Albumin nanocapsules containing fenretinide: pre-clinical evaluation of cytotoxic activity in experimental models of human non-small cell lung cancer

The present study deals with the preparation of albumin nanocapsules containing fenretinide and their evaluation in experimental models of human non-small cell lung cancer. These nanocapsules showed enhanced antitumor activity with respect to free fenretinide due to the solubilization effect of albumin on the hydrophobic drug, known to improve bioavailability. The high expression of caveolin-1 on the A549 cell surface further enhanced the antitumor activity of the nanoencapsulated fenretinide. Caveolin-1 favored albumin uptake and improved the efficacy of the fenretinide-loaded albumin nanocapsules, especially in 3-D cultures where the densely packed 3-D structures impaired drug diffusibility and severely reduced the activity of the free drug. The efficacy of the fenretinide albumin nanocapsules was further confirmed in tumor xenograft models of A549 by the significant delay in tumor progression observed with respect to control after intravenous administration of the novel formulation.

FROM THE CLINICAL EDITOR

This study describes the preparation of fenretinide containing albumin nanocapsules and their evaluation in experimental models of non-small cell lung cancer, showing enhanced antitumor activity compared to free fenretinide.

N-(4-hydroxyphenyl)retinamide promotes apoptosis of resting and proliferating B-cell chronic lymphocytic leukemia cells and potentiates fludarabine and ABT-737 cytotoxicity

The in vitro effects of the synthetic retinoid N-(4-hydroxyphenyl)retinamide (4HPR, fenretinide) on primary B-cell chronic lymphocytic leukemia (CLL) cells from previously untreated CLL patients were investigated. 4HPR promoted the intrinsic apoptotic pathway by reactive oxygen species (ROS) generation and was accompanied by drop of Mcl-1 protein expression. The latter was not attributable to transcriptional downregulation but to protein degradation mediated by jun N-terminal kinase activation, and likely by NF-kB downregulation and Noxa upregulation. CLL cells stimulated in vitro with CD40L did not increase 4HPR chemoresistance if activation was accompanied by proliferation. Intra-patient analysis confirmed that the proliferating pool of CLL cells was more sensitive to the cytotoxic action of 4HPR than the activated but resting CLL subpopulation. The different 4HPR susceptibility of the two subpopulations was associated with higher Noxa expression in proliferating CLLs. Combination experiments revealed that 4HPR strongly potentiated ABT-737 cytotoxicity, especially in proliferating CLL cells that displayed amplified chemoresistance to ABT-737 alone. Synergic cytotoxicity was also demonstrated in combination with fludarabine, in both resting and stimulated CLL samples. This study entitles 4HPR to be assayed as a chemotherapeutic adjuvant for the treatment of CLL.

Fenretinide metabolism in humans and mice: utilizing pharmacological modulation of its metabolic pathway to increase systemic exposure

BACKGROUND AND PURPOSE

High plasma levels of fenretinide [N-(4-hydroxyphenyl)retinamide (4-HPR)] were associated with improved outcome in a phase II clinical trial. Low bioavailability of 4-HPR has been limiting its therapeutic applications. This study characterized metabolism of 4-HPR in humans and mice, and to explore the effects of ketoconazole, an inhibitor of CYP3A4, as a modulator to increase 4-HPR plasma levels in mice and to increase the low bioavailability of 4-HPR.

EXPERIMENTAL APPROACH

4-HPR metabolites were identified by mass spectrometric analysis and levels of 4-HPR and its metabolites [N-(4-methoxyphenyl)retinamide (4-MPR) and 4-oxo-N-(4-hydroxyphenyl)retinamide (4-oxo-4-HPR)] were quantified by high-performance liquid chromatography (HPLC). Kinetic analysis of enzyme activities and the effects of enzyme inhibitors were performed in pooled human and pooled mouse liver microsomes, and in human cytochrome P450 (CYP) 3A4 isoenzyme microsomes. In vivo metabolism of 4-HPR was inhibited in mice.

KEY RESULTS

Six 4-HPR metabolites were identified in the plasma of patients and mice. 4-HPR was oxidized to 4-oxo-4-HPR, at least in part via human CYP3A4. The CYP3A4 inhibitor ketoconazole significantly reduced 4-oxo-4-HPR formation in both human and mouse liver microsomes. In two strains of mice, co-administration of ketoconazole with 4-HPR in vivo significantly increased 4-HPR plasma concentrations by > twofold over 4-HPR alone and also increased 4-oxo-4-HPR levels.

CONCLUSIONS AND IMPLICATIONS

Mice may serve as an in vivo model of human 4-HPR pharmacokinetics. In vivo data suggest that the co-administration of ketoconazole at normal clinical doses with 4-HPR may increase systemic exposure to 4-HPR in humans.