Small Molecule Counterparts Research Articles

Synthesis and characterization of fluorinated conjugates of albumin

A small fluorocarbon dendron that contains nine chemically identical fluorine atoms was covalently conjugated to albumin via a flexible linker. Two versions were made, which differ by 10% in the linker length. Both versions display split 19F signal and much shorter 19F longitudinal relaxation time than their small molecule counterparts. 10% difference in the flexible linker length has negligible impact on the 19F signal.

Interpatient Pharmacokinetic and Pharmacodynamic Variability of Carrier-Mediated Anticancer Agents

Major advances in the field of carrier-mediated agents (CMAs) have revolutionized drug delivery capabilities over the past decade. While providing numerous advantages over their small-molecule counterparts (solubility,duration of exposure, and delivery to the site of action are higher), these agents display substantial variability in systemic clearance (CL) and distribution, tumor delivery, and pharmacologic effects. This review provides an overview of factors that affect the pharmacokinetics (PK) and pharmacodynamics (PD) of CMAs in preclinical models and patients.

Synthesis of New Polyelectrolytes via Backbone Quaternization of Poly(aryloxy- and alkoxyphosphazenes) and their Small Molecule Counterparts

Novel polyelectrolytes were synthesized by quaternization of the backbone of poly(alkoxy- and aryloxyphosphazenes) with strong alkylation reagents. As models for the synthesis of these polymers, similar quaternization reactions were also carried out on small-molecule alkoxy and aryloxy cyclotriphosphazenes. The quaternized small molecules and high polymers were characterized by 1 H NMR, 31 P NMR, DSC, TGA, and AC impedance studies. The quaternized poly(alkoxyphosphazenes) showed ionic conductivities of 2.58 × 10 −4 S·cm −1 at 25 °C and 2.09 × 10 −3 S·cm −1 at 80 °C, which are among the highest values for known solvent-free ionically conducting polymers.

P4-17-04: Pharmacokinetic Disposition of PEGylated Liposomal Doxorubicin Compared with Non-Liposomal Doxorubicin in an Intracranial Breast Cancer Murine Model.

Abstract Background Breast cancer brain metastases are an increasingly common consequence of advanced breast cancer associated with poor prognosis and survival. Systemic therapies capable of crossing the blood brain barrier to control both intra- and extracranial disease are few. Nanoparticle agents, such as liposomes, achieve a higher concentration and prolonged exposure in solid tumors. Liposomal formulations of anti-cancer agents have also been shown in preclinical and clinical studies to enhance delivery to tumors within the brain. We compared the pharmacokinetic (PK) disposition of PEGylated liposomal doxorubicin (Doxil®; PLD) with non-liposomal doxorubicin (NLD) in an intracranial breast cancer model. Methods: Athymic (nu/nu) mice (∼8wks) were inoculated with MDA-MB-231-BR (brain subclone) cells expressing luciferase (2×105 cells/injection) in 5% methylcellulose (5 μL) into the right caudate nucleus. On day 18, tumor-bearing mice via bioluminescence imaging were administered PLD or NLD at 6 mg/kg IV x 1 via tail vein. Mice (n=3) were sacrificed at 6 and 24h for PLD and NLD; and 72h for PLD. Plasma and intracranial tumor were processed to measure sum total doxorubicin via high-performance liquid chromatography (HPLC, lower limit of quantification=10 ng/mL). T-tests were used to compare means between treatment groups. Results: Treatment with PLD resulted in higher plasma sum total doxorubicin concentrations compared with NLD (Table). PLD was detected at 72h in plasma. There were higher intracranial tumor sum total doxorubicin concentrations at 6 and 24h for PLD compared with NLD; NLD was below limit of quantification (BLQ) at both time points. Consistent with the plasma PK of PLD, intracranial tumor sum total doxorubicin concentrations for PLD remained elevated at 72h. Conclusions: Liposomal formulations of anti-cancer agents represent a promising treatment strategy to treat aggressive breast cancer brain metastases due to extended circulation time in plasma and higher exposure in intracranial tumor compared with small molecule counterparts. In this proof-of-concept preclinical study, PLD exhibits both higher and prolonged plasma and intracranial tumor exposure compared with NLD. The mechanism of higher intracranial tumor exposure with liposomal agents is unknown, however may be due to prolonged exposure in plasma, diffusion of encapsulated and/or released drug across the blood brain barrier, or enhanced permeation and retention effect in tumors. The improved PK profile and tumor distribution of PLD compared with NLD in this intracranial BC model are hypothesized to translate to improved efficacy and toxicity profiles over that of non-liposomal formulations and may represent a promising treatment strategy for a disease with limited treatment options. Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P4-17-04.

