Junyan A. Ji

Compatibility, Physical Stability, and Characterization of an IgG4 Monoclonal Antibody After Dilution into Different Intravenous Administration Bags

The physical stability of an immunoglobulin G4 monoclonal antibody (mAb) upon dilution into intravenous (i.v.) bags containing 0.9% saline was examined. Soluble aggregates and subvisible particles were observed by size-exclusion high-performance liquid chromatography (SE-HPLC) and light obscuration when formulated with suboptimal levels of polysorbate 20. The formation of soluble aggregates and particulates was further characterized by a combination of SE-HPLC, nanoparticle tracking analysis (NTA), microflow-digital imaging (MFI), and turbidity measurements. With sufficient PS20 levels, particle formation was minimized, although quantification of submicron sized particles by NTA was not possible because of the interference from PS20. Intravenous bags composed of polyvinyl chloride caused more protein particle formation than polyolefin bags. Differences between bag types were affected by removing headspace and by transferring the saline solution into glass vials. Characterization studies with Fourier transform infrared microscopy and extrinsic fluorescence spectroscopy demonstrated that isolated particles contained native-like secondary structure with partially altered tertiary structure, compared with heat-denatured and nonstressed controls. Transmission electron microscopy and MFI analysis showed particles had an amorphous morphology of varying sizes. Particles contained some non-native disulfide bond crosslinks, potentially initiated by low levels of free thiol in the native mAb. The critical role of proper formulation design to stabilize proteins against physical instability during i.v. administration is discussed.

Effect of Individual Fc Methionine Oxidation on FcRn Binding: Met252 Oxidation Impairs FcRn Binding More Profoundly than Met428 Oxidation

The long serum half-lives of mAbs are conferred by pH-dependent binding of IgG-Fc to the neonatal Fc receptor (FcRn). The Fc region of human IgG1 has three conserved methionine residues, Met252, Met358, and Met428. Recent studies showed oxidation of these Met residues impairs FcRn binding and consequently affects pharmacokinetics of therapeutic antibodies. However, the quantitative effect of individual Met oxidation on Fc-FcRn binding has not been addressed. This information is valuable for defining critical quality attributes. In the present study, two sets of homodimeric site-directed IgG1 mutations were generated to understand how individual Fc Met oxidation affects FcRn binding. The first approach used Met to Leu mutants to block site-specific Met oxidation. In the other approach, Met to Gln mutants were designed to mimic site-specific Met oxidation. Both mutagenesis approaches show that either Met252 or Met428 oxidation alone significantly impairs Fc-FcRn binding. Met252 oxidation has a more deleterious effect on FcRn binding than M428 oxidation, whereas Met428 oxidation has a bigger destabilization effect on the thermal stability. Our results also show that Met358 oxidation does not affect FcRn binding. In addition, our study suggests that Met to Gln mutation may serve as an important tool to understand Met oxidation.

The Relative Rate of Immunoglobulin Gamma 1 Fragmentation

The physicochemical stability of protein therapeutics is of significant pharmaceutical interest. Immunoglobulin gamma (IgG) hinge region fragmentation has recently garnered attention as an important degradation route of therapeutic monoclonal antibodies. In this work, the rates and relative amount of fragment species are compared for five different IgGs (IgG1-5) with widely varying solution properties. Native size-exclusion chromatography (SEC), sodium dodecyl sulfate (SDS)-based SEC, and capillary electrophoresis-SDS were used to characterize IgG1 fragmentation after storage at 30°C, 40°C, and 50°C. Two-dimensional correlation analysis of the chromatograms as a function of time was used to illustrate the relative rates of cleavage. Interestingly, the relative rate of Fab cleavage was greater than that of other species. An average apparent energy of activation for IgG1 fragmentation was also measured for all five molecules. This work suggests that IgG1 fragmentation is primarily hinge sequence dependent and other IgG1 molecules should behave similarly within the limits of the solution conditions used.

