Shawn P. Davis

Arrays of micrometer-scale needles could be used to deliver drugs, proteins, and particles across skin in a minimally invasive manner. We therefore developed microfabrication techniques for silicon, metal, and biodegradable polymer microneedle arrays having solid and hollow bores with tapered and beveled tips and feature sizes from 1 to 1,000 microm. When solid microneedles were used, skin permeability was increased in vitro by orders of magnitude for macromolecules and particles up to 50 nm in radius. Intracellular delivery of molecules into viable cells was also achieved with high efficiency. Hollow microneedles permitted flow of microliter quantities into skin in vivo, including microinjection of insulin to reduce blood glucose levels in diabetic rats.

Abstract: Subcutaneous (SC) delivery of biologics has traditionally been limited to fluid volumes of 1– 2 mL, with recent increases to volumes of about 3 mL. This injection volume limitation poses challenges for high-dose biologics, as these formulations may also require increased solution concentration in many cases, resulting in high viscosities which can affect the stability, manufacturability, and delivery/administration of therapeutic drugs. Currently, there are technologies that can help to overcome these challenges and facilitate the delivery of larger amounts of drug through the SC route. This can be achieved either by enabling biologic molecules to be formulated or delivered as high-concentration injectables (> 100 mg/mL for antibodies) or through facilitating the delivery of larger volumes of fluid (> 3 mL). The SC Drug Delivery and Development Consortium, which was established in 2018, aims to identify and address critical gaps and issues in the SC delivery of high-dose/volume products to help expand this delivery landscape. Identified as a high priority out of the Consortium’s eight problem statements, it highlights the need to shift perceptions of the capabilities of technologies that enable the SC delivery of large-volume (> 3 mL) and/or high-dose biologics. The Consortium emphasizes a patient-focused approach towards the adoption of SC delivery of large-volume/high-concentration dosing products to facilitate the continued expansion of the capabilities of novel SC technologies. To raise awareness of the critical issues and gaps in high-dose/volume SC drug development, this review article provides a generalized overview of currently available and emerging technologies and devices that could facilitate SC delivery of high-dose/volume drug formulations. In addition, it discusses the challenges, gaps, and future outlook in high-dose/volume SC delivery as well as potential solutions to exploit the full value of the SC route of administration. Keywords: high-dose biologic, drug delivery technologies, subcutaneous drug delivery, intravenous drug delivery, patient preference, large-volume subcutaneous delivery