Chemical Conjugation Research Articles

A Bioorthogonal Click Chemistry Toolbox for Targeted Synthesis of Branched and Well-Defined Protein-Protein Conjugates.

Bioorthogonal chemistry holds great potential to generate difficult‐to‐access protein–protein conjugate architectures. Current applications are hampered by challenging protein expression systems, slow conjugation chemistry, use of undesirable catalysts, or often do not result in quantitative product formation. Here we present a highly efficient technology for protein functionalization with commonly used bioorthogonal motifs for Diels–Alder cycloaddition with inverse electron demand (DAinv). With the aim of precisely generating branched protein chimeras, we systematically assessed the reactivity, stability and side product formation of various bioorthogonal chemistries directly at the protein level. We demonstrate the efficiency and versatility of our conjugation platform using different functional proteins and the therapeutic antibody trastuzumab. This technology enables fast and routine access to tailored and hitherto inaccessible protein chimeras useful for a variety of scientific disciplines. We expect our work to substantially enhance antibody applications such as immunodetection and protein toxin‐based targeted cancer therapies.

Engineering Functional DNA-Protein Conjugates for Biosensing, Biomedical, and Nanoassembly Applications.

DNA and protein are the most important two classes of biomacromolecules forming the basis of life. The conjugation of the two using crosslinking chemistries enables a combination of molecular recognition, enzymatic catalysis, and Watson-Crick hybridization properties. The DNA-protein conjugate with combined properties enables a broad range of applications, such as sensitive and selective bioassays, therapeutic agents, and building blocks for programmable nanoassemblies. In this review, we survey the conjugates from the aspects of conjugation chemistries as well as applications in biomedical and nanotechnology fields. We highlight the functions of both biological moieties of a conjugate for target binding and signal transduction in bioassays. We also review the use of DNA-protein conjugates for the construction of a variety of functional and dynamic nanostructures, from isolated hybrid cages to three-dimensional (3D) protein crystalline lattices. Moreover, these conjugates have been used as carriers to deliver enzymes or functional nucleic acids for disease treatments and gene editing.

Detection of Human p53 In-Vitro Expressed in a Transcription-Translation Cell-Free System by a Novel Conjugate Based on Cadmium Sulphide Nanoparticles.

Here, cadmium sulphide quantum dots (CdS QDs) have been synthetized and functionalized with Bovine Serum Albumin (BSA) in a colloidal aqueous solution with a stability of over 3 months. Specific synthesis conditions, in homogeneous phase and at low temperature, have allowed limitation of S2− concentration, hence, as a consequence, there is restricted growth of the nanoparticles (NPs). This fact allows binding with BSA in the most favorable manner for the biomolecule. The presence of Cd2+ ions on the surface of the CdS nanoparticle is counteracted by the negatively charged domains of the BSA, resulting in the formation of small NPs, with little tendency for aggregation. Temperature and pH have great influence on the fluorescence characteristics of the synthetized nanoparticles. Working at low temperatures (4 °C) and pH 10–11 have proven the best result as shown by hydrolysis kinetic control of the thioacetamide precursor of S2− ion. Biological activity of the coupled BSA is maintained allowing subsequent bioconjugation with other biomolecules such as antibodies. The chemical conjugation with anti-Glutathione S-transferase (α-GST) antibody, a common tag employed in human recombinant fusion proteins, produces a strong quenching of fluorescence that proves the possibilities of its use in biological labelling. Finally, p53, onco-human recombinant protein (GST tagged in COOH terminus), has been in situ IVTT (in vitro transcription-translation) expressed and efficiently captured by the α-GST-CdS QD conjugate as a proof of the biocompatibility on IVTT systems and the functionality of conjugated antibody.

