The present invention relates to conjugates, in particular antibody-drug conjugates and immunotoxins, having the formula I: A-(L-D)p (I) or a pharmaceutically acceptable salts or solvates thereof, wherein: A is an antibody that selectively binds Endoglin； L is a linker； D is a drug comprising a cytolysin or a Nigrin-b A-chain； and p is 1 to 10, and to use of such conjugates in the therapeutic treatment of tumors. Methods of producing such conjugates and components for use in such methods are disclosed.
