An antibody directed against the endothelin receptor sub-type B comprising: - a heavy chain variable region comprising - a CDR1 (hereinafter designated CDR1 H) having the following consensus sequence: GYTFX 1 SYW (SEQ ID NO: 3) in which X 1 is either I, or T; - a CDR2 (hereinafter designated CDR2 H) having the following consensus sequence: IDPX 2 SGGT (SEQ ID NO: 8) in which X 2 represents either D, or N; and - a CDR3 (hereinafter designated CDR3 H) having the following consensus sequence: X 3 REGX 4 X 5 AWFX 6 Y (SEQ ID NO: 13) wherein X 3 is either A, or V; X 4 is chosen from the group consisting of D,W and E; X 5 is chosen from the group consisting of Y, D and F and X 6 is either A, or V; and - a light chain variable region comprising - a CDR1 (hereinafter designated CDR1 L) having the following consensus sequence: QX 7 !VHSNGX 8 TY (SEQ ID NO: 20) wherein X 7 is either N, or S and X 8 is either N, or Y; - a CDR2 (hereinafter designated CDR2 L) having the following consensus sequence: KVX 9 wherein X 9 is either S, or F; and - a CDR3 (hereinafter designated CDR3 L) having the following consensus sequence: FQGSHVPX 10 T (SEQ ID NO: 25) wherein X 10 is either W, or L; a fragment or derivative thereof, wherein said antibody and said fragment or derivative thereof are capable of recognising particular conformational isomers of the endothelin receptor sub-type B expressed at the surface of glioblastoma cells, wherein said fragment has at least one antigen-binding site and wherein said derivative is a single chain Fv. - a heavy chain variable region comprising - a CDR1 (hereinafter designated CDR1 H) having the following consensus sequence: GYTFX 1 SYW (SEQ ID NO: 3) in which X 1 is either I, or T; - a CDR2 (hereinafter designated CDR2 H) having the following consensus sequence: IDPX 2 SGGT (SEQ ID NO: 8) in which X 2 represents either D, or N; and - a CDR3 (hereinafter designated CDR3 H) having the following consensus sequence: X 3 REGX 4 X 5 AWFX 6 Y (SEQ ID NO: 13) wherein X 3 is either A, or V; X 4 is chosen from the group consisting of D,W and E; X 5 is chosen from the group consisting of Y, D and F and X 6 is either A, or V; and - a CDR1 (hereinafter designated CDR1 H) having the following consensus sequence: GYTFX 1 SYW (SEQ ID NO: 3) in which X 1 is either I, or T; - a CDR2 (hereinafter designated CDR2 H) having the following consensus sequence: IDPX 2 SGGT (SEQ ID NO: 8) in which X 2 represents either D, or N; and - a CDR3 (hereinafter designated CDR3 H) having the following consensus sequence: X 3 REGX 4 X 5 AWFX 6 Y (SEQ ID NO: 13) wherein X 3 is either A, or V; X 4 is chosen from the group consisting of D,W and E; X 5 is chosen from the group consisting of Y, D and F and X 6 is either A, or V; and - a light chain variable region comprising - a CDR1 (hereinafter designated CDR1 L) having the following consensus sequence: QX 7 !VHSNGX 8 TY (SEQ ID NO: 20) wherein X 7 is either N, or S and X 8 is either N, or Y; - a CDR2 (hereinafter designated CDR2 L) having the following consensus sequence: KVX 9 wherein X 9 is either S, or F; and - a CDR3 (hereinafter designated CDR3 L) having the following consensus sequence: FQGSHVPX 10 T (SEQ ID NO: 25) wherein X 10 is either W, or L; a fragment or derivative thereof, wherein said antibody and said fragment or derivative thereof are capable of recognising particular conformational isomers of the endothelin receptor sub-type B expressed at the surface of glioblastoma cells, wherein said fragment has at least one antigen-binding site and wherein said derivative is a single chain Fv. - a CDR1 (hereinafter designated CDR1 L) having the following consensus sequence: QX 7 !VHSNGX 8 TY (SEQ ID NO: 20) wherein X 7 is either N, or S and X 8 is either N, or Y; - a CDR2 (hereinafter designated CDR2 L) having the following consensus sequence: KVX 9 wherein X 9 is either S, or F; and - a CDR3 (hereinafter designated CDR3 L) having the following consensus sequence: FQGSHVPX 10 T (SEQ ID NO: 25) wherein X 10 is either W, or L;