Preformulation studies as an essential guide to formulation development and manufacture of protein pharmaceuticals

Physicochemical Characterization of a Recombinant eCG and Comparative Studies with PMSG Commercial Preparations

Equine chorionic gonadotropin (eCG) is a glycoprotein hormone widely used in timed artificial ovulation (TAI) and superovulation protocols to improve the reproductive performance in livestock. Until recently, the only eCG products available in the market for veterinary use consisted in partially purified preparations of pregnant mare serum gonadotropin (PMSG). Here, a bioactive recombinant eCG (reCG) produced in suspension CHO-K1 cells was purified employing different chromatographic methods (hydrophobic interaction chromatography and reverse-phase (RP)-HPLC) and compared with a RP-HPLC-purified PMSG. To gain insight into the structural and functional characteristics of reCG, a bioinformatics analysis was performed. An exhaustive characterization comprising the determination of the purity degree, aggregates and nicked forms through SDS-PAGE, RP-HPLC and SEC-HPLC was performed. Higher order structures were studied by fluorescence spectroscopy and SEC-HPLC. Isoforms profile were analyzed by isoelectric focusing. Glycosylation analysis was performed through pulsed amperometric detection and PNGase F treatment following SDS-PAGE and weak anion exchange-HPLC. Slight differences between the purified recombinant hormones were found. However, recombinant molecules and PMSG exhibited variations in the glycosylation pattern. In fact, differences in sialic acid content between two commercial preparations of PMSG were also obtained, which could lead to differences in their biological potency. These results show the importance of having a standardized production process, as occurs in a recombinant protein bioprocess. Besides, our results reflect the importance of the glycan moieties on eCG conformation and hence in its biological activity, preventing denaturing processes such as aggregation.

A Cationic Amphipathic Tilapia Piscidin 4 Peptide-Based Antimicrobial Formulation Promotes Eradication of Bacterial Vaginosis-Associated Bacterial Biofilms

Bacterial vaginosis (BV) is prevalent among women of reproductive age and has a high rate of recurrence, which can be largely attributed to ineffective BV biofilm eradication by current first-line antibiotics. In this study, we report that the Nile tilapia piscidin 4 (TP4) exhibits broad-spectrum antimicrobial and antibiofilm activity against BV-associated bacteria, but not beneficial lactobacilli. In addition, BV-associated Gardnerella vaginalis remains susceptible to TP4 even after continual exposure to the peptide for up to 22 passages. Gardnerella vaginalis and Streptococcus anginosus are both biofilm-forming BV-associated bacteria, and we found that combining TP4 peptide and disodium EDTA with the biofilm-disrupting agent, chitosan, can eradicate biofilms formed by single or mixed G. vaginalis and S. anginosus. In addition, long-term storage of TP4 peptide in chitosan did not diminish its bactericidal activity toward G. vaginalis. Preformulation studies were performed using High performance liquid chromatography (HPLC) and Circular Dichroism (CD). The long-term stability of TP4 peptide was assessed under various conditions, such as different temperatures and ionic strengths, and in the presence of H₂O₂ and lactic acid. When exposed to sodium dodecyl sulfate (SDS), TP4 maintained its secondary structure at various temperatures, salt and disodium EDTA concentrations. Furthermore, the TP4 microbicide formulation significantly reduced the colonization density of BV-associated bacteria in mice infected with single or mixed bacteria (G. vaginalis and S. anginosus). The TP4 microbicide formulation showed biocompatibility with beneficial human vaginal lactobacilli and female reproductive tissues in C57BL/6 mice. These results suggest that the TP4 microbicide formulation could be a promising topical microbicide agent for BV treatment.

