Peptide Mapping of Innovator and iosimilar Monoclonal Antibod Using an Agilent 9 Infinit UHPLC Coupled to an Agilent 655 ifunnel Q-TOF LC/MS Sstem Application Note Author Ravindra Gudihal Agilent Technologies India Pvt Ltd Introduction Monoclonal antibodies (mabs) are becoming one of the important classes of biomolecules for the treatment of various cancers. iosimilar mabs, which are the replica of the licensed innovator product in the market are also gaining lots of attention. According to the FDA definition, iosimilars are a tpe of biological product that are licensed (approved) b FDA because the are highl similar to an alread FDA-approved biological product, known as the biological reference product (reference product), and have been shown to have no clinicall meaningful differences from the reference product. The development of these biosimilars is expanding due to the patent expir of innovator drugs. Man biopharmaceutical companies are involved in the manufacturing of these biosimilars, more so in developing countries. LC/MS characterization is a powerful and essential tool to show comparabilit between innovators and biosimilars. To ensure the qualit of biosimilar mabs, and to show molecular similarit with the innovators, their amino acid sequence confirmation is of crucial importance in biosimilar development. Peptide mapping is one of the vital steps to show similarit in the sequence and modifications between an innovator and biosimilar pair. Peptide mapping involves protease digestion of proteins/mabs followed b LC/MS analsis. In this Application Note, commercial Rituximab, a chimeric mouse/human monoclonal antibod (used in the treatment of -cell non-hodgkin lmphomas, rheumatoid arthritis, and chronic lmphoctic leukemia) from innovator and biosimilar was subjected to trpsin digestion followed b peptide separation and mass determination on LC/Q TOF MS. The innovator and biosimilar were compared for sequence similarit, oxidation, and deamidation status.
Experimental Materials Rituximab biosimilar and innovator were purchased from a local pharmac and stored according to manufacturer s instructions. DL-Dithiothreitol (DTT), idoacetamide, Trisbase, and LC/MS grade solvents were purchased from Sigma Aldrich. High qualit sequence grade trpsin was procured from Promega. Trpsin digestion efore the digestion of the mabs with trpsin, the disulfides were reduced and alklated under denaturation conditions. This pretreatment was done to ensure that the ma was completel denatured and soluble so that protease can access its substrate efficientl. The mabs that were in solution were lophilized, and equal concentrations of both were reconstituted in 8 M urea in.5 M Tris buffer, ph 7.6, containing dithiothreitol (DTT). The solutions were then incubated at 37 C for 3 minutes. Iodoacetamide in.5 M Tris buffer, ph 7.6, was added to these solutions, and the sample was incubated at ambient temperature in the dark for 5 minutes. The solutions were diluted with.5 M Tris buffer, ph 7.6, before digestion with trpsin. Trpsin, at a ratio of : (protein to protease w/w) was added to the above pretreated mab solutions. The reaction was kept for overnight incubation at 37 C before LC/MS analsis. The enzmatic activit was quenched b adding µl of % formic acid solution. The samples were either immediatel analzed, or stored at 8 C until LC/MS/MS analsis. Instrumentation LC sstem Agilent 9 Infinit LC Sstem including: Agilent 9 Infinit inar Pump (GA) Agilent 9 Infinit Thermostatted Column Compartment (G36C) Agilent 9 Infinit Autosampler (G6A) LC/MS parameters Parameter Column Sample thermostat 5 C Mobile phase A Mobile phase Agilent 9 Infinit Thermostat (G33) MS sstem Agilent 655 ifunnel Q-TOF LC/MS Sstem with Agilent JetStream Agilent 9 Infinit LC Sstem Agilent Advanceio Peptide Mapping,. 5 mm,.7 μm (p/n 6575-9). % formic acid in water 9 % acetonitrile in water with. % formic acid Gradient (segmented) At minutes & 3 % At minutes & % At minutes & 95 % At minutes & 95 % At. minutes & 3 % Stop time Post time Column temperature 6 C Flow rate Parameter Ion mode Source. minutes minutes.3 ml/min Dring gas temperature 5 C Dring gas flow Agilent 655 Q-TOF LC/MS Sstem Positive ion mode Agilent Dual JetStream L/min Sheath gas temperature 5 C Sheath gas flow Nebulizer Capillar voltage Nozzle L/min 5 psi 3,5 V V MS range m/z 3,7 MS/MS range m/z 5,7 MS scan rate (spectra/second) 6 MS/MS scan rate (spectra/second) 8 Ramped collision energ Data analsis Charge state slope offset 3. 3 and > 3 3.6.8 3.5 6 The data obtained from LC/MS were analzed using Agilent MassHunter Qualitative Analsis Software.7 and Agilent MassHunter ioconfirm Software.7
