Frequently asked questions

In core annular flow, two fluids (the sheath fluid and the core fluid) flow through the needle at the same time. The sheath fluid surrounds the core fluid in the needle, separating the core fluid from the needle wall. As a result, highly viscous core fluids can be easily transported through the needle. This unlocks patient-centric delivery of high-concentration, viscous therapeutics using narrow needles, small injection volumes and rapid injections.

The injection force for a core annular flow depends only on the sheath fluid viscosity, as the sheath fluid is the only fluid contacting the needle wall. The injection force can be estimated using the Hagen–Poiseuille equation with an effective viscosity of 4μ_sheath, where μ_sheath is the viscosity of the sheath fluid. As a result, core annular flow has been demonstrated to reduce injection force by more than 100× for highly viscous formulations.

Any formulation that is viscous. Force-reduction benefits start at ~10 cP, and CoFlo devices can manually deliver formulations up to around 10,000 cP. CoFlo has validated the approach on monoclonal antibodies (mAbs), polyclonal antibodies (pAbs), peptides, suspensions, small molecules, long-acting injectables, gels and more. The approach is physical, rather than biological or chemical: it only changes the way that the viscous fluid or drug flows through the needle. As a result, the core annular flow approach is chemistry-agnostic and broadly applicable to a wide range of formulations without requiring reformulation.

Yes. By reducing the injection force, core annular flow also reduces the shear that sensitive materials or molecules are exposed to. CoFlo has demonstrated aggregation prevention for shear-sensitive proteins.

There are only two requirements for the sheath fluid: (i) the sheath fluid should be a lower-viscosity fluid than the core fluid, in order to achieve the lubricant effect, and (ii) the sheath fluid should be chemically and biologically compatible with the core fluid. These requirements leave a wide range of options. The most commonly used sheath fluid is the saline buffer solution of the drug fluid itself, to guarantee stability and compatibility with the drug and the body. The sheath fluid can also be a second drug, a hyaluronidase, an oil, an alcohol and more.

The sheath fluid fraction is customizable. It can be brought as low as ~6% of the total injected volume, and has no technical upper bound. The sheath fluid is co-injected along with the drug.

The two fluids are only in contact for about 10–100 milliseconds as they flow through the needle. They therefore do not mix substantially despite being in contact. Once the two fluids are injected into the body, they will mix in the injection site depot.

Stability and viscosity are two separate constraints on drug product development, both of which become more problematic at higher concentrations. The role of each is different for each molecule, and many therapies are primarily limited by viscosity before they become unstable. CoFlo has worked with stable antibody formulations up to 400 mg/mL. Additionally, by eliminating the viscosity delivery constraint, it becomes possible to optimize the formulation excipients for stability, rather than viscosity, resulting in a more stable formulation.

High-viscosity formulations are common for high-dose and high-concentration applications, as well as depot-forming materials. Core annular flow reduces the injection force for high-viscosity formulations, unlocking their delivery. The opportunities that core annular flow unlocks can be grouped into four categories:

• Intravenous-to-subcutaneous transition for therapies > 300 mg
• Aiding delivery and improving the release profile of long-acting injectable systems
• Dual-drug delivery
• Reducing the burden of existing subcutaneous delivery by increasing concentration to reduce volume and improve patient experience

As small as 30 gauge and as large as 20 gauge.

Core annular flow eases delivery of high-viscosity fluids through needles, so the approach can unlock delivery in any needle-based route: subcutaneous (SC), intravitreal (IVT), intramuscular (IM) and more.

Our GenOne and Double Barrel systems have been developed for convenient single-step assembly. The GenOne needle hub connects to a prefilled syringe via a standard Luer lock connection. The Double Barrel device consists of a cassette that contains two prefilled syringes, which snaps onto the CO-AXL hub in a single assembly step.