Improving Viscosity and Stability of a Highly Concentrated Monoclonal Antibody Solution with Concentrated Proline

Purpose

To explain the effects of the osmolyte proline on the protein-protein interactions (PPI), viscosity and stability of highly concentrated antibody solutions in contrast to other neutral osmolytes.

Methods

The viscosity of ~225 mg/mL mAb solutions was measured with proline, glycine and trehalose as a function of pH and co-solute concentration up to 1.3 M. The stability was assessed via turbidity as well as size exclusion chromatography after 4 weeks storage at 40°C. The PPI strength was assessed qualitatively via the high concentration diffusion rate by dynamic light scattering.

Results

Increasing proline significantly reduced the mAb viscosity and increased the colloidal stability at pH 6, but not at pH 5 further from the mAb pI. In contrast, glycine and trehalose did not improve the viscosity nor stability. The normalized diffusion coefficient at high concentration, which is inversely proportional to the attractive PPI strength, increased with proline concentration but decreased with increasing glycine.

Conclusions

Proline demonstrated greater efficacy for improving mAb viscosity and stability in contrast to glycine and trehalose due to its amphipathic structure and partial charge on the pyrrolidine side chain. These properties likely allow proline to screen the attractive electrostatic and hydrophobic interactions that promote self-association and high viscosities. Binary proline-histidine formulations also demonstrated greater viscosity reduction effects than histidine alone at the same total co-solute concentration, while maintaining a lower total solution osmolarity.

     

Effects of Excipients on the Chemical and Physical Stability of Glucagon during Freeze-Drying and Storage in Dried Formulations

Purpose

To evaluate the effects of several buffers and excipients on the stability of glucagon during freeze-drying and storage as dried powder formulations.

Methods

The chemical and physical stability of glucagon in freeze-dried solid formulations was evaluated by a variety of techniques including mass spectrometry (MS), reversed phase HPLC (RP-HPLC), size exclusion HPLC (SE-HPLC), infrared (IR) spectroscopy, differential scanning calorimetry (DSC) and turbidity.

Results

Similar to protein drugs, maintaining the solid amorphous phase by incorporating carbohydrates as well as addition of surfactant protected lyophilized glucagon from degradation during long-term storage. However, different from proteins, maintaining/stabilizing the secondary structure of glucagon was not a prerequisite for its stability.

Conclusions

The formulation lessons learned from studies of freeze-dried formulations of proteins can be applied successfully to development of stable formulations of glucagon. However, peptides may behave differently than proteins due to their small molecule size and less ordered structure.     

Effect of pH and Excipients on Structure, Dynamics, and Long-Term Stability of a Model IgG1 Monoclonal Antibody upon Freeze-Drying

Purpose

To investigate the mechanism of IgG1 mAb stabilization after freeze-drying and the interdependence of protein structural preservation in the solid state, glassy state dynamics and long-term storage stability under different formulation conditions.

Methods

IgG1 mAb was formulated with mannitol at pH 3.0, 5.0, and 7.0 in the presence and absence of sucrose and stability was monitored over 1 year at different temperatures. Physical and covalent degradation of lyophilized formulation was monitored using SEC, CEX, and light obscuration technique. Secondary and tertiary structure of the protein in the solid state was characterized using FTIR and fluorescence spectroscopy respectively. Raman spectroscopy was also used to monitor changes in secondary and tertiary structure, while SS-NMR ¹H relaxation was used to monitor glassy state dynamics.

Results

IgG1 mAb underwent significant secondary structural perturbations at pH 3.0 and conditions without sucrose, while pH 5.0 condition with sucrose showed the least structural change over time. The structural changes correlated with long-term stability with respect to protein aggregate formation and SbVP counts. SS-NMR data showed reduced relaxation time at conditions that were more stable.

Conclusions

Native state protein structural preservation and optimal solid-state dynamics correlate with improved long-term stability of the mAb in the different lyophilized formulations.     