Results and Discussion Peptide mapping is a regularl emploed technique for evaluating the qualit of antibodies in the pharmaceutical industr. Peptide mapping is regarded as the fingerprint of the protein under analsis. Therefore, it is an excellent technique to compare the similarit between innovator and its biosimilar version. Figure shows the Total Ion Chromatogram (TIC) of trpsin-digested mab obtained using LC/MS for innovator and the biosimilar with Advancedio peptide mapping column. Inspection of the chromatograms reveals peptide peaks with no undigested protein product. The look similar in peak appearance across the chromatogram except for few minor differences. Peptides masses were obtained from the LC/MS run using the Molecular Feature Extraction feature (MFE) of ioconfirm. The masses of peptides obtained were matched with the theoretical digest. The results of MS onl gives 95 % sequence coverage of heav chain, and % for the light chain for trpsin digestion for both antibodies. The great separating power of the Advancedio peptide mapping column maximizes resolution and efficienc. This, in combination with the high analtical sensitivit and high accurac MS, enables a good comparison of the innovator and biosimilar pair. 8 Counts Counts 3 8 3 A Innovator iosimilar 6 8 6 8 6 8 3 3 3 36 38 Acquisition time (min) Figure. Total ion chromatogram (TIC) of peptide digest from Innovator (A) and iosimilar (). 3
To probe the differences between the peptide maps of innovator and biosimilar, a mirror plot of TIC as shown in Figure A was generated using the Compare Files feature of Agilent MassHunter Comparative Analsis software. The mirror plots show certain differences between the peptide maps. As an example in Figure A, a peak around. minutes is prominentl found in the biosimilar, and not in the innovator sample. This peak corresponded to a C-terminal sequence (SLSLSPGK). The abundance of the C-terminal can be attributed to additional charge variants (lsine addition and basic variants) seen in the biosimilar mab, which was reported earlier. The extracted compound chromatogram (EIC) for the peptide (SLSLSPGK) is also shown in Figure. A similar peak around 8.7 minutes (Figure C) corresponds to the des lsine peptide, which is enriched in the innovator. Peptide maps were also used to quantif the extent of oxidation and deamidation, as these are the two most commonl occurring modifications seen during storage, formulation, and sample handling. Oxidation The commonl used DLTMISR peptide sequence from the mab was used to access the degree of oxidation in both the innovator and biosimilar mabs 3. The peptide masses obtained from the MFE analsis from MS-onl data were matched with the theoretical digest with a preferred modification of oxidation included for the theoretical peptide digest. The theoretical digestion list of peptides for the trpsin-digested oxidized mab was generated using the ioconfirm sequence editor (define and match sequences). The relative percentage oxidation in the samples was calculated using Equation. Relative % oxidation = S Height of Met oxi peptide ions (S Height of Met oxi peptide ions) + (S Height of Met non-oxi peptide ions) Equation. 8 A Innovator Counts - iosimilar - Counts Counts 7.5 6-5 6 8 6 8 6 8 3 3 3 36 38 Acquisition time (min) Counts Counts 3 5 C Counts 7.5.3..5.6.7 Acquisition time (min) Counts 3 5 8.6 8.7 8.8 8.9 Acquisition time (min) Figure. Mirror plot of TIC between innovator (red trace) and biosimilar (blue trace) (A). The region at around. minutes is highlighted to show the difference of SLSLSPGK peptide. The EIC of SLSLSPGK peptide, shows that this peptide is enriched in biosmiliar (). Similarl, the peak around 8.7 minutes corresponds to SLSLSPG peptide (lsine truncated). The EIC of SLSLSPG peptide is shown (C), which is enriched in innovator.