Engineering Selective Molecular Tethers to Enhance Suboptimal Drug Properties

Small-molecule drugs are utilized in a wide variety of clinical applications, however, many of these drugs suffer from one or more suboptimal property that can hinder its delivery or cellular action in vivo, or even shelf an otherwise biologically tolerable drug. While high-throughput screening provides a method to discover drugs with altered chemical properties, directly engineering small-molecule bioconjugates provides an opportunity to specifically modulate drug properties rather than sifting through large drug libraries with seemingly 'random' drug properties. Herein, we propose that selectively tethering a drug molecule to an additional group with favorable properties will improve the drug conjugate's overall properties, such as solubility. Specifically, we outlined the site-specific chemical conjugation of rapamycin (RAP) to an additional high-affinity group to increase the overall the drug has for cyclodextrin-based polymers (pCD). By doing so, we found that RAP's for pCD and RAP's window of delivery from pCD microparticles was tripled without sacrificing RAP's cellular action. This synthesis method was applied to the concept of affinity for pCD, but other prosthetic groups can be used similarly. This study displays potential for increasing drug delivery windows of small-molecule drugs in pCD systems for chronic drug therapies and introduces the idea of altering drug properties to tune polymer-drug interactions.

A site-specific approach to improved antibody-drug conjugates.

e13009 Background: Antibody based therapeutics have emerged as a highly promising treatment option for various forms of cancer. One such class of emergent antibody therapeutics is antibody-drug conjugates (ADCs), which has experienced remarkable success in the past few decades, including many candidates currently undergoing clinical trials. Despite its promise, developing effective ADCs remains a challenge due to extensive optimization with regard to antibody target identification, conjugate specificity, conjugation chemistry compatibility, heterogeneous side product co-purification, all affecting efficacy, PK/PD characteristics, and toxicity. There is a pressing need to develop alternative strategies for precise (site-specific), flexible (offering numerous options for conjugation site and chemistry), efficient, and scalable generation of antibody-drug conjugates to overcome these limitations and realize the full potential of this highly promising class of therapeutics. Methods: In this study, we demonstrate the feasibility of efficiently incorporating an azide-containing UAA into full-length antibody at different site and facilitate its site-specific functionalization, which provides a facile scale-up compatible route to generate precise antibody-drug conjugates with fine-tuned therapeutic properties. Specifically, we have engineered multiple variants of trastuzumab to contain the aforementioned UAA, enabling site-specific attachment of cytotoxic payloads, such as MMAE/MMAF, via click chemistry to generate ADCs with homogeneous DARs. Results: The resulting BrickBio ADCs exhibit high therapeutic efficacy against HER2+ cell lines in vitro as well as in mouse xenograft models. These homogenous ADCs additionally outperform traditional antibody conjugation technologies which lack site-specificity or site-selectivity. Conclusions: The ability to systematically vary the attachment topology between the drug and the antibody is a major strength of this approach and preliminary data suggest that such variation indeed affect ADC performance. BrickBio ADCs are currently in the preclinical stage with further efforts for safety studies underway.

SKB264 ADC: A first-in-human study of SKB264 in patients with locally advanced unresectable/metastatic solid tumors who are refractory to available standard therapies.

