Assessing monoclonal antibody product quality attribute criticality through clinical studies

Recombinant therapeutic proteins, including antibodies, contain a variety of chemical and physical modifications. Great effort is expended during process and formulation development in controlling and minimizing this heterogeneity, which may not affect safety or efficacy and, therefore, may not need to be controlled. Many of the chemical conversions also occur in vivo and knowledge about the alterations can be applied to assessment of the potential impact on characteristics and the biological activity of therapeutic proteins. Other attributes may affect the drug clearance and thereby alter drug efficacy. In this review article, we describe attribute studies conducted using clinical samples and how information gleaned from them is applied to attribute criticality assessment. In general, how fast attributes change in vivo compared to the rate of mAb elimination is the key parameter used in these evaluations. An attribute with more rapidly changing levels may have greater potential to affect safety or efficacy and thereby reach the status of a Critical Quality Attribute (CQA) that should be controlled during production and storage, but the effect will depend on whether compositional changes are due to chemical conversion or differential clearance.Key words: quality by design, critical quality attributes, pharmacokinetics, biotransformations, microheterogeneity     

Quantitation and pharmacokinetic modeling of therapeutic antibody quality attributes in human studies

A thorough understanding of drug metabolism and disposition can aid in the assessment of efficacy and safety. However, analytical methods used in pharmacokinetics (PK) studies of protein therapeutics are usually based on ELISA, and therefore can provide a limited perspective on the quality of the drug in concentration measurements. Individual post-translational modifications (PTMs) of protein therapeutics are rarely considered for PK analysis, partly because it is technically difficult to recover and quantify individual protein variants from biological fluids. Meanwhile, PTMs may be directly linked to variations in drug efficacy and safety, and therefore understanding of clearance and metabolism of biopharmaceutical protein variants during clinical studies is an important consideration. To address such challenges, we developed an affinity-purification procedure followed by peptide mapping with mass spectrometric detection, which can profile multiple quality attributes of therapeutic antibodies recovered from patient sera. The obtained data enable quantitative modeling, which allows for simulation of the PK of different individual PTMs or attribute levels in vivo and thus facilitate the assessment of quality attributes impact in vivo. Such information can contribute to the product quality attribute risk assessment during manufacturing process development and inform appropriate process control strategy.     

Assessing in vivo dynamics of multiple quality attributes from a therapeutic IgG4 monoclonal antibody circulating in cynomolgus monkey

Characterization of biopharmaceutical proteins and assessment and understanding of the critical quality attributes (CQAs) is a significant part of biopharmaceutical product development and is routinely performed in vitro. In contrast, systematic analysis of the quality attributes in vivo is not as widespread, although metabolism and clearance of multiple variants of therapeutic proteins administered to non-human primates and human subjects may have a different impact on safety, efficacy and exposure. The major hurdles of such studies are usually sample availability and technical capability. In this study, we used affinity purification coupled with liquid chromatography and mass spectrometric analysis of the digested protein for consistent and simultaneous detection of the full amino acid sequence of a therapeutic IgG4 monoclonal antibody, MAB1. This methodology allowed us to assess in vivo changes of all sequence-related modifications and quality attributes of MAB1 over the duration of a preclinical pharmacokinetic study in cynomolgus monkeys.     

Review physical and chemical aspects of stabilization of compounds in silk

The challenge of stabilization of small molecules and proteins has received considerable interest. The biological activity of small molecules can be lost as a consequence of chemical modifications, while protein activity may be lost due to chemical or structural degradation, such as a change in macromolecular conformation or aggregation. In these cases, stabilization is required to preserve therapeutic and bioactivity efficacy and safety. In addition to use in therapeutic applications, strategies to stabilize small molecules and proteins also have applications in industrial processes, diagnostics, and consumer products like food and cosmetics. Traditionally, therapeutic drug formulation efforts have focused on maintaining stability during product preparation and storage. However, with growing interest in the fields of encapsulation, tissue engineering, and controlled release drug delivery systems, new stabilization challenges are being addressed; the compounds or protein of interest must be stabilized during: (1) fabrication of the protein or small molecule-loaded carrier, (2) device storage, and (3) for the duration of intended release needs in vitro or in vivo. We review common mechanisms of compound degradation for small molecules and proteins during biomaterial preparation (including tissue engineering scaffolds and drug delivery systems), storage, and in vivo implantation. We also review the physical and chemical aspects of polymer-based stabilization approaches, with a particular focus on the stabilizing properties of silk fibroin biomaterials.     

