Oxidation of human insulin-like growth factor I in formulation studies. 3. Factorial experiments of the effects of ferric ions, EDTA, and visible light on methionine oxidation and covalent aggregation in aqueous solution

Protein Formulations Containing Polysorbates: Are Metal Chelators Needed at All?

Proteins are prone to post-translational modifications at specific sites, which can affect their physicochemical properties, and consequently also their safety and efficacy. Sources of post-translational modifications include oxygen and reactive oxygen species. Additionally, catalytic amounts of Fe(II) or Cu(I) can promote increased activities of reactive oxygen species, and thus catalyse the production of particularly reactive hydroxyl radicals. When oxidative post-translational modifications are detected in the biopharmaceutical industry, it is common practice to add chelators to the formulation. However, the resultant complexes with metals can be even more damaging. Indeed, this is supported here using an ascorbate redox system assay and peptide mapping. Ethylenediaminetetraacetic acid (EDTA) addition strongly accelerated the formation of hydroxyl radicals in an iron-ascorbate system, while diethylenetriaminepentaacetic acid (DTPA) addition did not. When Fe(III) was substituted with Cu(II), EDTA addition almost stopped hydroxyl radical production, whereas DTPA addition showed continued production, but at a reduced rate. Further, EDTA accelerated metal-catalysed oxidation of proteins, and thus did not protect them from Fe-mediated oxidative damage. As every formulation is unique, justification for EDTA or DTPA addition should be based on experimental data and not common practice.

Mitigation of Oxidation in Therapeutic Antibody Formulations: a Biochemical Efficacy and Safety Evaluation of N-Acetyl-Tryptophan and L-Methionine

PURPOSE

Biotherapeutics can be susceptible to oxidation during manufacturing and storage. Free L-methionine is known to protect methionine residues in proteins from oxidation. Similarly, free tryptophan and other indole derivatives have been shown to protect tryptophan residues from oxidation. N-acetyl-DL-tryptophan was previously identified as a potentially superior antioxidant to tryptophan as it has a lower oxidation potential and produces less peroxide upon light exposure. This study sought to confirm the antioxidant efficacy and safety of N-acetyl-DL-tryptophan and L-methionine as formulation components for biotherapeutic drugs.

METHODS

Antibodies were subjected to AAPH and light exposure in the presence of N-acetyl-DL-tryptophan and L-methionine. Oxidation in relevant CDR and Fc residues was quantified by peptide map. In silico, in vitro, and in vivo studies were performed to evaluate the safety of N-acetyl-DL-tryptophan and L-methionine.

RESULTS

Peptide mapping demonstrated that N-acetyl-DL-tryptophan was effective at protecting tryptophans from AAPH stress, and that the combination of N-acetyl-DL-tryptophan and L-methionine protected both tryptophan and methionine from AAPH stress. The safety assessment suggested an acceptable safety profile for both excipients.

CONCLUSIONS

N-acetyl-tryptophan and L-methionine effectively reduce the oxidation of susceptible tryptophan and methionine residues in antibodies and are safe for use in parenteral biotherapeutic formulations.

Isoform Separation by a Mixed-mode Resin, TOYOPEARL MX-Trp-650M

TOYOPEARL particles are cross-linked hydroxylated methacrylic polymers available in different pore and particle sizes. They are conjugated with different ligands to generate ion-exchange, hydrophobic interaction and affinity resins. They have excellent physical and chemical properties. A mixed-mode resin, TOYOPEARL MX-Trp-650M, is made of this particle with tryptophan conjugated via N-terminal amino group and hence has both hydrophobic/aromatic side chain and carboxyl group. In this review, I will summarize the properties of the TOYOPEARL particles and MX-Trp-650M resin and application of this resin for purification of proteins and in some detail the separation of disulfide (SS)- scrambled oligomers of insulin-like growth factor-1 (IGF-1). For this particular application, the intact IGF-1 was used to examine binding and elution conditions of TOYOSCREEN MX-Trp-650M column. Strong binding was obtained at pH 4.0, at which arginine, but not NaCl, resulted in elution. Both NaCl and arginine resulted in elution at pH 6.5. In addition, a pH gradient from 4.0 to 8.5 was effective. When applied to SS-scrambled IGF-1 oligomers, both pH and arginine gradient exhibited an efficient separation of the oligomers.

The biological activity of FasL in human and mouse lungs is determined by the structure of its stalk region

Acute lung injury (ALI) is a life-threatening condition in critically ill patients. Injury to the alveolar epithelium is a critical event in ALI, and accumulating evidence suggests that it is linked to proapoptotic Fas/FasL signals. Active soluble FasL (sFasL) is detectable in the bronchoalveolar lavage (BAL) fluid of patients with ALI, but the mechanisms controlling its bioactivity are unclear. We therefore investigated how the structure of sFasL influences cellular activation in human and mouse lungs and the role of oxidants and proteases in modifying sFasL activity. The sFasL in BAL fluid from patients with ALI was bioactive and present in high molecular weight multimers and aggregates. Oxidants generated from neutrophil myeloperoxidase in BAL fluid promoted aggregation of sFasL in vitro and in vivo. Oxidation increased the biological activity of sFasL at low concentrations but degraded sFasL at high concentrations. The amino-terminal extracellular stalk region of human sFasL was required to induce lung injury in mice, and proteolytic cleavage of the stalk region by MMP-7 reduced the bioactivity of sFasL in human cells in vitro. The sFasL recovered from the lungs of patients with ALI contained both oxidized methionine residues and the stalk region. These data provide what we believe to be new insights into the structural determinants of sFasL bioactivity in the lungs of patients with ALI.

