This year, 11 of the 54 safety alerts issued by the FDA were for the presence of particulates in drug and therapeutic biological products.1 The organization tasked with compiling the official compendia of guidelines for particulate matter, the U.S. Pharmacopeia Convention (USP), set quantifiable limits for particulates in USP chapter <788>, and with the subsequent USP <787>, opened the door for broader regulation. According to Dr. Satish Singh, a member of the USP Expert Committee working on the USP <787>, “Although current historical USP limits of ≤ 6000 and ≤ 600 particles/container may be applied,” a reference to the quantifiable limits set by USP <788>, “the most appropriate limits for biotechnological products will depend upon the specific product and manufacturing process and taking into account the clinical safety and efficacy data as well as dose and route of administration.”2
In June of next year, USP will hold a series of seminars entitled “Control and Determination of Visible and Subvisible Particulate Matter in Biologics” to address the latest technologies and issues in the characterization of particulate matter. These seminars will likely set the stage for the organization to adopt stricter guidelines for particulates in drug and biological therapeutics. To prepare for more stringent guidelines, U.S. pharmaceutical companies producing drug and therapeutic biologics should understand at what point particulate matter manifests during the manufacturing, shipping, handling, or administration processes, as well as the most recent advancements in particle characterization technology.
Particle characterization is instrumental in determining whether par-ticles present in pharmaceutical product can be classified as either 1) inherent: particles that originate from the drug product itself, such as protein agglomerates; 2) intrinsic: non-protein particles that are introduced during the manufacturing and packaging (such as glass, silicone oil, stainless steel, etc.); or 3) extrinsic: particles that are neither inherent nor intrinsic, that is, do not arise during manufacturing processes but instead come from environmental contamination (such as textile fibers, insects, hair, rust, etc.).
For pharmaceutical companies, the analysis of particles has been a longstanding challenge in drug development and quality control measures because the degradation of the actual active constituents of the pharmaceutical product may be responsible for inherent particulate matter.3 To further complicate the issue, interactions between the active pharmaceutical ingredient (API) and its excipients with downstream administration methods such as tubing, syringes, etc., may cause the formation of intrinsic particulate matter. These interactions also include the way the product is transported to the actual site of administration, since different shipping and handling methods may form agglomerates that would otherwise not be present in the product. This means that when manufacturing a drug or therapeutic biologic, companies must take into consideration many disparate possibilities of transportation, storage, and usage, even extreme examples such as hospitals that use a pneumatic tube to transport the pharmaceutical throughout the facility.4
Beside the safety concerns associated with particulate matter in pharmaceuticals—such as thrombogenesis, impaired microcirculation and modulated immune response5—particulate matter can also negatively affect the efficacy of a therapeutic by interacting with the API and/or its excipients. For example, the interaction with particulate matter could accelerate the degradation of, interfere with, or inhibit the pharmaceutical compound.
Which particle characterization method to use depends on the size of the particle. For visible particles, that is particulates greater than 100 μm, Raman spectroscopy that uses a laser-based microscope device is a viable option. Raman spectroscopy is a common technique used in chemistry to identify molecules via a “fingerprint” by categorizing a diverse range of compounds by analyzing vibrational, rotational, and other low-frequency modes. Typically, Raman spectroscopy will be used for visible particles after they are identified with a simple visual inspection of the sample.
Raman spectroscopy is also an option for smaller subvisible particles, between 100 μm and 1 μm, but several other technologies exist at this level as well. At the higher end of the subvisible particle spectrum, Microflow imaging (MFI), which uses flow microscopy of particles contained in a solution based on size, has been shown to be complementary to Archimedes, a resonant mass measurement (RMM) technique based on buoyancy and resonance of the particles. Using these two techniques in concert has been recommended for “a comprehensive analysis of biotherapeutics potentially containing silicone oil droplets and protein particles in the submicron and micron size range.”7
Biosimilars are pharmaceutical and biological products approved by the FDA for use because they have been shown to be highly similar to an already approved product. This means that there are no meaningful differences in safety and effectiveness from the reference product, i.e. the product already approved by the FDA. The only allowed differences are “minor differences in clinically inactive components.”9
Biosimilars, however, have been shown to display different particle profiles, especially when characterized using complementary techniques. The implications of these different profiles are important for pharmaceutical companies to understand because they could potentially mean unique interactions with downstream processes such as shipping, handling, and administration, and therefore the biosimilar could become victim of a recall when the reference product is not.
Archimedes is also capable of particle characterization at the nano level, that is, particles measuring from 1 μm to 1 nm. Size-exclusion Chromatography (SEC), a nearly 50-year-old technique that is still the primary means of routinely measuring protein aggregate levels,8 has continued to evolve and is now capable, when combined with a multi-angle light scattering (MALS) analysis (SEC-MALS), of characterizing particles on the 500 nm to 10 nm range. Two techniques that characterize particles by measuring Brownian motion are Nanosight (NTA) and Dynamic Light Scattering (DLS) — both good options for the 1 μm to 10 nm range. Furthermore, DLS can be paired with Raman Spectroscopy to give a more detailed particle profile. Lastly, TDA Viscosizer technology that uses an automated microcapillary flow-based system with UV area detection is capable of molecular sizing in solution and relative viscosity measurements at the 50 nm to 0.2 nm range.
Inline filtration has shown benefits in the treatment of critically-ill pediatric ICU cases, which may be attributed to a reduction in particulate matter.5,6 In the “Complementary Techniques for Particle Characterization” webinar, Amber Fradkin presents results from an experiment designed to test if inline filtration actually reduces the number of particles in solution.
The group begins by profiling the particles of a solution using the flow microscopy MFI. After running the solution through a 20 micron filter, they again profile the solution using MFI and see little difference. The solution is run through a 0.2 micron filter and we see a marked reduction in particles. The before and after MFI results are compared with Archimedes (RMM) which indicates that the reduction was both in non-silicon and silicon particles — a distinction that MFI is unable to categorize alone. Next, the group wanted to determine if the non-silicon particles were protein, something that the Archimedes (RMM) and MFI combined were still unable to distinguish. Using SEC-MALS, and paralleling with data from the other two profiles, the group was able to tell that the non-silicon particles were proteinous.
Mr. Walker is the founder and managing director of That’s Nice LLC, a research-driven marketing agency with 20 years dedicated to life sciences. Nigel harnesses the strategic capabilities of Nice Insight, the research arm of That’s Nice, to help companies communicate science-based visions to grow their businesses. Mr. Walker earned a bachelor’s degree in graphic design with honors from London College of Communication, University of the Arts London, England.