TPS3659 Background: Elevated expression of trophoblast antigen 2 (TROP2) is often associated with invasion/aggression, progression, and metastasis of many different tumor types. Efficacies of anti-TROP2 ADC have been demonstrated both pre-clinically and in the clinical trials. SKB264 is being developed as a further optimized TROP2-targeting ADC with a proprietary cytotoxic, belotecan-derived payload and novel stable conjugation chemistry to achieve average DAR (Drug Antibody Ratio) of 7.4. Release of payload upon SKB264 internalization is in a TROP2 expression dependent manner. Extensive preclinical studies demonstrated antitumor activity of SKB264 in vitro, in xenograft and patient-derived xenograft (PDX) animal models. In addition, safety studies have demonstrated a good safety profile to allow SKB264 to be studied in clinical trials. Methods: SKB264-01 is a global open label multicenter study. The study is divided into 2 parts, the phase I is to determine the safety profile, define MTD and/or the RP2D, and characterize DLTs of SKB264. Dose escalation and MTD identification will be directed using a Bayesian logistic regression model (BLRM) with overdose control. The phase II is to evaluate efficacy and obtain clinical activity data of SKB264 as a monotherapeutic agent at the RP2D in each of the designated Phase II cohorts and overall (n = 16 per cohort; n = 48 for entire Phase II part). Objective response rate (ORR) will be continuously evaluated in each cohort using a Bayesian hierarchical model. TROP2 assessments will not be performed prior to enrollment but it will be assessed retrospectively. Confirmation of TROP2 expression by immunohistology or other methods is not required, but the Sponsor will request tissue specimens from archived materials for determination of TROP2 expression. The patient must have, in the judgment of the investigator, historically documented, incurable, locally advanced or metastatic cancer that are refractory to standard therapies of one of the following types: i. ovarian epithelial cancer, ii. gastric adenocarcinoma, iii. pancreatic adenocarcinoma, iv. triple negative breast cancer, v. bladder cancer. Patient will receive study drug as a single IV infusion at the prescribed dose level at each administration. Cycles will continue until disease progression or unacceptable toxicity. Adverse Events (AE) will be graded according to CTCAE V.5.0. Responses will be evaluated according to RECIST V1.1. The enrollment will began in Mar 2020 in USA sites. Clinical trial information: NCT04152499 .

Potentials of human bile acids and their salts in pharmaceutical nano delivery and formulations adjuvants.

In the last decade, the attention of the scientific community has been focused on bile acids and their salts as systems for the transportation of drugs; specifically their role as carriers and integration into nanomedicine. Bile acids can play a critical role as drug carriers in the form of chemical conjugates, complexation, mixed micelles formation as well as stabilized bile acid liposomes (bilosomes). The unique molecular structure and interaction of these amphiphilic-steroidal compounds make them an interesting subject of research. This review is based on literature research in order to emphasize the importance of bile acids and their salts as absorption modulators in order to improve therapeutic potentials of low bioavailability drugs.

A Purification Strategy Utilizing Hydrophobic Interaction Chromatography to Obtain Homogeneous Species from a Site-Specific Antibody Drug Conjugate Produced by AJICAP™ First Generation.

In recent years, site-specific antibody drug conjugates (ADC)s have been in great demand because they have an expanded therapeutic index compared with conventional ADCs. AJICAP™ technology is a chemical conjugation platform to obtain site-specific ADCs through the use of a class of Fc-affinity compounds. Promising results from early technology development studies led to further investigation of AJICAP™ ADC materials to obtain site-specific and homogeneous drug antibody ratio (DAR) ADCs. Here we report site-specific conjugation followed by a preparative hydrophobic interaction chromatography (HIC) purification strategy to obtain purified “DAR = 1.0” and “DAR = 2.0” AJICAP™ ADC materials. Optimization of the mobile phase conditions and resin achieved a high recovery rate. In vitro biological assay demonstrated the target selective activity for purified homogeneous DAR ADCs. These results indicate the ability of a HIC purification strategy to provide “DAR = 1.0” and “DAR = 2.0” AJICAP™ ADCs with considerable potency and target selectivity.

Isoniazid-phytochemical conjugation: A new approach for potent and less toxic anti-TB drug development.

Mycobacterium tuberculosis (Mtb) causes one of the most grievous pandemic infectious diseases, tuberculosis (TB), with long-term morbidity and high mortality. The emergence of drug-resistant Mtb strains, and the co-infection with human immunodeficiency virus, challenges the current WHO-TB stewardship programs. The first-line anti-TB drugs, isoniazid (INH) and rifampicin (RIF), have become extensively obsolete in TB control from chromosomal mutations during the last decades. However, based on clinical trial statistics, the production of well-tolerated anti-TB drug(s) is miserably low. Alternately, semi-synthesis or structural modifications of first-line obsolete antitubercular drugs remain as the versatile approach for getting some potential medicines. The use of any suitable phytochemicals with INH in a hybrid formulation could be an ideal approach for the development of potent anti-TB drug(s). The primary objective of this review was to highlight and analyze available INH-phytochemical hybrid research works. The utilization of phytochemicals through chemical conjugation is a new trend toward the development of safer/non-toxic anti-TB drugs.

