By Chris McKenzie, Battelle
Exciting new developments in drug delivery are creating unprecedented opportunities for medical device developers. However, in the rush to get to market, it’s easy to make expensive — and potentially dangerous — development missteps. Here are five steps that device developers can take to ensure their final device fully meets technical, user and regulatory requirements.
Build An Effective Theoretical Model
You’ve got a great idea for a novel drug delivery device, and your initial prototype works (more or less). That’s great! But do you understand why it works?
Often, manufacturers move into device development without fully understanding the science and engineering theory behind their device. The device may be a variation on something already on the market, or it may be something new, based on the designer’s intuition and prior knowledge. Before finalizing your design, you should make sure that you fully understand the science and engineering principles behind it and be able to build a mathematical model of how it works.
For example, the theoretical model for drug delivery time in a new auto injector might include variables like:
- Device characteristics, including the force of the spring, the friction in the syringe, needle bore, length and syringe barrel volume
- Environmental factors, such as temperature and humidity
- Drug formulation variables, such as volume and viscosity
An effective model is highly predictive, allowing you to determine which variables you need to adjust in your device design to achieve desired performance. Empirical testing is performed to validate the model. If empirical testing using prototypes does not correlate to the model, you know there is a gap in your understanding of the science behind your device and/or issues with the parts used in testing. Additional testing and model development will allow you to fill in these gaps in understanding.
An effective model, demonstrating solid understanding of the science and engineering theory the device is built on, will speed up development by allowing designers to predict device performance sensitivity as design inputs are altered. This sensitivity analysis also can help the technical team determine the design’s “sweet spot” and margin between acceptable and unacceptable performance. It also will help you reduce potential risks by understanding predicted performance under a variety of potential design and use scenarios.
Prove Your Core Technology
As you develop a solid theoretical model, you need to continue testing your prototypes to make sure they perform predictably under reasonably expected environmental conditions and use cases. While successful performance at nominal conditions is a good first step, consider evaluating performance at a wider range of conditions sooner rather than later. The earlier you can more completely challenge your core technology, the less likely you are to encounter avoidable and expensive problems further along the development timeline.
One important aspect that some designers neglect is product performance after aging. Your core technology may perform perfectly out of the box, but do you know how it will perform after six months, one year or five years of use? Accelerated aging studies can give you important insights into potential risks and liabilities for your product once it is released. These evaluations should be performed during early prototyping, as any design weaknesses identified can be more efficiently addressed — and for less money — during this stage of development than after design freeze.
Understand Your Technical Team’s Limits
Do you have materials science expertise on your team? Finite element analysis? Design for assembly? While large device manufacturers may have vast design and engineering departments, most smaller device developers work with a small core team of engineers who wear many engineering “hats.” Whether you have a large or small team, it’s important to objectively and accurately assess their strengths and weaknesses and to identify areas where you may need help from an outside subject matter expert. Beyond basic engineering design, key consideration should be given to such areas as:
- Mathematical model development
- Materials selection
- Accelerated aging
- Human factors
- Usability testing
- Finite element analysis
- Prototype development
- Design for manufacturing
- Design reviews
Early in the project, gaps in expertise may be considered risks. A realized risk is an issue, and issues don’t usually occur at convenient times during the project. If you don’t have clear expertise in-house, consider bringing in consultative support. The right external resource can be an invaluable asset to quickly mitigate gaps in technical expertise.
Don’t Neglect the Human Element
Human factors testing is required for regulatory approval. However, medical device developers should consider human factors and usability issues at every stage of design. No matter how well your device performs technically, if users are not able to use it correctly, or it does not fit easily into user routines, it is not likely to be accepted in the market.
Human Centric Design (HCD) is an approach to device development that puts the end user at the center of all design decisions. By considering human factors and usability issues from the very beginning of the design process, medical device developers can avoid costly redesigns prior to market release. They also will uncover unexpected insights that can significantly increase market acceptance and, ultimately, sales.
Challenge, Challenge, Challenge
It can’t be said enough: test your device design early and often. Design reviews are not just for the end of the development process. You should be continually challenging your design assumptions, evaluation results and plans at every stage of development, from initial concept to final product.
Early design reviews can save considerable time and money later on. The earlier you find and fix a potential problem, the more cost effective that fix will be. Correcting problems with a device during final verification and validation can be many times more expensive than making corrections at the design phase and will cause considerable delays in your market release schedule.
Often, early-stage design reviews will uncover bad assumptions or limited engineering skills that lead to problematic design choices. For example, a junior engineer at one company designed a device component under load and even went so far as to perform finite element analysis using a readily available software package. Unfortunately, while the staff member could use the software, he did not properly interpret the results. This miss led to the aged component failing. The company did not find the error until the final verification testing, at which point it had to go back to the drawing board, delaying product launch for months. Another company discovered immediately before FDA submission that its drug delivery device didn’t meet a key regulatory requirement. That’s why it’s important to have multiple perspectives during the design review process, including human factors, engineering and regulatory experts.
It’s important to bring independent expert reviewers into the process early in the development cycle. Instead of thinking of independent review as a simple “box checking” exercise for FDA submission, you should consider outside reviewers an important part of your development team. An objective, outside expert opinion at key points in the design process can pinpoint areas that need further attention and suggest changes that will increase the likelihood of technical success.
Taking these critical steps will add some time and money to your design and development process. However, the time spent up front to build and understand theoretical models, test your assumptions and technology, and integrate iterative design reviews into your processes will more than pay for itself when it comes time for successful design verification, regulatory approval and market release. Done right, these five steps will result in better, safer and more competitive medical devices.
About The Author
Chris McKenzie has more than 20 years of experience developing medical devices. He has led medical device development programs at a small device developer/manufacturer, a Fortune 500 pharmaceutical company and, most recently, at Battelle.