METABOLISM AND PHARMACOKINETICS OF THE ANTITUMOR AGENT ,3,5-TRIMETHYL-6-(3-PYRIDYLMETHYL)1,4-BENZOQUINONE (CV-6504)

2,3,5-Trimethyl-6-(3-pyridylmethyl) 1,4-benzoquinone (CV-6504) is an e ffective inhibitor of the growth of established murine adenocarcinomas (MACs) and is shortly to enter clinical investigation. When administe red to mice bearing the MAC16 tumour, CV-6504 rapidly disappeared from the plasma and tissues and there was an accumulation of the sulphate and glucuronide metabolites. After 24 h, the concentration of free CV- 6504 in the tumour (3.3 mu M) was higher than that in the liver (0.24 mu M) and equal to the IC50 value for the inhibition of the growth of MAC16 cells in vitro (3 mu M). The concentration of glucuronide and su lphate metabolites in both tumour and liver decreased with time. Both the MAC16 tumour and the liver possessed similar beta-glucuronidase ac tivity, which could account for the accumulation of free CV-6504. Alth ough the sulphate and glucuronide conjugates of CV-6504 were ineffecti ve inhibitors of the growth of MAC13 cells in vitro at concentrations up to 100 mu M, in vivo at a concentration of 50 mg kg(-1) day(-1) the conjugates produced a similar anti-tumour effect to CV-6504 at a conc entration of 5 mg kg(-1) day(-1). The MAC13 tumour possessed both beta -glucuronidase and sulphatase activity capable of converting the sulph ate and glucuronide conjugates to free CV-6504. Using MAC13 cells ex v ivo, CV-6504 inhibited conversion of arachidonic acid to 5-, 12- and 1 5-hydroxyeicosatetraenoic acids (HETE). The percentage reduction in fo rmation of 12- and 15-HETE exceeded that of 5-HETE. Inhibition of HETE formation may be responsible for the anti-tumour activity of CV-6504.