Reversion of Sulfenamide Prodrugs in the Presence of Free Thiol-Containing Proteins

The purpose of this work was to study the reaction kinetics between two model sulfenamide prodrugs of linezolid, N-(phenylthio)linezolid and N-[(2-ethoxycarbonyl)ethylthio]linezolid, with free thiol-containing proteins; commercial human serum albumin (HSA); a constitutively active mutant of the protein tyrosine phosphatase PRL-1 (PRL-1-C170S-C171S), a model protein; and diluted fresh human plasma. The reaction was followed by high-performance liquid chromatography, both for the loss of prodrug and appearance of linezolid, and at different pH values with molar excess of the proteins relative to the prodrugs. Pseudo first-order kinetics was observed. Consistent with earlier findings for the reaction between similar sulfenamides and small-molecule thiols, the reaction kinetics appeared to be consistent with thiolate attack at the sulfenamide bond to release the parent drug. The proteins reacted significantly slower on a molar basis than their small-molecule counterparts. It appears that proteins such as HSA may play a role in the in vivo conversion of sulfenamide prodrugs to their parent drug.

Design of clinically useful macromolecular iron chelators

In recent years, macromolecular iron chelators have received increasing attention as human therapeutic agents. The objectives of this article are: one, to discuss the factors which should be considered when designing iron binding macromolecules as human therapeutic agents, and two, to report recent achievements in the design and synthesis of appropriate macromolecular chelators that have resulted in the production of a number of agents with therapeutic potential. Macromolecular drugs exhibit unique pharmaceutical properties that are fundamentally different from their traditional small-molecule counterparts. By virtue of their high-molecular-weight characteristics, many are confined to extracellular compartments, for instance, the serum and the gastrointestinal tract. In addition, they have potential for topical administration. Consequently, these macromolecular drugs are free from many of the toxic effects that are associated with their low-molecular-weight analogues. The design and synthesis of macromolecular iron chelators provides a novel aspect to chelation therapy. 3-Hydroxypyridin-4-one hexadentate-based macromolecular chelators have considerable potential for the development of new treatments for iron overload and for topical treatment of infection.

Abstract 371: Comparison of toxicity and study design issues of nanoparticle and small molecule anticancer agents in preclinical models and phase I clinical trials

Abstract Background: Carrier-mediated agents (CMA) are classified as nanoparticles, nanosomes (nanoparticle sized liposomes) and conjugates. Anticancer CMA offer many unique advantages over their traditional small molecule (SM) counterparts, including improved solubility, longer duration of exposure, tumor-selective delivery, increased antitumor response and reduced toxicity. The interpatient variability in pharmacokinetics (PK) and pharmacodynamics (PD) associated with nanoparticles are greater than that observed with SM. The starting dose for phase I studies of SM and CMA anticancer agents is based on the toxicity profile of the most sensitive species (e.g. rat or canine). However, the optimal animal model for toxicologic and pharmacologic studies of CMA is unclear. Our preliminary data suggests that dogs are highly sensitive to nanoparticles and thus may not be an appropriate animal model in determining the starting dose of CMA for phase I clinical trials. We evaluated preclinical toxicology data and how this affected the design and progression of phase I studies of CMA compared to SM anticancer agents. Methods: In preclinical studies, the maximum tolerated dose (MTD) in rats and dogs was evaluated for CMA and their respective SM. In phase I clinical trials of CMA and their respective SM in patients with advanced solid tumors, the basis for starting dose, the number of dose escalations, number of patients and the ratio of MTD to starting dose was determined. Results: Starting dose in phase I studies of CMA was based on dogs. Conclusions: The degree of dose escalation from starting dose to MTD was significantly greater for CMA compared to SM drugs. This was also associated with a significantly greater number of dose levels, patients, and time required to complete phase I studies of CMA compared to SM. These findings necessitate the need to identify the most appropriate preclinical animal model to use to evaluate CMA toxicity in phase I studies. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 371. doi:10.1158/1538-7445.AM2011-371

