Biomedical subjects

David Filpula

Publications and source records attributed to David Filpula.

7 recordsLinked to original sources

PubMed2006

A highly stable polyethylene glycol-conjugated human single-chain antibody neutralizing granulocyte-macrophage colony stimulating factor at low nanomolar concentration.

GM-CSF (granulocyte-macrophage colony stimulating factor) plays a central role in inflammatory processes. Treatment with antibodies neutralizing murine GM-CSF showed significant therapeutic effects in mouse models of inflammatory diseases. We constructed by phage display technology a human scFv, which could potently neutralize human GM-CSF. At first, a human V(L) repertoire was combined with the V(H) domain of a parental GM-CSF-neutralizing rat antibody. One dominant rat/human scFv clone was selected, neutralizing human GM-CSF with an IC50 of 7.3 nM. The human V(L) of this clone was then combined with a human V(H) repertoire. The latter preserved the CDR 3 of the parental rat V(H) domain to retain binding specificity. Several human scFvs were selected, which neutralized human GM-CSF at low nanomolar concentrations (IC50 > or = 2.6 nM). To increase serum half-life, a branched 40 kDa PEG-polymer was coupled to the most potent GM-CSF-neutralizing scFv (3077) via an additional C-terminal cysteine. PEG conjugation had a negligible effect on the in vitro neutralizing potential of the scFv, although it caused a significant drop in binding affinity owing to a reduced on-rate. It also significantly increased the stability of the scFv at elevated temperatures. In mouse experiments, the PEGylated scFv 3077 showed a significantly prolonged elimination half-life of 59 h as compared with 2 h for the unconjugated scFv version. PEGylated scFv 3077 is a potential candidate for development of a novel antibody therapy to treat pro-inflammatory human diseases.

Animals↗

PubMed2005

Antitumor activity of poly(ethylene glycol)-camptothecin conjugate: the inhibition of tumor growth in vivo.

Antitumor effect of poly(ethylene glycol)-camptothecin conjugate (PEG-CPT) was studied in the nude mouse model of human colon cancer xenografts. The animals were treated intravenously with 15 mg/kg of camptothecin (CPT) or PEG-CPT conjugate at equivalent CPT dose. Antitumor activity, apoptosis induction and caspase-dependent signaling pathways were studied 12, 24, 48 and 96 h after single injection. In addition, pharmacokinetics, tumor distribution and accumulation of PEG polymer labeled with green fluorescence protein (GFP) were studied. The data obtained showed that the conjugation of low molecular weight anticancer drug CPT with low solubility to high molecular weight water-soluble PEG polymer provides several advantages over the native drug. First, the conjugation improves drug pharmacokinetics in the blood and tumor. Second, such conjugation provides passive tumor targeting by the Enhanced Permeability and Retention (EPR) effect, increasing drug concentration in the tumor. Third, the coupling increases the bioavailability of CPT, induces apoptosis in tumor and, therefore, enhances anticancer activity of PEG-CPT. Thus, the use of macromolecular conjugate provided passive tumor targeting of the drug, improved pharmacokinetics and increased the stability of the drug during circulation. It offered better uptake by the targeted tumor cells and substantially enhanced apoptosis and antitumor activity of the conjugated drug in the tumor and decreased apoptosis in liver and kidney as compared with the native drug. All these characteristics make PEG-CPT conjugate an attractive anticancer drug for the effective chemotherapy of solid tumors.

Animals↗

PubMed2003

Tailoring structure-function and pharmacokinetic properties of single-chain Fv proteins by site-specific PEGylation.

