Visible Light Degradation of a Monoclonal Antibody in a High-Concentration Formulation: Characterization of a Tryptophan-Derived Chromophoric Photo-product by Comparison to Photo-degradation of N-Acetyl-l-tryptophan Amide.

We investigated the discoloration of a highly concentrated monoclonal antibody (mAbZ) in sodium acetate (NaAc) and histidine/lysine (His/Lys) buffer after exposure to visible light. The color change of the mAbZ formulation was significantly more intense in NaAc buffer and developed a characteristic absorbance with a λmax of ca. 450 nm. We characterized this photo-chemically generated chromophore by comparison with visible light photo-degradation of a concentrated solution of a model compound for protein Trp residues, N-acetyl-l-tryptophan amide (NATA). The photo-degradation of NATA generated a chromophoric product with a λmax of ca. 450 nm and UV-vis spectroscopic properties identical to those of the product generated from mAbZ. This product was isolated and analyzed by high-performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS) and 1H, 13C, and 1H-13C heteronuclear single-quantum correlation NMR spectroscopy. MS/MS analysis reveals a product characterized by the loss of 33 Da from NATA, referred to as NATA-33. Together, the NMR data suggest that this product may be N-(2,4-dihydrocyclopenta[b]indol-2-yl)acetamide (structure P3a) or a tautomer (P3b-d).

Discovery of a Photoinduced Histidine-Histidine Cross-Link in an IgG4 Antibody.

A novel histidine-histidine (His-His) photooxidative cross-link has been identified in an IgG4 antibody. It was formed between the side chain of a histidine residue of the antibody and histidine from the formulation buffer. The structure of the cross-link was elucidated using high performance liquid chromatography (HPLC) hyphenated to tandem mass spectrometry (MS/MS) with higher energy collisional dissociation (HCD). The cross-link was found in multiple conformations, as the location of the oxygen varied. Furthermore, the extent of cross-link formation was shown to correlate with the amount of light the antibody was exposed to as well as the solvent accessibility of each modification site.

Effect of UVC Irradiation on the Oxidation of Histidine in Monoclonal Antibodies.

We oxidized histidine residues in monoclonal antibody drugs of immunoglobulin gamma 1 (IgG1) using ultraviolet C irradiation (UVC: 200-280 nm), which is known to be potent for sterilization or disinfection. Among the reaction products, we identified asparagine and aspartic acid by mass spectrometry. In the photo-induced oxidation of histidine in angiotensin II, 18O atoms from H218O in the solvent were incorporated only into aspartic acid but not into asparagine. This suggests that UVC irradiation generates singlet oxygen and induces [2 + 2] cycloaddition to form a dioxetane involving the imidazole Cγ - Cδ2 bond of histidine, followed by ring-opening in the manner of further photo-induced retro [2 + 2] cycloaddition. This yields an equilibrium mixture of two keto-imines, which can be the precursors to aspartic acid and asparagine. The photo-oxidation appears to occur preferentially for histidine residues with lower pKa values in IgG1. We thus conclude that the damage due to UVC photo-oxidation of histidine residues can be avoided in acidic conditions where the imidazole ring is protonated.

Protein Stability and Photostability under In Vitro Vitreal Conditions - Implications for Long Acting Delivery of Protein Therapeutics for Ocular Disease.

PURPOSE: To evaluate the stability of a model Mab1 and Fab1 under in vitro vitreal conditions in the presence of various metabolites and in the presence of light at λ > 400 nM. METHODS: A full length IgG1 monoclonal antibody (Mab1) and a fab fragment (Fab1) were formulated with various metabolites typically found in the vitreous humor and subjected to visible light treatment. Both proteins were analyzed using a variety of biochemical techniques. Furthermore, Fab1 was also tested for antigen binding ability using surface plasmon resonance. RESULTS: Our data shows that some vitreal metabolites such as riboflavin and ascorbic acid affect protein stability, via formation of reactive oxygen species (ROS) and advanced glycation end products (AGE) s respectively. In contrast, metabolites such as glutathione may protect these proteins from light-induced degradation to some extent. CONCLUSIONS: Ascorbic acid and riboflavin were found to photosensitize therapeutic proteins especially when exposed to light. Ascorbic acid reacted with proteins even in the absence of light. Antioxidants such as glutathione helped limit photooxidation under ambient or blue light exposure. Since antioxidant capacity in the eye decreases with age we recommend understanding long term stability, including photooxidation and photosensitization, of new candidate proteins in the context of controlled or sustained release technologies for ocular diseases.

