Conquering Oligonucleotide-Lipid Conjugate Process Challenges: How WuXi AppTec Accelerates Client Timelines

Oligonucleotides represent a rapidly emerging modality. As the technology evolves, extrahepatic delivery is becoming a new trend, with the potential to expand oligonucleotide-based therapies into a broader range of disease areas. Lipid conjugation, as one of the key approaches for achieving extrahepatic delivery, still presents considerable challenges during the transition from laboratory to clinical development.

A biotechnology company collaborated with WuXi AppTec to advance an oligonucleotide-lipid conjugate drug candidate. At that time, the candidate (siRNA-lipid conjugate) was preparing to advance from the preclinical candidate compound (PCC) stage toward investigational new drug (IND) application.

The intrinsic complexity of this class of therapeutics had already made the program highly challenging. A specific client requirement further increased the level of difficulty: completing kilogram-scale manufacturing of a siRNA-conjugated lipid and achieving IND submission within an accelerated timeline of fewer than 9 months.

This timeline was significantly faster than the industry norm. Under typical circumstances, an oligonucleotide-lipid conjugate program generally requires approximately 11 months to progress from PCC to IND-enabling CMC readiness. In this case, the core development timeline had to be substantially compressed.

Faced with this highly demanding objective, the integrated WuXi TIDES team adopted a flexible development strategy combined with rapid execution, ultimately delivering the program at high quality. Within 8 months, the team completed the full set of CMC activities required to advance the program from preclinical candidate to IND submission, and the project successfully passed client acceptance.

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Chemistry Expertise Solves Critical Process Challenges for Clients

The story begins with oligonucleotide drug delivery.

Over the past decade, the clinical success of oligonucleotide drugs has been largely limited to liver-related indications. Liver-directed delivery technologies, such as GalNAc conjugation, have enabled efficient targeting of hepatocytes, driving the rapid development of siRNA and antisense oligonucleotide (ASO) therapies. 

However, when therapeutic targets shift to extrahepatic tissues — such as muscle, heart, and the central nervous system (CNS) — additional challenges arise. The blood-brain barrier in the CNS, tissue-specific barriers, and differences in target cell receptor distribution have made extrahepatic delivery one of the major challenges in the field of nucleic acid therapeutics.

In this context, oligonucleotide-lipid conjugates have been explored as a potential solution. By conjugating oligonucleotides with lipid molecules of different chemical structures, it may be possible to modulate protein binding properties in the blood and thereby direct drug distribution to extrahepatic tissues. These conjugates are therefore considered as a promising tool for achieving extrahepatic delivery.

Nevertheless, the development of such conjugates is technically challenging. Due to the poor water solubility of lipids, these molecules present hurdles in chemical design, synthesis and purification, analytical characterization, and formulation development. Furthermore, developing oligonucleotide-lipid conjugates requires expertise across small molecules, oligonucleotides, and conjugation chemistry, placing high demands on both technical depth and end-to-end integration capabilities. In addition, oligonucleotide drugs face tighter regulatory scrutiny for impurity control and genotoxicity assessment, imposing higher demands on quality control.

In response to these challenges, WuXi AppTec's integrated CRDMO platform supports clients in accelerating the development of such novel conjugates.

Over the years, WuXi AppTec has continuously built extensive chemistry expertise, laying a solid foundation for tackling the complexities of conjugation chemistry. Early in the rise of oligonucleotides, WuXi AppTec began building the WuXi TIDES platform, which focuses on oligonucleotides, peptides, and related chemical conjugation drugs, with established capabilities to provide end-to-end solutions for complex oligonucleotide conjugates.

For oligonucleotide-lipid conjugates, the team made early strategic investments as the technology emerged. Through ongoing project work, the team has established a comprehensive technical framework and accumulated extensive experience in addressing complex development and manufacturing challenges.

