gene transcription, see figure 8.