Visible photorelease of liquid biopsy markers following microfluidic affinity-enrichment.

We detail a heterobifunctional, 7-aminocoumarin photocleavable (PC) linker with unique properties to covalently attach Abs to surfaces and subsequently release them with visible light (400-450 nm). The PC linker allowed rapid (2 min) and efficient (>90%) release of CTCs and EVs without damaging their molecular cargo.

Optical Control of Antibody Activity by Using Photocleavable Bivalent Peptide-DNA Locks.

Antibody-based molecular recognition plays a central role in today's life sciences, ranging from immunoassays to molecular imaging and antibody-based therapeutics. Control over antibody activity by using external triggers such as light could further increase the specificity of antibody-based targeting. Here we present bivalent peptide-DNA ligands containing photocleavable linkers as a noncovalent approach by which to allow photoactivation of antibody activity. Light-triggered cleavage of the 3-amino-3-(2-nitrophenyl)propionic acid peptide linker converted the high-affinity bivalent peptide-DNA lock into weakly binding monovalent ligands, effectively restoring antibody targeting of cell-surface receptors. In this work, a proof of principle was provided with an anti-hemagglutinin antibody, but the molecular design of the lock is generic and applicable to any monoclonal antibody for which an epitope or mimotope of sufficient affinity is available.

In-Use Photostability Practice and Regulatory Evaluation for Pharmaceutical Products in an Age of Light-Emitting Diode Light Sources.

This article describes how the increased use of energy-efficient solid-state light sources (e.g., light-emitting diode [LED]-based illumination) in hospitals, pharmacies, and at home can help alleviate concerns of photodegradation for pharmaceuticals. LED light sources, unlike fluorescent ones, do not have spurious spectral contributions <400 nm. Because photostability is primarily evaluated in the International Council of Harmonization Q1B tests with older fluorescent bulb standards (International Organization for Standardization 10977), the amount of photodegradation observed can over-predict what happens in reality, as products are increasingly being stored and used in environments fitted with LED bulbs. Because photodegradation is premised on light absorption by a compound of interest (or a photosensitizer), one can use the overlap between the spectral distribution of a light source and the absorption spectra of a given compound to estimate if photodegradation is a possibility. Based on the absorption spectra of a sample of 150 pharmaceutical compounds in development, only 15% would meet the required overlap to be a candidate to undergo direct photodegradation in the presence of LED lights, against a baseline of 55% of compounds that would, when considering regular fluorescent lights. Biological drug products such as peptides and monoclonal antibodies are also expected to benefit from the use of more efficient solid-state lighting.

Identification of D-Amino Acids in Light Exposed mAb Formulations.

PURPOSE: We previously demonstrated that D-amino acids can form as a result of photo-irradiation of a monoclonal antibody (mAb) at both λ = 254 nm and λ > 295 nm (λmax = 305 nm), likely via reversible hydrogen transfer reactions of intermediary thiyl radicals. Here, we investigate the role of various excipients (sucrose, glucose, L-Arg, L-Met and L-Leu) on D-amino acid formation, and specifically the distribution of D-amino acids in mAb monomers and aggregates present after light exposure. METHODS: The mAb-containing formulations were photo-irradiated at λ = 254 nm and λmax = 305 nm, followed by fractionation of aggregate and monomer fractions using size exclusion chromatography. These aggregate and monomer fractions were subjected to hydrolysis and subsequent amino acid analysis. RESULTS: Both aggregate and monomer fractions collected from all formulations showed the formation of D-Glu and D-Val, whereas the formation of D-Ala was limited to the aggregate fraction collected from an L-Arg-containing formulation. Interestingly, quantitative analysis revealed higher yields of D-amino acids in the L-Arg-containing formulation. CONCLUSIONS: Generally, D-amino acids accumulated to similar extents in monomers and aggregates.