Quality attributes of recombinant therapeutic proteins: an assessment of impact on safety and efficacy as part of a quality by design development approach

Quality by Design (QbD) is a new approach to the development of recombinant therapeutic protein products that promotes a better understanding of the product and its manufacturing process. The first step in the QbD approach consists in identifying the critical quality attributes (CQA), i.e., those quality attributes of the product that have an impact on its clinical efficacy or safety. CQAs are identified through a science-based risk assessment taking into consideration a combination of clinical and nonclinical data obtained with the molecule or other similar molecules or platform products, as well as the published literature. The purpose of this article is to perform a comprehensive review of the published literature, supporting an assessment of the impact on safety and efficacy of the quality attributes commonly encountered in recombinant therapeutic proteins, more specifically those produced in mammalian cell expression systems. Quality attributes generally observed in biopharmaceutical proteins including product-related impurities and substances, process-related impurities, product attributes, and contaminants are evaluated one by one for their impact on biological activity, pharmacokinetics and pharmacodynamics, immunogenicity, and overall safety/toxicity.     

N-terminal glutamate to pyroglutamate conversion in vivo for human IgG2 antibodies

Therapeutic proteins contain a large number of post-translational modifications, some of which could potentially impact their safety or efficacy. In one of these changes, pyroglutamate can form on the N terminus of the polypeptide chain. Both glutamine and glutamate at the N termini of recombinant monoclonal antibodies can cyclize spontaneously to pyroglutamate (pE) in vitro. Glutamate conversion to pyroglutamate occurs more slowly than from glutamine but has been observed under near physiological conditions. Here we investigated to what extent human IgG2 N-terminal glutamate converts to pE in vivo. Pyroglutamate levels increased over time after injection into humans, with the rate of formation differing between polypeptide chains. These changes were replicated for the same antibodies in vitro under physiological pH and temperature conditions, indicating that the changes observed in vivo were due to chemical conversion not differential clearance. Differences in the conversion rates between the light chain and heavy chain on an antibody were eliminated by denaturing the protein, revealing that structural elements affect pE formation rates. By enzymatically releasing pE from endogenous antibodies isolated from human serum, we could estimate the naturally occurring levels of this post-translational modification. Together, these techniques and results can be used to predict the exposure of pE for therapeutic antibodies and to guide criticality assessments for this attribute.     

Modifications of therapeutic proteins: challenges and prospects

The production of therapeutic proteins is one of the fastest growing sectors of the pharmaceutical industry. However, most proteins used in drug therapy require complex post-translational modifications for efficient secretion, drug efficacy and stability. Common protein modifications include variable glycosylation, misfolding and aggregation, oxidation of methionine, deamidation of asparagine and glutamine, and proteolysis. These modifications not only pose challenges for accurate and consistent bioprocessing, but also may have consequences for the patient in that incorrect modifications or aggregation may lead to an immune response to the protein therapeutic. This review provides examples of analytical and preventative advances that have been devised to meet these challenges, and insights into how further advances can improve the efficiency and safety in manufacturing recombinant proteins.     

An automated immunoassay for early specificity profiling of antibodies

Antibody-based therapeutics are of great value for the treatment of human diseases. In addition to functional activity, affinity or physico-chemical properties, antibody specificity is considered to be one of the most crucial attributes for safety and efficacy. Consequently, appropriate studies are required before entering clinical trials.

High content protein arrays are widely applied to assess antibody specificity, but this commercial solution can only be applied to final therapeutic antibody candidates because such arrays are expensive and their throughput is limited. A flexible, high-throughput and economical assay that allows specificity testing of IgG or Fab molecules during early discovery is described here. The 384-well microtiter plate assay contains a comprehensive panel of 32 test proteins and uses electrochemiluminescence as readout.

