Application of 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate derivatization for enhanced peptide mapping analysis of non-biological complex drug glatiramer acetate using liquid chromatography/electrospray ionization collision-induced dissociation high-resolution mass spectrometry.

RATIONALE

Glatiramer acetate (GA) (Copaxone®) is a non-biological complex drug (NBCD) comprising random-sequence polymer chains of four amino acids (MW ~ 5-9 kDa) with unknown structure. The characterization of NBCDs by reversed-phase liquid chromatography/mass spectrometry (RPLC/MS) peptide mapping is often impeded by insufficient separation and/or low sensitivity. To overcome this issue, pre-column derivatization of GA peptide digest was used to improve RPLC/MS detectability and to generate a comprehensive peptide profile.

METHODS

Amino groups of peptides generated by trypsin digestion of GA were derivatized using 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate (AQC) reagent. The derivatized mixture of random-sequence peptides was analyzed by liquid chromatography/positive-mode electrospray ionization collision-induced dissociation high-resolution mass spectrometry (RPLC/ESI-CID-HRMS/MS). Data-independent LC/MS mode was used for data acquisition.

RESULTS

The derivatization of the GA peptide mixture increased the detectability of RPLC/ESI-CID-HRMS/MS analysis. The efficacy of the procedure was demonstrated by using selected peptides related to different polymeric chain origins. The resultant peptides were derivatized in a predictable manner giving a minimum of side products. The reproducibility of the developed method was demonstrated by comparing peptide elution profiles derived from six Copaxone® lots.

CONCLUSIONS

Application of the AQC pre-column derivatization provides a framework that could be used as an attractive approach for monitoring the quality and characterization of NBCD products in the pharmaceutical industry.