Effect of photo-degradation on the structure, stability, aggregation, and function of an IgG1 monoclonal antibody.

Photostability testing of therapeutic proteins is a critical requirement in the development of biologics. Upon exposure to light, pharmaceutical proteins may undergo a change in structure, stability, and functional properties that could have a potential impact on safety and efficacy. In this work, we studied how exposure to light, according to ICH guidelines, leads to photo-oxidation of a therapeutic IgG1 mAb. We also tested the ability of five different excipients to prevent such oxidation. In samples that were exposed to light, we found that the CH2 domain was considerably destabilized but there were no major changes in the overall structure of the protein. Aggregation of the protein was observed because of light exposure. Mass spectrometry identified that light exposure oxidizes two key methionine residues in the Fc region of the protein. In terms of function, a loss in binding to the neonatal Fc receptor, decreased antibody-dependent cell-mediated cytotoxicity and cell proliferation activities of the protein were seen. Combined analysis of the photo-oxidation effects on the structure, stability, aggregation, and function of the mAb has identified the underlying unifying mechanism. Among the sugars and amino acids tested, methionine was the most effective in protecting mAb against photo-oxidation.

Effect of Surfactants on Mechanical, Thermal, and Photostability of a Monoclonal Antibody.

The purpose of this work was to evaluate the effect of commonly used surfactants (at 0.01% w/v concentration) on mechanical, thermal, and photostability of a monoclonal antibody (MAb1) of IgG1 sub-class and to evaluate the minimum concentration of surfactant (Polysorbate 80) required in protecting MAb1 from mechanical stress. Surfactants evaluated were non-ionic surfactants, Polysorbate 80, Polysorbate 20, Pluronic F-68 (polyoxyethylene-polyoxypropylene block polymer), Brij 35 (polyoxyethylene lauryl ether), Triton X-100, and an anionic surfactant, Caprylic acid (1-Heptanecarboxylic acid). After evaluating effect of surfactants and determining stabilizing effect of Polysorbate 80 against mechanical stress without compromising thermal and photostability of MAb1, the minimum concentration of Polysorbate 80 required for mechanical stability was further examined. Polysorbate 80 concentration was varied from 0 to 0.02%. Mechanical stability was evaluated by agitation of MAb1 at 300 rotations per minute at room temperature for 72 h. Samples were analyzed for purity by SEC-HPLC, turbidity by absorbance at 350 nm, visible particles by visual inspection, and sub-visible particles by light obscuration technique on a particle analyzer. All non-ionic surfactants tested showed a similar effect in protecting against mechanical stress and did not exhibit any significant negative effect on thermal and photostability. However, Caprylic acid had a slightly negative effect on mechanical and photostability when compared to the non-ionic surfactants or sample without surfactant. This work demonstrated that polysorbate 80 is better than other surfactants tested and that a concentration of at least 0.005% (w/v) Polysorbate 80 is needed to protect MAb1 against mechanical stress.

Fosfatasa alcalina ósea sérica elevada no mediada por metástasis en un paciente con cáncer renal / Elevated bone alkaline phosphatase not mediated by metastasis in a patient with renal cancer

Presentamos un paciente de 63 años con cáncer renal y aumento de fosfatasa alcalina sérica de tipo óseo de acuerdo con su reactividad con anticuerpos monoclonales específicos. Se descartaron las causas conocidas de aumento de la isoenzima, incluyendo metástasis óseas. Los niveles enzimáticos cayeron abruptamente con la remoción del tumor, por lo que consideramos a este último como su origen. Diversas isoenzimas de fosfatasa alcalina pueden ser producidas y secretadas por tumores como manifestación paraneoplásica. El conocimiento de esto puede, en ocasiones, orientarnos hacia la presencia de una neoplasia oculta. Además, los cambios en los niveles séricos de esas isoenzimas pueden ser indicadores de respuesta al tratamiento o de recidiva tumoral. (AU)

A 63-year old man was seen in the outpatient clinic because of renal cancer and elevation in bone alkaline phosphatase measured by monoclonal antibodies assay. Known causes of bone isoenzyme augmentation, including bone metastases, were ruled out. The tumoral origin of the isoenzyme was diagnosed because after removal of the tumor the enzymatic levels fell sharply. Several alkaline phosphatase isoenzymes can be produced and secreted by tumors as a paraneoplasic manifestation and their elevation could be a manifestation of an occult neoplasia. Furthermore the monitoring of their blood levels can be useful means of treatment response and a tool to monitoring recurrence if a sharp decrease after removal of the tumor is observed. (AU)

Effect of ambient light on IgG1 monoclonal antibodies during drug product processing and development.

