Cell cycle phase sensitivity to cis-dichloro-bis (isopropylamine) trans-dihydroxy platinum (IV) (CHIP)

Cis-dichloro-bis (isopropylamine) trans-dihydroxy platinum (IV) (CHIP) is a second generation platinum coordination complex now in Phase II clinical trials. In vitro studies with Chinese Hamster Ovary cell cultures show that CHIP is a phase-sensitive drug, being most cytotoxic to cells in early G1 phase and least toxic to late S and G2 phase cells. The dose-modifying factor between the drug sensitivity of cells treated in G1 and in late S phase is 1.6. These findings and their clinical significance are discussed with respect to the phase sensitivity of other cytotoxic agents.