Characterization of recombinant human monoclonal tissue necrosis factor-alpha antibody using cation-exchange HPLC and capillary isoelectric focusing

Mass spectrometry for structural characterization of therapeutic antibodies

Antibodies, also known as immunoglobulins, have emerged as one of the most promising classes of therapeutics in the biopharmaceutical industry. The need for complete characterization of the quality attributes of these molecules requires sophisticated techniques. Mass spectrometry (MS) has become an essential analytical tool for the structural characterization of therapeutic antibodies, due to its superior resolution over other analytical techniques. It has been widely used in virtually all phases of antibody development. Structural features determined by MS include amino acid sequence, disulfide linkages, carbohydrate structure and profile, and many different post-translational, in-process, and in-storage modifications. In this review, we will discuss various MS-based techniques for the structural characterization of monoclonal antibodies. These techniques are categorized as mass determination of intact antibodies, and as middle-up, bottom-up, top-down, and middle-down structural characterizations. Each of these techniques has its advantages and disadvantages in terms of structural resolution, sequence coverage, sample consumption, and effort required for analyses. The role of MS in glycan structural characterization and profiling will also be discussed.

Heterogeneity of Monoclonal Antibodies

Heterogeneity of monoclonal antibodies is common due to the various modifications introduced over the lifespan of the molecules from the point of synthesis to the point of complete clearance from the subjects. The vast number of modifications presents great challenge to the thorough characterization of the molecules. This article reviews the current knowledge of enzymatic and nonenzymatic modifications of monoclonal antibodies including the common ones such as incomplete disulfide bond formation, glycosylation, N-terminal pyroglutamine cyclization, C-terminal lysine processing, deamidation, isomerization, and oxidation, and less common ones such as modification of the N-terminal amino acids by maleuric acid and amidation of the C-terminal amino acid. In addition, noncovalent associations with other molecules, conformational diversity and aggregation of monoclonal antibodies are also discussed. Through a complete understanding of the heterogeneity of monoclonal antibodies, strategies can be employed to better identify the potential modifications and thoroughly characterize the molecules.

Characterization of the glycosylation state of a recombinant monoclonal antibody using weak cation exchange chromatography and mass spectrometry

Recombinant monoclonal antibody heterogeneity is inherent due to various enzymatic and non-enzymatic modifications. In this study, a recombinant humanized monoclonal IgG1 antibody with different states of glycosylation on the conserved asparagine residue in the CH(2) domain was analyzed by weak cation exchange chromatography. Two major peaks were observed and were further characterized by enzymatic digestion and mass spectrometry. It was found that this recombinant monoclonal antibody contained three glycosylation states of antibody with zero, one or two glycosylated heavy chains. The peak that eluted earlier on the cation exchange column contained antibodies with two glycosylated heavy chains containing fucosylated biantennary complex oligosaccharides with zero, one or two terminal galactose residues. The peak that eluted later from the column contained antibodies with either zero, one or two glycosylated heavy chains. The oligosaccharide on the antibodies eluted in the later peak was composed of only two GlcNAc residues. These results indicate that conformational changes in large proteins such as monoclonal antibodies, caused by different types of neutral oligosaccharides as well as the absence of oligosaccharides, can be differentiated by cation exchange column chromatography.

Adalimumab for rheumatoid arthritis

In the last few years significant advances have been made in our understanding of the molecular mechanisms underlying rheumatoid arthritis pathogenesis. Pro-inflammatory cytokines, such as TNF-alpha, play a pivotal role in its pathogenesis. Anti-TNF-alpha biological agents are considered a major advance in the treatment of rheumatoid arthritis. Adalimumab is a fully human monoclonal antibody that binds specifically to TNF-alpha, thereby neutralising its activity. It had significant efficacy in well-designed, placebo-controlled trials in patients suffering from rheumatoid arthritis, both as monotherapy and in combination with various disease-modifying antirheumatic drugs, including methotrexate. Adalimumab was generally well tolerated during both concomitant therapy with methotrexate or standard antirheumatic therapy and monotherapy. In addition, the radiographic progression of structural joint damage was significantly inhibited by adalimumab and improved quality of life. This review summarises the recent available data.