Photostability studies are standard stress testing conducted during drug product development of various pharmaceutical compounds, including small molecules and proteins. These studies as recommended by ICH Q1B are carried out using no less than 1.2× 10(6)lux-hours in the visible region and no less than 200Wh/m(2) in UV light. However, normal drug product processing is carried out under fluorescent lamps that emit white light almost exclusively in the >400nm region with a small UV quotient. We term these as ambient or mild light conditions. We tested several IgG1 monoclonal antibodies (mAbs 1-5) under these ambient light conditions and compared them to the ICH light conditions. All the mAbs were significantly degraded under the ICH light but several mAbs (mAbs 3-5) were processed without impacting any product quality attributes under ambient or mild light conditions. Interestingly we observed site-specific Trp oxidation in mAb1, while higher aggregation and color change were observed for mAb2 under mild light conditions. The recommended ICH light conditions have a high UV component and hence may not help to rank order photosensitivity under normal protein DP processing conditions.

Sequence-specific formation of d-amino acids in a monoclonal antibody during light exposure.

The photoirradiation of a monoclonal antibody 1 (mAb1) at λ = 254 nm and λmax = 305 nm resulted in the sequence-specific generation of d-Val, d-Tyr, and potentially d-Ala and d-Arg, in the heavy chain sequence [95-101] YCARVVY. d-Amino acid formation is most likely the product of reversible intermediary carbon-centered radical formation at the (α)C-positions of the respective amino acids ((α)C(•) radicals) through the action of Cys thiyl radicals (CysS(•)). The latter can be generated photochemically either through direct homolysis of cystine or through photoinduced electron transfer from Trp and/or Tyr residues. The potential of mAb1 sequences to undergo epimerization was first evaluated through covalent H/D exchange during photoirradiation in D2O, and proteolytic peptides exhibiting deuterium incorporation were monitored by HPLC-MS/MS analysis. Subsequently, mAb1 was photoirradiated in H2O, and peptides, for which deuterium incorporation in D2O had been documented, were purified by HPLC and subjected to hydrolysis and amino acid analysis. Importantly, not all peptide sequences which incorporated deuterium during photoirradiation in D2O also exhibited photoinduced d-amino acid formation. For example, the heavy chain sequence [12-18] VQPGGSL showed significant deuterium incorporation during photoirradiation in D2O, but no photoinduced formation of d-amino acids was detected. Instead this sequence contained ca. 22% d-Val in both a photoirradiated and a control sample. This observation could indicate that d-Val may have been generated either during production and/or storage or during sample preparation. While sample preparation did not lead to the formation of d-Val or other d-amino acids in the control sample for the heavy chain sequence [95-101] YCARVVY, we may have to consider that during hydrolysis N-terminal residues (such as in VQPGGSL) may be more prone to epimerization. We conclude that the photoinduced, radical-dependent formation of d-amino acids requires not only the intermediary formation of a (α)C(•) radical but also sufficient flexibility of the protein domain to allow both pro-chiral faces of the (α)C(•) radical to accept a hydrogen atom.

Effect of ambient light on monoclonal antibody product quality during small-scale mammalian cell culture process in clear glass bioreactors.

