Phase I trials of single agents in adult solid tumours: preclinical and clinical aspects.

Considerable progress has been made in the treatment of cancer. However, there is still a need for new drug development. The preclinical antitumour activity of new anticancer agents is evaluated by sequential testing in murine tumours and human xenografts in mice. More recently, the human tumour stem cell assay has been introduced into the preclinical screen. Toxicology studies are done in animals in order to characterize qualitatively and quantitatively the side effects of the new compounds. These toxicology studies allow an appropriate starting dose to be selected for clinical trials. Most commonly, the starting dose for clinical trials corresponds to 1/10 of the dose that will induce a 10% lethality in the mouse (LD10), if that dose is tolerated by the dog. The escalation scheme for clinical trials must be a compromise between the safety of the patient and quickly reaching biologically active doses. This may be achieved by using the so-called modified Fibonacci scheme. A slightly more rapid alternative is to increase the dose by 100% until the equivalent of the LD10 in the mouse is reached, and then by 50% until toxic effects are observed. Further dose increases depend on the type and severity of these toxic side-effects. Patients included in phase I clinical trials of anticancer agents must have histologically proven malignant disease that cannot be treated by conventional therapeutic modalities. They should have normal haematological, renal and hepatic functions and should be expected to live long enough to evaluate properly the toxic effects of the new compounds.(ABSTRACT TRUNCATED AT 250 WORDS)