An Easy, Predictable, and Simpler Way to Embolize Tumors
Bedford, MA -- Instylla is now enrolling patients in a clinical trial for the world’s first hydrogel-based liquid embolic intended for the treatment of hypervascular tumors. A second initial application for its Embrace embolic therapy is hemorrhage control, where the product offers advantages in terms of simplicity, speed, and safety.
Amar Sawhney and his teams, it seems, can make medical hydrogels do anything they want them to. The products of four hydrogel companies Sawhney founded with his partner Fred Khosravi (within their accelerator Incept LLC), have treated more than five million patients across the ophthalmic, surgical, interventional cardiology, and prostate cancer specialties.
Sawhney founded Confluent Surgical in 1998, which, after proving out a hydrogel platform for surgical sealants and post-surgical anti-adhesion products, was acquired by Covidien in 2006 (then known as Tyco Healthcare; in 2013, the Confluent products were sold to Integra LifeSciences). AccessClosure Inc. (acquired by Cardinal Health in 2014) was founded to address the problem of arterial puncture site closure after interventional procedures. Next came Ocular Therapeutix Inc., to develop an absorbable punctal plug for the extended delivery of drugs to the surface of the eye. Augmenix Inc., now part of Boston Scientific Corp. (which purchased the start-up in in 2018), created a hydrogel-based product that reduces some of the debilitating side effects of prostate radiation therapy.
Sawhney’s newest hydrogel company, Instylla Inc., founded in 2017, is addressing interventional oncology with a hydrogel-based liquid for tumor embolization, a therapy that shrinks tumors by blocking their blood supply. Instylla also has a side gig in hemorrhage control, a second early market for its technology.
Sawhney notes that as far back as the early days of Confluent Surgical, he had contemplated peripheral arterial embolization for the treatment of tumors, but at the time, decided against it. The field was then at an early stage of development and reimbursement for basic embolization beads was insufficient to justify the expensive clinical trials required for a new biomaterial-based solution. That’s not the case today. “There are existing codes that provide adequate reimbursement, and that makes this attractive from the standpoint of commercial adoption,” he says.
Standing Out in a Crowded Field
Of course, some 17 years later, the field of tumor embolization has become crowded with a variety of products— bland or drug-eluting beads, radioactive glass beads, and coils from such hefty competitors as Boston Scientific, Terumo Interventional Systems, and Cook Medical, in addition to Penumbra Inc., Sirtex Medical Ltd., and Balt, as well as start-ups entering the field.
Facing a high hurdle for differentiation and with the benefit of being able to learn from the extensive experience of the interventional radiologists that perform arterial embolization procedures, Sawhney and his team decided to begin with a wish list for the ideal solution. That exercise resulted in the Embrace Hydrogel Embolic System (HES). Embrace HES is the first liquid embolic hydrogel for peripheral arterial embolization of hypervascular tumors, which often occur in the liver, kidney, and bone. As noted, hemorrhage control is an additional early application.
Although competitors abound, Sawhney says “We found that the world still lacked a good liquid embolic for peripheral vascular applications.” Two types of liquid embolics approved for neurovascular applications are used off label in other parts of the body; Medtronic plc’s Onyx, an ethylene vinyl-alcohol copolymer embolic containing a solvent called dimethyl sulfoxide, and a class of “Super-Glue” products (of the cyanoacrylate family). None of those liquid embolics have approval to be left behind in the body or for peripheral vascular use and on occasion, operators using them have inadvertently glued the tip of the delivery catheter to the inside of the tumor, which can be a harmful outcome.
Permanent implants like beads and coils have their drawbacks too, in terms of the need to size the devices and the doses to the target anatomy, and the risk that they’ll migrate and embolize in unintended locations.
The laundry list the founding team put together was detailed: a water-based product that could penetrate the deepest part of the tumor vasculature, fill the vessels, and quickly and completely stop blood flow regardless of the patient’s coagulation status; avoid CT or MR imaging artifact; absorb over time; and, if it were to flow in an unintended direction, remain harmless, all within an aqueous environment. In other words, a seemingly contradictory combination of requirements: the same material can set up in water, absorb in water, and be rendered inactive in water, which is all achievable because of Sawhney and his team’s expertise in hydrogels.
Embrace HES, the main components of which are water and polyethylene glycol, is dilution sensitive. It doesn’t solidify unless there is a sufficient concentration at one location, so if a small amount escapes into circulation, it won’t set up. Because it is an aqueous hydrogel it can also carry drugs or combinations of drugs. “None of the other liquid embolics are capable of carrying drugs, and drug-eluting beads are also limited because they have a particular charge that limits them to complexing with only certain types of drugs,” Sawhney explains.
Instylla’s product might also offer advantages in terms of procedural speed and efficiency, especially in hemorrhage control. The Embrace embolic procedure can be completed in minutes, while procedures using beads can take almost an hour, for reasons that Sawhney enumerates.
When embolizing tumors
interventionalists might start with small beads (e.g., 200 microns in diameter) while viewing angiography to see if the blood flow is slowing down. They’ll often subsequently switch to larger beads to fill the vessel (600-700 microns). “You have to open several vials and suspend the beads because they tend to settle, and you have to keep moving the syringes back and forth to make sure they don’t,” Sawhney says. Since the operator can’t see exactly where the beads are going, “You pump out several syringes and observe where the flow is restricted. If it’s not, you need to keep repeating the steps.” Operators might need to insert seven or eight syringes full of beads to embolize a particular tumor, he says. “There will be many exchanges of syringes, resuspensions, and additional flushes. It can become a 40-minute procedure.”
Embrace HES, which is radiopaque due to added contrast media, is delivered from a coaxial dual lumen system—a microcatheter inside another microcatheter. A delivery kit containing two syringes with different solutions is attached to the back end of the dual lumen system. These solutions are injected simultaneously through the microcatheters, enabling formation of the hydrogel. The operator delivers a puff and can watch it enter the tumor because it is radiopaque. They’ll continue with a few more puffs until blood flow stops and the procedure is complete. “The whole procedure takes a couple of minutes. You don’t have to create a suspension of the beads, you don’t need to do any syringe exchanges, you don’t have to stock devices of varied sizes in inventory.” The embolization procedure becomes simpler, potentially shorter and more reproducible,” he says.
The hydrogel embolic absorbs in approximately six months and gradual cellular ingrowth occurs, preventing embolized vessels from reopening. “Since the hydrogel is more than 90% water, absorption is very reproducible,” Sawhney says.
Instylla began first-in-human studies in Australia just prior to the start of the pandemic, which, naturally, slowed down recruitment. An analysis of eight patients showed that all procedures were technically successful, and that hypervascular tumors (some benign, some malignant) were embolized, as confirmed by imaging at 30 days.