During a small-scale cell culture process producing a monoclonal antibody, a larger than expected difference was observed in the charge variants profile of the harvested cell culture fluid (HCCF) between the 2 L and larger scales (e.g., 400 L and 12 kL). Small-scale studies performed at the 2 L scale consistently showed an increase in acidic species when compared with the material made at larger scale. Since the 2 L bioreactors were made of clear transparent glass while the larger scale reactors are made of stainless steel, the effect of ambient laboratory light on cell culture process in 2 L bioreactors as well as handling the HCCF was carefully evaluated. Photoreactions in the 2 L glass bioreactors including light mediated increase in acidic variants in HCCF and formulation buffers were identified and carefully analyzed. While the acidic variants comprised of a mixture of sialylated, reduced disulfide, crosslinked (nonreducible), glycated, and deamidated forms, an increase in the nonreducible forms, deamidation and Met oxidation was predominantly observed under light stress. The monoclonal antibody produced in glass bioreactors that were protected from light behaved similar to the one produced in the larger scale. Our data clearly indicate that care should be taken when glass bioreactors are used in cell culture studies during monoclonal antibody production.

Effect of polysorbate 80 quality on photostability of a monoclonal antibody.

Polysorbate 80 is one of the key components of protein formulations. It primarily inhibits interfacial damage of the protein molecule due to mechanical stress during shipping and handling. However, polysorbate 80 also affects the formulation photostability. Exposure to light of polysorbate 80 aqueous solution results in peroxide generation, which in turn may result in oxidation of the susceptible amino acid residues in the protein molecule. The purpose of this study was to determine if the photostability of our proprietary IgG(1) monoclonal antibody formulation containing polysorbate 80 is affected by the quality (grade/vendor) of polysorbate 80. Following four types of polysorbate 80 were tested: (1) Polysorbate 80 Super-Refined, Mallinckrodt Baker, (2) Polysorbate 80 NF, Mallinckrodt Baker, (3) Polysorbate 80 NF, EMD Chemicals, and (4) Ultra-pure Polysorbate 80 (HX), NOF Corporation. The samples were exposed to light as per ICH guidelines Q1B. The results of the study show that photostability of the antibody formulation is indeed affected by the quality of polysorbate 80. This study underscores the importance of carefully choosing the quality of polysorbate 80 to ensure the robustness of formulation.

Structure of the DNA (6-4) photoproduct dTT(6-4)TT in complex with the 64M-2 antibody Fab fragment implies increased antibody-binding affinity by the flanking nucleotides.

Pyrimidine (6-4) pyrimidone DNA photoproducts produced by ultraviolet light are highly mutagenic and carcinogenic. The crystal structure of the dTT(6-4)TT photoproduct in complex with the Fab fragment of the antibody 64M-2 that is specific for (6-4) photoproducts was determined at 2.4 Šresolution. The dT(6-4)T segment is fully accommodated in the concave binding pocket of the Fab, as observed in the complex of dT(6-4)T with the Fab. The pyrimidine and pyrimidone bases of the dT(6-4)T segment are positioned nearly perpendicularly to each other. The thymidine segments flanking both ends extend away from the dT(6-4)T segment. The 5'-side thymine base is parallel to the side chain of Tyr100iH of the antibody heavy chain and is also involved in electrostatic interactions with Asn30L, Tyr32L and Lys50L of the antibody light chain. The 5'-side and 3'-side phosphate groups exhibit electrostatic interactions with Asn28L and Ser58H, respectively. These interactions with the flanking nucleotides explain why longer oligonucleotides containing dT(6-4)T segments in the centre show higher antibody-binding affinities than the dT(6-4)T ligand.

Denosumab for the treatment of osteoporosis.

Being a connective tissue, bone can increase or decrease its mass through the process of remodeling. Using a discovery in the mid-1980s-that tumor necrosis factor (TNF) could dramatically increase formation of osteoclasts (the cells that break down bone)-researchers at Amgen (Thousand Oaks, CA) discovered a TNF-like molecule that regulated bone resorption. Elevations in the expression of this molecule, receptor activator of nuclear factor-κB ligand (RANKL), can cause excessive bone destruction. A blocking antibody to RANKL named denosumab inhibits osteoclast formation and bone degradation. In a large multicenter clinical trial, known as the FREEDOM trial (Fracture Reduction Evaluation of Denosumab in Osteoporosis Every 6 Months), the effects of denosumab were tested in 60- to 90-year-old women over 3 years. Statistically significant reductions in fracture risk at the vertebral column, hip, and nonvertebral sites were associated with increases in bone mineral density (BMD) and reciprocal decreases in markers of bone resorption. However, the FREEDOM trial did not test the most beneficial use of a resorption blocking drug-to target the rapid bone loss that occurs in late perimenopause and early postmenopause. One adverse effect from denosumab is cellulitis, and research in animals suggests that RANKL/RANK interaction is needed for Langerhans cell (LC) survival in the skin. Further mechanistic and clinical studies on the role of RANKL in the skin are needed.

