Relationship between Drug Release of DE-310, Macromolecular Prodrug of DX-8951f, and Cathepsins Activity in Several Tumors

Abstract

Utilization of drug delivery systems is an attractive approach to improving efficacy and safety of anticancer drugs. Long-circulating macromolecular or particulate carriers are known to preferentially accumulate in solid tumors, due to the "enhanced permeability and retention (EPR)" effect, 1) i.e., leakiness of tumor angiogenic blood vessels and lack of effective lymphatic drainage. SMANCS (neocartinostatin polymer conjugate), Doxil (doxorubicin liposome), and Daunozome (daunorubicin liposome) 2,3) that exploit the EPR effect have already been launched in the market. Besides, PK1 (doxorubicin-HPMA polymer), 4) XYOTAX (paclitaxelpolyglutamate), 5) and NK911 (doxorubicin micelle) 6) are under clinical investigation.DE-310 is a novel macromolecular prodrug of the topoisomerase-I inhibitor (1S,9S)-1-amino-9-ethyl-5-fluoro-1,2,3,9,12,15-hexahydro-9-hydroxy-4-methyl-10H,13H-benzo[de]-pyrano) [3Ј,4Ј:6,7]indolizino[1,2-b]quinoline-10,13-dione (DX-8951).7) DX-8951 is covalently linked with carboxymethyl dextran polyalcohol (CM-Dex-PA) via the Gly-Leu-Phe-Gly (GGFG) tetrapeptide spacer (Fig. 1). 7) It has been demonstrated that a single dose of 11.4 mg/kg DE-310 exhibited stronger anti-tumor activity in mice than repeated doses (10 mg/kg daily for 5 d) of DX-8951f (exatecan; DX-8951 monomethansulfonate salt).8) Taking into account that DX-8951f belongs to time-dependent anti-cancer drugs, 9) slow release of DX-8951 from DE-310 in addition to long-term retention in tumor tissues would have been beneficial in exhibiting such an effective anti-tumor activity.The peptide spacer of DE-310 was designed to be cleaved by cysteine protease, cathepsins. Expression of cathepsins B, H, and L in tumor tissues and their involvement in tumor progression have been indicated. 10) Cathepsin B is expressed more highly in malignant tumors 11) and is responsible for destruction of basal membranes, processing of matrix proteases, and inactivation of protein inhibitors.12) On the other hand, cathepsin H is highly expressed in colon cancer cells, 13) and cathepsin L is secreted in metastatic bone marrow tumor.14) It is likely that the level of cathepsin species in tumor tissues would be one of the factors determining antitumor activity of DE-310.In this study, we examined the drug release from DE-310 by cathepsins B, H, and L obtained from human liver to identify the products of hydrolysis and determine the rate of hydrolysis for each cathepsin species. Then, we examined in vitro drug release from DE-310 in different murine or human tumor cell types, in addition to the activity or expression of cathepsins B, H and L in the cells. Correlation between the drug release and cathepsin levels was analyzed to quantitatively delineate the mechanism of drug release from DE-310. In addition, tumor tissue distribution of DE-310 was investi-

Silencing of Cathepsin B suppresses the proliferation and invasion of endometrial cancer

“…We showed that inhibition of Cathepsin B significantly decreased the proliferation of cancer cells, and that suppression of Cathepsin B significantly attenuated migration and invasive activity of HEC-1A cells. These findings are in agreement with those reported for other types of tumors (26,27). Taken together, these results suggest Cathepsin B has metastatic potential in EC cells.…”

Cancer Therapies Utilizing the Camptothecins: A Review of the in Vivo Literature

“…295 The release of drug through the amino acid linker cleavage was also determined to be mainly due to the activity of cathepsin B in the tumor. 296 Another study shows evidence of meningocele induction in rat fetuses after their mothers received four i.v. doses of 0.3 mg/kg or a single dose of 1 mg/kg.…”

Systematic Research of Peptide Spacers Controlling Drug Release from Macromolecular Prodrug System, Carboxymethyldextran Polyalcohol−Peptide−Drug Conjugates

“…In this context, we combinatorially synthesized 225 fluorogenic macromolecular prodrugs with a CM-Dex-PA backbone and evaluated sequence dependence of amino acid spacers on the rate of drug release by tumor-associated proteases. We intended to evaluate structure-activity relationship of drug release under rather physiologically relevant conditions (i.e., tumor cell homogenates) than by individual cathepsins, since it was obvious that multiple proteases including cathepsins B and L are responsible for hydrolysis of the same type of macromolecular prodrugs (17).…”

“…Considering the pH dependence on the cathepsin activities associated with Meth A tumor homogenate (17), the drug release assay of the conjugates was performed at pH 4.5. When CM-Dex-PA-Gly-Gly-P 2 -P 1 -DNS was incubated, not only DNS but its peptide conjugate (P 1 -DNS and P 2 -P 1 -DNS) were detected by HPLC.…”