High Concentration Formulation Studies of an IgG2 Antibody Using Small Angle X-ray Scattering

Purpose

Concentrated protein formulations are strongly influenced by protein-protein interactions. These can be probed at low protein concentration by e.g. virial coefficients. It was recently suggested that interactions are attractive at short distances and repulsive at longer distances. Measurements at low concentrations mainly sample longer distances, hence may not predict high concentration behavior. Here we demonstrate that small angle X-ray scattering (SAXS) measurements simultaneously collect information on interactions at short and long distances.

Methods

IgG2 antibody samples at concentrations up to 122?mg/ml are analyzed using SAXS and compared to Circular Dichroism (CD), Fluorescence, Size Exclusion Chromatography (SEC) and Dynamic Light Scattering (DLS) analysis.

Results

DLS and SEC analyses reveal attraction between antibodies at high concentrations. SAXS data analysis provides an elaborate understanding and shows both attractive and repulsive forces. The protein-protein interactions are strongly affected by excipients. No change in the solution state of IgG2 is observed at pH 4?C8, while samples at pH 3 exhibit heavy oligomerization. The solution conformation of the examined IgG2 derived from SAXS data is a T-shape.

Conclusion

SAXS analysis resolves simultaneous attractive and repulsive interactions, and details the effect of excipients on the interactions, while providing three-dimensional structural information from low-concentration samples.     

The Degradation of Polysorbates 20 and 80 and its Potential Impact on the Stability of Biotherapeutics

Purpose

To study the potential impact of the degradation of Polysorbates (PS) 20 and 80 on the stability of therapeutic proteins in parenteral formulations.

Method

First, degradation products of PS20 and 80 were identified. Subsequently, the effect of degraded polysorbate on physical characteristics and long-term stability of protein formulations was assessed. Further, the impact of polysorbate degradation on protein stability was evaluated via shaking stress studies on formulations spiked with artificially degraded polysorbate or degradants like fatty acids. Additionally, aged formulations with reduced polysorbate content were shaken.

Results

The degradation of polysorbate leads to a buildup of various molecules, some of which are poorly soluble, including fatty acids and polyoxyethylene (POE) esters of fatty acids. Spiking studies showed that the insoluble degradants could potentially impact protein stability and that the presence of sufficient intact polysorbate was crucial to prevent this. End-of-shelf-life shaking of protein formulations showed that the stability of various monoclonal antibodies was, however, not affected.

Conclusions

Although some degradants can potentially influence the stability of the protein (as discerned from spiking studies), degradation of polysorbates did not impact the stability of the different proteins tested in pharmaceutically relevant temperature and storage conditions.     

Stability and Release Kinetics of an Advanced Gliclazide-Cholic Acid Formulation: The Use of Artificial-Cell Microencapsulation in Slow Release Targeted Oral Delivery of Antidiabetics

Introduction

In previous studies carried out in our laboratory, a bile acid (BA) formulation exerted a hypoglycaemic effect in a rat model of type-1 diabetes (T1D). When the antidiabetic drug gliclazide (G) was added to the bile acid, it augmented the hypoglycaemic effect. In a recent study, we designed a new formulation of gliclazide-cholic acid (G-CA), with good structural properties, excipient compatibility and exhibits pseudoplastic-thixotropic characteristics. The aim of this study is to test the slow release and pH-controlled properties of this new formulation. The aim is also to examine the effect of CA on G release kinetics at various pH values and different temperatures.

Method

Microencapsulation was carried out using our Buchi-based microencapsulating system developed in our laboratory. Using sodium alginate (SA) polymer, both formulations were prepared: G-SA (control) and G-CA-SA (test) at a constant ratio (1:3:30), respectively. Microcapsules were examined for efficiency, size, release kinetics, stability and swelling studies at pH 1.5, pH 3, pH 7.4 and pH 7.8 and temperatures of 20 and 30 °C.

Results

The new formulation is further optimised by the addition of CA. CA reduced microcapsule swelling of the microcapsules at pH 7.8 and pH 3 at 30 °C and pH 3 at 20 °C, and, even though microcapsule size remains similar after CA addition, percent G release was enhanced at high pH values (pH 7.4 and pH 7.8, p?<?0.01).