Evaluation of the iCE280 Analyzer as a potential high-throughput tool for formulation development

The iCE280 Analyzer (iCE280) was evaluated for its potential application as a high-throughput tool to determine pI and separate charge related species using glycosylated, non-glycosylated and pegylated protein therapeutics as models. Resolution was achieved for glycosylated and non-glycosylated molecules, but remained a challenge for pegylated proteins. The sources of charge variants were determined to be the presence of C-terminal lysine residues, sialic acid content, and deamidation. Limited assay performance evaluation demonstrated that the method was linear in the concentration range of 2-333 microg/ml of IgG with linear regression coefficients of 0.984, 0.998, and 0.990 for acidic, main and basic species, respectively. Limit of detection and limit of quantitation were determined to be 3 and 11 microg/ml. The R.S.D. for intra- and inter-day precision as well as reproducibility was determined to be 0.2% or less for all pI values and 1.4% or less for acidic and main peak area distribution; the R.S.D. for basic peak area distribution was 5.7% or less. Robustness testing was performed by deliberately deviating +/-50% of pharmalyte concentration away from the desired condition. This deviation revealed a pI shift of only 0.06 units and resulted in no significant impact on area percent distribution. Utilization of iCE280 Analyzer eliminated the mobilization step associated with traditional capillary isoelectric focusing analysis and increased analytical throughput at least 2-fold.

Cation exchange–HPLC and mass spectrometry reveal C-terminal amidation of an IgG1 heavy chain

A unique, late-eluting "basic peak" (relative to the "main peak") was observed by weak cation exchange-HPLC (WCX) for a recombinant monoclonal antibody (mAb) sample. Peak fractions were collected, desalted, and analyzed by high-resolution MS using a top-down characterization approach that provided accurate masses of intact mAb charge isoforms and a comprehensive profile of the structural heterogeneity. The individual light (L) and heavy (H) chain subunits from the main and basic peaks were analyzed by reversed-phase (RP) HPLC/MS after disulfide bond reduction and cysteine alkylation. Three mAb isoforms were detected, and their modifications were localized to H chain. Bottom-up characterization using RP-HPLC/MS peptide mapping and accurate mass measurements identified three distinct H chain C-terminal peptides ending in glycine, lysine, or alpha-amidated proline. The combined analyses showed that the main WCX peak mAb isoform contained two unmodified L chains and two H chains terminating in glycine. Each mAb isoform that coeluted in the basic peak consisted of two unmodified L chain subunits and a single H chain ending in glycine, but the second H chain terminated in lysine for one isoform and alpha-amidated proline for another isoform. The WCX elution positions of the isoforms were consistent with their respective net charge. To the best of our knowledge, the occurrence of C-terminal alpha-amidation in mAbs has not been reported previously.

Characterization of maleuric acid derivatives on transgenic human monoclonal antibody due to post-secretional modifications in goat milk

A fully human antibody to tumor necrosis factor-alpha was expressed in the mammary glands of transgenic goats. The goat expressed antibody (gAb) is heterogeneous and has several isoforms due to typical cellular post-translational modifications. In addition, one post-secretional modification on gAb was discovered by high-resolution cation exchange chromatography (CIEX). The presence of these variants in the final product was shown to be dependent upon the initial milk storage and traditional purification methodologies used. These observations allow for the development of new sample recovery and purification processes to eliminate these variants. Various enzymatic treatments were used to characterize different gAb heavy chain C-terminal lysine and sialic acid variants. In addition, an unknown derivative with the additional mass of 140 Da was found in transgenic gAb using mass spectrometry (MS). The modification sites were identified as the N-termini of gAb light chains and heavy chains using Q-TOF MS. Characterization of transgenic gAb isoforms was facilitated by utilizing different enzymes, CIEX and MS techniques. A maleuric acid modification on the N-terminal portion of gAb was shown to be consistent with the available data characterizing this new derivative of transgenic gAb isoforms in goat milk.

