Pharmacokinetics of mitomycin-c lipidic prodrug entrapped in liposomes and clinical correlations in metastatic colorectal cancer patients

Background Pegylated liposomal (PL) mitomycin-c lipidic prodrug MLP) may be a useful agent in patients with metastatic colo-rectal carcinoma (CRC). We report here on the pharmacokinetics and clinical observations in a phase 1A/B study with PL-MLP. Methods Plasma levels of MLP were examined in 53 CRC patients, who received PL-MLP either as single agent or in combination with capecitabine and/or bevacizumab. MLP was determined by an HPLC-UV assay, and its pharmacokinetics was analyzed by noncompartmental methods. The correlation between clinical and pharmacokinetic parameters was statistically analyzed. Results PL-MLP was well tolerated with a good safety profile as previously reported. Stable Disease was reported in 15/36 (42%) of efficacy-evaluable patients. Median survival of stable disease patients (14.4 months) was significantly longer than of progressive disease patients (6.5 months) and non-evaluable patients (2.3 months). MLP pharmacokinetics was stealth-like with long T½ (~1 day), slow clearance, and small volume of distribution (Vd). The addition of capecitabine and/or bevacizumab did not have any apparent effect on the pharmacokinetics of MLP and clinical outcome. High baseline neutrophil count and CEA level were correlated with faster clearance, and larger Vd. Stable disease patients had longer T½ and slower clearance than other patients. T½ and clearance were significantly correlated with survival. Conclusions PL-MLP treatment results in a substantial rate of disease stabilization in metastatic CRC, and prolonged survival in patients achieving stable disease. The correlation of neutrophil count and CEA level with pharmacokinetic parameters of MLP is an unexpected finding that needs further investigation. The association of long T½ of MLP with stable disease and longer survival is consistent with an improved probability of disease control resulting from enhanced tumor localization of long-circulating liposomes and underscores the relevance of personalized pharmacokinetic evaluation in the use of nanomedicines.