Vaibhav Khare

Paclitaxel formulations: challenges and novel delivery options.

Paclitaxel (PTX), a taxane plant product, is one of the most effective broad-spectrum anti-cancer agents and approved for the treatment of a variety of cancers including ovarian, breast, lung, head and neck as well as Kaposis sarcoma. Poor aqueous solubility and serious side effects associated with commercial preparation of PTX (Taxol®) triggered the development of alternative PTX formulations. Over past three decades, plethora of research work has been published towards the development of cremophor free and efficient formulations. Various nanocarrier systems including nanoparticles, liposomes, micelles, bioconjugates and dendrimers have been employed in order to improve PTX solubility and eliminate undesired side effects. These nanocarriers offer the advantage of high degree of encapsulation and cellular uptake, escape from elimination by P-glycoprotein (P-gp) mediated efflux, and can be explored for targeted drug delivery. The potential of these nanocarriers is reflected by the fact that various nanocarriers of PTX are in different stages of clinical trials and a few have already been commercialized including Abraxane®, Lipusu and Genexol PM®. This review focuses on the various challenges associated with PTX formulation development, limitations of existing formulations and novel approaches for the development of alternative formulations for PTX and also highlights the development of novel formulations in clinical settings.

Advances in P-glycoprotein-based approaches for delivering anticancer drugs: pharmacokinetic perspective and clinical relevance

Introduction: P-glycoprotein (P-gp) is a multi-specific efflux transporter belonging to ATP-binding cassette (ABC) transporter family, encoded by the ABCB1 gene, which significantly impacts the pharmacokinetics as well as multidrug resistance of anticancer drugs. Areas covered: This review explores how human P-gp transporters modulate the pharmacokinetics of anticancer drugs and emerging strategies to modulate their function. The key findings in direct modulation by various P-gp inhibitors on pharmacokinetics of various anticancer P-gp substrates are described. The role of pharmaceutical excipients as P-gp inhibitor with the focus on the recent development in novel drug delivery systems to modulate pharmacokinetics of anticancer drugs is also outlined. Expert opinion: The concomitant use of anticancer P-gp substrate and P-gp inhibitor is an effective and safe way to enhance the bioavailability of anticancer drugs. The poor bioavailability and toxicity of anticancer drugs limit their therapeutic efficacy. These characteristics can be improved by using various nanocarriers which exhibited a high potential to bypass this efflux protein. The best combination of P-gp inhibitor and substrate anticancer drug in a single nanocarrier formulation is a future challenge and is still probably some years away from the marketplace.

Development and evaluation of folate functionalized albumin nanoparticles for targeted delivery of gemcitabine

Gemcitabine is one of the most potent anticancer agents acting on a wide range of solid tumors, however, its use is limited by short half life and high dose leading to serious side effects. The present investigation describes the development and characterization of folate functionalized gemcitabine loaded bovine serum albumin nanoparticles (Fa-Gem-BSANPs). The nanoparticles were prepared by desolvation cross-linking technique and characterized for various parameters including morphology, particle size, zeta potential, drug loading and release profile. The particle size of Gem-BSANPs and Fa-Gem-BSANPs was found to be 159.1±5.29 and 208.7±1.80 nm, respectively. DSC and XRD analysis indicated amorphous nature of the drug within the particles. The encapsulated gemcitabine exhibited less hemolytic properties as compared to native drug. The anticancer activity of Fa-Gem-BSANPs was evaluated in folate receptor over expressing cell lines (Ovcar-5 and MCF-7) and folate receptor deficient cell line (MIAPaCa-2). The Fa-Gem-BSANPs showed superior anticancer activity as compared to Gem-BSANPs in Ovcar-5 and MCF-7 cells while no significant difference in cytotoxicity was found with MIAPaCa-2 cells. Confocal microscopy indicated facilitated intracellular uptake of Fa-Gem-BSANPs in MCF-7, which in turn result in a higher potential for apoptosis. Further, Fa-Gem-BSANPs exhibited improved anti-tumor activity in Ehrlich solid tumor model in mice. In conclusion, our study indicates that folate functionalized nanoparticles confer enhance cellular uptake and cytotoxicity for gemcitabine.

Synthesis, characterization and mechanistic-insight into the anti-proliferative potential of PLGA-gemcitabine conjugate.