In 2025 alone, the platform delivered over 7,000 oligonucleotide-lipid conjugates. This figure reflects the team's experience with various conjugation sites on the 3′ and 5′ ends of strands, base or sugar skeleton of nucleotide, and phosphorus backbone. For lipid conjugates of various modalities, including siRNA, dual-targeting siRNA, and ASO, the platform has developed more than 20 lipid moieties suitable for conjugation.

At the process development level, the platform has accumulated extensive hands-on experience with various conjugation technologies, including amide coupling, amide condensation, click chemistry, and oxidative phosphoramidation. The close proximity of drug substance and drug product sites, together with a unified quality system, provides a strong foundation for high-quality, rapid project delivery.

The story returns to the client program described earlier. It was precisely this accumulation of technical expertise, platform capability, and hands-on experience that enabled the WuXi TIDES team to respond rapidly to the client’s needs.

Faced with an aggressive timeline and complex technical requirements, the team decided not to continue with the original solid-phase oligonucleotide synthesis strategy — a route that had become increasingly constrained. Under the initial process design, the customized lipid-functionalized support typically required a procurement lead time of two to three months, creating a supply bottleneck before synthesis could even begin. At the same time, the poor solubility and steric hindrance of the lipid significantly reduced coupling efficiency, resulting in low crude purity and unsatisfactory yield. Lipid-associated materials (such as free lipids, lipid degradation products, aggregates of siRNA-lipid complexes, etc.) also complicated downstream purification and endotoxin control, potentially introducing regulatory risk at the IND stage.

Timeline pressure, synthetic efficiency, and manufacturing quality all converged within a single program.

To overcome these challenges, the team redesigned the entire process route. Instead of following the original strategy, they adopted a new approach: completing oligonucleotide synthesis first, followed by solution-phase lipid conjugation. This change immediately improved operational flexibility. Lipid building blocks were synthesized in-house in parallel with oligonucleotide production, shortening the overall development timeline by approximately 2 months. By eliminating dependence on external lipid supply, the team also gained greater control over quality and supply reliability.

The new conjugation process achieved up to 95% homogeneous conversion, increased the crude purity by approximately 20%. Downstream processing was streamlined as well, with two purification steps consolidated into one. The team also developed and implemented a dedicated endotoxin control strategy across raw materials, equipment, and purification workflow, ultimately maintaining endotoxin levels in the final API below 0.05 EU/mg — well within regulatory expectations.

The Integrated CRDMO Platform Supports Acceleration of Project Development

If technical expertise and execution determined how well the project could be delivered, the integrated platform determined how quickly it could move forward.

Following the process redesign, the WuXi TIDES team advanced the program under an integrated development model. Lipid synthesis, process development, analytical method validation, and formulation development were all executed in parallel on a unified platform, enabling seamless coordination across functions.

Specifically, once the API team delivered the demo batch, process optimization began immediately, with pre-formulation/formulation development and API GLP production running in parallel. Drug product engineering batches followed, and API GMP batches were quickly advanced alongside to prepare clinical supply. Analytical method development and validation continued throughout the entire cycle.

This synergy is more than “working in parallel.” It rests on a deep, shared understanding of technical dependencies across upstream and downstream activities: each team knows what the prior stage will deliver and what the next stage needs, which cuts wait time and reduces communication inefficiencies. Built on an integrated platform with consistent processes, analytical methods, and quality systems, this approach increases success rates, minimizes deviations and repetitive re-validation during method transfers, and strengthens data integrity—supporting CMC consistency and regulatory acceptance. One dedicated project manager coordinates program end-to-end, further improving execution efficiency and risk control.

In short, cross-stage, cross-team, and cross-site frictions and risks are substantially reduced, enabling faster, more reliable project progression. This seamless integration of technical capability and collaborative mechanisms is the platform’s core value and differentiator versus traditional fragmented models.

Oligonucleotide-lipid conjugates offer a promising route from liver-targeted to extrahepatic delivery, though development remains technically challenging. In this case, reducing the R&D timeline from 11 to 8 months reflects not only improved efficiency but also the value of integrated capabilities in addressing complex development hurdles. This is consistent with WuXi AppTec’s vision: every drug can be made, and every disease can be treated.