Perhaps the best known of all recent antimalarial drugs is chloroquine. As antimalarial drugs were desperately needed during the war, it is startling to realize that chloroquine was first synthesized several years before the war and recognized at that time as having antimalarial activity. A delightfully frank account of its development shows some of the less scientific problems of discovery.

In 1934, H. Andersag, a chemist at the Bayer Laboratories in Elberfeld, prepared a which was first known as Resochin. It might be described as a simplified mepacrine, although it belonged to a substantially different class. For 10 years few people knew anything about it. Some limited laboratory and clinical tests at Bayer led to the belief that it was slightly too toxic to be acceptable. A closely related substance, which was given the name Sontochin, was also laid aside. Under cartel agreements, both the Winthrop Chemical Company in the United States and, later, the French firm of Specia were informed about Resochin and Sontochin. By this time, 1940, the German army had overrun France, and in Europe the of new drugs was made to needs.

In the USA, the need for into antimalarial drugs had naturally been foreseen. A program on the synthesis of new antimalarial drugs was at the National of Health in 1939 and formed the basis of a war program organized by the Committee on of the Office of Scientific and Development, National Council. The program scientists from the universities and industry, private , the US Army, the Navy and the Public Health Service, and included liaison with Great Britain and Australia. It was by a group of , subcommittees, and, from November 1943, by the Board for the of Malarial Studies. The search for new antimalarial agents the screening of some 16,000 , most of them for both suppressive and prophylactic activity against several avian malarias, a thorough study of the toxicology and pharmacology of many of the preparations in lower animals. the appraisal was of some 80 against the malarias of man.

A great deal of useful information was . Some people will regard such a massive exercise in organization with awe. To others it may seem like a recipe for disaster rather than for successful . It seems that the machinery did not work very well in discovering chloroquine. Under cartel agreements, the and properties both of Sontochin and of Resochin had been disclosed to the Winthrop Chemical Company. The reports interest for Sontochin to be synthesized and tested by the American company, and it was found to be active against malaria in canaries. Resochin was not at that time, but both were duly for purposes of patenting. The information very properly reached the of the for antimalarial under the Number SN-183 and was to various , committees, and subcommittees on the of Malarial Studies. History does not record what the members of these committees thought about it, or whether they had time to read their papers.

Meanwhile, P. Decourt, a French clinical to Specia, took samples of the drug to Tunisia for human trials. There he was helped by Jean Schneider, later a professor in the faculty at Paris. Schneider's trials were interrupted by the Allied invasion of North Africa in November 1942, and after the capture of Tunis, Schneider turned over his promising results and his remaining samples of Sontochin to the US Army.

In due course some of the drug reached the United States. Its chemical composition was determined at the Rockefeller in New York and found to be with the material synthesized at the Winthrop laboratories 3 years earlier. According to Coatney, this discovery havoc bordering on hysteria. "We had dropped the ball and in doing so had lost valuable time in the search for a synthetic antimalarial”. Naturally the lapse had to be covered up. The was given a new number and the biological declared secret.

Further trials on Sontochin, now SN-6911, confirmed its effectiveness, and also several ideas which resulted in the synthesis of a which was named SN-7618. It was made, but it was also found to be known already and to have been patented in the USA, along with Sontochin, by Winthrop. It was, in fact, a different salt of the same base as the original Bayer Resochin, and after much comparison with other related it became and was recognized formally in February 1946 under the name chloroquine. It had been synthesized and first tested in animals about 12 years earlier, and , or , twice. It has become the drug of choice for the American armed forces and for the World Health Organization, and has against the threat of resistant strains for a surprisingly long time.

Since this time much progress has been made in understanding the biology of plasmodia and new antimalarial drugs have been discovered. Primaquine, in the same family as the pre-war German drug patnaquin, as the most notable success of the great US wartime . Daraprim (pyritnethatnine), a very different substance, some years later from of more general , to which we shall return in the next . There are also more recent drugs and a different , based on advances immunology, is leading towards the development of vaccines. Much has been done to control mosquitoes too, but they, like the malaria parasites, have to in the face of new enemies. The great hope of eradicating malaria has faded: new battles must be fought and new weapons devised if even the present level of control is to be .