Abstract
Purpose :
Antibody-drug conjugates (ADCs) are a class of therapeutics that combine the target specificity of an antibody with a linked toxin. Conventional antibody drug conjugation methods have limited drug-to-antibody ratio (DAR), a critical attribute for ADC efficacy. In our antibody biopolymer conjugate (ABC) platform, an antibody is conjugated to a large branched hydrophilic phosphorylcholine biopolymer. The ability to generate random co-polymers allows high loading of small molecules to this attached biopolymer and may overcome DAR limitations without perturbing antibody function. Here, we evaluated if ABCs can be internalized upon binding to cell-surface receptors using a fluorescence-based internalization assay, providing a proof of concept for using ABCs for target-specific intracellular deliveries.
Methods :
A known internalizing anti-VEGFR2 antibody was conjugated to an 800 kDa biopolymer. The antibody and its conjugate were labeled with pHAb amine reactive dye, and their potency was evaluated by ELISA and VEGF cell reporter assays. For the antibody internalization assay, VEGFR2 expressing cells were treated with pHAb labeled molecules. The internalization signal was monitored at Ex/Em: 532nm/560nm by Tecan plate reader after 20 hours and images were taken under RFP channel with a Nikon microscope.
Results :
Dye labeling has minor impact on the potency of anti-VEGFR2 and its conjugate. The latter shows partially compromised binding to VEGFR2 on cell surface likely due to the steric hindrance of the attached polymer. Fluorescence measurements showed emission intensity of pHAb labeled molecules is pH dependent. In the internalization assay, a specific and concentration dependent fluorescence signal was detected for the cells treated with either anti-VEGFR2 or its conjugate. No significant difference was observed in the distribution or intensity of the internalized fluorescence between the anti-VEGFR2 antibody and its conjugate.
Conclusions :
The internalization of anti-VEGFR2 antibody biopolymer conjugate demonstrates the potential for intracellular drug delivery using the ABC PlatformTM. This platform, combined with diverse drug modalities such as oligonucleotides, small molecules and peptides, overcomes current DAR limitations and provides a broad range of options for drug loading and intracellular delivery.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.