The utility of single-chain Fv proteins as therapeutic agents would be realized if the circulating lives of these minimal antigen-binding polypeptides could be both prolonged and adjustable. We have developed a general strategy for creating tailored monoPEGylated single-chain antibodies. Free cysteine residues were engineered in an anti-TNF-alpha scFv at the C-terminus or within the linker segments of both scFv orientations, V(L)-linker-V(H) and V(H)-linker-V(L). High-level expression of 10 designed variant scFv proteins in Pichia pastoris allowed rapid purification. Optimization of site-specific conjugate preparation with 5, 20 and 40 kDa maleimide-PEG polymers was achieved and a comparison of the structural and functional properties of the scFv proteins and their PEGylated counterparts was performed. Peptide mapping and MALDI-TOF mass spectrometric analysis confirmed the unique attachment site for each PEG polymer. Independent biochemical and bioactivity analyses, including binding affinities and kinetics, antigenicity, flow cytometric profiling and cell cytotoxicity rescue, demonstrated that the functional activities of the 10 designed scFv conjugates are maintained, while scFv activity variations between these alternative assays can be correlated with conjugate and analytical designs. Pharmacokinetic studies of the PEGylated scFv in mice demonstrated up to 100-fold prolongation of circulating lives, in a range comparable to clinical antibodies.

Animals↗

PubMedDate not supplied

Controlled release of proteins from their poly(ethylene glycol) conjugates: drug delivery systems employing 1,6-elimination.

Several tripartate releasable PEG linkers (rPEG) that can provide anchimeric assistance to hydrolysis (cyclization prodrugs) were prepared and, after conjugation to lysozyme demonstrated rapid cleavage in rat plasma compared to nonassisted, permanently bound PEG. By varying the chemical structure and adding steric hindrance, the half-life of the protein conjugates can be adjusted from slow to very fast. The pharmacokinetics (PK) of regeneration of native protein, from various rPEG conjugates can, for the first time, be easily followed in the rat using green fluorescent protein. The PK in mice was also determined for rPEG-Interleukin 2 (rPEG-IL-2) conjugates in vivo using an ELISA assay. Thus, a systematic study of rPEGylated proteins, either in vivo or in vitro during processing, has been investigated based on regeneration of native protein. The employment of releasable PEG polymers substantially broadens the applications of PEGylation drug delivery technology by introducing the benefits of controlled release of native protein therapeutics.

Animals↗

PubMedDate not supplied

Linear and branched bicin linkers for releasable PEGylation of macromolecules: controlled release in vivo and in vitro from mono- and multi-PEGylated proteins.

The utility of PEGylation for improving therapeutic protein pharmacology would be substantially expanded if the authentic protein drugs could be regenerated in vivo. Diminution of kinetic constants of both enzymes and protein ligands are commonly encountered following permanent bioconjugation with poly(ethylene glycol) polymers. In further development of releasable linker technology, we investigated an amino PEG anchimeric prodrug system, based on either the linear or branched bicin3 (BCN3) linkage, one promising representative of several aliphatic ester structures synthesized from N-modifed bis-2-hydroxyethylglycinamide (bicin). Protein models included an enzyme, lysozyme, and a receptor ligand, interferon-beta-1b, for preparation of linear or branched mono- and multi-PEGylated conjugates as inactive PEG-BCN3 prodrugs. The kinetics of protein release, both in plasma (in vitro) and in mice (in vivo), correlated with the number of PEG attachments, and the plasma half-lives of PEG release spanned a duration of hours to days within the therapeutically relevant window. Capillary electrophoresis, SDS-PAGE, mass determination, and enzymatic and antiviral activity determinations demonstrated regeneration of equivalent native proteins from the inactive PEG-BCN3 conjugates. Pharmacokinetic analysis of the PEGylated interferon-beta-1b administered subcutaneously in mice demonstrated an over 20-fold expansion of the area under the curve exposure of bioactive protein when compared to native protein.

Animals↗

PubMedDate not supplied

Structure-function engineering of interferon-beta-1b for improving stability, solubility, potency, immunogenicity, and pharmacokinetic properties by site-selective mono-PEGylation.