Use of In silico tools for screening buffers to overcome physical instability of Abatacept

Rheumatoid arthritis is an autoimmune disorder. Abatacept (CTLA4-Ig) is used for the treatment of Rheumatoid arthritis. Abatacept is a monoclonal antibody. Monoclonal antibodies undergo chemical (e.g. oxidation, deamidation, hydrolysis) and physical (e.g. aggregation, unfolding) instabilities while handling and storage. Abatacept is also prone to aggregation. Stabilizing agents such as buffers are used to stabilize monoclonal antibodies. But, the selection of the appropriate buffer is a time-consuming process because after testing many buffers based on the analysis of the results the appropriate buffer is identified. To overcome this issue in the current study computational tools were utilized to virtually screen different buffers to select the appropriate buffer. Ligand binding is the principal mechanism of conformational stability of proteins. For the buffers as well ligand binding is the most common mechanism for enhancing the thermodynamic stability of proteins. Generally it is observed that by enhancing the thermodynamic stability there is reduction in the rate of aggregation of proteins. Buffer (ligand) binds to the native state of the protein preferentially; it results in stabilization of the protein, while in the case of denatured protein it has no impact. There are many studies conducted involving the proteins in buffer solutions but very limited information is available about the mechanism of protein-buffer interactions. In the current study ligand binding mechanism of protein - buffer interaction was studied using molecular docking. After the docking buffers were ranked according to their energy value. The lower energy scores represent better protein-buffer (ligand) binding affinity compared to high energy values. It was observed that Phosphate with a binding affinity of -107.9 kcal/mol was the buffer with the least binding energy followed by Citrate (-70.6 kcal/mol), Melglumine (-66.6 kcal/mol), Arginine (-64.5 kcal/mol), Glucono delta lactone (-62.6 kcal/mol), Sodium citrate (-56.5 kcal/mol), Tromethamine (-52.3 kcal/mol), Glycine HCl (-37.2 kcal/mol), Sulfuric acid (-37.7 kcal/mol), Ammonium acetate (-31.1 kcal/mol), Acetic acid (-30.7 kcal/mol). With lower binding energy higher is the affinity between the ligand and protein. So phosphate was identified as a buffer with the highest affinity with Abatacept.

Evaluation of the fusion inhibitor P3 peptide as a potential microbicide to prevent HIV transmission in women

Microbicides are an important strategy for preventing the sexual transmission of HIV but, so far, the most advanced tenofovir-based microbicides have had modest efficacy. This has been related to adherence problems and high prevalence of tenofovir-resistant HIV-1 strains. P3 is a new peptide with potent activity against HIV that may be a good microbicide candidate. In this work P3 was formulated in a gel of hydroxyethyl cellulose and its activity, stability and safety profile in Balb/c mice were evaluated. HIV infection was fully blocked by a 1.5% gel containing P3 at the IC90 (366.4 nM) concentration. The antiviral activity did not change at 4°C during 4 months and at 25, 37 and 65°C for 1 week. P3 was stable and fully functional at acidic pH up to 24h, under different concentrations of hydrogen peroxide and in the presence of genital fluids up to 48h. P3 had no antibacterial activity and did not affect sperm motility and vitality. Finally, P3 didn't cause significant alterations in the vaginal epithelium of Balb/c mice at 0.06 (456.8 μM) and 0.2 mg/day (1522.7 μM) doses. These findings indicate that P3 is an excellent candidate for further development as a microbicide gel for the prevention of HIV transmission in women.

Stabilization of therapeutic proteins in aqueous solutions and freeze-dried solids: an overview

Intrinsic chemical instability and physical instability of therapeutic proteins require appropriate formulations and processes to ensure their efficacy and safety. Recent concerns on possible immunogenicity of the structurally altered protein molecules emphasize relevance of the product quality. Advances in the protein and material researches enable rational design of the aqueous solution and solid protein formulations. This chapter describes the basic process to develop the formulations and choice of excipients that protect the proteins from various stresses during the manufacturing and storage.

