Synthesis and Biological Investigation of Bile Acid-Paclitaxel Hybrids.

Chenodeoxycholic acid and ursodeoxycholic acid (CDCA and UDCA, respectively) have been conjugated with paclitaxel (PTX) anticancer drugs through a high-yield condensation reaction. Bile acid-PTX hybrids (BA-PTX) have been investigated for their pro-apoptotic activity towards a selection of cancer cell lines as well as healthy fibroblast cells. Chenodeoxycholic-PTX hybrid (CDC-PTX) displayed cytotoxicity and cytoselectivity similar to PTX, whereas ursodeoxycholic-PTX hybrid (UDC-PTX) displayed some anticancer activity only towards HCT116 colon carcinoma cells. Pacific Blue (PB) conjugated derivatives of CDC-PTX and UDC-PTX (CDC-PTX-PB and UDC-PTX-PB, respectively) were also prepared via a multistep synthesis for evaluating their ability to enter tumor cells. CDC-PTX-PB and UDC-PTX-PB flow cytometry clearly showed that both CDCA and UDCA conjugation to PTX improved its incoming into HCT116 cells, allowing the derivatives to enter the cells up to 99.9%, respect to 35% in the case of PTX. Mean fluorescence intensity analysis of cell populations treated with CDC-PTX-PB and UDC-PTX-PB also suggested that CDC-PTX-PB could have a greater ability to pass the plasmatic membrane than UDC-PTX-PB. Both hybrids showed significant lower toxicity with respect to PTX on the NIH-3T3 cell line.

Balancing the efficacy vs. the toxicity of promiscuous natural products: Paclitaxel-based acid-labile lipophilic prodrugs as promising chemotherapeutics.

TumorSelect® is an anticancer technology that combines cytotoxics, nanotechnology, and knowledge of human physiology to develop innovative therapeutic interventions with minimal undesirable side effects commonly observed in conventional chemotherapy. Tumors have a voracious appetite for cholesterol which facilitates tumor growth and fuels their proliferation. We have transformed this need into a stealth delivery system to disguise and deliver anticancer drugs with the assistance of both the human body and the tumor cell. Several designer prodrugs are incorporated within pseudo-LDL nanoparticles, which carry them to tumor tissues, are taken up, internalized, transformed into active drugs, and inhibit cancer cell proliferation. Highly lipophilic prodrug conjugates of paclitaxel suitable for incorporation into the pseudo-LDL nanoparticles of the TumorSelect® delivery vehicle formulation were designed, synthesized, and evaluated in the panel of 24-h NCI-60 human tumor cell line screening to demonstrate the power of such an innovative approach. Taxane prodrugs, viz., ART-207 was synthesized by tethering paclitaxel to lipid moiety with the aid of a racemic solketal as a linker in cost-effective, simple, and straightforward synthetic transformations. In addition to the typical 24-h NCI screening protocol, these compounds were assessed for growth inhibition or killing of ovarian cell lines for 48 and 72h-time intervals and identified the long-lasting effectiveness of these lipophilic prodrugs. All possible, enantiomerically pure isomers of ART-207 were also synthesized, and cytotoxicities were biosimilar to racemic ART-207, suggesting that enantiopurity of linker has a negligible effect on cell proliferation. To substantiate further, ART-207 was evaluated for its in vivo tumor reduction efficacy by studying the xenograft model of ovarian cancer grown in SCID mice. Reduced weight loss (a measure of toxicity) in the ART-207 group was observed, even though it was dosed at 2.5x the paclitaxel equivalent of Abraxane®. As a result, our delineated approach is anticipated to improve patient quality of life, patient retention in treatment regimes, post-treatment rapid recovery, and overall patient compliance without compromising the efficacy of the cytotoxic promiscuous natural products.

Fluorinated paclitaxel prodrugs for potentiated stability and chemotherapy.

