Hopes have just been dashed that an experimental immunotherapy will keep melanomas from spreading. The vaccine contained GM2, a molecule that is common on the outside of melanoma cells but limited on healthy cells. Previous studies had shown that melanoma patients with antibodies against GM2 did better than those without. However, in a new study of 1,300 people with melanomas that had not yet spread, GM2 vaccination did not help and may actually have made things worse. The phase III clinical trial was stopped early because people who received the vaccine were 1.2% more likely to relapse and 2.1% less likely to survive.