Sushilkumar Patil

PEG — A versatile conjugating ligand for drugs and drug delivery systems

Polyethylene glycol (PEG) conjugation is a rapidly evolving strategy to solve hurdles in therapeutic delivery and is being used as an add-on tool to the traditional drug delivery methods. Chemically, PEGylation is a term used to denote modification of therapeutic molecules by conjugation with PEG. Efforts are constantly being made to develop novel strategies for conjugation of PEG with these molecules in order to increase its current applications. These strategies are specific to the therapeutic system used and also depend on the availability of activated PEGylating agents. Therefore, a prior knowledge is essential in selecting appropriate method for PEGylation. Once achieved, a successful PEGylation can amend the pharmacokinetic and pharmacodynamic outcomes of therapeutics. Specifically, the primary interest is in their ability to decrease uptake by reticuloendothelial system, prolong blood residence, decrease degradation by metabolic enzymes and reduce protein immunogenicity. The extensive research in this field has resulted into many clinical studies. The knowledge of outcome of these studies gave a good feedback and lessons which helped researchers to redesign PEG conjugates with improved features which can increase the chance of hitting the market. In light of this, the current paper highlights the approaches, novel strategies and the utilization of modern concept for PEG conjugation with respect to various bioactive components of clinical relevance. Moreover, this review also discusses potential clinical outcomes of the PEG conjugation, regulatory approved PEGylated product, clinical trials for newer formulations, and also provides future prospects of this technology.

Epidermal growth factor receptor targeting in cancer: A review of trends and strategies

The epidermal growth factor receptor (EGFR) is a cell-surface receptor belonging to ErbB family of tyrosine kinase and it plays a vital role in the regulation of cell proliferation, survival and differentiation. However; EGFR is aberrantly activated by various mechanisms like receptor overexpression, mutation, ligand-dependent receptor dimerization, ligand-independent activation and is associated with development of variety of tumors. Therefore, specific EGFR inhibition is one of the key targets for cancer therapy. Two major approaches have been developed and demonstrated benefits in clinical trials for targeting EGFR; monoclonal antibodies (mAbs) and tyrosine kinase inhibitors (TKIs). EGFR inhibitors like, cetuximab, panitumumab, etc. (mAbs) and gefitinib, erlotinib, lapatinib, etc. (TKIs) are now commercially available for treatment of variety of cancers. Recently, many other agents like peptides, nanobodies, affibodies and antisense oligonucleotide have also shown better efficacy in targeting and inhibiting EGFR. Now a days, efforts are being focused to identify molecular markers that can predict patients more likely to respond to anti-EGFR therapy; to find out combinatorial approaches with EGFR inhibitors and to bring new therapeutic agents with clinical efficacy. In this review we have outlined the role of EGFR in cancer, different types of EGFR inhibitors, preclinical and clinical status of EGFR inhibitors as well as summarized the recent efforts made in the field of molecular EGFR targeting.

Protein– and Peptide–Drug Conjugates: An Emerging Drug Delivery Technology

Protein- and peptide-drug conjugates hold a promising stance in the delivery of therapeutic agents by providing distinct advantage of improving therapeutic potential of drugs. Recent advancements in the proteomics and recombinant DNA technology, by enabling identification of distinct structural features of proteins and making it feasible to introduce specific functionalities in protein/peptide structure, has made it possible to synthesize high quality protein- and peptide-drug conjugates though a wide variety of coupling techniques. Additionally, use of specialized linkers makes them unique in their in vivo therapeutic application by providing target tissue-specific release of drug. Several protein- and peptide-drug conjugates are currently under clinical trials warranting their huge market potential in near future. Increased understanding in this field will surely enable us to produce high quality protein- and peptide-drug conjugates which will serve therapeutic needs demanded from drug delivery systems in clinical settings.