Robust colloidal stability is an essential prerequisite for effective drug delivery. Herein, a series of fluorinated paclitaxel prodrugs bridged with redox-responsive linkages were synthesized, and the effect of fluorination on the assembly behavior and physiological stability was investigated. The 17-fluorinated ethanol-modified paclitaxel prodrug could self-assemble into stable nanoparticles without the addition of any surfactants. Fluorinated paclitaxel prodrug nanoparticles possessed potent cytotoxicity toward cancer cells and superior antitumor activity. This study offers a universal fluorination approach to improve drug delivery efficacy by enhancing the self-assembly capability and improving the colloidal stability of prodrugs for potentiating chemotherapy.

Pulmonary Delivery of Reactive Oxygen Species/Glutathione-Responsive Paclitaxel Dimeric Nanoparticles Improved Therapeutic Indices against Metastatic Lung Cancer.

Chemotherapeutics often failed to elicit optimal antitumor responses against lung cancer due to their limited exposure and accumulation in tumors. To achieve an effective therapeutic outcome of paclitaxel (PTX) against metastatic lung cancer with attenuated systemic and local toxicities, pulmonary delivery of redox-responsive PTX dimeric nanoparticles (NPs) was introduced. PTX dimers conjugated through variable lengths of diacid linkers containing disulfide bonds (-SS-) (i.e., α-PTX-SS-PTX, ß-PTX-SS-PTX, and γ-PTX-SS-PTX) were initially synthesized and were subsequently self-assembled into uniform nanosized particles in the presence of vitamin E TPGS with high drug loading capacity (DE > 97%). Among various redox-sensitive scaffolds, ß-PTX-SS-PTX NPs exhibited an optimal reactive oxygen species/glutathione-responsive drug release behavior, causing a lower local toxicity profile of PTX in the lungs. The scaffolds also demonstrated excellent colloidal stability, cellular uptake efficiency, and discriminating cytotoxicity between cancer and healthy cells. Further, they depicted an improved lung retention as compared to the control nanovesicles (ß-PTX-CC-PTX) devoid of the redox-sensitive disulfide motif. In the B16F10 melanoma metastatic lung cancer mouse model, intratracheally delivered ß-PTX-SS-PTX NPs exhibited a stronger anticancer potential with reduced systemic toxicity as compared to Taxol intravenous injection containing an equivalent PTX dose. The PTX dimeric NPs could also dramatically reduce the local toxicity relative to Taxol following their pulmonary delivery. Thus, this study presents redox-responsive PTX dimeric NPs as a promising nanomedicine for improved therapeutic efficacy against metastatic lung cancer.

Synthesis of small molecules targeting paclitaxel-induced MyD88 expression in triple-negative breast cancer cell lines.

Acquired paclitaxel (PTX) chemoresistance in triple-negative breast cancer (TNBC) can be inferred from the overexpression of toll-like receptor 4 (TLR4) and myeloid differentiation primary response 88 (MyD88) proteins and the activation of the TLR4/MyD88 cascading signalling pathway. Finding a new inhibitor that can attenuate the activation of this pathway is a novel strategy for reducing PTX chemoresistance. In this study, a series of small molecule compounds were synthesised and tested in combination with PTX against TNBC cells. The trimethoxy-substituted compound significantly decreased MyD88 overexpression and improved PTX activity in MDA-MB-231TLR4+ cells but not in HCCTLR4- cells. On the contrary, the trifluoromethyl-substituted compound with PTX synergistically improved the growth inhibition in both TNBC subtypes. The fluorescence titrations indicated that both compounds could bind with MD2 with good and comparable binding affinities. This was further supported by docking analysis, in which both compounds fit perfectly well and form some critical binding interactions with MD2, an essential lipid-binding accessory to TLR4 involved in activating the TLR-4/MyD88-dependent pathway.

Asymmetric Total Synthesis of Taxol.