Conclusion

The new formulation exhibits colon-targeted delivery and the addition of CA prolonged G release suggesting its suitability for the sustained and targeted delivery of G and CA to the lower intestine.     

Novel Topical Ophthalmic Formulations for Management of Glaucoma

Purpose

Preparation of topical ophthalmic formulations containing brimonidine-loaded nanoparticles prepared from various biodegradable polymers—PCL, PLA and PLGA—for sustained release of brimonidine as a once daily regimen for management of glaucoma.

Methods

Nanoparticles were prepared using spontaneous emulsification solvent diffusion method then characterized regarding their particle size, zeta potential, morphology and drug contents. Brimonidine-loaded nanoparticles were incorporated into eye drops, temperature-triggered in situ gelling system and preformed gel and characterized regarding their pH, viscosity, uniformity of drug contents, in vitro release study, in vitro cytotoxicity and in vivo intraocular pressure (IOP) lowering effects.

Results

The results of optimized brimonidine-loaded PCL-, PLGA- and PLA-NPs respectively, are: particle sizes of 117.33?±?4.58 nm, 125.67?±?5.15 nm and 131.67?±?3.79 nm; zeta potentials of ?18.5?±?2.87 mV, ?21.82?±?2.7 mV and ?28.11?±?2.21 mV; and encapsulation efficiencies of 77.97?±?1.38%, 68.65?±?3.35% and 73.52?±?2.92%. TEM analyses revealed that all NPs have spherical shapes with dense core and distinct coat. In vitro release data showed a sustained release without any burst effect with Higuchi non-Fickian diffusion mechanism. Cytotoxicity studies revealed that all formulations are non-toxic. Also all formulations possessed a sustained IOP lowering effect compared to Alphagan® P eye drops.

Conclusions

Our formulations showed prolonged management of glaucoma that should meet with better patient compliance as a once-daily formulation.     

Rapid Intradermal Delivery of Liquid Formulations Using a Hollow Microstructured Array

Purpose

The purpose of this work is to demonstrate rapid intradermal delivery of up to 1.5 mL of formulation using a hollow microneedle delivery device designed for self-application.

Methods

3M??s hollow Microstructured Transdermal System (hMTS) was applied to domestic swine to demonstrate delivery of a variety of formulations including small molecule salts and proteins. Blood samples were collected after delivery and analyzed via HPLC or ELISA to provide a PK profile for the delivered drug. Site evaluations were conducted post delivery to determine skin tolerability.

Results

Up to 1.5 mL of formulation was infused into swine at a max rate of approximately 0.25 mL/min. A red blotch, the size of the hMTS array, was observed immediately after patch removal, but had faded so as to be almost indistinguishable 10 min post-patch removal. One-mL deliveries of commercial formulations of naloxone hydrochloride and human growth hormone and a formulation of equine anti-tetanus toxin were completed in swine. With few notable differences, the resulting PK profiles were similar to those achieved following subcutaneous injection of these formulations.

Conclusions

3M??s hMTS can provide rapid, intradermal delivery of 300?C1,500 µL of liquid formulations of small molecules salts and proteins, compounds not typically compatible with passive transdermal delivery.     

Mapping Ion-Induced Mesophasic Transformation in Lyotropic In Situ Gelling System and its Correlation with Pharmaceutical Performance

Purpose

To investigate influence of ion induced mesophasic transformation on pharmaceutical performance of in situ gelling system consisting of glyceryl monooleate.

Methods

The prepared system showed mesophasic transformation during its conversion from sol to gel upon controlled hydration. The process of mesophasic transformation was studied by SAXS, DSC, rheology and plane polarized light microscopy. Further the influence of additives i.e. naproxen salts (sodium and potassium) and naproxen (base) on the process of mesophasic transformation was also elucidated.

Results

It was observed that addition of salt form of naproxen transformed W/O emulsions into cubic mesophase whereas addition of base form of naproxen formed reverse hexagonal (H_II) phase upon controlled hydration. The cubic mesophase formed by naproxen salts retarded the drug release for initial 3 h whereas H_II phase showed sustained drug release characteristics for naproxen base following Higuchi drug release kinetics.