Technical decision making with higher order structure data: impact of a formulation change on the higher order structure and stability of a mAb

Changes in formulation may be required during the development of protein therapeutics. Some of the changes may alter the protein higher order structure (HOS). In this note, we show how the change from a trehalose-based formulation to an arginine-based formulation concomitantly impacted the tertiary structure and the thermal stability of a mAb (mAb1). The secondary structure was not disrupted by the formulation change. The destabilization of the tertiary structure did not affect the long-term stability or the bioactivity of mAb1. This indicates that loss of conformational stability was likely compensated by improvements in the colloidal stability of mAb1 in the arginine-based formulation. The formulation-induced changes in HOS were reversible as proven by measurements after dilution in a common buffer (phosphate-buffered saline). For aggregation driven by assembly of aggregates (colloidally limited), small changes in conformational structure and stability as measured by HOS methods may not necessarily be predictive of long-term stability.

Polyethylene glycol-based hydrogels for controlled release of the antimicrobial subtilosin for prophylaxis of bacterial vaginosis

Current treatment options for bacterial vaginosis (BV) have been shown to be inadequate at preventing recurrence and do not provide protection against associated infections, such as that with HIV. This study examines the feasibility of incorporating the antimicrobial peptide subtilosin within covalently cross-linked polyethylene glycol (PEG)-based hydrogels for vaginal administration. The PEG-based hydrogels (4% and 6% [wt/vol]) provided a two-phase release of subtilosin, with an initial rapid release rate of 4.0 μg/h (0 to 12 h) followed by a slow, sustained release rate of 0.26 μg/h (12 to 120 h). The subtilosin-containing hydrogels inhibited the growth of the major BV-associated pathogen Gardnerella vaginalis with a reduction of 8 log10 CFU/ml with hydrogels containing ≥15 μg entrapped subtilosin. In addition, the growth of four common species of vaginal lactobacilli was not significantly inhibited in the presence of the subtilosin-containing hydrogels. The above findings demonstrate the potential application of vaginal subtilosin-containing hydrogels for prophylaxis of BV.

Impact of physiochemical properties on pharmacokinetics of protein therapeutics

Physicochemical properties, such as molecular weight, size, partition coefficient, acid dissociation constant and solubility have a great impact on pharmacokinetics of traditional small molecule drugs and substantially used in development of small drugs. However, predicting pharmacokinetic fate (absorption, distribution, metabolism and elimination) of protein therapeutics from their physicochemical parameters is extremely difficult due to the macromolecular nature of therapeutic proteins and peptides. Their structural complexity and immunogenicity are other contributing factors that determine their biological fate. Therefore, to develop generalized strategies concerning development of therapeutic proteins and peptides are highly challenging. However, reviewing the literature, authors found that physiochemical properties, such as molecular weight, charge and structural modification are having great impact on pharmacokinetics of protein therapeutics and an attempt is made to provide the major findings in this manuscript. This manuscript will serve to provide some bases for developing protein therapeutics with desired pharmacokinetic profile.

Preformulation and stability in biological fluids of the retrocyclin RC-101, a potential anti-HIV topical microbicide

Background

RC-101, a cationic peptide retrocyclin analog, has in vitro activity against HIV-1. Peptide drugs are commonly prone to conformational changes, oxidation and hydrolysis when exposed to excipients in a formulation or biological fluids in the body, this can affect product efficacy. We aimed to investigate RC-101 stability under several conditions including the presence of human vaginal fluids (HVF), enabling the efficient design of a safe and effective microbicide product. Stability studies (temperature, pH, and oxidation) were performed by HPLC, Circular Dichroism, and Mass Spectrometry (LC-MS/MS). Additionally, the effect of HVF on formulated RC-101 was evaluated with fluids collected from healthy volunteers, or from subjects with bacterial vaginosis (BV). RC-101 was monitored by LC-MS/MS for up to 72 h.

Results

RC-101 was stable at pH 3, 4, and 7, at 25 and 37°C. High concentrations of hydrogen peroxide resulted in less than 10% RC-101 reduction over 24 h. RC-101 was detected 48 h after incubation with normal HVF; however, not following incubation with HVF from BV subjects.