The Protein Panel Profiling (3P) was used to analyze marketed therapeutic antibodies that all showed highly specific binding profiles. Subsequently, 3P was applied to antibody candidates from early discovery and the results compared well with those obtained with a commercially available high content protein chip. Our results suggest that 3P can be applied as an additional filter for lead selection, allowing the identification of favorable antibody candidates in early discovery and thereby increasing the speed and possibility of success in drug development.     

Tailoring recombinant protein quality by rational media design

Clinical efficacy and safety of recombinant proteins are closely associated with their structural characteristics. The major quality attributes comprise glycosylation, charge variants (oxidation, deamidation, and C‐ & N‐terminal modifications), aggregates, low‐molecular‐weight species (LMW), and misincorporation of amino acids in the protein backbone. Cell culture media design has a great potential to modulate these quality attributes due to the vital role of medium in mammalian cell culture. The purpose of this review is to provide an overview of the way both classical cell culture medium components and novel supplements affect the quality attributes of recombinant therapeutic proteins expressed in mammalian hosts, allowing rational and high‐throughput optimization of mammalian cell culture media. A selection of specific and/or potent inhibitors and activators of oligosaccharide processing as well as components affecting multiple quality attributes are presented. Extensive research efforts in this field show the feasibility of quality engineering through media design, allowing to significantly modulate the protein function. © 2015 American Institute of Chemical Engineers Biotechnol. Prog., 31:615–629, 2015     

蛋白质药物长效化技术的现状和进展

综述了提高蛋白质药物半衰期技术的最新进展。由于蛋白质药物在体内会被快速清除,所以患者必须频繁用药才能保持药物浓度,限制了其治疗效果。因此,延长蛋白质药物体内的半衰期并阻止其被快速清除已成为近年来的研究热点。已建立的提高蛋白质药物半衰期的技术包括化学修饰、蛋白质融合、微囊化、糖基化、抗蛋白酶突变体等,许多长效蛋白质药物已经研制成功并应用于临床治疗。阐述了这些技术的原理并通过实例比较和评价了各种技术的优点和适用范围。     

Perspectives on transdermal ultrasound mediated drug delivery

The use of needles for multiple injection of drugs, such as insulin for diabetes, can be painful. As a result, prescribed drug noncompliance can result in severe medical complications. Several noninvasive methods exist for transdermal drug delivery. These include chemical mediation using liposomes and chemical enhancers or physical mechanisms such as microneedles, iontophoresis, electroporation, and ultrasound. Ultrasound enhanced transdermal drug delivery offers advantages over traditional drug delivery methods which are often invasive and painful. A broad review of the transdermal ultrasound drug delivery literature has shown that this technology offers promising potential for noninvasive drug administration. From a clinical perspective, few drugs, proteins or peptides have been successfully administered transdermally because of the low skin permeability to these relatively large molecules, although much work is underway to resolve this problem. The proposed mechanism of ultrasound has been suggested to be the result of cavitation, which is discussed along with the bioeffects from therapeutic ultrasound. For low frequencies, potential transducers which can be used for drug delivery are discussed, along with cautions regarding ultrasound safety versus efficacy.     

Evaluation of protein disulfide conversion in vitro using a continuous flow dialysis system

Recombinant therapeutic proteins are heterogeneous due to chemical and physical modifications. Understanding the impact of these modifications on drug safety and efficacy is critical for optimal process development and for setting reasonable specification limits. In this study, we describe the development of an in vitro continuous flow dialysis system to evaluate potential in vivo behavior of thiol adducted species and incorrectly disulfide bonded species of therapeutic proteins. The system is capable of maintaining the low-level cysteine concentrations found in human blood. Liabilities of cysteamine adducted species, incorrectly disulfide bonded species, and the correctly disulfide bonded form of an Fc-fusion protein were studied using this system. Results showed that 90% of the cysteamine adduct converted into the correctly disulfide bonded form and incorrectly disulfide bonded species in approximately 4 h under physiological conditions. Approximately 50% of incorrectly disulfide bonded species converted into the correctly bonded form in 2 days. These results provide valuable information on potential in vivo stability of the cysteamine adduct, incorrectly disulfide bonded species, and the correctly bonded form of the Fc-fusion protein. These are important considerations when evaluating the criticality of product quality attributes.     