Conclusion

The current work suggests that formulations with tailor made pharmaceutical performance can be developed by selecting proper additives in the system so as to obtain the desired mesophase ‘on demand’ thereby controlling drug release characteristics.

Bicontinuous Cubic Liquid Crystalline Nanoparticles for Oral Delivery of Doxorubicin: Implications on Bioavailability,Therapeutic Efficacy,and Cardiotoxicity

Purpose

The present study explores the potential of bicontinous cubic liquid crystalline nanoparticles (LCNPs) for improving therapeutic potential of doxorubicin.

Methods

Phytantriol based Dox-LCNPs were prepared using hydrotrope method, optimized for various formulation components, process variables and lyophilized. Structural elucidation of the reconstituted formulation was performed using HR-TEM and SAXS analysis. The developed formulation was subjected to exhaustive cell culture experiments for delivery potential (Caco-2 cells) and efficacy (MCF-7 cells). Finally, in vivo pharmacokinetics, pharmacodynamic studies in DMBA induced breast cancer model and cardiotoxicity were also evaluated.

Results

The reconstituted formulation exhibited Pn3m type cubic structure, evident by SAXS and posed stability in simulated gastrointestinal fluids and at accelerated stability conditions for 6 months. Dox-LCNPs revealed significantly higher cell cytotoxicity (16.23-fold) against MCF-7 cell lines as compared to free drug owing to its preferential localization in the vicinity of nucleus. Furthermore, Caco-2 cell experiments revealed formation of reversible “virtual pathways” in the cell membrane for Dox-LCNPs and hence posed significantly higher relative oral bioavailability (17.74-fold). Subsequently, Single dose of Dox-LCNPs (per oral) led to significant reduction in % tumor burden (~42%) as compared that of ~31% observed in case of Adriamycin® (i.v.) when evaluated in DMBA induced breast cancer model. Moreover, Dox induced cardiotoxicity was also found to be significantly lower in case of Dox-LCNPs as compared to clinical formulations (Adriamycin® and Lipodox®).

Conclusion

Incorporation of Dox in the novel LCNPs demonstrated improved antitumor efficacy and safety profile and can be a viable option for oral chemotherapy.     

Beyond Glass Transitions: Studying the Highly Viscous and Elastic Behavior of Frozen Protein Formulations Using Low Temperature Rheology and Its Potential Implications on Protein Stability

Purpose

A novel application of oscillatory shear rheology was used to directly monitor global phase behavior of protein formulations in the frozen state and study its correlation with physical instability of frozen protein formulations.

Methods

Oscillatory rheology was used to measure changes in rheological parameters and to identify mechanical softening temperature (Ts*) and related properties of an IgG2 mAb formulation. Rheological measurements were compared to DSC/MDSC. Physical stability of IgG2 formulations was monitored by SE-HPLC.

Results

Rheological parameters and Ts* of an IgG2 formulation were sensitive to physical/morphological phase changes during freezing and thawing. Ts* of the frozen formulation was a function of concentration of protein and excipient. Complex modulus, G*, and phase angle, δ, for IgG2 at 70 mg/mL in a sucrose-containing formulation showed the system was not completely frozen at ?10°C, which correlated to stability data consistent with ice-induced protein aggregation.

Conclusions

We report the first application of oscillatory shear rheology to study phase behavior of IgG2 in a sucrose-containing formulation and its correspondence with physical stability not explained by glass transition (Tg’). We provide a mechanism and data suggesting that protein instability occurs at the ice/water interface.     

Stabilization of Live Attenuated Influenza Vaccines by Freeze Drying,Spray Drying,and Foam Drying

Purpose

The goal of this research is to develop stable formulations for live attenuated influenza vaccines (LAIV) by employing the drying methods freeze drying, spray drying, and foam drying.

Methods

Formulated live attenuated Type-A H1N1 and B-strain influenza vaccines with a variety of excipient combinations were dried using one of the three drying methods. Process and storage stability at 4, 25 and 37°C of the LAIV in these formulations was monitored using a TCID₅₀ potency assay. Their immunogenicity was also evaluated in a ferret model.