Protein– and Peptide–Drug Conjugates

Protein- and peptide-drug conjugates hold a promising stance in the delivery of therapeutic agents by providing distinct advantage of improving therapeutic potential of drugs. Recent advancements in the proteomics and recombinant DNA technology, by enabling identification of distinct structural features of proteins and making it feasible to introduce specific functionalities in protein/peptide structure, has made it possible to synthesize high quality protein- and peptide-drug conjugates though a wide variety of coupling techniques. Additionally, use of specialized linkers makes them unique in their in vivo therapeutic application by providing target tissue-specific release of drug. Several protein- and peptide-drug conjugates are currently under clinical trials warranting their huge market potential in near future. Increased understanding in this field will surely enable us to produce high quality protein- and peptide-drug conjugates which will serve therapeutic needs demanded from drug delivery systems in clinical settings.

Polymer assisted entrapment of netilmicin in PLGA nanoparticles for sustained antibacterial activity

Abstract This study was aimed to develop poly(dl-lactide-co-glycolide) (PLGA) nanoparticle of highly water soluble antibiotic drug, netilmicin sulfate (NS) with improved entrapment efficiency (EE) and antibacterial activity. Dextran sulfate was introduced as helper polymer to form electrostatic complex with NS. Nanoparticles were prepared by double emulsification method and optimized using 25-1 fractional factorial design. EE was mainly influenced by dextran sulfate: NS charge ratio and PLGA concentration, whereas particle size (PS) was affected by all factors examined. The optimized NS-loaded-NPs had EE and PS of 93.23 ± 2.7% and 140.83 ± 2.4 nm respectively. NS-loaded-NPs effectively inhibited bacterial growth compared to free NS. Sustained release protected its inactivation and reduced the decline in its killing activity over time even in presence of bronchial cells. A MIC value of 18 μg/mL was observed for NPs on P. aeruginosa. Therefore, NPs with sustained bactericidal efficiency against P. aeruginosa may provide therapeutic benefit in chronic pulmonary infection, like cystic fibrosis.

Receptor-targeted drug delivery: current perspective and challenges

Receptor-targeted drug delivery has been extensively explored for active targeting. However, the scarce clinical applications of such delivery systems highlight the implicit hurdles in development of such systems. These hurdles begin with lack of knowledge of differential expression of receptors, their accessibility and identification of newer receptors. Similarly, ligand-specific challenges range from proper choice of ligand and conjugation chemistry, to release of drug/delivery system from ligand. Finally, nanocarrier systems, which offer improved loading, biocompatibility and reduced premature degradation, also face multiple challenges. This review focuses on understanding these challenges, and means to overcome such challenges to develop efficient, targeted drug-delivery systems.

Role of Nanotechnology in Delivery of Protein and Peptide Drugs.

The advent of recombinant DNA technology and computational designing has fueled the emergence of proteins and peptides as a new class of modern therapeutics such as vaccines, antigens, antibodies and hormones. Demand for such therapeutics has increased recently due to their distinct pharmacodynamic characteristics of specificity of action and high potency. However, their potential clinical applications are often hindered by involvement of factors which impact their therapeutic potential negatively. Large size, low permeability, conformational fragility, immunogenicity, metabolic degradation and short half-life results in poor bioavailability and inferior efficacy. These challenges have encouraged researchers to devise strategies for effective delivery of proteins and peptides. Recent advances made in nanotechnology are being sought to overcome aforesaid problems and to offer advantages such as higher drug loading, improved stability, sustained release, amenability for non-parenteral administration and targeting through surface modifications. This review focuses on elaborating the role of nanotechnology based formulations and associated challenges in protein and peptide delivery, their clinical outlook and future perspective.