Gemcitabine, a nucleoside analogue, is used in the treatment of various solid tumors, however, its efficacy is limited by rapid metabolism by cytidine deaminase and fast kidney excretion. In this study, a polymeric conjugate of gemcitabine was prepared by covalent coupling with poly(lactic-co-glycolic) acid (PLGA), in order to improve anticancer efficacy of the drug. The prepared conjugate was characterized by various analytical techniques including FTIR, NMR and mass spectroscopic analysis. The stability study indicated that the polymeric conjugate was more stable in plasma as compared to native gemcitabine. Further, in vitro cytotoxicity determined in a panel of cell lines including pancreatic cancer (MIAPaCa-2), breast cancer (MCF-7) and colon cancer (HCT-116), indicated that the cytotoxic activity of gemcitabine was retained following conjugation with polymeric carrier. In the nucleoside transportation inhibition assay, it was found that the prepared conjugate was not dependent on nucleoside transporter for entering into the cells and this, in turn, reflecting potential implication of this conjugate in the therapy of transporter- deficient resistance cancer. Further, the cell cycle analysis showed that the sub-G1 (G0) apoptotic population was 46.6% and 60.6% for gemcitabine and PLGA gemcitabine conjugate, respectively. The conjugate produced remarkable decrease in mitochondrial membrane potential, a marker of apoptosis. In addition, there was a marked increase in PARP cleavage and P-H2AX expression with PLGA gemcitabine conjugate as compared to native gemcitabine indicating improved apoptotic activity. The findings demonstrated the potential of PLGA gemcitabine conjugate to improve clinical outcome of gemcitabine based chemotherapy of cancer.

Biodegradable polymeric system for cisplatin delivery: Development, in vitro characterization and investigation of toxicity profile ☆ ☆☆

Cisplatin is one of the most potent anticancer agent used in the treatment of various solid tumors, however, its clinical use is limited due to severe adverse effects including nephrotoxicity. In this investigation cisplatin loaded poly (lactic-co-glycolic acid) (PLGA) nanoparticles were developed and characterized for various in vitro characteristics including size distribution, zeta potential, drug loading and release profile. PLGA nanoparticles were successfully developed as investigated using scanning electron microscopy and exhibited average particles size and zeta potential as 284.8 nm and -15.8 mV, respectively. Fourier transform infrared spectroscopy and differential scanning calorimetry indicated an absence of any polymer-drug interactions. Cisplatin nanoparticles exhibited in vitro anticancer activity against A549 cells comparable to that of cisplatin solution. The biodistribution study in mice indicated that the kidney cisplatin level was significantly (p<0.01) lower with cisplatin nanoparticles than cisplatin solution. Following two cycles of cisplatin treatment, a week apart, blood urea nitrogen level was found to be higher in case of cisplatin solution as compared to cisplatin nanoparticles. Further, there was a significant (p<0.01) increase in plasma creatinine level in case of cisplatin solution as compared to cisplatin nanoparticles. Histopathological examination of kidney from cisplatin nanoparticles treated group revealed no kidney damage, however, a sign of nephrotoxicity was observed in the case of cisplatin solution. The results suggest that PLGA nanoparticle based formulation could be a potential option for cisplatin delivery.

Co-formulation of P-glycoprotein Substrate and Inhibitor in Nanocarriers: An Emerging Strategy for Cancer Chemotherapy

Scientific community is striving to understand the role of P-glycoprotein (P-gp) in drug discovery programs due to its impact on pharmacokinetic and multi-drug resistance (MDR) of anticancer drugs. A number of efforts to resolve the crystal structure and understanding the mechanism of P-gp mediated efflux have been made. Several generations of Pgp inhibitors have been developed to tackle this multi-specific efflux protein. Unfortunately, these inhibitors lack selectivity, exhibit poor solubility and severe pharmacokinetic interactions restricting their clinical use. The nanocarrier drug delivery systems (NDDS) are receiving increasing attention for P-gp modulating activity of pharmaceutical excipients which are used in their fabrication. In addition, NDDS can enhance the solubility and exhibited ability to bypass P-gp mediated efflux. The co-formulation of P-gp inhibitors and substrate anticancer drugs in single drug delivery system offers the advantage of bypassing P-gp mediated drug efflux as well as inhibiting the P-gp. Moreover, severe pharmacokinetic interactions between P-gp inhibitor and substrate anticancer drugs could be avoided by using this strategy. In this article we describe the co-formulation strategies using nanocarriers for modulation of pharmacokinetics as well as multi-drug resistance of anticancer drugs along with the challenges in this area.

Development and evaluation of paclitaxel loaded PLGA:poloxamer blend nanoparticles for cancer chemotherapy.

This investigation described the development of novel PLGA:poloxamer blend nanoparticles for intravenous administration of paclitaxel in order to limit the cremophor-associated adverse effects. The developed formulation was well-characterized using various techniques including scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy and differential scanning calorimetry. The nanoparticles had an average particle size around 180nm and zeta potential of -22.7mV. The in vitro release study of nanoparticles exhibited biphasic release pattern. The non-hemolytic potential of the nanoparticles indicated the suitability of the developed formulation for intravenous administration. The PLGA:poloxamer blend nanoparticles showed significantly improved cytotoxicity in cell lines (MCF-7 and Colo-205), as compared to free drug. Further, the developed formulation was stable under the accelerated storage conditions. In conclusion, the results indicated that the developed polymeric formulation is a novel and potential alternative for the paclitaxel delivery.