Effect of gamma-sterilization process on PLGA microspheres loaded with insulin-like growth factor-I (IGF-I)

The influence of gamma-sterilization on the physicochemical properties of a controlled release formulation for the insulin-like growth factor-I (IGF-I) was investigated in this study. Recombinant human insulin-like growth factor-I (rhIGF-I) was efficiently entrapped in poly (D,L-lactide-co-glycolide) (PLGA) microspheres by water-in-oil-in-water (W/O/W) solvent evaporation technique. Microspheres were irradiated at a dose of 25kGy and evaluated by means of scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). The stability of the released protein was investigated by circular dichroism (CD) and sodium dodecyl sulfate polyacrilamide gel electrophoresis (SDS-PAGE). No difference was noticed in microsphere size and morphology before and after irradiation. Drug loading remains essentially the same after the sterilization process. However, rhIGF-I aggregation was detected by electrophoresis. In addition, subtle changes in DSC pattern were noticed for irradiated microspheres. In vitro drug release from irradiated microspheres was also affected, showing an increased burst effect. From this results it can be concluded that gamma-sterilization process causes changes in the properties of rhIGF-I loaded microspheres.

Complete disulfide bond assignment of a recombinant immunoglobulin G4 monoclonal antibody

Recombinant monoclonal antibodies (mAbs) are an emerging therapeutic area. However, there are few reports on disulfide bond assignment of recombinant mAbs. This work describes the complete disulfide bond assignment of a recombinant immunoglobulin G4 (IgG4) mAb. N-ethylmaleimide (NEM) was used to mask free sulfhydryl groups present in the mAb. Digestion of the mAb with endoproteinase Lys-C without disulfide scrambling was achieved by denaturing the mAb in the presence of NEM in guanidine hydrochloride (GuHCl). The Lys-C digest was subsequently reduced with dithiothreitol (DTT). Native and reduced Lys-C digests were mass analyzed by on-line reversed-phase-high-performance liquid chromatography mass spectrometry (RP-HPLC/MS). Disulfide-containing peptides were sequenced by off-line nanoelectrospray quadrupole time-of-flight mass spectrometry (nanoESI-QTOF MS) and N-terminal Edman sequencing for verifying connectivities. The recombinant IgG4 mAb was found to contain the expected disulfide linkages with the proposed method. The NEM alkylating reagent was critical in minimizing disulfide scrambling during the denaturation and digestion of the mAb. This integrated approach, combining MS and N-terminal Edman sequencing, was capable of assigning the disulfide pattern of the IgG4 mAb rapidly and completely, and should be applicable for disulfide bond assignment and structural analysis of other mAbs and large proteins with multiple disulfide bonds.

Effects of conformation on the chemical stability of pharmaceutically relevant polypeptides

Control of chemical instability in protein pharmaceuticals continues to be a critical issue in developing stable formulations. While the effects of pH, buffer composition, ionic strength and temperature remain the most effective methods for controlling hydrolysis and oxidation reactions, it appears that conformational control may also be important. Addition of excipients to maintain native structure and reduce the propensity of the protein to denature and/or aggregate is already a central theme in stabilizing proteins (Arakawa et al., 1993). The same additives have now been found to slow both deamidation and oxidation, whether in solution or in the solid state. What is emerging is an additional approach for producing protein pharmaceuticals that maintain native structure and activity during long-term storage.

Reversed phase HPLC of Met58 oxidized rhIL-11: oxidation enhanced by plastic tubes

The hydrophobicity of human recombinant interleukin 11 (rhIL-11) with an oxidized Met58 residue is nearly identical to the hydrophobicity of native rhIL-11. Consequently, separation of these species using standard gradient elution or isocratic elution is very difficult. Using an optimized, shallow gradient RP-HPLC method. Met58 oxidized rhIL-11 could be separated sufficiently from native rhIL-11. The identity of the oxidized form detected with this method was confirmed by peptide mapping with trypsin and endoproteinase Asp-N, N-terminal sequencing and mass spectrometric analysis. This method was employed to determine the effect of disposable laboratory plastic tubes for the oxidation. The amounts of Met58 oxidized rhIL-11 were increased when rhIL-11 samples were stored in plastic tubes at 37 degrees C in the dark. Samples stored in polypropylene tubes were oxidized much more than samples stored in polystyrene tubes. Additionally, the oxidation was greatly enhanced when samples were stored in polypropylene tubes exposed to light before rhIL-11 sample storage. The extent of the oxidation was also affected by the sources of polypropylene tubes. A maximum increase in Met58 oxidized rhIL-11 was more than 30% when samples were stored at 37 degrees C for 14 days in polypropylene tubes exposed to a daylight fluorescent lamp for 25 days. Consequently, these results indicate that attention should be paid for selection of suitable plastic tubes used for storage of protein samples, and for protection of the plastic tubes themselves from extended exposure to light while in storage.