BET bromodomain proteins are required for glioblastoma cell proliferation

Epigenetic proteins have recently emerged as novel anticancer targets. Among these, bromodomain and extra terminal domain (BET) proteins recognize lysine-acetylated histones, thereby regulating gene expression. Newly described small molecules that inhibit BET proteins BRD2, BRD3, and BRD4 reduce proliferation of NUT (nuclear protein in testis)-midline carcinoma, multiple myeloma, and leukemia cells in vitro and in vivo. These findings prompted us to determine whether BET proteins may be therapeutic targets in the most common primary adult brain tumor, glioblastoma (GBM). We performed NanoString analysis of GBM tumor samples and controls to identify novel therapeutic targets. Several cell proliferation assays of GBM cell lines and stem cells were used to analyze the efficacy of the drug I-BET151 relative to temozolomide (TMZ) or cell cycle inhibitors. Lastly, we performed xenograft experiments to determine the efficacy of I-BET151 in vivo. We demonstrate that BRD2 and BRD4 RNA are significantly overexpressed in GBM, suggesting that BET protein inhibition may be an effective means of reducing GBM cell proliferation. Disruption of BRD4 expression in glioblastoma cells reduced cell cycle progression. Similarly, treatment with the BET protein inhibitor I-BET151 reduced GBM cell proliferation in vitro and in vivo. I-BET151 treatment enriched cells at the G1/S cell cycle transition. Importantly, I-BET151 is as potent at inhibiting GBM cell proliferation as TMZ, the current chemotherapy treatment administered to GBM patients. Since I-BET151 inhibits GBM cell proliferation by arresting cell cycle progression, we propose that BET protein inhibition may be a viable therapeutic option for GBM patients suffering from TMZ resistant tumors.     

The role of HSP27 in the development of drug resistance of gastrointestinal malignancies: Current status and perspectives

Heat-shock protein 27 (HSP27) is a chaperone molecule that plays a critical role in the refolding and activity of several proteins responsible for cancer cell drug toxicity. Upregulation of HSP27 is associated with decreased drug sensitivity as well as poorer survival in gastrointestinal (GI) malignancies. It is, therefore, possible that HSP27 may be of value in the assessment of prognostic and therapeutic efficacy in the treatment of GI cancers. Pharmacological and biological inhibitors of HSP27 enhance tumor cell chemosensitivity. This review summarizes the potential role of HSP27 in chemotherapy drug resistance and the therapeutic potential of HSP27 inhibitors as a novel strategy in the treatment of GI cancers.     

BET bromodomain proteins are required for glioblastoma cell proliferation

Epigenetic proteins have recently emerged as novel anticancer targets. Among these, bromodomain and extra terminal domain (BET) proteins recognize lysine-acetylated histones, thereby regulating gene expression. Newly described small molecules that inhibit BET proteins BRD2, BRD3, and BRD4 reduce proliferation of NUT (nuclear protein in testis)-midline carcinoma, multiple myeloma, and leukemia cells in vitro and in vivo. These findings prompted us to determine whether BET proteins may be therapeutic targets in the most common primary adult brain tumor, glioblastoma (GBM). We performed NanoString analysis of GBM tumor samples and controls to identify novel therapeutic targets. Several cell proliferation assays of GBM cell lines and stem cells were used to analyze the efficacy of the drug I-BET151 relative to temozolomide (TMZ) or cell cycle inhibitors. Lastly, we performed xenograft experiments to determine the efficacy of I-BET151 in vivo. We demonstrate that BRD2 and BRD4 RNA are significantly overexpressed in GBM, suggesting that BET protein inhibition may be an effective means of reducing GBM cell proliferation. Disruption of BRD4 expression in glioblastoma cells reduced cell cycle progression. Similarly, treatment with the BET protein inhibitor I-BET151 reduced GBM cell proliferation in vitro and in vivo. I-BET151 treatment enriched cells at the G1/S cell cycle transition. Importantly, I-BET151 is as potent at inhibiting GBM cell proliferation as TMZ, the current chemotherapy treatment administered to GBM patients. Since I-BET151 inhibits GBM cell proliferation by arresting cell cycle progression, we propose that BET protein inhibition may be a viable therapeutic option for GBM patients suffering from TMZ resistant tumors.     

