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At least 1,081 records · Page 60Linked to original sources

PubMed2006

Every-12-hour administration of extended-release divalproex in patients with epilepsy: impact on plasma valproic acid concentrations.

Extended-release divalproex sodium (divalproex-ER) biopharmaceutics after every-12-hour (q12h) administration was compared with that of once-daily divalproex-ER and conventional divalproex given every 6 hours (q6h) in a multiple-dose (14-day), randomized, three-period crossover design study in 24 patients with epilepsy concomitantly receiving enzyme-inducing antiepileptic medication(s). Plasma valproic acid (VPA) minimum concentration (Cmin) for divalproex-ER q12h was higher than the once-daily divalproex-ER Cmin (P=0.043). Once-daily divalproex-ER Cmin values were not different from those for divalproex q6h, suggesting that adequate trough steady-state concentrations are maintained with once daily dosing, despite enzyme-inducing comedication. The degree of peak-trough fluctuation (DFL, calculated as (Cmax-Cmin)/Cavg) in VPA concentration was less with both q12h (35.2% less) and once-daily (16.9% less) divalproex-ER regimens compared with q6h divalproex (P0.024). The DFL for divalproex-ER dosed as a q12h regimen was 22% less than that for once-daily divalproex-ER (P=0.02). The DFL in VPA concentration with divalproex-ER can be minimized with once-daily administration and more so with q12h administration, compared with conventional enteric-coated divalproex taken q6h.

Adult↗

PubMed2005

Gas-inducible product gene expression in bioreactors.

Inducible transgene expression technologies are of unmatched potential for biopharmaceutical manufacturing of unstable, growth-impairing and cytotoxic proteins as well as conditional metabolic engineering to improve desired cell phenotypes. Currently available transgene dosing modalities which rely on physical parameters or small-molecule drugs for transgene fine-tuning compromise downstream processing and/or are difficult to implement technologically. The recently designed gas-inducible acetaldehyde-inducible regulation (AIR) technology takes advantage of gaseous acetaldehyde to modulate product gene expression levels. At regulation effective concentrations gaseous acetaldehyde is physiologically inert and approved as food additive by the Federal Drug Administration (FDA). During standard bioreactor operation, gaseous acetaldehyde could simply be administered using standard/existing gas supply tubing and eventually eliminated by stripping with inducer-free air. We have determined key parameters controlling acetaldehyde transfer in three types of bioreactors and designed a mass balance-based model for optimal product gene expression fine-tuning using gaseous acetaldehyde. Operating a standard stirred-tank bioreactor set-up at 10 L scale we have validated AIR technology using CHO-K1-derived serum-free suspension cultures transgenic for gas-inducible production of human interferon-beta (IFN-beta). Gaseous acetaldehyde-inducible IFN-beta production management was fully reversible while maintaining cell viability at over 95% during the entire process. Compatible with standard bioreactor design and downstream processing procedures AIR-based technology will foster novel opportunities for pilot and large-scale manufacturing of difficult-to-produce protein pharmaceuticals.

Acetaldehyde↗

PubMed2006

6-hydroxy-nicotine-inducible multilevel transgene control in mammalian cells.

The precise control of transgene expression is essential for biopharmaceutical manufacturing, gene therapy and tissue engineering. We have designed a novel conditional transcription technology, which enables reversible induction, repression and adjustment of desired transgene expression using the clinically inert 6-hydroxy-nicotine (6HNic). The 6-hydroxy-nicotine oxidase (6HNO) repressor (HdnoR), which manages nicotine metabolism in Arthrobacter nicotinovorans pAO1 by binding to a specific operator of the 6-hydroxy-nicotine oxidase (O(NIC)), was fused to the Krueppel-associated box protein of the human kox-1 gene (KRAB) to create a synthetic 6HNic-dependent transsilencer (NS) that controls chimeric mammalian promoters, which are assembled by cloning tandem O(NIC) operators 3' of a constitutive promoter. In the absence of 6HNic, NS binds to O(NIC) and silences the constitutive promoter, which otherwise drives high-level transgene expression when the NS-O(NIC) interaction stops in the presence of 6HNic. Generic NICE(ON) technology was compatible with a variety of constitutive viral and mammalian housekeeping promoters, each of which enabled specific induced, repressed, adjusted and reversible transgene expression profiles in Chinese hamster ovary (CHO-K1), baby hamster kidney (BHK-21) as well as in human fibrosarcoma (HT-1080) cells. NICE(ON) also proved successful in controlling multicistronic expression units for coordinated transcription of up to three transgenes and in the fine-tuning of transcription-translation networks, in which RNA polymerase II- and III-dependent promoters, engineered for 6HNic responsiveness, drove expression of siRNAs that triggered specific transgene knockdown. NICE(ON) represents a robust and versatile technology for the precise tuning of transgene expression in mammalian cells.

