Current concepts of treatment in medical oncology: new anticancer drugs.

General principles for anticancer drug development include traditional drug-screening methods in biological test systems. Today, testing of a drug in a panel of selected human tumor xenografts in mice is assumed to have the best predictive value for clinical efficacy. Chemical modification of well-known antitumor drugs from compound groups such as purine analogs, vinca alkaloids, antifolates and platinum analogs are carried out to increase anticancer activity, to reduce toxic side-effects and to improve pharmacokinetic properties of the drugs. In the last decade the enormous development in molecular techniques has led to the discovery of key proteins that are intimately involved in the regulation of cancer growth control. Cell growth inhibitors could be developed by structure-based design, creating small organic molecules ("peptide mimetics") to target crucial enzymes, oncogenes or oncogene products, tumor-suppressor genes and their products as well as growth factors and their corresponding receptors. Drugs representing new leading structures, like alkylphosphocholines, topoisomerase I inhibitors, taxoids and suramin, have already entered the clinic. Novel therapeutic approaches may provide substantial progress in cancer treatment in the very near future. Examples are the concept of high-dose chemotherapy with hematopoietic stem cell support, the various strategies of gene therapy, the modulation of multi-drug resistance of cancer cells, and strategies to inhibit tumor angiogenesis.