Integration of Imaged cIEF with Mass Spectrometry Accelerates the Identification of Charge Variants in Intact Monoclonal Antibodies

Scott Mack, Steve Lacy, Jennifer Ji, Erik Gentalen – Intabio, Inc., Newark, CA

Charge heterogeneity analysis is essential for the successful development and quality monitoring of therapeutic proteins. Imaged capillary isoelectric focusing (cIEF) is a proven approach for analyzing charge variant isoforms as many protein modifications and degradation events affect isoelectric point. Mass spectrometry (MS), with the capability of resolving subtle mass differences, has the capacity to identify protein modifications that cannot be resolved by cIEF. Coupling cIEF with MS detectionresults in a powerful analytical approach for more comprehensive protein characterization. This work demonstrates how a novelmicrochip-based assay integrating a MS-compatible imaged cIEF separation methodology with QTOF MS analysis vastly improves the workflow for the characterization of intact biologic isoforms, laying the groundwork for routine cIEF-MS monitoring of bioprocessing steps.

Using the NIST Monoclonal Antibody Reference Material 8671, we demonstrate real-time, label-free, intact protein variant analysis that combines imaged cIEF with MS detection. Infusion of NIST mAb demonstrates sensitive nanoflow conditions for stable electrospray and good ionization efficiency. The deconvoluted mass spectra identify 16 of 18 of the known glycoformswhen using a Bruker Compact QTOF.

Our key innovation is the integration of imaged cIEF and microchip-based ESI into a multi-layer microchip with an incorporated imaging aperture. Our design enables UV detection of the entire separation channel for real-time imaged cIEF and facilitates precise addition and mixing of the electrolyte solution needed to ionize the proteins for MS analysis. Intabio’s utilization of the microchip format obviates many of the key problems with capillary-based approaches, including how to mobilize the separated protein isoforms to the ESI emitter at the end of the chip. In a microchip format, an intersecting channel can introduce an electrolyte to ionize the isoforms, each of which is at net zero charge after focusing. Peaks can then be mobilized electrophoretically to the ESI emitter for ESI delivery to the MS orifice. ESI is an industry standard technique for sample introduction into MS, and is compatible with all major manufacturers’ MS instrumentation. In addition to the microchip design, reagents and coatings have also been developed to be compatible with both cIEF and MS. Intabio has patents issued and pending that cover the chip design and other novel assay aspects of the integrated assay.

Introduction

Microchip Design & Production

The current process required to characterize an unknown protein modification following identification is cumbersome and requires weeks of work. Blaze system, connected to a MS, integrates imaged cIEF seamlessly to MS analysis to provide real-time, label-free analysis of intact proteins.

Intabio’s Proprietary Microchip Platform Provides Seamless Integration of Imaged cIEF and MS for Intact Protein Analysis

Imaged cIEF on a Blaze Microchip

Results

Figure 3. A) Linear separation of isoelectric point (pI) standards marker ladder demonstrates pH 3 -10 separation. Standards imaged in real-time during 8 min. separation (600 V/cm). Detection analysis: 280 nm absorbance. Peptide markers (12.5 mg/mL) in a mixture with 4% Pharmalyte 3-10 carrier ampholytes. B) Separation of NISTmAbcomparable to conventional cIEF systems using the Blaze system. The NISTmAb sample (250 ug/mL) is in 1.5% Pharmalyte 3-10 carrier ampholytes, 1.5% Pharmalyte 8-10.5 carrier ampholytes and 20 mM Arginine.10 min separation (600 V/cm). Detection by 280 nm absorbance.

Figure 4 A) Stable Taylor cone formation and electrospray using the Blaze microchip. B) ESI tip. C) Total ion count and MS chromatogram showing mass spectra for NISTmAb. NISTmAbtuning solution (500 µg/ml) was loaded onto the chip and flowed at a rate of ~100 nanoliters/min. A voltage of 3000 V was applied for ESI. Data demonstrates that fluidic control and cIEF reagents are compatible with ESI. Deconvoluted data shows that we are detecting 16/18 glycoforms using a Bruker Compact Q-TOF.

Blaze Microchip Achieves Nanoflow for Efficient Electrospray Ionization

ESI Emitter Tip

Electrospray

Summary

Features, Workflow, Benefits

Successful demonstration of each of the three key analytical functions required for real-time, label-free, intact biopharmaceutical analysis that seamlessly integrates imaged cIEF with in-line mass spectrometer analysis utilizing Intabio’s proprietary microchip technology:

• Capillary isoelectric focusing of the NISTmAb• Real-time, whole column imaging by 280 nm UV absorbance• Ionized electrospray of NISTmAb

On-going development to demonstrate full integration of imaged cIEF-MS/NISTmAb

To request additional information or inquire about our Early Access Program,please visit us at WWW.INTABIO.COM or email Info@intabio.com.

Conventional cIEF System, Technical Seminar,

CE Pharm 2016

Mass Spectra16/18 Glycoforms Detected

Key development elements of Intabio’s integrated imaged cIEF-MS assay include:• Chip production• Development of an imaged

cIEF assay with our novel microchip design and MS compatible reagents

• Establishing conditions for electrospray from the microchip to the mass spec

Demonstration of good chip-to-chip cIEF separation reproducibility using NISTmAb. NISTmAb profile resolution is maintained and all terminal lysine variants are detected across multiple chips. Sample composition is 1.5% Pharmalyte 5-8, 1.5% Pharmalyte 8-10.5, 20 mM Arginine and 250 µg/mL NISTmAb in DI H2O.

A B C

Total Ion Count

A

B

Molded bottomHigh throughput

A. Two Layer Chip for CommerciallyScalable Process

Two layer chipChannel features molded into bottom Layer; Laminate layers

• Robust, automated process• Commercially scalable• Single point source

B. Reproducible cIEF SeparationAcross Multiple Chips

A1

Rapid Set Up and Automated Operation Enables 100x Faster Intact Biologics Quality Characterization

Benefits•100 times more fully characterized samples

•Time & labor savings by eliminatingscale-up, chromatographic method development and peak collection

•Load sample plate/vial, reagents, 1 cartridge into instrument

•Onboard mixing of Sample + Ampholyte + pI Standards

•Add to 96-well plate

•Set assay parameters

•Tune MS and set initial alignment between ESI tip and MS (10-30 min)

Blaze 1.0Connected to MS for cIEF-MS

Blaze 1.0

1 Lys

2 Lys

Acidic

0 Lys (Main)

Sample Introduction

Mass Spec+

+

Electrolyte

Separation and Imaging column, 50 mm length

Separation Channel

ElectrosprayTip

Microfluidic Chip

Core technology patent issued Feb 2019

Imaged cIEF Peak mobilization Electrospray to MS