Development of a quantitative mass spectrometry multi-attribute method for characterization,quality control testing and disposition of biologics

Regulatory agencies have recently recommended a Quality by Design (QbD) approach for the manufacturing of therapeutic molecules. A QbD strategy requires deep understanding at the molecular level of the attributes that are crucial for safety and efficacy and for insuring that the desired quality of the purified protein drug product is met at the end of the manufacturing process. A mass spectrometry (MS)-based approach to simultaneously monitor the extensive array of product quality attributes (PQAs) present on therapeutic molecules has been developed. This multi-attribute method (MAM) uses a combination of high mass accuracy / high resolution MS data generated by Orbitrap technology and automated identification and relative quantification of PQAs with dedicated software (Pinpoint). The MAM has the potential to replace several conventional electrophoretic and chromatographic methods currently used in Quality Control to release therapeutic molecules. The MAM represents an optimized analytical solution to focus on the attributes of the therapeutic molecule essential for function and implement QbD principles across process development, manufacturing and drug disposition.     

Survey of phosphorylation near drug binding sites in the Protein Data Bank (PDB) and their effects

While it is currently estimated that 40 to 50% of eukaryotic proteins are phosphorylated, little is known about the frequency and local effects of phosphorylation near pharmaceutical inhibitor binding sites. In this study, we investigated how frequently phosphorylation may affect the binding of drug inhibitors to target proteins. We examined the 453 non‐redundant structures of soluble mammalian drug target proteins bound to inhibitors currently available in the Protein Data Bank (PDB). We cross‐referenced these structures with phosphorylation data available from the PhosphoSitePlus database. Three hundred twenty‐two of 453 (71%) of drug targets have evidence of phosphorylation that has been validated by multiple methods or labs. For 132 of 453 (29%) of those, the phosphorylation site is within 12 Å of the small molecule‐binding site, where it would likely alter small molecule binding affinity. We propose a framework for distinguishing between drug‐phosphorylation site interactions that are likely to alter the efficacy of drugs versus those that are not. In addition we highlight examples of well‐established drug targets, such as estrogen receptor alpha, for which phosphorylation may affect drug affinity and clinical efficacy. Our data suggest that phosphorylation may affect drug binding and efficacy for a significant fraction of drug target proteins. Proteins 2015; 83:25–36. © 2014 Wiley Periodicals, Inc.     

Aggregates in monoclonal antibody manufacturing processes

Monoclonal antibodies have proved to be a highly successful class of therapeutic products. Large-scale manufacturing of pharmaceutical antibodies is a complex activity that requires considerable effort in both process and analytical development. If a therapeutic protein cannot be stabilized adequately, it will lose partially or totally its therapeutic properties or even cause immunogenic reactions thus potentially further endangering the patients' health. The phenomenon of protein aggregation is a common issue that compromises the quality, safety, and efficacy of antibodies and can happen at different steps of the manufacturing process, including fermentation, purification, final formulation, and storage. Aggregate levels in drug substance and final drug product are a key factor when assessing quality attributes of the molecule, since aggregation might impact biological activity of the biopharmaceutical. In this review it is analyzed how aggregates are formed during monoclonal antibody industrial production, why they have to be removed and the manufacturing process steps that are designed to either minimize or remove aggregates in the final product.     

重组单克隆抗体电荷异质性和工艺调控

重组单克隆抗体药物大多存在翻译后修饰且种类复杂多样,因此研发过程中的质量控制显得尤为重要。其中电荷异质性是关键质量属性,其可能影响生物制品的疗效,甚至有可能带来意想不到的副作用,从而影响药品的安全性和有效性,所以在单抗药物开发过程中需要重点关注并加以调控。单抗药物翻译后修饰是造成电荷异质性的主要原因,因此电荷异质性的控制是生物药物工艺开发的一个重要挑战。梳理了电荷异质性的表征方法,并且根据其分类对能够造成电荷异质性产生的蛋白翻译后修饰进行了总结,同时阐述了不同的电荷异质性对抗体类药物安全性及有效性的影响,最后总结了工艺开发中电荷异质性工艺调控策略的最新进展,以期给生物药物工艺开发及质量研究人员以启示。