Enabling high-viscosity biologic delivery with Molly autoinjector and Stevanato Group's syringes

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 50 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 needle as well as Nexa thin-wall and special-thin-wall needle. 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 50 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.  

Measurable gains in injection time  

By combining Molly’s platform technology with Stevanato’s 8 mm needle, the study demonstrated significant reductions in injection time compared with legacy systems adapted beyond their original design intent.