An Over 50-Fold Yield Increase in 8 Months: How WuXi AppTec Helped a Client Overcome a Development Bottleneck

Antibody-drug conjugates (ADCs) have emerged as one of the most promising therapeutic modalities in oncology. Yet as molecular designs grow increasingly complex, the synthesis and process development of ADCs are becoming increasingly challenging. WuXi AppTec has established an integrated ADC platform to help clients accelerate ADC development. In one recent case, the team improved the overall yield of a client's innovative ADC molecule over 50-fold in just 8 months, a result that opened the door to deeper, long-term collaboration.

Several years ago, a biopharmaceutical company encountered just such a development bottleneck while advancing an innovative ADC project.

To keep the project on track for later-stage development, the client needed to optimize the synthetic route and complete delivery within 12 months. The initial route, however, involved numerous steps and relied heavily on complex purification processes, resulting in an extremely low overall yield.

This long and technically demanding synthesis posed a comprehensive challenge to both synthetic chemistry and early-stage process optimization. Against this backdrop, the client turned to WuXi AppTec.

To address these challenges, WuXi AppTec’s Research Chemistry Services (RCS) team optimized the route with future scale-up in mind. By integrating capabilities across multiple technology platforms, the team addressed critical challenges including byproduct control and increased the overall yield over 50-fold within just 8 months, delivering with a speed and quality that exceeded the client’s expectations.

The project subsequently progressed smoothly within WuXi AppTec from synthesis into later-stage process development. The experience also further strengthened the relationship between the two organizations, laying the foundation for deeper collaboration across additional pipelines.

How an Initial Collaboration Turned to Long-Term Trust

This collaboration did not happen by chance. It grew out of trust built through years of working together.

During an earlier engagement, the RCS team took on a molecule from the same client that had been stalled for many years. Faced with this long-standing challenge, the team drew on its extensive experience in drug discovery chemistry to redesign the synthesis and develop a more streamlined route.

Within 9 months, the team broke through the development bottleneck and successfully revived the long-dormant project. That experience marked the beginning of a strategic partnership and laid the groundwork for deeper collaboration in the years that followed.

It was this trust, established through successful project execution, that led the client to turn to WuXi AppTec again when it later encountered the development challenge described above.

As ADC innovation accelerated, the client was developing a new type of ADC. Based on preliminary work, the client had selected one promising synthetic route from several candidate pathways.

The technical challenges, however, remained substantial. The route involved more than 50 synthetic steps, with low reaction efficiency, far from sufficient to support subsequent process scale-up. Several technically demanding steps, including multi-fragment couplings and byproduct control, resulted in high levels of byproducts in key intermediates and made separation particularly challenging.

Breaking Through: Multi-Platform Synergy and a DPC Mindset

Faced with these challenges, the WuXi AppTec team took an early-stage process view and began systematically optimizing the route. Two core capabilities proved pivotal in breaking the deadlock.

The first was the coordinated support of multiple technology platforms.

At the time, the field was still in its early stage of development, with few established precedents to follow. Over the preceding years, however, WuXi AppTec had progressively built and refined its ADC capabilities.

For critical synthetic steps, the team also leveraged capabilities such as catalyst screening and recrystallization to optimize reaction conditions and route design, systematically improving both yield and product purity.

Drawing on deep expertise in this field, WuXi AppTec’s RCS provides integrated capabilities spanning linker and payload synthesis, analysis, and purification. Built on more than a decade of project experience, the platform has delivered more than 27,000 related compounds and established a modular system encompassing more than 1,000 linkers, over 30 antibody conjugation sites, and more than 30 novel payloads and their analogs. These capabilities support flexible synthesis from the milligram scale to the hundreds-of-grams scale.

The second capability was the consistent application of a Discovery Process Chemistry (DPC) mindset throughout the project.

In conventional drug development, discovery chemistry and process chemistry can sometimes become disconnected. A reaction that performs well at laboratory scale may experience a sharp decline in yield or become difficult to reproduce once scaled up.

