Combination products are defined in 21 CFR 3.2(e) as therapeutic and diagnostic products comprising two or more regulated components, i.e., drug/device, biologic/device, drug/biologic, or drug/device/biologic, that are physically, chemically, or otherwise combined or mixed and produced as a single entity. This broad definition includes products ranging from pre-filled syringes to drug coated implants. For medical device companies, combination products provide an attractive route to improving product performance or extending a product’s lifecycle. In this article, we will explore polymer selection and design options for implanted drug-device combination products.
Polymer Selection for Combination Products
Broadly speaking, drugs and implants are used together for one of two reasons: 1. the device acts as a vehicle to deliver a drug or 2. the drug is included to enhance the performance of the device. For medical device developers, the most relevant examples involve the addition of a drug to an existing medical device. Antimicrobial catheters, steroid-coated pacemaker leads, and antibiotic bone cements are examples of traditional medical devices that are enhanced by the inclusion of a drug.
Polymer selection is a critical component of medical device development, and the same guidelines apply when choosing a polymer for a combination product. Combination product developers should ensure that their chosen polymer(s), as with any key component, will be available in the grade necessary for an implant and that the manufacturer can provide the needed documentation and support.
Pathway™ Thermoplastic Polyurethane (TPU) Excipients
A material showing increased use in combination products is thermoplastic polyurethane (TPU). Non-biodegradable TPU excipients, including Lubrizol Life Sciences’ Pathway™ offering, are versatile and customizable to a broad range of chemical and physical properties (Figure 1). The ability to modify TPU chemistry makes these excipients compatible with a wide range of APIs (hydrophobic and hydrophilic) and allows them to provide different drug-release kinetics (short and long-term) depending on the application. TPUs come in a range of durometers and are amenable to many processing methods, including hot melt extrusion, solvent casting, and injection molding. Lubrizol’s TPUs have a long history of in vivo safety, stability, and biocompatibility and, as a result, have been used for decades in biomedical applications such as implanted cardiac pacemakers and defibrillators. Additionally, Pathway™ TPUs have established Drug Master Files (DMFs) and are manufactured under IPEC-PQG good manufacturing practice guidelines, which is commonly required by the FDA when working with a pharmaceutical or incorporating one into a medical device.