Results

The thermal stability of H1N1 vaccine was significantly enhanced through application of unique formulation combinations and drying processes. Foam dried formulations were as much as an order of magnitude more stable than either spray dried or freeze dried formulations, while exhibiting low process loss and full retention of immunogenicity. Based on long-term stability data, foam dried formulations exhibited a shelf life at 4, 25 and 37°C of >2, 1.5 years and 4.5 months, respectively. Foam dried LAIV Type-B manufactured using the same formulation and process parameters as H1N1 were imparted with a similar level of stability.

Conclusion

Foam drying processing methods with appropriate selection of formulation components can produce an order of magnitude improvement in LAIV stability over other drying methods.

     

Paliperidone-Loaded Mucoadhesive Microemulsion in Treatment of Schizophrenia: Formulation Consideration

Purpose

This paper describes formulation considerations and in vitro evaluation of a microemulsion drug delivery system designed for intranasal administration of Paliperidone.

Methods

Drug-loaded microemulsions were successfully prepared by a water titration. Prepared formulations were subjected to physicochemical characterization, and evaluated for in vitro diffusion, nasal cilio toxicity, and in vitro mucoadhesion.

Results

The microemulsion, containing 4 % oleic acid, 30 % surfactant mixture of [Labrasol/Cremophor RH 40 (1:1)]/[Transcutol P] (3:1) and 66 % (wt/wt) aqueous phase, that displayed a 99.93 % optical transparency, globule sizes of 20.01?±?1.28 nm, and a polydispersity index of 0.117?±?0.034 was selected for the incorporation of polyelectrolytic polymer (polycarbophil) as the mucoadhesive component. The mucoadhesive microemulsion formulation of Paliperidone that contains 0.5 % by weight of polycarbophil displayed higher in vitro mucoadhesive potential (18.0?±?2.5 min) and diffusion coefficient (3.83?×?10^?6?±?0.019?×?10^?6) than microemulsion. Also, they were found to be free from nasal ciliotoxicity and had stability for 6 months.

Conclusion

The in vitro studies demonstrated the potential of developing mucoadhesive microemulsion formulation for intranasal delivery of Paliperidone.     

Effects of Ionic Strength and Sugars on the Aggregation Propensity of Monoclonal Antibodies: Influence of Colloidal and Conformational Stabilities

Purpose

To develop a general strategy for optimizing monoclonal antibody (MAb) formulations.

Methods

Colloidal stabilities of four representative MAbs solutions were assessed based on the second virial coefficient (B ₂) at 20°C and 40°C, and net charges at different NaCl concentrations, and/or in the presence of sugars. Conformational stabilities were evaluated from the unfolding temperatures. The aggregation propensities were determined at 40°C and after freeze–thawing. The electrostatic potential of antibody surfaces was simulated for the development of rational formulations.

Results

Similar B ₂ values were obtained at 20°C and 40°C, implying little dependence on temperature. B ₂ correlated quantitatively with aggregation propensities at 40°C. The net charge partly correlated with colloidal stability. Salts stabilized or destabilized MAbs, depending on repulsive or attractive interactions. Sugars improved the aggregation propensity under freeze–thaw stress through improved conformational stability. Uneven and even distributions of potential surfaces were attributed to attractive and strong repulsive electrostatic interactions.

Conclusions

Assessment of colloidal stability at the lowest ionic strength is particularly effective for the development of formulations. If necessary, salts are added to enhance the colloidal stability. Sugars further improved aggregation propensities by enhancing conformational stability. These behaviors are rationally predictable according to the surface potentials of MAbs.     

Protected Graft Copolymer Excipient Leads to a Higher Acute Maximum Tolerated Dose and Extends Residence Time of Vasoactive Intestinal Peptide Significantly Better than Sterically Stabilized Micelles

Purpose

To determine and compare pharmacokinetics and toxicity of two nanoformulations of Vasoactive Intestinal Peptide (VIP).

