Obsidio Inc., a medical device company based in Columbia, South Carolina, has developed an embolic hydrogel (called a gel embolic material: GEM) designed to be delivered minimally invasively through a clinical catheter for blood vessel occlusion. Applications include controlling blood flow in vascular injuries and aneurysms, reducing tumor blood supply, and preventing abnormal blood flow between arteries and veins, such as arteriovenous malformations.
Currently, the gold standard treatment in terms of transcatheter embolization involves delivering multiple metal coils into a blood vessel, which works by promoting coagulation so that the clot around the coil stops the flow of blood. However, this approach has numerous limitations, as it is not always suitable for patients with impaired coagulation, and can sometimes fail, resulting in rebleeding.
To address this, Obsidio has developed a hydrogel material that can occlude a target vessel and which does not rely on a patient’s own coagulation ability. The material can be delivered using a catheter, and demonstrates shear thinning properties, whereby it acts as a semisolid when subjected to shear stress. This allows it to flow through a catheter during delivery but it forms a soft solid once in the blood vessel, allowing for minimally invasive embolization.
Through its substantial cohesive properties, the material is not easily dislodged and does not break up in the vessel. In fact, it fills the targeted vessel, forming a “cast” of the vessel interior to immediately stop blood flow.
Medgadget had the opportunity to ask Dr. Rahmi Oklu, Founder and Chief Medical Officer of Obsidio some questions about the technology.
Conn Hastings, Medgadget: Please give us an overview of the indications for transcatheter intravascular embolization.
Dr. Oklu, Obsidio: Our goal is to disrupt the coil embolization industry. Wherever you would use a coil, GEM can be used; for example, treatment of saccular aneurysms, gastrointestinal bleeding, trauma bleeding and gonadal vein embolization in pelvic congestion syndrome or in varicocele. We are also branching out to indications that would include embolization of vascular malformations, tumor embolization, prostate artery embolization for benign prostatic hyperplasia (BPH), and varicose vein embolization. Just to illustrate the ease of use of GEM, in an office setting, in minutes you can inject GEM under ultrasound guidance to the great saphenous vein to treat varicose veins.
Medgadget: What are the limitations of current treatment approaches?
Dr. Oklu: There are numerous limitations; I’m not sure where to begin! Coils come in all sorts of lengths, diameters and shapes; some are pushable, retractable, and require special catheters and individual coil releasing devices. If you look in an angiography room, shelf after shelf is filled with costly coils and catheters. This increases the cost burden for the hospital, for the patient, and the healthcare system. These coils also create an artifact when they are imaged; so you go through all this trouble, spend many thousands of dollars on coils and spend several hours doing the procedure exposing yourself and the patient to radiation and at the end you can’t even use an ultrasound, CT or MRI to see whether coiling worked. Doctors want to know if the coils were able to stop the bleeding by imaging. Often we look for clinical signs instead; did the blood pressure normalize, or is the heart rate back to normal, does the patient require blood transfusions? This is frustrating for the physician and a disservice to our patients. The most critical limitation of current technology is that they are ineffective in coagulopathic patients. This is, in fact, the motivation for developing GEM; a patient that I embolized passed away because the coils were not effective in stopping the bleeding. This patient was the inspiration to push us to come up with a better alternative to coil embolization. Coils today rely on the body’s ability to form a clot around the coil to stop bleeding. Another significant limitation is the time it takes to deploy a coil. Some cases may require dozens of coils; large pseudoaneurysms, portal vein embolization cases, bowel or stomach varix embolization, gonadal vein embolization. These take time to deploy, increase costs and at the end may not work.
Medgadget: How does the hydrogel embolic agent developed by Obsidio circumvent these limitations?
Dr. Oklu: Every time I do an embolization procedure, I wish that I could use GEM. Recently, I had to rush to the hospital to treat a patient with a ruptured aneurysm; the patient was vomiting up blood while on a massive transfusion protocol. I placed over 580 cm of fibered coil as fast as I could in an hour, and at the end the blood continued to go through the coils. I stopped the procedure because I just could not place any more coils, not knowing whether we helped the patient or not. With GEM, however, you would simply connect to the catheter, any catheter, and simply inject the gel. We would have finished in under a minute knowing at the end that the bleeding had stopped. The gel would simply fill the aneurysm space to create an impenetrable cast. GEM would replace the massive coil/catheter inventory in the angiography suite reducing costs to the hospital. GEM would also reduce procedure time, reduce radiation exposure, and significantly improve efficacy. One of the most essential features of GEM is that it produces no artifact; this means that for the first time you can do a CT scan or MRI to see whether the embolization worked or deliver the GEM under ultrasound guidance.
Medgadget: Is the gel intended to permanently block the target vessel? What happens to the treated vessel and gel bolus over time?
Dr. Oklu: GEM will block the vessel permanently. Because it is biocompatible, it elicits an immune reaction to the biomaterial and immune cells then biodegrade the GEM and replace it with fibrotic tissue.
Medgadget: What is the gel made of? How did you develop a material which can easily flow through a catheter, but which can form a robust bolus in situ?
Dr. Oklu: The gel consists of gelatin and nanosilicates; when pressure is applied, the gel becomes semi-solid and begins to flow, for example through the catheter. When the pressure inside the catheter stops, the gel adopts a solid state.
Medgadget: Is the gel easy to prepare and use during transcatheter procedures?
Dr. Oklu: In its pure form, the gel is easy to make; it takes a few hours. The quality assurance step is lengthy in our laboratory since we are testing it in large animals. The GEM we make has to have a certain injectable pressure using a clinical catheter, the rheological properties have to be consistent and we do a sterility test. In the future, the complexity of the gel could change as we use it as a carrier to deliver therapeutics.
Link: Obsidio homepage…