SAT-283 Generation of a Long-Acting Human Growth Hormone Receptor Antagonist by Site-Specific Pegylation

Growth hormone (GH) is a peptide hormone that mediates actions through binding to a cell surface GH receptor (GHR), activating key signalling pathways including the JAK/STAT pathway. Excess GH secretion leads to acromegaly and tumoral expression has been implicated in cancer progression, suggesting that GH is also a potential target for anticancer therapy. Pegvisomant is the only GHR antagonist approved for clinical use. This antagonist is a PEGylated form of a mutated GH (B2036) that binds and blocks the receptor. Conjugation to polyethylene glycol (PEG) at multiple amine residues reduces in vitro bioactivity but extends the serum half-life resulting in improved in vivo bioactivity. We investigated whether we could generate a long-acting PEGylated GHR antagonist through site-specific conjugation of PEG. A codon optimised GHR antagonist, with an introduced free cysteine residue at amino acid site 144 (S144C), was generated by gene synthesis and recombinantly engineered by gene fusion with thioredoxin. Recombinant protein was expressed in E. coli and purified using a series of chromatographic methods. Antagonists were PEGylated using cysteine-specific conjugation chemistry. In vitro activity was determined using a Ba/F3-GHR viability assay, and in vivo pharmacokinetic and bioactivity was determined in mice. Fusion to thioredoxin was found to improve soluble protein expression at 30℃, resulting in dramatically increased yield. After a series of purification steps, including Ni-NTA, 3C protease cleavage and ion-exchange chromatography, a single band with a molecular mass of 22 kDa was observed by SDS-PAGE analysis. The recombinant antagonist was conjugated to 20 kDa or 30 kDa-PEG at amino acid site S144C. After purification, a single band with an effective molecular size of approximately 60 kDa (PEG-20kDa conjugate) or 70 kDa (PEG-30kDa conjugate) was observed by SDS-PAGE analysis. The unconjugated antagonist inhibited the proliferation of Ba/F3-GHR cells in a dose-dependent manner with a half maximal inhibitory concentration (IC50) of 10.1 ± 2.5 nM. Following PEGylation and purification, the PEG-20kDa and PEG-30kDa conjugates retained high in vitro bioactivity with an IC50 of 66.2 ± 3.8 nM and 106.1 ± 7.1 nM, respectively. Pharmacokinetic analysis demonstrated that PEGylation increased the serum half-life to approximately 15 hours in mice. Subcutaneous administration of the PEG-30kDa conjugate (10 mg/kg/day) reduced serum IGF-I levels in mice. In conclusion, we have generated a novel long-acting human GHR antagonist conjugate by introducing a free cysteine at a non-essential site of the antagonist and targeted attachment of PEG.

Lipid-mimicking peptide decorates erythrocyte membrane for active delivery to engrafted MDA-MB-231 breast tumour

Decorating the membrane surface of vesicle carriers with proteins for targeted delivery has been achieved mainly by chemical methods. In this study, we report the rational design of a lipid-mimicking peptide for biomembrane decoration without chemical conjugation. A peptide Pm45 consisting of a hydrophobic helical tail and an anionic headgroup linked with an integrin-targeting RGD moiety was manually designed. Pm45 was synthesized and characterized, which confirmed an alpha-helix at the C-terminal. Pm45 spontaneously intercalated into the lipid bilayer as illustrated by quartz crystal of microbalance with dissipation (QCM-D), a calcein leakage assay, and TEM. The intercalation was accomplished within 10 min, and the ITC results indicated that the affinity of Pm45 binding with lipids was ~100-fold greater than that of the naturally occurring cell-penetrating peptide Ib-AMP4. In vitro cellular experiments indicated that the Pm45-decorated erythrocyte vesicles specifically bound and killed integrin αvβ3-expressing MDA-MB-231 breast cancer cells. The targeting potential of Pm45-decorated erythrocyte vesicles was further evaluated in an MDA-MB-231 xenograft nude mouse model. The in vivo therapeutic effects indicated that the targeting vesicles significantly improved the therapeutic effect of encapsulated doxorubicin (DOX) compared with that of DOX or non-targeting vesicles. NIRF imaging implied that the targeting vesicles improved the pharmacokinetics of DOX in vivo and concentrated DOX in the tumour tissue at levels >50% higher than those achieved by non-targeting liposomes. This study reports a new method for liposome decoration as an alternative to chemical conjugation.

