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With the precision of monoclonal antibodies and the potency of small-molecular payloads, antibody-drug conjugates (ADC) are promising cancer therapeutics. As of this year, there are 19 ADC drugs available on the market, with more than 200 in clinical trials. However, getting more of these treatments on the market requires addressing unique manufacturing challenges. These include strict containment due the hazardous payload; use of organic solvents, which may extract unwanted components from the single-use plastics; and reliable analytical control of the drug-antibody ratio (DAR), which is an important critical quality attribute.
Repligen’s portfolio of single-use and analytical technologies offer capabilities that are uniquely tailored to enhance safety for both the product and operators, and to boost the performance of the ADC manufacturing workflow.
Self-contained flat sheet cassettes for closed processing and operator safety
Tangential flow filtration (TFF) is a key process step in ADC purification. It removes unreacted small-molecular payload and organic solvent, adjusts product concentration to meet the drug substance specification, and replaces starting buffer composition with formulation buffer. The traditional cassettes must be installed into stainless steel holders, and most TFF steps are not performed in functionally closed systems. However, the high potency and toxicity of the payload requires isolating operators and/or using closed processing to address safety concerns.
Repligen’s TangenX® SC self-contained, flat sheet TFF device mitigate these risks by adopting a closed, holder-free design. Each device is gamma-irradiated, fitted with AseptiQuik® connectors, and the compression is captured by the housing, which eliminates torquing and minimizes the risk of product bypass. TangenX SC TFF devices are available in a range of molecular weight cutoffs (10–300 kDa) and surface areas (0.5–10 m2), and they are linearly scalable from traditional cassettes, as they have the same membrane chemistries (ProStream® and HyStream®) and flow-channel dimensions.
Benchmarking studies were conducted by Sanofi with technical support from Repligen to compare Repligen’s 30 kDa ProStream and HyStream cassettes against their current platform. The ProStream reusable cassette was tested head-to-head with the reference cassette (comparable protein load, flow rate, transmembrane pressure) used in commercial ADC production. The results showed comparable processing time, quality attributes, slightly lower recovery (93% vs. 99%), and higher normalized water permeability (90% vs. 60-70%) with ProStream. The HyStream single-use cassettes were tested with higher protein load and higher final concentration than used for the reference cassette. The process control strategy was also changed to pressure-drop regulation. The HyStream cassettes achieved a 30% reduction in processing times despite the 50% higher protein load and provided comparable quality attributes and recovery.
Ensuring product consistency and safety with single-use solutions
Most ADC payloads are hydrophobic, which implies that conjugation often uses organic solvents. These solvents can interact with and extract compounds from single-use components, whose presence may influence the efficacy and/or safety of the product.
To evaluate material compatibility with the most common solvents in ADC manufacturing, Repligen performed an extractables study on the ProConnex® Flow Path assemblies for KrosFlo® RS TFF systems and TangenX® SIUS Gamma TFF devices using the BioPhorum (BPOG) standardized testing protocols. Test materials were exposed to 20% dimethyl sulfoxide, 20% dimethylacetamide, and deionized water under controlled conditions. Appropriate analytical methods were utilized to detect volatile, semi-volatile, and non-volatile organic extractables, and inorganic extractables in the collected samples.
Results confirmed low extractable profiles in all samples. Just seven organic extractables were detected in the ProConnex® Flow Path samples, with a single one exceeding 0.05 µg/cm². For the TangenX® SIUS gamma device, 19 organic compounds were identified, but only three surpassed the 0.05 µg/cm² threshold. In all cases, the dominant species were inorganic extractables (sodium, potassium, and silicon).
These findings demonstrated that Repligen’s single-use ProConnex® assemblies and TangenX® SIUS Gamma devices represent low risk from an extractables and leachables points of view. They also support their use in the ADC manufacturing workflow.
Improving process efficiency with real-time analytics
Accurate, rapid measurement of the DAR ensures an effective therapeutic with minimal off-target effects. Repligen’s CTech™, SoloVPE®, and FlowVPX® variable pathlength spectroscopy (also called Slope Spectroscopy®) systems bring real-time visibility for both at-line and in-line monitoring of ADCs. Digging deeper into the technology, SoloVPE applies Slope Spectroscopy to generate linear absorbance data. The method makes it possible to measure different concentrations without requiring background correction and dilution, which minimize the risk of error.
In a recent case study, Repligen ran experiments with Piramal that compared Slope Spectroscopy to traditional UV-Vis. In one experiment assessing its linearity, the system achieved recovery rates between 96% and 100% across different concentrations, while meeting all acceptance criteria for multiple experiments. Compared to traditional UV-Vis workflows that can take minutes or hours, SoloVPE shortens analysis times to mere seconds, reduces costs by roughly one-third, and has fewer preparation steps.
FlowVPX extends these capabilities in-line by supporting continuous monitoring of protein concentration, drug clearance, and DAR during TFF. Furthermore, employing the FlowVPX optimizes the formulation buffer required to clear free drug, thereby shortening diafiltration processing time and increasing available manufacturing capacity.
Access to real-time readouts from the system helps manufacturers make decisions quickly and avoid overprocessing.
These studies demonstrate how Repligen’s application of automation, material science, and advanced analytics can simplify one of the more demanding workflows in biopharma. Taken together, the technologies described above provide firm footing on which to build the next generation of ADC manufacturing workflows that yield effective therapies for patients.