Characterization by liquid chromatography combined with mass spectrometry of monoclonal anti-IGF-1 receptor antibodies produced in CHO and NS0 cells

7H2HM is a new humanized recombinant monoclonal antibody (MAb) directed against insulin-like growth factor-1 receptor and produced in CHO cells. Homogeneity of intact antibody, reduced light and heavy chains, Fab and Fc fragments were investigated by analytical methods based on mass (SDS-PAGE, SEC), charge (IEF, C-IEX) and hydrophobicity differences (RP-HPLC, HIC) and compared side-by-side with A2CHM, produced in NS0 cells. Primary structures and disulfide bridge pairing were analyzed by microsequencing (Edman degradation), mass spectrometry (MALDI-TOF, ES-TOF) and peptide mapping after enzymatic digestion (Trypsin, endoprotease Lys-C, papain). The light chains demonstrated the expected sequences. The heavy chains yielded post-translational modifications previously reported for other recombinant humanized or human IgG1 such as N-terminal pyroglutamic acid, C-terminal lysine clipping and N-glycosylation for asparagine 297. More surprisingly, two-thirds of the 7H2HM heavy chains were shown to contain an additional 24-amino-acid sequence, corresponding to the translation of an intron located between the variable and the constant domains. Taken together these data suggest that 7H2HM is a mixture of three families of antibodies corresponding (i) to the expected structure (17%; 14,9297 Da; 1330 amino acids), (ii) a variant with a translated intron in one heavy chains (33%; 15,2878 Da; 1354 amino acids) and (iii) a variant with translated introns in two heavy chains (50%; 15,4459 Da; 1378 amino acids), respectively. RP-HPLC is not a commonly used chromatographic method to assess purity of monoclonal antibodies but unlike to SEC and SDS-PAGE, was able to show and to quantify the family of structures present in 7H2HM, which were also identified by peptide mapping, mass spectrometry and microsequencing.

Structural Characterization of a Recombinant Monoclonal Antibody by Electrospray Time-of-Flight Mass Spectrometry

PURPOSE

The aim of this study was to perform structural characterization of a recombinant monoclonal antibody (MAb), huN901, by electrospray time-of-flight mass spectrometry (ESI-TOFMS) using both "top-down" and "bottom-up" approaches.

METHODS

In the top-down approach, the molecular masses of the deglycosylated huN901 and the light and heavy chains of the antibody were measured by direct infusion MS and liquid chromatography-mass spectrometry (LC-MS). In the bottom-up approach, trypsin and Asp-N protease were used to digest the separated, reduced and alkylated light and heavy chains followed by LC-MS analysis of the digests.

RESULTS

The primary structure and post-translational modifications of huN901 were characterized by both top-down and bottom-up MS approaches. Modifications of N-terminal pyroglutamate formation, cleavage of C-terminal lysine, glycosylation, and deamidation were identified in the antibody heavy chain by both protein mass measurement and peptide mapping. No modifications were found in the complementarity determining regions (CDRs) of both chains. Both trypsin and Asp-N protease digestion had an average sequence recovery of 97%, and generated complimentary mapping results with complete sequence recovery.

CONCLUSIONS

ESI-TOFMS is a superior tool to characterize MAb and other complex protein pharmaceuticals.

