Conversion of liposomal 5-fluoro-2'-deoxyuridine and its dipalmitoyl derivative to bile acid conjugates of alpha-fluoro-beta-alanine and their excretion into rat bile

Polymeric curcumin nanoparticle pharmacokinetics and metabolism in bile duct cannulated rats

The objective of this study was to compare the pharmacokinetics and metabolism of polymeric nanoparticle-encapsulated (nanocurcumin) and solvent-solubilized curcumin formulations in Sprague-Dawley (SD) rats. Nanocurcumin is currently under development for cancer therapy. Since free, unencapsulated curcumin is rapidly metabolized and excreted in rats, upon intravenous (i.v.) administration of nanocurcumin only nanoparticle-encapsulated curcumin can be detected in plasma samples. Hence, the second objective of this study was to utilize the metabolic instability of curcumin to assess in vivo drug release from nanocurcumin. Nanocurcumin and solvent-solubilized curcumin were administered at 10 mg curcumin/kg by jugular vein to bile duct-cannulated male SD rats (n = 5). Nanocurcumin increased the plasma Cmax of curcumin 1749 fold relative to the solvent-solubilized curcumin. Nanocurcumin also increased the relative abundance of curcumin and glucuronides in bile but did not dramatically alter urine and tissue metabolite profiles. The observed increase in biliary and urinary excretion of both curcumin and metabolites for the nanocurcumin formulation suggested a rapid "burst" release of curcumin. Although the burst release observed in this study is a limitation for targeted tumor delivery, nanocurcumin still exhibits major advantages over solvent-solubilized curcumin, as the nanoformulation does not result in the lung accumulation observed for the solvent-solubilized curcumin and increases overall systemic curcumin exposure. Additionally, the remaining encapsulated curcumin fraction following burst release is available for tumor delivery via the enhanced permeation and retention effect commonly observed for nanoparticle formulations.

A new liposomal formulation of Gemcitabine is active in an orthotopic mouse model of pancreatic cancer accessible to bioluminescence imaging

Despite its rapid enzymatic inactivation and therefore limited activity in vivo, Gemcitabine is the standard drug for pancreatic cancer treatment. To protect the drug, and achieve passive tumor targeting, we developed a liposomal formulation of Gemcitabine, GemLip (Ø: 36 nm: 47% entrapment). Its anti-tumoral activity was tested on MIA PaCa-2 cells growing orthotopically in nude mice. Bioluminescence measurement mediated by the stable integration of the luciferase gene was employed to randomize the mice, and monitor tumor growth. GemLip (4 and 8 mg/kg), Gemcitabine (240 mg/kg), and empty liposomes (equivalent to 8 mg/kg GemLip) were injected intravenously once weekly for 5 weeks. GemLip (8 mg/kg) stopped tumor growth, as measured via in vivo bioluminescence, reducing the primary tumor size by 68% (SD +/- 8%; p < 0.02), whereas Gemcitabine hardly affected tumor size (-7%; +/- 1.5%). In 80% of animals, luciferase activity in the liver indicated the presence of metastases. All treatments, including the empty liposomes, reduced the metastatic burden. Thus, GemLip shows promising antitumoral activity in this model. Surprisingly, empty liposomes attenuate the spread of metastases similar to Gemcitabine and GemLip. Further, luciferase marked tumor cells are a powerful tool to observe tumor growth in vivo, and to detect and quantify metastases.

Pharmacokinetics of differently designed immunoliposome formulations in rats with or without hepatic colon cancer metastases

PURPOSE

Compare pharmacokinetics of tumor-directed immunoliposomes in healthy and tumor-bearing rats (hepatic colon cancer metastases).

METHODS

A tumor cell-specific monoclonal antibody was attached to polyethyleneglycol-stabilized liposomes, either in a random orientation via a lipid anchor (MPB-PEG-liposomes) or uniformly oriented at the distal end of the PEG chains (Hz-PEG-liposomes). Pharmacokinetics and tissue distribution were determined using [3H]cholesteryloleylether or bilayer-anchored 5-fluoro[3H]deoxyuridine-dipalmitate ([3H]FUdR-dP) as a marker.

RESULTS

In healthy animals clearance of PEG-(immuno)liposomes was almost log-linear and only slightly affected by antibody attachment; in tumor-bearing animals all liposomes displayed biphasic clearance. In normal and tumor animals blood elimination increased with increasing antibody density; particularly for the Hz-PEG-liposomes, and was accompanied by increased hepatic uptake, probably due to increased numbers of macrophages induced by tumor growth. The presence of antibodies on the liposomes enhanced tumor accumulation: uptake per gram tumor tissue (2-4% of dose) was similar to that of liver. Remarkably, this applied to tumor-specific and irrelevant antibody. Increased immunoliposome uptake by trypsin-treated Kupffer cells implicated involvement of high-affinity Fc-receptors on activated macrophages.

CONCLUSIONS

Tumor growth and immunoliposome characteristics (antibody density and orientation) determine immunoliposome pharmacokinetics. Although with a long-circulating immunoliposome formulation, efficiently retaining the prodrug FUdR-dP, we achieved enhanced uptake by hepatic metastases, this was probably not mediated by specific interaction with the tumor cells, but rather by tumor-associated macrophages.