Electrochemically Tagging Elastin-like Polymers-Modified Au Surfaces

We are exploring Elastin-like-Polymer (ELP) as a transducing enhancement element for biosensors. While previous work in our lab has investigated surface-bound ELP conformational state with electrochemical impedance spectroscopy to understand its stimuli-response, we would like to use ELP as an electrically active transducer in sensor applications. To achieve this, we must understand how much of the ELP is covalently attached to the electrode and functionalize the electrochemically-inert ELP with a faradaic tag. We present a proof-of-concept model for modifying the C-terminus of the ELP with Toluidine Blue O, an electrically active phenothiazine compound. Our system uses simple and accessible conjugation chemistry for this purpose and is conducted in aqueous solution. Further, reducing the thiol bonds will remove the covalently-bound ELP from the electrode surface to obtain an estimate of the ELP surface coverageThus far, we have successful decoupled the thiol-gold bond using the cyclic voltammetry reduction technique.. Electrochemical impedance spectroscopy confirmed that the modified electrode after thiol desorption returned to a similar state compared to a bare electrode. Additionally, we successfully measured an electrochemical signal attributed to the Toluidine Blue O tag conjugated to ELP based on its redox properties (Figure 1). We intend to further expand this work by refining the conjugation protocol, comparing various tags and conjugation chemistries, and relating surface coverage to desorption amounts of covalently bound ELP. Acknowledgements: The authors would like to acknowledge the financial support from the College of Medicine at Drexel University, NSF (CBET 1638896), the Collaborative Research Excellence Initiative Pilot Research Program at the University of New Hampshire, and the Hamel Center of Undergraduate Research at the University of New Hampshire. The authors also would like to acknowledge the assistance of Dr. Balog’s laboratory and Dr. Halpern’s laboratory.

The development and characterization of a long acting anti‐thrombotic von Willebrand factor (VWF) aptamer

BackgroundThrombus formation involves coagulation proteins and platelets. The latter, referred to as platelet‐mediated thrombogenesis, is predominant in arterial circulation. Platelet thrombogenesis follows vascular injury when extracellular von Willebrand factor (VWF) binds via its A3 domain to exposed collagen, and the free VWF A1 domain binds to platelet glycoprotein Ib (GPIb). ObjectivesTo characterize the antiplatelet/antithrombotic activity of the pegylated VWF antagonist aptamer BT200 and identify the aptamer VWF binding site. MethodsBT100 is an optimized aptamer synthesized by solid‐phase chemistry and pegylated (BT200) by standard conjugation chemistry. The affinity of BT200 for purified human VWF was evaluated as was VWF inhibition in monkey and human plasma. Efficacy of BT200 was assessed in the monkey FeCl3 femoral artery thrombosis model. ResultsBT200 bound human VWF at an EC50 of 5.0 nmol/L and inhibited VWF A1 domain activity in monkey and human plasma with mean IC50 values of 183 and 70 nmol/L. BT200 administration to cynomolgus monkeys caused a time‐dependent and dose‐dependent effect on VWF A1 domain activity and inhibited platelet function as measured by collagen adenosine diphosphate closure time in the platelet function analyzer. BT200 demonstrated a bioavailability of ≥77% and exhibited a half‐life of >100 hours after subcutaneous injection. The treatment effectively prevented arterial occlusion in an FeCl3‐induced thrombosis model in monkeys. ConclusionsBT200 has shown promising inhibition of human VWF in vitro and prevented arterial occlusion in non‐human primates. These data including a long half‐life after subcutaneous injections provide a strong rationale for ongoing clinical development of BT200.