Biology of tumor necrosis factor-alpha- implications for psoriasis

Numerous recent investigations have pointed to a key role of the proinflammatory, pleiotropic cytokine tumor necrosis factor-alpha (TNF-alpha) in host defense and inflammatory processes. TNF overexpression has been found in lesional skin and in the circulation of psoriatic patients, and it was suggested that TNF-alpha is crucial in this and other immune diseases. Several approaches to inhibit TNF-alpha activity have been developed. These include three different neutralizing antibodies to TNF-alpha as well as three different soluble TNF-alpha receptors with characteristic properties designed to bind the 17-KDa soluble trimeric TNF-alpha and the 26-KDa membrane-bound form of TNF-alpha. Clinical trials have demonstrated significant antipsoriatic effects, and it is likely that blocking TNF-alpha will become an important therapeutic option. The data available from these trials contribute to further understanding of the disease by demonstrating the major role of TNF-alpha. An in-depth understanding of the regulation of TNF gene expression, protein production, receptor expression, and signaling pathways may lead to further, potentially important novel therapeutic strategies and antipsoriatic active small molecules, suitable for oral application in the future. Here we review the current knowledge of TNF biology, the approaches to inhibit TNF activity, and their clinical and immunological effects in psoriasis. In addition, the host-defense effects and chronic TNF-blocking activity are discussed.

Novel ion chromatographic stationary phases for the analysis of complex matrices

Ion chromatography (IC) has a proven track record in the determination of inorganic and organic anions and cations in complex matrices. Recently, application of IC to the separation and determination of bio-molecules such as amino acids, carbohydrates, nucleotides, proteins and peptides has also received much attention. The key to the determination of all of the above species in the most analytically challenging complex matrices is the ability to manipulate selectivity through control of stationary phase chemistry, mobile phase chemistry and the choice of detection method. This Tutorial Review summarises some of the most significant recent advances made in IC stationary phase technology. In particular, the review details stationary phases specifically designed for ion analysis in complex sample matrices, and considers in which direction future stationary phase development might proceed.

Efficacy and safety of the fully human anti-tumour necrosis factor alpha monoclonal antibody adalimumab (D2E7) in DMARD refractory patients with rheumatoid arthritis: a 12 week, phase II study

OBJECTIVES

To evaluate efficacy, dose response, safety, and tolerability of adalimumab (D2E7) in disease modifying antirheumatic drug (DMARD) refractory patients with longstanding, active rheumatoid arthritis (RA).

METHODS

During a 12 week, double blind, placebo controlled study, 284 patients were randomly allocated to receive weekly subcutaneous injections of adalimumab 20 mg (n = 72), 40 mg (n = 70), or 80 mg (n = 72) or placebo (n = 70) without concomitant DMARDs.

RESULTS

Adalimumab significantly improved the signs and symptoms of RA for all efficacy measures. ACR20 responses with adalimumab were significant at each assessment versus placebo (p</=0.01). Additionally, ACR responses with adalimumab were achieved more rapidly than with placebo, with 82/115 (71%) of the ultimate ACR20 response rate to adalimumab treatment achieved at week 2. At week 12, for adalimumab 20, 40, and 80 mg, ACR20 response rates were 50.7%, 57.1%, and 54.2%, respectively, versus 10.0% for placebo (p</=0.001 for all comparisons); ACR50 rates were 23.9%, 27.1%, and 19.4%, respectively, versus 1.4% for placebo (p</=0.001 for all comparisons); and ACR70 rates were 11.3%, 10.0%, and 8.3%, respectively, versus 0.0% for placebo (p</=0.05 for all comparisons). All adalimumab doses significantly improved all ACR core criteria at all assessments. The 40 mg and 80 mg doses provided similar benefit. Adalimumab at all doses was generally well tolerated, with only mild or moderate adverse events. Completion rates were 87% for adalimumab and 67% for placebo.

CONCLUSIONS

Adalimumab given as monotreatment to patients with longstanding, severe RA refractory to traditional DMARDs produced a rapid, sustained response and was safe and well tolerated, with no dose limiting side effects.

