Enabling high-viscosity biologic delivery with Molly autoinjector and Stevanato Group's syringes
January 05 2026
![[.jpg] Image of Molly 2.25 mL autoinjector and a pre-filled syringe configured for high-viscosity biologic delivery.](https://cdn.bfldr.com/DTG6CG68/at/6fcp2h99v3hrb78mfjmc9z/device-primary-container-partner-plug-play.jpg?width=480&auto=webp&format=webp)
As biologics continue to evolve, drug developers are increasingly challenged by larger subcutaneous injection volumes and high-viscosity formulations. Many next-generation monoclonal antibodies, bispecifics, and GLP-1–based therapies now exceed the traditional comfort limits of classic autoinjectors, pushing beyond 1.0 mL volumes and 15 cP viscosity.
At injection volumes of 2.0 mL and viscosities up to 30 cP, standard autoinjectors paired with conventional pre-filled syringe designs can result in injection times exceeding 20-30 seconds. To address this limitation, SHL Medical and Stevanato Group collaborated on a study demonstrating that large-volume, high-viscosity biologics can be reliably and comfortably self-administered using SHL Medical’s Molly® 2.25 mL autoinjector in combination with Stevanato’s Alba® and Nexa® pre-filled syringes.
A platform-to-platform approach for high-viscosity delivery
Rather than treating each drug-device combination as a bespoke development effort, the teams adopted a shared platform-to-platform integration strategy. The goal was to define and validate a common design space upfront, helping de-risk combination product development and reduce late-stage uncertainty.
The Molly 2.25 mL autoinjector was evaluated with Stevanato’s Alba special-thin-wall syringe as well as Nexa thin-wall and special-thin-wall syringes. Both configurations used 27G needles, with additional testing performed using an 8 mm needle length to further optimize delivery performance and patient experience.
Comprehensive performance across viscosity ranges
To fully characterize system performance, the integrated pre-filled syringe and autoinjector configurations were evaluated across a broad viscosity range from 1 to 30 cP. Testing covered key parameters, including break-loose and extrusion forces in accordance with ISO 11040-8, cap removal force, and injection time as a function of both viscosity and delivered volume.
Hydrodynamic pressure drop was also modeled using the Hagen-Poiseuille equation adapted for power-law fluids, enabling a deeper understanding of flow behavior at higher viscosities. Together, this approach allowed the teams to map performance boundaries and identify optimal configurations for high-viscosity biologic delivery.
![[.png] hagen-poiseuille-equation-used-study](https://cdn.bfldr.com/DTG6CG68/at/v67zjgmr55mmhcjc85hxwqjs/hagen-poiseuille-equation-used-study.png?width=480&auto=webp&format=webp)
Measurable gains in injection time
By combining Molly’s high-torque spring with Stevanato’s larger-bore Alba and Nexa pre-filled syringes, the study demonstrated significant reductions in injection time compared with legacy systems adapted beyond their original design intent.
For a 2.0 mL formulation at 30 cP, average injection time was reduced from more than 25 seconds to just 8-12 seconds, while maintaining glide forces well below 15N. This represents a reduction of more than 60% in injection time, achieved without compromising system robustness or usability.
Equally important, the full design space was mapped and de-risked upfront. Drug developers selecting either Alba or Nexa pre-filled syringes now benefit from pre-validated compatibility data with the Molly 2.25 autoinjector, supporting shorter development timelines and reducing late-stage technical risk.
Key takeaways
● Platform-based integration supports program progression.
Early alignment between device and primary container partners allows high-viscosity biologic programs to move forward with reduced development risk and fewer late-stage design changes.
● Syringe geometry is a critical enabler for high-viscosity delivery.
Thin-wall and special thin-wall pre-filled syringes improve flow performance, with flow-rate gains scaling with the fourth power of internal diameter.
● Optimized systems support patient comfort.
By combining optimized syringe designs, short needles, and autoinjectors with increased drive capability, 2.0 mL formulations at 30 cP can be delivered in injection times comparable to today’s 1.0 mL devices, delivering lower-viscosity formulations (10 cP), helping maintain patient comfort as biologic therapies continue to advance.
The study was presented at the PDA Universe of Pre-filled Syringes and Injection Devices 2025 as a joint SHL Medical-Stevanato Group poster. To learn more about the study, please contact SHL Medical team.