Animals↗

PubMed1996

A review of current clinical findings with fluvastatin.

Fluvastatin, the newest member of the class of 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors, is structurally different from the fungal metabolites (lovastatin, pravastatin, and simvastatin) and is wholly synthetic. Fluvastatin has a distinct biopharmaceutical profile, including a short systemic exposure time (half-life of 1.2 hours) and virtually no active circulating metabolites. Fluvastatin is targeted to the liver, where it is rapidly metabolized; 98% of fluvastatin is protein bound. Double-blind, placebo-controlled studies have demonstrated that fluvastatin at daily dosages of 20-40 mg produces significant decreases from baseline in low-density lipoprotein (LDL) cholesterol on the order of 22-31% in patients with severe primary hypercholesterolemia (mean baseline LDL cholesterol 227 mg/dL) and decreases of 19-25% in patients with familial hypercholesterolemia (mean baseline LDL cholesterol 270 mg/dL). Interim results of a titrate-to-goal, 20-week study in patients with moderate hypercholesterolemia (LDL cholesterol >= 160 mg/dL and triglycerides <= 350 mg/dL) demonstrate that fluvastatin, 20 mg/day, lowers LDL cholesterol by 21% within 6 weeks. Long-term results indicate that the lipid-lowering effects of fluvastatin are sustained for 96 weeks. Further, 1 study has shown that the combination of low-dose fluvastatin plus niacin decreased LDL cholesterol levels 40% without untoward adverse events, suggesting that this combination is effective and safe for patients needing intensive lipid-lowering therapy. Asymptomatic, reversible increases in hepatic transaminase levels occur in fluvastatin-treated patients at a frequency comparable to that reported for other HMG-CoA reductase inhibitors. The 20-30% reduction in LDL cholesterol required by the majority of patients with hypercholesterolemia can be achieved with fluvastatin at 20 or 40 mg/day as well as with the other available HMG-CoA reductase inhibitors at their most commonly prescribed doses. Fluvastatin, priced 40% lower than other statins, provides the most cost-effective means of safely achieving goal LDL cholesterol levels in these patients.

Fatty Acids, Monounsaturated↗

PubMed2001

Using densities of estimators to compare pharmacokinetic experiments.

Different designs of experiments are compared according to the shape, concentration, etc. of the densities of the least-squares estimator (conditional densities, marginal densities). In contrast with D'Argenio (J. Pharmacokinetics Biopharmaceutics 9(16) (1981) 739-756), where marginal densities have been obtained by simulations, we present here a faster procedure based on well-elaborated approximations of the densities. The stress is on the graphical presentation of the results.

Computer Graphics↗

PubMedDate not supplied

Quality and functionality of excipients.

