Design Differences and Usability Risks in GLP-1 Pen Injectors: A Comparative Study of a Generic and Reference Device

To provide preliminary insights into whether a proposed generic combination product injector for glucagon-like peptide-1 (GLP-1) receptor agonist administration can be substituted for the delivery device constituent part of the Reference Listed Drug (RLD) without the need for additional training or health care provider intervention for Abbreviated New Drug Application (ANDA) submissions. A preliminary comparative use Human Factors study was conducted with 14 participants experienced with the RLD, including patients and caregivers. Participants simulated critical tasks using a delivery device constituent part of both the proposed generic combination product and the RLD. Observational data, use error rates, and subjective feedback on acceptability and ease of use were collected and analyzed. The overall use error rate was slightly higher for the proposed generic combination product (79%) compared to that of the RLD pen (71%), corresponding to one additional participant experiencing failure. Most use errors were not attributed to differences in external critical design attributes but rather to user habits or procedural misunderstandings. Notably, 93% of participants demonstrated similar usability profiles across both devices. Design differences, such as the outward translation of the dose set knob and increased injection force of the proposed generic combination product, were associated with a small number of use errors, but these were resolved after a single use, indicating a rapid learning effect. Acceptability and ease-of-use ratings were high for both devices, with 87% of participants expressing comfort in switching between them. Despite "other design differences", the proposed generic combination product injector demonstrated comparable usability to the RLD pen without additional risks. Most observed use errors were not device-specific and were resolved quickly, suggesting limited clinical impact in real-world use. These findings support the potential substitutability of the proposed GLP-1 generic combination product for the RLD and contribute to de-risking the final comparative use Human Factors evaluations required for ANDA.