The DPC approach is designed to bridge discovery chemistry and process chemistry by bringing scalability considerations forward into the discovery stage. From the outset, downstream process development informs how routes and reaction conditions are selected. The objective is therefore not simply to “make the product,” but also to consider whether the chemistry can be transferred, reproduced, and scaled effectively. This allows suitable reaction conditions for scale-up to be identified earlier.

Systematic Optimization to Overcome a Byproduct Challenge

The value of this holistic process perspective and integrated platform capability became especially clear when the team encountered a critical byproduct issue.

At one point in the synthetic route, a key intermediate was highly prone to an unexpected elimination reaction, generating substantial levels of an unwanted byproduct. In the initial route, substantial byproduct formation occurred, resulting in material loss and complicating downstream separation, purification, and biological testing.

To address the problem, the team systematically optimized several aspects of the process by leveraging capabilities across multiple platforms:

• Route design: By adjusting the molecular structure and reaction strategy, the team suppressed the side reaction at its source and substantially increased the proportion of the desired product.
• žProcess conditions: The team systematically screened coupling conditions to identify a reaction window that minimized byproduct formation while improving yield.
• Purification strategy: Conventional purification approaches were costly and difficult to scale. Guided by the DPC mindset, the team drew on technology platforms including catalyst screening, recrystallization, and flow chemistry to simplify operations, improve purification efficiency, and reduce the complexity of scale-up.

Following this multidimensional optimization, side reactions were significantly suppressed and product purity was substantially improved. The single-step yield increased, clearing the way for subsequent scale-up.

An Over 50-Fold Increase in Overall Yield in 8 Months

The successful optimization of this critical step reflected the broader systematic redesign of the entire synthetic route. Once the major bottlenecks had been addressed, early-stage process scale-up became far more straightforward.

During the first phase of the project, the RCS team increased the overall yield over 5-fold within 5 months, with delivery quantities satisfying the needs of biological screening.

The second phase focused on scaling the process from milligram to gram quantities. Building on the optimization already completed, the team further accelerated execution, shortening an anticipated 6-month timeline to just 3 months while achieving another over 10-fold increase in overall yield.

Across the two phases, the RCS team met the client’s objective in only 8 months. Overall yield increased over 50-fold compared with the initial route, while material utilization improved substantially. In the final key step alone, the single-step yield increased over 5-fold, significantly reducing material loss.

The project then advanced smoothly into subsequent process scale-up.

The high-quality delivery earned strong recognition from the client. Since then, the client has entrusted WuXi AppTec with more innovative ADC collaboration projects.

From a complex molecule requiring more than 50 synthetic steps to an increasingly deep and long-term client partnership, the significance of this story extends beyond the successful delivery of a single project.

As innovative therapies become increasingly complex, what is scarce is not only scientific inspiration, but also the ability to translate that inspiration into viable therapies. This is where WuXi AppTec creates value as an enabler of biopharmaceutical innovation.

At the increasingly complex frontier of novel molecule development, WuXi AppTec continues to strengthen its integrated platform capabilities in step with scientific advances and evolving client needs. Through its integrated enabling platform, WuXi AppTec helps innovators worldwide overcome development bottlenecks, accelerate novel therapies toward key milestones, and ultimately bring them to patients sooner.

Key Takeaways

• WuXi AppTec’s Research Chemistry Services (RCS) team increased the overall yield of a client’s innovative ADC molecule over 50-fold in 8 months.
• Leveraging the capabilities of WuXi AppTec’s ADC platform, the team systematically optimized the synthetic route, significantly suppressed side reactions and improved product purity for a critical step.
• WuXi AppTec’s Discovery Process Chemistry (DPC) approach bridges discovery chemistry and process chemistry by incorporating scalability considerations early in development, helping ensure that route and condition selections are transferable, reproducible, and better suited to subsequent scale-up.
• At WuXi AppTec’s RCS, the ADC platform has delivered more than 27,000 related compounds and established a modular system encompassing 1,000+ linkers, 30+ antibody conjugation sites, and 30+ novel payloads and their analogs, supporting flexible synthesis from the milligram scale to the hundreds-of-grams scale.