The quality of medicines depends not only on the active principles and production processes, but also the performance of the excipients. The traditional concept of the excipient as any component other than the active substance has undergone a substantial evolution from an 'inert' and cheap vehicle to an essential constituent of the formulation. The rapid evolution of scientific, regulatory and economic factors, the introduction of delivery systems and the advance in biopharmaceutics have led to a new interest in the role and functionality of the excipients. More than one thousand raw materials are available from a multitude of sources and are used today in the pharmaceutical industry. Their chemical structures vary from small molecules to complex natural or synthetic polymeric mixtures. Excipients are now chosen to perform a variety of functions to guarantee the stability and bioavailability of the drug substance from the drug product and its manufacturability on a production scale. Beyond the dosage form necessities, excipients are required to perform important and specific technological functions, particularly in the case of solid dosage forms. As a consequence, their characterisation must go beyond the simple tests for identity, purity and strength as prescribed in general by the Pharmacopoeia monographs. With the exception of the Textbook of Pharmaceutical Excipients, not many reference sources describing the physical mechanical characteristics of the powders for a specific role are available. Full physical characterisation of solid materials is now made possible with the help of high resolution analytical techniques on the molecular, particulate and bulk levels. This systematic approach is necessary to guarantee the behaviour of the excipient during the formulation and production phases. Some examples have been chosen in this mini-review in an effort to highlight the emerging trends in the development of 'tailor-made' materials. Three main approaches are followed by the industry: physical or minor chemical manipulation of materials already known, combination of two or more marketed excipients in order to reduce unwanted defects and, finally, preparation of new chemical entities with huge investments for the toxicity studies. Excipient harmonisation, standardised functionality tests, preformulation data bases and expert systems will contribute to change the conventional trial-and-error formulation approach into a far more scientific and technological development.

Chemistry, Pharmaceutical↗

PubMed1982

Determination of tocainide in human plasma by gas chromatography with nitrogen-selective detection after Schiff base formation.

Tocainide is a primary amine with antiarrhythmic properties derived from lidocaine. For biopharmaceutical and pharmacokinetic purposes an assay was developed that made use of Schiff base formation with methyl isobutyl ketone and gas chromatography with nitrogen-selective detection. The derivatization procedure was performed at 85 C for 10 min, although a longer time at this temperature caused degradation of the product. Of several structural analogues the p-methyl one was the internal standard of choice. The amine was extracted from alkaline samples with dichloromethane and, after evaporation, reconstituted in methyl isobutyl ketone. From plasma the yields were lower than those from aqueous samples but the addition of hydroxylamine 30 min before the extraction process resulted in the same yields. Hydroxylamine probably acts as a competitor for carbonyl groups in the biological sample. In addition to the enhanced yields patients' samples extracted after hydroxylamine treatment were analysed with better precision. With nitrogen-selective detection 500 nmol/l in a 0.5-ml sample could be quantified, which is well below the therapeutic levels. The method compared favourably with a liquid chromatography assay.

Anti-Arrhythmia Agents↗

PubMed2001

Affinity-reversed-phase liquid chromatography assay to quantitate recombinant antibodies and antibody fragments in fermentation broth.

An automated dual-column liquid chromatography assay comprised of affinity and reversed-phase separations that quantifies the majority of antibody-related protein species found in crude cell extracts of recombinant origin is described. Although potentially applicable to any antibody preparation, we here use samples of anti-CD18 (Fab'2LZ) and a full-length antibody, anti-tissue factor (anti-TF), from various stages throughout a biopharmaceutical production process to describe the assay details. The targeted proteins were captured on an affinity column containing an anti-light-chain (kappa) Fab antibody (AME5) immobilized on controlled pore glass. The affinity column was placed in-line with a reversed-phase column and the captured components were transferred by elution with dilute acid and subsequently resolved by eluting the reversed-phase column with a shallow acetonitrile gradient. Characterization of the resolved components showed that most antibody fragment preparations contained a light-chain fragment, free light chain, light-chain dimer and multiple forms of Fab'. Analysis of full-length antibody preparations also resolved these fragments as well as a completely assembled form. Co-eluting with the full-length antibody were high-molecular-mass variants that were missing one or both light chains. Resolved components were quantified by comparison with peak areas of similarly treated standards. By comparing the two-dimensional polyacrylamide gel electrophoresis patterns of an Escherichia coli blank run, a production run and the material affinity captured (AME5) from a production run, it was determined that the AME5 antibody captured isoforms of light chain, light chain covalently attached to heavy chain, and truncated light chain isoforms. These forms comprise the bulk of the soluble product-related fragments found in E. coli cell extracts of recombinantly produced antibody fragments.

Antibodies↗

PubMed2002

Initial purification of recombinant botulinum neurotoxin fragments for pharmaceutical production using hydrophobic charge induction chromatography.