In silico design of a universal carrier protein: A potential solution to the variable immunogenicity observed in past vaccines against drugs of abuse

Abstract Vaccines against drugs of abuse (VADAs) show promise as a possible therapeutic for the alleviation of addiction due to their ability to modulate intake behavior via the altering of drug pharmacokinetics. In the past, however, these vaccines have failed to show clinical efficacy due to extensive variability in the magnitude of antibody response between individual vaccinees. Correspondingly, the future success of VADAs hinges directly on whether or not researchers can find ways to engineer more broadly effective vaccines. Differences in response must, to some extent, be the result of variable capacities for each individual’s immune system to process and/or present antigens. As such, we speculate that future VADAs will need to target the three key stages of vaccine processing, recognition, processing, and presentation, in order to achieve clinical effectiveness. Here, we describe a project aiming to engineer a broadly effective carrier protein based on this concept. Using haplotype frequency data provided by Be the Match, HLA-DQ and -DR haplotypes covering 99% of the population were selected for analysis. Next, the most common carrier proteins used in conjugate vaccine formulations were analyzed for MHC II epitope content using these haplotypes and NetMHCIIPan 3.2 prediction software. Finally, a modified version of the prediction output was used to excise the most likely MHC II epitopes. The highest-ranked epitopes were then stitched together using linkers designed with chemical conjugation sites and cathepsin cleavage sequences and subsequently tethered to cholera toxin subunit B. These results present the successful design of an in silico derived, broadly effective carrier protein to be used in future VADA formulations.

Improving efficacy of glycoconjugate vaccines: from chemical conjugates to next generation constructs.

Glycoconjugate vaccines are among the safest and most successful vaccines developed during the past 30 years. Since the first semisynthetic chemical conjugate vaccine licensed in the 1980's to protect human against Haemophilus influenzae type b infection, conjugate vaccines against Neisseria meningitidis and Streptococcus pneumoniae have been developed and registered using the same approach (i.e. bacterial growth to produce capsular polysaccharide antigen and chemical coupling to carrier protein). Other types of conjugate vaccines have been recently developed and tested in clinical trials, prepared by coupling chemically synthesized oligosaccharides to proteins, by engineering Escherichia coli to directly produce bioconjugates or by delivering the native carbohydrate antigen in engineered membrane vesicles (i.e. Generalized Modules for Membrane Antigens, GMMA). Through this review, the reader will have an insight regarding the history and the characteristics of different types of conjugate vaccines, and the attributes that might affect their immunogenicity and their potential for future applications.

Calcium-cation-doped polydopamine-modified 2D black phosphorus nanosheets as a robust platform for sensitive and specific biomolecule sensing

Many polymer decorated/modified 2D nanomaterials have been developed as enhanced drug delivery systems and photothermal theranostic nanoagents. However, few reports describe the use of these novel nanomaterials as nanoplatforms for biomolecule sensing. Herein, we used calcium-cation-doped polydopamine-modified (PDA-modified) 2D black phosphorus (BP) nanosheets (BP@PDA) as a sensing nanoplatform for the detection of nucleic acids and proteins in complex biological samples. Fluorescent-dye-labeled single-strand DNA aptamer/probes are adsorbed by the Ca2+-doped BP@PDA mediated by calcium-cation coordination. The PDA coating enhances the stability of the inner BP, provides binding sites to DNA nucleobases, and quenches fluorescence. Without any chemical conjugation, this sensing nanoplatform selectively and specifically detects protein (human thrombin, linear range: 10–25 nM, detection limit: 0.02 nM), single-strand DNA (linear range: 1–10 nM, detection limit: 0.52 nM) in 1% serum diluted samples, and senses intracellular mRNAs (C-myc, and actin) in living cells. The nanoplatform exhibits the advantages of both the 2D nanomaterial (BP) and the coating polymer (PDA), naturally enters living cells unaided by transfection agents, resists enzymatic lysis and shows high biocompatibility. This nanoplatform design contributes towards future biomolecule analytical method development based on polymer decorated/modified 2D nanomaterials.

