The Versa™ platform is covered by an extensive intellectual property library and is responsible for the two FDA approved drug delivery products – Vitrasert® and Retisert®. It is based on a core of solid drug, coated with a semi-permeable polymer.  Water from tissue fluid diffuses into its core, leading to the dissolution of the drug, and resulting in a saturated solution within the polymer envelope. Drug in solution then diffuses out of the envelope based on the concentration difference between inside and outside. As the inside concentration remains saturated until virtually all of the drug is dissolved, and as the outside conditions are “sink,” the chemical potential which drives drug release is constant over the entire delivery period. This leads to pseudo-zero order release.

Briefly, API in powdered form is compressed into a "pill" using conventional tableting procedures. The pill is then coated with a semipermeable polymer or polymers forming a "pod" (Fig. 1a).  The pod is then placed into a receptacle in a "blank" ring which includes a drug delivery window. The delivery rate is controlled by modifying the permeability characteristics of the coating polymer, and the size of the delivery window.

Fig 1a. Cross-section view of a polymer-coated drug pod (red = polymer; grey = drug core)

Fig 1b. Cross-section view of an IVR with a drug pod in place. (green =  outer IVR structure made of silicone elastomer; blue = silicone elastomer for backfilling)

Fig 1c. Schematic showing the IVR assembly process.

The A--> B -->C ---> D process shows how the pods are placed in IVR cavities and back-filled with an elastomer using silicone adhesive.

Fig 1d. Photograph of an IVR.

Picture of the finished four-pod-ivr.