Children prescribed injectable biologics frequently failed to correctly administer doses, resulting in incomplete delivery ("wet leg" incidents).

The problem was initially attributed to injection speed, force, or patient anxiety during administration.

• Device ergonomics did not support small-hand grip stability
• Button mechanics were difficult to coordinate during injection
• Instructions were too complex to follow during active use
• Failure resulted from multiple interacting usability breakdowns, not a single mechanism issue

The device and instructions were redesigned to better support real-time use, including improved ergonomics and simplified step-by-step digital guidance. Failure rates decreased significantly and the program advanced through accelerated regulatory pathways.