The present invention provides a tumour vasculature permeabilising molecule for use in permeabilising vasculature of a tumour for treating, detecting or diagnosing said tumour wherein said tumour vasculature permeabilising molecule is formulated for systemic administration to said patient. A composition comprising a tumour vasculature permeabilising molecule and an appropriate anticancer agent or imaging agent, and a method of treatment or a method of detecting the presence or absence of a tumour are also provided.