Plant Virus Nanoparticles for Vaccine Applications.

In the rapidly evolving field of nanotechnology, plant virus nanoparticles (pVNPs) are emerging as powerful tools in diverse applications ranging from biomedicine to materials science. The proteinaceous structure of plant viruses allows the capsid structure to be modified by genetic engineering and/or chemical conjugation with nanoscale precision. This means that pVNPs can be engineered to display peptides and proteins on their external surface, including immunodominant peptides derived from pathogens allowing pVNPs to be used for active immunization. In this context, pVNPs are safer than VNPs derived from mammalian viruses because there is no risk of infection or reversion to pathogenicity. Furthermore, pVNPs can be produced rapidly and inexpensively in natural host plants or heterologous production platforms. In this review, we discuss the use of pVNPs for the delivery of peptide antigens to the host immune in pre-clinical studies with the final aim of promoting systemic immunity against the corresponding pathogens. Furthermore, we described the versatility of plant viruses, with innate immunostimulatory properties, in providing a huge natural resource of carriers that can be used to develop the next generation of sustainable vaccines.

Virus-Like Particles as an Immunogenic Platform for Cancer Vaccines.

Virus-like particles (VLP) spontaneously assemble from viral structural proteins. They are naturally biocompatible and non-infectious. VLP can serve as a platform for many potential vaccine epitopes, display them in a dense repeating array, and elicit antibodies against non-immunogenic substances, including tumor-associated self-antigens. Genetic or chemical conjugation facilitates the multivalent display of a homologous or heterologous epitope. Most VLP range in diameter from 25 to 100 nm and, in most cases, drain freely into the lymphatic vessels and induce antibodies with high titers and affinity without the need for additional adjuvants. VLP administration can be performed using different strategies, regimens, and doses to improve the immunogenicity of the antigen they expose on their surface. This article summarizes the features of VLP and presents them as a relevant platform technology to address not only infectious diseases but also chronic diseases and cancer.

Understanding the Pharmaceutical Aspects of Dendrimers for the Delivery of Anticancer Drugs.

Dendrimers are emerging class of nanoparticles used in targeted drug delivery systems. These are radially symmetric molecules with well-defined, homogeneous, and monodisperse structures. Due to the nano size, they can easily cross the biological membrane and increase bioavailability. The surface functionalization facilitates targeting of the particular site of action, assists the high drug loading and improves the therapeutic efficiency of the drug. These properties make dendrimers advantageous over conventional drug delivery systems. This article explains the features of dendrimers along with their method of synthesis, such as divergent growth method, convergent growth method, double exponential and mixed method, hyper-core and branched method. Dendrimers are effectively used in anticancer delivery and can be targeted at the site of tumor either by active or passive targeting. There are three mechanisms by which drugs interact with dendrimers, and they are physical encapsulation, electrostatic interaction, chemical conjugation of drug molecules. Drug releases from dendrimer either by in vivo cleavage of the covalent bond between drugdendrimer complexes or by physical changes or stimulus like pH, temperature, etc.

Expanding the Scope of Antibody Rebridging with New Pyridazinedione-TCO Constructs.

Disulfide rebridging methods have recently emerged as a route to hinge region-specific antibody modification, and there exist numerous examples of successful rebridging chemistry applied to clinically relevant human IgG1 antibodies. Here, dibromopyridazinedione disulfide rebridging is adapted to fast trans-cyclooctene/tetrazine (TCO/Tz) bioorthogonal ligations and extended beyond therapeutic human IgG1 antibodies for the first time to include mouse and rat monoclonal antibodies integral to multiplexed analytical diagnostics. In spite of a common architecture, only a subset of antibody host species and IgG isotype subclasses can be rebridged, highlighting the intricate relationship between hinge region sequence, structure, biological activity, and the conjugation chemistry of IgG antibodies.