Methods

VIP was formulated using a micellar (Sterically Stabilized Micelles, SSM) and a polymer-based (Protected Graft Copolymer, PGC) nanocarrier at various loading percentages. VIP binding to the nanocarriers, pharmacokinetics, blood pressure, blood chemistry, and acute maximum tolerated dose (MTD) of the formulations after injection into BALB/c mice were determined.

Results

Both formulations significantly extend in vivo residence time compared to unformulated VIP. Formulation toxicity is dependent on loading percentage, showing major differences between the two carrier types. Both formulations increase in vivo potency of unformulated VIP and show acute MTDs at least 140 times lower than unformulated VIP, but still at least 100 times higher than the anticipated highest human dose, 1–5 μg/kg. These nanocarriers prevented a significant drop in arterial blood pressure compared to unformulated VIP.

Conclusions

While both carriers enhance in vivo residence time compared to unformulated VIP and reduce the drop in blood pressure immediately after injection, PGC is the excipient of choice to extend residence time and improve the safety of potent therapeutic peptides such as VIP.

Stabilization of HAC1 Influenza Vaccine by Spray Drying: Formulation Development and Process Scale-Up

Purpose

Stable vaccines with long shelf lives and reduced dependency on the cold chain are ideal for stockpiling and rapid deployment during public emergencies, including pandemics. Spray drying is a low-cost process that has potential to produce vaccines stable at a wide range of temperatures. Our aim was to develop a stable formulation of a recombinant H1N1 influenza hemagglutinin vaccine candidate and take it to pilot-scale spray-drying production.

Methods

Eight formulations containing different excipients were produced and assayed for antigen stability, powder characteristics, and immunogenicity after storage at a range of temperatures, resulting in the identification of four promising candidates. A pilot-scale spray-drying process was then developed for further testing of one formulation.

Results

The pilot-scale process was used to reproducibly manufacture three batches of the selected formulation with yields >90%. All batches had stable physical properties and in vitro potency for 6 months at temperatures from ?20°C to +50°C. Formulations stored for 3 months elicited immunogenic responses in mice equivalent to a frozen lot of bulk vaccine used as a stability control.

Conclusions

This study demonstrates the feasibility of stabilizing subunit vaccines using a spray-drying process and the suitability of the process for manufacturing a candidate product.

     

Dipole-Dipole Interaction in Antibody Solutions: Correlation with Viscosity Behavior at High Concentration

Purpose

The purpose of this study was to investigate the contribution of the dipole moment to overall protein-protein interactions and viscosity of a monoclonal antibody MAb1.

Methods

The dipole moment of MAb1 was measured at various solution pH conditions using dielectric relaxation spectroscopy.

Results

The dipole moment for MAb1 was highest at pH 6.5, and the pH dependent change in molecular dipole correlated fairly well with previously observed trends of viscosity and storage modulus versus pH. Moreover, the magnitude of the dielectric increment at pH 6.5 and 7.0 showed strong concentration dependence, indicating the presence of relatively strong dipole-dipole interactions at these pHs. To test if the cluster of charged residues present in the Fab contributes to the mean dipole moment observed for MAb1, additional mutants involving charge mutations in the CDR were investigated. In contrast to MAb1, all of the other MAbs showed significantly reduced pH and concentration dependence of the measured dipole moments and dielectric increments, respectively.

Conclusions

The solution pH dependent measured dipole moments of MAb1 appears to be in line with the observed intermolecular interactions and viscosity behavior suggesting that dipole-dipole interaction plays an important role in governing the high concentration solution behavior of this MAb.     

Ultrasonication as a Potential Tool to Predict Solute Crystallization in Freeze-Concentrates

Purpose

We hypothesize that ultrasonication can accelerate solute crystallization in freeze-concentrates. Our objective is to demonstrate ultrasonication as a potential predictive tool for evaluating physical stability of excipients in frozen solutions.