A practical guide to the construction of radiometallated bioconjugates for positron emission tomography.

Positron emission tomography (PET) has become a vital imaging modality in the diagnosis and treatment of disease, most notably cancer. A wide array of small molecule PET radiotracers have been developed that employ the short half-life radionuclides (11)C, (13)N, (15)O, and (18)F. However, PET radiopharmaceuticals based on biomolecular targeting vectors have been the subject of dramatically increased research in both the laboratory and the clinic. Typically based on antibodies, oligopeptides, or oligonucleotides, these tracers have longer biological half-lives than their small molecule counterparts and thus require labeling with radionuclides with longer, complementary radioactive half-lives, such as the metallic isotopes (64)Cu, (68)Ga, (86)Y, and (89)Zr. Each bioconjugate radiopharmaceutical has four component parts: biomolecular vector, radiometal, chelator, and covalent link between chelator and biomolecule. With the exception of the radiometal, a tremendous variety of choices exists for each of these pieces, and a plethora of different chelation, conjugation, and radiometallation strategies have been utilized to create agents ranging from (68)Ga-labeled pentapeptides to (89)Zr-labeled monoclonal antibodies. Herein, the authors present a practical guide to the construction of radiometal-based PET bioconjugates, in which the design choices and synthetic details of a wide range of biomolecular tracers from the literature are collected in a single reference. In assembling this information, the authors hope both to illuminate the diverse methods employed in the synthesis of these agents and also to create a useful reference for molecular imaging researchers both experienced and new to the field.

Therapeutic Nanoparticles to Combat Cancer Drug Resistance

This review focuses on the application of drug-loaded nanoparticles (NPs), also called therapeutic NPs, to combat cancer chemoresistance. Many cancer patients have encouraging response to first line chemotherapies but end up with cancer progression or cancer recurrence that requires further treatment. Response to subsequent chemotherapies with various agents usually drops significantly due to formidable cancer chemoresistance. A number of mechanisms have been postulated to account for cancer chemoresistance or poor response to chemotherapy. The best studied mechanism of resistance is mediated through the alteration in the drug efflux proteins responsible for the removal of many commonly used anticancer drugs. Therapeutic NPs have emerged as an innovative and promising alternative of the conventional small molecule chemotherapies to combat cancer drug resistance and have shown enhanced therapeutic efficacy and reduced adverse side effects as compared to their small molecule counterparts. Here the possible mechanisms of therapeutic NPs to combat cancer chemoresistance are reviewed, including prolonging drug systemic circulation lifetime, targeted drug delivery, stimuli-responsive drug release, endocytic uptake of drugs and co-delivering chemo-sensitizing agents. We also call attention to the current challenges and needs of developing therapeutic NPs to combat cancer drug resistance.

