Table 1.
Characteristics and impact of charge variants in mAbs.
| Feature | Acidic | Main | Basic | Ref. |
|---|---|---|---|---|
| Net Charge | More negative/Lower pI | Expected net charge/pI for the target molecule profile | More positive/Higher pI | Xie et al.44 |
| Chromatographic Profile | Elutes earlier in Cation Exchange Chromatography (CEX)/Migrates towards anode in cIEF | A principal peak in CEX/cIEF; Represents the target elution/migration time | Elutes later in CEX/Migrates towards cathode in cIEF | Beck et al.9 Xie et al.44 |
| Representative PTMs | Deamidation (Asn → Asp/isoAsp) - Sialylation (N-glycans) - Glycation - Trp Oxidation (sometimes) - Arg Modification (e.g., by methylglyoxal) | N-terminal Pyroglutamate Formation - Complete C-terminal Lys Removal - Core/Neutral N-glycosylation (e.g., G0F, G1F) | Incomplete C-term Lys Removal - Incomplete N-term PyroGlu Formation - Succinimide Formation - C-terminal Amidation - Asp Isomerization to isoAsp (sometimes) - Met Oxidation | Brorson and Jia38 Du et al.33 Gangwar et al.32 |
| Key Origin Drivers | High Temperature; High pH (esp. for deamidation); Long culture duration; High glucose/sugar; Oxidative stress (DO, light, certain metals); Nutrient depletion; Cell stress/lysis | Optimal biosynthesis, Efficient enzymatic processing, Controlled process conditions | Suboptimal enzymatic processing (esp. carboxypeptidase, glutaminyl cyclase), Low pH (esp. isoAsp/succinimide), Specific metal ion levels (e.g., Zn/Cu affecting Cp), Cell line-specific enzyme levels | Gangwar et al.29 Ha et al.32 Sissolak et al.36 Weng et al.21 |
| Analytical Detection Methods | CEX, cIEF/iCIEF, LC-MS, Peptide Mapping | CEX, cIEF/iCIEF, LC-MS, Peptide Mapping | CEX, cIEF/iCIEF, LC-MS, Peptide Mapping | Gupta et al.35 Horvath et al.45 Wagner-Rousset et al.15 |
| Stability Profile | Often linked to degradation pathways (deamidation, oxidation); Potential for increased aggregation/fragmentation propensity | Represents target stability profile; Generally stable within specifications | May contain degradation intermediates (succinimide, isoAsp); Can impact conformation/solubility | Hazeltine et al.46 Kaur et al.26 Luo et al.42 Zheng et al.47 |
| Functional Implications | Altered antigen binding (if in CDR), ↓ ADCC/CDC (sialylation), altered PK, immunogenicity (sometimes) | Represents the target activity profile; Benchmark for comparison. | Altered FcRn binding/PK (C-term Lys), potentially altered potency or clearance (conformational variants), immunogenicity (sometimes, e.g., leader seq.) | Chen et al.48 Hong et al.49 Zhang et al.50 Zheng et al.51 |
| Regulatory Perspective | CQA; Must be characterized, monitored, and controlled within justified limits. | Defined as the Reference Standard profile; CQA; Must be characterized, monitored, and controlled within justified limits | CQA; Must be characterized, monitored, and controlled within justified limits | Horvath et al.45 Rouiller et al.52 Xu et al.53 |