Assessing Antibody Aggregation

Microfluidic channels
Experimental set-up containing microfluidic channels that are used to discriminate the individual effects of interfaces and hydrodynamic flow on the aggregation of antibodies. [Paolo Arosio, PhD, ETH Zurich]

The impact of an antibody varies between individual and aggregated forms. The biological activity can change. Aggregated antibodies can also cause a patient’s immune system to attack the therapeutic molecule. Paolo Arosio, PhD, professor of biochemical engineering at ETH Zurich, and his colleagues study the causes of aggregation in antibodies in bioprocessing and delivery.

“During several manufacturing steps antibody solutions are exposed to interfaces and hydrodynamic flow stresses, which often lead to protein aggregation,” Arosio says. “In our work, we have designed an experimental set-up containing microfluidic channels to discriminate the individual effects of interfaces and hydrodynamic flow, including shear stresses.” This method allows researchers to control the interfaces—areas of contact between antibodies and surfaces of bioprocessing equipment—and the flow of a process. Our results demonstrate that these two factors can act synergistically in promoting formation of protein aggregates and should be often considered together when discussing sources of protein aggregation.”

This work revealed a couple problems at interfaces. As Arosio explains: “Our experiments add to the large body of evidence that interfaces are often evil for biopharmaceuticals and can promote formation of protein particles or films.” He adds, “Major attention should be therefore given to protein stability against interfaces, even during the early stages of drug development.” But it’s not just the interfaces that matter. “Hydrodynamic flow, mechanical agitation, or mechanical scraping can also have a synergistic and important effect—in our case by favoring displacement of aggregates into the bulk.”

Arosio plans to dig deeper into how these interactions arise. His team “would like to know the molecular details of the formation of protein particles at interfaces, which involves multiple microscopic steps such as protein adsorption, possible protein denaturation, heterogeneous nucleation and possible growth of particles, desorption, and release into the bulk phase,” he said. “Moreover, we would like to know how the presence of flow can affect all of these steps.”

To develop a better understanding of the processes that impact antibody aggregation, Arosio believes that more than one approach is required. “We believe that microfluidic technology coupled with chemical kinetic modeling represents promising emerging platforms to better understand the effect of flow and interfaces on protein aggregation, with implications for industrial bioprocessing,” he explains. “This understanding is crucial for the development of strategies—such as optimization of buffer composition—to improve the stability of biopharmaceuticals, with consequences on their safety and efficacy.”

Just designing the right monoclonal antibody fails to ensure the desired efficacy. Molecules must behave as expected during bioprocessing and delivery, or these processes could turn a potent therapy into a problem. That’s just what Arosio’s team hopes to prevent—improving the processes along the way.

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