Protein-Functionalized PLGA Nanoparticles of Lamotrigine for Neuropathic Pain Management

Lamotrigine (LTG), a sodium and calcium channel blocker, has demonstrated efficacy for the treatment of neuropathic pain in multiple, randomized, controlled trials. However, its potential clinical applications in neuropathic pain are limited due to the risk of dose-dependent severe rashes associated with high dose and prompt dose escalation. Further, the poor pharmacokinetic profile due to non-selective distribution to organs other than brain reduces the efficacy of dosage regimen. Therefore, the aim of present investigation is to develop surface-engineered LTG nanoparticles (NPs) using transferrin and lactoferrin as ligand to deliver higher amount of drug to brain and improve the biodistribution and pharmacokinetic profile of drug with prolonged duration of action and reduced accumulation in non-target organs. The LTG NPs were prepared by nanoprecipitation and optimized by factorial design for high entrapment and optimized particle size. The optimized NPs were surface functionalized by conjugating with the lactoferrin (Lf) and transferrin (Tf) as ligands. The developed NPs were characterized for different physicochemical parameters and stability. The in vivo biodistribution showed preferential targeting to brain and reduced accumulation in non-target organs over a prolonged duration of time. Finally, partial sciatic nerve injury model was used to demonstrate the increased pharmacodynamic response as antinociceptive effect. Both biodistribution and pharmacodynamic study in mice confirmed that the approach used for LTG can help to increase clinical applications of LTG due to brain targeting and reduced side effects.

Liposomes encapsulating native and cyclodextrin enclosed paclitaxel: Enhanced loading efficiency and its pharmacokinetic evaluation

Combination strategy involving cyclodextrin (CD) complexation and liposomal system was investigated for Paclitaxel (PTX) to improve loading. Complexation was done using 2,6-di-O-methylbetacyclodextrin (DMβCD). Sterically stabilized double loaded PEGylated liposomes (DLPLs) containing PTX and PTX-DMβCD complex were prepared by thin film hydration. Physicochemical characterization of complex and prepared DLPLs was carried out. Cytotoxic potential, hemolytic potential and pharmacokinetics of DLPLs were tested in comparison to Taxol®. Aqueous solubility of PTX increased by almost 3 × 104 folds due to complexation with DMβCD as compared to pure drug solubility. Liposomal system was found to have 162.8 ± 4.1 nm size, zeta potential of -5.6 ± 0.14 mV and 2-fold increase in drug loading to 5.8 mol % for PTX due to double loading. DLPLs had low hemolytic potential and higher cytotoxicity on SKOV3 cells with improvement in IC50 value by 4.2 folds as compared to Taxol® at 48 h. The anti-angiogenic potential of DLPLs was confirmed by 1.33 folds lesser wound recovery in SKOV3 cells compared to Taxol®. In-vivo pharmacokinetic evaluation of DLPLs in rats substantiates improvement in circulation time, higher plasma concentration and decreased clearance rate compared to Taxol®. An efficacious system with improved loading and pharmacokinetics was formulated as potential alternative for currently marketed PTX formulation.

PEGylated composite nanoparticles of PLGA and polyethylenimine for safe and efficient delivery of pDNA to lungs

Achieving stable, efficient and non-toxic pulmonary gene delivery is most challenging requirement for successful gene therapy to lung. Composite nanoparticles (NPs) of the poly(lactic-co-glycolic acid) (PLGA) and cationic polymer polyethyleneimine (PEI) is an efficient alternative to viral and liposomal vectors for the pulmonary delivery of pDNA. NPs with different weight ratios (0-12.5%w/w) of PLGA/PEI were prepared and characterized for size, morphology, surface charge, pDNA loading and in vitro release. The in vitro cell uptake and transfection studies in the CFBE41o-cell line revealed that NPs with 10% w/w PEI were more efficient but they exhibited significant cytotoxicity in MTT assays, challenging the safety of this formulation. Surface modifications of these composite NPs through PEGylation reduced toxicity and enhanced cellular uptake and pDNA expression. PEGylation improved diffusion of NPs through the mucus barrier and prevented uptake by pulmonary macrophages. Finally, PEGylated composite NPs were converted to DPI by lyophilization and combined with lactose carrier particles, which resulted in improved aerosolization properties and lung deposition, without affecting pDNA bioactivity. This study demonstrates that a multidisciplinary approach may enable the local delivery of pDNA to lung tissue for effective treatment of deadly lung diseases.