Adalimumab

Adalimumab (Humira) is a recombinant, fully human IgG1 monoclonal antibody that binds specifically to tumor necrosis factor (TNF)-alpha, thereby neutralizing the activity of the cytokine. Subcutaneous adalimumab has been investigated in well designed trials in patients with active rheumatoid arthritis despite treatment with disease-modifying antirheumatic drugs (DMARDs). Patients receiving adalimumab 40mg every other week in combination with methotrexate (Anti-TNF Research Study Program of the Monoclonal Antibody Adalimumab [ARMADA] and DE019 trials) or standard antirheumatic therapy (Safety Trial of Adalimumab in Rheumatoid Arthritis [STAR] trial) for 24-52 weeks had significantly higher American College of Rheumatology (ACR) 20, ACR50, and ACR70 response rates than patients receiving placebo plus methotrexate or standard antirheumatic therapy. In ARMADA, an ACR20 response was achieved in 25%, 52%, and 67% of adalimumab plus methotrexate recipients at weeks 1, 4, and 24, respectively. In ARMADA and DE019, improvements in the individual components of the ACR response were significantly greater with adalimumab 40mg every other week plus methotrexate than with placebo plus methotrexate. Monotherapy with adalimumab 40mg every other week was associated with significantly higher ACR20, ACR50, and ACR70 response rates than placebo, as well as significantly greater improvements in the individual components of the ACR response. ACR responses were sustained with adalimumab according to the results of extension studies in which patients received adalimumab in combination with methotrexate (up to 30 months) or as monotherapy (up to 5 years). In both concomitant therapy and monotherapy trials, adalimumab was associated with significantly greater improvements from baseline in health-related quality of life (HR-QOL) measures than placebo; adalimumab also retarded the radiographic progression of structural joint damage to a significant extent compared with placebo. Adalimumab was generally well tolerated as both concomitant therapy and monotherapy. In ARMADA, there were no significant differences between adalimumab and placebo (in combination with methotrexate) in the incidence of adverse events; however, in STAR, the incidence of injection site reactions, rash, and back pain was significantly higher with adalimumab than with placebo (in combination with standard antirheumatic therapy). No cases of tuberculosis were reported in either trial.In conclusion, subcutaneous adalimumab in combination with methotrexate or standard antirheumatic therapy, or as monotherapy, is effective in the treatment of adults with active rheumatoid arthritis who have had an inadequate response to DMARDs. Adalimumab has a rapid onset of action and sustained efficacy. The drug also retards the progression of structural joint damage, improves HR-QOL, and is generally well tolerated. Thus, adalimumab is a valuable new option for the treatment of DMARD-refractory adult rheumatoid arthritis.

Scintigraphic detection of tumour necrosis factor in patients with rheumatoid arthritis

OBJECTIVES

To investigate the biodistribution and specific targeting for tumour necrosis factor (TNF) of a fully human, radiolabelled anti-TNF monoclonal antibody (anti-TNF mAb) in patients with active rheumatoid arthritis (RA). To assess whether this agent is suitable for visualisation of synovitis.

METHODS

Ten patients with RA underwent whole body scintigraphy after administration of a tracer-subtherapeutic dose of 100 microg (99m)Tc human anti-TNF mAb. After two weeks, the procedure was repeated to assess the specificity of the radiolabelled antibody for TNF and its sensitivity for changes in inflammation. Therefore, a competition study was performed in five patients, who received excess unlabelled anti-TNF mAb before the tracer dose of (99m)Tc-anti-TNF. Another five patients received 120 mg methylprednisolone two days before the second scintigraphy.

RESULTS

Radiolabelled anti-TNF mAb allowed clear visualisation of inflamed joints in patients with active RA with a high specificity. Concomitant administration of excess unlabelled anti-TNF reduced the joint uptake of (99m)Tc-anti-TNF mAb by a median of 25% as a percentage of the injected dose after 24 hours, whereas uptake in liver and spleen remained unchanged. Systemic corticosteroids reduced the disease activity, which was mirrored by a decreased joint uptake of the tracer. The anti-TNF mAb retained its high affinity for TNF alpha after labelling and was cleared from the circulation with an elimination half life of 48 hours. The procedure was well tolerated.

