Viscosity Reduction with An Excipient Platform and Feasibility Testing Service

Higher viscosities for injectable drugs can present significant problems for both manufacturers and patients. The typical approach of using a single excipient to achieve appropriate viscosity in the drug formulation is insufficient, given that each therapeutic protein is unique and behaves differently at high concentrations and in different formulation conditions. Lowering the viscosity of the drug product can also reduce downstream processing times and thus lead to improved process economics. The SAFC® Viscosity Reduction Platform provides formulation viscosity and protein stability to achieve optimum results. Scientists interested in evaluating the platform can request a sample kit or leverage MilliporeSigma’s raw material expertise and analytical capabilities through its new Feasibility Testing Service. In this Q&A, Alana Gouveia, Protein Formulation Scientist for SAFC® Raw Materials at MilliporeSigma, explains the application of the platform and how it is evolving to meet customer needs, with Pharma’s Almanac’s David Alvaro, Ph.D.

David Alvaro (DA): What can you share about the challenges formulators are facing with regard to viscosity?

Alana Gouveia (AG): Higher viscosities for injectable drugs can be a significant problem for both drug manufacturers and patients themselves. For subcutaneous administration, there is a limit to the acceptable viscosity of formulations, which is approximately 20–25 millipascal seconds (mPa·s). During the biomanufacturing process, usually tangential flow filtration (TFF), therapeutic proteins undergo purification and concentration steps, which may result in an increase in viscosity, as well as decrease in membrane penetration, hence low yields. This is when high viscosities can present difficulties.

Viscosity can become a challenge at concentrations of about 100–200 mg/mL. At this concentration range, viscosity challenges occur by the formation of transient protein clusters, which can be driven by an affinity of the antibody for self-interaction. Under molecular crowding conditions, which are predominant at concentrations above 200 mg/mL but might occur also at concentrations below 200 mg/mL, antibodies are forced into close proximity to each other, which yields to interactions even when the antibody has a low self-affinity.

It is important to keep in mind that interactions between different proteins and the interactions that are responsible for one protein maintaining its native structure are identical. Therefore, any viscosity-reducing excipient can also destabilize an antibody. As a result, too much interference with interactions made in the name of lowering viscosity can lead to the destabilization of the protein molecules. Adding to this challenge is the fact that each protein has a unique structure and therefore behaves differently — and not very predictably — at high concentrations.


DA: What is the best overall approach to reducing viscosity in these formulations, and how is protein stability maintained?

AG: Formulation scientists today most often choose a single excipient — generally the amino acid arginine — to reduce the viscosity of protein formulations. However, in some cases viscosity-reducing excipients may also interfere with protein stability. Moreover, there is no general excipient on the market that can reduce viscosity and maintain stability of all therapeutic proteins. Therefore, there is a need for innovative solutions in this direction.

Extensive research at MilliporeSigma revealed that the combination of an amino acid and an anionic molecule can provide a good balance between decreasing protein viscosity and maintaining protein stability, which has been showcased by long-term stability studies. The SAFC® Viscosity Reduction Platform provides a toolbox of amino acid and anionic excipients from which formulation scientists can select the most efficient, empirically determined combination for a given protein or antibody under specific formulation conditions.

Importantly, all of the excipients included in the SAFC® Viscosity Reduction Platform have been used in human applications, most in parenteral formulations in the past, either as parenteral nutrition agents, as counterions to APIs, or for pH adjustment. The respective safety evaluations from a European Registered Toxicologist can be provided.

DA: How does the platform overcome challenges faced by formulators?

AG: The ability to vary the excipient combinations with the SAFC® Viscosity Reduction Platform gives formulation scientists a high degree of flexibility for balancing formulation viscosity and protein stability, as well as helping to meet target pH levels while taking the route of administration and the requirements of the recombinant protein, plasma protein, or antibody into account.

Plasma proteins are a notable example, because the typical treatment volumes are high, and thus approaches that allow an increase in the maximum dose per volume would be highly beneficial for patients. Indeed, the excipient combinations offered through the SAFC® Viscosity Reduction Platform not only enable higher concentrations while preserving long-term stability; they make the treatment as a whole more patient-friendly and more economical. Our unique excipient combinations can also be used to formulate biobetters with increased concentrations, offering patients the opportunity to receive their medications in a more convenient manner, potentially contributing to increased patient compliance.

DA: Does the SAFC® Viscosity Reduction Platform also impact the downstream process?

AG: For downstream operations, reducing viscosity enables higher concentrations to be achieved during tangential flow filtration (TFF). TFF is used for the ultrafiltration/diafiltration step preceding fill/finish operations, and very high protein concentrations are often involved, leading to the generation of back pressure in the system that can be challenging to manage. Reducing the viscosity can reduce these issues during this critical step. At MilliporeSigma, we have conducted studies which show that a significant increase in protein concentration can be achieved with a reduced processing time by using combinations from the SAFC® Viscosity Reduction Platform. Shorter processing times, in turn, contribute to improved downstream process economics. This approach supports small-volume formulations of protein drugs necessary for subcutaneous delivery by enabling high concentration.

DA: I understand that the Viscosity Reduction Platform has evolved since it was first introduced. Can you tell me about the recent addition and how it completes the offering?

AG: The addition of IPEC/PQG GMP pyridoxine hydrochloride (vitamin B6) to the SAFC® Viscosity Reduction Platform rounds out the full offering of the platform. In addition to vitamin B6, the other excipients include IPEC/PQG GMP-quality L-ornithine hydrochloride, L-phenylalanine, L-arginine, benzenesulfonic acid, and thiamine phosphoric acid ester chloride dihydrate (vitamin B1 derivate). These excipients are part of the Emprove® Expert portfolio of chemicals, designed for high-risk applications where the lowest microbiological and endotoxin levels are essential. The six platform excipients can be used in up to nine different combinations, giving formulation scientists a high degree of flexibility for balancing formulation viscosity and protein stability.

