The Terumo Neuro Arsenal Medical deal gives Terumo’s neurovascular business a new liquid embolic. Terumo Neuro said on September 29, 2026 that it has signed an agreement to acquire Arsenal Medical, a privately held, clinical-stage biomaterials company developing NeoCast, an investigational liquid embolic for chronic subdural hematoma (cSDH). Financial terms were not disclosed, and the proposed transaction is subject to customary closing conditions, according to the company announcement.
Upon completion, the acquisition would expand Terumo Neuro’s liquid embolic portfolio and advance its strategy of bringing differentiated neurovascular technologies to physicians and patients.
Key Takeaways: Terumo Neuro Arsenal Medical Deal
- Terumo Neuro signed an agreement to acquire Arsenal Medical. Terms were not disclosed, and closing is subject to customary conditions.
- Arsenal’s NeoCast is an investigational, solvent-free, non-adhesive liquid embolic designed for controlled delivery and predictable distal penetration. It is not approved for commercial sale in the United States.
- NeoCast has first-in-human data in cSDH and an FDA-approved investigational device exemption for the pivotal RADIANT study, where the first patients have been enrolled.
- If approved, NeoCast would compete with established liquid embolic platforms from Medtronic and Johnson & Johnson, MassDevice reported.
What Is NeoCast?
NeoCast is an investigational next-generation liquid embolic biomaterial from Arsenal Medical that is delivered through a catheter to block small vessels such as the middle meningeal artery (MMA). It is described as shear-responsive, solvent-free and non-adhesive, with controlled delivery and predictable distal penetration, and it is being developed for chronic and subacute subdural hematoma.
What Is Chronic Subdural Hematoma?
A chronic subdural hematoma is a collection of blood between the membranes that surround the brain. The term chronic refers to a clinical onset about three weeks or more after the presumed causing event. The condition is typically caused by minor head trauma and is more common among older adults and people taking blood thinners, MassDevice reported. Surgical drainage remains a common treatment, but recurrence after surgery is a continuing clinical challenge, according to MD+DI.
Terumo Neuro Arsenal Medical Deal at a Glance
| Detail | Information |
|---|---|
| Acquirer | Terumo Neuro (formerly MicroVention), part of Terumo Corporation |
| Target | Arsenal Medical Inc., Waltham, Massachusetts |
| Technology | NeoCast, an investigational liquid embolic for chronic subdural hematoma |
| Announced | September 29, 2026 |
| Financial terms | Not disclosed |
| Status | Proposed transaction, subject to customary closing conditions |
| Clinical status | First-in-human data; FDA-approved IDE for the pivotal RADIANT study, with first patients enrolled |
| Regulatory status | Investigational; not approved for commercial sale in the United States |
Why Liquid Embolics Matter for Subdural Hematoma
Liquid embolics are injectable materials delivered through a microcatheter that lodge or solidify inside a vessel to block blood flow. In subdural hematoma, physicians can use them to embolize the middle meningeal artery, which supplies the membrane around the blood collection, with the aim of reducing recurrence without repeat surgery. The approach is still emerging, and published pilot studies note that the choice of embolic agent remains an open question, which is the gap NeoCast is designed to address.
What the Terumo Neuro Arsenal Medical Deal Means
Terumo Neuro CEO Carsten Schroeder called NeoCast a compelling opportunity that could be a game-changing innovation for cSDH, saying that as MMA embolization emerges as an important new treatment option, a purpose-developed liquid embolic could make a meaningful impact for physicians and patients. Arsenal CEO Upma Sharma said the company was founded on the idea that advanced materials can transform how challenging conditions are treated, and that NeoCast was designed to deliver controlled placement and consistent distal penetration without solvents or adhesives.
Terumo Neuro was founded in 1997 as MicroVention and acquired by Terumo Corporation in 2006. Its portfolio covers treatments for cerebral aneurysms, ischemic stroke, carotid artery disease and neurovascular malformations. Adding a liquid embolic aimed at subdural hematoma would extend that range into a newer area of neurointervention.
Clinical Evidence So Far
In the EMBO-02 first-in-human study, NeoCast produced what NeuroNews described as substantial cSDH resolution and functional outcome gains in final results. MD+DI reported that 79% of the 24 patients were treated with embolization alone, and 10 were treated without general anesthesia.
Arsenal has since received FDA investigational device exemption approval for RADIANT, a pivotal, randomized, multicenter study evaluating NeoCast adjunctively with surgery for symptomatic subacute and chronic subdural hematoma. MassDevice reports that the study compares NeoCast with Medtronic’s Onyx liquid embolic system. In our assessment, small first-in-human data cannot show that NeoCast is better than existing options, so RADIANT will be the key test.
What Comes Next for the Terumo Neuro Arsenal Medical Deal
The companies did not give a closing date or a timeline for U.S. approval. After the transaction closes, Terumo Neuro says it will combine its global neurovascular expertise with Arsenal’s technology platform. Until then, NeoCast remains an investigational device that cannot be sold in the United States.
For related coverage, read our reports on the blood clot retrieval devices market, the neurotech devices market and the Neuralink brain chip implant, or browse our medical devices news section.
Frequently Asked Questions About the Terumo Neuro Arsenal Medical Deal
What is Terumo Neuro acquiring?
Terumo Neuro is acquiring Arsenal Medical, a privately held, clinical-stage biomaterials company in Waltham, Massachusetts that is developing the NeoCast liquid embolic for chronic subdural hematoma.
How much is Terumo Neuro paying for Arsenal Medical?
The financial terms were not disclosed.
What does NeoCast treat?
NeoCast is investigational and is being developed for chronic and subacute subdural hematoma through embolization of the middle meningeal artery.
Is NeoCast approved?
No. NeoCast is an investigational device and is not approved for commercial sale in the United States. It is being studied in the pivotal RADIANT trial.
When will the deal close?
No closing date was given. The proposed transaction is subject to customary closing conditions.
This report is based on company announcements and trade-press coverage, and was last updated on October 1, 2026. It is for information only and is not medical or investment advice.