Conclusions

Our results emphasize the importance of preformulation evaluations and highlight the impact of HVF on microbicide product stability and efficacy. RC-101 was stable in normal HVF for at least 48 h, indicating that it is a promising candidate for microbicide product development. However, RC-101 stability appears compromised in individuals with BV, requiring more advanced formulation strategies for stabilization in this environment.

Evaluation of chemical degradation of a trivalent recombinant protein vaccine against botulinum neurotoxin by LysC peptide mapping and MALDI-TOF mass spectrometry

Vaccines utilizing recombinant protein antigens typically require an adjuvant to enhance immune response in the recipients. However, the consequences of antigen binding to adjuvant on both the short- and long-term stability of the protein remain poorly defined. In our companion paper (Vessely et al., in press, J Pharm Sci), we characterized the effects of binding to adjuvant on the conformation and thermodynamic stability of three antigen variants for botulinum vaccines: rBoNTA(H(c)), rBoNTB(H(c)), and rBoNTE(H(c)). In the current study, we evaluated the effect of binding to adjuvant (Alhydrogel, aluminum hydroxide) on chemical stability of these antigens during long-term storage in aqueous suspension. We developed methods that employ LysC peptide mapping in conjunction with MALDI-TOF mass spectrometry. Peptide maps were developed for the proteins for a vaccine formulation of rBoNTE(H(c)) as well as a trivalent rBoNT(H(c)) vaccine formulation. This method provided high sequence coverage for the proteins in part due to the implementation of a postdigestion elution fractionation method during sample preparation, and was also successfully utilized to evaluate the chemical integrity of adjuvant-bound rBoNT(H(c)) protein antigens. We found that all three of the rBoNT(H(c)) proteins were susceptible to degradation via both oxidation and deamidation. In many cases, such reactions occurred earlier with the adjuvant-bound protein formulations when compared to the proteins in control samples that were not bound to adjuvant. Additionally, some chemical modifications were found in the adjuvant-bound protein formulations but were not detected in the unbound solution controls. Our studies indicate that binding to aluminum-based adjuvants can impact the chemical stability and/or the chemical degradation pathways of protein during long-term storage in aqueous suspension. Furthermore, the methods we developed should be widely useful for assessing chemical stability of adjuvant-bound recombinant protein antigens.

Effects of glycosylation on the stability of protein pharmaceuticals

In recent decades, protein-based therapeutics have substantially expanded the field of molecular pharmacology due to their outstanding potential for the treatment of disease. Unfortunately, protein pharmaceuticals display a series of intrinsic physical and chemical instability problems during their production, purification, storage, and delivery that can adversely impact their final therapeutic efficacies. This has prompted an intense search for generalized strategies to engineer the long-term stability of proteins during their pharmaceutical employment. Due to the well known effect that glycans have in increasing the overall stability of glycoproteins, rational manipulation of the glycosylation parameters through glycoengineering could become a promising approach to improve both the in vitro and in vivo stability of protein pharmaceuticals. The intent of this review is therefore to further the field of protein glycoengineering by increasing the general understanding of the mechanisms by which glycosylation improves the molecular stability of protein pharmaceuticals. This is achieved by presenting a survey of the different instabilities displayed by protein pharmaceuticals, by addressing which of these instabilities can be improved by glycosylation, and by discussing the possible mechanisms by which glycans induce these stabilization effects.

