How to develop wearable medical devices
Tom McLean, vice president, integrated delivery systems research and development, West Pharmaceutical Services discusses the challenges associated with developing plastic wearable medical devices.
There are many challenges associated with developing wearable medical devices which can be customised to meet both the healthcare provider and patient’s needs.
The approach
A platform approach works by attempting to create the the design of a wearable delivery system with maximum design flexibility, whilst meeting as many applications and customer and patient needs as possible. In order to implement this platform approach during development some conflicting design requirements must be dealt with, which can be categorised into the following areas:
- The intended user/patient population and their specific needs. E.g. age, gender, BMI
- Therapeutic characteristics such as the frequency of dosing (E.g. daily) the dose volume, delivery time, delivery rate (E.g. bolus injection) and the delivery location on the body
- Molecule/drug characteristics such as drug viscosity, temperature (cold chain), ultra violet or light sensitivity, and shelf life
- Business and marketing considerations including product cost, the ability to differentiate or brand, and the ease in which the wearable and drug product are consolidated into the final combination product
By understanding these conflicting application and user requirements from the start, West Pharmaceutical Services is able to define which product features are fixed, which are designed to operate within a range and which features can be customised for a customer’s application.
Meeting expectations
In terms of expectations for manufacturers from regulatory agencies, there is currently a potential lack of clarity. This is because wearable devices are still very new to the industry, with only a few products receiving marketing approval up to now.
West Pharmaceutical Services is actively involved with the international standards organisations (ISO TC 84) that are developing guidance for wearable delivery systems (E.g. on-body delivery systems) to ensure we understand the expectation of not only the regulatory agencies but also all stakeholders. The company also work closely with customers and participate in meetings with the regulatory agencies for specific applications, in order to ensure adherence to regulatory expectations for each application.
One example of a new expectation from the regulatory agencies is demonstrating the consistency of dose delivery over the defined delivery time for a wearable device. Most delivery systems (pen injectors, pre-filled syringes, auto-injectors) in the market today have not needed to demonstrate delivery consistency due to their lower delivery volumes (less than 2mL) and delivery times (typically less than 15 seconds). Wearable devices typically intend to deliver larger volumes over a longer time. There is a need to define a delivery profile (delivery volume over time curve) with limits, and to demonstrate from this that the device can consistently meet this defined curve - this can often be a challenge for many wearable delivery technologies.
Ensuring quality
As manufacturers it’s important to ensure that you maintain quality expectations, and quality starts with how the product is designed and developed. West Pharmaceutical Services follows a stage gate product development process where we assess the performance of the product and manufacturing processes against pre-defined requirements at each gate.
The company also utilise theoretical analysis tools (E.g. MoldFlow) during the early stages as part of the design for excellence (DFx) program, whilst the statistically based testing plans throughout development help to provide confidence in the product reliability. Once a product is developed and out on the market, West Pharmaceutical Services has a dedicated team that conducts market vigilance of the product, assesses any issues observed in the field and looks at data trends for any signs of potential quality issues. This information is then fed back to the development team for potential product improvements.
User research and human factors studies are critical when making wearable devices. This is because firstly, it is an expectation from the regulatory agencies that you have conducted human factors studies and have submitted this as part of a marketing application. Additionally, it is vital to have a good understanding of the user, the use environment and the challenges of the specific therapeutic application as you develop a wearable device. The information gained from these types of studies leads to specific requirements and product features that ensure a patient is able to use the product and receive their therapy as intended. At West Pharmaceutical Services we consider things like:
- Form Factor that provides a positive response from the user
- Ease of use, starting with how the product is removed from the packaging through the completion of the dose
- Understanding how to use and gain confidence when using the delivery system
Material choice
It can be challenging deciding which materials to use. When selecting materials for wearable devices, West Pharmaceutical Services first looks for material types that are fit for use within the wearable delivery technology – whether that is a polycarbonate, acrylonitrile butadiene styrene or another type of polymer. We then determine if there is proven biocompatibility for medicinal use, and if not, we will conduct testing at an independent, third-party facility to ensure that all industry standards are met.
In addition, we seek out materials whose continuity of supply is most reliable. Patients rely upon drug delivery technologies to ensure adherence to their prescribed therapeutic regimens; thus, reliability is crucial. Dual-sourcing options or a business continuity plan is essential from a procurement perspective when selecting any material used within the device.
Conclusion
The ultimate goal is for a patient to want to use the wearable delivery system as prescribed, because it is compliant with their therapeutic regimen and therefore results in desired health outcomes for the patient.