Taxol is one of the most famous natural diterpenoids and an important anticancer medicine. Taxol represents a formidable synthetic challenge and has prompted significant interest from the synthetic community. However, in all the previous syntheses of Taxol, there have been no reports of closing the desired eight-membered ring through C1-C2 bond formation. Furthermore, the existence of Taxol-resistant tumors and side effects of Taxol make the development of new approaches to synthesize Taxol and its derivatives highly desirable. Here, we report the asymmetric total synthesis of Taxol using a concise approach through 19 isolated intermediates. The synthetically challenging eight-membered ring was constructed efficiently by a diastereoselective intramolecular SmI2-mediated pinacol coupling reaction to form the C1-C2 bond. The unique biomimetic oxygen ene reaction and the newly developed facile tandem C2-benzoate formation and C13 side chain installation improved the efficiency of the synthesis. The mild oxygen ene reaction under light conditions would be an alternative reaction involved in Taxol biosynthesis. This new convergent approach will allow the diverse creation of Taxol derivatives to enable further biological research.

Exquisite Vesicular Nanomedicine by Paclitaxel Mediated Co-assembly with Camptothecin Prodrug.

We report that the self-assembly of drug amphiphiles, Evans blue conjugated camptothecin prodrug (EB-CPT), can be modulated by another anticancer drug paclitaxel (PTX), resulting in ultrahigh quality of nanovesicles (NVs) with uniform shape and diameters of around 80 nm with the EB-CPT:PTX weight ratio of 1:1, 1:2, and 1:3, denoted as ECX NVs. Significantly, the co-assembly of EB-CPT and PTX without adding other excipients has nearly 100 % drug loading efficiency (DLE) and ultrahigh drug loading content (DLC) of PTX alone of up to 72.3±1.7 wt % which, to our best knowledge, is among the highest level reported in literature. Moreover, the ECX NVs with the EB-CPT:PTX weight ratio of 1:2 showed remarkable combination index of 0.59 at a level of 50 % efficacy against HCT116 cells in vitro and greatly improved tumor inhibition effect in vivo compared with two clinically approved CPT- and PTX-based anticancer nanomedicines (Onivyde and Abraxane) individually and their combinations.

Paclitaxel and naringenin-loaded solid lipid nanoparticles surface modified with cyclic peptides with improved tumor targeting ability in glioblastoma multiforme.

The present work describes the systematic development of paclitaxel and naringenin-loaded solid lipid nanoparticles (SLNs) for the treatment of glioblastoma multiforme (GBM). So far only temozolomide therapy is available for the GBM treatment, which fails by large amount due to poor brain permeability of the drug and recurrent metastasis of the tumor. Thus, we investigated the drug combination containing paclitaxel and naringenin for the treatment of GBM, as these drugs have individually demonstrated significant potential for the management of a wide variety of carcinoma. A systematic product development approach was adopted where risk assessment was performed for evaluating the impact of various formulation and process parameters on the quality attributes of the SLNs. I-optimal response surface design was employed for optimization of the dual drug-loaded SLNs prepared by micro-emulsification method, where Percirol ATO5 and Dynasan 114 were used as the solid lipid and surfactant, while Lutrol F188 was used as the stabilizer. Drug loaded-SLNs were subjected to detailed in vitro and in vivo characterization studies. Cyclic RGD peptide sequence (Arg-Gly-Asp) was added to the formulation to obtain the surface modified SLNs which were also evaluated for the particle size and surface charge. The optimized drug-loaded SLNs exhibited particle size and surface charge of 129 nm and 23 mV, drug entrapment efficiency >80% and drug loading efficiency >7%. In vitro drug release study carried out by micro dialysis bag method indicated more than 70% drug was release observed within 8 h time period. In vivo pharmacokinetic evaluation showed significant improvement (p < 0.05) in drug absorption parameters (Cmax and AUC) from the optimized SLNs over the free drug suspension. Cytotoxicity evaluation on U87MG glioma cells indicated SLNs with higher cytotoxicity as compared to that of the free drug suspension (p < 0.05). Evaluation of uptake by florescence measurement indicated superior uptake of SLNs tagged with dye over the plain dye solution. Overall, the dual drug-loaded SLNs showed better chemoprotective effect over the plain drug solution, thus construed superior anticancer activity of the developed nanoformulation in the management of glioblastoma multiforme.