Initial purification of two serotypic variants of recombinant botulinum neurotoxin toxin heavy chain fragment [rBoNT(Hc)], produced intracellularly in the yeast Pichia pastoris, using hydrophobic charge induction chromatography (HCIC) is reported. HCIC employs a matrix containing a weakly ionizable ligand that binds proteins through hydrophobic interactions at neutral pH and elutes the proteins by charge repulsion at acidic pH. HCIC optimization led to different purification conditions for each of the proteins even though they have 58% sequence similarity. The HCIC resin has a higher affinity for the fragment of serotype A than that of serotype B. The 10% dynamic breakthrough capacity for the serotype A fragment is >12.5 mg per ml of resin and is approximately 3.5 mg or the serotype B fragment per ml of resin. Stable elution conditions are also different for the two serotypes. The serotype A fragment is unstable when citrate is used to elute the product. However the serotype B fragment is stable when eluted with citrate buffer, and it is further purified by a overnight precipitation caused by the citrate buffer. This paper reports the development strategy, dynamic capacity breakthrough curves, resin and separation reproducibility, and preliminary scale-up data. The summation of the data demonstrates that HCIC is a scaleable process step for biopharmaceutical production of rBoNT(Hc) proteins.

Amino Acid Sequence↗

PubMed1996

Quality assurance after process changes of the production of a therapeutic antibody.

Process development for the production of a therapeutic humanised antibody is a very complex operation. It involves recombinant genetics, verification of a strong expression system, gene amplification, characterisation of a stable host cell expression system, optimisation and design of the mammalian cell culture fermentation system and development of an efficient recovery process resulting in high yields and product quality. Rapid progress in the field and the wish of some pharmaceutical companies for outsourcing their production are the driving forces for process changes relatively late in the development phase. This literature survey is aimed at identifying the limits of acceptable process changes in up scaling of the fermentation and down stream processing of biopharmaceuticals and defining the demand in production validation to prove product equivalency and identity of the isolated, purified therapeutic antibody.

Animals↗

PubMed2001

Karl Heinrich Slotta (1895-1987) biochemist: snakes, pregnancy and coffee.

In 1923 Karl H. Slotta obtained his PhD in chemistry from the University of Breslau, Germany, where he continued to work. At the instigation of the gynaecologist Ludwig Fraenkel, Slotta made the first isolation of progesterone in 1933. In 1934 he proposed the correct structural formula. Slotta was appointed professor of chemistry in 1935, but with the oppression of the Nazi regime mounting, he soon left Germany with his family to take a post at the Instituto Butantan, Brazil. Initially he worked on the chemistry of coffee. In 1938 Slotta and his brother-in-law Heinz Fraenkel-Conrat isolated crotoxin from Crotalus durissus terrificus venom, the first snake toxin to be obtained in crystalline form. They had evidence to suggest that the toxicity of crotoxin was due to a phospholipolytic action on nerve lipids. In 1938 Slotta's department was closed; he subsequently cofounded a biopharmaceutical company. In 1956 Slotta was appointed research professor of biochemistry at the University of Miami, USA. Slotta purified the most basic polypeptide from Naja naja venom, known as direct lytic factor, and with James Vick identified this as cardiotoxin. Karl H. Slotta will be remembered not only for his skill as a biochemist but also for his indomitable and cheerful spirit.

Biochemistry↗

PubMed2002

'Biogenerics': the off-patent biotech products.

The first patents of biopharmaceuticals derived from recombinant DNA will expire shortly, which raises the possibility of marketing generic products ('biogenerics') with limited documentation, similar to that which occurs with conventional pharmaceuticals. We propose the term off-patent biotechnological products (OPBPs) as an alternative to biogenerics when describing such products. It is questionable whether the majority of OPBPs can be classified as similar to the innovator products, considering the size and complexity of the molecules and the many factors that influence biological activity. There are three classes of OPBPs, each of which needs to meet different regulatory demands when seeking marketing authorization.

Biotechnology↗

PubMed2002

A highly sensitive chemiluminescent reverse transcriptase assay for human immunodeficiency virus.

