Stability and characterization of human growth hormone

Characterization of a macroporous epoxy-polymer based resin for the ion-exchange chromatography of therapeutic proteins

This study investigated the adsorption capacity and mass transfer properties of a novel macroporous epoxy-polymer-based anion-exchanger, MPR Q, for the efficient separation of therapeutic proteins. MPR Q resin was prepared by phase separation based on spinodal decomposition followed by dextran grafting and ligand conjugation. Under static conditions, MPR Q exhibited a binding capacity of 49.8 mg-IgG/cm³-resin at pH 10, whereas the fastest adsorption was observed among the anion-exchanger resins tested. Inverse size-exclusion chromatography (iSEC) experiments revealed that the apparent pore diameter of MPR Q was approximately 90 nm, which was sufficiently large for the penetration of human IgG and bovine IgM. Moreover, the reduced height equivalent to a theoretical plate, h, of human IgG, determined using the linear gradient elution method was 65.8 and was not significantly changed in the range of linear velocities from 20.37 to 50.93 cm/min. The dynamic binding capacity at 10% breakthrough of MPR Q, determined by frontal analysis, exhibited a capacity of 43.8 mg/cm³ at 5.09 cm/min and 58% of DBC_10% was maintained even though the linear velocity was increased to 50.93 cm/min. Furthermore, a resolution for separation of IgG and BSA by MPR Q was 1.06 at 5.09 cm/min, while it was higher than that for the conventional resin at all linear velocities from 5.09 cm/min to 50.93 cm/min. Thus, it was suggested that the MPR Q developed in this study is a promising resin that can efficiently separate large biomacromolecules such as human IgG at higher velocities.

Peptide-Based Inhibitors for SARS-CoV-2 and SARS-CoV

The COVID‐19 (coronavirus disease) global pandemic, caused by the spread of the SARS‐CoV‐2 (severe acute respiratory syndrome coronavirus 2) virus, currently has limited treatment options which include vaccines, anti‐virals, and repurposed therapeutics. With their high specificity, tunability, and biocompatibility, small molecules like peptides are positioned to act as key players in combating SARS‐CoV‐2, and can be readily modified to match viral mutation rate. A recent expansion of the understanding of the viral structure and entry mechanisms has led to the proliferation of therapeutic viral entry inhibitors. In this comprehensive review, inhibitors of SARS and SARS‐CoV‐2 are investigated and discussed based on therapeutic design, inhibitory mechanistic approaches, and common targets. Peptide therapeutics are highlighted, which have demonstrated in vitro or in vivo efficacy, discuss advantages of peptide therapeutics, and common strategies in identifying targets for viral inhibition.

Development and Characterization of Sodium Hyaluronate Microparticle-Based Sustained Release Formulation of Recombinant Human Growth Hormone Prepared by Spray-Drying

The purpose of this study was to develop and characterize a sodium hyaluronate microparticle-based sustained release formulation of recombinant human growth hormone (SR-rhGH) prepared by spray-drying. Compared to freeze-drying, spray-dried SR-rhGH showed not only prolonged release profiles but also better particle property and injectability. The results of size-exclusion high-performance liquid chromatography showed that no aggregate was detected, and dimer was just about 2% and also did not increase with increase of inlet temperature up to 150 °C. Meanwhile, the results of reversed-phase high-performance liquid chromatography revealed that related proteins increased slightly from 4.6% at 100 °C to 6.3% at 150 °C. Thermal mapping test proved that product temperature did not become high to cause protein degradation during spray-drying because thermal energy was used for the evaporation of surface moisture of droplets. The structural characterization by peptide mapping, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and circular dichroism revealed that the primary, secondary, and tertiary structures of rhGH in SR-rhGH were highly comparable to those of reference somatropin materials. The biological characterization by rat weight gain and cell proliferation assays provided that bioactivity of SR-rhGH was equivalent to that of native hGH. These data establish that spray-dried SR-rhGH is highly stable by preserving intact rhGH and hyaluronate microparticle-based formulation by spray-drying can be an alternative delivery system for proteins.

A novel long-acting human growth hormone fusion protein (VRS-317): enhanced in vivo potency and half-life

A novel recombinant human growth hormone (rhGH) fusion protein (VRS-317) was designed to minimize receptor-mediated clearance through a reduction in receptor binding without mutations to rhGH by genetically fusing with XTEN amino acid sequences to the N-terminus and the C-terminus of the native hGH sequence. Although in vitro potency of VRS-317 was reduced approximately 12-fold compared with rhGH, in vivo potency was increased because of the greatly prolonged exposure to the target tissues and organs. VRS-317 was threefold more potent than daily rhGH in hypophysectomized rats and fivefold more potent than daily rhGH in juvenile monkeys. In juvenile monkeys, a monthly dose of 1.4 mg/kg VRS-317 (equivalent to 0.26 mg/kg rhGH) caused a sustained pharmacodynamic response for 1 month equivalent to 0.05 mg/kg/day rhGH (1.4 mg/kg rhGH total over 28 days). In monkeys, VRS-317, having a terminal elimination half-life of approximately 110 h, was rapidly and near-completely absorbed, and was well tolerated with no observed adverse effects after every alternate week subcutaneous dosing for 14 weeks. VRS-317 also did not cause lipoatrophy in pig and monkey studies. VRS-317 is currently being studied in GH-deficient patients to confirm the observations in these animal studies.