Preparation and in vitro evaluation of amphiphilic paclitaxel small molecule prodrugs and enhancement of oral absorption.

A series of novel amphiphilic paclitaxel (PTX) small molecule prodrugs, PTX-succinic anhydride-cystamine (PTX-Cys), PTX-dithiodipropionic anhydride (PTX-SS-COOH) and PTX-succinic anhydride-cystamine-valine (PTX-SS-Val) were designed, synthesized and evaluated against cancer cell lines. Compared with paclitaxel, these prodrugs contained water-soluble groups such as amino, carboxyl and amino acid, which improved the aqueous solubility of the prodrugs. More importantly, the valine was introduced in PTX-SS-Val molecule and made the molecule conform to the structural characteristics of intestinal oligopeptide transporter PEPT1 substrate. Thus the oral bioavailability of prodrug could be improved because of the mediation of PEPT1 transporter. These small molecule paclitaxel prodrugs could self-assemble into nanoparticles in aqueous solution, which effectively improved the solubility of paclitaxel, and had certain stability in pH 6.5, pH 7.4 buffer solutions and simulated gastrointestinal fluids. Some of these prodrugs, especially for PTX-Cys and PTX-SS-Val, exhibited nearly equal or slightly better anticancer activity when compared to paclitaxel. Further studies on PTX-Cys and PTX-SS-Val showed that both had good intestinal absorption in the rat single-pass intestinal perfusion (SPIP) experiments. Oral pharmacokinetic experiments showed that PTX-SS-Val could effectively improve the oral bioavailability of PTX.

Hyperthermal paclitaxel-bound albumin nanoparticles co-loaded with indocyanine green and hyaluronidase for treating pancreatic cancers.

Albumin nanoparticles have become an attractive cancer nanomedicine platform due to their pharmaceutical advantages. Recently, photothermal therapy has been extensively applied to cancer treatment due to heat-induced tumor ablation. Herein, we fabricated albumin nanoparticles (HSA-NPs) loaded with paclitaxel (PTX), indocyanine green (ICG; a hyperthermal agent) and hyaluronidase (HAase) that breaks down hyaluronan, a major component of the extracellular matrix (ECM) in tumors. Synthesis was based on a slightly modified nanoparticle albumin-bound (Nab™) technique. The prepared nanoparticles (PTX/ICG/HAase-HSA-NPs) had a spherical shape with an average size of ~ 110 nm and a zeta potential of ~ -30.4 mV. They displayed good colloidal stability and typical patterns of ICG, HSA and HAase in UV-VIS-NIR and circular dichroism spectroscopic analysis. PTX/ICG/HAase-HSA-NPs were found to have excellent hyperthermal effects in response to near-infrared laser irradiation (808 nm) (up to > 50 °C over 4 min). The hyperthermia conducted by PTX/ICG/HAase-HSA-NPs resulted in significant cytotoxicity to pancreatic AsPC-1 cells at both severe (> 50 °C) and mild (41-42 °C) hyperthermal states in conjunction with the inherent cytotoxic activity of paclitaxel. Furthermore, the confocal images of AsPC-1 cell spheroids proved PTX/ICG/HAase-HSA-NPs were able to permeate deeply into the three-dimensional tumor tissue mimicry structure. Most of all, PTX/ICG/HAase-HSA-NPs maintained all these physicochemical and anti-cancer properties irrespective of the amount of embedded HAase (1-5 mg). Our results demonstrated that PTX/ICG/HAase-HSA-NPs are a promising hyperthermal/chemotherapeutic anticancer agent.