In 1956, C. Gordon Zubrod, who had formerly led the development of antimalarial agents for the United States Army, took over the Division of Cancer Treatment of the NCI and guided development of new drugs. In the two decades that followed the establishment of the NCCSC, a large network of cooperative clinical trial groups evolved under the auspices of the NCI to test anticancer agents. Zubrod had a particular interest in natural products, and established a broad programme for collecting and testing plant and marine sources, a controversial programme that led to the discovery of taxanes (in 1964) and camptothecins (in 1966). Both classes of drug were isolated and characterized by the laboratory of Monroe Wall at the Research Triangle Institute.