Of the six subjects in Wu’s study, four had stage III cancer and 25 months after vaccination, there was no sign of tumors. In the other two subjects, who had stage IV melanomas, they saw improvement with additional checkpoint therapy. Likewise, in Sahin’s study, eight out of 13 initially tumor-free subjects remained tumor-free 23 months later; normally half of them would be expected to relapse, Vormehr says. Of five subjects who relapsed, two responded positively to the vaccine, and a third responded when the vaccine was combined with checkpoint blockade therapy. Looking more closely, both sets of researchers found that their subjects' immune systems were learning to react to the neoantigens.