Distribution of daunorubicin, a potent in vitro trypanocide which lacks in vivo activity, in the blood of trypanosome-infected mice

Method for Analysis, and Distribution Profile, of Covalently-linked Ferritin-daunorubicin Conjugate in the Blood of Trypanosome-infected Mice

Daunorubicin is a highly potent trypanocide in-vitro but is inactive in-vivo. When daunorubicin is conjugated to bovine serum albumin or horse spleen ferritin using Schiffs base linkages, the complex is trypanocidal in-vitro and in-vivo. We have developed novel analytical methods, using HPLC with fluorimetric detection, for the quantitation of daunorubicin and doxorubicin in biological samples, either as unconjugated drug, or when covalently linked to macromolecules or particles. Ferritin-daunorubicin conjugate (25 mg kg−1) was administered intraperitoneally to mice infected with monomorphic Trypanosoma brucei rhodesiense; peak plasma levels occurred after 1·5 h, and were 5 times higher than those resulting from administration of an equivalent amount of unconjugated daunorubicin. Plasma levels then declined rapidly (t½ for 1–6 h period was 0·58 and 0·86 h respectively for conjugated and unconjugated daunorubicin). However, higher plasma levels were seen 24 h after treatment, suggesting the distribution profile of daunorubicin when conjugated to ferritin is multiphasic with resultant high levels of daunorubicin obtained for a prolonged time period.

The trypanocidal effect of drugs in different parts of the brain

Three parts of the brain, cerebral cortex, lining of ventricle and choroid plexus, are cleared of trypanosomes to different extents by different drugs. There appear to be several barriers preventing drugs from acting in different parts of the brain, the concept of a single "blood-brain barrier" does not account for the phenomena observed. The protection of trypanosomes from certain drugs by the choroid plexus and ventricular wall supports the concept of an intracellular stage of Trypanosoma brucei in the ependymal cell; this concept is also supported by differences in parasitaemia resulting from the inoculation of ependymal and of other tissues. Alternative therapies for sleeping sickness are suggested, one of which (suramin/metronidazole) is being advanced for trials in man.