A trend towards resorbable microspheres

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Jafar Golzarian, a professor of interventional radiology, University of Minnesota, Minneapolis, USA, founded EmboMedics in 2012 and serves as its chief medical officer. He tells Interventional News about the factors driving an interest in resorbable embolics.

What advantages does “resorbability”, the ability to create a temporary occlusion and then dissolve, confer to an embolic agent? In which clinical situations is this of most value?

There is a trend towards using resorbable and “organic” materials, both by patients and regulatory instances. The first objective and goal of resorbable materials is that the embolic material should be removed from the body after the desired clinical effect is obtained. Materials left permanently within the body may be subject to long-term reaction from our immune system. Synthetic materials may also cause foreign body reaction unless eliminated very early. These can provoke some issues with clearance from the kidney.

Another advantage with resorbable embolics is that they should ideally allow for the revascularisation and opening of occluded vessels; this may allow additional treatment in situations such as liver tumours.

Resorbable materials have been successfully used in many indications but the more obvious clinical situations are uterine fibroid embolization, trauma and conventional transarterial chemoembolization (TACE).

What are the key characteristics of EmboMedic’s resorbable spheres?

The embolic materials currently being developed by EmboMedics are called ResoSpheres. They are available in similar size ranges as other commercial particles from 40 to 1200µm. These particles are made of natural polymers and are therefore resorbable, totally organic and biocompatible. Embomedics is working on two different resorbable microspheres.

One of the current difficulties with non-resorbable embolic agents is that they remain in the arteries permanently and can cause inflammatory and immune responses. How long are resorbable microspheres designed to provide an occlusion and how long do they take to breakdown?

This is an excellent point. This biocompatible material can have different resorption time based on the strength of the cross linking. The particles are designed for 14 to 21 days resorption. A paper recently published in the Journal of Vascular and Interventional Radiology (JVIR) shows that the beads start to breakdown within the first week and that the vessels are open at 21 days.

What are the key in vitro and in vivo findings from the early research involving these resorbable microspheres?

These findings show that the beads are injectable, compressible and easy to use. The resorption time is predictable and not only is the material resorbed, but the vessel also recanalises after resorption.

What drugs are currently able to be loaded onto these resorbable microspheres?

There are two resorbable materials. The first one is designed to be used as a bland embolic. However, the second material that is under development is resorbable and loadable; these beads can load a series of drugs with successful loading and release, including doxorubicin, ibuprofen, sunitinib, tetracycline and others.

Are there particular types of embolization that require a more permanent occlusion? In which embolization procedures would you not use resorbable microspheres?

There are some indications such as bronchial artery embolization, visceral aneurysms or arteriovenous malformations for which permanent occlusion is required. However, in the majority of embolization cases as demonstrated by the extensive use.