To be able to evaluate the feasibility of the viscosity-reducing agents to the specific protein or development project, a test kit that contains samples of the six viscosity-reducing excipients included in the platform, along with a detailed user guide describing proof-of-concept screening procedures, is available free-of-charge. Researchers who are interested in a specific combination of excipients for the formulation of a protein of interest can obtain a commercial technology license. The benefit for the customer is the opportunity to exclusively protect that specific solution.

All of the components in the platform are available at commercial scale under MilliporeSigma’s Emprove® Program, which combines high-quality products, comprehensive documentation, and superior customer support to facilitate qualification, risk assessment, and process optimization.

DA: Beyond providing the SAFC® Viscosity Reduction Platform itself, does MilliporeSigma also offer a dedicated service to help scientists that may not have the necessary expertise to get the best results from the platform?

AG: As an alternative to evaluating the platform in their own laboratories, scientists can access MilliporeSigma’s newly launched Feasibility Testing Service to support their efforts to formulate low-viscosity, high-concentration drug products. This service is ideally suited for those seeking a fast evaluation of viscosity-reducing excipient combinations and for scientists that do not have experience working with high-concentration biologics and/or lack the full analytical capabilities necessary to ensure comprehensive evaluation of performance. Using the feasibility testing service allows them to avoid significant investments in resources while still at the technical proof-of-concept stage.

The benefit to scientists of accessing the Feasibility Testing Service is rapid identification of the most effective excipient combination from the SAFC® Viscosity Reduction Platform for their specific drug candidates and formulations. The work is completed by dedicated application experts with extensive experience in high-concentration drug formulation and the analytical expertise and capabilities needed to thoroughly characterize formulation performance.

DA: Can you expand on the Feasibility Testing Service and how it is structured to support the unique needs of different customers?

AG: The new Feasibility Testing Service launched two study packages, including a basic package with optimally selected methods to make a quick and accurate decision on which excipient combination works best for a specific protein of interest. Such methods include a viscosity profiling at different protein concentrations by microfluidic viscometry; an excipient screening using our SAFC® Viscosity Reduction Platform excipients as well as other optional benchmarks excipients to identify the best excipient combinations, and a rounded-off analytical package to analyze the protein integrity in the new formulation, including buffer osmolalities; a nano differential scanning fluorimetry (nanoDSF) to check the conformational stability, size-exclusion ultra-high-performance liquid chromatography (SE-UHPLC) for protein integrity and purity analysis, and dynamic light scattering (DLS) to determine the hydrodynamic radius of the protein. A more extensive analytical package is also available that includes assessment of the viscosity profiles of the optimal formulations to determine the maximum protein concentrations that can be reached.

The stability extension package includes an extended stability study to assess the long-term stability of the optimal formulation. It is conducted in compliance with regulatory requirements, and thus customers can refer to the results when planning for regulatory approval. Samples are stored in a climate-controlled chamber, either at 2–8 °C or 25 °C for three months or at 40 °C for three weeks. Analyses once again include the nanoDSF for conformational stability and SE-UHPLC for protein integrity and purity, as well as capillary electrophoresis (CE) to detect any protein fragmentation, turbidity analysis, optical imaging to detect visible particles, and dynamic light scattering (DLS) for particle size analysis. Elective assays include microfluidic imaging for particle size analysis and reversed-phase ultra-high-performance liquid chromatography (RP-UHPLC) for placebo content determination.

Separately, MilliporeSigma has investigated the long-term stability of the excipients included in the SAFC® Viscosity Reduction Platform, particularly on the nine functional excipient combinations. This information provides real value to scientists because they can have confidence at the outset that these excipients are suitable for use in their formulations.

The overall goal of the Feasibility Testing Service is to design tailor-made excipient solutions for therapeutic protein candidates for each customer. Customers provide MilliporeSigma with samples of their protein of interest and experiments are performed in the application lab in Darmstadt. During the trials, intermediate results are communicated and discussed, and the studies are concluded with a detailed experimental report that is presented and provided to the customers. 

DA: To close, would you like to underline how the SAFC® Viscosity Reduction Platform and the Feasibility Testing Service fit into MilliporeSigma’s broader mission and the rest of the company’s offering?

AG: MilliporeSigma’s aim is to support its customers’ efforts to simplify drug formulation and reduce the time to market for new drugs desperately needed by patients. For this reason, in addition to the SAFC® Viscosity Reduction Platform, we offer a wide range of IPEC-GMP grade chemicals for the manufacturing and formulation of protein-based therapeutics (such as buffers, surfactants, salts, and stabilizers) and are continuously expanding our offering in terms of both products and services to target unmet needs.

The comprehensive portfolio for biopharmaceutical applications, together with innovative solutions and services like the SAFC® Viscosity Reduction Platform and Feasibility Services, backed by comprehensive regulatory support, enables formulators and researchers to overcome potential challenges in processing and formulation development.

Alana Gouveia

Alana Gouveia is a scientist in the Liquid Formulation R&D lab at MilliporeSigma in Darmstadt, working on highly concentrated protein formulations (HCPF). She is the global lead for the Feasibility Assessment Service offering. As such, she is supporting customers in the technology evaluation of the Viscosity Reduction Platform (VRP). Alana’s role is highly customer-oriented, and she has a profound experience working on highly concentrated antibody formulations. Alana holds a master’s degree from the Technical University of Darmstadt, where she focused on highly viscous protein formulation during her thesis.