A simple and highly sensitive reverse transcriptase (RT) assay was developed by combining a previously reported non-radioisotopic RT assay with the use of a template-primer-immobilized microplate, an enzyme capture protocol, product digestion and a chemiluminescent substrate. The assay was able to detect directly the RT activity in serum samples, plasma and cell culture medium without the need for concentration and extraction of the enzyme. The assay was able to detect RT activity equivalent to 100 virions/ml of HIV-1. These results suggest that this highly sensitive chemiluminescent RT assay can be used not only for virological investigation but also for routine screening of biopharmaceuticals.

Cells, Cultured↗

PubMed2003

Comparison of electron microscopic techniques for enumeration of endogenous retrovirus in mouse and Chinese hamster cell lines used for production of biologics.

Murine myeloma and Chinese hamster ovary cells are used widely in the manufacture of recombinant proteins for biopharmaceuticals. However, rodent cell lines express endogenous retrovirus, which necessitates appropriate design of purification processes to remove virus in excess of the calculated maximum retroviral load. Currently, electron microscopy is the method of choice for determination of retroviral titre in bulk harvest. In this study we compared three electron microscopy techniques to determine retroviral titre in bulk harvest. These were direct negative stain, negative stain after sucrose-density purification and thin section electron microscopy of pelleted supernatant. The study demonstrated that the level of C-type retrovirus associated with cells was predictive of the viral load in cell culture supernatants. The most accurate method for quantifying viral load was direct counting, followed by thin section of pelleted supernatant and negative stain after sucrose concentration. The most practical method was thin section of resuspended pelleted supernatant, which gave improved detection limits.

Animals↗

PubMed2003

Avian transgenesis: progress towards the promise.

The hen has long held promise as a low cost, high-yield bioreactor for the production of human biopharmaceuticals in egg whites. A typical egg white contains 3.5-4.0 grams of protein, more than half of which comes from a single gene (ovalbumin). Harnessing the power of the gene to express a recombinant protein could yield up to a gram or more of the protein in the naturally sterile egg. Accordingly, a major effort has been underway for more than a decade to develop robust methods for modification of the chicken genome. This effort intensified in the mid-1990s when several avian transgenic companies entered the scene. Progress has been made in that time but much remains to be done.

Animals↗

PubMed2002

Optimizing scale-up fermentation processes.

There are many aims associated with the optimization of fermentation processes. Optimization is expected to increase the yield of the final product but the process must be compliant with good manufacturing practices, the available equipment and the expected final scale of operation. Dealing with genetically modified microorganisms that overproduce recombinant protein has the advantage that the vast majority of the processes use only three different species, namely Escherichia coli, Saccharomyces cerevisiae and Pichia pastoris. Standard processes for each organism are described in textbooks and serve as a basis for the development of a tailored process. This article outlines the general philosophy that we have devised to ensure an efficient approach of scaling up fermentation processes for biopharmaceutical purposes, in a multidisciplinary environment.

Biomass↗

PubMed2002

Preparative protein refolding.

The rapid provision of purified native protein underpins both structural biology and the development of new biopharmaceuticals. The dominance of Escherichia coli as a cellular biofactory depends on technology for solubilizing and refolding proteins that are expressed as insoluble inclusion bodies. Such technology must be scale invariant, easily automated, generic for a broad range of similar proteins and economical. Refolding methods relying on denaturant dilution and column-based approaches meet these criteria. Recent developments, particularly in column-based methods, promise to extend the range of proteins that can be refolded successfully. Developments in preparing denatured purified protein and in the analysis of protein refolding products promise to remove bottlenecks in the overall process. Combined, these developments promise to facilitate the rapid and automated determination of appropriate refolding conditions and to simplify scale-up.

Chromatography, Affinity↗

PubMed1997

Some aspects of bioassay methods in natural-product research aimed at drug lead discovery.

The objective of natural-product research aimed at drug lead discovery is to find unique bioactive molecules with improved biopharmaceutical properties or new modes of action. In order to discover such bioactive substances, different bioassays are used for detection, for guidance of the chemical isolation procedures and for preliminary biological characterization of new compounds. This article gives a brief update on current biological activities and discusses some essential, but occasionally neglected, aspects of bioassay methods. Some future perspectives on the use of bioassay methods in the drug-discovery process are also discussed.

Biological Assay↗