Protein-excipient interactions: mechanisms and biophysical characterization applied to protein formulation development

The purpose of this review is to demonstrate the critical importance of understanding protein-excipient interactions as a key step in the rational design of formulations to stabilize and deliver protein-based therapeutic drugs and vaccines. Biophysical methods used to examine various molecular interactions between solutes and protein molecules are discussed with an emphasis on applications to pharmaceutical excipients in terms of their effects on protein stability. Key mechanisms of protein-excipient interactions such as electrostatic and cation-pi interactions, preferential hydration, dispersive forces, and hydrogen bonding are presented in the context of different physical states of the formulation such as frozen liquids, solutions, gels, freeze-dried solids and interfacial phenomenon. An overview of the different classes of pharmaceutical excipients used to formulate and stabilize protein therapeutic drugs is also presented along with the rationale for use in different dosage forms including practical pharmaceutical considerations. The utility of high throughput analytical methodologies to examine protein-excipient interactions is presented in terms of expanding formulation design space and accelerating experimental timelines.

The impact of drying method and formulation on the physical properties and stability of methionyl human growth hormone in the amorphous solid state

The objective of this work was to investigate the impact of drying method and formulation on the physical stability (aggregation) and selected important physical properties of dried methionyl human growth hormone (Met-hGH) formulations. Solutions of Met-hGH with different stabilizers were dried by different methods (freeze drying, spray drying, and film drying), with and without surfactant. Properties of the dried powders included powder morphology, specific surface area (SSA), protein surface coverage, thermal analysis, and protein secondary structure. Storage stability of Met-hGH in different formulations was also studied at 50 degrees C and at 60 degrees C for 3 months. The dried powders displayed different morphologies, depending mainly on the method of drying and on the presence or absence of surfactant. Film dried powders had the lowest SSA (approximately 0.03 m(2)/g) and the lowest total protein surface accumulation (approximately 0.003%). Surfactant caused a reduction in the SSA of both spray dried and freeze dried powders. Spray dried powders showed greater protein surface coverage and SSA relative to the same formulations dried by other means. Greater in-process perturbations of protein secondary structure were observed with polymer excipients. Formulation impacted physical stability. In general, low molecular weight stabilizers provided better stability. For example, the aggregation rate at 50 degrees C of Met-hGH in a freeze dried trehalose-based formulation was approximately four times smaller than the corresponding Ficoll-70-based formulation. Drying method also influenced physical stability. In general, the film dried preparations studied showed superior stability to preparations dried by other methods, especially those formulations employing low molecular weight stabilizers.

Analysis of recombinant human growth hormone by capillary electrophoresis with bilayer-coated capillaries using UV and MS detection

The characterization of recombinant human growth hormone (rhGH; somatropin) by capillary electrophoresis (CE) with UV-absorbance and mass spectrometric (MS) detection using capillaries noncovalently coated with polybrene (PB) and poly(vinyl sulfonic acid) (PVS) is demonstrated. Compared with bare fused-silica capillaries, PB-PVS coated capillaries yielded more favorable migration-time reproducibilities and higher separation efficiencies. Optimal separation conditions for the bilayer-coated capillaries comprised a background electrolyte (BGE) of 400 mM Tris phosphate (pH 8.5) yielding migration-time R.S.D.s of less than 1.0% and plate numbers above 300,000 for intact rhGH. The protein was also analyzed using the CE method described in the European Pharmacopoeia (Ph. Eur.) monograph. The pharmacopoeial method gave much longer analysis times (22 min versus 8 min), lower resolution and plate numbers, and consecutive shifts in migration time for rhGH, indicating possible interactions between the protein and the inner capillary wall. Due to stable migration times obtained with the coated capillaries, reliable profiling and quantification of rhGH and its byproducts in time was possible. Analysis of thermally degraded rhGH revealed the formation of two main degradation products. CE-mass spectrometry (MS) of this sample, using a PB-PVS coated capillary and a BGE of 75 mM ammonium formate (pH 8.5), suggests that these products are desamido forms of rhGH. Analyses of expired rhGH preparations with CE-UV and CE-MS indicated the presence of both deamidation and oxidation products.

