Site-specific GlyCLICK® Antibody Conjugates Suitable for Radioimmuno- and Fluorescent Imaging

GENOVIS PRESENTS

AUTHORS

INTRODUCTION

SUMMARY

RESULTS

Antibody conjugation is a powerful tool for applications ranging from imaging and immunoassays to ADC development. The quality and robustness of the conjugation technology is critical to obtain reliable and reproducible results. Conjugation at the Fc-glycans using GlyCLICK has proven to be a promising technology for obtaining site-specific and homogenous antibody conjugates. GlyCLICK is based on a two-step enzymatic modification of the IgG Fc-glycans by deglycosylation and subse-quent addition of a GalNAz-group to the inner GlcNAc. The azide activated Fc-gly-cans are then conjugated with an alkyne-carrying label of choice using copper-free

Hanna Toftevall, Felicia Mejàre, Maria Nordgren, Helén Nyhlén, Jonathan Sjögren, Fredrik Olsson | Genovis AB, Lund, Sweden

• Aim: Characterize GlyCLICK-conjugates and demonstrate the potential of using GlyCLICK from antibody screening to evaluation.

• Deglycosylation using GlycINATOR enables quantitative site-specific conjugation

click-chemistry. In this work, we present GlyCLICK for site-specific conjugation with a variety of labels and analyze the material using RP-HPLC. We also demonstrate by surface plasmon resonance how GlyCLICK preserves immunoreactivity and show the superior tumor uptake of GlyCLICK-conjugated antibodies in vivo using PET/CT imaging. Finally, we highlight the potential of site-specific labeling in fluorescent im-aging applications using GlyCLICK-conjugated antibodies for flow cytometry and in vitro imaging.

• Site-specific GlyCLICK-conjugates display preserved antigen binding capabilities

• GlyCLICK is robust with a mode of incorporation that is independent of the label

• Homogenous and less hydrophobic GlyCLICK- conjugates show increased tumor uptake

• High-quality and dynamic fluorescent imaging using GlyCLICK

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Increased Tumor Uptake using GlyCLICK for Immuno Imaging

Hydrophobicity decreases stability and contributes to complex behavior that may impact antibody performance in vivo. Trastuzumab was site-specifically conjugat-ed with deferoxamine (T-GlyCLICK-DFO) and compared to random conjugates (T-DFO) to study the effect on hydrophobicity. HIC analysis (Fig. 4a) shows ho-mogenous and less hydrophobic material with DOL=2.0 using GlyCLICK as com-pared to the random conjugates. The performance in vivo was also evaluated by PET/CT imaging after 89Zr-labeling, showing superior tumor uptake with GlyCLICK conjugates (Fig. 4b).

Contact email: hanna.toftevall@genovis.com

Figure 2. MALDI-TOF analysis of GlycINATOR- and IgGZERO®-hydrolyzed cetuximab N-glycans. The glycans were separated after 30 min incubation with enzyme at 37°C and analyzed using MALDI-TOF. Glycans were detected as sodium adducts.

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The first step in the GlyCLICK workflow involves trimming of the N-linked Fc-gly-cans of IgG using GlycINATOR (EndoS2). To study the glycoform specificity of GlycINATOR, the hydrolyzed glycans from a therapeutic antibody were analyzed by mass spectrometry. The results show that GlycINATOR removes all kinds of glycoforms, including high-mannose and hybrid-type glycans (Fig. 2)*. Deglyco-sylation and exposure of the core GlcNAc by GlycINATOR enables complete con-jugation with a consistent degree of label (DOL=2.0) on IgG from several species and subclasses.

Deglycosylation using GlycINATOR®

High-quality Dynamic Fluorescent Imaging using GlyCLICK

Indirect detection is often limited by primary antibody species and secondary an-tibodies are a potential source of background staining or cross-reactivity. The per-formance of GlyCLICK-conjugated trastuzumab with AlexaFluor647 (T-GlyCLICK- AF647) or Cy5 (T-GlyCLICK-Cy5) and indirect detection was evaluated using flow cytometry. The results show a higher separation index using GlyCLICK for direct conjugation (Fig. 5a). Imaging of HER2(+) cells and tissue show that T-GlyCLICK-AF647 results in dynamic visualization of antigen distribution. The homogenous material enables quantitation (Fig. 5b). Random labeling requires optimization and results in heterogeneous material, here DOL=0-7 (avg. 3.3).

GlyCLICK Random

GlyCLICK Random

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SELECTION

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EVALUATION

Figure 1. Schematic presentation of GlyCLICK during selection and evaluation of antibody candidates. Site-specific and quantitative conjugation preserves affinity and minimizes variability. GlyCLICK is suitable for robust workflows from antibody selection to antibody candidate evaluation. The same reproducible technology is used to incorporate the label of choice needed in multiple bioanalytic applications in mAb and ADC development.

Figure 4. a) HIC separation of trastuzumab, GlyCLICK and random conjugates injected on TSKgel® Butyl-NPR column (Tosoh Bioscience) in 25 mM NaP pH 7, 1.5 M ammonium sulfate and eluted with a salt gradi-ent with 20% isopropanol. The more hydrophobic random lysine DFO-conjugates were not resolved due to heterogeneity. b) PET/CT imaging of SK-OV-3 tumor bearing mice using GlyCLICK and randomly labeled 89Zr-DFO-trastuzumab showing mean tumor uptake (Minerva Imaging).

Figure 5. a) FCM analysis of HER2(+) human Fc-blocked cells (MDA-MB-435) incubated with GlyCLICK con-jugates or mouse anti-human (3B5) primary antibody (3.7 μg/ml). Cells incubated with 3B5 were detected by donkey anti-mouse AlexaFluor647 labeled antibody (1:200). Images were obtained using CytoFlex. b) Confo-cal microscopy of HER2(+) cells (MDA-MB-453) and paraffin embedded HIER processed human breast tissue incubated with AlexaFluor647 GlyCLICK or random conjugates (cells 1μg/ml, tissue 10 μg/ml) and DAPI (0.2 μM).

Figure 3. a) RP-HPLC analysis of panitumumab unmodified and conjugated with DFO, AlexaFluor488, Bio-tin or MMAE digested with FabRICATOR. RP-HPLC was performed on Agilent 1290 using Waters Acquity UPLC® BEH C4, 1.7 μm, 2.1x100 mm column. b) Affinity analysis of trastuzumab conjugated with DFO, MMAE or AlexaFluor488 using GlyCLICK (DOL 2). Anti-human IgG (Fc) was used as capture molecule and HER2 injected in a range ensuring sufficient curvature. The data were fitted against a 1:1 mathematical model.

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Therapeutic antibodies were conjugated with a selection of labels for analysis us-ing RP-HPLC and surface plasmon resonance (SPR) to evaluate the specificity of GlyCLICK and the preserved affinity of the conjugated antibodies. The results show the reproducible mode of incorporation using GlyCLICK, as indicated by the distinct elution peaks for the conjugated Fc/2 (Fig. 3a). Site-specific GlyCLICK conjugation does not interfere with the Fd’ or LC chains, thereby preserving anti-gen binding capability (Fig. 3b).

Site-specific Conjugation Preserves Affinity

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Reference: *Sjögren, J. et al., 2015. EndoS and EndoS2 hydrolyze Fc-glycans on therapeutic antibodies with different glycoform selectivity and can be used for rapid quantification of high-mannose glycans. Glycobiology, 25(10), pp.1053–1063.