Assessment of penetration depth and delivery performance of a novel intradermal drug delivery device

1 INTRODUCTION
Intradermal (ID) injection has gained renewed interest due to its dose-sparing potential in light of the recent Sars-CoV-2 pandemic and the mpox health emergency. Indeed, studies have shown that ID vaccination with up to 1/10th of the dose typically administered intramuscularly, can elicit a non-inferior immune response.
The aim of the study was to create a mathematical model for ID injection using novel delivery device VAX-ID® by (i) building a model that allows defining penetration versus delivery depth; (ii) verifying the metrics using imaging technology; (iii) validation in a preclinical setting in piglets.

2 MATERIALS & METHODS

The device is composed of a housing, a foot, a short hollow needle and a safety pin. To guarantee skin penetration at a predefined depth, VAX-ID has a friction and acceleration mechanism that prevents skin-tenting associated with external leakage.
2.1 Mathematical model
Key elements of needles ranging from 32 to 27G were taken into account, including: (1) primary bevel (e.g. 10°), secondary lancet (e.g. 60°) and tip cuts angles (e.g. 19,2°); (2) the needle's outer diameter; (3) inner diameter; (4) wall thickness; and (5) manufacturing tolerances.
2.2 3D CAD and CFD model
3D Computer Aided Design (CAD) models of needle geometry and device components were configured and assessed using Computational Fluid Dynamics (CFD).
2.3 Visual inspection
Consequently, prototypes were built. Pixel based imaging was used to assess the protruding needle length.
2.4 Delivery performance in piglets
To gain pre-clinical evidence on performance of VAX-ID, two piglets (12kg) received each 9 injections (back, neck, abdomen) with a dye.

3 RESULTS
3.1 Analytical assessment
Mathematical and computational analysis, taking manufacturing allowance into account, gave clear theoretical values and visual representation of (i) penetration and (ii) delivery depth, ranging from 0.07mm up to 1.40mm.
3.2 Visual inspection
Visual inspection confirmed the protruding length of the tip on 100+ devices.
3.3 Delivery performance in piglets
Histology of piglet dermis showed clear deposit of dye in the dermal layer of the skin, without internal leakage to the hypodermis.

4 CONCLUSION
The predefined penetration and delivery depth of VAX-ID® allows reliable ID injection. The mathematical model will enable different variants targeting a variety of depths that can be used for a broad range of prophylactic and therapeutic vaccines.

Authors

K. CL Beyers(1), D. Scalco Vasconcelos(1), M. Rbeihat(1), V. VJ Vankerckhoven(1)

Organisations

Idevax BV(1)

Presenting author

Koen Beyers, Founder, Director, Idevax BV
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