In the winter of 1957, the leukemia group launched yet another modification to the first experiment. This time, one group received a combined regimen, while the other two groups were given one drug each. And with the question even more starkly demarcated, the pattern of responses was even clearer. Given alone, either of the drugs performed poorly, with a response rate between 15 and 20 percent. But when methotrexate and 6-MP were administered together, the remission rate jumped to 45 percent.
