AOC (Antibody-Oligonucleotide Conjugate) DMPK Services

Antibody-oligonucleotide conjugates (AOCs) are subject to extensive distribution and degradation by nucleases in vivo, and the stability of their oligonucleotide payloads is critical for effective delivery and pharmacological activity in both the circulatory system and target tissues. Furthermore, the stability of the linker in systemic circulation, along with the plasma protein binding characteristics of the released free oligonucleotides, has a profound impact on their pharmacokinetic/pharmacodynamic (PK/PD) profiles. Leveraging a well-established in vitro ADME research platform for oligonucleotide therapeutics, WuXi AppTec DMPK has developed comprehensive AOC in vitro stability evaluation systems covering various matrices, including plasma and serum. These systems provide robust support for early discovery and in vitro ADME studies of AOC therapeutics.

WuXi AppTec DMPK has developed a comprehensive multi-dimensional biotransformation characterization platform for AOCs based on advanced LC-HRMS:

• Oligo-level profiling: Mapping metabolic changes across total oligo, released oligo, and conjugated oligo.

• Protein-level characterization: Intact or sub-unit profiling of the AOC.

This strategy provides critical insights for AOC development: (1) Guiding Linker Optimization: Elucidating release mechanisms and mapping specific cleavage sites in plasma, target cells, and tissues. (2) Guiding Oligo Design: Assessing payload stability and identifying major biotransformation pathways. (3) Supporting Bioanalytical & PK/PD Strategies: Identifying the most relevant analytes for quantitative PK/TK assays, and offering the mechanistic basis to correlate systemic exposure with efficacy and safety.

WuXi AppTec DMPK has built a comprehensive analytical platform for AOCs. Studies show that administration of AOCs can generate at least seven related analyte species in in vivo samples. A detailed understanding of the distribution and time-course of these species helps evaluate whether AOC delivery is efficient to reach the intended target, the effective concentration of the oligonucleotide, whether gene silencing meets expectations, and the relationships among these events.

Choosing the right analytical platforms is critical to obtain these key data. We have integrated liquid chromatography–mass spectrometry (LC–MS), ELISA/MSD, and RT-qPCR to create a broad detection capability for AOC biological components, including:

• Antibody-related species: total antibody, conjugated (bound) antibody, and intact antibody–sense strand (or intact antibody–ASO);

• Oligonucleotide-related species: total antisense strand (or total ASO), and the antisense strand in free versus conjugated forms;

• Oligonucleotide-to-antibody ratio (OAR).

Integrating technologies in radioisotope labeling, oligonucleotide synthesis, and antibody chemical modification, the platform enables ¹⁴C or ³H labeling of oligonucleotides and AOCs, delivering high-quality test articles for in vivo ADME studies. Leveraging an automated solid-phase synthesis system and proprietary labeling processes, combined with analytical and detection methods including SEC-HPLC, SDS-PAGE, and high-resolution mass spectrometry, the platform ensures high radiochemical purity of the final product while preserving the biological activity of the AOC. Supported by well-established experimental systems and extensive resources in rodent and non-human primate models, the platform enables systematic studies on tissue distribution (QWBA), mass balance, and metabolite identification.