Supporting the next era of scalable RNAi production: Insights from TIDES Europe 2025

The number of RNA interference (RNAi) therapies under development globally has steadily grown over the past five years, with more than 350 as of July 2025 [1]. Along with the hope each therapy brings to patients, every new asset increases the pressure on existing manufacturing capacity. Rising demand and a move toward larger indications are prompting developers to identify approaches that deliver efficiency, reliability and scale while supporting more sustainable operations.  

At TIDES Europe 2025, Derek Gauntlett, Vice President, Development and Pierre Barratt, Vice President, Strategy & Program Management, at Codexis, showcased how the ECO Synthesis® Manufacturing Platform is being developed to meet the needs of RNAi production.  

Optimizing RNAi manufacturing for scalability 

ECO (Enzyme-Catalyzed Oligonucleotide) Synthesis supports RNAi manufacturing through a solution-phase, sequential workflow that incorporates modified nucleotides step-by-step in a controlled environment [Figure 1], providing a scalable alternative to solid-phase oligonucleotide synthesis (SPOS). 

Figure 1. ECO Synthesis uses a sequential extend and deblock cycle in a fully aqueous, solution-phase workflow.  

Using an engineered polymerase and phosphatase cycle in a water-based environment, ECO Synthesis is designed to enable true manufacturing scale for RNAi therapeutics. By eliminating solid supports and enabling continuous material circulation through each reaction step, the platform removes many of the physical and chemical constraints that limit SPOS as batch sizes increase. The ECO Synthesis platform directly supports large-scale production, delivering predictable performance as programs advance from early development to commercial-scale requirements. 

ECO Synthesis is also designed to support high, consistent product quality. Controlled nucleotide incorporation in solution enables uniform reaction conditions, improved mass transfer and consistent impurity profiles as synthesis volumes increase. The ability to directly sample material throughout the workflow further reinforces quality control by providing visibility into sequence fidelity and purity that is not possible with resin-bound intermediates. 

Operating in a water-based environment and avoiding solvent-intensive solid supports reduces solvent use, waste generation and operational complexity. As a result, ECO Synthesis aligns scalable manufacturing with quality and sustainability, offering an approach that addresses the growing capacity, consistency and environmental challenges facing RNAi production as the field moves toward larger indications and higher demand. 

The process utilizes an extend and deblock cycle that operates within a multidimensional parameter space where flow rate, concentration, temperature and other factors influence reaction performance, in addition to product quality. Each parameter contributes to overall reaction behavior and understanding how they interact is essential for defining a robust operating range. 

Codexis has advanced this understanding through structured optimization. Leveraging design of experiments (DoE) [2], our experts have established how individual parameters shape extension performance and how their interactions influence overall process behavior: 

• Flow rate, substrate concentration and temperature were examined to understand their combined influence on extension kinetics and to identify conditions that may increase the risk of overextension. 

• Reservoir volume was identified as directly impacting cycle time and volumetric productivity and can be optimized via controlling wash volume or mid-run concentrations of the process. 

• Scale comparison studies confirmed that impurity profiles remain consistent between milligram to multi-gram syntheses, reinforcing confidence in how the process performs as volumes increase. 

Figure 2. Representative zoomed overlay of 0.5 and 10 gram scale impurity profiles by RP-LC-UV A260nm. 

The findings provide a clearer understanding of how ECO Synthesis performs as it scales, giving drug developers greater confidence in how the process can support consistent, high-quality output through scale-up. This confidence is reinforced by the Codexis Innovation Lab, which is equipped to intake and advance ECO Synthesis programs at 100 g+ scale beginning in 2026 (Figure 3).  

Figure 3. ECO Synthesis Innovation Lab evolution. 

Watch the TIDES presentation to discover how ECO Synthesis can strengthen your approach to scaling RNAi manufacturing. 

Strengthening RNAi manufacturing with cycle-level insight 

As the demand for scalable RNAi production approaches increases, in-process analytics will play an increasingly important role in ensuring manufacturing is efficient, reliable and scalable while maintaining high quality. The ECO Synthesis fully aqueous, solution-phase workflow supports this shift by enabling direct sampling at every extension and deblock step [Figure 4]. This offers manufacturers visibility into how each sequence develops and provides information that solid-phase systems cannot offer, as intermediates remain resin-bound. 

Figure 4. ECO Synthesis RNAi manufacturing ensures intermediates remain in solution as material circulates through each reactor, allowing direct sampling after extension and deblock steps.  

The FDA’s Process Analytical Technology guidance states that a process is considered well understood when all critical sources of variability are identified and explained, variability is managed by the process and product quality attributes can be accurately and reliably predicted across the design space [3]. The analytical development team at Codexis applies these principles within the ECO Synthesis workflow by integrating in-process testing that provides developers with real-time insight into cycle performance: 

• Quality control is supported through direct sampling, which confirms the identity and purity of intermediates at defined points in the sequence. 

• Safety assurance is strengthened through stepwise visibility that verifies sequence fidelity throughout the cycle. 

• Error detection is improved through early recognition of cycle deviations, allowing teams to intervene before downstream performance is affected. 

• Process optimization benefits from quantitative yield data that informs decisions and helps refine operating conditions with greater accuracy. 

These in-process capabilities support the broader optimization work across the ECO Synthesis platform and help developers respond to rising demand with greater confidence. 

Watch the TIDES presentation to explore how cycle-level insight can help you strengthen quality, safety and consistency as your RNAi programs advance. 

Meeting future needs for increasingly scalable RNAi manufacturing 

As demand for RNAi therapies increases and more programs enter the development pipeline, Codexis is expanding the ECO Synthesis platform’s capabilities to support future needs. Current focuses for advancement include larger-batch production (>100 grams), progress in stereoselective asset synthesis, and the integration of automated process analytical technology (PAT) workflows. These efforts reflect a commitment to giving drug developers the control, clarity and technical depth needed as RNAi manufacturing moves toward larger-scale requirements.