Wrenchnolol Derivative Optimized for Gene Activation in Cells

Naturally occurring transcription factors usually have two independent domains, a DNA-binding domain and an activation domain. In designing a synthetic small molecule that mimics a transcription factor, each of the two domains needs to be replaced by small-molecule counterparts. Results of the present study show that derivatives of wrenchnolol, a synthetic molecule that interacts with Sur-2 coactivator, serve as activation modules and stimulate gene transcription in vitro and in cells when tethered to a DNA-binding molecule. Thirteen derivatives of wrenchnolol were chemically synthesized and tested for their ability to activate transcription in vitro and in cells. When tethered to the GAL4 DNA-binding domain, one derivative increased transcription of a GAL4-responsive reporter gene in cells 9-fold. This optimized derivative also induced up to 45% myogenesis of C2C12 cells when tethered to the DNA-binding domain of myogenic transcription factor MyoD. This optimized derivative may serve as a starting point for designing biological tools or components of fully synthetic transcription factors that permit selective up-regulation of genes.

Biologically active polymeric sequestrants: Design, synthesis, and therapeutic applications

Abstract In recent years, functional polymers exhibiting inherently biological activities have been receiving increasing attention as polymer-based human therapeutic agents. These polymeric drugs exhibit unique pharmaceutical properties that are fundamentally different from their traditional small-molecule counterparts. However, unlike polymeric drug delivery systems, examples of polymers possessing intrinsically therapeutic properties are relatively scarce. By virtue of their high-molecular-weight characteristics, these polymeric drugs can be confined to the gastrointestinal (GI) tract, where they can selectively recognize, bind, and remove target disease-causing substances from the body. Being confined to the GI tract and non-biodegradable, these polymeric drugs are free from toxic effects that are associated with traditional systemic drugs. This report highlights recent developments in the rational design and synthesis of appropriate functional polymers that have resulted in a number of promising polymer-based therapeutic agents, including some marketed products.

Supramolecular assemblies from amphiphilic homopolymers: Testing the scope.

It has been shown by us in a recent communication that homopolymers, in which each repeat unit contains a hydrophilic and a hydrophobic head group, are capable of forming environment-dependent micellar or inverse micellar assemblies. A systematic structure-property relationship study is carried out here to test the scope of the design. We show here that the molecular design is indeed broadly applicable and that there is a significant gain in the critical aggregation concentrations of these polymers, as compared to the small molecule counterparts. We also show that the design can be tuned to achieve vesicle-type assemblies, which further expands the repertoire of amphiphilic homopolymers in a variety of areas. Characterizations of these assemblies have been carried out using transmission electron microscopy, dynamic light scattering, static light scattering, and dye incorporation experiments.

Polymer Light Emitting Diodes Made by Ink Jet Printing

Since its discovery in 1989, electroluminescence from conjugated polymers has been a field of intensive research. One particular advantage of polymers compared to their small molecule counterparts is their processability from solution. This makes them the ideal active layer to be used for flat panel displays because the different colors can be ink jetted economically even onto relatively large substrates. Ink jet technology for polymer light emitting diodes (PLEDs) and full color displays, however, is not yet an established display production technology. A detailed understanding of the underlying principles and the interaction of print head, ink and substrate is a prerequisite for the development of the technology. This paper presents performance data of ink jetted PLEDs and compares them with the respective spin coated devices. These devices have been prepared on a substrate with a simple, low resolution photo resist structure. As the target application is the manufacture of full color displays, the light emitting polymers investigated in this study were red, green and blue. The results show that a careful choice of the printing parameters and environment results in devices with current-voltage, brightness-voltage and emission characteristics comparable to spin coating samples, which have been prepared as reference. The film homogeneity of the functional layers turned out to be of utmost importance and can be influenced by various jetting parameters.