Synthesis and characterization of TPGS–gemcitabine prodrug micelles for pancreatic cancer therapy

The therapeutic potential of a nucleoside analog, gemcitabine, is severely compromised due to its rapid clearance from systemic circulation by enzymatic degradation into an inactive metabolite. In the present investigation, micelles based on polymer–drug conjugate were developed for gemcitabine and investigated for their potential to improve cancer chemotherapy. The tocopherol poly(ethylene glycol) succinate 1000 (TPGS)–gemcitabine prodrug was synthesized via an amide linkage and characterised by analytical methods, including FT-IR, 1H NMR, and MALDI-TOF. The micellar formulation of TPGS–gemcitabine prodrug was developed by a self-assembly technique and evaluated for various physicochemical parameters including particle size, polydispersity, morphology, critical micelle concentration and release profile. It was observed that gemcitabine present in TPGS–gemcitabine micelles was resistant to deamination by crude cytidine deaminase. The improved cytotoxicity of the micellar formulation was observed using TPGS–gemcitabine micelles against pancreatic cancer cells. Further, it was found that, unlike native gemcitabine, nucleoside transporters were not required for TPGS–Gem micelles to demonstrate their anticancer potential. These findings revealed that TPGS–gemcitabine micelles may serve as a promising platform for gemcitabine in order to improve its anticancer efficacy.

Improved efficacy of cisplatin in combination with a nano-formulation of pentacyclic triterpenediol

Cisplatin is widely used for the treatment of various cancers including cervical, ovarian, lung and head and neck, however, its clinical success is limited owing to the dose-dependent adverse effects, mainly nephrotoxicity and neurotoxicity. In order to address this limitation, the present study was undertaken to investigate growth inhibitory effect of cisplatin in combination with a triterpenediol (3a, 24-dihydroxyurs-12-ene and 3a, 24-dihydroxyolean-12-ene, TPD) on human ovarian cancer cell line. Poly(dl-lactic-co-glycolic) acid nanoparticles loaded with TPD (TPD-PLGA-NPs) were successfully developed by emulsion solvent evaporation method. The TPD-PLGA-NPs were characterized for size distribution and zeta potential which was in order of 152.56±3.01nm and -17.36±0.37mV respectively. The morphological evaluation was carried out by transmission electron microscopy and the formulation was also characterized using Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). The drug loading of the optimized formulation was 51.03±1.52μg/mg and the formulation exhibited sustained drug release profile. The in vitro cellular uptake study of coumarin-6 loaded PLGA nanoparticles in OVCAR-5 cells demonstrated a time dependent increase in uptake efficiency. Further, growth inhibitory effect of cisplatin was investigated in combination with TPD-PLGA-NPs. The combination index (CI) was <1, indicating a synergistic interaction. Further, at 75% of cell growth inhibition (ED75) the dose of cisplatin was reduced to 3.8 folds using this combination. The results indicated the potential of cisplatin and TPD-PLGA-NPs combination in order to reduce to dose limiting toxicities of the former.

Development and mechanistic insight into enhanced cytotoxic potential of hyaluronic acid conjugated nanoparticles in CD44 overexpressing cancer cells

&NA; The overexpression of CD44 in cancer cells reroutes number of oncogenic pathways including the central Pi3K/Akt/NF‐kB pathway leading to cancer progression and malignancy. Herein, we developed hyaluronic acid‐modified poly(DL‐lactic‐co‐glycolic acid)‐poly (ethylene glycol) nanoparticles (PLGA‐PEG‐HA NPs) for targeted delivery of TTQ (thio‐tetrazolyl analog of a clinical candidate, IC87114) to CD44 overexpressing cancer cells. The PLGA‐PEG co‐polymer was synthesized and characterized by NMR and FTIR. The co‐polymer based nanoparticles were prepared by solvent evaporation method and hyaluronic acid (HA) was conjugated on to the nanoparticle surface via EDC/NHS chemistry. The PLGA‐PEG–HA NPs had a desirable particle size (< 200 nm) with reduced polydispersibility and exhibited spherical shape under atomic force microscope (AFM). In vitro cytotoxicity and cellular uptake studies demonstrated higher cytotoxicity and enhanced intracellular accumulation of PLGA‐PEG‐HA NPs compared to PLGA‐PEG NPs in high CD44 expressing MiaPaca‐2 cells compared to MDA‐MB‐231 and MCF7 cells. At the molecular level, the PLGA‐PEG‐HA NPs were found to be inducing premature senescence with increase in senescence associated &bgr;‐galactosidase activity and senescence specific marker p21 expression through modulation of Pi3K/Akt/NF‐kB signaling pathway in MiaPaca‐2 cells. These findings collectively indicated that HA‐modified nanoparticles might serve as a promising nanocarrier for site‐specific drug delivery, and can be explored further to increase the therapeutic efficacy of anticancer drugs via targeting to CD44 over‐expressing cancer cells. Graphical abstract Figure. No caption available.