Effects of Solutes on Empirical Phase Diagrams of Human Fibroblast Growth Factor 1

A variety of solutes are commonly used to increase the stability of protein in therapeutic formulations. An empirical phase diagram approach is used to evaluate the effects of different types of additives on the solution behavior of a protein of pharmaceutical interest, human fibroblast growth factor 1 (FGF-1). A specific stabilizer, heparin, and a nonspecific stabilizer, sucrose, were used in this work. The protein was characterized as a function of pH (3-8) and temperature (10-85 degrees C) using Far-UV circular dichroism (Far-UV CD), intrinsic and extrinsic fluorescence as well as second derivative UV absorption spectroscopy. Empirical phase diagrams were constructed to summarize the biophysical characterization data obtained with FGF-1 alone, in the presence of a threefold weight excess of heparin (3x heparin) or 10% sucrose (w/v). Three phases are observed in the low temperature regions at pH 3, 4, and 5-8. Phase boundaries corresponding to major heat-induced transitions are detected in the physiological temperature range. The highest thermal stabilities are observed near neutral pH (pH 6 and 7). Both heparin and sucrose appear to enhance the thermal stability of FGF-1, although their effects on the phase diagram are quite distinct. The greatest stabilization is observed at pH 8. Only heparin appears to protect FGF-1 from acid-induced unfolding to any extent.

A Critical Evaluation of Tm(FTIR) Measurements of High-Concentration IgG1 Antibody Formulations as a Formulation Development Tool

PURPOSE

Fourier-transform infrared (FTIR) spectroscopy was applied for the determination of protein melting temperature (Tm(FTIR)) and to assess the stability predictability of a 100-mg/mL liquid IgG1 antibody formulation.

METHODS

Tm(FTIR) values of various formulations (different pH, buffers, excipients) were compared to the results of a stability study under accelerated conditions (40 degrees C/75% relative humidity), using size-exclusion high-performance liquid chromatography (SE-HPLC) and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) for the detection of soluble aggregates and covalent modifications.

RESULTS

The highest Tm(FTIR) was achieved at pH 5.5, and, similarly, SE-HPLC and SDS-PAGE results suggested a pH optimum between 5.5 and 6.0. Transition temperatures were comparable for all tested buffers. However, the decrease in the monomer fraction upon thermal storage was the lowest for citrate buffers. Whereas sugars and polyols resulted in an increase in Tm(FTIR) and enhanced monomer fraction after storage, amino acids showed a destabilization according to SE-HPLC analysis, albeit no change or even an increase in the melting temperature was observed.

CONCLUSIONS

All examples gave evidence that Tm(FTIR) values did not necessarily correspond to the storage stability at 40 degrees C analyzed by means of SE-HPLC and SDS-PAGE. Tm values, e.g., determined by FTIR, should only be employed as supportive information to the results from both real-time and accelerated stability studies.

FTIR and nDSC as analytical tools for high-concentration protein formulations

PURPOSE

The aim of the study is to evaluate Fourier-transform infrared spectroscopy (FTIR) as an analytical tool for high-concentrated protein formulations.

METHODS

FTIR is used to determine the melting temperature (T(m (FTIR))) of various proteins, such as bovine serum albumin (BSA), immunoglobulin (IgG1), beta-lactoglobulin (beta-LG), and lysozyme (HEWL), at different protein concentrations (5-100 mg/mL), where four data interpretation methods are discussed. The obtained T(m (FTIR)) values are further compared to the T(m) measured by the nanodifferential scanning calorimetry (nDSC) technique.

RESULTS

The T(m (FTIR)) values of IgG1 and beta-LG showed strong consistency and corresponded to the nDSC results irrespective of the method of data interpretation and the protein concentration applied. In contrast, the T(m (FTIR)) of BSA and HEWL is characterized by significant deviations. Only the midpoint of the second-derivative intensity-temperature curve of the intermolecular beta-sheet mode measured at a concentration of 100 mg/mL is consistent with the nDSC results.

CONCLUSIONS

Determination of a T(m (FTIR)) is feasible by the midpoint of the intensity-temperature plot of the arising intermolecular beta-sheet band. More significant results are obtained for proteins, which are predominantly composed of intramolecular beta-sheet elements as well as at higher protein concentrations. A further study was started to assess the predictability of long-term protein stability by T(m (FTIR)).