Racotumomab–alum vaccine is an anti-idiotypic vaccine able to mimic the tumor-associated antigen NeuGcGM3. Different Phase I clinical trials and compassionate use studies demonstrated its low toxicity and capacity to induce a strong anti-NeuGcGM3 response, able to bind and directly kill tumor cells expressing the antigen. A Phase II/III randomized double-blind clinical trial in advanced non-small cell lung cancer patients showed a significant improvement in overall survival and progression-free survival for racotumomab–alum versus placebo. Patients who developed anti-NeuGcGM3 antibodies capable of binding and killing NeuGcGM3 expressing tumor cells showed significantly longer median survival times. The impact of using racotumomab–alum as switch maintenance followed by second-line therapy is currently being explored in a new randomized, multinational Phase III study.