KW-2149 (7-N-[2-[GAMMA-L-GLUTAMYLAMINO]ETHYLDITHIO-ETHYL] MITOMYCIN-C) - DNA INTERACTIONS AND DRUG UPTAKE FOLLOWING SERUM ACTIVATION

7-N-[2-[gamma-L-glutamylamino]ethyldithio-ethyl] mitomycin C (KW-2149) is a mitomycin-C analogue currently being evaluated in clinical trial s. It has been shown that KW-2149 is unusual in that it is activated b y serum, resulting in an increase in potency of up to 200-fold. To inv estigate the mechanism by which KW-2149 is activated, the abilities of mitomycin C, KW-2149 and its metabolites M-18 (symmetrical disulphide dimer) and M-16 (methyl sulphide form) to interact with DNA were comp ared, and the influence of serum and glutathione on the sequence-speci ficity of KW-2149-DNA interactions was determined. Following reduction by glutathione both KW-2149 and M-18 are more efficient crosslinking agents of naked DNA, with the metabolite M-18 showing superior activit y. The efficiency of DNA interstrand crosslinking in cells by KW-2149 was also increased by the addition of serum. Using the potassium/SDS p recipitation method it was found that KW 2149 and M-18 crosslink prote in to DNA whilst mitomycin C and M-16 do not. All four compounds produ ced almost identical patterns of adducts. Serum and glutathione did no t alter the pattern of DNA adducts, but did increase the efficiency of adduct formation. Our earlier studies had indicated that the mechanis m of activation of KW-2149 by serum is related to cellular uptake, and we therefore studied the effects of certain metabolic inhibitors, tem perature and competitive inhibition on drug uptake. The results sugges t that uptake is passive, and this indicates that a component in serum modifies KW 2149 to a form that passively enters cells more rapidly. (C) 1998 Elsevier Science Inc.