Which polymer is more suitable for etoposide: A comparison between two kinds of drug loaded polymeric micelles in vitro and in vivo?

Preparation of etoposide liposomes for enhancing antitumor efficacy on small cell lung cancer and reducing hematotoxicity of drugs

Etoposide (VP16) is commonly used in the treatment of small cell lung cancer (SCLC) in clinical practice. However, severe adverse reactions such as bone marrow suppression toxicity limit its clinical application. Although several studies on VP16 liposomes were reported, no significant improvement in bone marrow suppression toxicity has been found, and there was a lack of validation of animal models for in vivo antitumor effects. Therefore, we attempted to develop a PEGylated liposomal formulation that effectively encapsulated VP16 (VP16-LPs) and evaluated its therapeutic effect and toxicity at the cellular level and in animal models. First, we optimized the preparation process of VP16-LPs using an orthogonal experimental design and further prepared them into freeze-dried powder to improve storage stability of the product. Results showed that VP16-LPs freeze-dried powder exhibited good dispersibility and stability after redispersion. In addition, compared to marketed VP16 injection, VP16-LPs exhibited sustained drug release characteristics. At the cellular level, VP16-LPs enhanced the cellular uptake of drugs and exhibited strong cytotoxic activity. In animal models, VP16-LPs could target and aggregate in tumors and exhibit a higher anti-tumor effect than VP16-injection after intravenous injection. Most importantly, hematological analysis results showed that VP16-LPs significantly alleviated the bone marrow suppression toxicity of drug. In summary, our study confirmed that PEGylated liposomes could enhance therapeutic efficacy and reduce toxicity of VP16, which demonstrated that VP16-LPs had enormous clinical application potential.

A liposomal etoposide with a sustained drug release effectively alleviated the therapy-related leukemia

Etoposide (VP16) can induce therapy-related leukemia, which is reported to occur less frequently with a prolonged dose schedule. Therefore, we hypothesized that nanocarriers could decrease the VP16-induced leukemogenesis by reducing the rate of VP16 exposure via a sustained drug release. To test our hypothesis, the VP16-loaded liposome with a slow drug release behavior was constructed by encapsulating a rapidly-cleaved VP16-maleimide conjugate into liposomes using a glutathione-gradient loading method, and its toxicities and in vivo antitumor efficacy were compared with free VP16 in the LLC lung cancer xenograft. It was found that the repeated injection of free VP16 induced severe splenomegaly, lymphocytosis, and extensive lymphocyte infiltration in various tissues, indicating a sign of VP16 therapy-related leukemia. By contrast, the liposomal VP16 not only remarkably alleviated the syndrome of leukemogenesis, but also exhibited significantly enhanced antitumor activity as compared with free VP16 at the same dose. These results highlighted that the liposomal VP16 having a sustained drug release could effectively decrease the toxicity of leukemogenesis, which provided a new warranty to develop liposomal VP16 as a safe alternative to the commercial VP16 injection.

Development of a hybrid nanocarrier-recognizing tumor vasculature and penetrating the BBB for glioblastoma multi-targeting therapy

The success of glioma chemotherapy is hampered by poor drug penetration ability across the blood-brain barrier (BBB) and low intratumoral drug concentration. Novel tumor-targeted delivery systems are useful in specifically accumulating in the tumor foci and penetrating into the glioma core after entering into the brain. Here we show that a multi-targeting hybrid nanocarrier (Pep-MLHA HNPs) system based on hyaluronic acid (HA)-modified polymer and a functional peptide possesses multi-target capability and stronger penetration ability into the core of three-dimensional tumor spheroids, could migrate efficiently across the BBB in vitro. The intensity of the Pep-MLHA HNPs after transporting across the BBB was 5.2-fold and 5.6-fold higher than that of ML NPs in C6 and U87 cells, respectively. More interestingly, this multi-targeting hybrid system displayed high colloidal stability in PBS solution, and weak negative zeta potential (-1.99 ± 0.655 mV) minimizing nonspecific interactions with plasma proteins and promoting long-term circulation in vivo. Additionally, the multi-targeting hybrid system induced enhanced tumor localization in U87 in situ-bearing nude mice and xenograft-bearing nude mice after systemic administration. Furthermore, docetaxel (DTX)-loaded Pep-MLHA HNPs showed negligible systemic toxicity and enhanced therapeutic efficacy, with significantly improved survival rates in intracranial C6 glioma-bearing rats. The 50% survival rate of DTX/Pep-MLHA HNPs-treated rats (40 days) was significantly longer than that of rats treated with NS (22 days), Taxotere® (25 days), DTX/ML NPs (25 days), DTX/Pep NPs (32 days) and DTX/MLHA NPs (29 days). All the results suggested that the multi-targeting hybrid nanocarrier system is promising for glioma treatment.