Interactions between dendrimer biocides and bacterial membranes

Dendrimer biocides have been shown to be more potent than their small molecule counterparts. In this study, several techniques were utilized to investigate the interactions between quaternary ammonium functionalized poly(propylene imine) dendrimers and bacterial membranes. Both Gram-positive and Gram-negative bacteria were tested. The techniques employed include UV–Vis spectroscopy, differential scanning calorimetry, and bioluminescence. When treated with dendrimer biocides, release of 260nm adsorbing materials from Escherichia coli strains quickly increased and reached a plateau afterwards, while release of 260nm absorbing materials from Staphylococcus aureus increased monotonically with the concentration due to the difference in cell structures. The different release behavior also correlates with the antimicrobial properties against these two types of bacteria. Bioluminescence experiments using bacteria containing stress-responsive bioluminescent reporter gene fusions provided information suggesting that damage to the cell membranes is the primary mechanism of the antimicrobial action for dendrimer biocides. High concentrations of calcium ions can limit the efficacy of the dendrimer biocides, although the tested concentration range is much higher than most practical applications. Differential scanning calorimetry studies showed at high concentrations that dendrimer biocides formed precipitates with phospholipid vesicles, suggesting a strong interaction with this model of bacterial membrane. These results provide insight about the antibacterial action of dendrimer biocides and establish the basis for their mode of action.

Polymer Light Emitting Diodes Made by Inkjet Printing

Since its discovery in 1989 (1,2), electroluminescence from conjugated polymers has been a field of intensive research. One particular advantage of polymers compared to their small molecule counterparts is their processability from solution. This makes them the ideal active layer to be used for flat panel displays because the different colors can be inkjetted (3) economically even onto relatively large substrates. Inkjet technology for polymer light emitting diodes (PLEDs) and full color displays, however, is not fully developed yet, and a detailed understanding of the underlying principles and the interaction of printhead, ink and substrate has not been achieved thus far. This paper presents performance data of inkjetted PLEDs and compares them with the respective spin-coated devices. The results show the importance of the film homogeneities of the functional layers and how they can be influenced by various jetting parameters. Cross sections of inkjetted drops are vastly different depending on the drying conditions (underlayer, substrate temperature, formulation, surrounding atmosphere). Devices have been prepared on a substrate with a simple, low resolution photoresist structure. These devices show that the PL-image alone is not sufficient to predict the resulting EL image.

Antibacterial activity and mutagenicity studies of water-soluble phosphazene high polymers

Eight water-soluble phosphazene high polymers, [NPR 2] n ( R, organic, water-solubilizing side-group; n, approx: 15 000) and the small-molecule counterparts of the polymers were examined for antibacterial activity against six different strains of bacteria ( Escherichia coli, Salmonella typhimurium (TA 100), Salmonella pullorum, Streptococcus faecalis. Bacillus subtilis and Pseudomonas aeruginosa). Antibacterial testing was carried out by measuring zones of inhibition and changes in solution turbidity over time. In addition, the antibacterial activity of the surfaces of cross-linked poly[di(methoxyethoxyethoxy)phosphazene] (MEEP) hydrogels were investigated. A number of the high polymers, as well as the MEEP hydrogels, impeded bacterial growth. Only E. coli was unaffected by the phosphazenes. A possible explanation for the antibacterial character of the polymers is presented. The same compounds were monitored for potential mutagenic activity using the Salmonella typhimurium tester strains TA 100 and TA 98. None of the high polymers or their small-molecule analogues showed mutagenic activity in either strain of Salmonella at the concentrations tested. The use of these materials as coatings for artificial implants is discussed.

Bilayer Formation by Aggregation of Polymeric Amphiphiles

Abstract Acrylic monomers possessing dialkyl(double-chain) and single-chain tails were prepared. The tail portions are made of characteristic structures common to the hydrophobic portion of bilayer-forming amphiphiles. They are dialky(C12 to C18)chains connected by amide, glyceryl ether or glutamate moieties or single chains with rigid aromatic segments(azobenzene and biphenyl). These monomers were copolymerized by azobisisobutyronirile with hydrophilic monomers such as acrylamide, acrylglycinamide and other charged monomers. Copolymers which contain as much hydrophobic units as possible were dispersed in water by sonication. They formed the bilayer aggregate spontaneously, as confirmed by electron microscopy, differential scanning calorimetry and small-angle laser light scattering. On average, 10 to 10 polymer molecules aggregate to form huge(molecular weight, 106–108) bilayer aggregates. The bilayer assemblage of the polymeric amphiphiles appears to be inferior to that of the small-molecule counterparts...