Pure polymers, pure excellence – decades of setting the standard with RESOMER® parenteral functional excipients

Evonik has been delivering its portfolio of RESOMER® parenteral functional excipients to formulators developing complex injectable drug products for more than 30 years. Lactide/glycolide-containing polymers have a long safety record, have been used with small molecules, peptides, proteins, nucleic acids, and other drug substances, are biocompatible, and are 100 percent bioabsorbable in the body. With a shelf life exceeding five years and amenability to terminal sterilization with ionizing radiation, RESOMER® is the most versatile polymeric excipient available on the market. 

In this interview, Drs. Whitney Moro, Director Technical Marketing Parenteral Products, and Tom Tice, Senior Director Strategic & Technical Marketing at Evonik, discuss what sets RESOMER® apart.

1. Can you tell us a little bit about the history of Evonik's RESOMER® bioabsorbable polymer portfolio?

Tom: Evonik's bioabsorbable polymer portfolio has a long and rich history – a pioneering history, in fact. The company’s polymer expertise and scientific contributions date back to the 1970s, before commercial lactide/glycolide-containing (LG) polymers were even available. During these early years, for example, we established the industry standard for LG polymer compositions – lactide/glycolide ratios of 50:50, 65:35, 75:25, 85:15 and 100:0. These same standard compositions are used even today in publications and commercial products.  

The RESOMER® brand was launched in the 1980s as the first commercial source of solvent-purified LG polymers. The first approved PLG-containing drug delivery product went on the market around that same time. This product incorporated both bioabsorbable polymers and formulation technology from Evonik. Having acquired the two oldest polymer brands in the U.S. (Lakeshore Biomaterials and LACTEL® Absorbable Polymers), the first patented polymer purification technology (Boehringer Ingelheim, 1987), and by providing drug delivery formulation services for decades, there is no one company in the world that manufactures, purifies and formulates with LG polymers other than Evonik.


2. What sets this portfolio apart today? 

Whitney: Polymers are tricky to make, and it's essential to understand the science behind them, build the capabilities to purify them, and develop the known-how to make and analyze them reproducibly. If consistency is the most important attribute in a commercial polymer source, purity is a close second. Polymers with low residual monomers are essential for certain applications, but efficient solvent purification requires a lot of expertise—not to mention some very sophisticated equipment! At Evonik, our polymer portfolio has been built by formulators with formulators in mind, resulting in a unique portfolio that includes zero-tin polymers (RESOMER® Zero), polymers with ultra-low residual monomers, and the ability to meet extremely narrow inherent viscosity requirements (RESOMER® Precise). No one has more history or higher quality in this field. 


3. Can you explain the benefits of using the bioresorbable polymers RESOMER® in parenteral drug delivery? 

Tom: RESOMER® is a portfolio of unique bioresorbable, polyester polymers with many inherent properties that make them ideal for long-acting, parenteral drug delivery. These polymers have glass transition temperatures above 37 °C, which means drug release is not influenced by body temperature. They are broken down with only water (by hydrolysis), so enzymes in the body are not required for degradation. When these polymers break down, the products formed are lactic acid and glycolic acid, which are part of the Kreb cycle. So, these acids are fully absorbed by the body. 

Whitney: LG polymers also have a long-standing safety record and have been approved by regulatory bodies around the world for use in medical devices since 1971, and drug delivery products since 1986. With all this market success, however, it’s important to keep in mind that working with these polymers is quite complex. Formulators need to understand the chemistry of these polymers and how their attributes contribute to the release of their unique APIs. Unlike other excipients, LG polymers can be tailor-made for each formulation to align polymer properties with drug properties and the required formulation attributes. Because there are so many LG polymer characteristics that can be manipulated for product performance tuning, developing a final product can be time consuming. That is why it is critical to partner with a reliable, quality polymer supplier in the beginning stages of a drug delivery project! 


4. In what types of formulations is RESOMER® used? 

Tom: The RESOMER® portfolio has been used in a variety of complex parenteral formulations, including local delivery in the knee, sinus and eye, with more applications sure to come! New products, such as LG polymer nanoparticles for immunotherapy, continue to support the modalities of unmet medical needs.  

Whitney: When we look at the components of a successful formulation, we’ve found that polymer experts and formulation teams working hand-in-hand is key. This strong synergy is crucial for timely development of a long-acting formulation. For example, we know from 40+ years of formulating with LG polymers that certain drugs (especially peptides and some small molecules) require extremely low monomer residuals in these polymers to prevent formation of drug impurities and conjugates. The RESOMER® Zero process was designed specifically with this in mind.


5. Why is a strong regulatory affairs group important for formulators working with RESOMER®? 

Whitney: A strong regulatory group is essential! When a pharmaceutical company files a new drug product, they rely on their excipient manufacturer to have a strong framework already in place. Evonik retains Master Files (DMFs and MAFs) with FDA and equivalent documents with other international regulatory bodies. This infrastructure ensures that relevant data and documentation are ready at all times to support clients’ regulatory filings. 

Tom: Regulatory agencies are becoming more interested in excipients in recent years—in some cases, facing almost as much scrutiny as the drugs themselves. So it’s becoming even more important to secure excipient suppliers with a strong regulatory presence to ensure that the excipients used in parenteral formulations meet current regulatory requirements.


6. Why do customers benefit from a global network for production and sales? 

Tom: Having a global network for production and sales provides security of supply, plain and simple. Evonik has two manufacturing sites on two continents, which ensures that customers can receive their products even if there are disruptions at one location.  

Whitney: This global network also allows Evonik to provide local support to customers, which is critical for complex parenteral formulations. This local support includes everything from technical assistance, to regulatory support and supply chain management. 


7. Any closing remarks? 

Tom: When it comes to developing complex parenteral formulations like long-acting injectables, formulation manufacturing processes such as microencapsulation, nanoencapsulation, and hot melt extrusion depend on the inherent physical and chemical properties of the LG polymer. Consequently, it is crucial to start formulation development using LG polymers with properties that are close to what you want, rather than trying to save time by getting a quick sample. Investing time at the beginning of drug product development will save time later and prevent problems down the road.  

Whitney: Don't cut corners and compromise the quality of your product! Choosing a company with a long history, robust track record and the experience to make these complex parenteral formulations will keep you on the path to success. At Evonik, we understand the importance of excipient quality and the impact it can have on the drug. We also understand the relationships between product-by-process formulation manufacturing, drug product composition and tuning the properties of RESOMER® polymers. That's why we offer a range of bioabsorbable polymers, including our RESOMER® portfolio, which provides a safe, effective, and reliable platform for drug delivery. 


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