Reactivity-driven cleanup of 2-Aminobenzamide derivatized oligosaccharides.

N-glycan profiling is commonly accomplished by the derivatization of the enzymatically released oligosaccharides with a fluorophore, thereby facilitating their analysis by hydrophilic-interaction liquid chromatography (HILIC). These fluorescent dyes are often present in large excess during derivatization reactions, and their removal is typically required to minimize chromatographic interference. Herein, we report a reactivity-driven 2-phase extraction protocol with the aldehyde reagent octanal, which demonstrated efficient 2-aminobenzamide cleanup as well as high derivatized N-glycan recovery. This cleanup method can be performed within minutes, and therefore provides an alternative sample preparation route for N-glycan profiling with improved time efficiency and operational simplicity.

A rapid on-line method for mass spectrometric confirmation of a cysteine-conjugated antibody-drug-conjugate structure using multidimensional chromatography.

Cysteine-conjugated antibody-drug conjugates (ADCs) are manufactured using controlled partial reduction and conjugation chemistry with drug payloads that typically occur in intervals of 0, 2, 4, 6, and 8. Control of heterogeneity is of particular importance to the quality of ADC product because drug loading and distribution can affect the safety and efficacy of the ADC. Liquid chromatography ultra-violet (LC-UV)-based methods can be used to acquire the drug distribution profiles of cysteine-conjugated ADCs when analyzed using hydrophobic interaction chromatography (HIC). However, alternative analysis techniques are often required for structural identification when conjugated drugs do not possess discrete ultra-violet absorbance properties for precise assessment of the drug-to-antibody ratio (DAR). In this study, multidimensional chromatography was used as an efficient method for combining non-compatible techniques, such as HIC, with analysis by mass spectrometry (LC/LC/QTOF-MS) for rapid on-line structural elucidation of species observed in HIC distribution profiles of cysteine-conjugated ADCs. The methodology was tested using an IgG1 mAb modified by cysteine conjugation with a non-toxic drug mimic. Structural elucidation of peaks observed in the HIC analysis (1(st) dimension) were successfully identified based on their unique sub-unit masses via mass spectrometry techniques once dissociation occurred under denaturing reversed phase conditions (2(nd) dimension). Upon identification, the DAR values were determined to be 2.83, 4.44, and 5.97 for 3 drug load levels (low-, medium-, and high-loaded ADC batches), respectively, based on relative abundance from the LC-UV data. This work demonstrates that multidimensional chromatography coupled with MS, provides an efficient approach for on-line biotherapeutic characterization to ensure ADC product quality.

Development and application of a robust N-glycan profiling method for heightened characterization of monoclonal antibodies and related glycoproteins.

A highly robust hydrophilic interaction liquid chromatography (HILIC) method that involves both fluorescence and mass spectrometric detection was developed for profiling and characterizing enzymatically released and 2-aminobenzamide (2-AB)-derivatized mAb N-glycans. Online HILIC/mass spectrometry (MS) with a quadrupole time-of-flight mass spectrometer provides accurate mass identifications of the separated, 2-AB-labeled N-glycans. The method features a high-resolution, low-shedding HILIC column with acetonitrile and water-based mobile phases containing trifluoroacetic acid (TFA) as a modifier. This column and solvent system ensures the combination of robust chromatographic performance and full compatibility and sensitivity with online MS in addition to the baseline separation of all typical mAb N-glycans. The use of TFA provided distinct advantages over conventional ammonium formate as a mobile phase additive, such as, optimal elution order for sialylated N-glycans, reproducible chromatographic profiles, and matching total ion current chromatograms, as well as minimal signal splitting, analyte adduction, and fragmentation during HILIC/MS, maximizing sensitivity for trace-level species. The robustness and selectivity of HILIC for N-glycan analyses allowed for method qualification. The method is suitable for bioprocess development activities, heightened characterization, and clinical drug substance release. Application of this HILIC/MS method to the detailed characterization of a marketed therapeutic mAb, Rituxan(®), is described.

The von Willebrand factor antagonist (GPG-290) prevents coronary thrombosis without prolongation of bleeding time.

The interaction between von Willebrand factor (VWF) and platelet glycoprotein Ibalpha (GPIbalpha) is a critical step that allows platelet adhesion, activation and subsequent thrombus formation to the injured vessel wall under high-shear conditions. In this study, we sought to investigate 1) whether GPG-290, a recombinant human GPIbalpha chimeric protein, would prevent thrombosis in a canine model of coronary thrombosis by blocking VWF-GPIbalpha interaction; and 2) whether desmopressin (DDAVP), a VWF release stimulant, could reduce the prolonged bleeding time caused by a 10x efficacious dose of GPG-290. The antithrombotic efficacy of GPG-290 was evaluated by the in-vivo ability to prevent cyclic flow reductions (CFRs) and ex-vivo inhibition of platelet adhesion/aggregation reflected by prolongation of Platelet Function Analyzer (PFA-100) collagen/ADP closure time. The anti-hemostatic effect was assessed by template bleeding time. GPG-290 at doses of 25, 50 and 100 microg/kg abolished CFRs in 67%, 100% and 100% of the treated dogs without bleeding time prolongation, respectively; GPG-290 dose-dependently prolonged the ex-vivo collagen/ADP-closure time, while it had no effects on plasma VWF antigen level (VWF:Ag) and VWF-collagen binding activity (VWF:CB); the prolonged template bleeding time caused by 500 microg/kg of GPG-290 was prevented by intravenous infusion of DDAVP (0.3 microg/kg). In conclusion, GPG-290 appears to be an effective agent for treating arterial thrombosis without bleeding time prolongation.

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.