24 



Museum in Honolulu), respectively, in 1986, and were renewed for a further five years in 

 1991. 



In the microbial cultivation contracts, major use has been made of cultures from established 

 collections, such as the American Type Culture Collection. Marine collections have been 

 performed in the territorial waters of a number of countries, including Australia, Federated 

 States of Micronesia, New Zealand, Papua New Guinea, Philippines and Thailand. Plant 

 collections in Africa have been carried out in Cameroon, Central African Republic, Gabon, 

 Ghana, Madagascar, and Tanzania. In Central and South America, plant collections have 

 focussed on Belize, Bolivia, Colombia, Dominica, Dominican Republic, Guatemala, 

 Honduras, Martinique, Paraguay, Peru, and Puerto Rico, while in Southeast Asia, collections 

 have been performed in Indonesia (through the Arnold Arboretum), Malaysia, Nepal, Papua 

 New Guinea (through the Bishop Museum), Philippines, Taiwan and Thailand. 



DRUG DISCOVERY AND DEVELOPMENT 



Dried plant samples and frozen marine macro-organisms are delivered to the Natural Products 

 Repository (NPR) at the Frederick Cancer Research and Development Center (FCRDC), 

 where they are stored frozen. Aqueous and organic solvent extracts are made by the 

 Extraction and Grinding Laboratory at FCRDC, and are also stored frozen at the NPR, as are 

 microbial extracts and microbial culture samples. Extracts are tested in vitro for potential 

 antitumor activity against the panel of human cancer cell lines representing major disease- 

 types, such as breast, colon, lung, and melanoma. As mentioned earlier, the screen currently 

 comprises 60 cell lines. Anti-HIV testing is performed in vitro against a single human 

 lymphoblastoid cell line infected with the AIDS virus. The NPR, extraction and screening 

 laboratories are operated in NCI facilities at FCRDC by a contractor. Program Resources, 

 Inc. 



Active extracts are purified by NCI chemists using bioassay-guided fractionation. In 

 bioassay-guided fractionation, all fractions produced at each stage of the separation procedure 

 are tested for activity in the relevant bioassay, and subsequent fractionation steps are only 

 performed on those fractions showing significant activity. This process of fractionation and 

 testing is continued until the pure active constituent(s) is isolated. Bioassay-guided 

 fractionation is essential since, in most instances, the active constituents are present in only 

 small amounts in the crude extracts, and are generally isolated in yields of .01 percent or 

 less, based on the mass of material. After the active constituent is isolated from an extract, 

 its complete chemical structure is elucidated using modem spectroscopic techniques, and, if 

 necessary and possible, x-ray crystallography. This isolation and structural elucidation of a 

 potential new agent is but the first phase in a lengthy process of development towards clinical 

 trials, and possible general clinical use. At any one time the total number of compounds 

 being pursued at this stage for anti-HIV and anti-cancer activities is between 50-75. 



Agents showing significant activity in the primary in vitro human cancer cell line or anti-HIV 

 screens are entered into various stages of preclinical development to determine their suitability 