Topoisomerase inhibitors: Pharmacology and emerging nanoscale delivery systems

Topoisomerase enzymes have shown unique roles in replication and transcription. These enzymes which were initially found in Escherichia coli have attracted considerable attention as target molecules for cancer therapy. Nowadays, there are several topoisomerase inhibitors in the market to treat or at least control the progression of cancer. However, significant toxicity, low solubility and poor pharmacokinetic properties have limited their wide application and these characteristics need to be improved. Nano-delivery systems have provided an opportunity to modify the intrinsic properties of molecules and also to transfer the toxic agent to the target tissues. These delivery systems leads to the re-introduction of existing molecules present in the market as novel therapeutic agents with different physicochemical and pharmacokinetic properties. This review focusses on a variety of nano-delivery vehicles used for the improvement of pharmacological properties of topoisomerase inhibitors and thus enabling their potential application as novel drugs in the market.

Amphiphilic diblock copolymer of hydrophilic-functionalized lactone and lactide via switchable organocatalytic polymerization

Main-chain degradable amphiphilic diblock copolymers prepared by one-pot ring-opening polymerization via actively manipulating catalytic states of an acid–base catalytic system were capable of forming stable micelle with optimal particle size.

Characterization and antitumor efficacy of poly(L-lactid acid)-based etoposide-loaded implants

Etoposide is widely used in the chemotherapy of a variety of malignancies. But the strong lipophilicity, poor bioavailability, and severe side effects of etoposide limit its clinical application. The aim of this study was to develop sustained-release etoposide-loaded implants and evaluate antitumor activity of the implants after intratumoral implantation. We prepared the implants containing etoposide, poly(L-lactid acid) and polyethylene glycol 4000 by the direct compression method. The implants were characterized regarding drug-excipient compatibility, content uniformity, morphology, sterility, in vitro, and in vivo release profiles. Then the antitumor activity of the implants was tested in xenograft model of A549 human non-small cell lung cancer. SEM images displayed smooth surface of the implant and indicated that etoposide was homogeneously dispersed in the polymeric matrix. The results of content uniformity met the requirements of the Chinese Pharmacopoeia. Both in vitro and in vivo release profiles of the implants were characterized by high burst release followed by sustained release of etoposide. Intratumoral implantation of etoposide-loaded implants could efficiently delay the tumor growth. Furthermore, increasing the dose of implants led to higher tumor suppression rate without adding systemic toxicity. These results indicated that etoposide-loaded implants have significant antitumor efficacy in xenograft model without dose-limiting side effects and they possess a strong potential to be used as an intratumoral chemotherapy option for lung cancer treatment.

