Cellular accumulation determines the activity of three novel tricyclic platinum agents.

BACKGROUND: Cisplatin (CDDP) is a very useful chemotherapeutic agent, but cellular resistance limits its efficacy in malignant glioma. In order to analyze and overcome this resistance, we synthesized three novel platinum compounds; aminoplatin, methylplatin and oxiplatin, using tricyclic DNA intercalating molecules as models. MATERIALS AND METHODS: The novel compounds differ only in one chemical group, which is positioned opposite to the DNA binding site. DNA binding, cellular penetration, and cytotoxicity were compared in three human glioma cell lines (T98G, U87-MG, and U25 IN) and a human fibroblast cell strain (HS 68). 2 RESULT: Binding to isolated DNA was most effective in aminoplatin, followed by methylplatin and oxiplatin. It differed by factors I. I, 0.35, 0.23, from the DNA binding of CDDP (factor I) for the three compounds, respectively. The cellular penetration, however, was fastest with oxiplatin (factor 10.1) followed by CDDP (1), aminoplatin (0.55), and methylplatin (0.27). The cytotoxicity of the three novel compounds followed the pattern of their cellular penetration with oxiplatin being the most active. U87-MG cells were resistant to CDDP, and in this cell line oxiplatin was more effective than CDDP in overcoming the resistance. CONCLUSION: This indicates cellular penetration to be an important feature and the ketogroup of oxiplatin to be beneficial in tricyclic platinum compounds.

Therapeutic drug monitoring of busulfan in transplantation.

Busulfan is the only agent used in myeloablative regimens for hematopoietic stem cell transplantation for which therapeutic drug monitoring (TDM) has been widely used. Studies of oral busulfan (Bu) indicate wide intrapatient and interpatient variations in pharmacokinetic (PK) behavior, particularly in children. Dose adjustments of oral Bu based on TDM to bring exposures within established therapeutic ranges have been shown to reduce toxicity and improve outcomes. Intravenous (IV) Bu is becoming more widely used and has much more predictable PK. Outcomes with IV Bu appear to be superior to those achieved using oral Bu without TDM. However there is still at least a threefold variation in exposures achieved by the same dose of IV Bu in different individuals and a small proportion of patients will experience toxic exposures with current dosing regimens. Therapeutic monitoring with appropriate dose adjustment is therefore recommended for all patients treated with regimens containing high doses of Bu. Giving IV Bu at a fixed rate to adults will narrow the range of exposures but more work is needed to establish the best dosing regimen to bring as many exposures as possible within the target range. Studies of test dosing of IV Bu show that this strategy is more accurate when test and treatment doses are infused at the same rate. Finally, targeting exposures to the upper end of the therapeutic range may provide a safe approach to exploiting dose-intensity for the treatment of some malignancies.