Enabling faster subcutaneous delivery of larger volume, high viscosity fluids.

Objectives: Many current subcutaneous (SC) biologic therapies may require >1 mL volume or have increased viscosity, necessitating new delivery system approaches. This study evaluated 2-mL large-volume autoinjector (LVAI) delivery performance across varying solution viscosities and design inputs to assess the design space and identify configurations that produce practical injection times.

Methods: Investigational LVAI delivery duration and volume, depot location, and tissue effects were examined in both air and in vivo models across various pre-filled syringe (PFS) cannula types (27 G Ultra-thin wall [UTW], 27 G special thin wall [STW], or 29 G thin-wall [TW]), drive spring forces (SF or SF), and Newtonian solutions (2.3-50 centipoise [cP]).

Results: Within each design configuration, increasing PFS internal diameters and spring forces reduced delivery times, while increasing viscosity increased times. The 27 G UTW PFS/SF combination achieved shorter delivery times across all injection conditions, with 2 mL in vivo durations <15 seconds at ≤31 cP and routinely <20 seconds at 39 and 51 cP, with nominal and transitory tissue effects.

Conclusion: PFS cannula and spring force combinations can be tailored to achieve various injection durations across viscosities, while UTW PFS enables faster rates to potentially better accommodate human factors during LVAI injection, especially at high viscosity.