A Novel MPEG-PDLLA-PLL Copolymer for Docetaxel Delivery in Breast Cancer Therapy

Satisfactory drug loading capacity and stability are the two main factors that determine the anti-cancer performance. In general, the stability of the micelles is reduced when the drug loading (DL) is increased. Therefore, it was a challenge to have high drug loading capacity and good stability. In this study, we introduced a hydrophilic poly (L-Lysine) (PLL) segment with different molecular-weights into the monomethoxy poly (ethylene glycol)-poly (D, L-lactide) (MPEG-PDLLA) block copolymer to obtain a series of novel triblock MPEG-PDLLA-PLL copolymers. We found that the micelles formed by a specific MPEG2k-PDLLA4k-PLL1k copolymer could encapsulate docetaxel (DTX) with a satisfactory loading capacity of up to 20% (w/w) via the thin film hydration method, while the stability of drug loaded micellar formulation was still as good as that of micelles formed by MPEG2k-PDLLA1.7k with drug loading of 5% (w/w). The results from computer simulation study showed that compared with MPEG2k-PDLLA1.7k, the molecular chain of MPEG2k-PDLLA4k-PLL1k could form a more compact funnel-shaped structure when interacted with DTX. This structure favored keeping DTX encapsulated in the copolymer molecules, which improved the DL and stability of the nano-formulations. The in vitro and in vivo evaluation showed that the DTX loaded MPEG2k-PDLLA4k-PLL1k (DTX/MPEG2k-PDLLA4k-PLL1k) micelles exhibited more efficiency in tumor cell growth inhibition. In conclusion, the MPEG2k-PDLLA4k-PLL1k micelles were much more suitable than MPEG2k-PDLLA1.7k for DTX delivery, and then the novel nano-formulations showed better anti-tumor efficacy in breast cancer therapy.

Synthesis, characterization and drug loading property of Monomethoxy-Poly(ethylene glycol)-Poly(ε-caprolactone)-Poly(D,L-lactide) (MPEG-PCLA) copolymers

Amphiphilic block copolymers have attracted a great deal of attention in drug delivery systems. In this work, a series of monomethoxy-poly (ethylene glycol)-poly (ε-caprolactone-co-D,L-lactide) (MPEG-PCLA) copolymers with variable composition of poly (ε-caprolactone) (PCL) and poly (D,L-lactide) (PDLLA) were prepared via ring-opening copolymerization of ε-CL and D,L-LA in the presence of MPEG and stannous octoate. The structure and molecular weight were characterized by nuclear magnetic resonance (NMR) and gel permeation chromatography (GPC). The crystallinity, hydrophilicity, thermal stability and hydrolytic degradation behavior were investigated in detail, respectively. The results showed that the prepared amphiphilic MPEG-PCLA copolymers have adjustable properties by altering the composition of PCLA, which make it convenient for clinical applications. Besides, the drug loading properties were also studied. Docetaxel (DTX) could be entrapped in MPEG-PCLA micelles with high loading capacity and encapsulation efficiency. And all lyophilized DTX-loaded MPEG-PCLA micelles except MPEG-PCL micelles were readily re-dissolved in normal saline at 25 °C. In addition, DTX-loaded MPEG-PCLA micelles showed a slightly enhanced antitumor activity compared with free DTX. Furthermore, DTX micelles exhibited a slower and sustained release behavior in vitro, and higher DTX concentration and longer retention time in vivo. The results suggested that the MPEG-PCLA copolymer with the adjustable ratio of PCL to PDLLA may be a promising drug delivery carrier for DTX.

Effective tumor-targeted delivery of etoposide using chitosan nanoparticles conjugated with folic acid and sulfobetaine methacrylate

FA–CS(VP-16)-g-PSBMA nanoparticles were synthesized and showed effective tumor-targeting properties and promising anti-tumor capacity in vivo.

Well-defined labile diselenide-centered poly(ε-caprolactone)-based micelles for activated intracellular drug release

Diselenide groups were introduced into aliphatic polyesters to develop a novel well-defined reduction-labile biodegradable diselenide-containing polymeric drug delivery system (mPEG–PCL–Se)₂.

The evaluation of cellular uptake efficiency and tumor-targeting ability of MPEG–PDLLA micelles: effect of particle size

The study reported herein describes the cellular uptake efficiency and tumor-targeting ability of MPEG–PDLLA micelles with two different particle sizes.