An anti-idiotype murine monoclonal antibody (MoAb) specific to P3 MoAb with anti-metastatic effect. Racotumomab binds to the idiotype region of P3 MoAb and functionally mimics the three-dimensional structure of N-glycolyl ceramides of mono-sialyl lactose, the antigenic target of P3. As a result, this anti-idiotype antibody may stimulate the host immune system to elicit humoral and cellular immune responses against tumour cells expressing NeuGc-GM3 gangliosides, which are expressed in a wide variety of tumour cells.