Molecular mechanism of pulsed-dye laser in treatment of keloids: an in vitro study.

OBJECTIVE: Clinical observations indicate that the irradiation of pulsed-dye laser (PDL) can inhibit keloid growth; however, the mechanism of this process is unknown. The aim of this study was to explore the molecular mechanism of the action of PDL on keloid fibroblasts. METHODS: Twenty patients with keloids were selected for this study. Fibroblasts were harvested from keloid tissue. Cell cycle distribution and apoptosis induction were analyzed by flow cytometry and with an antibody to Fas. The expression of apoptosis-related proteins (Fas, BCL-2, and p53) was measured by flow cytometry. RESULTS: Fibroblasts with laser irradiation and control fibroblasts displayed significant resistance to Fas-mediated apoptosis. Analysis of cell cycle distribution indicated that approximately 64% of control fibroblasts were in the proliferative periods of the cell cycle (G2 to M and S phases). However, most fibroblasts with laser irradiation were in the G0 to G1 phase. Fas and BCL-2 expression did not differ significantly between the 2 groups, but p53 expression was much higher in fibroblasts with laser irradiation than in control fibroblasts. CONCLUSION: It is suggested that differences in cell cycle distribution and p53 protein expression may partly account for the biologic mechanism of 595-nm PDL in treating keloid disease.

The construction and in vitro testing of photo-activatable cancer targeting folated anti-CD3 conjugates.

The construction and in vitro testing of a photo-activatable anti-tumour immuno-regulatory antibody is described. In this 'cloaked' folated anti-CD3 antibody conjugate, the folate portion of the conjugate is free to bind to folate receptor expressing cancer cells, whilst the anti-CD3 activity is effectively rendered inert by a coating of photo-labile 2-nitrobenzyl groups. On irradiation with UV-A light the activity of the anti-CD3 antibody is restored, not only when it is required, but more importantly, only where it is required. The conjugate can then attract killer T-cells to the surface of the tumour cells and kill them. Unirradiated normal tissues, to which the conjugate has been targeted by specific and non-specific binding, remain unharmed. We believe that these 'photo-switchable' conjugates could be used to markedly improve the targeting of the immune response to folate receptor (FR) expressing ovarian and breast cancers whilst minimising the side effects in the rest of the body.

Identification of a single tryptophan residue as critical for binding activity in a humanized monoclonal antibody against respiratory syncytial virus.

We have identified a single tryptophan (Trp) residue responsible for loss of binding and biological activity upon ultraviolet (UV) light irradiation in MEDI-493, a humanized monoclonal antibody (MAb) against respiratory syncytial virus (RSV). This finding provides a better understanding of structure-function relationship in a 150-kDa protein. Irradiation of MEDI-493 with UV light resulted in spectral changes typical of Trp photoproducts and in a progressive loss of MEDI-493 binding and biological activity as measured by ELISA, Biacore, and cell-based assays. Mass spectrometric characterization of the proteolytic peptides generated from the UV irradiated MEDI-493 confirmed that most methionine (Met) and a few Trp residues were oxidized to various extents upon exposure to UV light. Among Trp residues, only Trp-105, containing the most solvent-exposed indole moiety in MEDI-493 and residing in a complementary-determining region (CDR) of the heavy chain, was significantly oxidized. When bound to a synthetic antigenic peptide, MEDI-493 showed significant resistance toward binding activity loss during UV irradiation. A second MAb (MEDI-524) with Trp-105 replaced by phenylalanine (Phe) showed a similar pattern of Met oxidation, but no loss of binding and biological activity following irradiation. Treatment of both MAbs with Met- and Trp-specific oxidizing reagents showed that oxidation of Trp-105 correlated with the activity loss, whereas Met oxidation did not affect the activity. These results demonstrate that Trp-105 in MEDI-493 is responsible for the UV light-induced effects.