On-Body Injectors Are Surging: How Large-Dose, High-Viscosity Biologics Are Moving From IV to Subcutaneous Delivery

Introduction

Biologics are getting more powerful—and often more concentrated, more viscous, and higher in delivered volume. At the same time, healthcare systems and patients are pushing for treatment models that reduce clinic visits and enable home administration. These forces are accelerating a major industry shift: converting some therapies traditionally delivered by IV infusion into subcutaneous (SC) self-administration using on-body injectors (also called wearable injectors).

Unlike conventional injection pens (typically designed for smaller SC volumes), on-body injectors are engineered for larger volumes and tougher formulations, delivered hands-free over a controlled period—often on the abdomen or thigh.

This article explains what on-body injectors are, why they’re trending, what technical hurdles they solve, and what this means for pharma and drug-device combination development.

1) What Is an On-Body Injector?

An on-body injector (OBI) is a wearable drug-delivery device that adheres to the body and automatically delivers a fixed dose subcutaneously—often over minutes to hours—without requiring the patient to hold a syringe or push a plunger continuously.

Many OBI platforms are designed as combination-product device components, meaning they are intended to be paired with a specific drug product and container configuration rather than sold as a “standalone consumer device.”

2) Why OBIs Are Rising Now

A) The “SC conversion” wave (infusion → subcutaneous)

A key driver is the push to convert some infusion therapies into patient-friendly SC delivery. BD, for example, announced a pharma-sponsored combination-product clinical trial using its BD Libertas™ wearable injector for SC delivery of complex biologics—explicitly highlighting the potential to move therapies from hospital/clinic infusion settings to more flexible care models including home use.

B) Larger volumes and higher viscosities are increasingly common

As biologics evolve, formulations can require more volume (or can’t be delivered comfortably via a quick push). Wearable injectors help deliver these doses slowly and consistently, which can improve tolerability and usability for at-home administration.

3) How OBIs Solve the “Large Volume + High Viscosity” Problem

Traditional pen platforms work well for many SC therapies, but they become challenged when:

• Volume increases beyond common pen ranges

• Viscosity rises, increasing injection force requirements

• Injection time must be extended to improve comfort

Wearable injectors address these constraints by:

• Delivering medication hands-free over a controlled rate

• Using mechanical or electromechanical drive systems to manage force

• Improving the user experience with guided steps and feedback (audio/visual cues), depending on platform

West’s SmartDose® platform, for example, explicitly discusses longer injection times as a way to improve comfort when delivering higher-viscosity products and references published research on the tolerability of larger-volume SC injections.

4) Real-World Examples of On-Body Injector Platforms

Below are representative examples showing how the category is being engineered (specs vary by platform and drug program):

BD Libertas™ Wearable Injector

• Designed for complex biologics and SC delivery

• States support for high-viscosity biologics up to 50 cP

• Offered in 2–5 mL and 5–10 mL configurations

• “Peel, stick, click” user flow; prefilled, patient-ready concept

Enable Injections enFuse®

• Wearable platform positioned for large-volume SC delivery

• States delivery range of 5–25 mL per device and compatibility with 1–100 cP viscosities (platform dependent)

West SmartDose® On-Body Delivery Systems

• SmartDose® 3.5: up to ~3.7 mL, wearable single-use device paired with a co-packaged prefilled container

• SmartDose® 10: up to 10 mL, battery-powered wearable OBI using a separate, pre-fillable polymer cartridge

These examples illustrate the broader trend: platform OBIs designed around volume/viscosity needs and patient usability, integrated into drug-device combination programs.

5) Key Design and Development Considerations (B2B Perspective)

If you’re evaluating OBI pathways for biologics “SC conversion,” these are common decision points:

A) Formulation constraints

• Viscosity profile over temperature range

• Compatibility with primary container materials (glass vs polymer; elastomers; silicone sensitivity)

B) Delivery time and patient comfort

• Rate control to reduce injection-site discomfort

• Managing back-pressure in SC tissue (especially for higher viscosities)

C) Human factors and usability

• Simple user steps (apply, activate, confirm delivery)

• Clear feedback (visual/audible indicators) and error prevention

D) Manufacturing and scale readiness

OBIs are combination products; scale depends on:

• Fill-finish alignment with the chosen container configuration

• Final assembly capability and in-process testing

• Partnering with CMOs/CDMOs for validated workflows

BD notes ongoing validation work with multiple CMOs for fill-finish and final assembly support.

6) What This Trend Means for the Future of Self-Injection

On-body injectors are not “replacing pens” across the board. Instead, the market is segmenting:

• Conventional pens / autoinjectors: ideal for many low-to-medium volume SC therapies

• Wearable OBIs: increasingly preferred for large volume, high viscosity, or extended delivery-time needs

As biologics pipelines grow and home-care models expand, OBIs are becoming a critical part of modern drug-delivery strategy—especially for programs targeting improved patient convenience and reduced infusion burden.