From the bar graph (Figure 3A), it can be seen that the biosimilar has relativel more oxidation species compared to the innovator. MS/MS data further confirmed the site of modification on the DLTMISR peptide in both mabs. Figure 3 shows representative MS/MS spectra for DLTMISR peptide in both modified and unmodified peptide derived from the biosimilar sample. Comparison of the ions from the MS/MS spectrum in Figure 3C table for modified and 5 ions shows an increase of ~6 Da over those ions in unmodified peptide, suggesting that oxidation is occurring on the Met position. A 6 5 3 Oxidation (DLTMISR peptide) Innovator iosimilar Relative % oxidation..8 86.95 L,I 375.3 3 56.77 69.36 5 Counts (%) Counts (%).6 89.86.85 5.3. NH3, NH3 3.83.67 5.675. 67.58 35.75 6.355 8.596 565.9 8 6 8 3 36 8 5 56 6 6 Mass-to-charge (m/z). 5.67 375.37 98.83. DLTMISR 3 7.6.8 77.6653 58.695 99.689 38.869.6 635.35 b HO 5 5. 86.966 6.5 7.78 L,I b 9.958 599.337. 86.589 655.67 6 8 6 3 3 38 6 5 5 58 6 66 Mass-to-charge (m/z) C Unmodified peptide Modified peptide Figure 3. ar graph between innovator and biosimilar for percentage of oxidation species in the sample (A). MS/MS spectra between unmodified and modified DLTMISR peptide (). Table showing the fragment ions for unmodified and modified DLTMISR peptide (C). 5
Deamidation Deamidation is an important PTM to stud, as this modification can cause structural and functional changes to the mab. Deamidation is a nonenzmatic chemical reaction in which asparagine residues are converted to isoaspartl and aspartl residues. It can be identified through a LC/MS/MS peptide mapping experiment. The GFYPSDIAVEWESNGQPENNYK peptide sequence (375 396), from the mab heav chain was used for accessing the degree of deamidation in the innovator and biosimilar mab. The relative percentage deamidation of the amino acid was calculated using Equation. From the bar graph (Figure A), it can be seen that both mabs have similar deamidation species, at about 8 %. From the MS/MS experiments, heav chain peptide (375 396), which contains Asn 388, was identified to have undergone the deamidation in both mabs. S Height of Asp dem peptide ions Relative % deamidation = (S Height of Asp dem peptide ions) + (S Height of Asp non-dem peptide ions) Equation. A 8 6 Deamidation ( NGQPENNYK peptide) Innovator iosimilar Relative % deamidation Counts (%) Counts (%)..8.6....8.6.. 5 6.3 S 36.769 Y, 3 HO 59.885 W 5.957 b 76.3555 6 77.397 368.56 b3 38.686 69.63 6 NH3 538.59 575.7567 6 b 6 HO 797.89 3,79.967 9 HO,5.586 5 5 35 5 55 65 75 85 95,5,5,5,35 Mass-to-charge (m/z) 36.76 3 HO,Y 3+ 59.88 W 368.563 38.679 6 b3.3 3 575.56 76.356 6 78.355 b 7 798.3 95.63,5.98 3 85.395 b,6.558 9 b 8 9 9 GFYPSDIAVEWESNGQPENNYK,39.636 b 5 C Unmodified peptide 5 5 35 5 55 65 75 85 95,5,5,5,35 Mass-to-charge (m/z) Modified peptide Figure. ar graph between innovator and biosimilar for percentage of deamidation species in the samples (A). MS/MS spectra of unmodified and modified GFYPSDIAVEWESNGQPENNYK peptide (). MS/MS fragment ions observed for unmodified and modified peptides (C). Peptide GFYPSDIAVEWESNGQPENNYK peptide (C). 6
Figure shows a representative MS/MS spectrum for the GFYPSDIAVEWESNGQPENNYK peptide in both modified and unmodified peptide forms. If we compare the ions from the MS/MS spectrum in Figure C for modified ions from 9 onwards, we can clearl see an increase of ~.98 Da over those ions in unmodified peptide suggesting that deamidation is occurring on the Asn 388 position. Conclusions This Application Note demonstrates peptide mapping of innovator and biosimilar monoclonal antibodies using an Agilent 9 Infinit LC Sstem coupled to an Agilent 655 ifunnel Q-TOF LC/MS Sstem. Peptide mapping was used to compare and find similarities and differences between innovator and biosimilar mabs. References. http://www.fda.gov/drugs/ DevelopmentApprovalProcess/ HowDrugsareDevelopedandApproved/ ApprovalApplications/ TherapeuticiologicApplications/ iosimilars/ucm78.htm. Agilent Technologies, publication number 599 5557EN. 3. Agilent Technologies, publication number 599 8769EN.. Chelius, D.; Rehder, D. S.; ondarenko, P. V. Identification and characterization of deamidation sites in the conserved regions of human immunoglobulin gamma antibodies. Anal Chem. 5, 77, 6 6. Oxidation and deamidation levels between the innovator and biosimilar mabs were assessed b comparing specific peptides. Agilent MassHunter ioconfirm software and Agilent MassHunter Comparative Analsis software provided automated data extraction, sequence matching, PTM identification, and sequence coverage calculation. 7
www.agilent.com/chem For Research Use Onl. Not for use in diagnostic procedures. This information is subject to change without notice. Agilent Technologies, Inc., 6, 7 Published in the USA, November, 7 599-65EN