In vitro pharmacodynamics of CKD-602 in HT-29 cells.
CKD-602 (7-[2-(N-isopropylamino)ethyl]-(20S)-camptothecin) is a recently-developed synthetic camptothecin analogue and currently under clinical development by Chong Kun Dang Pharm (Seoul, Korea). CKD-602 showed potent topoisomerase inhibitory activity in vitro and broad antitumor activity against various human tumor cells in vitro and in vivo in animal models. This study describes the pharmacodynamics of the immediate and delayed cytotoxicity induced by CKD-602 in a human colorectal adenocarcinoma cell line, HT-29, and its intracellular drug accumulation by HPLC. The present study was designed to address whether the higher activity of CKD-602 with prolonged exposure is due to delayed exhibition of cytotoxicity and/or an accumulation of antiproliferative effect on continuous drug exposure. The drug uptake study was performed to determine whether the delayed cytotoxicity is due to a slow drug accumulation in cells. CKD-602 produced a cytotoxicity that was exhibited immediately after treatment (immediate effect) and after treatment had been terminated (delayed effect). Both the immediate and delayed effects of CKD-602 showed a time dependent decrease in IC50 values. Drug uptake was biphasic and the second equilibrium level was obtained as early as at 24 hr, indicating that the cumulative and delayed antitumor effects of CKD-602 were not due to slow drug uptake. On the other hand, CKD-602 treatment was sufficient to induce delayed cytotoxicity after 4 hr, however, longer treatment (>24 hr) enhanced its cytotoxicity due to the intracellular accumulation of the drug, which requires 24 hr to reach maximum equilibrium concentration. In addition, Cn x T=h analysis (n=0.481) indicated that increased exposure times may contribute more to the overall antitumor activity of CKD-602 than drug concentration. Additional studies to determine the details of the intracellular uptake kinetics (e.g., concentration dependency and retention studies) are needed in order to identify the optimal treatment schedules for the successful clinical development of CKD-602.
Park
In-Sook
IS
Department of Pharmacology, National Institute of Toxicological Research, Korea Food and Drug Administration, Eunpyung-ku.
Ahn
Mee Ryung
MR
Suh
Soo Kyung
SK
Choi
Hong-Serck
HS
Sohn
Soo Jung
SJ
Yang
Ji Sun
JS
Yoo
Tae Moo
TM
Kuh
Hyo-Jeong
HJ
D002166:Camptothecin / Q000031:analogs & derivatives* / Q000493:pharmacokinetics / Q000494:pharmacology* / Q000633:toxicity; D004354:Drug Screening Assays, Antitumor / Q000379:methods; D019073:HT29 Cells; D006801:Humans
C116963:belotecan; D002166:Camptothecin