Molecular Dynamics Simulations and Oxidation Rates of Methionine Residues of Granulocyte Colony-Stimulating Factor at Different pH Values

To understand the connection between the conformation of a protein molecule and the oxidation of its methionine residues, we measured the rates of oxidation of methionine residues by H(2)O(2) in granulocyte colony-stimulating factor (G-CSF) as a function of pH and also studied the structural properties of this protein as a function of pH via molecular dynamics simulations. We found that each of the four methionine groups in G-CSF have significant and different rates of oxidation as a function of pH. Moreover, Met(1), in the unstructured N-terminal region, has a rate of oxidation as low as half that of free methionine. The structural properties of G-CSF as a function of pH are evaluated in terms of properties such as hydrogen bonding, deviations from X-ray structure, helical/helical packing, and the atomic covariance fluctuation matrix of alpha-carbons. We found that dynamics (structural fluctuations) are essential in explaining oxidation and that a static picture, such as that resulting from X-ray data, fails in this regard. Moreover, the simulation results also indicate that the solvent-accessible area, traditionally used to measure solvent accessibility of a protein site, of the sulfur atom of methionine residues does not correlate well with the rate of oxidation. Instead, we identified a structural property, average two-shell water coordination number, that correlates well with measured oxidation rates.

Computational stabilization of human growth hormone

Recombinant human growth hormone (hGH) is used worldwide for the treatment of pediatric hypopituitary dwarfism and in children suffering from low levels of hGH. It has limited stability in solution, and because of poor oral absorption, is administered by injection, typically several times a week. Development has therefore focused on more stable or sustained-release formulations and alternatives to injectable delivery that would increase bioavailability and make it easier for patients to use. We redesigned hGH computationally to improve its thermostability. A more stable variant of hGH could have improved pharmacokinetics or enhanced shelf-life, or be more amenable to use in alternate delivery systems and formulations. The computational design was performed using a previously developed combinatorial optimization algorithm based on the dead-end elimination theorem. The algorithm uses an empirical free energy function for scoring designed sequences. This function was augmented with a term that accounts for the loss of backbone and side-chain conformational entropy. The weighting factors for this term, the electrostatic interaction term, and the polar hydrogen burial term were optimized by minimizing the number of mutations designed by the algorithm relative to wild-type. Forty-five residues in the core of the protein were selected for optimization with the modified potential function. The proteins designed using the developed scoring function contained six to 10 mutations, showed enhancement in the melting temperature of up to 16 degrees C, and were biologically active in cell proliferation studies. These results show the utility of our free energy function in automated protein design.

Effects of formulation and process variables on the aggregation of freeze-dried interleukin-6 (IL-6) after lyophilization and on storage

This study assessed the impact of residual moisture, Tg, and excipient physical state of different formulations on the "in-process" and shelf-life stability of freeze-dried interleukin-6 (IL-6). The effect of an annealing procedure was also evaluated. Characterization of the lyophilizates was done by Karl Fischer titration, differential scanning calorimetry (DSC), and x-ray measurements. Analysis of protein stability was carried out by size exclusion chromatography (SEC), sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), and turbidity measurements. During freeze-drying, the most effective protection against aggregation was provided by completely amorphous formulations consisting of trehalose or sucrose either alone or in combination with glycine or mannitol. Other amorphous formulations like those of sucrose with lysine-HCl or dextran could not provide comparable stabilization. In lyophilizates containing a crystallized excipient such as glycine or mannitol, IL-6 suffered destabilization, which was less pronounced if an additional amorphous excipient was present. For the completely amorphous formulations, aggregation was prevented during a 9-month storage at 25 and 40 degrees C as long as the storage temperature did not exceed the Tg value of the lyophilizate, otherwise severe damage occurred. Formulations containing amorphous dextran or lysine-HCl could not effectively stabilize IL-6 even when stored below Tg. Annealing helped to improve cake robustness and appearance, but for lyophilizates containing an excipient crystallized by annealing an increase of IL-6 aggregation was observed despite a storage below Tg. Thus, the amorphous state of the excipients and a high Tg can be considered necessary conditions for preventing aggregation of freeze-dried IL-6. Whether the conditions are also sufficient depends on the choice of excipients. Destabilization can occur with some excipients despite their amorphous state as well as in the presence of crystallized excipients despite a storage below Tg. Compared to sucrose, trehalose is a more favorable excipient for protein lyophilization because it exhibits a higher Tg, possesses better stabilizing properties, and can reduce protein aggregation which may have been caused by annealing.

