HPLC AND P-31 NMR CHARACTERIZATION OF THE REACTION BETWEEN ANTITUMOR PLATINUM AGENTS AND THE PHOSPHOROTHIOATE CHEMOPROTECTIVE AGENT S-2-(3-AMINOPROPYLAMINO)ETHYLPHOSPHOROTHIOIC ACID (WR-2721)
Dc. Thompson et al., HPLC AND P-31 NMR CHARACTERIZATION OF THE REACTION BETWEEN ANTITUMOR PLATINUM AGENTS AND THE PHOSPHOROTHIOATE CHEMOPROTECTIVE AGENT S-2-(3-AMINOPROPYLAMINO)ETHYLPHOSPHOROTHIOIC ACID (WR-2721), Biochemical pharmacology, 50(9), 1995, pp. 1413-1419
In prior studies, we examined the effects of the radioprotective and c
hemoprotective agent WR-2721 [S-2-(3-aminopropylamino)ethylphosphoroth
ioic] on the in vivo biotransformation of the cisplatin [cisdiamminedi
chloroplatinum(II)] analog ormaplatin ans-1,2-diaminocyclohexanetetrac
hloroplatinum(IV), Pt(dach)Cl-4, (formerly called tetraplatin)]. Those
data suggested that a direct interaction between WR-2721 and ormaplat
in and/or the corresponding Pt(II) drug, Pt(dach)Cl-2, may be occurrin
g in vivo. This would be in contrast to the generally accepted hypothe
sis that WR-2721 is a prodrug that must first be converted by alkaline
phosphatase to a free thiol compound, WR-1065, before any appreciable
reactivity would be evident. However, the major biotransformation pro
duct observed in the peritoneal fluid, plasma, and all tissues was Pt(
dach)(WR-1065). We report here on further investigations into the in v
itro reactivity of Pt(dach) compounds with WR-2721 and WR-1065. Separa
tion of reaction products resulting from incubation of Pt(dach)(malona
to) with either WR-2721 or WR-1065 under physiological conditions gave
profiles that were indistinguishable by reverse phase HPLC and cation
exchange HPLC at two different pHs. P-31 NMR characterization of the
dephosphorylation of WR-2721 revealed essentially no loss of inorganic
phosphate for up to 24 hr when incubated in unbuffered water at 30 de
grees. In contrast, when incubated with a 1:1 molar ratio of cisplatin
under the same conditions, the WR-2721 signal was decreased markedly
in the first 5 min, and had disappeared almost completely by 1 hr. The
signal corresponding to inorganic phosphate increased in parallel to
the decrease in the WR-2721 signal. No intermediate formation of a com
plex containing both platinum and phosphate could be detected at any t
ime. These data suggest that the reaction between WR-2721 and platinum
complexes results in rapid dephosphorylation of WR-2721, and, consequ
ently, that the reaction products formed with either WR-2721 or WR-106
5 and Pt(II) complexes are identical.