Recombinant interferon-beta-1b (IFN-beta-1b) is used clinically in the treatment of multiple sclerosis. In common with many biological ligands, IFN-beta-1b exhibits a relatively short serum half-life, and bioavailability may be further diminished by neutralizing antibodies. While PEGylation is an approach commonly employed to increase the blood residency time of protein therapeutics, there is a further requisite for molecular engineering approaches to also address the stability, solubility, aggregation, immunogenicity and in vivo exposure of therapeutic proteins. We investigated these five parameters of recombinant human IFN-beta-1b in over 20 site-selective mono-PEGylated or multi-PEGylated IFN-beta-1b bioconjugates. Primary amines were modified by single or multiple attachments of poly(ethylene glycol), either site-specifically at the N-terminus, or randomly on the 11 lysines. In two alternate approaches, site-directed mutagenesis was independently employed in the construction of designed IFN-beta-1b variants containing either a single free cysteine or lysine for site-specific PEGylation. Optimization of conjugate preparation with 12 kDa, 20 kDa, 30 kDa, and 40 kDa amine-selective PEG polymers was achieved, and a comparison of the structural and functional properties of the IFN-beta-1b proteins and their PEGylated counterparts was conducted. Peptide mapping and MALDI-TOF mass spectrometric analysis confirmed the attachment sites of the PEG polymer. Independent biochemical and bioactivity analyses, including antiviral and antiproliferation bioassays, circular dichroism, capillary electrophoresis, flow cytometric profiling, reversed phase and size exclusion HPLC, and immunoassays demonstrated that the functional activities of the designed IFN-beta-1b conjugates were maintained, while the formation of soluble or insoluble aggregates of IFN-beta-1b was ameliorated. Immunogenicity and pharmacokinetic studies of selected PEGylated IFN-beta-1b compounds in mice and rats demonstrated both diminished IgG responses, and over 100-fold expanded AUC exposure relative to the unmodified protein. The results demonstrate the capacity of this macromolecular engineering strategy to address both pharmacological and formulation challenges for a highly hydrophobic, aggregation-prone protein. The properties of a lead mono-PEGylated candidate, 40 kDa PEG2-IFN-beta-1b, were further investigated in formulation optimization and biological studies.

Amides↗

PubMedDate not supplied

Engineering an arginine catabolizing bioconjugate: Biochemical and pharmacological characterization of PEGylated derivatives of arginine deiminase from Mycoplasma arthritidis.

Arginine is an important metabolite in the normal function of several biological systems, and arginine deprivation has been investigated in animal models and human clinical trials for its effects on inhibition of tumor growth, angiogenesis, or nitric oxide synthesis. In order to design an optimal arginine-catabolizing enzyme bioconjugate, a novel recombinant arginine deiminase (ADI) from Mycoplasma arthritidis was prepared, and multi-PEGylated derivatives were examined for enzymatic and biochemical properties in vitro, as well as pharmacokinetic and pharmacodynamic behavior in rats and mice. ADI bioconjugates constructed with 12 kDa or 20 kDa monomethoxy-poly(ethylene glycol) polymers with linear succinimidyl carbonate linkers were investigated via intravenous, intramuscular, or subcutaneous administration in rodents. The selected PEG-ADI compounds have 22 +/- 2 PEG strands per protein dimer, providing an additional molecular mass of about 0.2-0.5 x 10(6) Da and prolonging the plasma mean residence time of the enzyme over 30-fold in mice. Prolonged plasma arginine deprivation was demonstrated with each injection route for these bioconjugates. Pharmacokinetic analysis employed parallel measurement of enzyme activity in bioassays and enzyme assays and demonstrated a correlation with the pharmacodynamic analysis of plasma arginine concentrations. Either ADI bioconjugate depressed plasma arginine to undetectable levels for 10 days when administered intravenously at 5 IU per mouse, while the subcutaneous and intramuscular routes exhibited only slightly reduced potency. Both bioconjugates exhibited potent growth inhibition of several cultured tumor lines that are deficient in the anabolic enzyme, argininosuccinate synthetase. Investigations of structure-activity optimization for PEGylated ADI compounds revealed a benefit to constraining the PEG size and number of attachments to both conserve catabolic activity and streamline manufacturing of the experimental therapeutics. Specifically, ADI with either 12 kDa or 20 kDa PEG attachments on 33% of the primary amines retained about 60% or 48% of enzyme activity, respectively; the Km and pH profiles were nearly unchanged; IC50 values were diminished by less than 30%; while stability studies demonstrated full retention of activity at 4 degrees C for 5 months. A comparison of the enzymatic properties of a second ADI from Pseudomonas putida illustrated the superior characteristics of the M. arthritidis ADI enzyme.

Amino Acid Sequence↗