Characteristics of rhVEGF Release from Topical Hydrogel Formulations

PurposeTo study recombinant human vascular endothelial growth factor (rhVEGF), the release characteristics from topical gel formulations, and its interaction with the gelling agents.MethodsThe release kinetics were followed by quantifying rhVEGF that diffused into the receptor chamber of Franz cells. Analytical ultracentrifuge (AUC) was used to characterize the sedimentation velocity of rhVEGF experienced in the gel. The interactions were characterized by isothermal calorimetry (ITC), and rhVEGF conformation was assessed by circular dichroism (CD).ResultsThe fraction of protein released was linear with the square root of time. The release rate constants did not show significant change within a wide range of bulk viscosities created by different concentrations of hydroxypropyl methylcellulose (HPMC) or MC gels. Sedimentation velocity determined by AUC generated comparable sedimentation coefficients of protein in these gels. AUC and ITC revealed no significant interaction between rhVEGF and HPMC and some change on secondary structure of the protein by Far UV CD, which was not the case with carboxymethyl cellulose (CMC).ConclusionsMicroviscosity, not bulk viscosity, was the key factor for the release of rhVEGF from cellulosic gels such as HPMC. Interaction between rhVEGF and CMC resulted in slower, and reduced amount of, release from the gel.

Oxidative Degradation of Polysorbate Surfactants Studied by Liquid Chromatography–Mass Spectrometry

Polysorbates (PSs), as acquired from manufacturing processes and chemical nature of fatty acids (FAs) used in production of biotherapeutic formulations, are heterogeneous mixtures of structurally related compounds, covering a wide range of physicochemical properties. Such complexity presents a certain challenge for analysis of these important surfactants and demands the use of methods offering sufficient resolution to monitor individual classes of species and detect changes upon stress. A liquid chromatography mass spectrometry method, benefiting from the use of low m/z marker ions, simplifies profiling of PSs by providing detailed information on FA composition even of chromatographically overlapping peaks. The ability of the method to monitor individual components and follow their changes because of oxidative stress was explored. A water-soluble azo compound was used as a model oxidizer. Major degradation products of PS 80, because of reactions involving double bond, were identified as oxo-C9:0, keto-C18:1, hydroxyl-C18:1, epoxy-C18:0, and hydroperoxy-C18:1. Stability of PS 20 components was found to depend on the carbon number of polyethoxylated (POE) sorbitan FA ester and its order. Rates of oxidative degradation increased with the length of the FA ester and, moreover, POE sorbitan diesters degraded significantly faster in comparison to the corresponding monoesters upon the oxidative stress.

Compatibility of a Protein Topical Gel with Wound Dressings

The compatibility between several dressing materials and a recombinant human vascular endothelial growth factor (rhVEGF) topical methylcellulose gel formulation was investigated. The dressings being studied were Adaptic, Non-stick Dressing, Conformant 2, Opsite and Tegapore. The criteria to select a compatible dressing include protein stability, absence of leachables from the dressing, and ability to retain gel on wound. An LC-MS method with sample treatment using cellulase was developed to determine protein oxidation in gel formulations. Results showed that rhVEGF was significantly oxidized by Adaptic dressing in 24 h. Protein oxidation was likely due to the peroxides, as determined by FOX assay, released into the protein solution from the dressing. Furthermore, Adaptic dressing caused protein adsorption loss, formation of high MW protein adducts, and released leachables as determined by RP-HPLC, LC-MS, and SEC. No protein oxidation or loss was observed after exposure to the other four alternative dressings. However, unknown leachables were detected in the presence of Opsite and Non-stick Dressing. The pore sizes of the Conformant 2 and Non-stick dressings were too large to hold the topical gel within the wound area, making them unsuitable for patient use. No rhVEGF bioactivity loss was observed in the presence of Tegapore. In conclusion, Tegapore was considered suitable for the rhVEGF topical gel.

Formulation Development for Antibody-Drug Conjugates

Antibody–drug conjugates (ADCs) are complex molecules designed to provide targeted therapy to cancer patients. An ADC is formed commonly by conjugating an antibody with small cytotoxic drugs generally either through lysine e-amino groups to form a lysine-linked ADC or through sulfhydryl groups of reducing interchain cystine. THIOMAB®–drug conjugates (TDCs) are a new subclass of ADCs in which the engineered free cysteine residues at specific sites of the antibody are conjugated with cytotoxins. The majority of ADCs currently in the market and under development contains a common moiety: a thio-succinimide linker that is susceptible to hydrolysis of succinimide and cleavage of the thioether bond. ADC contains a heterogeneous mixture of different drug-loaded antibody species, whereas TDC exhibits a more homogeneous distribution of linker drugs. Linker stability, drug load distribution, and drug-to-antibody ratio (DAR) are believed to play critical roles in the efficacy and safety of ADC products. This chapter describes analytical methods and formulation strategies to understand and characterize these critical quality attributes in order to develop a stable formulation for ADC product. The effect of DAR on ADC aggregation is presented. In addition, formulation parameters such as pH and buffers, antioxidants, and surfactants are described. Finally, the advantages and drawbacks of a lyophilized formulation are discussed.