CONCLUSIONS

Radiolabelled human anti-TNF mAb allows visualisation of synovitis in patients with RA. Joint accumulation of this agent is partly due to specific TNF targeting and is highly predictive for inflammation.

Characterization of noncovalent complexes of recombinant human monoclonal antibody and antigen using cation exchange, size exclusion chromatography, and BIAcore

The binding of fully human monoclonal antibodies (MAbs) D2E7 and 2SD4 to their antigen, human tumor necrosis factor-alpha (TNFalpha), was investigated by BIAcore, cation exchange (CIEX), and size exclusion liquid chromatography (SEC) using ultraviolet and laser light scattering detectors. D2E7 has a higher affinity for TNFalpha than 2SD4 and the two antibodies (Abs) differ by 12 amino acids in the antigen (Ag) binding regions. A BIAcore biosensor instrument was used to determine the association, k(on) and dissociation, k(off), rate constants for the binding of TNFalpha to D2E7 and 2SD4. The HPLC methods were used to resolve and to study D2E7, 2SD4, and TNFalpha molecules and the noncovalent complexes of D2E7 and 2SD4 with TNFalpha. The CIEX method demonstrated that all D2E7 charged-variants bound TNFalpha equally well. There was no preferential binding for any one of D2E7 charged-variants to TNFalpha. D2E7 and 2SD4 Abs were resolved by the CIEX method. When a mixture of D2E7 and 2SD4 was mixed with excess TNFalpha, D2E7. TNFalpha complexes were formed before any 2SD4. TNFalpha complexes. Thus, the CIEX method was able to rank the affinities of the MAbs. D2E7 and TNFalpha formed complexes of 600-5000 kDa. The molecular weights of various D2E7. TNFalpha complexes were determined by a SEC method with light scattering (LS) and refractive index (RI) detectors. Upon overnight incubation, a 598-kDa complex emerged as the most stable and the only D2E7. TNFalpha complex. The molar ratio of D2E7 to TNFalpha in this complex was approximately 1:1. Based on molecular weights and the molar ratio, an immune complex, consisting of alternating three D2E7 and three TNFalpha molecules, is proposed as the most stable complex.

Accuracy in the determination of isoelectric points of some proteins and a peptide by capillary isoelectric focusing: utility of synthetic peptides as isoelectric point markers

To evaluate the accuracy ofisoelectric point determination by capillary isoelectric focusing, the pI values of nine proteins and a peptide, the pI values of which had been determined by other methods and ranging pI 3.55-9.60, were determined by capillary isoelectric focusing by cofocusing of recently developed peptide pI markers ranging 3.38-10.17, and the consistency of the pI values was examined. Isoelectric focusing was carried out in neutral polymer-coated capillaries, and the pH gradient was mobilized by pressure toward the cathode, to detect samples with absorption at 280 nm at a fixed detection point. Carrier ampholytes from two different suppliers and in different pH ranges were used. The sharp peaks of the highly pure peptide pI markers greatly facilitated the unambiguous identification of the peaks. When a carrier ampholyte ranging over the acidic side was used, the detection of acidic pI samples was anomalously delayed. This could be partly mitigated by reducing the viscosity of the anode solution in comparison with the pH gradient formed in the capillary. Since the detection times vs the pH relationships were not linear in most cases, the use of a linear calibration line over an entire pH gradient would be erroneous. Instead, the pI values of samples were calculated by assuming a linear relation for pH against detection time between two flanking marker peptides. Close agreement between the pI values, determined by capillary isoelectric focusing, and the reference values of the samples was observed within an average difference range of 0.04-0.08 pH unit with a sample consumption of 10-100 ng within 30-60 min. Some carrier ampholytes were preferentially more effective at either the acidic or the basic side of the pH gradient. For confirmation of the completion of focusing, the use of two different focusing times is recommended.