Determination of a new polymer-bound paclitaxel derivative (PNU 166945), free paclitaxel and 7-epipaclitaxel in dog plasma and urine by reversed-phase high-performance liquid chromatography with UV detection

An effective method to produce 7-epitaxol from taxol in HCO3

It is known that 7-epitaxol has much stronger cytotoxicity than taxol does. However, the content of 7-epitaxol in yew is much less than taxol, which makes it more costly to obtain. We describe here a method to effectively convert taxol to 7-epitaxol. The key condition for reaction needs NaHCO₃ in solvent acetonitrile (ACN). The conversion rate can be over 82%.

Self-assembled PEGylated albumin nanoparticles (SPAN) as a platform for cancer chemotherapy and imaging

Paclitaxel (PTX) is used as a major antitumor agent for the treatment of recurrent and metastatic breast cancer. For the clinical application of PTX, it needs to be dissolved in an oil/detergent-based solvent due to its poor solubility in an aqueous medium. However, the formulation often causes undesirable complications including hypersensitivity reactions and limited tumor distribution, resulting in a lower dose-dependent antitumor effect. Herein, we introduce a facile and oil-free method to prepare albumin-based PTX nanoparticles for efficient systemic cancer therapy using a conjugate of human serum albumin (HSA) and poly(ethyleneglycol) (PEG). PTX were efficiently incorporated in the self-assembled HSA-PEG nanoparticles (HSA-PEG/PTX) using a simple film casting and re-hydration procedure without additional processes such as application of high pressure/shear or chemical crosslinking. The spherical HSA-PEG nanoparticle with a hydrodynamic diameter of ca. 280 nm mediates efficient cellular delivery, leading to comparable or even higher cytotoxicity in various breast cancer cells than that of the commercially available Abraxane^®. When systemically administered in a mouse xenograft model for human breast cancer, the HSA-PEG-based nanoparticle formulation exhibited an extended systemic circulation for more than 96 h and enhanced intratumoral accumulation, resulting in a remarkable anticancer effect and prolonged survival of the animals.

Synthesis, physico-chemical and biological characterization of a paclitaxel macromolecular prodrug

Paclitaxel was attached to poly(hydroxyethylaspartamide) via a succinic spacer arm by a two-step protocol: (1) synthesis of 2'-O-succinyl-paclitaxel; (2) synthesis of PHEA-2'-O-succinyl-paclitaxel. The 2'-O-succinyl-paclitaxel derivative and the macromolecular conjugate were characterized by UV, IR, NMR and mass spectrometry analysis. The reaction yields were over 95% and the purity of products over 98%. Paclitaxel release and degradation from 2'-O-succinyl-paclitaxel occurred at a faster rate at pH 5.5 than 7.4. After 30 h of incubation at pH 5.5 and 7.4 the released free paclitaxel was about 40 and 20%, respectively. In plasma both drug release and degradation were found to occur at a higher rate than in buffer at pH 7.4 suggesting that an enzymatic mechanism could be involved. The paclitaxel release and degradation from PHEA-2'-O-succinyl-paclitaxel were negligible at pH 5.5 and 7.4 and very slow in plasma. Investigation carried out using murine myeloid cell line showed that the polymeric prodrug maintains partial pharmacological activity of paclitaxel. The DL50 of the conjugate (over 40 ng/ml) as compared to free paclitaxel (about 1 ng/ml) was correlated to the slow drug release. Finally a pharmacokinetic study carried out by intravenous inoculation of the macromolecular prodrug to mice demonstrated that the polymer conjugation modify dramatically the in vivo fate of the drug. The conjugate disappeared from the bloodstream much more quickly as compared to both free drug and naked polymer. Massive accumulation of bioconjugate in the liver (80% of the dose) was found to persist throughout 1 week.

Synthesis and characterization of a catalytic antibody-HPMA copolymer-Conjugate as a tool for tumor selective prodrug activation

Selective chemotherapy remains a key issue for successful treatment in cancer therapy. The use of targeting approaches like the enhanced permeability and retention (EPR) effect of macromolecules, is consequently needed. Here, we report the preparation of a novel catalytic antibody-polymer conjugate for selective prodrug activation. HPMA copolymer was conjugated to catalytic antibody 38C2 through an amide bond formation between epsilon-amino group of lysine residue from the antibody molecule and a p-nitrophenyl ester of the polymer. The conjugate was purified over a size exclusion column using FPLC. In the isolated fraction, one or two molecules of polymer were conjugated to one molecule of antibody based on gel analysis. The resulting conjugate retained most of its catalytic activity (75-81%) in comparison to the free antibody. The activity was monitored with a fluorogenic substrate and a prodrug activation assay using HPLC. Furthermore, the conjugate was evaluated in vitro for its ability to activate an etoposide prodrug using two different cancer cell lines. Cells growth inhibition using the prodrug and the conjugate was almost identical to inhibition by the free antibody and the prodrug. For the first time, a catalytic antibody was conjugated to a passive targeting moiety while retaining its catalytic ability to activate a prodrug. The conjugate described in this work can be used for selective activation of prodrug in the PDEPT (polymer directed enzyme prodrug therapy) approach by replacing the enzyme component with catalytic antibody 38C2.

Determination of MAG-camptothecin, a new polymer-bound camptothecin derivative, and free camptothecin in dog plasma by HPLC with fluorimetric detection

A high throughput. selective and sensitive high-performance liquid chromatographic (HPLC) method for the determination of a water-soluble polymer-bound Camptothecin conjugate (MAG-CPT) and Camptothecin (CPT) in dog plasma has been developed and validated. The method involved the analysis of free and total CPT (free + polymer-bound). Free CPT (intact lactone plus carboxylate) was extracted from acidified plasma using Oasis SPE material in 96-well plates. For the assay of the total CPT, plasma proteins were first precipitated with methanol in a 96-well plate containing a 10-microm melt blown polypropylene membrane. The methanolic supernatant was separated and collected into a second 96-well plate by simply applying vacuum to the plate. After hydrolysis at pH 9.8 for 18 h and re-acidification, samples were injected directly from the collection plate onto the HPLC system. MAG-CPT concentration was then calculated by subtraction of free from total CPT. The LLOQs of the method were 1.17 ng/ml for free CPT and 103.10 ng/ml (as CPT equivalent) for MAG-CPT using 0.1 and 0.05 ml of plasma, respectively. Linearity, precision, accuracy and recovery of the method were evaluated. The stability of MAG-CPT in plasma alone and after its stabilisation was carefully evaluated. No interference from blank dog, mouse and human plasma was observed. The suitability of the method for in vivo samples was assessed by the analysis of samples obtained from dogs that had received a single and 5-day repeated dose of MAG-CPT.

High throughput on-line solid phase extraction/tandem mass spectrometric determination of paclitaxel in human serum

The feasibility of high throughput on-line solid phase extraction/tandem mass spectrometry (SPE/MS/MS) is tested for target analysis of paclitaxel in human serum. The use of a dual Prospekt system, with parallel SPE and elution directly to the mass spectrometer, resulted in a cycle time of 80 seconds for the entire, fully automated assay. The assay proved to be linear from 1 to 1000 ng/mL. Cartridges packed with small sorbent particles functioned both as SPE cartridges and as short analytical columns.