Methods

The crystallization tendencies of lyoprotectants (trehalose, sucrose), carboxylic acid buffers (citric, tartaric, malic, and acetic) and an amino acid buffer (histidine HCl) were studied. Aqueous solutions of buffers, lyoprotectants and mixtures of the two were cooled from room temperature to ?20°C and sonicated to induce solute crystallization. The crystallized phases were identified by X-ray diffractometry (laboratory or synchrotron source).

Results

Sonication accelerated crystallization of trehalose dihydrate in frozen trehalose solutions. Sonication also enhanced solute crystallization in tartaric (200 mM; pH 5), citric (200 mM pH 4) and malic (200 mM; pH 4) acid buffers. At lower buffer concentrations, longer annealing times following sonication were required to facilitate solute crystallization. The time for crystallization of histidine HCl progressively increased as a function of sucrose concentration. The insonation period required to effect crystallization also increased with sucrose concentration.

Conclusions

Sonication can substantially accelerate solute crystallization in the freeze-concentrate. Ultrasonication may be useful in assessing the crystallization tendency of formulation constituents used in long term frozen storage and freeze-drying.     

Aggregation and Chemical Modification of Monoclonal Antibodies under Upstream Processing Conditions

Purpose

To investigate antibody stability and formation of modified species under upstream processing conditions.

Methods

The stability of 11 purified monoclonal human IgG1 and IgG4 antibodies, including an IgG1-based bispecific CrossMab, was compared in downscale mixing stress models. One of these molecules was further evaluated in realistic bioreactor stress models and in cell culture fermentations. Analytical techniques include size exclusion chromatography (SEC), turbidity measurements, cation exchange chromatography (cIEX), dynamic light scattering (DLS) and differential scanning calorimetry (DSC).

Results

Sensitivity in downscale stress models varies among antibodies and results in formation of high molecular weight (HMW) aggregates. Stability is increased in cell culture medium and in bioreactors. Media components stabilizing the proteins were identified. Extensive chemical modifications were detected both in stress models as well as during production of antibodies in cell culture fermentations.

Conclusions

Protective compounds must be present in chemically defined fermentation media in order to stabilize antibodies against the formation of HMW aggregates. An increase in chemical modifications is detectable in bioreactor stress models and over the course of cell culture fermentations; this increase is dependent on the expression rate, pH, temperature and fermentation time. Consequently, product heterogeneity increases during upstream processing, and this compromises the product quality.     

The CRF1 receptor antagonist SSR125543 prevents stress-induced cognitive deficit associated with hippocampal dysfunction: Comparison with paroxetine and d-cycloserine

Rationale

The selective CRF₁ (corticotropin releasing factor type 1) receptor antagonist SSR125543 has been previously shown to attenuate the long-term cognitive deficit produced by traumatic stress exposure. Memory disturbances described in post-traumatic stress disorder (PTSD) patients are believed to be associated with changes in neuronal activity, in particular at the level of the hippocampus.

Objectives

The present study aims at investigating whether the effects of SSR125543 (10 mg/kg/day for 2 weeks) on cognitive impairment induced by traumatic stress exposure are associated with changes in hippocampal excitability. Effects of SSR125543 were compared to those of the 5-HT reuptake inhibitor, paroxetine (10 mg/kg/day), and the partial N-methyl-d-aspartate (NMDA) receptor agonist, d-cycloserine (10 mg/kg/day), two compounds which have demonstrated clinical efficacy against PTSD.

Methods

Mice received two unavoidable electric foot-shocks. Then, 1 or 16 days after stress, they were tested for their memory performance using the object recognition test. Neuronal excitability was recorded during the third week post-stress in the CA1 area of the hippocampus. Drugs were administered from day 1 post-stress to the day preceding the electrophysiological study.

Results

Application of electric shocks produced cognitive impairment 16, but not 1 day after stress, an effect which was associated with a decrease in hippocampal neuronal excitability. Both stress-induced effects were prevented by repeated administration of SSR125543, paroxetine and d-cycloserine.

Conclusions

These findings confirm that the CRF₁ receptor antagonist SSR125543 is able to attenuate the behavioral effects of traumatic stress exposure and indicate that these effects are associated with a normalization of hippocampal neuronal excitability impaired by stress.