Thermodynamic characterization of an intermediate state of human growth hormone

The thermal denaturation of recombinant human growth hormone (rhGH) was studied by differential scanning calorimetry and circular dichroism spectroscopy (CD). The thermal unfolding is reversible only below pH 3.5, and under these conditions a single two-state transition was observed between 0 and 100 degrees C. The magnitudes of the deltaH and deltaCp of this transition indicate that it corresponds to a partial unfolding of rhGH. This is also supported by CD data, which show that significant secondary structure remains after the unfolding. Above pH 3.5 the thermal denaturation is irreversible due to the aggregation of rhGH upon unfolding. This aggregation is prevented in aqueous solutions of alcohols such as n-propanol, 2-propanol, or 1,2-propanediol (propylene glycol), which suggests that the self-association of rhGH is caused by hydrophobic interactions. In addition, it was found that the native state of rhGH is stable in relatively high concentrations of propylene glycol (up to 45% v/v at pH 7-8 or 30% at pH 3) and that under these conditions the thermal unfolding is cooperative and corresponds to a transition from the native state to a partially folded state, as observed at acidic pH in the absence of alcohols. In higher concentrations of propylene glycol, the tertiary structure of rhGH is disrupted and the cooperativity of the unfolding decreases. Moreover, the CD and DSC data indicate that a partially folded intermediate with essentially native secondary structure and disordered tertiary structure becomes significantly populated in 70-80% propylene glycol.

Recombinant human growth hormone poly(lactic-co-glycolic acid) microsphere formulation development

The development of a sustained release formulation of recombinant human growth hormone (rhGH) has focused on a depot preparation using the biodegradable polymer, poly(lactic-co-glycolic acid) (PLGA), for microsphere production. These formulations have been designed to assure the maintenance of protein integrity both during the microencapsulation process and upon subsequent release in vitro and in vivo. In addition, animal models were developed to assess both the in vivo release kinetics and the potency of the released protein. These studies emphasized the importance of obtaining a correlation between the in vivo and in vitro release at an early stage of development. Juvenile rhesus monkey studies revealed that continuous rhGH administration resulted in a greater total insulin-like growth factor-I (IGF-I) response than daily rhGH administration, indicating that a continuous rhGH dose may provide comparable efficacy to daily dosing at a lower total dose of rhGH. The use of a conventional water-in-oil-in-water process yielded a triphasic release of biologically active and non-immunogenic rhGH, while the novel cryogenic process achieved a continuous release of rhGH that is biologically active and non-immunogenic. The rhGH PLGA formulation produced by the novel cryogenic process was manufactured under aseptic GMP conditions and was shown to be safe in growth hormone-deficient adults. This protein and these studies should serve as a model for the future development of PLGA formulations for therapeutic proteins.

Use of poloxamer polymers to stabilize recombinant human growth hormone against various processing stresses

Several processing and shipping stresses were investigated for their effect on the physical stability of recombinant human growth hormone (rhGH). These included exposure to air/water interfaces, adsorption to hydrophobic surfaces, freeze-thaw cycles, and temperature. The interfacially and thermally denatured hormone was evaluated for the presence of insoluble and soluble aggregates by spectrophotometry and by size-exclusion chromatography, respectively. Noncovalent aggregates were generated by either vortexing or multiple passages through a hypodermic needle, processes which exposed the protein to air/water interfaces. Thermal stress also resulted in the generation of aggregates. This aggregation was reduced or eliminated by the use of poloxamer polymers. Under the conditions employed, filtration through some commercially available filters, exposure to hydrophobic beads, or multiple freeze-thaw cycles did not produce any aggregates within the limitations of the analytical procedures used. Based on this study, Poloxamer 407 was found to be the most effective stabilizer for rhGH for protection against interfacial and thermal stress.

Effect of surfactants on the physical stability of recombinant human growth hormone

The physical stability of a human growth hormone (hGH) formulation upon exposure to air/water interfaces (with vortex mixing) and to nonisothermal stress [determined by differential scanning calorimetry (DSC)] was investigated. The effect of these stresses on the formation of soluble and insoluble aggregates was studied. The aggregates were characterized and quantified by size exclusion-HPLC and UV spectrophotometry. Vortex mixing of hGH solutions (0.5 mg/mL) in phosphate buffer, pH 7.4, for just 1 min caused 67% of the drug to precipitate as insoluble aggregates. These aggregates were noncovalent in nature. Non-ionic surfactants prevented the interfacially induced aggregation at their critical micelle concentration (cmc) for Pluronic F-68 (polyoxyethylene polyoxypropylene block polymer) and Brij 35 (polyoxyethylene alkyl ether) and above the cmc for Tween 80 (polyoxyethylene sorbitan monooleate). However, the same surfactants failed to stabilize hGH against thermal stress in DSC studies. Higher concentrations of surfactants actually destabilized hGH as evidenced by the decrease in the onset temperature for the denaturation endotherm.