Suddenly, it seemed, Debbie Brown became permanently tired. She was so tired that she had to crawl up the stairs, and with any slight contact, she bruised. It was 1954, and Debbie, age 9, had leukemia.

A year earlier, Debbie would have died within months. But it was 1954, and Debbie's doctor knew about Dr. Joseph Burchenal's work at Memorial Sloan-Kettering Hospital in New York. After a referral, Burchenal's team gave Debbie two experimental drugs, 6-mercaptopurine (6-MP) and methotrexate--and a chance for survival.

The scientists who developed those drugs, which are still used in leukemia chemotherapy, did not stumble upon them in nature or in the laboratory. Instead, they set out to design the drugs, which were among the first ones ever made to order.

Without the drugs, Debbie had a life expectancy of 3 months; with them, she became perhaps the first long-term survivor of childhood leukemia. Although a cure was never mentioned, her visits to Burchenal became less frequent. In 1969, she had her first child, and she now teaches at a school in New Jersey.

The story of childhood leukemia did not end in 1954. In that year, Debbie was a lucky exception. To reach the nearly 80% cure rate of childhood leukemia seen today, doctors have had to marshal up to 12 drugs, used in complex combinations, and add transfusions and radiation therapy. But the drugs that gave doctors hope that this fast-moving disease was even worth tackling were the ones that cured Debbie Brown--the "antimetabolites."